#!/usr/bin/env python
from pprint import pprint
from pathlib import Path
import tkinter as tk
import tkinter.filedialog
from functools import partial
from PIL import ImageTk,Image


def pack(what, *args, **kwargs):
    '''replacement for tkinters object.pack() method, returning the object'''
    what.pack(*args, **kwargs)
    return what


class MainWin(tk.Tk):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.title('Mein Titel ;-)')
        self.menubar = tk.Menu(self)
        self.config(menu=self.menubar)
        self.filemenu = tk.Menu(self.menubar, tearoff=False)
        self.menubar.add_cascade(label='File', menu=self.filemenu)
        self.filemenu.add_command(label='Open', command=self.open)
        self.filemenu.add_command(label='Exit', command=self.destroy)
        self.navimenu = tk.Menu(self.menubar, tearoff=False)
        self.menubar.add_cascade(label='Navigation', menu=self.navimenu)
        self.navimenu.add_command(label='Next', command=partial(self.navi, True))
        self.navimenu.add_command(label='Previous', command=partial(self.navi, False))
        self.filename = pack(tk.Label(self, relief=tk.SUNKEN), side=tk.TOP, fill=tk.X)
        self.canvas = pack(tk.Canvas(self), side=tk.TOP, fill=tk.BOTH, expand=True)
        self.bind('n', lambda event: self.navi(True))
        self.bind('<Right>', lambda event: self.navi(True))
        self.bind('<Left>', lambda event: self.navi(False))
        self.bind('p', lambda event: self.navi(False))
        self.bind('o', lambda event: self.open())
        self.bind('<Configure>', self.on_resize)
        self.files = list()
        self.index = 0
        self.image = None


    def on_resize(self, *args, **kwargs):
        self.display_file()


    def open(self, *args, **kwargs):
        directory = Path(tk.filedialog.askdirectory(master=self, title='Verzeichnis?', initialdir='/home/luke/Downloads'))
        self.files = sorted([f for f in directory.iterdir()
                             if f.is_file()
                             and (str(f).lower().endswith('.jpg')
                                  or str(f).lower().endswith('.jpeg')
                                  or str(f).lower().endswith('.png')
                                  or str(f).lower().endswith('.gif'))])
        self.display_file()


    def navi(self, go_up, *args, **kwargs):
        if not self.files:
            tk.messagebox.showwarning(title='No images loaded', message='No images were loaded, please use File->Open first')
            return
        if go_up:
            if self.index < len(self.files):
                self.index += 1
        else:
            if self.index > 0:
                self.index -=1
        self.display_file()


    def display_file(self):
        self.canvas.update()
        width = self.canvas.winfo_width()
        height = self.canvas.winfo_height()
        filepath = self.files[self.index]
        pilimage = Image.open(filepath)
        pilimage.thumbnail((width, height), Image.ANTIALIAS)
        img = ImageTk.PhotoImage(image=pilimage)
        self.canvas.create_image(1, 1, anchor=tk.NW, image=img)
        self.canvas.image = img
        self.filename.config(text=str(filepath.name))

        
if __name__ == '__main__':
    MainWin().mainloop()