package main

import (
	_ "embed"
	"fmt"
	"image"
	"log"
	"os"
	"path/filepath"
	"slices"
	"strconv"
	"strings"

	"git.yetaga.in/alazyreader/why/filetypes"
	"github.com/dblezek/tga"
	"github.com/disintegration/imaging"
	"golang.org/x/image/webp"
	tk "modernc.org/tk9.0"
)

//go:embed noise.png
var noise []byte // this is a default image

//go:embed icon.png
var icon []byte // this is the app icon

//go:generate go run ./filetypes/cmd/gen.go
var validFileTypes = filetypes.Valid

var fileList *tk.ToplevelWidget
var lb *tk.ListboxWidget
var img = tk.Label()
var fileListBindVar = tk.Variable("FileList")

var directoryState struct {
	currentDirectory string
	currentFile      string
	images           []string
}

func must[T any](t T, err error) T {
	if err != nil {
		panic(err)
	}
	return t
}

func checkErr[T any](_ T, err error) bool {
	return err == nil
}

func isImage(entry os.DirEntry) bool {
	if entry.IsDir() {
		return false
	}
	ext := filepath.Ext(entry.Name())
	if ext == "" {
		return false
	}
	for _, ft := range validFileTypes {
		if slices.Contains(ft.MacExtensions, ext[1:]) {
			return true
		}
	}
	return false
}

func newFileInDirectory() {
	files := tk.GetOpenFile(tk.Filetypes(filetypes.GetTkTypes(validFileTypes)), tk.Multiple(false))
	if len(files) < 1 || files[0] == "" {
		log.Println("no file chosen")
		return
	}
	file := strings.Join(files, " ") // GetOpenFile returns an array split on spaces!
	openFileAndDirectory(file)
}

func openFileAndDirectory(file string) {
	directoryState.currentFile = filepath.Base(file)
	directoryState.currentDirectory = filepath.Dir(file)
	dirfiles, err := os.ReadDir(directoryState.currentDirectory)
	if err != nil {
		log.Printf("could not open dir: %v", err)
		return
	}
	directoryState.images = []string{}
	for _, v := range dirfiles {
		if isImage(v) {
			directoryState.images = append(directoryState.images, v.Name())
		}
	}
	updateImage(file)
}

func newDirectory() {
	dir := tk.ChooseDirectory()
	if dir == "" {
		log.Println("no directory chosen")
		return
	}
	directoryState.currentDirectory = dir
	dirfiles, err := os.ReadDir(directoryState.currentDirectory)
	if err != nil {
		log.Println(err)
		return
	}
	directoryState.images = []string{}
	for _, v := range dirfiles {
		if isImage(v) {
			directoryState.images = append(directoryState.images, v.Name())
		}
	}
	updateImage(filepath.Join(directoryState.currentDirectory, directoryState.images[0]))
}

func updateImage(file string) {
	var i image.Image

	f, err := os.Open(file)
	if err != nil {
		log.Printf("error opening image: %v", err)
		return
	}
	defer f.Close()

	ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(file), "."))
	if checkErr(imaging.FormatFromExtension(ext)) {
		i, err = imaging.Decode(f, imaging.AutoOrientation(true))
	} else if ext == "webp" {
		i, err = webp.Decode(f)
	} else if ext == "tga" {
		i, err = tga.Decode(f)
	}
	if err != nil {
		log.Printf("error decoding image: %v", err)
		return
	}
	i = imaging.Fit(i,
		// -50 to give some space to breathe around the edges
		must(strconv.Atoi(tk.WinfoScreenWidth(tk.App)))-50,
		must(strconv.Atoi(tk.WinfoScreenHeight(tk.App)))-50,
		imaging.CatmullRom,
	)
	repaint(filepath.Base(file), tk.Data(i))
	directoryState.currentFile = filepath.Base(file)
}

