using System;
using System.Collections.Generic;
using System.Data.Common;
using System.IO;
using System.Reflection;

namespace MsgLibReadSidecar
{
    internal static class Program
    {
        private const string Version = "0.4.0";
        private const string DefaultPassword = "123";

        private static readonly HashSet<string> DefaultTargetTables = new HashSet<string>(StringComparer.OrdinalIgnoreCase)
        {
            "TD_Roster", "TD_CustomEffigy", "tblRecent", "tblChatLevel", "tblPersonMsg", "tblMsgGroupPersonMsg",
            "TD_WorkGroupAuth", "TD_ReceiveFileRecord", "TD_SendFileRecord", "TD_SystemMessageRecord", "TD_MsgReadBurn"
        };

        [STAThread]
        private static int Main(string[] args)
        {
            string requestText = Console.In.ReadToEnd();
            Dictionary<string, object> request;
            string requestId = "";
            string op = "";

            if (!SidecarProtocol.TryParseRequest(requestText, out request, out requestId, out op))
            {
                Console.WriteLine(SidecarProtocol.ToJson(SidecarProtocol.Failure(requestId, op, "INVALID_REQUEST", "request must be a valid isphere.msglib.v1 JSON object")));
                return 0;
            }

            try
            {
                Dictionary<string, object> opArgs = SidecarProtocol.GetObject(request, "args");
                Dictionary<string, object> response;
                switch (op)
                {
                    case "self_check":
                        response = SidecarProtocol.Success(requestId, op, SelfCheckData());
                        break;
                    case "schema_summary":
                        response = SidecarProtocol.Success(requestId, op, SchemaSummary(opArgs, false));
                        break;
                    case "display_sources":
                        response = SidecarProtocol.Success(requestId, op, SchemaSummary(opArgs, true));
                        break;
                    case "message_sources":
                        response = SidecarProtocol.Success(requestId, op, MessageSources(opArgs));
                        break;
                    case "list_messages":
                        response = SidecarProtocol.Success(requestId, op, ListMessages(opArgs));
                        break;
                    case "display_entities":
                        response = SidecarProtocol.Success(requestId, op, DisplayEntities(opArgs));
                        break;
                    default:
                        response = SidecarProtocol.Failure(requestId, op, "UNSUPPORTED_OP", "unsupported op: " + op);
                        break;
                }
                Console.WriteLine(SidecarProtocol.ToJson(response));
                return 0;
            }
            catch (Exception ex)
            {
                Console.Error.WriteLine(ex.ToString());
                Console.WriteLine(SidecarProtocol.ToJson(SidecarProtocol.Failure(requestId, op, "SIDECAR_FAILED", ex.Message)));
                return 0;
            }
        }

        private static Dictionary<string, object> SelfCheckData()
        {
            return new Dictionary<string, object>
            {
                { "sidecar_name", "MsgLibReadSidecar" },
                { "sidecar_version", Version },
                { "protocol", SidecarProtocol.Protocol },
                { "runtime", ".NET Framework " + Environment.Version },
                { "process_bits", IntPtr.Size * 8 },
                { "requires_process_bits", 32 },
                { "read_only", true },
                { "mutates_db", false },
                { "db_mutation_allowed", false },
                { "message_body_reads_allowed", true }
            };
        }

        private static Dictionary<string, object> SchemaSummary(Dictionary<string, object> args, bool displayOnly)
        {
            string sqliteDllPath = SidecarProtocol.GetString(args, "sqlite_dll_path", "");
            string dbPath = SidecarProtocol.GetString(args, "db_path", "");
            string password = SidecarProtocol.GetString(args, "password", DefaultPassword);
            bool includeCounts = SidecarProtocol.GetBool(args, "include_counts", true);
            int maxTables = Clamp(SidecarProtocol.GetInt(args, "max_tables", 128), 1, 256);
            List<string> requestedTargets = SidecarProtocol.GetStringList(args, "target_tables");
            HashSet<string> targetTables = requestedTargets.Count == 0 ? DefaultTargetTables : new HashSet<string>(requestedTargets, StringComparer.OrdinalIgnoreCase);

            ValidateInputs(sqliteDllPath, dbPath);

            var result = new Dictionary<string, object>
            {
                { "metadata_only", true },
                { "read_only", true },
                { "message_body_values_returned", false },
                { "sqlite_dll_path", sqliteDllPath },
                { "db_path", dbPath },
                { "provider", "System.Data.SQLite" },
                { "process_bits", IntPtr.Size * 8 }
            };

            using (DbConnection connection = OpenSqliteConnection(sqliteDllPath, dbPath, password))
            {
                connection.Open();
                TryExecuteNonQuery(connection, "PRAGMA query_only=ON");
                result["sqlite_version"] = ExecuteScalar(connection, "select sqlite_version()");
                List<Dictionary<string, object>> tables = ReadMasterTables(connection, maxTables);
                List<Dictionary<string, object>> columns = ReadColumns(connection, tables, displayOnly ? targetTables : null);
                result["tables"] = tables;
                result["columns"] = columns;
                result["target_row_counts"] = includeCounts ? ReadTargetCounts(connection, tables, targetTables) : new List<Dictionary<string, object>>();
                if (displayOnly)
                {
                    result["display_sources"] = BuildDisplaySources(tables, columns);
                }
            }

            return result;
        }

        private static Dictionary<string, object> MessageSources(Dictionary<string, object> args)
        {
            string sqliteDllPath = SidecarProtocol.GetString(args, "sqlite_dll_path", "");
            string dbPath = SidecarProtocol.GetString(args, "db_path", "");
            string password = SidecarProtocol.GetString(args, "password", DefaultPassword);

