package repository

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"database/sql"
	"fmt"
	"log"
	"net"
	"os"
	"strings"
	"time"

	"github.com/go-sql-driver/mysql"

	"cmautobuy/admin/config"
	"cmautobuy/admin/model"
	"cmautobuy/admin/spec"
)

const mysqlSchemaVersion = 5

// OpenMySQL 打开生产 MySQL 8 数据库。错误信息绝不包含完整 DSN 或密码。
func OpenMySQL(cfg config.DatabaseConfig) (*sql.DB, error) {
	driverConfig, err := newMySQLDriverConfig(cfg)
	if err != nil {
		return nil, err
	}
	connector, err := mysql.NewConnector(driverConfig)
	if err != nil {
		return nil, fmt.Errorf("准备 MySQL 连接失败: %w", err)
	}
	db := sql.OpenDB(connector)

	db.SetMaxOpenConns(10)
	db.SetMaxIdleConns(10)
	db.SetConnMaxLifetime(3 * time.Minute)
	db.SetConnMaxIdleTime(time.Minute)

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := db.PingContext(ctx); err != nil {
		db.Close()
		return nil, fmt.Errorf("连接 MySQL 失败，请检查服务、库名、config.yaml、环境变量和 TLS 配置: %w", err)
	}
	if err := CheckMySQLServer(db, cfg.Name); err != nil {
		db.Close()
		return nil, err
	}
	return db, nil
}

// newMySQLDriverConfig 只负责把业务配置转换成驱动配置，方便单元测试在不连接
// 数据库的情况下核对 TLS 是否真的开启。
func newMySQLDriverConfig(cfg config.DatabaseConfig) (*mysql.Config, error) {
	driverConfig := mysql.NewConfig()
	driverConfig.User = cfg.User
	driverConfig.Passwd = cfg.Password
	driverConfig.Net = "tcp"
	driverConfig.Addr = net.JoinHostPort(cfg.Host, cfg.Port)
	driverConfig.DBName = cfg.Name
	driverConfig.Collation = "utf8mb4_0900_ai_ci"
	driverConfig.Loc = time.UTC
	driverConfig.Timeout = 5 * time.Second
	driverConfig.ReadTimeout = 30 * time.Second
	driverConfig.WriteTimeout = 30 * time.Second
	driverConfig.RejectReadOnly = true
	// 业务层用 RowsAffected 判断目标行是否存在；重复写入相同值也应算匹配到。
	driverConfig.ClientFoundRows = true
	driverConfig.Params = map[string]string{
		"time_zone": "'+00:00'",
		"sql_mode":  "'STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'",
	}

	if cfg.TLSMode == config.DatabaseTLSVerifyCA {
		tlsConfig, err := loadMySQLTLSConfig(cfg.TLSCA)
		if err != nil {
			return nil, err
		}
		driverConfig.TLS = tlsConfig
	}
	return driverConfig, nil
}

// loadMySQLTLSConfig 加载服务器专属 CA，并验证服务端证书确实由它签发。
// MySQL 自动生成的服务端证书没有 SAN，Go 无法做 IP/域名匹配；这里显式跳过
// 内置主机名检查，但用 VerifyConnection 恢复证书链校验，不能退回明文连接。
func loadMySQLTLSConfig(caPath string) (*tls.Config, error) {
	pemData, err := os.ReadFile(caPath)
	if err != nil {
		return nil, fmt.Errorf("读取 MySQL TLS CA 文件 %s 失败: %w", caPath, err)
	}
	roots := x509.NewCertPool()
	if !roots.AppendCertsFromPEM(pemData) {
		return nil, fmt.Errorf("解析 MySQL TLS CA 文件 %s 失败: 文件中没有有效 PEM 证书", caPath)
	}

	return &tls.Config{
		MinVersion:         tls.VersionTLS12,
		InsecureSkipVerify: true, // 主机名检查由下面的服务器专属 CA 链校验替代。
		VerifyConnection: func(state tls.ConnectionState) error {
			if len(state.PeerCertificates) == 0 {
				return fmt.Errorf("验证 MySQL TLS 证书失败: 服务端没有提供证书")
			}
			intermediates := x509.NewCertPool()
			for _, certificate := range state.PeerCertificates[1:] {
				intermediates.AddCert(certificate)
			}
			_, err := state.PeerCertificates[0].Verify(x509.VerifyOptions{
				Roots:         roots,
				Intermediates: intermediates,
				KeyUsages:     []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
			})
			if err != nil {
				return fmt.Errorf("验证 MySQL TLS 证书链失败: %w", err)
			}
			return nil
		},
	}, nil
}

// CheckMySQLServer 拒绝错误版本、错误库、非 UTC 或非 utf8mb4 的连接。
func CheckMySQLServer(db *sql.DB, expectedDatabase string) error {
	var version, databaseName, timeZone, charset, collation string
	if err := db.QueryRow(`SELECT VERSION(), DATABASE(), @@session.time_zone,
		@@character_set_connection, @@collation_connection`).Scan(
		&version, &databaseName, &timeZone, &charset, &collation); err != nil {
		return fmt.Errorf("读取 MySQL 运行参数失败: %w", err)
	}
	if !strings.HasPrefix(version, "8.") {
		return fmt.Errorf("MySQL 版本不兼容：需要 8.x，实际 %s", version)
	}
	if databaseName != expectedDatabase {
		return fmt.Errorf("连接到了错误的 MySQL 数据库：期望 %s，实际 %s", expectedDatabase, databaseName)
	}
	if timeZone != "+00:00" {
		return fmt.Errorf("MySQL 会话时区必须是 +00:00，实际 %s", timeZone)
	}
	if charset != "utf8mb4" || !strings.HasPrefix(collation, "utf8mb4_") {
		return fmt.Errorf("MySQL 连接字符集必须是 utf8mb4，实际 %s/%s", charset, collation)
	}
	return nil
}

