package database

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

	"github.com/glebarez/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"

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

var (
	mu          sync.RWMutex
	settingsDB  *gorm.DB
	activeLib   *gorm.DB
	activeLibNm string
	DataDir     string
)

// Init opens/creates the settings database ($HOME/Library/Application Support/AI-Expert-Sidebar/settings.db).
func Init() error {
	dir, err := appDataDir()
	if err != nil {
		return err
	}
	DataDir = dir
	if err := os.MkdirAll(dir, 0o750); err != nil {
		return fmt.Errorf("create data dir: %w", err)
	}

	db, err := openSQLite(filepath.Join(dir, "settings.db"))
	if err != nil {
		return fmt.Errorf("open settings.db: %w", err)
	}
	if err := db.AutoMigrate(&models.AppSetting{}, &models.Library{}); err != nil {
		return fmt.Errorf("migrate settings schema: %w", err)
	}
	mu.Lock()
	settingsDB = db
	mu.Unlock()
	log.Printf("[DB] Settings DB ready at %s/settings.db", dir)
	return nil
}

// OpenLibrary switches the active knowledge library.
func OpenLibrary(lib models.Library) error {
	db, err := openSQLite(lib.FilePath)
	if err != nil {
		return fmt.Errorf("open library %q: %w", lib.Name, err)
	}
	if err := db.AutoMigrate(&models.Entry{}); err != nil {
		return fmt.Errorf("migrate library %q: %w", lib.Name, err)
	}
	mu.Lock()
	activeLib = db
	activeLibNm = lib.Name
	mu.Unlock()
	// Persist preference
	settingsDB.Exec(
		"INSERT INTO app_settings(key,value) VALUES(?,?) ON CONFLICT(key) DO UPDATE SET value=excluded.value",
		"active_library", lib.Name,
	)
	log.Printf("[DB] Active library: %s", lib.Name)
	return nil
}

// NewLibraryDB creates a fresh SQLite DB at path and migrates the Entry schema.
func NewLibraryDB(path string) error {
	db, err := openSQLite(path)
	if err != nil {
		return err
	}
	return db.AutoMigrate(&models.Entry{})
}

// NewLibraryDBReadOnly opens an existing SQLite DB read-only (for counting etc).
func NewLibraryDBReadOnly(path string) (*gorm.DB, error) {
	return openSQLite(path + "?mode=ro")
}

// GetSettings returns the global settings DB (AppSetting + Library tables).
func GetSettings() *gorm.DB {
	mu.RLock()
	defer mu.RUnlock()
	return settingsDB
}

// Get returns the active knowledge library DB.
func Get() *gorm.DB {
	mu.RLock()
	defer mu.RUnlock()
	return activeLib
}

// GetActiveLibName returns the display name of the currently open library.
func GetActiveLibName() string {
	mu.RLock()
	defer mu.RUnlock()
	return activeLibNm
}

// IsReady reports whether both the settings DB and an active library are open.
func IsReady() bool {
	mu.RLock()
	defer mu.RUnlock()
	return settingsDB != nil && activeLib != nil
}

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

func openSQLite(path string) (*gorm.DB, error) {
	return gorm.Open(sqlite.Open(path), &gorm.Config{
		Logger: logger.Default.LogMode(logger.Warn),
	})
}

func appDataDir() (string, error) {
	dir, err := os.UserConfigDir()
	if err != nil {
		return "", fmt.Errorf("user config dir: %w", err)
	}
	return filepath.Join(dir, "AI-Expert-Sidebar"), nil
}