            ValidateInputs(sqliteDllPath, dbPath);

            var result = new Dictionary<string, object>
            {
                { "metadata_only", true },
                { "read_only", true },
                { "message_body_values_returned", false },
                { "raw_rows_returned", false },
                { "file_paths_returned", false },
                { "provider", "System.Data.SQLite" },
                { "process_bits", IntPtr.Size * 8 }
            };

            using (DbConnection connection = OpenSqliteConnection(sqliteDllPath, dbPath, password))
            {
                connection.Open();
                TryExecuteNonQuery(connection, "PRAGMA query_only=ON");
                List<Dictionary<string, object>> tables = ReadMasterTables(connection, 256);
                HashSet<string> messageTables = BuildMessageSourceTableSet();
                List<Dictionary<string, object>> columns = ReadColumns(connection, tables, messageTables);
                Dictionary<string, HashSet<string>> columnMap = BuildColumnMap(columns);
                Dictionary<string, string> rowCounts = ReadTargetCountMap(connection, tables, messageTables);
                result["message_sources"] = BuildMessageSources(tables, columnMap, rowCounts);
            }

            return result;
        }

        private static Dictionary<string, object> ListMessages(Dictionary<string, object> args)
        {
            string sqliteDllPath = SidecarProtocol.GetString(args, "sqlite_dll_path", "");
            string dbPath = SidecarProtocol.GetString(args, "db_path", "");
            string password = SidecarProtocol.GetString(args, "password", DefaultPassword);
            string conversationId = SidecarProtocol.GetString(args, "conversation_id", "").Trim();
            string conversationType = SidecarProtocol.GetString(args, "conversation_type", "auto").Trim().ToLowerInvariant();
            string query = SidecarProtocol.GetString(args, "query", "").Trim();
            string since = SidecarProtocol.GetString(args, "since", "").Trim();
            string cursor = SidecarProtocol.GetString(args, "cursor", "").Trim();
            int limit = Clamp(SidecarProtocol.GetInt(args, "limit", 20), 1, 50);
            bool includeBody = SidecarProtocol.GetBool(args, "include_body", false);
            bool includeAttachmentMetadata = SidecarProtocol.GetBool(args, "include_attachment_metadata", false);

            if (!string.IsNullOrWhiteSpace(cursor))
            {
                throw new ArgumentException("list_messages cursor pagination is not available yet");
            }
            if (string.IsNullOrWhiteSpace(conversationType)) conversationType = "auto";
            if (!string.Equals(conversationType, "auto", StringComparison.OrdinalIgnoreCase) &&
                !string.Equals(conversationType, "direct", StringComparison.OrdinalIgnoreCase) &&
                !string.Equals(conversationType, "group", StringComparison.OrdinalIgnoreCase) &&
                !string.Equals(conversationType, "system", StringComparison.OrdinalIgnoreCase))
            {
                throw new ArgumentException("conversation_type must be auto, direct, group, or system");
            }

            ValidateInputs(sqliteDllPath, dbPath);

            var result = new Dictionary<string, object>
            {
                { "metadata_only", !includeBody },
                { "read_only", true },
                { "message_body_values_returned", includeBody },
                { "raw_rows_returned", false },
                { "file_paths_returned", false },
                { "limit", limit },
                { "provider", "System.Data.SQLite" },
                { "process_bits", IntPtr.Size * 8 },
                { "next_cursor", null }
            };

            using (DbConnection connection = OpenSqliteConnection(sqliteDllPath, dbPath, password))
            {
                connection.Open();
                TryExecuteNonQuery(connection, "PRAGMA query_only=ON");
                List<Dictionary<string, object>> tables = ReadMasterTables(connection, 256);
                HashSet<string> listTables = BuildListMessagesTableSet();
                List<Dictionary<string, object>> columns = ReadColumns(connection, tables, listTables);
                Dictionary<string, HashSet<string>> columnMap = BuildColumnMap(columns);
                var sourceTables = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
                var messages = new List<Dictionary<string, object>>();

                if (ShouldReadMessageRole(conversationType, "direct"))
                {
                    ReadDirectMessages(connection, columnMap, conversationId, query, since, limit, includeBody, includeAttachmentMetadata, messages, sourceTables);
                }
                if (ShouldReadMessageRole(conversationType, "group"))
                {
                    ReadGroupMessages(connection, columnMap, conversationId, query, since, limit, includeBody, includeAttachmentMetadata, messages, sourceTables);
                }
                if (ShouldReadMessageRole(conversationType, "system"))
                {
                    ReadSystemMessages(connection, columnMap, conversationId, query, since, limit, includeBody, includeAttachmentMetadata, messages, sourceTables);
                }

                messages.Sort(CompareMessagesDescending);
                while (messages.Count > limit)
                {
                    messages.RemoveAt(messages.Count - 1);
                }
                foreach (Dictionary<string, object> message in messages)
                {
                    message.Remove("sort_key");
                }

                result["source_tables"] = ToSortedArray(sourceTables);
                result["messages"] = messages;
            }

            return result;
        }


        private static Dictionary<string, object> DisplayEntities(Dictionary<string, object> args)
        {
            string sqliteDllPath = SidecarProtocol.GetString(args, "sqlite_dll_path", "");
            string dbPath = SidecarProtocol.GetString(args, "db_path", "");
            string password = SidecarProtocol.GetString(args, "password", DefaultPassword);
            string entityType = SidecarProtocol.GetString(args, "entity_type", "").Trim().ToLowerInvariant();
            string query = SidecarProtocol.GetString(args, "query", "").Trim();
            int limit = Clamp(SidecarProtocol.GetInt(args, "limit", 25), 1, 100);

            if (!string.Equals(entityType, "contacts", StringComparison.OrdinalIgnoreCase) &&
                !string.Equals(entityType, "groups", StringComparison.OrdinalIgnoreCase))
            {
                throw new ArgumentException("entity_type must be contacts or groups");
            }

            ValidateInputs(sqliteDllPath, dbPath);

            var result = new Dictionary<string, object>
            {
                { "metadata_only", true },
                { "read_only", true },
                { "message_body_values_returned", false },
                { "raw_rows_returned", false },
                { "entity_type", entityType },
                { "limit", limit },
                { "provider", "System.Data.SQLite" },
                { "process_bits", IntPtr.Size * 8 }
            };

            using (DbConnection connection = OpenSqliteConnection(sqliteDllPath, dbPath, password))
            {
                connection.Open();
                TryExecuteNonQuery(connection, "PRAGMA query_only=ON");
                List<Dictionary<string, object>> tables = ReadMasterTables(connection, 256);
                HashSet<string> entityTables = BuildDisplayEntityTableSet(entityType);
                List<Dictionary<string, object>> columns = ReadColumns(connection, tables, entityTables);
                Dictionary<string, HashSet<string>> columnMap = BuildColumnMap(columns);
                List<Dictionary<string, object>> entities = ReadDisplayEntities(connection, entityType, query, limit, columnMap);
                result["entities"] = entities;
                result["result_count"] = entities.Count;
            }

