package services

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"sync"
	"time"
	"voidraft/internal/models"

	"github.com/wailsapp/wails/v3/pkg/application"
	"github.com/wailsapp/wails/v3/pkg/services/log"
	_ "modernc.org/sqlite" // SQLite driver
)

// SQL constants for document operations
const (

	// Document operations
	sqlGetDocumentByID = `
SELECT id, title, content, created_at, updated_at, is_deleted 
FROM documents 
WHERE id = ?`

	sqlInsertDocument = `
INSERT INTO documents (title, content, created_at, updated_at, is_deleted)
VALUES (?, ?, ?, ?, 0)`

	sqlUpdateDocumentContent = `
UPDATE documents 
SET content = ?, updated_at = ?
WHERE id = ?`

	sqlUpdateDocumentTitle = `
UPDATE documents 
SET title = ?, updated_at = ?
WHERE id = ?`

	sqlMarkDocumentAsDeleted = `
UPDATE documents 
SET is_deleted = 1, updated_at = ?
WHERE id = ?`

	sqlRestoreDocument = `
UPDATE documents 
SET is_deleted = 0, updated_at = ?
WHERE id = ?`

	sqlListAllDocumentsMeta = `
SELECT id, title, created_at, updated_at 
FROM documents 
WHERE is_deleted = 0
ORDER BY updated_at DESC`

	sqlListDeletedDocumentsMeta = `
SELECT id, title, created_at, updated_at 
FROM documents 
WHERE is_deleted = 1
ORDER BY updated_at DESC`

	sqlGetFirstDocumentID = `
SELECT id FROM documents WHERE is_deleted = 0 ORDER BY id LIMIT 1`

	sqlCountDocuments = `SELECT COUNT(*) FROM documents WHERE is_deleted = 0`

	sqlDefaultDocumentID = 1 // 默认文档的ID
)

// DocumentService provides document management functionality
type DocumentService struct {
	databaseService *DatabaseService
	logger          *log.LoggerService
	mu              sync.RWMutex
	ctx             context.Context
}

// NewDocumentService creates a new document service
func NewDocumentService(databaseService *DatabaseService, logger *log.LoggerService) *DocumentService {
	if logger == nil {
		logger = log.New()
	}

	return &DocumentService{
		databaseService: databaseService,
		logger:          logger,
	}
}

// OnStartup initializes the service when the application starts
func (ds *DocumentService) OnStartup(ctx context.Context, _ application.ServiceOptions) error {
	ds.ctx = ctx
	// Ensure default document exists
	if err := ds.ensureDefaultDocument(); err != nil {
		return fmt.Errorf("failed to ensure default document: %w", err)
	}
	return nil
}

// ensureDefaultDocument ensures a default document exists
func (ds *DocumentService) ensureDefaultDocument() error {
	// Check if any document exists
	var count int
	db := ds.databaseService.GetDB()
	err := db.QueryRow(sqlCountDocuments).Scan(&count)
	if err != nil {
		return err
	}

	// If no documents exist, create default document
	if count == 0 {
		defaultDoc := models.NewDefaultDocument()
		_, err := ds.CreateDocument(defaultDoc.Title)
		return err
	}
	return nil
}

// GetDocumentByID gets a document by ID
func (ds *DocumentService) GetDocumentByID(id int64) (*models.Document, error) {
	ds.mu.RLock()
	defer ds.mu.RUnlock()

	var doc models.Document
	var isDeletedInt int
	db := ds.databaseService.GetDB()
	row := db.QueryRow(sqlGetDocumentByID, id)
	err := row.Scan(&doc.ID, &doc.Title, &doc.Content, &doc.CreatedAt, &doc.UpdatedAt, &isDeletedInt)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			return nil, nil
		}
		return nil, fmt.Errorf("failed to get document by ID: %w", err)
	}
	doc.IsDeleted = isDeletedInt == 1

	return &doc, nil
}

// CreateDocument creates a new document and returns the created document with ID
func (ds *DocumentService) CreateDocument(title string) (*models.Document, error) {
	ds.mu.Lock()
	defer ds.mu.Unlock()

	// Create document with default content
	now := time.Now()
	doc := &models.Document{
		Title:     title,
		Content:   "∞∞∞text-a\n",
		CreatedAt: now,
		UpdatedAt: now,
		IsDeleted: false,
	}

	db := ds.databaseService.GetDB()
	result, err := db.Exec(sqlInsertDocument, doc.Title, doc.Content, doc.CreatedAt, doc.UpdatedAt)
	if err != nil {
		return nil, fmt.Errorf("failed to create document: %w", err)
	}

