package theme

import (
	"fmt"
	"strings"

	"code.gitea.io/gitea/modules/assetfs"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/public"
	"code.gitea.io/gitea/modules/setting"

	"golang.org/x/sync/singleflight"
)

const (
	key string = "load-themes"
)

var (
	group   singleflight.Group
	assetFs *assetfs.LayeredFS
	loaded  bool
)

// LoadThemes loads installed themes
//
// Note that you can't just run this during init, because webpack mightn't have completed yet.
// Hence, we're loading on first demand.
func LoadThemes() error {
	if loaded {
		return nil
	}

	if assetFs == nil {
		assetFs = public.AssetFS()
	}

	_, err, _ := group.Do(key, func() (interface{}, error) {
		themes, err := loadThemesInner(assetFs)

		if err != nil {
			group.Forget(key)
		} else {
			setting.UI.Themes = themes
			loaded = true
		}

		return nil, err
	})

	return err
}

func loadThemesInner(assetFs *assetfs.LayeredFS) ([]string, error) {
	entries, err := assetFs.ListFiles("assets/css")

	if err != nil {
		return nil, err
	}

	var themes []string

	for _, entry := range entries {
		if !(strings.HasPrefix(entry, "theme-") && strings.HasSuffix(entry, ".css")) {
			continue
		}

		theme := entry[6 : len(entry)-4]
		themes = append(themes, theme)

		log.Info("Found theme: %s", theme)
	}

	if len(themes) > 0 {
		log.Info("Loaded %d themes", len(themes))
		return themes, nil
	} else {
		return nil, fmt.Errorf("no themes found")
	}
}

// GetFriendlyThemeName converts an raw theme name (forgejo-dark) to a friendly name (Forgejo Dark)
//
// Example: forgejo-dark -> Forgejo Dark, catppuccin-maroon-auto -> Catppuccin Maroon Auto
func GetFriendlyThemeName(themeName string) string {
	themeName = strings.ReplaceAll(themeName, "-", " ")

	themeName = strings.ToLower(themeName)
	themeName = strings.Title(themeName)

	return themeName
}