            return result;
        }

        private static void ValidateInputs(string sqliteDllPath, string dbPath)
        {
            if (string.IsNullOrWhiteSpace(sqliteDllPath) || !File.Exists(sqliteDllPath))
            {
                throw new ArgumentException("sqlite_dll_path must point to an existing System.Data.SQLite.dll");
            }
            if (string.IsNullOrWhiteSpace(dbPath) || !File.Exists(dbPath))
            {
                throw new ArgumentException("db_path must point to an existing copied MsgLib.db");
            }
            if (!string.Equals(Path.GetFileName(dbPath), "MsgLib.db", StringComparison.OrdinalIgnoreCase))
            {
                throw new ArgumentException("db_path must point to a copied MsgLib.db file");
            }
        }

        private static DbConnection OpenSqliteConnection(string sqliteDllPath, string dbPath, string password)
        {
            Assembly assembly = Assembly.LoadFrom(sqliteDllPath);
            Type builderType = assembly.GetType("System.Data.SQLite.SQLiteConnectionStringBuilder", true);
            object builder = Activator.CreateInstance(builderType);
            SetPropertyIfExists(builderType, builder, "DataSource", dbPath);
            SetPropertyIfExists(builderType, builder, "Password", password);
            SetPropertyIfExists(builderType, builder, "ReadOnly", true);
            SetPropertyIfExists(builderType, builder, "Pooling", false);
            SetPropertyIfExists(builderType, builder, "FailIfMissing", true);
            string connectionString = Convert.ToString(builderType.GetProperty("ConnectionString").GetValue(builder, null));
            Type connectionType = assembly.GetType("System.Data.SQLite.SQLiteConnection", true);
            object connection = Activator.CreateInstance(connectionType, new object[] { connectionString });
            DbConnection dbConnection = connection as DbConnection;
            if (dbConnection == null)
            {
                throw new InvalidOperationException("SQLiteConnection is not a DbConnection");
            }
            return dbConnection;
        }

        private static void SetPropertyIfExists(Type type, object target, string name, object value)
        {
            PropertyInfo property = type.GetProperty(name);
            if (property != null && property.CanWrite)
            {
                property.SetValue(target, value, null);
            }
        }

        private static List<Dictionary<string, object>> ReadMasterTables(DbConnection connection, int maxTables)
        {
            var rows = new List<Dictionary<string, object>>();
            using (DbCommand command = connection.CreateCommand())
            {
                command.CommandText = "select type, name, tbl_name from sqlite_master where type in ('table','view') order by type, name";
                using (DbDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read() && rows.Count < maxTables)
                    {
                        rows.Add(new Dictionary<string, object>
                        {
                            { "type", Convert.ToString(reader["type"]) },
                            { "name", Convert.ToString(reader["name"]) },
                            { "tbl_name", Convert.ToString(reader["tbl_name"]) }
                        });
                    }
                }
            }
            return rows;
        }

        private static List<Dictionary<string, object>> ReadColumns(DbConnection connection, List<Dictionary<string, object>> tables, HashSet<string> onlyTables)
        {
            var rows = new List<Dictionary<string, object>>();
            foreach (Dictionary<string, object> table in tables)
            {
                string tableName = Convert.ToString(table["name"]);
                string tableType = Convert.ToString(table["type"]);
                if (!string.Equals(tableType, "table", StringComparison.OrdinalIgnoreCase)) continue;
                if (onlyTables != null && !onlyTables.Contains(tableName)) continue;

                using (DbCommand command = connection.CreateCommand())
                {
                    command.CommandText = "PRAGMA table_info(" + QuoteIdent(tableName) + ")";
                    using (DbDataReader reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            rows.Add(new Dictionary<string, object>
                            {
                                { "table", tableName },
                                { "cid", Convert.ToString(reader["cid"]) },
                                { "name", Convert.ToString(reader["name"]) },
                                { "type", Convert.ToString(reader["type"]) },
                                { "notnull", Convert.ToString(reader["notnull"]) },
                                { "pk", Convert.ToString(reader["pk"]) }
                            });
                        }
                    }
                }
            }
            return rows;
        }

        private static List<Dictionary<string, object>> ReadTargetCounts(DbConnection connection, List<Dictionary<string, object>> tables, HashSet<string> targetTables)
        {
            var rows = new List<Dictionary<string, object>>();
            foreach (Dictionary<string, object> table in tables)
            {
                string tableName = Convert.ToString(table["name"]);
                string tableType = Convert.ToString(table["type"]);
                if (!string.Equals(tableType, "table", StringComparison.OrdinalIgnoreCase)) continue;
                if (!targetTables.Contains(tableName)) continue;
                rows.Add(new Dictionary<string, object>
                {
                    { "table", tableName },
                    { "row_count", ExecuteScalar(connection, "select count(*) from " + QuoteIdent(tableName)) }
                });
            }
            return rows;
        }

        private static Dictionary<string, string> ReadTargetCountMap(DbConnection connection, List<Dictionary<string, object>> tables, HashSet<string> targetTables)
        {
            var rowCounts = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
            foreach (Dictionary<string, object> item in ReadTargetCounts(connection, tables, targetTables))
            {
                rowCounts[Convert.ToString(item["table"])] = Convert.ToString(item["row_count"]);
            }
            return rowCounts;
        }

        private static List<Dictionary<string, object>> BuildDisplaySources(List<Dictionary<string, object>> tables, List<Dictionary<string, object>> columns)
        {
            var tableSet = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (Dictionary<string, object> table in tables)
            {
                if (string.Equals(Convert.ToString(table["type"]), "table", StringComparison.OrdinalIgnoreCase))
                {
                    tableSet.Add(Convert.ToString(table["name"]));
                }
            }

            var columnMap = new Dictionary<string, HashSet<string>>(StringComparer.OrdinalIgnoreCase);
            foreach (Dictionary<string, object> column in columns)
            {
                string table = Convert.ToString(column["table"]);
                string name = Convert.ToString(column["name"]);
                if (!columnMap.ContainsKey(table)) columnMap[table] = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
                columnMap[table].Add(name);
            }

            var sources = new List<Dictionary<string, object>>();
            AddSource(sources, tableSet, columnMap, "contacts_roster", "TD_Roster", new string[] { "JId", "Nick", "GroupName" });
            AddSource(sources, tableSet, columnMap, "contacts_effigy", "TD_CustomEffigy", new string[] { "PersonJid", "PersonName" });
            AddSource(sources, tableSet, columnMap, "recent_display", "tblRecent", new string[] { "PersonId", "PersonName", "FType" });
            AddSource(sources, tableSet, columnMap, "person_message_names", "tblPersonMsg", new string[] { "SndPerson", "SndPersonId", "RecvPerson", "RecvPersonId", "ObjPerson", "ObjPersonId" });
            AddSource(sources, tableSet, columnMap, "group_message_names", "tblMsgGroupPersonMsg", new string[] { "MsgGroupId", "MsgGroupName", "SessionPersonId", "SessionPersonName", "GroupType" });
            AddSource(sources, tableSet, columnMap, "work_group_auth", "TD_WorkGroupAuth", new string[] { "GroupJID", "GroupName", "ChildGroupJid" });
            AddSource(sources, tableSet, columnMap, "received_file_metadata", "TD_ReceiveFileRecord", new string[] { "FileName", "SendPersonJid", "SendPersonName" });
            AddSource(sources, tableSet, columnMap, "sent_file_metadata", "TD_SendFileRecord", new string[] { "FileName", "ReceivePersonJid", "ReceivePersonName" });
            return sources;
        }

