package service

import (
	"errors"
	"path/filepath"
	"regexp"
	"strings"
)

// 站点背景图（前台 / 后台分轨）
const (
	SettingKeyBgSiteURL   = "bg_site_url"
	SettingKeyBgSiteMode  = "bg_site_mode"
	SettingKeyBgAdminURL  = "bg_admin_url"
	SettingKeyBgAdminMode = "bg_admin_mode"

	BgSurfaceSite  = "site"
	BgSurfaceAdmin = "admin"

	BgModeCover    = "cover"
	BgModeContain  = "contain"
	BgModeRepeat   = "repeat"
	BgModeRepeatX  = "repeat-x"
	BgModeRepeatY  = "repeat-y"
	BgModeStretch  = "stretch"
	BgModeCenter   = "center"
	DefaultBgMode  = BgModeCover
)

// ErrBgFileMissing 设置了合法 URL 但磁盘上没有对应文件
var ErrBgFileMissing = errors.New("背景图文件不存在")

// 仅接受本站上传目录下的 32 位 hex 文件名，禁止外链与路径穿越（写入 CSS url()）
var bgUploadURLRe = regexp.MustCompile(`^/uploads/backgrounds/[0-9a-f]{32}\.(jpg|jpeg|png|webp)$`)

var bgModes = map[string]struct{}{
	BgModeCover:   {},
	BgModeContain: {},
	BgModeRepeat:  {},
	BgModeRepeatX: {},
	BgModeRepeatY: {},
	BgModeStretch: {},
	BgModeCenter:  {},
}

// NormalizeBgMode 校验铺放模式；空串视为默认 cover
func NormalizeBgMode(raw string) (string, bool) {
	m := strings.ToLower(strings.TrimSpace(raw))
	if m == "" {
		return DefaultBgMode, true
	}
	if _, ok := bgModes[m]; !ok {
		return "", false
	}
	return m, true
}

// NormalizeBgURL 校验背景图 URL；空串表示清除（走默认画布）
func NormalizeBgURL(raw string) (string, bool) {
	u := strings.TrimSpace(raw)
	if u == "" {
		return "", true
	}
	u = strings.ToLower(u)
	if !bgUploadURLRe.MatchString(u) {
		return "", false
	}
	return u, true
}

// NormalizeBgSurface 前台 site / 后台 admin
func NormalizeBgSurface(raw string) (string, bool) {
	s := strings.ToLower(strings.TrimSpace(raw))
	if s == BgSurfaceSite || s == BgSurfaceAdmin {
		return s, true
	}
	return "", false
}

func (s *SettingService) BgSiteURL() (string, error) {
	return s.bgURL(SettingKeyBgSiteURL)
}

func (s *SettingService) BgAdminURL() (string, error) {
	return s.bgURL(SettingKeyBgAdminURL)
}

func (s *SettingService) BgSiteMode() (string, error) {
	return s.bgMode(SettingKeyBgSiteMode)
}

func (s *SettingService) BgAdminMode() (string, error) {
	return s.bgMode(SettingKeyBgAdminMode)
}

func (s *SettingService) bgURL(key string) (string, error) {
	v, found, err := s.getValue(key)
	if err != nil || !found {
		return "", err
	}
	u, ok := NormalizeBgURL(v)
	if !ok {
		return "", nil
	}
	return u, nil
}

func (s *SettingService) bgMode(key string) (string, error) {
	v, found, err := s.getValue(key)
	if err != nil || !found {
		return DefaultBgMode, err
	}
	m, ok := NormalizeBgMode(v)
	if !ok {
		return DefaultBgMode, nil
	}
	return m, nil
}

// SetBgSiteURL 保存前台背景；空串删除键
func (s *SettingService) SetBgSiteURL(url string) error {
	return s.setBgURL(SettingKeyBgSiteURL, url)
}

// SetBgAdminURL 保存后台背景；空串删除键
func (s *SettingService) SetBgAdminURL(url string) error {
	return s.setBgURL(SettingKeyBgAdminURL, url)
}

func (s *SettingService) setBgURL(key, url string) error {
	u, ok := NormalizeBgURL(url)
	if !ok {
		return ErrInvalidSiteSetting
	}
	if u == "" {
		return s.deleteKey(key)
	}
	return s.putValue(key, u)
}

func (s *SettingService) SetBgSiteMode(mode string) error {
	return s.setBgMode(SettingKeyBgSiteMode, mode)
}

func (s *SettingService) SetBgAdminMode(mode string) error {
	return s.setBgMode(SettingKeyBgAdminMode, mode)
}

func (s *SettingService) setBgMode(key, mode string) error {
	m, ok := NormalizeBgMode(mode)
	if !ok {
		return ErrInvalidSiteSetting
	}
	if m == DefaultBgMode {
		return s.deleteKey(key)
	}
	return s.putValue(key, m)
}

// BgRelPath 把合法 URL 转成 uploads 根下的相对路径；非法返回空
func BgRelPath(url string) string {
	u, ok := NormalizeBgURL(url)
	if !ok || u == "" {
		return ""
	}
	return filepath.FromSlash(strings.TrimPrefix(u, "/uploads/"))
}