// mysqlSchemaV1 是当前 SQLite v8 最终业务结构在 MySQL 8 上的等价定义。
// 每条 CREATE TABLE 都可重复执行；全部完成并通过自检后才记录版本。
var mysqlSchemaV1 = []string{
	`CREATE TABLE IF NOT EXISTS shopee_products (
		goods_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		title TEXT NOT NULL,
		shopee_status VARCHAR(191),
		main_sku_code VARCHAR(191),
		pdd_goods_url TEXT,
		pdd_goods_id VARCHAR(191) COLLATE utf8mb4_bin,
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL,
		KEY idx_shopee_products_pdd (pdd_goods_id)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS shopee_skus (
		sku_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		spec_raw TEXT NOT NULL,
		color TEXT,
		size TEXT,
		advice TEXT,
		parse_ok TINYINT NOT NULL DEFAULT 0,
		sku_code VARCHAR(191),
		is_manual TINYINT NOT NULL DEFAULT 0,
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL,
		KEY idx_shopee_skus_goods (goods_id),
		KEY idx_shopee_skus_parse (parse_ok),
		CONSTRAINT fk_shopee_skus_product FOREIGN KEY (goods_id)
			REFERENCES shopee_products(goods_id) ON DELETE CASCADE,
		CHECK (parse_ok IN (0, 1)),
		CHECK (is_manual IN (0, 1))
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS pdd_products (
		id BIGINT PRIMARY KEY AUTO_INCREMENT,
		goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL UNIQUE,
		url TEXT NOT NULL,
		title TEXT,
		shop_name TEXT,
		skus_json LONGTEXT,
		collect_status VARCHAR(20) NOT NULL DEFAULT 'pending',
		collect_msg TEXT,
		artifact_ref TEXT,
		collected_at VARCHAR(35),
		deleted_at VARCHAR(35),
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL,
		KEY idx_pdd_products_status (collect_status),
		CHECK (collect_status IN ('pending', 'collecting', 'collected', 'failed'))
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS syb_orders (
		syb_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		order_no VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		title TEXT,
		shopee_goods_id VARCHAR(191) COLLATE utf8mb4_bin,
		shopee_sku_id VARCHAR(191) COLLATE utf8mb4_bin,
		product_spec TEXT,
		quantity BIGINT NOT NULL,
		price_twd_cent BIGINT,
		image_url TEXT,
		syb_data LONGTEXT NOT NULL DEFAULT ('{}'),
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL,
		KEY idx_syb_orders_order (order_no),
		KEY idx_syb_orders_goods (shopee_goods_id),
		KEY idx_syb_orders_list (updated_at DESC, syb_id DESC),
		CHECK (quantity > 0),
		CHECK (price_twd_cent IS NULL OR price_twd_cent >= 0)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS sku_mappings (
		shopee_sku_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		pdd_goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		pdd_option_key VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		pdd_options LONGTEXT NOT NULL,
		goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		mapped_at VARCHAR(35) NOT NULL,
		mapped_by VARCHAR(191),
		PRIMARY KEY (shopee_sku_id, pdd_goods_id),
		KEY idx_sku_mappings_goods (goods_id),
		KEY idx_sku_mappings_pdd (pdd_goods_id),
		CONSTRAINT fk_sku_mappings_sku FOREIGN KEY (shopee_sku_id)
			REFERENCES shopee_skus(sku_id) ON DELETE CASCADE
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS tasks (
		task_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		task_type VARCHAR(20) NOT NULL,
		status VARCHAR(20) NOT NULL DEFAULT 'pending',
		version BIGINT NOT NULL DEFAULT 1,
		priority BIGINT NOT NULL DEFAULT 0,
		assigned_client VARCHAR(191) COLLATE utf8mb4_bin,
		claimed_at VARCHAR(35),
		syb_id VARCHAR(191) COLLATE utf8mb4_bin,
		order_no VARCHAR(191) COLLATE utf8mb4_bin,
		goods_id VARCHAR(191) COLLATE utf8mb4_bin,
		shopee_sku_id VARCHAR(191) COLLATE utf8mb4_bin,
		pdd_goods_url TEXT NOT NULL,
		pdd_goods_id VARCHAR(191) COLLATE utf8mb4_bin,
		pdd_options LONGTEXT,
		quantity BIGINT,
		max_price_cent BIGINT,
		result_data LONGTEXT,
		error_code VARCHAR(191),
		error_message TEXT,
		finished_at VARCHAR(35),
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL,
		KEY idx_tasks_claim (assigned_client, status, priority DESC, created_at),
		KEY idx_tasks_list (updated_at DESC, task_id DESC),
		KEY idx_tasks_order (order_no),
		CHECK (task_type IN ('collect', 'purchase')),
		CHECK (status IN ('pending', 'assigned', 'claimed', 'succeeded', 'manual_review', 'failed', 'cancelled')),
		CHECK (version > 0),
		CHECK (quantity IS NULL OR quantity > 0),
		CHECK (max_price_cent IS NULL OR max_price_cent > 0)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS clients (
		client_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		name TEXT,
		device_address TEXT,
		platform VARCHAR(191),
		pdd_package VARCHAR(191),
		capabilities LONGTEXT,
		last_seen_at VARCHAR(35) NOT NULL,
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS idempotency_keys (
		` + "`key`" + ` VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		request_hash VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		response_body LONGTEXT NOT NULL,
		created_at VARCHAR(35) NOT NULL
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS task_claims (
		task_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		client_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		claimed_at VARCHAR(35) NOT NULL,
		PRIMARY KEY (task_id, client_id),
		KEY idx_task_claims_client (client_id)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS syb_session (
		username VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		cookies LONGTEXT NOT NULL,
		expires_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS syb_sync_state (
		id TINYINT PRIMARY KEY,
		last_synced_at VARCHAR(35),
		updated_at VARCHAR(35) NOT NULL,
		CHECK (id = 1)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS users (
		user_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		username VARCHAR(191) COLLATE utf8mb4_0900_ai_ci NOT NULL UNIQUE,
		password_hash VARCHAR(255) COLLATE utf8mb4_bin NOT NULL,
		role VARCHAR(20) NOT NULL,
		status VARCHAR(20) NOT NULL,
		last_login_at VARCHAR(35),
		password_changed_at VARCHAR(35) NOT NULL,
		created_at VARCHAR(35) NOT NULL,
		updated_at VARCHAR(35) NOT NULL,
		CHECK (role IN ('admin', 'purchaser')),
		CHECK (status IN ('active', 'disabled'))
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS web_sessions (
		session_hash VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		user_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		expires_at VARCHAR(35) NOT NULL,
		created_at VARCHAR(35) NOT NULL,
		last_seen_at VARCHAR(35) NOT NULL,
		KEY idx_web_sessions_user (user_id),
		KEY idx_web_sessions_expiry (expires_at),
		CONSTRAINT fk_web_sessions_user FOREIGN KEY (user_id) REFERENCES users(user_id)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS client_user_assignments (
		assignment_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		client_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		user_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		started_at VARCHAR(35) NOT NULL,
		ended_at VARCHAR(35),
		assigned_by_user_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		ended_by_user_id VARCHAR(191) COLLATE utf8mb4_bin,
		end_reason VARCHAR(20),
		current_client_id VARCHAR(191) COLLATE utf8mb4_bin
			GENERATED ALWAYS AS (IF(ended_at IS NULL, client_id, NULL)) STORED,
		UNIQUE KEY idx_client_assignment_current (current_client_id),
		KEY idx_client_assignment_user (user_id, ended_at, client_id),
		KEY idx_client_assignment_history (client_id, started_at DESC),
		CONSTRAINT fk_client_assignment_user FOREIGN KEY (user_id) REFERENCES users(user_id),
		CONSTRAINT fk_client_assignment_assigned_by FOREIGN KEY (assigned_by_user_id) REFERENCES users(user_id),
		CONSTRAINT fk_client_assignment_ended_by FOREIGN KEY (ended_by_user_id) REFERENCES users(user_id),
		CHECK (end_reason IS NULL OR end_reason IN ('unbind', 'transfer')),
		CHECK ((ended_at IS NULL AND ended_by_user_id IS NULL AND end_reason IS NULL)
			OR (ended_at IS NOT NULL AND ended_by_user_id IS NOT NULL AND end_reason IS NOT NULL))
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`CREATE TABLE IF NOT EXISTS syb_sync_runs (
		run_id VARCHAR(191) COLLATE utf8mb4_bin PRIMARY KEY,
		user_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
		date_from VARCHAR(10) NOT NULL,
		date_to VARCHAR(10) NOT NULL,
		status VARCHAR(20) NOT NULL,
		stock_count BIGINT NOT NULL DEFAULT 0,
		detail_count BIGINT NOT NULL DEFAULT 0,
		created_count BIGINT NOT NULL DEFAULT 0,
		updated_count BIGINT NOT NULL DEFAULT 0,
		skipped_count BIGINT NOT NULL DEFAULT 0,
		error_message TEXT,
		cursor_advanced TINYINT NOT NULL DEFAULT 0,
		started_at VARCHAR(35) NOT NULL,
		finished_at VARCHAR(35),
		KEY idx_syb_sync_runs_started (started_at DESC, run_id DESC),
		CONSTRAINT fk_syb_sync_runs_user FOREIGN KEY (user_id) REFERENCES users(user_id),
		CHECK (status IN ('running', 'succeeded', 'failed', 'interrupted')),
		CHECK (cursor_advanced IN (0, 1)),
		CHECK ((status = 'running' AND finished_at IS NULL)
			OR (status <> 'running' AND finished_at IS NOT NULL))
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
}