        private sealed class MessageSourceSpec
        {
            public string Source;
            public string Table;
            public string Role;
            public string[] RequiredColumns;
        }

        private static HashSet<string> BuildMessageSourceTableSet()
        {
            var tables = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (MessageSourceSpec spec in BuildMessageSourceSpecs())
            {
                tables.Add(spec.Table);
            }
            return tables;
        }

        private static List<MessageSourceSpec> BuildMessageSourceSpecs()
        {
            return new List<MessageSourceSpec>
            {
                new MessageSourceSpec
                {
                    Source = "direct_messages",
                    Table = "tblPersonMsg",
                    Role = "direct",
                    RequiredColumns = new string[] { "Id", "SndPersonId", "RecvPersonId", "ObjPersonId", "ActionTime", "MsgText", "MessageBody" }
                },
                new MessageSourceSpec
                {
                    Source = "group_messages",
                    Table = "tblMsgGroupPersonMsg",
                    Role = "group",
                    RequiredColumns = new string[] { "Id", "SndPersonId", "MsgGroupId", "MsgGroupName", "MsgTime", "MsgText", "MessageBody" }
                },
                new MessageSourceSpec
                {
                    Source = "system_messages",
                    Table = "TD_SystemMessageRecord",
                    Role = "system",
                    RequiredColumns = new string[] { "MsgGuid", "MsgType", "MsgTitle", "MsgText", "SendPersonJid", "MsgTime", "MsgReadState" }
                },
                new MessageSourceSpec
                {
                    Source = "group_receipts",
                    Table = "TD_GroupReceiptMessage",
                    Role = "receipt_metadata",
                    RequiredColumns = new string[] { "MsgGuid", "PersonID", "ReceiptTime" }
                },
                new MessageSourceSpec
                {
                    Source = "received_file_metadata",
                    Table = "TD_ReceiveFileRecord",
                    Role = "attachment_metadata",
                    RequiredColumns = new string[] { "ReceiveMsgGuid", "FileName", "FileSize", "SourceID", "SourceName", "FileType", "SendPersonJid", "SendPersonName", "SendTime" }
                },
                new MessageSourceSpec
                {
                    Source = "recent_conversation_index",
                    Table = "tblRecent",
                    Role = "conversation_index",
                    RequiredColumns = new string[] { "Id", "PersonId", "PersonName", "ActionTime", "FType" }
                }
            };
        }

        private static List<Dictionary<string, object>> BuildMessageSources(List<Dictionary<string, object>> tables, Dictionary<string, HashSet<string>> columnMap, Dictionary<string, string> rowCounts)
        {
            var tableSet = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (Dictionary<string, object> table in tables)
            {
                if (string.Equals(Convert.ToString(table["type"]), "table", StringComparison.OrdinalIgnoreCase))
                {
                    tableSet.Add(Convert.ToString(table["name"]));
                }
            }

            var sources = new List<Dictionary<string, object>>();
            foreach (MessageSourceSpec spec in BuildMessageSourceSpecs())
            {
                AddMessageSource(sources, tableSet, columnMap, rowCounts, spec);
            }
            return sources;
        }

        private static void AddMessageSource(List<Dictionary<string, object>> sources, HashSet<string> tableSet, Dictionary<string, HashSet<string>> columnMap, Dictionary<string, string> rowCounts, MessageSourceSpec spec)
        {
            var presentColumns = new List<string>();
            if (columnMap.ContainsKey(spec.Table))
            {
                foreach (string column in spec.RequiredColumns)
                {
                    if (columnMap[spec.Table].Contains(column)) presentColumns.Add(column);
                }
            }
            string rowCount = rowCounts.ContainsKey(spec.Table) ? rowCounts[spec.Table] : "0";
            sources.Add(new Dictionary<string, object>
            {
                { "source", spec.Source },
                { "table", spec.Table },
                { "role", spec.Role },
                { "available", tableSet.Contains(spec.Table) && presentColumns.Count == spec.RequiredColumns.Length },
                { "required_columns", spec.RequiredColumns },
                { "present_columns", presentColumns.ToArray() },
                { "row_count", rowCount }
            });
        }

        private static HashSet<string> BuildListMessagesTableSet()
        {
            return new HashSet<string>(StringComparer.OrdinalIgnoreCase)
            {
                "tblPersonMsg",
                "tblMsgGroupPersonMsg",
                "TD_SystemMessageRecord",
                "TD_ReceiveFileRecord"
            };
        }

        private static bool ShouldReadMessageRole(string requested, string role)
        {
            return string.Equals(requested, "auto", StringComparison.OrdinalIgnoreCase) ||
                string.Equals(requested, role, StringComparison.OrdinalIgnoreCase);
        }

        private static void ReadDirectMessages(
            DbConnection connection,
            Dictionary<string, HashSet<string>> columnMap,
            string conversationId,
            string query,
            string since,
            int limit,
            bool includeBody,
            bool includeAttachmentMetadata,
            List<Dictionary<string, object>> messages,
            HashSet<string> sourceTables)
        {
            const string table = "tblPersonMsg";
            if (!HasColumns(columnMap, table, new string[] { "Id" })) return;

            string senderIdColumn = FirstExistingColumn(columnMap, table, new string[] { "SndPersonId", "SenderId" });
            string senderNameColumn = FirstExistingColumn(columnMap, table, new string[] { "SndPerson", "SenderName" });
            string receiverIdColumn = FirstExistingColumn(columnMap, table, new string[] { "RecvPersonId", "ReceiverId" });
            string receiverNameColumn = FirstExistingColumn(columnMap, table, new string[] { "RecvPerson", "ReceiverName" });
            string objectIdColumn = FirstExistingColumn(columnMap, table, new string[] { "ObjPersonId", "PersonId" });
            string objectNameColumn = FirstExistingColumn(columnMap, table, new string[] { "ObjPerson", "PersonName" });
            string timeColumn = FirstExistingColumn(columnMap, table, new string[] { "ActionTime", "MsgTime", "CreateTime", "SendTime" });
            string readColumn = FirstExistingColumn(columnMap, table, new string[] { "IsRead", "ReadState", "MsgReadState" });

