// Package store 负责 SQLite 连接、迁移与全部数据读写。
package store

import (
	"database/sql"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	_ "modernc.org/sqlite"

	"daili/internal/domain"
)

// 常见错误
var (
	ErrDuplicate = errors.New("记录已存在")
	ErrNotFound  = errors.New("记录不存在")
)

// DB 是数据库句柄。
type DB struct {
	sql  *sql.DB
	Path string

	// BackupPath 由配置文件指定；为空时回落到数据库同级的 backup/ 目录。
	BackupPath string
}

// Open 打开或创建数据库文件。
//
// 采用 DELETE 回滚日志模式而不是 WAL：这样全部数据始终在 daili.db 这一个文件里，
// 运行中不会产生 -wal/-shm 旁路文件，用户复制一个 daili.db 就能无损迁移；
// 删掉 daili.db 也就等于清空全部数据。
func Open(path string) (*DB, error) {
	if abs, err := filepath.Abs(path); err == nil {
		path = abs
	}
	if dir := filepath.Dir(path); dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return nil, fmt.Errorf("创建数据目录失败: %w", err)
		}
	}
	// 数据库文件不存在（用户删除 = 重置）时，清掉可能是旧版本残留的旁路文件，
	// 避免一个孤立的 -wal 干扰新建的库。
	if _, statErr := os.Stat(path); errors.Is(statErr, os.ErrNotExist) {
		_ = os.Remove(path + "-wal")
		_ = os.Remove(path + "-shm")
	}
	dsn := strings.ReplaceAll(path, "\\", "/") +
		"?_pragma=busy_timeout(5000)&_pragma=journal_mode(DELETE)&_pragma=foreign_keys(ON)&_pragma=synchronous(FULL)"
	sqlDB, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, err
	}
	sqlDB.SetMaxOpenConns(1)
	sqlDB.SetMaxIdleConns(1)
	if err := sqlDB.Ping(); err != nil {
		sqlDB.Close()
		return nil, err
	}
	// 兜底确认：旧版本的 WAL 库在打开时会被自动 checkpoint 并切回 DELETE 模式
	var mode string
	if err := sqlDB.QueryRow("PRAGMA journal_mode").Scan(&mode); err == nil && !strings.EqualFold(mode, "delete") {
		sqlDB.Close()
		return nil, fmt.Errorf("数据库日志模式切换失败（当前 %s），请确认 daili.db 没有被其他程序占用", mode)
	}
	return &DB{sql: sqlDB, Path: path}, nil
}

// JournalMode 返回当前日志模式（正常应为 delete）。
func (db *DB) JournalMode() (string, error) {
	var mode string
	err := db.sql.QueryRow("PRAGMA journal_mode").Scan(&mode)
	return mode, err
}

// Close 关闭数据库。
func (db *DB) Close() error { return db.sql.Close() }

// SQL 暴露底层连接（供备份等使用）。
func (db *DB) SQL() *sql.DB { return db.sql }

func nowStamp() string { return time.Now().Format(domain.StampLayout) }

func (db *DB) withTx(fn func(*sql.Tx) error) error {
	tx, err := db.sql.Begin()
	if err != nil {
		return err
	}
	if err := fn(tx); err != nil {
		_ = tx.Rollback()
		return err
	}
	return tx.Commit()
}

func isUnique(err error) bool {
	return err != nil && strings.Contains(err.Error(), "UNIQUE constraint failed")
}

func normalizeUnit(u string) string {
	if u == domain.UnitCount {
		return domain.UnitCount
	}
	return domain.UnitDay
}

// Migrate 幂等建表。
func (db *DB) Migrate() error {
	for _, stmt := range schemaStatements {
		if _, err := db.sql.Exec(stmt); err != nil {
			return fmt.Errorf("迁移失败: %w\nSQL: %s", err, stmt)
		}
	}
	// 增量列：老库升级时补上（SQLite 没有 ADD COLUMN IF NOT EXISTS）
	if err := db.ensureColumn("packages", "calendar_separate",
		"ALTER TABLE packages ADD COLUMN calendar_separate INTEGER NOT NULL DEFAULT 0"); err != nil {
		return err
	}
	// v1.3：管理员颜色 + 客户归属打手
	if err := db.ensureColumn("users", "color",
		"ALTER TABLE users ADD COLUMN color TEXT NOT NULL DEFAULT ''"); err != nil {
		return err
	}
	if err := db.ensureColumn("customers", "assignee_id",
		"ALTER TABLE customers ADD COLUMN assignee_id INTEGER REFERENCES users(id)"); err != nil {
		return err
	}
	return nil
}