// mysqlSchemaV2 增加首位管理员初始化的并发哨兵。MySQL DDL 会隐式提交，
// 因此每条语句都必须可重放，并在全部成功后才记录版本。
var mysqlSchemaV2 = []string{
	`CREATE TABLE IF NOT EXISTS admin_initialization_lock (
		id TINYINT PRIMARY KEY,
		CHECK (id = 1)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`,
	`INSERT INTO admin_initialization_lock (id) VALUES (1)
	 ON DUPLICATE KEY UPDATE id = VALUES(id)`,
}

const mysqlSchemaV3SpecMappings = `CREATE TABLE IF NOT EXISTS spec_mappings (
	shopee_goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	spec_key VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	pdd_goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	pdd_option_key VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	pdd_options LONGTEXT NOT NULL,
	spec_raw TEXT NOT NULL,
	mapped_at VARCHAR(35) NOT NULL,
	mapped_by VARCHAR(191),
	PRIMARY KEY (shopee_goods_id, spec_key, pdd_goods_id),
	KEY idx_spec_mappings_goods (shopee_goods_id),
	KEY idx_spec_mappings_pdd (pdd_goods_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`

const mysqlSchemaV4Decisions = `CREATE TABLE IF NOT EXISTS spec_mapping_decisions (
	id BIGINT AUTO_INCREMENT PRIMARY KEY,
	shopee_goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	spec_key VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	pdd_goods_id VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	rules_version VARCHAR(32) NOT NULL,
	suggested_option_key VARCHAR(191) COLLATE utf8mb4_bin,
	chosen_option_key VARCHAR(191) COLLATE utf8mb4_bin NOT NULL,
	accepted TINYINT NOT NULL,
	decided_by VARCHAR(191),
	decided_at VARCHAR(35) NOT NULL,
	CONSTRAINT chk_spec_mapping_decisions_accepted CHECK (accepted IN (0,1)),
	KEY idx_decisions_mapping (shopee_goods_id, spec_key, pdd_goods_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`