            using (DbCommand command = connection.CreateCommand())
            {
                var where = new List<string>();
                where.Add("coalesce(" + QuoteIdent("Id") + ", '') <> ''");
                AddListMessageWhere(command, where, table, columnMap, conversationId, query, since, timeColumn,
                    new string[] { senderIdColumn, receiverIdColumn, objectIdColumn },
                    new string[] { "Id", senderIdColumn, senderNameColumn, receiverIdColumn, receiverNameColumn, objectIdColumn, objectNameColumn },
                    includeBody);

                command.CommandText =
                    "select " +
                    QuoteIdent("Id") + " as message_id, " +
                    SelectColumn(senderIdColumn, "sender_id") + ", " +
                    SelectColumn(FirstNonEmpty(senderNameColumn, objectNameColumn), "sender_name") + ", " +
                    SelectColumn(receiverIdColumn, "receiver_id") + ", " +
                    SelectColumn(FirstNonEmpty(objectIdColumn, receiverIdColumn, senderIdColumn), "conversation_id") + ", " +
                    SelectColumn(timeColumn, "timestamp") + ", " +
                    SelectColumn(readColumn, "read_state") + ", " +
                    BodySelect(columnMap, table, includeBody) +
                    " from " + QuoteIdent(table) +
                    " where " + string.Join(" and ", where.ToArray()) +
                    " order by " + OrderByExpression(timeColumn) + " desc limit " + Convert.ToString(limit);

                using (DbDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read() && messages.Count < limit * 3)
                    {
                        string messageId = ReaderString(reader, "message_id");
                        string timestamp = ReaderString(reader, "timestamp");
                        string contentText = includeBody ? ReaderString(reader, "content_text") : "";
                        List<Dictionary<string, object>> attachments = includeAttachmentMetadata ? ReadAttachmentsForMessage(connection, columnMap, messageId) : new List<Dictionary<string, object>>();
                        messages.Add(new Dictionary<string, object>
                        {
                            { "message_id", messageId },
                            { "id", messageId },
                            { "conversation_id", ReaderString(reader, "conversation_id") },
                            { "conversation_type", "direct" },
                            { "sender_id", ReaderString(reader, "sender_id") },
                            { "sender_name", ReaderString(reader, "sender_name") },
                            { "receiver_id", ReaderString(reader, "receiver_id") },
                            { "text", contentText },
                            { "content_text", contentText },
                            { "content_type", ContentType(contentText, attachments) },
                            { "timestamp", timestamp },
                            { "created_at", timestamp },
                            { "subject", "" },
                            { "read", ReaderBool(reader, "read_state") },
                            { "source", "local_readonly" },
                            { "raw_ref", "msglib:" + table },
                            { "attachments", attachments },
                            { "sort_key", timestamp + "|" + messageId }
                        });
                    }
                }
            }
            sourceTables.Add(table);
        }

        private static void ReadGroupMessages(
            DbConnection connection,
            Dictionary<string, HashSet<string>> columnMap,
            string conversationId,
            string query,
            string since,
            int limit,
            bool includeBody,
            bool includeAttachmentMetadata,
            List<Dictionary<string, object>> messages,
            HashSet<string> sourceTables)
        {
            const string table = "tblMsgGroupPersonMsg";
            if (!HasColumns(columnMap, table, new string[] { "Id" })) return;

            string senderIdColumn = FirstExistingColumn(columnMap, table, new string[] { "SndPersonId", "SessionPersonId", "PersonId" });
            string senderNameColumn = FirstExistingColumn(columnMap, table, new string[] { "SndPerson", "SessionPersonName", "PersonName" });
            string groupIdColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgGroupId", "GroupJID", "GroupId" });
            string groupNameColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgGroupName", "GroupName", "SessionPersonName" });
            string timeColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgTime", "ActionTime", "CreateTime", "SendTime" });
            string readColumn = FirstExistingColumn(columnMap, table, new string[] { "IsRead", "ReadState", "MsgReadState" });

            using (DbCommand command = connection.CreateCommand())
            {
                var where = new List<string>();
                where.Add("coalesce(" + QuoteIdent("Id") + ", '') <> ''");
                AddListMessageWhere(command, where, table, columnMap, conversationId, query, since, timeColumn,
                    new string[] { groupIdColumn, senderIdColumn },
                    new string[] { "Id", senderIdColumn, senderNameColumn, groupIdColumn, groupNameColumn },
                    includeBody);

                command.CommandText =
                    "select " +
                    QuoteIdent("Id") + " as message_id, " +
                    SelectColumn(senderIdColumn, "sender_id") + ", " +
                    SelectColumn(senderNameColumn, "sender_name") + ", " +
                    SelectColumn(groupIdColumn, "conversation_id") + ", " +
                    SelectColumn(timeColumn, "timestamp") + ", " +
                    SelectColumn(readColumn, "read_state") + ", " +
                    BodySelect(columnMap, table, includeBody) +
                    " from " + QuoteIdent(table) +
                    " where " + string.Join(" and ", where.ToArray()) +
                    " order by " + OrderByExpression(timeColumn) + " desc limit " + Convert.ToString(limit);

                using (DbDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read() && messages.Count < limit * 3)
                    {
                        string messageId = ReaderString(reader, "message_id");
                        string timestamp = ReaderString(reader, "timestamp");
                        string contentText = includeBody ? ReaderString(reader, "content_text") : "";
                        List<Dictionary<string, object>> attachments = includeAttachmentMetadata ? ReadAttachmentsForMessage(connection, columnMap, messageId) : new List<Dictionary<string, object>>();
                        messages.Add(new Dictionary<string, object>
                        {
                            { "message_id", messageId },
                            { "id", messageId },
                            { "conversation_id", ReaderString(reader, "conversation_id") },
                            { "conversation_type", "group" },
                            { "sender_id", ReaderString(reader, "sender_id") },
                            { "sender_name", ReaderString(reader, "sender_name") },
                            { "receiver_id", "" },
                            { "text", contentText },
                            { "content_text", contentText },
                            { "content_type", ContentType(contentText, attachments) },
                            { "timestamp", timestamp },
                            { "created_at", timestamp },
                            { "subject", "" },
                            { "read", ReaderBool(reader, "read_state") },
                            { "source", "local_readonly" },
                            { "raw_ref", "msglib:" + table },
                            { "attachments", attachments },
                            { "sort_key", timestamp + "|" + messageId }
                        });
                    }
                }
            }
            sourceTables.Add(table);
        }