// ensureColumn 在列不存在时执行 ddl，保证迁移可重复执行。
func (db *DB) ensureColumn(table, column, ddl string) error {
	rows, err := db.sql.Query("PRAGMA table_info(" + table + ")")
	if err != nil {
		return fmt.Errorf("读取 %s 表结构失败: %w", table, err)
	}
	found := false
	for rows.Next() {
		var cid int
		var name, ctype string
		var notnull, pk int
		var dflt any
		if err := rows.Scan(&cid, &name, &ctype, &notnull, &dflt, &pk); err != nil {
			rows.Close()
			return err
		}
		if strings.EqualFold(name, column) {
			found = true
		}
	}
	rows.Close()
	if found {
		return nil
	}
	if _, err := db.sql.Exec(ddl); err != nil {
		return fmt.Errorf("迁移失败（%s.%s）: %w", table, column, err)
	}
	return nil
}

var schemaStatements = []string{
	`CREATE TABLE IF NOT EXISTS users (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		username TEXT NOT NULL UNIQUE,
		display_name TEXT NOT NULL DEFAULT '',
		password_hash TEXT NOT NULL,
		is_active INTEGER NOT NULL DEFAULT 1,
		color TEXT NOT NULL DEFAULT '',
		created_at TEXT NOT NULL,
		last_login_at TEXT
	)`,
	`CREATE TABLE IF NOT EXISTS sessions (
		token TEXT PRIMARY KEY,
		user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
		created_at TEXT NOT NULL,
		expires_at TEXT NOT NULL,
		ip TEXT
	)`,
	`CREATE TABLE IF NOT EXISTS packages (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		name TEXT NOT NULL,
		unit TEXT NOT NULL CHECK (unit IN ('day','count')),
		default_amount INTEGER NOT NULL DEFAULT 30,
		price_cents INTEGER,
		color TEXT NOT NULL DEFAULT '#2F5D50',
		note TEXT NOT NULL DEFAULT '',
		archived INTEGER NOT NULL DEFAULT 0,
		sort_order INTEGER NOT NULL DEFAULT 0,
		calendar_separate INTEGER NOT NULL DEFAULT 0,
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL
	)`,
	`CREATE TABLE IF NOT EXISTS customers (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		tail TEXT NOT NULL,
		name TEXT NOT NULL,
		game_name TEXT NOT NULL DEFAULT '',
		game_server TEXT NOT NULL DEFAULT '',
		contact TEXT NOT NULL DEFAULT '',
		tags TEXT NOT NULL DEFAULT '',
		source TEXT NOT NULL DEFAULT '',
		note TEXT NOT NULL DEFAULT '',
		assignee_id INTEGER REFERENCES users(id),
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL,
		UNIQUE (tail, name)
	)`,
	`CREATE TABLE IF NOT EXISTS subscriptions (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		customer_id INTEGER NOT NULL REFERENCES customers(id) ON DELETE CASCADE,
		package_id INTEGER NOT NULL REFERENCES packages(id),
		unit TEXT NOT NULL CHECK (unit IN ('day','count')),
		status TEXT NOT NULL DEFAULT 'active' CHECK (status IN ('active','paused','closed')),
		start_date TEXT NOT NULL,
		end_date TEXT,
		total_count INTEGER NOT NULL DEFAULT 0,
		used_count INTEGER NOT NULL DEFAULT 0,
		note TEXT NOT NULL DEFAULT '',
		created_by INTEGER REFERENCES users(id),
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL,
		closed_at TEXT,
		UNIQUE (customer_id, package_id)
	)`,
	`CREATE TABLE IF NOT EXISTS sub_pauses (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		sub_id INTEGER NOT NULL REFERENCES subscriptions(id) ON DELETE CASCADE,
