import os
from flask import Flask, render_template, request, flash, redirect, session, url_for
from flask_wtf import FlaskForm
from wtforms.fields.html5 import DateField, EmailField
from wtforms.fields import StringField, BooleanField
from wtforms.validators import DataRequired, ValidationError, EqualTo
from flask_sqlalchemy import SQLAlchemy
from flask_security import Security, SQLAlchemyUserDatastore, auth_required, hash_password, uia_email_mapper, current_user
from flask_security.models import fsqla_v2 as fsqla
from flask_security.forms import LoginForm, Required, PasswordField
from flask_security.utils import find_user, verify_password
from flask_mail import Mail
from email_validator import validate_email
import bleach
import ldap3
from ldap3.core.exceptions import LDAPBindError, LDAPSocketOpenError
from pathlib import Path
import logging

from datetime import date
from .door_handle import DoorHandle


def validate_valid_thru_date(form, field):
    if form.limit_validity.data:  # only check date format if limited validity of token is set
        try:
            if not field.data >= date.today():
                raise ValueError
        except ValueError as e:
            flash("Ungültiges Datum")
            raise ValidationError
    return True


class TokenForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired()])
    email = EmailField('E-Mail', validators=[DataRequired()])
    organization = StringField('Organization', validators=[DataRequired()])
    limit_validity = BooleanField('Gültigkeit begrenzen?')
    valid_thru = DateField('Gültig bis', validators=[validate_valid_thru_date])
    active = BooleanField('Aktiv?')
    dsgvo = BooleanField('Einwilligung Nutzungsbedingungen erfragt?', validators=[DataRequired()])

class TokenDeleteForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired(), EqualTo('name_confirm', 'Name stimmt nicht überein')])
    name_confirm = StringField('Name confirm')

def uia_username_mapper(identity):
    # we allow pretty much anything - but we bleach it.
    return bleach.clean(identity, strip=True)

def create_application(config):
    # set up logging for the web app
    logger = logging.getLogger('webapp')
    logger.setLevel(logging.INFO)

    if config.log_file is not None:
        ch = logging.FileHandler(config.log_file)
        ch.setLevel(logging.INFO)
    else:
        # create console handler and set level to debug
        ch = logging.StreamHandler()
        ch.setLevel(logging.DEBUG)
    # create formatter
    formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
    # add formatter to ch
    ch.setFormatter(formatter)
    # add ch to logger
    logger.addHandler(ch)

    # do some checks for file existence etc.
    if not Path(config.template_folder).exists():
        logger.error(f'Flask template folder not found at {config.template_folder}')
    if not Path(config.static_folder).exists():
        logger.error(f'Flask static folder not found at {config.static_folder}')
    if not Path(config.token_file).exists():
        logger.warning(f"Token file not found at {config.token_file}")

    new_admin_data = []
    if config.admin_file is not None:
        if not Path(config.admin_file).exists():
            logger.warning(f"Admin user creation file not found at {config.admin_file}")
        else:
            # store data for new admins in memory s.t. the file can be deleted afterwards
            with open(config.admin_file) as f:
                for i, d in enumerate(f.readlines()):
                    try:
                        user, email, pw = d.split()
                        validate_email(email)
                        new_admin_data.append({'username': user, 'email': email, 'password': pw})
                    except Exception as e:
                        print(f"Error while parsing line {i} in admin config file. Config file should contain lines of "
                              f"'<username> <email> <password>\\n'\n Exception: {e}\nAdmin account could not be created.")

    # create door objects which provides access to the token file and current door state via MQTT
    door = DoorHandle(token_file=config.token_file, mqtt_host=config.mqtt_host, nfc_socket=config.nfc_socket,
                      logger=logger)

    app = Flask(__name__, template_folder=config.template_folder, static_folder=config.static_folder)

    # Generate a nice key using secrets.token_urlsafe()
    app.config['SECRET_KEY'] = os.environ.get("SECRET_KEY", 'Q7PJu2fg2jabYwP-Psop6c6f2G4')
    # Bcrypt is set as default SECURITY_PASSWORD_HASH, which requires a salt
    # Generate a good salt using: secrets.SystemRandom().getrandbits(128)
    app.config['SECURITY_PASSWORD_SALT'] = os.environ.get("SECURITY_PASSWORD_SALT",
                                                          '10036796768252925167749545152988277953')

    app.config['SECURITY_USER_IDENTITY_ATTRIBUTES'] = [
        {"email": {"mapper": uia_email_mapper, "case_insensitive": True}},
        {"username": {"mapper": uia_username_mapper}}
    ]
    app.config['SECURITY_CHANGEABLE'] = True
    app.config['SECURITY_RECOVERABLE'] = True
    app.config['SECURITY_SEND_PASSWORD_CHANGE_EMAIL'] = False

