package main

import (
	"errors"
	"flag"
	"fmt"
	"html/template"
	"io/ioutil"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"git.gutmet.org/go-mastodon.git"
	goutil "git.gutmet.org/goutil.git/misc"
)

const (
	CHARACTER_LIMIT = 500
	MAX_BYTES       = 50 * 1024 * 1024
)

var formatTemplate *template.Template

type mediaKind int

const (
	UNKNOWN mediaKind = iota
	PIC
	GIF
	VIDEO
)

func kind(path string) mediaKind {
	ext := filepath.Ext(path)
	switch ext {
	case ".jpg":
		fallthrough
	case ".jpeg":
		fallthrough
	case ".png":
		return PIC
	case ".gif":
		return GIF
	case ".mp4":
		return VIDEO
	}
	return UNKNOWN
}

func optLogFatal(decorum string, err error) {
	if err != nil && err.Error() != "" {
		panic("swill: " + decorum + ": " + err.Error())
	}
}

func checkUsage(args []string, argcMin int, argcMax int, help string) {
	argc := len(args)
	if (argcMin > -1 && argc < argcMin) || (argcMax > -1 && argc > argcMax) {
		fmt.Fprintf(os.Stderr, "USAGE: %s %s\n", os.Args[0], help)
		os.Exit(-1)
	}
}

type data struct {
	status []string
	pics   []string
	gifs   []string
	videos []string
}

func (d *data) getStatus(i int) string {
	return goutil.StrSliceAt(d.status, i)
}

func (d *data) getGif(i int) string {
	return goutil.StrSliceAt(d.gifs, i)
}

func (d *data) getVideo(i int) string {
	return goutil.StrSliceAt(d.videos, i)
}

func uploadFile(file string) *mastodon.Attachment {
	att, err := mastodon.UploadMedia(file)
	optLogFatal("uploadFile", err)
	return att
}

func uploadAll(files []string) []mastodon.ID {
	ids := []mastodon.ID{}
	for _, f := range files {
		if f != "" {
			id := uploadFile(f).ID
			ids = append(ids, id)
		}
	}
	return ids
}

func (d *data) uploadPics(from, to int) []mastodon.ID {
	pics := goutil.StrSlice(d.pics, from, to)
	return uploadAll(pics)
}

func (d *data) uploadGif(i int) []mastodon.ID {
	gif := d.getGif(i)
	return uploadAll([]string{gif})
}

func (d *data) uploadVideo(i int) []mastodon.ID {
	vid := d.getVideo(i)
	return uploadAll([]string{vid})
}

func setStatus(f statusFlags, msg string, mediaIDs []mastodon.ID, previous *mastodon.Status) *mastodon.Status {
	toot := &mastodon.Toot{
		Status:   msg,
		MediaIDs: mediaIDs,
	}
	if previous != nil {
		toot.InReplyToID = previous.ID
	}
	if f.visibility != "" {
		toot.Visibility = f.visibility
	}
	status, err := mastodon.PostStatus(toot)
	optLogFatal("setStatus", err)
	return status
}

func (d *data) push(f statusFlags, previous *mastodon.Status) []*mastodon.Status {
	empty := false
	i, g, v := 0, 0, 0
	statuses := []*mastodon.Status{}
	if d == nil {
		return statuses
	}
	for !empty {
		empty = true
		status := d.getStatus(i)
		mediaIDs := []mastodon.ID{}
		if status != "" {
			empty = false
		}
		from := i * 4
		to := (i + 1) * 4
		mediaIDs = d.uploadPics(from, to)
		if len(mediaIDs) == 0 {
			mediaIDs = d.uploadGif(g)
			g++
		}
		if len(mediaIDs) == 0 {
			mediaIDs = d.uploadVideo(v)
			v++
		}
		if len(mediaIDs) > 0 {
			empty = false
		}
		if !empty {
			t := setStatus(f, status, mediaIDs, previous)
			statuses = append(statuses, t)
			previous = t
			i++
		}
	}
	return statuses
}

func exitIfInvalid(path string) {
	log := func(err error) { optLogFatal("exitIfInvalid", err) }
	// check existence AND readability
	f, err := os.Open(path)
	log(err)
	defer f.Close()
	tmp, err := ioutil.ReadAll(f)
	log(err)
	if len(tmp) > MAX_BYTES {
		log(errors.New("File too big: " + path + " is bigger than maximum of " + strconv.Itoa(MAX_BYTES) + " Bytes"))
	}
}

func lastSpace(slice []rune) int {
	for i := len(slice) - 1; i >= 0; i-- {
		if slice[i] == ' ' {
			return i
		}
	}
	return -1
}

