from datetime import datetime
from itsdangerous import Signer
from flask import (Flask, request, url_for, redirect, g, render_template, session, abort)
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config.from_pyfile('config.cfg')
db = SQLAlchemy(app)

def url_for_other_page(page):
   args = request.view_args.copy()
   args['page'] = page
   return url_for(request.endpoint, **args)
app.jinja_env.globals['url_for_other_page'] = url_for_other_page

@app.before_request
def check_user_status():
   g.user = None
   if 'user_id' in session:
      g.user = User.query.get(session['user_id'])

class Paste(db.Model):
   id = db.Column(db.Integer, primary_key=True)
   code = db.Column(db.Text)
   title = db.Column(db.Text)
   pub_date = db.Column(db.DateTime)
   user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
   is_private = db.Column(db.Boolean)
   parent_id = db.Column(db.Integer, db.ForeignKey('paste.id'))
   parent = db.relationship('Paste', lazy=True, backref='children', uselist=False, remote_side=[id])

   def __init__(self, user, code, title, parent=None, is_private=False):
      self.user = user
      self.code = code
      self.title = title
      self.is_private = is_private
      self.pub_date = datetime.utcnow()
      self.parent = parent

class User(db.Model):
   id = db.Column(db.Integer, primary_key=True)
   display_name = db.Column(db.String(120))
   fb_id = db.Column(db.String(30), unique=True)
   pastes = db.relationship(Paste, lazy='dynamic', backref='user')

@app.route('/', methods=['GET', 'POST'])
def new_paste():
   parent = None
   reply_to = request.args.get('reply_to', type=int)
   if reply_to is not None:
      parent = Paste.query.get(reply_to)
   if request.method == 'POST' and request.form['code']:
      is_private = bool(request.form.get('is_private'))
      title = "Untitled paste"
      if request.form['pastetitle'] and request.form['pastetitle'] != "Enter title here":
         title = request.form['pastetitle']
      paste = Paste(g.user, request.form['code'], title, parent=parent, is_private=is_private)
      db.session.add(paste)
      db.session.commit()
      sign = Signer(app.secret_key, salt='jackson').sign(str(paste.id)) \
         if is_private else None
      return redirect(url_for('show_paste', paste_id=paste.id, s=sign))
   return render_template('new_paste.html', parent=parent)

@app.route('/<int:paste_id>/')
@app.route('/<int:paste_id>')
def show_paste(paste_id):
   paste = Paste.query.options(db.eagerload('children')).get_or_404(paste_id)
   if paste.is_private:
      try:
         sign = request.args.get('s', '')
         assert str(paste.id) == \
            Signer(app.secret_key, salt='jackson').unsign(sign).decode("utf-8")
      except:
         abort(403)
   return render_template('show_paste.html', paste=paste)