package braille

import (
	"os"
	"path/filepath"
	"sort"
	"strings"
)

const tableDirectory = "/usr/share/liblouis/tables"

type TableOption struct {
	Label string
	File  string
}

// AvailableTables lists installed literary and computer tables for the
// current message locale. English US also offers UEB tables.
func AvailableTables() []TableOption {
	locale := ""
	for _, key := range []string{"LC_ALL", "LC_MESSAGES", "LANG"} {
		if value := os.Getenv(key); value != "" {
			locale = value
			break
		}
	}
	return tablesForLocale(tableDirectory, locale)
}

func tablesForLocale(dir, locale string) []TableOption {
	locale = strings.ToLower(strings.ReplaceAll(strings.Split(strings.Split(locale, ".")[0], "@")[0], "_", "-"))
	if locale == "" || locale == "c" || locale == "posix" {
		locale = "en-us"
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil
	}
	var result []TableOption
	for _, entry := range entries {
		name := entry.Name()
		lower := strings.ToLower(name)
		if entry.IsDir() || !(strings.HasSuffix(lower, ".ctb") || strings.HasSuffix(lower, ".utb")) ||
			strings.Contains(lower, "interline") || strings.Contains(lower, "mathtext") ||
			!(strings.HasPrefix(lower, locale+"-") || locale == "en-us" && strings.HasPrefix(lower, "en-ueb-")) {
			continue
		}
		label := strings.TrimSuffix(strings.TrimSuffix(name, ".ctb"), ".utb")
		label = strings.ReplaceAll(label, "-g1", " Grade 1")
		label = strings.ReplaceAll(label, "-g2", " Grade 2")
		label = strings.ReplaceAll(label, "-g3", " Grade 3")
		result = append(result, TableOption{Label: label, File: filepath.Join(dir, name)})
	}
	sort.Slice(result, func(i, j int) bool { return result[i].Label < result[j].Label })
	return result
}