package mysql

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"strings"

	_ "github.com/go-sql-driver/mysql"
	"hyapp/pkg/appcode"
	"hyapp/pkg/xerr"
	activitydomain "hyapp/services/activity-service/internal/domain/activity"
)

// Repository 是 activity-service 的 MySQL 存储入口。
type Repository struct {
	db *sql.DB
}

// Open 创建 MySQL 连接池并做启动 ping。
func Open(ctx context.Context, dsn string) (*Repository, error) {
	if strings.TrimSpace(dsn) == "" {
		return nil, xerr.New(xerr.InvalidArgument, "mysql_dsn is required")
	}

	db, err := sql.Open("mysql", dsn)
	if err != nil {
		return nil, err
	}

	if err := db.PingContext(ctx); err != nil {
		_ = db.Close()
		return nil, err
	}

	return &Repository{db: db}, nil
}

// Migrate performs narrow, idempotent local schema fixes for activity-service.
func (r *Repository) Migrate(ctx context.Context) error {
	if r == nil || r.db == nil {
		return xerr.New(xerr.Unavailable, "mysql repository is not configured")
	}
	if err := r.ensureLuckyDrawPoolID(ctx); err != nil {
		return err
	}
	return nil
}

// Close 释放 MySQL 连接池。
func (r *Repository) Close() error {
	if r == nil || r.db == nil {
		return nil
	}

	return r.db.Close()
}

// Ping 验证 MySQL 当前可用。
func (r *Repository) Ping(ctx context.Context) error {
	if r == nil || r.db == nil {
		return xerr.New(xerr.Unavailable, "mysql repository is not configured")
	}

	return r.db.PingContext(ctx)
}

func (r *Repository) ensureLuckyDrawPoolID(ctx context.Context) error {
	const table = "lucky_draw_records"
	hasPoolID, err := r.columnExists(ctx, table, "pool_id")
	if err != nil {
		return err
	}
	if !hasPoolID {
		if _, err := r.db.ExecContext(ctx, `
			ALTER TABLE lucky_draw_records
			ADD COLUMN pool_id VARCHAR(96) NOT NULL DEFAULT '' COMMENT '幸运礼物奖池 ID' AFTER anchor_id`); err != nil {
			return err
		}
	}
	if _, err := r.db.ExecContext(ctx, `UPDATE lucky_draw_records SET pool_id = gift_id WHERE pool_id = ''`); err != nil {
		return err
	}
	hasPoolIndex, err := r.indexExists(ctx, table, "idx_lucky_draw_pool")
	if err != nil {
		return err
	}
	if !hasPoolIndex {
		if _, err := r.db.ExecContext(ctx, `CREATE INDEX idx_lucky_draw_pool ON lucky_draw_records (app_code, pool_id, created_at_ms)`); err != nil {
			return err
		}
	}
	return nil
}

func (r *Repository) columnExists(ctx context.Context, table string, column string) (bool, error) {
	database, err := r.currentDatabase(ctx)
	if err != nil {
		return false, err
	}
	var count int
	if err := r.db.QueryRowContext(ctx, `
		SELECT COUNT(*)
		FROM information_schema.COLUMNS
		WHERE TABLE_SCHEMA = ? AND TABLE_NAME = ? AND COLUMN_NAME = ?`,
		database, table, column,
	).Scan(&count); err != nil {
		return false, err
	}
	return count > 0, nil
}

func (r *Repository) indexExists(ctx context.Context, table string, index string) (bool, error) {
	database, err := r.currentDatabase(ctx)
	if err != nil {
		return false, err
	}
	var count int
	if err := r.db.QueryRowContext(ctx, `
		SELECT COUNT(*)
		FROM information_schema.STATISTICS
		WHERE TABLE_SCHEMA = ? AND TABLE_NAME = ? AND INDEX_NAME = ?`,
		database, table, index,
	).Scan(&count); err != nil {
		return false, err
	}
	return count > 0, nil
}

func (r *Repository) currentDatabase(ctx context.Context) (string, error) {
	var database sql.NullString
	if err := r.db.QueryRowContext(ctx, `SELECT DATABASE()`).Scan(&database); err != nil {
		return "", err
	}
	if !database.Valid || strings.TrimSpace(database.String) == "" {
		return "", fmt.Errorf("mysql database is not selected")
	}
	return database.String, nil
}

// GetActivity 从 MySQL 活动配置表读取同步查询投影。
func (r *Repository) GetActivity(ctx context.Context, activityID string) (activitydomain.Activity, error) {
	if r == nil || r.db == nil {
		return activitydomain.Activity{}, xerr.New(xerr.Unavailable, "mysql repository is not configured")
	}

	row := r.db.QueryRowContext(ctx,
		`SELECT app_code, activity_id, status, updated_at_ms
		 FROM activities
		 WHERE app_code = ? AND activity_id = ?`,
		appcode.FromContext(ctx),
		activityID,
	)

	var activity activitydomain.Activity
	var status string
	if err := row.Scan(&activity.AppCode, &activity.ActivityID, &status, &activity.UpdatedAtMs); err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			// 未配置活动时返回 NotFound，上层可决定是否降级为 inactive。
			return activitydomain.Activity{}, xerr.New(xerr.NotFound, "activity not found")
		}

		return activitydomain.Activity{}, err
	}
	activity.Status = activitydomain.Status(status)

	return activity, nil
}