package db

import (
	"database/sql"
	"os"
	"path/filepath"
	"time"

	_ "modernc.org/sqlite"

	"github.com/google/uuid"
)

func OpenSQLite(path string) (*sql.DB, error) {
	dir := filepath.Dir(path)
	if dir != "." {
		_ = os.MkdirAll(dir, 0o755)
	}
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, err
	}
	db.SetMaxOpenConns(1)
	db.SetConnMaxLifetime(10 * time.Minute)
	if err := db.Ping(); err != nil {
		return nil, err
	}
	return db, nil
}

func MigrateSQLite(db *sql.DB) error {
	stmts := []string{
		`CREATE TABLE IF NOT EXISTS users (
      id TEXT PRIMARY KEY,
      email TEXT NOT NULL UNIQUE,
      password_hash TEXT NOT NULL,
      name TEXT NOT NULL DEFAULT '',
      module_key TEXT NOT NULL DEFAULT 'shop',
      experience_level TEXT NOT NULL DEFAULT 'beginner',
      onboarding_completed INTEGER NOT NULL DEFAULT 0,
      created_at TEXT NOT NULL
    );`,
		`CREATE TABLE IF NOT EXISTS user_databases (
      id TEXT PRIMARY KEY,
      user_id TEXT NOT NULL,
      name TEXT NOT NULL,
      source TEXT NOT NULL,
      schema_name TEXT NOT NULL,
      is_active INTEGER NOT NULL DEFAULT 0,
      created_at TEXT NOT NULL
    );`,
		`CREATE INDEX IF NOT EXISTS idx_user_databases_user_id ON user_databases(user_id);`,
		`CREATE TABLE IF NOT EXISTS exercises (
      id TEXT PRIMARY KEY,
      title TEXT NOT NULL,
      level TEXT NOT NULL,
      prompt TEXT NOT NULL,
      answer_sql TEXT NOT NULL,
      database_key TEXT NOT NULL,
      created_at TEXT NOT NULL
    );`,
		`CREATE INDEX IF NOT EXISTS idx_exercises_level ON exercises(level);`,
		`CREATE TABLE IF NOT EXISTS progress (
      id TEXT PRIMARY KEY,
      user_id TEXT NOT NULL,
      exercise_id TEXT NOT NULL,
      draft_sql TEXT NOT NULL DEFAULT '',
      is_solved INTEGER NOT NULL DEFAULT 0,
      updated_at TEXT NOT NULL
    );`,
		`CREATE UNIQUE INDEX IF NOT EXISTS uniq_progress_user_exercise ON progress(user_id, exercise_id);`,
	}

	for _, s := range stmts {
		if _, err := db.Exec(s); err != nil {
			return err
		}
	}
	return nil
}

func SeedSQLite(db *sql.DB) error {
	var cnt int
	if err := db.QueryRow(`SELECT COUNT(1) FROM exercises`).Scan(&cnt); err != nil {
		return err
	}
	if cnt > 0 {
		return nil
	}

	now := time.Now().UTC().Format(time.RFC3339)
	seed := []struct {
		Title       string
		Level       string
		Prompt      string
		AnswerSQL   string
		DatabaseKey string
	}{
		{
			Title:       "新手 1：查询所有商品名称与价格",
			Level:       "beginner",
			Prompt:      "在电商库中查询 products 表，返回 name 与 price 两列。",
			AnswerSQL:   "SELECT name, price FROM products ORDER BY id;",
			DatabaseKey: "shop",
		},
		{
			Title:       "新手 2：筛选价格大于 100 的商品",
			Level:       "beginner",
			Prompt:      "在电商库中查询 price > 100 的商品，返回 id, name, price，并按 price 从高到低排序。",
			AnswerSQL:   "SELECT id, name, price FROM products WHERE price > 100 ORDER BY price DESC, id ASC;",
			DatabaseKey: "shop",
		},
		{
			Title:       "一般 1：统计每个用户的订单数",
			Level:       "normal",
			Prompt:      "在电商库中统计每个用户的订单数量，返回 user_id 与 order_count，并按 order_count 从高到低排序。",
			AnswerSQL:   "SELECT user_id, COUNT(*) AS order_count FROM orders GROUP BY user_id ORDER BY order_count DESC, user_id ASC;",
			DatabaseKey: "shop",
		},
		{
			Title:       "一般 2：查询每个订单的总金额",
			Level:       "normal",
			Prompt:      "在电商库中，计算每个订单的总金额（sum(quantity * unit_price)），返回 order_id 与 total_amount，按 order_id 排序。",
			AnswerSQL:   "SELECT order_id, SUM(quantity * unit_price) AS total_amount FROM order_items GROUP BY order_id ORDER BY order_id ASC;",
			DatabaseKey: "shop",
		},
		{
			Title:       "进阶 1：找出下单金额最高的用户",
			Level:       "advanced",
			Prompt:      "在电商库中，计算每个用户的下单总金额，找出总金额最高的用户，返回 user_id 与 total_amount。",
			AnswerSQL:   "SELECT o.user_id, SUM(oi.quantity * oi.unit_price) AS total_amount FROM orders o JOIN order_items oi ON oi.order_id = o.id GROUP BY o.user_id ORDER BY total_amount DESC, o.user_id ASC LIMIT 1;",
			DatabaseKey: "shop",
		},
		{
			Title:       "新手 3：查询所有员工姓名与部门",
			Level:       "beginner",
			Prompt:      "在人事库中查询 employees 与 departments，返回 employee_name 与 department_name，并按 employee_id 排序。",
			AnswerSQL:   "SELECT e.name AS employee_name, d.name AS department_name FROM employees e JOIN departments d ON d.id = e.department_id ORDER BY e.id ASC;",
			DatabaseKey: "hr",
		},
		{
			Title:       "一般 3：统计每个部门员工数",
			Level:       "normal",
			Prompt:      "在人事库中统计每个部门的员工数，返回 department_name 与 employee_count，按 employee_count 从高到低排序。",
			AnswerSQL:   "SELECT d.name AS department_name, COUNT(e.id) AS employee_count FROM departments d LEFT JOIN employees e ON e.department_id = d.id GROUP BY d.id ORDER BY employee_count DESC, d.id ASC;",
			DatabaseKey: "hr",
		},
		{
			Title:       "进阶 2：找出每个部门工资最高的员工",
			Level:       "advanced",
			Prompt:      "在人事库中，找出每个部门工资最高的员工，返回 department_name, employee_name, salary。",
			AnswerSQL:   "SELECT d.name AS department_name, e.name AS employee_name, e.salary FROM departments d JOIN employees e ON e.department_id = d.id WHERE e.salary = (SELECT MAX(salary) FROM employees e2 WHERE e2.department_id = d.id) ORDER BY d.id ASC, e.id ASC;",
			DatabaseKey: "hr",
		},
	}

	for _, s := range seed {
		id := uuid.NewString()
		if _, err := db.Exec(
			`INSERT INTO exercises (id, title, level, prompt, answer_sql, database_key, created_at) VALUES (?, ?, ?, ?, ?, ?, ?)`,
			id,
			s.Title,
			s.Level,
			s.Prompt,
			s.AnswerSQL,
			s.DatabaseKey,
			now,
		); err != nil {
			return err
		}
	}
	return nil
}