		start_at TEXT NOT NULL,
		end_at TEXT
	)`,
	`CREATE TABLE IF NOT EXISTS sub_adjustments (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		sub_id INTEGER NOT NULL REFERENCES subscriptions(id) ON DELETE CASCADE,
		kind TEXT NOT NULL,
		base_date TEXT,
		old_end_date TEXT,
		new_end_date TEXT,
		days_added INTEGER NOT NULL DEFAULT 0,
		count_added INTEGER NOT NULL DEFAULT 0,
		old_total INTEGER NOT NULL DEFAULT 0,
		new_total INTEGER NOT NULL DEFAULT 0,
		note TEXT NOT NULL DEFAULT '',
		operator_id INTEGER REFERENCES users(id),
		created_at TEXT NOT NULL
	)`,
	`CREATE TABLE IF NOT EXISTS checkins (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		sub_id INTEGER NOT NULL REFERENCES subscriptions(id) ON DELETE CASCADE,
		service_date TEXT NOT NULL,
		status TEXT NOT NULL CHECK (status IN ('done','skipped')),
		note TEXT NOT NULL DEFAULT '',
		operator_id INTEGER REFERENCES users(id),
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL,
		UNIQUE (sub_id, service_date)
	)`,
	`CREATE TABLE IF NOT EXISTS op_logs (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		operator_id INTEGER REFERENCES users(id),
		operator_name TEXT NOT NULL DEFAULT '',
		action TEXT NOT NULL,
		entity TEXT NOT NULL DEFAULT '',
		entity_id INTEGER,
		summary TEXT NOT NULL DEFAULT '',
		detail TEXT NOT NULL DEFAULT '',
		ip TEXT NOT NULL DEFAULT '',
		created_at TEXT NOT NULL
	)`,
	`CREATE TABLE IF NOT EXISTS task_flags (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		sub_id INTEGER NOT NULL REFERENCES subscriptions(id) ON DELETE CASCADE,
		service_date TEXT NOT NULL,
		urgent INTEGER NOT NULL DEFAULT 0,
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL,
		UNIQUE (sub_id, service_date)
	)`,
	`CREATE INDEX IF NOT EXISTS idx_task_flags_date ON task_flags(service_date)`,
	`CREATE TABLE IF NOT EXISTS settings (
		key TEXT PRIMARY KEY,
		value TEXT NOT NULL
	)`,
	`CREATE INDEX IF NOT EXISTS idx_sub_status_end ON subscriptions(status, end_date)`,
	`CREATE INDEX IF NOT EXISTS idx_sub_customer ON subscriptions(customer_id)`,
	`CREATE INDEX IF NOT EXISTS idx_sub_package ON subscriptions(package_id)`,
	`CREATE INDEX IF NOT EXISTS idx_cust_tail ON customers(tail)`,
	`CREATE INDEX IF NOT EXISTS idx_adj_sub ON sub_adjustments(sub_id, created_at)`,
	`CREATE INDEX IF NOT EXISTS idx_ci_date ON checkins(service_date)`,
	`CREATE INDEX IF NOT EXISTS idx_ci_sub ON checkins(sub_id, service_date)`,
	`CREATE INDEX IF NOT EXISTS idx_pause_sub ON sub_pauses(sub_id)`,
	`CREATE INDEX IF NOT EXISTS idx_log_created ON op_logs(created_at)`,
}

// ---------- 设置 ----------

// Setting 读取设置，缺失时返回默认值。
func (db *DB) Setting(key, def string) string {
	var v string
	err := db.sql.QueryRow(`SELECT value FROM settings WHERE key=?`, key).Scan(&v)
	if err != nil || v == "" {
		return def
	}
	return v
}

// SetSetting 写入设置。
func (db *DB) SetSetting(key, value string) error {
	_, err := db.sql.Exec(`INSERT INTO settings(key,value) VALUES(?,?)
		ON CONFLICT(key) DO UPDATE SET value=excluded.value`, key, value)
	return err
}