from datetime import datetime
import unicodedata
import os
import subprocess
import time
import glob
from io import BytesIO
from pypdf import PdfReader, PdfWriter
from django import template
from django.template.loader import get_template
from django.conf import settings
from django.http import HttpResponse, HttpResponseRedirect
from wsgiref.util import FileWrapper
from PIL import Image


def find_template(template_name):
    for engine in template.engines.all():
        for loader in engine.engine.template_loaders:
            for origin in loader.get_template_sources(template_name):
                if os.path.exists(origin.name):
                    return origin.name
    raise template.TemplateDoesNotExist(f"Could not find template: {template_name}")


def media_path(fp):
    return os.path.join(os.path.join(settings.MEDIA_ROOT, "memberlists"), fp)


def media_dir():
    return os.path.join(settings.MEDIA_ROOT, "memberlists")


def serve_pdf(filename_pdf):
    # provide the user with the resulting pdf file
    with open(media_path(filename_pdf), 'rb') as pdf:
        response = HttpResponse(FileWrapper(pdf))#, content='application/pdf')
        response['Content-Type'] = 'application/pdf'
        response['Content-Disposition'] = 'attachment; filename='+filename_pdf

    return response


def render_tex(name, template_path, context, save_only=False):
    filename = name + "_" + datetime.today().strftime("%d_%m_%Y")
    filename = filename.replace(' ', '_').replace('&', '').replace('/', '_')
    # drop umlauts, accents etc.
    filename = unicodedata.normalize('NFKD', filename).encode('ASCII', 'ignore').decode()
    filename_tex = filename + '.tex'
    filename_pdf = filename + '.pdf'

    tmpl = get_template(template_path)
    res = tmpl.render(dict(context, creation_date=datetime.today().strftime('%d.%m.%Y')))

    if not os.path.exists(media_dir()):
        os.makedirs(media_dir())

    with open(media_path(filename_tex), 'w', encoding='utf-8') as f:
        f.write(res)

    # compile using pdflatex
    oldwd = os.getcwd()
    os.chdir(media_dir())
    subprocess.call(['pdflatex', '-halt-on-error',filename_tex])
    time.sleep(1)

    # do some cleanup
    for f in glob.glob('*.log'):
        os.remove(f)
    for f in glob.glob('*.aux'):
        os.remove(f)
    #os.remove(filename_tex)
    #os.remove(filename_table)

    os.chdir(oldwd)

    if save_only:
        return filename_pdf
    return serve_pdf(filename_pdf)


def fill_pdf_form(name, template_path, fields, attachments=[], save_only=False):
    filename = name + "_" + datetime.today().strftime("%d_%m_%Y")
    filename = filename.replace(' ', '_').replace('&', '').replace('/', '_')
    # drop umlauts, accents etc.
    filename = unicodedata.normalize('NFKD', filename).encode('ASCII', 'ignore').decode()
    filename_pdf = filename + '.pdf'

    path = find_template(template_path)

    if not os.path.exists(media_dir()):
        os.makedirs(media_dir())

    reader = PdfReader(path)
    writer = PdfWriter()

    writer.append(reader)

    writer.update_page_form_field_values(None, fields, auto_regenerate=False)

    for fp in attachments:
        try:
            if fp.endswith(".pdf"):
                # append pdf directly
                img_pdf = PdfReader(fp)
            else:
                # convert ensures that png files with an alpha channel can be appended
                img = Image.open(fp).convert("RGB")
                img_pdf = BytesIO()
                img.save(img_pdf, "pdf")
            writer.append(img_pdf)
        except Exception as e:
            print("Could not add image", fp)
            print(e)

    with open(media_path(filename_pdf), 'wb') as output_stream:
        writer.write(output_stream)

    if save_only:
        return filename_pdf
    return serve_pdf(filename_pdf)


def merge_pdfs(name, filenames, save_only=False):
    merger = PdfWriter()

    for pdf in filenames:
        merger.append(media_path(pdf))

    filename = name + "_" + datetime.today().strftime("%d_%m_%Y")
    filename = filename.replace(' ', '_').replace('&', '').replace('/', '_')
    filename = unicodedata.normalize('NFKD', filename).encode('ASCII', 'ignore').decode()
    filename_pdf = filename + ".pdf"
    merger.write(media_path(filename_pdf))
    merger.close()

    if save_only:
        return filename_pdf
    return serve_pdf(filename_pdf)