        private static void ReadSystemMessages(
            DbConnection connection,
            Dictionary<string, HashSet<string>> columnMap,
            string conversationId,
            string query,
            string since,
            int limit,
            bool includeBody,
            bool includeAttachmentMetadata,
            List<Dictionary<string, object>> messages,
            HashSet<string> sourceTables)
        {
            const string table = "TD_SystemMessageRecord";
            string idColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgGuid", "Id" });
            if (string.IsNullOrWhiteSpace(idColumn)) return;

            string senderIdColumn = FirstExistingColumn(columnMap, table, new string[] { "SendPersonJid", "PersonID", "SourceID" });
            string senderNameColumn = FirstExistingColumn(columnMap, table, new string[] { "SendPersonName", "PersonName", "SourceName" });
            string titleColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgTitle", "Title" });
            string timeColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgTime", "ActionTime", "CreateTime", "SendTime" });
            string readColumn = FirstExistingColumn(columnMap, table, new string[] { "MsgReadState", "IsRead", "ReadState" });

            using (DbCommand command = connection.CreateCommand())
            {
                var where = new List<string>();
                where.Add("coalesce(" + QuoteIdent(idColumn) + ", '') <> ''");
                AddListMessageWhere(command, where, table, columnMap, conversationId, query, since, timeColumn,
                    new string[] { senderIdColumn },
                    new string[] { idColumn, senderIdColumn, senderNameColumn, titleColumn },
                    includeBody);

                command.CommandText =
                    "select " +
                    QuoteIdent(idColumn) + " as message_id, " +
                    SelectColumn(senderIdColumn, "sender_id") + ", " +
                    SelectColumn(senderNameColumn, "sender_name") + ", " +
                    SelectColumn(titleColumn, "subject") + ", " +
                    SelectColumn(timeColumn, "timestamp") + ", " +
                    SelectColumn(readColumn, "read_state") + ", " +
                    BodySelect(columnMap, table, includeBody) +
                    " from " + QuoteIdent(table) +
                    " where " + string.Join(" and ", where.ToArray()) +
                    " order by " + OrderByExpression(timeColumn) + " desc limit " + Convert.ToString(limit);

                using (DbDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read() && messages.Count < limit * 3)
                    {
                        string messageId = ReaderString(reader, "message_id");
                        string timestamp = ReaderString(reader, "timestamp");
                        string contentText = includeBody ? ReaderString(reader, "content_text") : "";
                        List<Dictionary<string, object>> attachments = includeAttachmentMetadata ? ReadAttachmentsForMessage(connection, columnMap, messageId) : new List<Dictionary<string, object>>();
                        messages.Add(new Dictionary<string, object>
                        {
                            { "message_id", messageId },
                            { "id", messageId },
                            { "conversation_id", ReaderString(reader, "sender_id") },
                            { "conversation_type", "system" },
                            { "sender_id", ReaderString(reader, "sender_id") },
                            { "sender_name", ReaderString(reader, "sender_name") },
                            { "receiver_id", "" },
                            { "text", contentText },
                            { "content_text", contentText },
                            { "content_type", ContentType(contentText, attachments) },
                            { "timestamp", timestamp },
                            { "created_at", timestamp },
                            { "subject", ReaderString(reader, "subject") },
                            { "read", ReaderBool(reader, "read_state") },
                            { "source", "local_readonly" },
                            { "raw_ref", "msglib:" + table },
                            { "attachments", attachments },
                            { "sort_key", timestamp + "|" + messageId }
                        });
                    }
                }
            }
            sourceTables.Add(table);
        }

        private static void AddListMessageWhere(
            DbCommand command,
            List<string> where,
            string table,
            Dictionary<string, HashSet<string>> columnMap,
            string conversationId,
            string query,
            string since,
            string timeColumn,
            string[] conversationColumns,
            string[] queryColumns,
            bool includeBody)
        {
            if (!string.IsNullOrWhiteSpace(conversationId))
            {
                var parts = new List<string>();
                foreach (string column in conversationColumns)
                {
                    if (!string.IsNullOrWhiteSpace(column) && HasColumns(columnMap, table, new string[] { column }))
                    {
                        parts.Add(QuoteIdent(column) + " = @conversation_id");
                    }
                }
                if (parts.Count > 0)
                {
                    where.Add("(" + string.Join(" or ", parts.ToArray()) + ")");
                    AddParameter(command, "@conversation_id", conversationId);
                }
            }

            if (!string.IsNullOrWhiteSpace(query))
            {
                var parts = new List<string>();
                foreach (string column in queryColumns)
                {
                    if (!string.IsNullOrWhiteSpace(column) && HasColumns(columnMap, table, new string[] { column }))
                    {
                        parts.Add(QuoteIdent(column) + " like @query");
                    }
                }
                if (includeBody)
                {
                    if (HasColumns(columnMap, table, new string[] { "MsgText" })) parts.Add(QuoteIdent("MsgText") + " like @query");
                    if (HasColumns(columnMap, table, new string[] { "MessageBody" })) parts.Add(QuoteIdent("MessageBody") + " like @query");
                }
                if (parts.Count > 0)
                {
                    where.Add("(" + string.Join(" or ", parts.ToArray()) + ")");
                    AddParameter(command, "@query", "%" + query + "%");
                }
            }

            if (!string.IsNullOrWhiteSpace(since) && !string.IsNullOrWhiteSpace(timeColumn) && HasColumns(columnMap, table, new string[] { timeColumn }))
            {
                where.Add(QuoteIdent(timeColumn) + " >= @since");
                AddParameter(command, "@since", since);
            }
        }

        private static string BodySelect(Dictionary<string, HashSet<string>> columnMap, string table, bool includeBody)
        {
            if (!includeBody)
            {
                return "'' as content_text";
            }

            var expressions = new List<string>();
            if (HasColumns(columnMap, table, new string[] { "MsgText" })) expressions.Add(QuoteIdent("MsgText"));
            if (HasColumns(columnMap, table, new string[] { "MessageBody" })) expressions.Add(QuoteIdent("MessageBody"));
            if (expressions.Count == 0)
            {
                return "'' as content_text";
            }
            expressions.Add("''");
            return "coalesce(" + string.Join(", ", expressions.ToArray()) + ") as content_text";
        }

