package tools

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/modelcontextprotocol/go-sdk/mcp"
)

const (
	ToolNameSendFile      = "isphere_send_file"
	EnvSendFileAllowedDir = "ISPHERE_SEND_FILE_ALLOWED_DIR"

	sendFileConnector      = "implatform-file-transfer"
	sendFileConnectorMode  = "preview-only"
	sendFilePreviewStage   = "preview"
	sendFileBlockedStage   = "blocked"
	sendFileProductionMode = "production"
)

type SendFileArgs struct {
	TargetType     string `json:"target_type" jsonschema:"target type; direct/contact or group/groupchat"`
	TargetID       string `json:"target_id" jsonschema:"contact or group id returned by iSphere search tools"`
	FilePath       string `json:"file_path" jsonschema:"local file path under ISPHERE_SEND_FILE_ALLOWED_DIR to hash and preview"`
	FileSHA256     string `json:"file_sha256,omitempty" jsonschema:"optional lowercase SHA256 hex of file contents; checked when supplied"`
	IdempotencyKey string `json:"idempotency_key" jsonschema:"required idempotency key; returned only as SHA256"`
	ExecutionMode  string `json:"execution_mode,omitempty" jsonschema:"preview/dry_run or production; production is blocked until file-send evidence passes"`
	Preview        bool   `json:"preview,omitempty" jsonschema:"accepted for contract compatibility; current implementation is preview-only"`
}

type normalizedSendFileArgs struct {
	TargetType           string
	TargetID             string
	TargetRef            string
	FileName             string
	FileSHA256           string
	FileSizeBytes        int64
	IdempotencyKeySHA256 string
	ExecutionMode        string
}

func RegisterISphereSendFileTool(server *mcp.Server) {
	mcp.AddTool[SendFileArgs, map[string]any](server, &mcp.Tool{
		Name:        ToolNameSendFile,
		Description: "Preview iSphere file sends with target/file hash/idempotency metadata; production file upload is blocked until sandbox evidence passes.",
	}, func(ctx context.Context, _ *mcp.CallToolRequest, input SendFileArgs) (*mcp.CallToolResult, map[string]any, error) {
		_ = ctx
		started := time.Now().UTC()
		normalized, blockedReason, err := normalizeSendFileArgs(input)
		if err != nil {
			return nil, nil, err
		}
		if blockedReason != "" {
			return nil, sendFileResponse(normalized, started, time.Now().UTC(), false, blockedReason), nil
		}
		if normalized.ExecutionMode == sendFileProductionMode {
			return nil, sendFileResponse(normalized, started, time.Now().UTC(), false, "production file upload is blocked until send-file sandbox evidence passes"), nil
		}
		return nil, sendFileResponse(normalized, started, time.Now().UTC(), true, ""), nil
	})
}

func normalizeSendFileArgs(input SendFileArgs) (normalizedSendFileArgs, string, error) {
	targetType, targetRefPrefix, err := normalizeSendFileTargetType(input.TargetType)
	if err != nil {
		return normalizedSendFileArgs{}, "", err
	}
	targetID := strings.TrimSpace(input.TargetID)
	if targetID == "" {
		return normalizedSendFileArgs{}, "", fmt.Errorf("%s target_id is required", ToolNameSendFile)
	}
	idempotencyKey := strings.TrimSpace(input.IdempotencyKey)
	if idempotencyKey == "" {
		return normalizedSendFileArgs{}, "", fmt.Errorf("%s idempotency_key is required", ToolNameSendFile)
	}
	mode, err := normalizeSendFileExecutionMode(input.ExecutionMode)
	if err != nil {
		return normalizedSendFileArgs{}, "", err
	}

	normalized := normalizedSendFileArgs{
		TargetType:           targetType,
		TargetID:             targetID,
		TargetRef:            targetRefPrefix + ":" + targetID,
		FileName:             filepath.Base(strings.TrimSpace(input.FilePath)),
		IdempotencyKeySHA256: sha256Hex(idempotencyKey),
		ExecutionMode:        mode,
	}
	fileSHA256, fileSize, blockedReason, err := inspectSendFilePath(input.FilePath, input.FileSHA256)
	if err != nil {
		return normalizedSendFileArgs{}, "", err
	}
	normalized.FileSHA256 = fileSHA256
	normalized.FileSizeBytes = fileSize
	return normalized, blockedReason, nil
}

func normalizeSendFileTargetType(value string) (string, string, error) {
	switch strings.ToLower(strings.TrimSpace(value)) {
	case "direct", "contact":
		return "direct", "contact", nil
	case "group", "groupchat":
		return "group", "group", nil
	default:
		return "", "", fmt.Errorf("%s target_type %q is not available; use direct or group", ToolNameSendFile, value)
	}
}

func normalizeSendFileExecutionMode(value string) (string, error) {
	switch strings.ToLower(strings.TrimSpace(value)) {
	case "", "preview", "dry_run", "dry-run":
		return "preview", nil
	case sendFileProductionMode:
		return sendFileProductionMode, nil
	default:
		return "", fmt.Errorf("%s execution_mode %q is not available; use preview or production", ToolNameSendFile, value)
	}
}

