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

## ripped from https://stackoverflow.com/questions/183042/how-can-i-use-uuids-in-sqlalchemy/812363#812363
from sqlalchemy import types
from sqlalchemy.dialects.mysql.base import MSBinary
from sqlalchemy.schema import Column
import uuid
class UUID(types.TypeDecorator):
   impl = MSBinary
   def __init__(self):
      self.impl.length = 16
      types.TypeDecorator.__init__(self,length=self.impl.length)
   def process_bind_param(self,value,dialect=None):
      if value and isinstance(value,uuid.UUID):
         return value.bytes
      elif value and not isinstance(value,uuid.UUID):
         raise ValueError('value %s is not a valid uuid.UUID' % value)
      else:
         return None
   def process_result_value(self,value,dialect=None):
      if value:
         return uuid.UUID(bytes=value)
      else:
         return None
   def is_mutable(self):
      return False
id_column_name = "id"
def id_column():
    return Column(id_column_name,UUID(),primary_key=True,default=uuid.uuid4)

def get_signed(string, salt="blank"):
   return Signer(app.secret_key, salt=salt).sign(str(string))

def get_unsigned(string, salt="blank"):
   return Signer(app.secret_key, salt=salt).unsign(str(string)).decode("utf-8")

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.jinja_env.globals['appname'] = app.config['APPNAME']

def refresh_string(delay,url):
   """
   Returns a string for html content for redirecting the user back after the
   requested delay, to the requested url.
   """
   return f'<meta http-equiv="Refresh" content="{delay}; url={url}">'

@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 = id_column()
   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(UUID(), 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')
   if reply_to is not None:
      try:
         parent = Paste.query.get(uuid.UUID(reply_to))
      except:
         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 = get_signed(paste.id, salt=app.config['SALT']) \
         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('/<paste_id>/')
@app.route('/<paste_id>')
def show_paste(paste_id):
   try:
      paste = Paste.query.options(db.eagerload('children')).get_or_404(paste_id)
   except:
      paste = Paste.query.options(db.eagerload('children')).get_or_404(uuid.UUID(paste_id))
   if paste.is_private:
      try:
         sign = request.args.get('s', '')
         assert str(paste.id) == \
            get_unsigned(sign, salt=app.config['SALT'])
      except:
         abort(403)
   parent = None
   if paste.parent_id:
      try:
         parent = Paste.query.get(uuid.UUID(paste.parent_id))
      except:
         parent = Paste.query.get(paste.parent_id)
   children = []
   if paste.children:
      for i in paste.children:
         j = None
         try:
            j = Paste.query.get(uuid.UUID(i.id))
         except:
            j = Paste.query.get(i.id)
         if j:
            k = j.id, j.title
            children.append(k)
   return render_template('show_paste.html', paste=paste, parent=parent, children=children)

@app.route('/<paste_id>/delete/', methods=['POST'])
@app.route('/<paste_id>/delete', methods=['POST'])
def delete_paste(paste_id):
   try:
      paste = Paste.query.options(db.eagerload('children')).get_or_404(paste_id)
   except:
      paste = Paste.query.options(db.eagerload('children')).get_or_404(uuid.UUID(paste_id))
   sign = str(request.form['s'])
   try:
      assert str(paste.id) == get_unsigned(sign, salt=app.config['DELETESALT'])
   except:
      abort(403)
   try:
      Paste.query.filter(Paste.id == paste.id).delete()
      db.session.commit()
      message = refresh_string(1, url_for("admin")) + "OK"
      return message,200
   except:
      return f"failure to delete object. Select <a href='{url_for('admin')}'>here</a> to return to the admin panel.",500

def get_all_pastes():
   """
   Get custom arrangement of pastes for Admin view
   """
   all1 = Paste.query.all()
   all2 = []
   for p1 in all1:
      parent_id = None
      parent_title = None
      children = []
      if p1.parent_id:
         parent_id = p1.parent_id
         try:
            parent_title = Paste.query.get(p1.parent_id).title
         except:
            parent_title = "" # works better than None for the parent column of the generated html
      if p1.children:
         for c1 in p1.children:
            child = Paste.query.get(c1.id)
            child_title = child.title
            c2 = c1.id, child_title
            children.append(c2)
      private = None
      if p1.is_private:
         private = get_signed(p1.id, salt=app.config['SALT'])
      p2 = {
         "id": p1.id,
         "title": p1.title,
         "private": private,
         "user_id": p1.user_id,
         "is_private": p1.is_private,
         "parent": (parent_id, parent_title),
         "children": children,
         "delete": get_signed(p1.id, salt=app.config['DELETESALT']).decode("utf-8")
      }
      all2.append(p2)
   return all2

@app.route('/admin/')
@app.route('/admin')
def admin():
   all_pastes = get_all_pastes()
   return render_template('admin.html', pastes = all_pastes)