package service

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"time"

	"AI-Expert-Sidebar/internal/database"
	"AI-Expert-Sidebar/internal/models"
)

// ListLibraries returns all registered knowledge libraries with entry counts.
func ListLibraries() ([]models.Library, error) {
	sdb := database.GetSettings()
	if sdb == nil {
		return nil, fmt.Errorf("settings DB not ready")
	}
	var libs []models.Library
	if err := sdb.Order("created_at asc").Find(&libs).Error; err != nil {
		return nil, err
	}
	// Populate entry count for each library
	for i, lib := range libs {
		libs[i].EntryCount = countEntries(lib.FilePath)
	}
	return libs, nil
}

// CreateLibrary registers a new knowledge library and creates its SQLite file.
func CreateLibrary(name, description string) (*models.Library, error) {
	sdb := database.GetSettings()
	dir := database.DataDir

	fileName := sanitizeFileName(name) + ".db"
	filePath := filepath.Join(dir, fileName)

	// Ensure uniqueness of file path
	if _, err := os.Stat(filePath); err == nil {
		filePath = filepath.Join(dir, sanitizeFileName(name)+"_"+fmt.Sprintf("%d", time.Now().Unix())+".db")
	}

	if err := database.NewLibraryDB(filePath); err != nil {
		return nil, fmt.Errorf("create library DB: %w", err)
	}

	lib := models.Library{Name: name, Description: description, FilePath: filePath}
	if err := sdb.Create(&lib).Error; err != nil {
		os.Remove(filePath) // rollback file
		return nil, err
	}
	log.Printf("[Library] Created: %s → %s", name, filePath)
	return &lib, nil
}

// SwitchLibrary makes the named library active.
func SwitchLibrary(name string) error {
	sdb := database.GetSettings()
	var lib models.Library
	if err := sdb.Where("name = ?", name).First(&lib).Error; err != nil {
		return fmt.Errorf("library %q not found", name)
	}
	return database.OpenLibrary(lib)
}

// DeleteLibrary removes a library from the registry (and optionally its file).
func DeleteLibrary(name string, deleteFile bool) error {
	sdb := database.GetSettings()
	var lib models.Library
	if err := sdb.Where("name = ?", name).First(&lib).Error; err != nil {
		return fmt.Errorf("library %q not found", name)
	}
	if err := sdb.Delete(&lib).Error; err != nil {
		return err
	}
	if deleteFile {
		return os.Remove(lib.FilePath)
	}
	return nil
}

// InitLibraries restores the last active library or creates the default one.
func InitLibraries() error {
	sdb := database.GetSettings()
	// Check active_library preference
	var setting models.AppSetting
	if sdb.Where("key = ?", "active_library").First(&setting).Error == nil {
		if err := SwitchLibrary(setting.Value); err == nil {
			return nil // restored successfully
		}
	}
	// No preference or stale — find first library
	var lib models.Library
	if sdb.Order("created_at asc").First(&lib).Error == nil {
		return database.OpenLibrary(lib)
	}
	// No libraries at all — create default
	lib2, err := CreateLibrary("默认知识库", "自动创建的默认知识库")
	if err != nil {
		return err
	}
	return database.OpenLibrary(*lib2)
}

// ── helpers ───────────────────────────────────────────────────────────────────

func countEntries(filePath string) int {
	db, err := database.NewLibraryDBReadOnly(filePath)
	if err != nil {
		return -1
	}
	var count int64
	db.Model(&models.Entry{}).Count(&count)
	return int(count)
}

func sanitizeFileName(name string) string {
	result := make([]rune, 0, len(name))
	for _, r := range name {
		if r == '/' || r == '\\' || r == ':' || r == '*' || r == '?' || r == '"' || r == '<' || r == '>' || r == '|' {
			result = append(result, '_')
		} else {
			result = append(result, r)
		}
	}
	if len(result) == 0 {
		return "library"
	}
	return string(result)
}