        private static List<Dictionary<string, object>> ReadAttachmentsForMessage(DbConnection connection, Dictionary<string, HashSet<string>> columnMap, string messageId)
        {
            var attachments = new List<Dictionary<string, object>>();
            const string table = "TD_ReceiveFileRecord";
            if (string.IsNullOrWhiteSpace(messageId)) return attachments;
            if (!HasColumns(columnMap, table, new string[] { "ReceiveMsgGuid", "FileName" })) return attachments;

            string sizeColumn = FirstExistingColumn(columnMap, table, new string[] { "FileSize", "Size" });
            string sourceColumn = FirstExistingColumn(columnMap, table, new string[] { "SourceID", "FileGuid", "FileId" });
            using (DbCommand command = connection.CreateCommand())
            {
                command.CommandText =
                    "select " +
                    SelectColumn(sourceColumn, "source_id") + ", " +
                    SelectColumn("FileName", "file_name") + ", " +
                    SelectColumn(sizeColumn, "size_bytes") +
                    " from " + QuoteIdent(table) +
                    " where " + QuoteIdent("ReceiveMsgGuid") + " = @message_id limit 20";
                AddParameter(command, "@message_id", messageId);

                using (DbDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        string fileName = SafeFileName(ReaderString(reader, "file_name"));
                        if (string.IsNullOrWhiteSpace(fileName)) continue;
                        string sourceId = ReaderString(reader, "source_id");
                        attachments.Add(new Dictionary<string, object>
                        {
                            { "file_id", FirstNonEmpty(sourceId, messageId + ":" + fileName) },
                            { "file_name", fileName },
                            { "size_bytes", ReaderInt64(reader, "size_bytes") },
                            { "download_ref", "" }
                        });
                    }
                }
            }
            return attachments;
        }

        private static bool HasColumns(Dictionary<string, HashSet<string>> columnMap, string table, string[] columns)
        {
            if (!columnMap.ContainsKey(table)) return false;
            foreach (string column in columns)
            {
                if (string.IsNullOrWhiteSpace(column)) return false;
                if (!columnMap[table].Contains(column)) return false;
            }
            return true;
        }

        private static string FirstExistingColumn(Dictionary<string, HashSet<string>> columnMap, string table, string[] columns)
        {
            if (!columnMap.ContainsKey(table)) return "";
            foreach (string column in columns)
            {
                if (!string.IsNullOrWhiteSpace(column) && columnMap[table].Contains(column))
                {
                    return column;
                }
            }
            return "";
        }

        private static string SelectColumn(string column, string alias)
        {
            if (string.IsNullOrWhiteSpace(column))
            {
                return "'' as " + QuoteIdent(alias);
            }
            return QuoteIdent(column) + " as " + QuoteIdent(alias);
        }

        private static string OrderByExpression(string column)
        {
            if (string.IsNullOrWhiteSpace(column))
            {
                return "1";
            }
            return QuoteIdent(column);
        }

        private static string ReaderString(DbDataReader reader, string name)
        {
            try
            {
                object value = reader[name];
                if (value == null || value == DBNull.Value) return "";
                return Convert.ToString(value);
            }
            catch
            {
                return "";
            }
        }

        private static bool ReaderBool(DbDataReader reader, string name)
        {
            string value = ReaderString(reader, name).Trim();
            if (string.IsNullOrWhiteSpace(value)) return false;
            return string.Equals(value, "1", StringComparison.OrdinalIgnoreCase) ||
                string.Equals(value, "true", StringComparison.OrdinalIgnoreCase) ||
                string.Equals(value, "read", StringComparison.OrdinalIgnoreCase) ||
                string.Equals(value, "yes", StringComparison.OrdinalIgnoreCase);
        }

        private static long ReaderInt64(DbDataReader reader, string name)
        {
            string value = ReaderString(reader, name).Trim();
            long parsed;
            if (long.TryParse(value, out parsed)) return parsed;
            return 0;
        }

        private static string FirstNonEmpty(params string[] values)
        {
            foreach (string value in values)
            {
                if (!string.IsNullOrWhiteSpace(value)) return value;
            }
            return "";
        }

        private static string ContentType(string contentText, List<Dictionary<string, object>> attachments)
        {
            if (attachments != null && attachments.Count > 0) return "file";
            if (string.IsNullOrWhiteSpace(contentText)) return "unknown";
            return "text";
        }

        private static int CompareMessagesDescending(Dictionary<string, object> left, Dictionary<string, object> right)
        {
            string leftKey = left.ContainsKey("sort_key") ? Convert.ToString(left["sort_key"]) : "";
            string rightKey = right.ContainsKey("sort_key") ? Convert.ToString(right["sort_key"]) : "";
            return string.Compare(rightKey, leftKey, StringComparison.Ordinal);
        }

        private static string[] ToSortedArray(HashSet<string> values)
        {
            var list = new List<string>();
            foreach (string value in values)
            {
                list.Add(value);
            }
            list.Sort(StringComparer.OrdinalIgnoreCase);
            return list.ToArray();
        }

        private static void AddParameter(DbCommand command, string name, object value)
        {
            DbParameter parameter = command.CreateParameter();
            parameter.ParameterName = name;
            parameter.Value = value ?? DBNull.Value;
            command.Parameters.Add(parameter);
        }

        private static string SafeFileName(string value)
        {
            if (string.IsNullOrWhiteSpace(value)) return "";
            try
            {
                return Path.GetFileName(value);
            }
            catch
            {
                int slash = Math.Max(value.LastIndexOf('/'), value.LastIndexOf('\\'));
                if (slash >= 0 && slash + 1 < value.Length) return value.Substring(slash + 1);
                return value;
            }
        }


        private sealed class DisplayEntitySpec
        {
            public string EntityType;
            public string SourceTable;
            public string JidColumn;
            public string NameColumn;
            public double Confidence;
        }

        private static HashSet<string> BuildDisplayEntityTableSet(string entityType)
        {
            var tables = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (DisplayEntitySpec spec in BuildDisplayEntitySpecs(entityType))
            {
                tables.Add(spec.SourceTable);
            }
            return tables;
        }

        private static Dictionary<string, HashSet<string>> BuildColumnMap(List<Dictionary<string, object>> columns)
        {
            var columnMap = new Dictionary<string, HashSet<string>>(StringComparer.OrdinalIgnoreCase);
            foreach (Dictionary<string, object> column in columns)
            {
                string table = Convert.ToString(column["table"]);
                string name = Convert.ToString(column["name"]);
                if (!columnMap.ContainsKey(table)) columnMap[table] = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
                columnMap[table].Add(name);
            }
            return columnMap;
        }