func repaint(name string, data tk.Opt) {
	// TODO: sometimes, when going from a big image to a smaller one,
	// the window remains the same height as the big image,
	// even as the width shrinks to fit the smaller image.
	// This only seems to happen when the large image was full-screen height.
	img.Configure(tk.Image(tk.NewPhoto(data)))
	if name != "" {
		tk.App.WmTitle(fmt.Sprintf("why | %s", name))
	} else {
		tk.App.WmTitle("why")
	}
	tk.App.Center()
}

func destroyFileList(destroy bool) {
	if destroy {
		tk.Destroy(fileList)
	}
	fileList = nil
	lb = nil
	fileListBindVar.Set("0")
}

func constructFileList() {
	fileList = tk.Toplevel()
	fileList.WmTitle("Files")
	lb = fileList.Listbox(tk.Height(0))
	for i := range directoryState.images {
		lb.Insert("end", directoryState.images[i])
		if i == slices.Index(directoryState.images, directoryState.currentFile) {
			lb.SelectionSet(i)
		}
	}
	tk.Pack(lb)
	tk.Bind(lb, "<<ListboxSelect>>", tk.Command(func() {
		selection := lb.Curselection()
		updateImage(filepath.Join(directoryState.currentDirectory, directoryState.images[selection[0]]))
	}))
	tk.Bind(fileList, "<Destroy>", tk.Command(func(e *tk.Event) {
		// list closed by user click on <x>
		destroyFileList(false)
	}))
	fileListBindVar.Set("1")
}

func menuSelect() {
	if fileListBindVar.Get() == "1" && fileList == nil {
		constructFileList()
	} else if fileListBindVar.Get() == "0" && fileList != nil {
		destroyFileList(true)
	}
}

func moveSelectInFileList(target int) {
	if lb != nil {
		lb.SelectionClear("0", "end")
		lb.SelectionSet(target)
		lb.See(target)
	}
}

func keyPress(e *tk.Event) {
	curr := slices.Index(directoryState.images, directoryState.currentFile)
	switch e.Keysym {
	case ".":
		log.Printf("state: %+v", directoryState)
	case "o":
		newFileInDirectory()
	case "a":
		if fileList == nil {
			constructFileList()
		} else {
			destroyFileList(true)
		}
	case "Up", "Right":
		if curr > 0 {
			updateImage(filepath.Join(directoryState.currentDirectory, directoryState.images[curr-1]))
			moveSelectInFileList(curr - 1)
		}
	case "Down", "Left":
		if curr < len(directoryState.images)-1 && curr != -1 {
			updateImage(filepath.Join(directoryState.currentDirectory, directoryState.images[curr+1]))
			moveSelectInFileList(curr + 1)
		}
	}
}

func main() {
	tk.App.IconPhoto(tk.NewPhoto(tk.Data(icon)))
	tk.MacOpenDocument(openFileAndDirectory)

	menubar := tk.Menu()
	fileMenu := menubar.Menu()
	fileMenu.AddCommand(tk.Lbl("Open File"), tk.Accelerator("O"), tk.Command(newFileInDirectory))
	fileMenu.AddCommand(tk.Lbl("Open Directory"), tk.Command(newDirectory))
	fileMenu.AddSeparator()
	checkbox := fileMenu.AddCheckbutton(tk.Lbl("Show Filelist"))

	fileMenu.EntryConfigure(checkbox, fileListBindVar)
	menubar.AddCascade(tk.Lbl("File"), tk.Underline(0), tk.Mnu(fileMenu))
	tk.App.Configure(tk.Mnu(menubar))

	tk.Bind(fileMenu, "<<MenuSelect>>", tk.Command(menuSelect))
	tk.Bind(tk.App, "<KeyPress>", tk.Command(keyPress))
	// todo: resize image based on scroll events
	// tk.Bind(tk.App, "<TouchpadScroll>", tk.Command(func(e *tk.Event) {
	// 	log.Printf("%v, %v", int16(e.Delta>>16), int16(e.Delta&0xFFFF))
	// }))

	repaint("", tk.Data(noise))
	tk.Pack(img)
	tk.App.Center()
	tk.App.Wait()
}