package main

import (
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"text/template"
	"time"

	"code.osinet.fr/fgm/kurz/translations"

	"github.com/nicksnyder/go-i18n/v2/i18n"
	"github.com/spf13/cobra"
	"golang.org/x/text/language"
	"gopkg.in/yaml.v2"
)

var cmdGenerateTranslations = &cobra.Command{
	Args:  cobra.NoArgs,
	Long:  "Generate the translations package",
	Run:   generateTranslationsHandler,
	Short: "Converts the messages.*.yaml files to a compilable i18n messages embed package. Only useful during Kurz development",
	Use:   "generate-translations",
}

func init() {
	cmd.AddCommand(cmdGenerateTranslations)
}

/*
dumpMessages is a debug helper, logging a messageMap in YAML format for readability.
*/
func dumpMessages(messageMap translations.MessageMap) {
	out, err := yaml.Marshal(messageMap)
	if err != nil {
		panic(err)
	}
	log.Println("Messages:\n" + string(out))
}

func generateTranslationsHandler(cmd *cobra.Command, args []string) {
	cwd, err := os.Getwd()
	if err != nil {
		panic(err)
	}
	t0 := time.Now()
	log.Printf("Finding message catalogs below %s\n", cwd)

	tags := []string{
		language.English.String(),
		language.French.String(),
	}

	messageMap := make(translations.MessageMap)
	for _, tag := range tags {
		messageMap[language.Make(tag)] = [](*i18n.Message){}
	}
	// Build the regex matching message file names.
	re := regexp.MustCompile("messages\\.(?:" + strings.Join(tags, "|") + ")\\.yaml")
	scanned := 0
	catalogCount := 0
	walkErr := filepath.Walk(cwd, scanCatalog(messageMap, re, &scanned, &catalogCount))
	if walkErr != nil {
		panic(walkErr)
	}

	t1 := time.Now()
	diff := t1.Sub(t0)
	log.Printf("%d items scanned, %d catalogs loaded in %d msec\n", scanned, catalogCount, diff/time.Millisecond)
	// dumpMessages(messageMap)

	pwd, err := os.Getwd()
	if err != nil {
		panic(err)
	}
	println(pwd)
	translationsDir := pwd + "/translations"
	tpl := template.Must(template.ParseFiles(translationsDir + "/template.go.gotext"))
	gen, err := os.Create(translationsDir + "/generated.go")
	if err != nil {
		panic(err)
	}
	err = tpl.ExecuteTemplate(gen, "template.go.gotext", messageMap)
	if err != nil {
		panic(err)
	}
}

/*
parseMessageFileBytes merges the messages found in "buf" into the messageMap.

See scanCatalog().
*/
func parseMessages(messagesMap translations.MessageMap, buf []byte, tag language.Tag) error {
	if len(buf) == 0 {
		return nil
	}

	raw := make(map[string]interface{})
	if err := yaml.Unmarshal(buf, &raw); err != nil {
		return err
	}
	for id, item := range raw {
		switch item.(type) {
		// Degenerate case: "key: one"
		case string:
			message := &i18n.Message{
				ID:  id,
				Other: item.(string),
			}
			messagesMap[tag] = append(messagesMap[tag], message)

		// Normal case:	 key: { ID: ..., one: ... }.
		case map[interface{}]interface{}:
			serial, err := yaml.Marshal(item)
			if err != nil {
				panic(err)
			}
			message := &i18n.Message{
				ID: id,
			}
			err = yaml.Unmarshal(serial, message)
			if err != nil {
				panic(err)
			}
			messagesMap[tag] = append(messagesMap[tag], message)

		default:
			log.Fatalf("Unsupported message format %#v", item)
		}
	}
	return nil
}

// parsePath is a copy of go-i18n.internal.parsePath
//
// Used under its MIT license.
func parsePath(path string) (langTag, format string) {
	formatStartIdx := -1
	for i := len(path) - 1; i >= 0; i-- {
		c := path[i]
		if os.IsPathSeparator(c) {
			if formatStartIdx != -1 {
				langTag = path[i+1 : formatStartIdx]
			}
			return
		}
		if path[i] == '.' {
			if formatStartIdx != -1 {
				langTag = path[i+1 : formatStartIdx]
				return
			}
			if formatStartIdx == -1 {
				format = path[i+1:]
				formatStartIdx = i
			}
		}
	}
	if formatStartIdx != -1 {
		langTag = path[:formatStartIdx]
	}
	return
}

/*
scanCatalog builds a WalkFn callback parsing each message file as it is found, and
merging its values into messageMap.

See generateTranslationsHandler
*/
func scanCatalog(messageMap translations.MessageMap, re *regexp.Regexp, scanned *int, catalogCount *int) filepath.WalkFunc {
	return func(path string, info os.FileInfo, err error) error {
		*scanned++
		if err != nil {
			panic(err)
		}
		if info.IsDir() {
			return nil
		}

		if !re.MatchString(info.Name()) {
			return nil
		}

		langid, _ := parsePath(path)
		tag := language.Make(langid)
		_, ok := messageMap[tag]
		if !ok {
			log.Printf("Found message catalog %s in unexpected language %s, skipping.",
				path, tag.String())
			return nil
		}

		buf, err := ioutil.ReadFile(path)
		if err != nil {
			panic(err)
		}
		err = parseMessages(messageMap, buf, tag)
		*catalogCount++
		return err
	}
}