// MigrateMySQL 建立或升级 MySQL schema。生产迁移只能在这里追加新版本。
func MigrateMySQL(db *sql.DB) error {
	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		version INT PRIMARY KEY,
		applied_at VARCHAR(35) NOT NULL
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci`); err != nil {
		return fmt.Errorf("建立 MySQL 迁移版本表失败: %w", err)
	}
	var current int
	if err := db.QueryRow(`SELECT COALESCE(MAX(version), 0) FROM schema_migrations`).Scan(&current); err != nil {
		return fmt.Errorf("读取 MySQL schema 版本失败: %w", err)
	}
	if current > mysqlSchemaVersion {
		return fmt.Errorf("MySQL schema 版本 %d 高于程序支持的 %d，请升级程序", current, mysqlSchemaVersion)
	}
	if current < 1 {
		for i, statement := range mysqlSchemaV1 {
			if _, err := db.Exec(statement); err != nil {
				return fmt.Errorf("执行 MySQL schema v1 第 %d 条失败: %w", i+1, err)
			}
		}
		if err := checkMySQLSchema(db, requiredTables); err != nil {
			return fmt.Errorf("MySQL schema v1 自检失败，未记录版本: %w", err)
		}
		if _, err := db.Exec(`INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)`,
			1, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			return fmt.Errorf("记录 MySQL schema v1 失败: %w", err)
		}
		current = 1
	}
	if current < 2 {
		for i, statement := range mysqlSchemaV2 {
			if _, err := db.Exec(statement); err != nil {
				return fmt.Errorf("执行 MySQL schema v2 第 %d 条失败: %w", i+1, err)
			}
		}
		mysqlRequiredTablesV2 := append(append([]string{}, requiredTables...), "admin_initialization_lock")
		if err := checkMySQLSchema(db, mysqlRequiredTablesV2); err != nil {
			return fmt.Errorf("MySQL schema v2 自检失败，未记录版本: %w", err)
		}
		if _, err := db.Exec(`INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)`,
			2, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			return fmt.Errorf("记录 MySQL schema v2 失败: %w", err)
		}
		current = 2
	}
	if current < 3 {
		if err := migrateMySQLV3(db); err != nil {
			return fmt.Errorf("执行 MySQL schema v3 失败: %w", err)
		}
		if err := checkMySQLSchemaV3(db); err != nil {
			return fmt.Errorf("MySQL schema v3 自检失败，未记录版本: %w", err)
		}
		if _, err := db.Exec(`INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)`,
			3, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			return fmt.Errorf("记录 MySQL schema v3 失败: %w", err)
		}
		current = 3
	}
	if current < 4 {
		if _, err := db.Exec(mysqlSchemaV4Decisions); err != nil {
			return fmt.Errorf("执行 MySQL schema v4 失败: %w", err)
		}
		if err := checkMySQLV4Shape(db); err != nil {
			return fmt.Errorf("MySQL schema v4 自检失败，未记录版本: %w", err)
		}
		if _, err := db.Exec(`INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)`, 4, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			return fmt.Errorf("记录 MySQL schema v4 失败: %w", err)
		}
		current = 4
	}
	if current < 5 {
		if err := migrateMySQLV5(db); err != nil {
			return fmt.Errorf("执行 MySQL schema v5 失败: %w", err)
		}
		if err := checkMySQLV5Shape(db); err != nil {
			return fmt.Errorf("MySQL schema v5 自检失败，未记录版本: %w", err)
		}
		if _, err := db.Exec(`INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)`, 5, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			return fmt.Errorf("记录 MySQL schema v5 失败: %w", err)
		}
	}
	return CheckMySQLSchema(db)
}

// migrateMySQLV5 给任务增加不可变执行模式和真实下单创建审计。
// 每条 DDL 都先检查存在性，MySQL 在任意一步隐式提交后都可以安全重放。
func migrateMySQLV5(db *sql.DB) error {
	columns := []struct {
		name string
		ddl  string
	}{
		{"execution_mode", `ALTER TABLE tasks ADD COLUMN execution_mode VARCHAR(16) COLLATE utf8mb4_bin NOT NULL DEFAULT 'dry_run' AFTER status`},
		{"live_confirmed_by", `ALTER TABLE tasks ADD COLUMN live_confirmed_by VARCHAR(191) COLLATE utf8mb4_bin NULL AFTER finished_at`},
		{"live_confirmed_at", `ALTER TABLE tasks ADD COLUMN live_confirmed_at VARCHAR(35) NULL AFTER live_confirmed_by`},
	}
	for _, column := range columns {
		exists, err := mysqlColumnExists(db, "tasks", column.name)
		if err != nil {
			return err
		}
		if !exists {
			if _, err := db.Exec(column.ddl); err != nil {
				return fmt.Errorf("增加 tasks.%s 失败: %w", column.name, err)
			}
		}
	}
	if _, err := db.Exec(`UPDATE tasks SET execution_mode='dry_run' WHERE execution_mode IS NULL OR execution_mode=''`); err != nil {
		return fmt.Errorf("回填任务执行模式失败: %w", err)
	}
	constraints := []struct {
		name string
		ddl  string
	}{
		{"chk_tasks_execution_mode", `ALTER TABLE tasks ADD CONSTRAINT chk_tasks_execution_mode CHECK (execution_mode IN ('dry_run','live'))`},
		{"chk_tasks_live_confirmation", `ALTER TABLE tasks ADD CONSTRAINT chk_tasks_live_confirmation CHECK ((execution_mode='dry_run' AND live_confirmed_by IS NULL AND live_confirmed_at IS NULL) OR (execution_mode='live' AND live_confirmed_by IS NOT NULL AND live_confirmed_by<>'' AND live_confirmed_at IS NOT NULL AND live_confirmed_at<>''))`},
	}
	for _, constraint := range constraints {
		exists, err := mysqlConstraintExists(db, "tasks", constraint.name)
		if err != nil {
			return err
		}
		if !exists {
			if _, err := db.Exec(constraint.ddl); err != nil {
				return fmt.Errorf("增加 tasks.%s 失败: %w", constraint.name, err)
			}
		}
	}
	indexExists, err := mysqlIndexExists(db, "tasks", "idx_tasks_claim_mode")
	if err != nil {
		return err
	}
	if !indexExists {
		if _, err := db.Exec(`ALTER TABLE tasks ADD INDEX idx_tasks_claim_mode (assigned_client, status, execution_mode, priority DESC, created_at)`); err != nil {
			return fmt.Errorf("增加任务模式领取索引失败: %w", err)
		}
	}
	return nil
}

func checkMySQLSchemaV3(db *sql.DB) error {
	tables := []string{"shopee_products", "shopee_skus", "pdd_products", "syb_orders", "spec_mappings", "tasks", "clients", "idempotency_keys", "task_claims", "syb_session", "syb_sync_state", "users", "web_sessions", "client_user_assignments", "syb_sync_runs", "admin_initialization_lock"}
	if err := checkMySQLSchema(db, tables); err != nil {
		return err
	}
	return checkMySQLV3Shape(db)
}

