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

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

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

const h5LinkGroup = "h5-links"

const listH5LinksSQL = "SELECT `key`, COALESCE(description, ''), COALESCE(value, ''), updated_at_ms FROM admin_app_configs WHERE `group` = ? ORDER BY `key` ASC"
const bdLeaderPositionAliasSQL = `
	SELECT position_alias
	FROM admin_bd_leader_position_aliases
	WHERE app_code = ? AND user_id = ?
	LIMIT 1`
const listExploreTabsSQL = `
	SELECT id, app_code, tab, h5_url, enabled, sort_order, updated_at_ms
	FROM admin_app_explore_tabs
	WHERE app_code = ? AND enabled = TRUE
	ORDER BY sort_order ASC, id DESC`
const listAppBannersSQL = `
	SELECT id, app_code, cover_url, room_small_image_url, banner_type, display_scope, param, platform, sort_order, region_id, country_code, description, starts_at_ms, ends_at_ms, updated_at_ms
	FROM admin_app_banners
	WHERE app_code = ? AND status = 'active' AND FIND_IN_SET(?, display_scope) > 0
	  AND (? = '' OR platform = ?)
	  AND (region_id = 0 OR region_id = ?)
	  AND (country_code = '' OR country_code = ?)
	  AND (starts_at_ms = 0 OR starts_at_ms <= ?)
	  AND (ends_at_ms = 0 OR ends_at_ms > ?)
	ORDER BY sort_order ASC, id DESC`
const latestAppVersionSQL = `
	SELECT id, app_code, platform, version, build_number, force_update, download_url, COALESCE(description, ''), updated_at_ms
	FROM admin_app_versions
	WHERE app_code = ? AND platform = ?
	ORDER BY build_number DESC, id DESC
	LIMIT 1`

// 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"`
}

// H5LinkQuery 是 H5 入口配置的可选用户态筛选条件。
type H5LinkQuery struct {
	AppCode string
	UserID  int64
}

// ExploreTab 是后台 APP配置/Explore配置 中启用的 H5 tab。
type ExploreTab struct {
	ID          uint   `json:"id"`
	AppCode     string `json:"app_code"`
	Tab         string `json:"tab"`
	H5URL       string `json:"h5_url"`
	Enabled     bool   `json:"enabled"`
	SortOrder   int    `json:"sort_order"`
	UpdatedAtMs int64  `json:"updated_at_ms"`
}

// BannerQuery 是 App banner 的公开筛选条件。
type BannerQuery struct {
	AppCode      string
	DisplayScope string
	Platform     string
	RegionID     int64
	Country      string
}

// Banner 是 gateway 下发给 App 指定显示范围的 banner 配置。
type Banner struct {
	ID                uint     `json:"id"`
	CoverURL          string   `json:"cover_url"`
	RoomSmallImageURL string   `json:"room_small_image_url,omitempty"`
	BannerType        string   `json:"type"`
	DisplayScope      string   `json:"display_scope"`
	DisplayScopes     []string `json:"display_scopes,omitempty"`
	Param             string   `json:"param"`
	Platform          string   `json:"platform"`
	SortOrder         int      `json:"sort_order"`
	RegionID          int64    `json:"region_id,omitempty"`
	CountryCode       string   `json:"country_code,omitempty"`
	Description       string   `json:"description,omitempty"`
	StartsAtMs        int64    `json:"starts_at_ms,omitempty"`
	EndsAtMs          int64    `json:"ends_at_ms,omitempty"`
	UpdatedAtMs       int64    `json:"updated_at_ms"`
}

// VersionQuery 是 App 检查更新的公开筛选条件。
type VersionQuery struct {
	AppCode            string
	Platform           string
	CurrentBuildNumber int64
}

// Version 是后台 APP配置/版本管理 中当前平台的最新 App 版本。
type Version struct {
	ID          uint   `json:"id"`
	AppCode     string `json:"app_code"`
	Platform    string `json:"platform"`
	Version     string `json:"version"`
	BuildNumber int64  `json:"build_number"`
	ForceUpdate bool   `json:"force_update"`
	DownloadURL string `json:"download_url"`
	Description string `json:"description"`
	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, query H5LinkQuery) ([]H5Link, error)
	ListExploreTabs(ctx context.Context, appCode string) ([]ExploreTab, error)
	ListBanners(ctx context.Context, query BannerQuery) ([]Banner, error)
	LatestVersion(ctx context.Context, query VersionQuery) (Version, error)
}