func splitStatus(status string) []string {
	characterLimit := CHARACTER_LIMIT
	// Twitter has an insane definition of what counts as a character
	// ( see https://developer.twitter.com/en/docs/counting-characters )
	// - as a crude approximation, anything outside LATIN-1 halfs the limit
	// for _, ch := range status {
	// 	if ch > 0x10FF {
	// 		characterLimit = CHARACTER_LIMIT / 2
	// 		break
	// 	}
	// }
	asRunes := []rune(status)
	split := []string{}
	for len(asRunes) != 0 {
		var limit int
		if len(asRunes) <= characterLimit {
			limit = len(asRunes)
		} else {
			limit = lastSpace(asRunes[0:characterLimit])
			if limit == -1 {
				limit = characterLimit
			} else {
				limit = limit + 1
			}
		}
		split = append(split, string(asRunes[0:limit]))
		asRunes = asRunes[limit:]
	}
	return split
}

func splitArguments(args []string) data {
	if len(args) < 1 {
		fmt.Fprintln(os.Stderr, "Usage: swill status STATUS [FILE1 FILE2 ...]")
		os.Exit(-1)
	}
	d := data{}
	d.status = splitStatus(args[0])
	for _, arg := range args[1:] {
		exitIfInvalid(arg)
		switch kind(arg) {
		case PIC:
			d.pics = append(d.pics, arg)
		case GIF:
			d.gifs = append(d.gifs, arg)
		case VIDEO:
			d.videos = append(d.videos, arg)
		default:
			optLogFatal("splitArguments", errors.New("Unsupported file: "+arg))
		}
	}
	return d
}

func updateStatus(f statusFlags, args []string) []*mastodon.Status {
	d := splitArguments(args)
	return d.push(f, nil)
}

func PrintStatuses(statuses []*mastodon.Status) {
	if formatTemplate != nil {
		optLogFatal("printStatuses", formatTemplate.Execute(os.Stdout, statuses))
	} else {
		for _, status := range statuses {
			fmt.Println(status.Account.Username, status.CreatedAt)
			fmt.Println(status.Content)
			fmt.Println("----------")
		}
	}
}

type statusFlags struct {
	visibility string
}

func status(f statusFlags, args []string) error {
	checkUsage(args, 1, -1, "status STATUS [FILE1 FILE2 ...]")
	statuses := updateStatus(f, args)
	PrintStatuses(statuses)
	return nil
}

func statusCommand() (goutil.CommandFlagsInit, goutil.CommandFunc) {
	f := statusFlags{}
	flagsInit := func(s *flag.FlagSet) {
		s.StringVar(&f.visibility, "visibility", "", "public, unlisted, private or direct")
	}
	return flagsInit, func(args []string) error { return status(f, args) }
}

func userTimeline(args []string) error {
	checkUsage(args, 1, 1, "timeline USER")
	user := args[0]
	account, err := mastodon.LookupAccount(user)
	optLogFatal("userTimeline - lookup account", err)
	statuses, err := account.GetStatuses(nil)
	optLogFatal("userTimeline - get statuses", err)
	PrintStatuses(statuses)
	return nil
}

type generalFlags struct {
	templateFile string
}

func wrapCommand(cmd goutil.CommandFunc) func() (goutil.CommandFlagsInit, goutil.CommandFunc) {
	return wrapCommandFl(func() (goutil.CommandFlagsInit, goutil.CommandFunc) { return nil, cmd })
}

func wrapCommandFl(cmd func() (goutil.CommandFlagsInit, goutil.CommandFunc)) func() (goutil.CommandFlagsInit, goutil.CommandFunc) {
	f := generalFlags{}
	flagsInit := func(s *flag.FlagSet) {
		s.StringVar(&f.templateFile, "template", "", "use a template file to format tweets")
	}
	return func() (goutil.CommandFlagsInit, goutil.CommandFunc) {
		formerInit, commandFunc := cmd()
		return func(s *flag.FlagSet) {
				if formerInit != nil {
					formerInit(s)
				}
				flagsInit(s)
			}, func(args []string) error {
				if f.templateFile != "" {
					formatTemplate = template.Must(template.New(filepath.Base(f.templateFile)).Funcs(template.FuncMap{"replaceAll": strings.ReplaceAll}).ParseFiles(f.templateFile))
				}
				return commandFunc(args)
			}
	}
}

func main() {
	defer func() {
		if r := recover(); r != nil {
			fmt.Fprintln(os.Stderr, r)
			os.Exit(-1)
		}
	}()
	initializeMastodon()
	commands := []goutil.Command{
		goutil.NewCommandWithFlags("status", wrapCommandFl(statusCommand), "post a status with message and/or media"),
		goutil.NewCommandWithFlags("timeline", wrapCommand(userTimeline), "get timeline of a specific user"),
	}
	_ = goutil.Execute(commands)
}