// migrateMySQLV3 把采购规格身份从蝦皮 SKU 改为顺运宝商品规格原文。
// 每一步都可重放：DDL 已提交但版本尚未记录时，再启动仍会收敛。
func migrateMySQLV3(db *sql.DB) error {
	if err := ensureMySQLV3Columns(db); err != nil {
		return err
	}
	if _, err := db.Exec(mysqlSchemaV3SpecMappings); err != nil {
		return fmt.Errorf("建立 spec_mappings 失败: %w", err)
	}
	if err := backfillSybSpecKeys(db); err != nil {
		return err
	}
	if err := ensureSybShopeeSkeletons(db); err != nil {
		return err
	}
	return convertLegacySKUMappings(db)
}

func ensureMySQLV3Columns(db *sql.DB) error {
	exists, err := mysqlColumnExists(db, "syb_orders", "spec_key")
	if err != nil {
		return err
	}
	if !exists {
		if _, err := db.Exec(`ALTER TABLE syb_orders ADD COLUMN spec_key VARCHAR(191) COLLATE utf8mb4_bin NULL AFTER product_spec`); err != nil {
			return fmt.Errorf("增加 syb_orders.spec_key 失败: %w", err)
		}
	} else if _, err := db.Exec(`ALTER TABLE syb_orders MODIFY COLUMN spec_key VARCHAR(191) COLLATE utf8mb4_bin NULL`); err != nil {
		return fmt.Errorf("校正 syb_orders.spec_key 结构失败: %w", err)
	}

	exists, err = mysqlColumnExists(db, "shopee_products", "source")
	if err != nil {
		return err
	}
	if !exists {
		if _, err := db.Exec(`ALTER TABLE shopee_products ADD COLUMN source VARCHAR(16) COLLATE utf8mb4_bin NOT NULL DEFAULT 'report' AFTER main_sku_code`); err != nil {
			return fmt.Errorf("增加 shopee_products.source 失败: %w", err)
		}
	} else {
		// 兼容“列已加但还是可空”的 DDL 中断点。先回填旧行，
		// 再收紧 NOT NULL，否则带 NULL 的存量数据会让 ALTER 失败。
		if _, err := db.Exec(`UPDATE shopee_products SET source='report' WHERE source IS NULL OR source=''`); err != nil {
			return fmt.Errorf("回填 shopee_products.source 失败: %w", err)
		}
		if _, err := db.Exec(`ALTER TABLE shopee_products MODIFY COLUMN source VARCHAR(16) COLLATE utf8mb4_bin NOT NULL DEFAULT 'report'`); err != nil {
			return fmt.Errorf("校正 shopee_products.source 结构失败: %w", err)
		}
	}

	constraintExists, err := mysqlConstraintExists(db, "shopee_products", "chk_shopee_products_source")
	if err != nil {
		return err
	}
	if !constraintExists {
		if _, err := db.Exec(`ALTER TABLE shopee_products ADD CONSTRAINT chk_shopee_products_source CHECK (source IN ('report','syb'))`); err != nil {
			return fmt.Errorf("增加 shopee_products.source CHECK 失败: %w", err)
		}
	}
	return nil
}

func mysqlColumnExists(db *sql.DB, table, column string) (bool, error) {
	var count int
	if err := db.QueryRow(`SELECT COUNT(*) FROM information_schema.columns
		WHERE table_schema=DATABASE() AND table_name=? AND column_name=?`, table, column).Scan(&count); err != nil {
		return false, fmt.Errorf("检查 MySQL 数据表 %s.%s 失败: %w", table, column, err)
	}
	return count == 1, nil
}

func mysqlConstraintExists(db *sql.DB, table, constraint string) (bool, error) {
	var count int
	if err := db.QueryRow(`SELECT COUNT(*) FROM information_schema.table_constraints
		WHERE constraint_schema=DATABASE() AND table_name=? AND constraint_name=?`, table, constraint).Scan(&count); err != nil {
		return false, fmt.Errorf("检查 MySQL 约束 %s.%s 失败: %w", table, constraint, err)
	}
	return count == 1, nil
}

func mysqlIndexExists(db *sql.DB, table, index string) (bool, error) {
	var count int
	if err := db.QueryRow(`SELECT COUNT(DISTINCT index_name) FROM information_schema.statistics
		WHERE table_schema=DATABASE() AND table_name=? AND index_name=?`, table, index).Scan(&count); err != nil {
		return false, fmt.Errorf("检查 MySQL 索引 %s.%s 失败: %w", table, index, err)
	}
	return count == 1, nil
}