	// Get the auto-generated ID
	id, err := result.LastInsertId()
	if err != nil {
		return nil, fmt.Errorf("failed to get last insert ID: %w", err)
	}

	// Return the created document with ID
	doc.ID = id
	return doc, nil
}

// UpdateDocumentContent updates the content of a document
func (ds *DocumentService) UpdateDocumentContent(id int64, content string) error {
	ds.mu.Lock()
	defer ds.mu.Unlock()

	db := ds.databaseService.GetDB()
	_, err := db.Exec(sqlUpdateDocumentContent, content, time.Now(), id)
	if err != nil {
		return fmt.Errorf("failed to update document content: %w", err)
	}
	return nil
}

// UpdateDocumentTitle updates the title of a document
func (ds *DocumentService) UpdateDocumentTitle(id int64, title string) error {
	ds.mu.Lock()
	defer ds.mu.Unlock()

	db := ds.databaseService.GetDB()
	_, err := db.Exec(sqlUpdateDocumentTitle, title, time.Now(), id)
	if err != nil {
		return fmt.Errorf("failed to update document title: %w", err)
	}
	return nil
}

// DeleteDocument marks a document as deleted (default document with ID=1 cannot be deleted)
func (ds *DocumentService) DeleteDocument(id int64) error {
	ds.mu.Lock()
	defer ds.mu.Unlock()

	// 不允许删除默认文档
	if id == sqlDefaultDocumentID {
		return fmt.Errorf("cannot delete the default document")
	}

	db := ds.databaseService.GetDB()
	_, err := db.Exec(sqlMarkDocumentAsDeleted, time.Now(), id)
	if err != nil {
		return fmt.Errorf("failed to mark document as deleted: %w", err)
	}
	return nil
}

// RestoreDocument restores a deleted document
func (ds *DocumentService) RestoreDocument(id int64) error {
	ds.mu.Lock()
	defer ds.mu.Unlock()

	db := ds.databaseService.GetDB()
	_, err := db.Exec(sqlRestoreDocument, time.Now(), id)
	if err != nil {
		return fmt.Errorf("failed to restore document: %w", err)
	}
	return nil
}

// ListAllDocumentsMeta lists all active (non-deleted) document metadata
func (ds *DocumentService) ListAllDocumentsMeta() ([]*models.Document, error) {
	ds.mu.RLock()
	defer ds.mu.RUnlock()

	db := ds.databaseService.GetDB()
	rows, err := db.Query(sqlListAllDocumentsMeta)
	if err != nil {
		return nil, fmt.Errorf("failed to list document meta: %w", err)
	}
	defer rows.Close()

	var documents []*models.Document
	for rows.Next() {
		var doc models.Document
		err := rows.Scan(&doc.ID, &doc.Title, &doc.CreatedAt, &doc.UpdatedAt)
		if err != nil {
			return nil, fmt.Errorf("failed to scan document meta: %w", err)
		}
		doc.IsDeleted = false
		documents = append(documents, &doc)
	}

	return documents, nil
}

// ListDeletedDocumentsMeta lists all deleted document metadata
func (ds *DocumentService) ListDeletedDocumentsMeta() ([]*models.Document, error) {
	ds.mu.RLock()
	defer ds.mu.RUnlock()

	db := ds.databaseService.GetDB()
	rows, err := db.Query(sqlListDeletedDocumentsMeta)
	if err != nil {
		return nil, fmt.Errorf("failed to list deleted document meta: %w", err)
	}
	defer rows.Close()

	var documents []*models.Document
	for rows.Next() {
		var doc models.Document
		err := rows.Scan(&doc.ID, &doc.Title, &doc.CreatedAt, &doc.UpdatedAt)
		if err != nil {
			return nil, fmt.Errorf("failed to scan deleted document meta: %w", err)
		}
		doc.IsDeleted = true
		documents = append(documents, &doc)
	}

	return documents, nil
}

// GetFirstDocumentID gets the first active document's ID for frontend initialization
func (ds *DocumentService) GetFirstDocumentID() (int64, error) {
	ds.mu.RLock()
	defer ds.mu.RUnlock()

	db := ds.databaseService.GetDB()
	var id int64
	err := db.QueryRow(sqlGetFirstDocumentID).Scan(&id)
	if err != nil {
		if err == sql.ErrNoRows {
			return 0, nil // No documents exist
		}
		return 0, fmt.Errorf("failed to get first document ID: %w", err)
	}
	return id, nil
}