func inspectSendFilePath(filePath string, providedSHA256 string) (string, int64, string, error) {
	trimmedPath := strings.TrimSpace(filePath)
	if trimmedPath == "" {
		return "", 0, "", fmt.Errorf("%s file_path is required", ToolNameSendFile)
	}
	allowedDir := strings.TrimSpace(os.Getenv(EnvSendFileAllowedDir))
	if allowedDir == "" {
		return "", 0, fmt.Sprintf("%s is required before previewing local file paths", EnvSendFileAllowedDir), nil
	}
	allowedAbs, err := filepath.Abs(allowedDir)
	if err != nil {
		return "", 0, "", fmt.Errorf("%s allowed dir: %w", ToolNameSendFile, err)
	}
	fileAbs, err := filepath.Abs(trimmedPath)
	if err != nil {
		return "", 0, "", fmt.Errorf("%s file_path: %w", ToolNameSendFile, err)
	}
	if !sendFilePathInsideDir(fileAbs, allowedAbs) {
		return "", 0, fmt.Sprintf("file_path must stay inside %s", EnvSendFileAllowedDir), nil
	}
	info, err := os.Stat(fileAbs)
	if err != nil {
		if os.IsNotExist(err) {
			return "", 0, "file_path does not exist under allowed directory", nil
		}
		return "", 0, "", fmt.Errorf("%s stat file_path: %w", ToolNameSendFile, err)
	}
	if info.IsDir() {
		return "", 0, "file_path points to a directory; choose one file", nil
	}
	fileHash, err := sha256FileHex(fileAbs)
	if err != nil {
		return "", 0, "", fmt.Errorf("%s hash file_path: %w", ToolNameSendFile, err)
	}
	normalizedProvided := strings.ToLower(strings.TrimSpace(providedSHA256))
	if normalizedProvided != "" {
		if len(normalizedProvided) != 64 || !isLowerHex(normalizedProvided) {
			return "", 0, "", fmt.Errorf("%s file_sha256 must be a lowercase SHA256 hex value", ToolNameSendFile)
		}
		if normalizedProvided != fileHash {
			return "", 0, "", fmt.Errorf("%s file_sha256 does not match file contents", ToolNameSendFile)
		}
	}
	return fileHash, info.Size(), "", nil
}

func sendFilePathInsideDir(fileAbs string, allowedAbs string) bool {
	rel, err := filepath.Rel(filepath.Clean(allowedAbs), filepath.Clean(fileAbs))
	if err != nil {
		return false
	}
	if rel == "." {
		return true
	}
	return rel != ".." && !strings.HasPrefix(rel, ".."+string(os.PathSeparator)) && !filepath.IsAbs(rel)
}

func sha256FileHex(path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()
	hash := sha256.New()
	if _, err := io.Copy(hash, file); err != nil {
		return "", err
	}
	return hex.EncodeToString(hash.Sum(nil)), nil
}

func sendFileResponse(input normalizedSendFileArgs, started time.Time, finished time.Time, planned bool, blockedReason string) map[string]any {
	sideEffects := sendMessageNoSideEffects()
	status := "planned"
	stage := sendFilePreviewStage
	ok := true
	blocked := any(nil)
	if !planned {
		status = "blocked"
		stage = sendFileBlockedStage
		ok = false
		blocked = blockedReason
	}
	auditRef := "send-file:" + shortHash(input.FileSHA256) + ":" + shortHash(input.IdempotencyKeySHA256)
	return map[string]any{
		"ok":                      ok,
		"send_status":             status,
		"blocked_reason":          blocked,
		"execution_mode":          input.ExecutionMode,
		"connector":               sendFileConnector,
		"connector_mode":          sendFileConnectorMode,
		"connector_stage":         stage,
		"production_send_enabled": false,
		"real_send_attempted":     false,
		"target_ref":              input.TargetRef,
		"file_sha256":             input.FileSHA256,
		"file_size_bytes":         input.FileSizeBytes,
		"target": map[string]any{
			"target_type": input.TargetType,
			"target_id":   input.TargetID,
			"target_ref":  input.TargetRef,
		},
		"file": map[string]any{
			"file_name":             input.FileName,
			"file_sha256":           input.FileSHA256,
			"file_size_bytes":       input.FileSizeBytes,
			"allowed_dir_enforced":  true,
			"file_content_returned": false,
		},
		"idempotency": map[string]any{
			"idempotency_key_sha256": input.IdempotencyKeySHA256,
		},
		"side_effect_flags": sideEffects,
		"side_effects":      sideEffects,
		"audit": map[string]any{
			"tool":                ToolNameSendFile,
			"source":              sendFileConnector,
			"execution_mode":      input.ExecutionMode,
			"connector":           sendFileConnector,
			"connector_mode":      sendFileConnectorMode,
			"connector_stage":     stage,
			"file_sha256":         input.FileSHA256,
			"file_size_bytes":     input.FileSizeBytes,
			"target_ref":          input.TargetRef,
			"audit_ref":           auditRef,
			"started_at":          started.Format(time.RFC3339Nano),
			"finished_at":         finished.Format(time.RFC3339Nano),
			"result":              status,
			"real_send_attempted": false,
		},
	}
}