// Package appconfig 读取后台管理维护的 App 运行时配置。
package appconfig

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

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

const h5LinkGroup = "h5-links"

const listH5LinksSQL = "SELECT `key`, COALESCE(value, ''), updated_at FROM admin_app_configs WHERE `group` = ?"

// H5Link 是 gateway 下发给 App 的 H5 入口配置。
type H5Link struct {
	Key         string `json:"key"`
	Label       string `json:"label"`
	URL         string `json:"url"`
	UpdatedAtMs int64  `json:"updated_at_ms"`
}

// Reader 是 HTTP 层读取 H5 配置的最小依赖。
type Reader interface {
	ListH5Links(ctx context.Context) ([]H5Link, error)
}

type h5LinkDefinition struct {
	Key   string
	Label string
}

var h5LinkDefinitions = []h5LinkDefinition{
	{Key: "host-center", Label: "Host Center"},
	{Key: "bd-center", Label: "BD Center"},
	{Key: "bd-leader-center", Label: "BD Leader Center"},
	{Key: "agency-center", Label: "Agency Center"},
	{Key: "invite-user", Label: "Invite User"},
}

// MySQLReader 从 hyapp_admin.admin_app_configs 读取后台 H5 配置。
type MySQLReader struct {
	db *sql.DB
}

// OpenMySQLReader 创建后台配置只读连接池。
func OpenMySQLReader(dsn string) (*MySQLReader, error) {
	db, err := sql.Open("mysql", strings.TrimSpace(dsn))
	if err != nil {
		return nil, err
	}

	return &MySQLReader{db: db}, nil
}

// Close 关闭后台配置连接池。
func (r *MySQLReader) Close() error {
	if r == nil || r.db == nil {
		return nil
	}

	return r.db.Close()
}

// ListH5Links 返回固定 H5 入口集合；未配置的入口保留空 URL，方便客户端按 key 稳定渲染。
func (r *MySQLReader) ListH5Links(ctx context.Context) ([]H5Link, error) {
	if r == nil || r.db == nil {
		return nil, errors.New("app config reader is not configured")
	}

	rows, err := r.db.QueryContext(ctx, listH5LinksSQL, h5LinkGroup)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	configs := make(map[string]H5Link, len(h5LinkDefinitions))
	for rows.Next() {
		var key string
		var url string
		var updatedAt sql.NullTime
		if err := rows.Scan(&key, &url, &updatedAt); err != nil {
			return nil, err
		}

		key = strings.TrimSpace(key)
		link := H5Link{
			Key: key,
			URL: strings.TrimSpace(url),
		}
		if updatedAt.Valid {
			link.UpdatedAtMs = updatedAt.Time.UnixMilli()
		}
		configs[key] = link
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	items := make([]H5Link, 0, len(h5LinkDefinitions))
	for _, definition := range h5LinkDefinitions {
		item := H5Link{
			Key:   definition.Key,
			Label: definition.Label,
		}
		if config, ok := configs[definition.Key]; ok {
			item.URL = config.URL
			item.UpdatedAtMs = config.UpdatedAtMs
		}
		items = append(items, item)
	}

	return items, nil
}

// StaticReader 给测试和临时环境提供内存版 H5 配置读取。
type StaticReader struct {
	Links []H5Link
	Err   error
}

// ListH5Links 返回预置 H5 配置。
func (r StaticReader) ListH5Links(context.Context) ([]H5Link, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	out := make([]H5Link, len(r.Links))
	copy(out, r.Links)
	return out, nil
}