// MySQLReader 从 hyapp_admin 读取后台 App 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 返回后台动态维护的 H5 入口集合。
func (r *MySQLReader) ListH5Links(ctx context.Context, query H5LinkQuery) ([]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()

	items := make([]H5Link, 0)
	for rows.Next() {
		var item H5Link
		if err := rows.Scan(&item.Key, &item.Label, &item.URL, &item.UpdatedAtMs); err != nil {
			return nil, err
		}
		item.Key = strings.TrimSpace(item.Key)
		item.Label = strings.TrimSpace(item.Label)
		if item.Label == "" {
			item.Label = item.Key
		}
		item.URL = strings.TrimSpace(item.URL)
		items = append(items, item)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	if alias, err := r.bdLeaderPositionAlias(ctx, query); err != nil {
		return nil, err
	} else if alias != "" {
		applyAdminH5LinkAlias(items, alias)
	}
	return items, nil
}

func (r *MySQLReader) bdLeaderPositionAlias(ctx context.Context, query H5LinkQuery) (string, error) {
	if query.UserID <= 0 {
		return "", nil
	}
	var alias string
	err := r.db.QueryRowContext(ctx, bdLeaderPositionAliasSQL, normalizeAppCode(query.AppCode), query.UserID).Scan(&alias)
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	if isMissingTableError(err) {
		// gateway 读的是 admin 库；迁移未发布前保持 H5 配置原始返回，不让可选别名阻断老环境。
		return "", nil
	}
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(alias), nil
}

// ListExploreTabs 返回当前 App 启用的 Explore H5 tabs；后台关闭的 tab 不下发给客户端。
func (r *MySQLReader) ListExploreTabs(ctx context.Context, appCode string) ([]ExploreTab, error) {
	if r == nil || r.db == nil {
		return nil, errors.New("app config reader is not configured")
	}

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

	items := make([]ExploreTab, 0)
	for rows.Next() {
		var item ExploreTab
		if err := rows.Scan(&item.ID, &item.AppCode, &item.Tab, &item.H5URL, &item.Enabled, &item.SortOrder, &item.UpdatedAtMs); err != nil {
			return nil, err
		}
		items = append(items, item)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return items, nil
}

// ListBanners 返回当前 App、显示范围、平台和地域可见的 banner。
func (r *MySQLReader) ListBanners(ctx context.Context, query BannerQuery) ([]Banner, error) {
	if r == nil || r.db == nil {
		return nil, errors.New("app config reader is not configured")
	}

	appCode := normalizeAppCode(query.AppCode)
	displayScope := NormalizeBannerDisplayScope(query.DisplayScope)
	if displayScope == "" {
		return []Banner{}, nil
	}
	platform := normalizePlatform(query.Platform)
	country := normalizeCountry(query.Country)
	nowMs := time.Now().UTC().UnixMilli()
	rows, err := r.db.QueryContext(ctx, listAppBannersSQL, appCode, displayScope, platform, platform, query.RegionID, country, nowMs, nowMs)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	items := make([]Banner, 0)
	for rows.Next() {
		var item Banner
		var appCode string
		var updatedAtMS int64
		if err := rows.Scan(
			&item.ID,
			&appCode,
			&item.CoverURL,
			&item.RoomSmallImageURL,
			&item.BannerType,
			&item.DisplayScope,
			&item.Param,
			&item.Platform,
			&item.SortOrder,
			&item.RegionID,
			&item.CountryCode,
			&item.Description,
			&item.StartsAtMs,
			&item.EndsAtMs,
			&updatedAtMS,
		); err != nil {
			return nil, err
		}
		item.UpdatedAtMs = updatedAtMS
		item.DisplayScopes = bannerDisplayScopeList(item.DisplayScope)
		items = append(items, item)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return items, nil
}