func backfillSybSpecKeys(db *sql.DB) error {
	const batchSize = 500
	cursor := ""
	for {
		rows, err := db.Query(`SELECT syb_id, product_spec FROM syb_orders
			WHERE syb_id > ? AND spec_key IS NULL AND product_spec IS NOT NULL
			  AND TRIM(product_spec) <> '' ORDER BY syb_id LIMIT ?`, cursor, batchSize)
		if err != nil {
			return fmt.Errorf("读取待回填顺运宝规格失败: %w", err)
		}
		type item struct{ id, raw, key string }
		items := make([]item, 0, batchSize)
		for rows.Next() {
			var value item
			if err := rows.Scan(&value.id, &value.raw); err != nil {
				rows.Close()
				return fmt.Errorf("读取待回填顺运宝规格失败: %w", err)
			}
			value.key, err = spec.SpecKey(value.raw)
			if err != nil {
				rows.Close()
				return fmt.Errorf("顺运宝明细 %s 的规格不能生成身份键: %w", value.id, err)
			}
			items = append(items, value)
		}
		if err := rows.Close(); err != nil {
			return fmt.Errorf("关闭顺运宝规格回填结果失败: %w", err)
		}
		if len(items) == 0 {
			return nil
		}
		tx, err := db.Begin()
		if err != nil {
			return fmt.Errorf("开始顺运宝规格回填事务失败: %w", err)
		}
		for _, value := range items {
			if _, err := tx.Exec(`UPDATE syb_orders SET spec_key=? WHERE syb_id=? AND spec_key IS NULL`, value.key, value.id); err != nil {
				tx.Rollback()
				return fmt.Errorf("回填顺运宝明细 %s 的规格键失败: %w", value.id, err)
			}
		}
		if err := tx.Commit(); err != nil {
			return fmt.Errorf("提交顺运宝规格回填失败: %w", err)
		}
		cursor = items[len(items)-1].id
	}
}

func ensureSybShopeeSkeletons(db *sql.DB) error {
	now := model.NowISO()
	_, err := db.Exec(`INSERT INTO shopee_products
		(goods_id, title, source, created_at, updated_at)
		SELECT shopee_goods_id, MAX(COALESCE(title,'')), 'syb', ?, ?
		  FROM syb_orders
		 WHERE shopee_goods_id IS NOT NULL AND shopee_goods_id <> ''
		 GROUP BY shopee_goods_id
		ON DUPLICATE KEY UPDATE goods_id=VALUES(goods_id)`, now, now)
	if err != nil {
		return fmt.Errorf("按顺运宝数据补建蝦皮商品骨架失败: %w", err)
	}
	return nil
}

func convertLegacySKUMappings(db *sql.DB) error {
	exists, err := mysqlTableExists(db, "sku_mappings")
	if err != nil || !exists {
		return err
	}
	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS sku_mappings_v3_backup LIKE sku_mappings`); err != nil {
		return fmt.Errorf("建立旧规格映射备份表失败: %w", err)
	}
	if _, err := db.Exec(`INSERT IGNORE INTO sku_mappings_v3_backup SELECT * FROM sku_mappings`); err != nil {
		return fmt.Errorf("备份旧规格映射失败: %w", err)
	}

	rows, err := db.Query(`SELECT m.shopee_sku_id, m.pdd_goods_id, m.pdd_option_key,
		m.pdd_options, m.mapped_at, m.mapped_by, sk.goods_id, sk.spec_raw
		FROM sku_mappings m LEFT JOIN shopee_skus sk ON sk.sku_id=m.shopee_sku_id`)
	if err != nil {
		return fmt.Errorf("读取旧规格映射失败: %w", err)
	}
	type legacy struct {
		skuID, pddID, optionKey, options, mappedAt string
		mappedBy, goodsID, raw                     sql.NullString
	}
	var records []legacy
	for rows.Next() {
		var value legacy
		if err := rows.Scan(&value.skuID, &value.pddID, &value.optionKey, &value.options,
			&value.mappedAt, &value.mappedBy, &value.goodsID, &value.raw); err != nil {
			rows.Close()
			return fmt.Errorf("读取旧规格映射失败: %w", err)
		}
		records = append(records, value)
	}
	if err := rows.Close(); err != nil {
		return fmt.Errorf("关闭旧规格映射结果失败: %w", err)
	}

	matched, noCurrentMatch, unable := 0, 0, 0
	for _, value := range records {
		if !value.goodsID.Valid || !value.raw.Valid {
			unable++
			log.Printf("mysql_v3_mapping_unconvertible shopee_sku_id=%s pdd_goods_id=%s", value.skuID, value.pddID)
			continue
		}
		key, err := spec.SpecKey(value.raw.String)
		if err != nil {
			unable++
			log.Printf("mysql_v3_mapping_unconvertible shopee_sku_id=%s pdd_goods_id=%s reason=invalid_spec_key", value.skuID, value.pddID)
			continue
		}
		if err := UpsertSpecMapping(db, model.SpecMapping{
			ShopeeGoodsID: value.goodsID.String, SpecKey: key, SpecRaw: value.raw.String,
			PddGoodsID: value.pddID, PddOptionKey: value.optionKey, PddOptions: value.options,
			MappedAt: value.mappedAt, MappedBy: value.mappedBy.String,
		}); err != nil {
			return fmt.Errorf("转换旧规格映射 %s 失败: %w", value.skuID, err)
		}
		var hit int
		if err := db.QueryRow(`SELECT EXISTS(SELECT 1 FROM syb_orders WHERE shopee_goods_id=? AND spec_key=?)`,
			value.goodsID.String, key).Scan(&hit); err != nil {
			return fmt.Errorf("验证旧规格映射 %s 命中失败: %w", value.skuID, err)
		}
		if hit == 1 {
			matched++
		} else {
			noCurrentMatch++
			log.Printf("mysql_v3_mapping_no_current_hit shopee_sku_id=%s pdd_goods_id=%s", value.skuID, value.pddID)
		}
	}
	if matched+noCurrentMatch+unable != len(records) {
		return fmt.Errorf("旧规格映射迁移计数不守恒: 总数=%d 命中=%d 无命中=%d 无法转换=%d",
			len(records), matched, noCurrentMatch, unable)
	}
	log.Printf("mysql_v3_mapping_summary total=%d matched=%d no_current_hit=%d unconvertible=%d backup_table=sku_mappings_v3_backup",
		len(records), matched, noCurrentMatch, unable)
	if _, err := db.Exec(`DROP TABLE sku_mappings`); err != nil {
		return fmt.Errorf("删除已备份的旧规格映射表失败: %w", err)
	}
	return nil
}

func mysqlTableExists(db *sql.DB, table string) (bool, error) {
	var count int
	if err := db.QueryRow(`SELECT COUNT(*) FROM information_schema.tables
		WHERE table_schema=DATABASE() AND table_name=? AND table_type='BASE TABLE'`, table).Scan(&count); err != nil {
		return false, fmt.Errorf("检查 MySQL 数据表 %s 失败: %w", table, err)
	}
	return count == 1, nil
}