        private static List<DisplayEntitySpec> BuildDisplayEntitySpecs(string entityType)
        {
            var specs = new List<DisplayEntitySpec>();
            if (string.Equals(entityType, "contacts", StringComparison.OrdinalIgnoreCase))
            {
                AddEntitySpec(specs, entityType, "TD_Roster", "JId", "Nick", 0.95);
                AddEntitySpec(specs, entityType, "TD_CustomEffigy", "PersonJid", "PersonName", 0.90);
                AddEntitySpec(specs, entityType, "tblRecent", "PersonId", "PersonName", 0.70);
                AddEntitySpec(specs, entityType, "tblChatLevel", "PersonId", "PersonName", 0.70);
                AddEntitySpec(specs, entityType, "tblPersonMsg", "SndPersonId", "SndPerson", 0.55);
                AddEntitySpec(specs, entityType, "tblPersonMsg", "RecvPersonId", "RecvPerson", 0.55);
                AddEntitySpec(specs, entityType, "tblPersonMsg", "ObjPersonId", "ObjPerson", 0.55);
            }
            else if (string.Equals(entityType, "groups", StringComparison.OrdinalIgnoreCase))
            {
                AddEntitySpec(specs, entityType, "TD_WorkGroupAuth", "GroupJID", "GroupName", 0.90);
                AddEntitySpec(specs, entityType, "TD_WorkGroupAuth", "ChildGroupJid", "GroupName", 0.80);
                AddEntitySpec(specs, entityType, "tblMsgGroupPersonMsg", "MsgGroupId", "MsgGroupName", 0.70);
                AddEntitySpec(specs, entityType, "tblMsgGroupPersonMsg", "SessionPersonId", "SessionPersonName", 0.60);
            }
            return specs;
        }

        private static void AddEntitySpec(List<DisplayEntitySpec> specs, string entityType, string table, string jidColumn, string nameColumn, double confidence)
        {
            specs.Add(new DisplayEntitySpec
            {
                EntityType = entityType,
                SourceTable = table,
                JidColumn = jidColumn,
                NameColumn = nameColumn,
                Confidence = confidence
            });
        }

        private static List<Dictionary<string, object>> ReadDisplayEntities(DbConnection connection, string entityType, string query, int limit, Dictionary<string, HashSet<string>> columnMap)
        {
            var rows = new List<Dictionary<string, object>>();
            var seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            foreach (DisplayEntitySpec spec in BuildDisplayEntitySpecs(entityType))
            {
                if (rows.Count >= limit) break;
                if (!columnMap.ContainsKey(spec.SourceTable)) continue;
                if (!columnMap[spec.SourceTable].Contains(spec.JidColumn)) continue;
                if (!columnMap[spec.SourceTable].Contains(spec.NameColumn)) continue;
                ReadDisplayEntitiesForSpec(connection, spec, query, limit - rows.Count, rows, seen);
            }
            return rows;
        }

        private static void ReadDisplayEntitiesForSpec(DbConnection connection, DisplayEntitySpec spec, string query, int limit, List<Dictionary<string, object>> rows, HashSet<string> seen)
        {
            if (limit <= 0) return;
            using (DbCommand command = connection.CreateCommand())
            {
                string jid = QuoteIdent(spec.JidColumn);
                string name = QuoteIdent(spec.NameColumn);
                command.CommandText =
                    "select " + jid + " as jid, " + name + " as display_name from " + QuoteIdent(spec.SourceTable) +
                    " where (coalesce(" + jid + ", '') <> '' or coalesce(" + name + ", '') <> '')";
                if (!string.IsNullOrWhiteSpace(query))
                {
                    command.CommandText += " and (" + jid + " like @query or " + name + " like @query)";
                    DbParameter queryParam = command.CreateParameter();
                    queryParam.ParameterName = "@query";
                    queryParam.Value = "%" + query + "%";
                    command.Parameters.Add(queryParam);
                }
                command.CommandText += " limit " + Convert.ToString(limit);

                using (DbDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read() && rows.Count < limit)
                    {
                        string entityJid = Convert.ToString(reader["jid"]);
                        string displayName = Convert.ToString(reader["display_name"]);
                        if (string.IsNullOrWhiteSpace(entityJid) && string.IsNullOrWhiteSpace(displayName)) continue;
                        string key = spec.EntityType + "|" + entityJid + "|" + displayName + "|" + spec.SourceTable;
                        if (seen.Contains(key)) continue;
                        seen.Add(key);
                        rows.Add(new Dictionary<string, object>
                        {
                            { "entity_type", spec.EntityType },
                            { "source_table", spec.SourceTable },
                            { "jid", entityJid },
                            { "display_name", displayName },
                            { "confidence", spec.Confidence },
                            { "matched_columns", new string[] { spec.JidColumn, spec.NameColumn } }
                        });
                    }
                }
            }
        }

        private static void AddSource(List<Dictionary<string, object>> sources, HashSet<string> tableSet, Dictionary<string, HashSet<string>> columnMap, string sourceName, string table, string[] columns)
        {
            var presentColumns = new List<string>();
            if (columnMap.ContainsKey(table))
            {
                foreach (string column in columns)
                {
                    if (columnMap[table].Contains(column)) presentColumns.Add(column);
                }
            }
            sources.Add(new Dictionary<string, object>
            {
                { "source", sourceName },
                { "table", table },
                { "available", tableSet.Contains(table) && presentColumns.Count > 0 },
                { "required_columns", columns },
                { "present_columns", presentColumns.ToArray() }
            });
        }

        private static string ExecuteScalar(DbConnection connection, string sql)
        {
            using (DbCommand command = connection.CreateCommand())
            {
                command.CommandText = sql;
                object value = command.ExecuteScalar();
                return Convert.ToString(value);
            }
        }

        private static void TryExecuteNonQuery(DbConnection connection, string sql)
        {
            try
            {
                using (DbCommand command = connection.CreateCommand())
                {
                    command.CommandText = sql;
                    command.ExecuteNonQuery();
                }
            }
            catch
            {
            }
        }

        private static string QuoteIdent(string value)
        {
            return "\"" + value.Replace("\"", "\"\"") + "\"";
        }

        private static int Clamp(int value, int min, int max)
        {
            if (value < min) return min;
            if (value > max) return max;
            return value;
        }
    }
}