package store

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

// SetBackupDir 设置备份目录（来自配置文件）。
func (db *DB) SetBackupDir(dir string) { db.BackupPath = dir }

// BackupDir 返回备份目录。
func (db *DB) BackupDir() string {
	if db.BackupPath != "" {
		return db.BackupPath
	}
	return filepath.Join(filepath.Dir(db.Path), "backup")
}

// BackupDaily 当天首次调用时生成一份备份；已有今日备份则跳过。
// 空库（还没有客户）不生成备份，避免第一天的备份是空壳。
func (db *DB) BackupDaily(keep int) (string, error) {
	dir := db.BackupDir()
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", err
	}
	now := time.Now()
	prefix := "daili-" + now.Format("20060102") + "-"
	entries, err := os.ReadDir(dir)
	if err != nil {
		return "", err
	}
	for _, e := range entries {
		if strings.HasPrefix(e.Name(), prefix) {
			return "", nil
		}
	}
	if n, err := db.CustomerCount(); err != nil || n == 0 {
		return "", err
	}
	target := filepath.Join(dir, fmt.Sprintf("daili-%s.db", now.Format("20060102-150405")))
	return db.BackupTo(target, keep)
}

// BackupNow 立即生成一份备份。
func (db *DB) BackupNow(keep int) (string, error) {
	dir := db.BackupDir()
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", err
	}
	target := filepath.Join(dir, fmt.Sprintf("daili-%s.db", time.Now().Format("20060102-150405")))
	return db.BackupTo(target, keep)
}

// BackupTo 用 VACUUM INTO 生成一致性备份，并按保留份数清理。
func (db *DB) BackupTo(target string, keep int) (string, error) {
	abs, err := filepath.Abs(target)
	if err != nil {
		return "", err
	}
	if err := os.MkdirAll(filepath.Dir(abs), 0o755); err != nil {
		return "", fmt.Errorf("创建备份目录失败: %w", err)
	}
	if _, err := os.Stat(abs); err == nil {
		return abs, fmt.Errorf("备份文件已存在: %s", filepath.Base(abs))
	}
	escaped := strings.ReplaceAll(strings.ReplaceAll(abs, "\\", "/"), "'", "''")
	if _, err := db.sql.Exec("VACUUM INTO '" + escaped + "'"); err != nil {
		return "", err
	}
	if keep > 0 {
		_ = db.pruneBackups(keep)
	}
	return abs, nil
}

// ListBackups 列出备份（新→旧）。
func (db *DB) ListBackups() ([]string, error) {
	dir := db.BackupDir()
	entries, err := os.ReadDir(dir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}
	var out []string
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".db") {
			out = append(out, e.Name())
		}
	}
	sort.Sort(sort.Reverse(sort.StringSlice(out)))
	return out, nil
}

func (db *DB) pruneBackups(keep int) error {
	list, err := db.ListBackups()
	if err != nil {
		return err
	}
	if len(list) <= keep {
		return nil
	}
	dir := db.BackupDir()
	for _, name := range list[keep:] {
		_ = os.Remove(filepath.Join(dir, name))
	}
	return nil
}