// CheckMySQLSchema 确认所有业务表、关键追加列和采购身份结构完整。
func CheckMySQLSchema(db *sql.DB) error {
	mysqlRequiredTables := []string{
		"shopee_products", "shopee_skus", "pdd_products", "syb_orders", "spec_mappings",
		"tasks", "clients", "idempotency_keys", "task_claims", "syb_session", "syb_sync_state",
		"users", "web_sessions", "client_user_assignments", "syb_sync_runs", "admin_initialization_lock",
		"spec_mapping_decisions",
	}
	if err := checkMySQLSchema(db, mysqlRequiredTables); err != nil {
		return err
	}
	if err := checkMySQLV3Shape(db); err != nil {
		return err
	}
	if err := checkMySQLV4Shape(db); err != nil {
		return err
	}
	return checkMySQLV5Shape(db)
}

func checkMySQLV5Shape(db *sql.DB) error {
	if err := checkMySQLVarcharColumn(db, "tasks", "execution_mode", 16, false, "utf8mb4_bin", "dry_run"); err != nil {
		return err
	}
	if err := checkMySQLVarcharColumn(db, "tasks", "live_confirmed_by", 191, true, "utf8mb4_bin", ""); err != nil {
		return err
	}
	if err := checkMySQLNullDefault(db, "tasks", "live_confirmed_by"); err != nil {
		return err
	}
	if err := checkMySQLVarcharColumn(db, "tasks", "live_confirmed_at", 35, true, "utf8mb4_0900_ai_ci", ""); err != nil {
		return err
	}
	if err := checkMySQLNullDefault(db, "tasks", "live_confirmed_at"); err != nil {
		return err
	}
	for _, check := range []struct {
		name     string
		required []string
	}{
		{"chk_tasks_execution_mode", []string{"execution_modein'dry_run','live'"}},
		{"chk_tasks_live_confirmation", []string{"execution_mode='dry_run'", "live_confirmed_byisnull", "live_confirmed_atisnull", "execution_mode='live'", "live_confirmed_byisnotnull", "live_confirmed_by<>''", "live_confirmed_atisnotnull", "live_confirmed_at<>''"}},
	} {
		var enforced, clause string
		if err := db.QueryRow(`SELECT tc.enforced,cc.check_clause FROM information_schema.table_constraints tc JOIN information_schema.check_constraints cc ON cc.constraint_schema=tc.constraint_schema AND cc.constraint_name=tc.constraint_name WHERE tc.constraint_schema=DATABASE() AND tc.table_name='tasks' AND tc.constraint_name=? AND tc.constraint_type='CHECK'`, check.name).Scan(&enforced, &clause); err != nil {
			return fmt.Errorf("任务 CHECK %s 缺失或不可读: %w", check.name, err)
		}
		normalized := strings.NewReplacer("`", "", " ", "", "(", "", ")", "", "_utf8mb4", "", `\`, "").Replace(strings.ToLower(clause))
		if enforced != "YES" {
			return fmt.Errorf("任务 CHECK %s 未启用", check.name)
		}
		for _, fragment := range check.required {
			if !strings.Contains(normalized, fragment) {
				return fmt.Errorf("任务 CHECK %s 表达式不正确", check.name)
			}
		}
	}
	var cols string
	if err := db.QueryRow(`SELECT GROUP_CONCAT(CONCAT(column_name,':',collation) ORDER BY seq_in_index) FROM information_schema.statistics WHERE table_schema=DATABASE() AND table_name='tasks' AND index_name='idx_tasks_claim_mode'`).Scan(&cols); err != nil || cols != "assigned_client:A,status:A,execution_mode:A,priority:D,created_at:A" {
		return fmt.Errorf("任务模式领取索引不正确")
	}
	return nil
}

func checkMySQLNullDefault(db *sql.DB, table, column string) error {
	var defaultValue sql.NullString
	if err := db.QueryRow(`SELECT column_default FROM information_schema.columns WHERE table_schema=DATABASE() AND table_name=? AND column_name=?`, table, column).Scan(&defaultValue); err != nil {
		return fmt.Errorf("检查 MySQL 列 %s.%s 默认值失败: %w", table, column, err)
	}
	if defaultValue.Valid {
		return fmt.Errorf("MySQL 列 %s.%s 默认值应为 NULL", table, column)
	}
	return nil
}

func checkMySQLV4Shape(db *sql.DB) error {
	for _, c := range []struct {
		name     string
		length   int64
		nullable bool
		coll     string
	}{
		{"shopee_goods_id", 191, false, "utf8mb4_bin"}, {"spec_key", 191, false, "utf8mb4_bin"}, {"pdd_goods_id", 191, false, "utf8mb4_bin"},
		{"rules_version", 32, false, "utf8mb4_0900_ai_ci"}, {"suggested_option_key", 191, true, "utf8mb4_bin"}, {"chosen_option_key", 191, false, "utf8mb4_bin"},
	} {
		if err := checkMySQLVarcharColumn(db, "spec_mapping_decisions", c.name, c.length, c.nullable, c.coll, ""); err != nil {
			return err
		}
	}
	var enforced, clause string
	if err := db.QueryRow(`SELECT tc.enforced,cc.check_clause FROM information_schema.table_constraints tc JOIN information_schema.check_constraints cc ON cc.constraint_schema=tc.constraint_schema AND cc.constraint_name=tc.constraint_name WHERE tc.constraint_schema=DATABASE() AND tc.table_name='spec_mapping_decisions' AND tc.constraint_name='chk_spec_mapping_decisions_accepted'`).Scan(&enforced, &clause); err != nil {
		return fmt.Errorf("审计 accepted CHECK 缺失: %w", err)
	}
	n := strings.NewReplacer("`", "", " ", "", "(", "", ")", "", "_utf8mb4", "", `\`, "").Replace(strings.ToLower(clause))
	if enforced != "YES" || n != "acceptedin0,1" {
		return fmt.Errorf("审计 accepted CHECK 不正确")
	}
	var cols string
	if err := db.QueryRow(`SELECT GROUP_CONCAT(column_name ORDER BY seq_in_index) FROM information_schema.statistics WHERE table_schema=DATABASE() AND table_name='spec_mapping_decisions' AND index_name='idx_decisions_mapping'`).Scan(&cols); err != nil || cols != "shopee_goods_id,spec_key,pdd_goods_id" {
		return fmt.Errorf("审计映射索引不正确")
	}
	return nil
}

