"""
Script shall be called every X minutes. Pseudocode:
get catalog at http://a.4cdn.org/ic/catalog.json
for each thread with prefix "/las/" and "last_modified" greater than locally saved:
    get thread at http://a.4cdn.org/ic/thread/{threadnumber}.json
    for each new reply:
        if name, image and securetrip are valid:
            if name isn't already used:
                create folder (name!!securetrip)
            if folder exists (thus securetrip is valid):
                add image to the folder ({timestamp in millis}.{ext})
"""

import requests, re, os

USER_DIR = "users/"
STATE_FILE = "state.txt"
BOARD = "ic"
GENERAL_PREFIX = "/las/"

def get(url):
    return requests.get(url).json()

def get_catalog(board):
    catalog = get("http://a.4cdn.org/{}/catalog.json".format(board))
    threads = []
    for page in catalog:
        threads.extend(page["threads"])
    return threads

def get_thread(board, thread):
    return get("http://a.4cdn.org/{}/thread/{}.json".format(board, thread))["posts"]

def get_new_posts(board, thread, time):
    return [post for post in get_thread(board, thread) if post["time"] > time]

def load_state():
    try:
        with open(STATE_FILE, "r") as file:
            return tuple(int(time) for time in file.read().split(" "))
    except FileNotFoundError:
        return (0, 0)

def save_state(last_report, last_update):
    with open(STATE_FILE, "w") as file:
        file.write("{} {}".format(last_report, last_update))

def is_name_valid(name):
    return name is not "Anonymous" and re.match(r"^[a-zA-Z0-9 \-_]{1,32}$", name)

def is_submission(post):
    return "name" in post and is_name_valid(post["name"]) and "trip" in post and post["trip"].startswith("!!") and "tim" in post

def load_users():
    if not os.path.exists(USER_DIR):
        os.makedirs(USER_DIR)
    users = {}
    for dir in os.listdir(USER_DIR):
        tokens = dir.split("!!")
        users[tokens[0]] = "!!" + tokens[1]
    return users

def save_remote_file(url, path):
    if not os.path.exists(path):
        request = requests.get(url, stream=True)
        if request.status_code == 200:
            with open(path, 'wb') as file:
                for chunk in request.iter_content(1024):
                    file.write(chunk)
        else:
            print("FAILED: {} {} {}".format(url, path, request.status_code))

def merge_user(users, name, trip):
    if name not in users:
        users[name] = trip
        return True
    else:
        return users[name] == trip

def merge_submission(board, post):
    path = USER_DIR + post["name"] + post["trip"]
    if not os.path.exists(path):
        os.makedirs(path)
    filename = "{}{}".format(post["tim"], post["ext"])
    save_remote_file("http://i.4cdn.org/{}/{}".format(board, filename), path + "/" + filename)

if __name__ == "__main__":
    last_report, last_update = load_state()
    users = load_users()

    current = last_update
    for thread in get_catalog(BOARD):
        if "sub" in thread and thread["sub"].startswith(GENERAL_PREFIX) and thread["last_modified"] > current:
            last_update = max(last_update, thread["last_modified"])
            print("UPDATE: {} at {}".format(thread["no"], thread["last_modified"]))
            for post in get_new_posts(BOARD, thread["no"], current):
                if is_submission(post) and merge_user(users, post["name"], post["trip"]):
                    merge_submission(BOARD, post)

    save_state(last_report, last_update)