#!/usr/bin/python3
# -*- coding: UTF-8 -*-

# GET me using a web browser,
# executing my code with a Python interpreter called by a CGI-compliant webserver!
# Example URI:
#   http://www.example.org/path/main.py?title=title&author=author
# where:
#   title:
#       title of the book to filter (optional)
#   author:
#       author of the book to filter (optional)
#
#   Every parameter is optional.
#   Please note that not providing filters results in all books in the library.

# Useful libraries (no pun intended)
import xml.etree.ElementTree as ET
import json
import sys
import cgitb, cgi
import zipfile
from io import BytesIO
import shutil as sh
import os
import time
import logging
# Connection to remote library file
import requests
# Parsing of HTTP RFC 1123 datetime format
from email.utils import parsedate_to_datetime
# Our custom library (again no pun intended)
import tcparser
# Global variables and configurations
import glob

try:

    # Start the logging library (to avoid printing on stdout)
    # TODO
    logging.basicConfig(filename='conf/tpdf.log', level=logging.DEBUG)

    # Start CGI handling for webserver
    cgitb.enable()
    inputvars = cgi.FieldStorage()

    logging.debug("Started CGI")

    print('Content-Type: text/json; charset=utf-8')
    print('Access-Control-Allow-Origin: *')
    print()
    ### End of HTTP headers:  it is now safe to output things
    ##########################################################

    # Create output directory and temporary files if they do not exist
    if not os.path.exists(glob.conf['default']['outdir']):
        logging.debug("missing outdir, creating...")
        os.mkdir(glob.conf['default']['outdir'])
    if not os.path.exists(glob.conf['default']['outdir'] + '/lastupdate.txt'):
        logging.debug("missing lastupdate.txt, creating...")
        luh = open(glob.conf['default']['outdir'] + '/lastupdate.txt', 'w')
        luh.write('0')
        luh.close()

    # Retrieve last database update timestamp
    luh = open(glob.conf['default']['outdir'] + '/lastupdate.txt', 'r')
    try:
        lu = int(float(luh.read()))
    except ValueError:
        lu = 0
    luh.close()
    logging.info("last database update timestamp is %d" % lu)


    # Fetch last modified from HTTP header
    path = glob.conf['default']['path']
    user = glob.conf['default']['user']
    pswd = glob.conf['default']['pswd']
    req  = requests.head(path, auth=(user, pswd))

    logging.debug("fetched header from %s, returned code %d" % (path, req.status_code))

    cachefile = glob.conf['default']['outdir'] + "/tellico.xml"

    # If header fetch fails I can't update cache.
    # Try with current one, if exists
    if req.status_code == 200 and 'Last-modified' in req.headers:
        mtime = int(parsedate_to_datetime(req.headers['Last-modified']).timestamp())
        logging.info("Tellico last modified timestamp is %d" % mtime)

        # If local xml is out-of-date or missing, try download it
        if int(lu) < int(mtime) or not os.path.isfile(cachefile):
            logging.info("Out-of-date, updating")
            # Download Tellico .tc database
            req = requests.get(path, auth=(user, pswd))
            if req.status_code == 200 and req.content != None:    
                # Unzip Tellico .tc database and "cache it" locally
                zipHandler = zipfile.ZipFile(BytesIO(req.content), 'r')
                zipHandler.extractall(glob.conf['default']['outdir'])
                zipHandler.close()
                luh = open(glob.conf['default']['outdir'] + '/lastupdate.txt', 'w')
                luh.write(str(mtime))
                luh.close()
            else:
                logging.error("Update failed")

    # Get a Python-friendly library struct from XML file
    library = tcparser.getLibrary(cachefile, lu)

    ### Get filters to search for books ###
    try:
        title = inputvars['title'].value
    except KeyError:
        title = ''

    try:
        author = inputvars['author'].value
    except KeyError:
        author = ''


    result = tcparser.filter(library, title=title, author=author)

    # Wanna get a pretty JSON encoded library to do your nasty things offline at home? ;-)
    print(json.dumps(result, indent=4))

# Avoid printing on str{out,err} the unexpected exception traces. Log it instead.
except Exception as e:
    logging.exception(e)