func checkMySQLSchema(db *sql.DB, tables []string) error {
	rows, err := db.Query(`SELECT table_name FROM information_schema.tables
		WHERE table_schema = DATABASE() AND table_type = 'BASE TABLE'`)
	if err != nil {
		return fmt.Errorf("读取 MySQL 数据表清单失败: %w", err)
	}
	defer rows.Close()
	existing := map[string]bool{}
	for rows.Next() {
		var name string
		if err := rows.Scan(&name); err != nil {
			return fmt.Errorf("读取 MySQL 数据表清单失败: %w", err)
		}
		existing[name] = true
	}
	if err := rows.Err(); err != nil {
		return err
	}
	var missing []string
	for _, table := range tables {
		if !existing[table] {
			missing = append(missing, table)
		}
	}
	if len(missing) > 0 {
		return fmt.Errorf("MySQL schema 不完整，缺少表 %s", strings.Join(missing, "、"))
	}
	for table, columns := range requiredColumns {
		for _, column := range columns {
			var count int
			if err := db.QueryRow(`SELECT COUNT(*) FROM information_schema.columns
				WHERE table_schema = DATABASE() AND table_name = ? AND column_name = ?`,
				table, column).Scan(&count); err != nil {
				return fmt.Errorf("检查 MySQL 数据表 %s 的列失败: %w", table, err)
			}
			if count != 1 {
				return fmt.Errorf("MySQL 数据表 %s 缺少列 %s", table, column)
			}
		}
	}
	return nil
}

func checkMySQLV3Shape(db *sql.DB) error {
	rows, err := db.Query(`SELECT column_name FROM information_schema.key_column_usage
		WHERE table_schema=DATABASE() AND table_name='spec_mappings'
		  AND constraint_name='PRIMARY' ORDER BY ordinal_position`)
	if err != nil {
		return fmt.Errorf("检查 spec_mappings 主键失败: %w", err)
	}
	var primary []string
	for rows.Next() {
		var column string
		if err := rows.Scan(&column); err != nil {
			rows.Close()
			return fmt.Errorf("检查 spec_mappings 主键失败: %w", err)
		}
		primary = append(primary, column)
	}
	rows.Close()
	if strings.Join(primary, ",") != "shopee_goods_id,spec_key,pdd_goods_id" {
		return fmt.Errorf("spec_mappings 主键不正确，实际为 (%s)", strings.Join(primary, ","))
	}
	for _, column := range []string{"shopee_goods_id", "spec_key", "pdd_goods_id"} {
		if err := checkMySQLVarcharColumn(db, "spec_mappings", column, 191, false, "utf8mb4_bin", ""); err != nil {
			return err
		}
	}
	if err := checkMySQLVarcharColumn(db, "syb_orders", "spec_key", 191, true, "utf8mb4_bin", ""); err != nil {
		return err
	}
	if err := checkMySQLVarcharColumn(db, "shopee_products", "source", 16, false, "utf8mb4_bin", "report"); err != nil {
		return err
	}
	var enforced, checkClause string
	if err := db.QueryRow(`SELECT tc.enforced, cc.check_clause
		FROM information_schema.table_constraints tc
		JOIN information_schema.check_constraints cc
		  ON cc.constraint_schema=tc.constraint_schema AND cc.constraint_name=tc.constraint_name
		WHERE tc.constraint_schema=DATABASE() AND tc.table_name='shopee_products'
		  AND tc.constraint_name='chk_shopee_products_source' AND tc.constraint_type='CHECK'`).Scan(&enforced, &checkClause); err != nil {
		return fmt.Errorf("shopee_products.source CHECK 缺失或不可读: %w", err)
	}
	if enforced != "YES" {
		return fmt.Errorf("shopee_products.source CHECK 未启用")
	}
	normalizedClause := strings.NewReplacer("`", "", " ", "", "(", "", ")", "", "_utf8mb4", "", `\`, "").Replace(strings.ToLower(checkClause))
	if !strings.Contains(normalizedClause, "sourcein'report','syb'") {
		return fmt.Errorf("shopee_products.source CHECK 表达式不正确")
	}
	return nil
}

func checkMySQLVarcharColumn(db *sql.DB, table, column string, length int64, nullable bool, collation, defaultValue string) error {
	var dataType, isNullable string
	var actualLength sql.NullInt64
	var actualCollation, actualDefault sql.NullString
	if err := db.QueryRow(`SELECT data_type, character_maximum_length, is_nullable, collation_name, column_default
		FROM information_schema.columns WHERE table_schema=DATABASE() AND table_name=? AND column_name=?`,
		table, column).Scan(&dataType, &actualLength, &isNullable, &actualCollation, &actualDefault); err != nil {
		return fmt.Errorf("检查 MySQL 列 %s.%s 结构失败: %w", table, column, err)
	}
	wantNullable := "NO"
	if nullable {
		wantNullable = "YES"
	}
	if dataType != "varchar" || !actualLength.Valid || actualLength.Int64 != length ||
		isNullable != wantNullable || actualCollation.String != collation {
		return fmt.Errorf("MySQL 列 %s.%s 结构不正确", table, column)
	}
	if defaultValue != "" && (!actualDefault.Valid || actualDefault.String != defaultValue) {
		return fmt.Errorf("MySQL 列 %s.%s 默认值不正确", table, column)
	}
	return nil
}