// LatestVersion 返回指定 App 和平台的最高 build_number 版本；未配置时返回空版本，方便 App 端按无更新处理。
func (r *MySQLReader) LatestVersion(ctx context.Context, query VersionQuery) (Version, error) {
	if r == nil || r.db == nil {
		return Version{}, errors.New("app config reader is not configured")
	}

	var item Version
	err := r.db.QueryRowContext(ctx, latestAppVersionSQL, normalizeAppCode(query.AppCode), normalizePlatform(query.Platform)).Scan(
		&item.ID,
		&item.AppCode,
		&item.Platform,
		&item.Version,
		&item.BuildNumber,
		&item.ForceUpdate,
		&item.DownloadURL,
		&item.Description,
		&item.UpdatedAtMs,
	)
	if errors.Is(err, sql.ErrNoRows) {
		return Version{AppCode: normalizeAppCode(query.AppCode), Platform: normalizePlatform(query.Platform)}, nil
	}
	if err != nil {
		return Version{}, err
	}
	return item, 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
	ExploreTabs     []ExploreTab
	Banners         []Banner
	Version         Version
	Err             error
	PositionAliases map[string]string
}

// ListH5Links 返回预置 H5 配置。
func (r StaticReader) ListH5Links(_ context.Context, query H5LinkQuery) ([]H5Link, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	out := make([]H5Link, len(r.Links))
	copy(out, r.Links)
	if alias := strings.TrimSpace(r.PositionAliases[bdLeaderPositionAliasKey(query.AppCode, query.UserID)]); alias != "" {
		applyAdminH5LinkAlias(out, alias)
	}
	return out, nil
}

// ListExploreTabs 返回预置 Explore tab 配置。
func (r StaticReader) ListExploreTabs(context.Context, string) ([]ExploreTab, error) {
	if r.Err != nil {
		return nil, r.Err
	}

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

// ListBanners 返回预置 App banner 配置。
func (r StaticReader) ListBanners(context.Context, BannerQuery) ([]Banner, error) {
	if r.Err != nil {
		return nil, r.Err
	}

	out := make([]Banner, len(r.Banners))
	copy(out, r.Banners)
	for index := range out {
		if len(out[index].DisplayScopes) == 0 {
			out[index].DisplayScopes = bannerDisplayScopeList(out[index].DisplayScope)
		}
	}
	return out, nil
}

// LatestVersion 返回预置版本配置。
func (r StaticReader) LatestVersion(_ context.Context, query VersionQuery) (Version, error) {
	if r.Err != nil {
		return Version{}, r.Err
	}
	item := r.Version
	if item.AppCode == "" {
		item.AppCode = normalizeAppCode(query.AppCode)
	}
	if item.Platform == "" {
		item.Platform = normalizePlatform(query.Platform)
	}
	return item, nil
}

func normalizeAppCode(value string) string {
	value = strings.ToLower(strings.TrimSpace(value))
	if value == "" {
		return "lalu"
	}
	return value
}

func normalizePlatform(value string) string {
	return strings.ToLower(strings.TrimSpace(value))
}

func normalizeCountry(value string) string {
	return strings.ToUpper(strings.TrimSpace(value))
}

func applyAdminH5LinkAlias(items []H5Link, alias string) {
	alias = strings.TrimSpace(alias)
	if alias == "" {
		return
	}
	for index := range items {
		if strings.EqualFold(strings.TrimSpace(items[index].Key), "admin") {
			// admin 入口只覆盖展示名，key 和 URL 仍来自后台 H5 配置，保证 Flutter 路由识别不变。
			items[index].Label = alias
		}
	}
}

func bdLeaderPositionAliasKey(appCode string, userID int64) string {
	return normalizeAppCode(appCode) + ":" + strconv.FormatInt(userID, 10)
}

func isMissingTableError(err error) bool {
	var mysqlErr *mysqlDriver.MySQLError
	return errors.As(err, &mysqlErr) && mysqlErr.Number == 1146
}

// NormalizeBannerDisplayScope 统一 App 和后台约定的显示范围枚举。
func NormalizeBannerDisplayScope(value string) string {
	value = strings.ToLower(strings.TrimSpace(value))
	switch value {
	case "":
		return "home"
	case "home", "首页":
		return "home"
	case "room", "房间内":
		return "room"
	case "recharge", "充值页":
		return "recharge"
	default:
		return ""
	}
}

func bannerDisplayScopeList(value string) []string {
	seen := make(map[string]struct{}, 3)
	for _, part := range strings.Split(value, ",") {
		scope := NormalizeBannerDisplayScope(part)
		if scope != "" {
			seen[scope] = struct{}{}
		}
	}
	out := make([]string, 0, len(seen))
	for _, scope := range []string{"home", "room", "recharge"} {
		if _, ok := seen[scope]; ok {
			out = append(out, scope)
		}
	}
	return out
}