import time
import praw

CONFIG_INTERVAL      = 30 # Number of seconds between updating
CONFIG_CLIENT_ID     = "" # Client ID from /prefs/apps
CONFIG_CLIENT_SECRET = "" # Client secret from /prefs/apps
CONFIG_USERNAME      = "" # Username for the bot account
CONFIG_PASSWORD      = "" # Password for the bot account
CONFIG_SUBREDDIT     = "" # Subreddit(s) the script runs on
CONFIG_SCRIPTHOST    = "" # Your Reddit username
CONFIG_USER_AGENT    = "postsubscribe 1.0 for /r/%s, hosted by /u/%s" \
                       %(CONFIG_SUBREDDIT, CONFIG_SCRIPTHOST)
CONFIG_SUB_SUBJECT   = 'Subscribe me!' # Subject users put to subscribe
CONFIG_SUB_NOTIFY    = 'Subscribed!' # Subject use to confirm subscription
CONFIG_SUB_MSG       = 'You are now subscribed to new posts.'
CONFIG_UNSUB_SUBJECT = 'Unsubscribe me!' # Subject users put to unsubscribe
CONFIG_UNSUB_NOTIFY  = 'Unsubscribed!' # Subject use to confirm unsubscription
CONFIG_UNSUB_MSG     = 'You are now unsubscribed to new posts.'
CONFIG_NOTIFY_SUB    = 'New post from /u/%s' # Subject of notification.
CONFIG_NOTIFY_MSG    = "Here's my latest post: [%s](%s)" # Body of notification
CONFIG_USERS_FILE    = 'users.txt' # file to read usernames from
CONFIG_LASTPOST_FILE = 'last_post.txt' # file to read last post ID from

# For CONFIG_NOTIFY_SUB, %s should exist once, where you would like your
# username to show in the subject line.
# For CONFIG_NOTIFY_MSG, the first %s is the title of your post, and the
# second is the direct link. I recommend leaving it as [%s](%s) to create
# a proper markdown link.

def log(msg):
    print('[%s] %s'%(time.ctime(), msg))

def poll_messages(reddit, users):
    new_users = set()
    new_users.update(users)
    unread = []
    for item in reddit.inbox.unread(limit=None):
        if isinstance(item, praw.models.Message):
            unread.append(item)
    log('Found %d unread message(s).'%len(unread))
    reddit.inbox.mark_read(unread)
    for msg in unread:
        user = msg.author
        usern = user.name
        if msg.subject == CONFIG_SUB_SUBJECT and not usern in new_users:
            new_users.add(usern)
            user.message(CONFIG_SUB_NOTIFY, CONFIG_SUB_MSG)
            log('User /u/%s has subscribed!'%usern)
        elif msg.subject == CONFIG_UNSUB_SUBJECT and usern in new_users:
            new_users.discard(usern)
            user.message(CONFIG_UNSUB_NOTIFY, CONFIG_UNSUB_MSG)
            log('User /u/%s has unsubscribed.'%usern)
    return new_users

def send_to_subscribed(reddit, users, post):
    msg = CONFIG_NOTIFY_MSG%(post.title, post.url)
    sub = CONFIG_NOTIFY_SUB%(CONFIG_SCRIPTHOST)
    for u in users:
        reddit.redditor(u).message(sub, msg)
        log('Notified /u/%s of new post.'%u)

def most_recent_post(reddit, subr):
    sub = reddit.subreddit(subr)
    return list(sub.new(limit=1))[0]

def read(path):
    data = ''
    try:
        with open(path, 'r') as f:
            data = f.read().strip()
    except: pass
    return data

def write(path, data):
    try:
        with open(path, 'w') as f:
            f.write(data)
    except: pass

def read_subscribed(path):
    users = set()
    for u in read(path).splitlines():
        users.add(u)
    return users

def read_last_post(path):
    return read(path)

def write_subscribed(users):
    write(CONFIG_USERS_FILE, '\n'.join(users))

def write_last_post(postid):
    write(CONFIG_LASTPOST_FILE, postid)

def main():
    log('Reading subscribed users...')
    users = read_subscribed('users.txt')
    log('Reading last post...')
    last_post = read_last_post('last_post.txt')
    log('Authenticating with Reddit...')
    reddit = praw.Reddit(client_id = CONFIG_CLIENT_ID,
                         client_secret = CONFIG_CLIENT_SECRET,
                         username = CONFIG_USERNAME,
                         password = CONFIG_PASSWORD,
                         user_agent = CONFIG_USER_AGENT)
    while True:
        log('Polling messages...')
        new_users = poll_messages(reddit, users)
        if users != new_users:
            log('Subscribed users changed, re-writing file...')
            write_subscribed(new_users)
            users = new_users
        log('Getting last post...')
        recent = most_recent_post(reddit, CONFIG_SUBREDDIT)
        if recent.name != last_post:
            log('A new post was found! Notifying users...')
            send_to_subscribed(reddit, users, recent)
            log('Re-writing post file...')
            write_last_post(recent.name)
            last_post = recent.name
        else:
            log('No new posts.')
        log('Sleeping for %d seconds...'%CONFIG_INTERVAL)
        time.sleep(CONFIG_INTERVAL)

if __name__ == '__main__':
    main()