    # Mail Config
    app.config['MAIL_SERVER'] = config.mail_server
    app.config['MAIL_PORT'] = config.mail_port
    app.config['MAIL_USE_TLS'] = config.mail_use_tls
    app.config['MAIL_USE_SSL'] = config.mail_use_ssl
    app.config['MAIL_USERNAME'] = config.mail_username
    app.config['MAIL_PASSWORD'] = config.mail_password
    app.config['MAIL_DEFAULT_SENDER'] = app.config['MAIL_USERNAME']
    mail = Mail(app)

    app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///admin.db'
    # As of Flask-SQLAlchemy 2.4.0 it is easy to pass in options directly to the
    # underlying engine. This option makes sure that DB connections from the
    # pool are still valid. Important for entire application since
    # many DBaaS options automatically close idle connections.
    app.config["SQLALCHEMY_ENGINE_OPTIONS"] = {
        "pool_pre_ping": True,
    }

    # Create database connection object
    db = SQLAlchemy(app)

    # Define models
    fsqla.FsModels.set_db_info(db)

    class Role(db.Model, fsqla.FsRoleMixin):
        pass

    class User(db.Model, fsqla.FsUserMixin):
        username = db.Column(db.String(255))

    # LDAP
    ldap_server = ldap3.Server(config.ldap_url)
    local_ldap_cache = {}   # dict for caching LDAP authorization locally (stores username + hashed password)

    def validate_ldap(user, password):
        """Validate the user and password through an LDAP server.

        If the connection completes successfully the given user and password is authorized and the password is stored
        locally for future authorization without internet connectivity.
        If the server is not reachable we check the password against a locally stored password (if the user previously
        authorized through LDAP).

        Parameters
        ----------
        user     :  username for the LDAP server
        password :  password for the LDAP server

        Returns
        -------
            bool : result of the authorization process (True = success, False = failure)
        """

        try:
            con = ldap3.Connection(ldap_server, user="uid=%s,ou=Users,dc=imaginaerraum,dc=de" % (user.username,),
                                    password=password, auto_bind=True)
        except ldap3.core.exceptions.LDAPBindError:
            # server reachable but user unauthorized -> fail
            return False
        except LDAPSocketOpenError:
            # server not reachable -> try cached authorization data
            return user.username in local_ldap_cache and verify_password(password, local_ldap_cache[user.username])
        except Exception:
            # for other Exceptions we just fail
            return False

        # TODO check if user has permission to edit tokens
        # if LDAP authorization succeeds we cache the password locally (in memory) to allow LDAP authentication even if
        # the server is not reachable
        local_ldap_cache[user.username] = hash_password(password)
        return True

    class ExtendedLoginForm(LoginForm):
        email = StringField('Benutzername oder E-Mail', [Required()])
        password = PasswordField('Passwort', [Required()])

        def validate(self):
            # try authorizing locally using Flask security user datastore
            authorized = super(ExtendedLoginForm, self).validate()

            if not authorized:
                # try authorizing using LDAP
                # authorization in LDAP uses username -> get username associated with email from the database
                user = find_user(self.email.data)
                authorized = validate_ldap(user, self.password.data)
                if authorized:
                    logger.info(f"Admin user with credentials '{self.email.data}' authorized through LDAP")
            else:
                logger.info(f"Admin user with credentials '{self.email.data}' authorized through local database")

            # if any of the authorization methods is successful we authorize the user
            return authorized

    # Setup Flask-Security
    user_datastore = SQLAlchemyUserDatastore(db, User, Role)
    security = Security(app, user_datastore, login_form=ExtendedLoginForm)

    # create admin users (only if they don't exists already)
    def create_admins(new_admin_data):
        for d in new_admin_data:
            if user_datastore.find_user(email=d['email'], username=d['username']) is None:
                logger.info(f"New admin user created with username '{d['username']}' and email '{d['email']}'")
                # create new admin (only if admin does not already exist)
                user_datastore.create_user(email=d['email'], username=d['username'], password=hash_password(d['password']))

    # Create a user to test with
    @app.before_first_request
    def create_user():
        db.create_all()
        if len(new_admin_data) > 0:
            # create admin accounts from given file
            create_admins(new_admin_data)
        db.session.commit()

    @app.route('/')
    def door_lock():
        return render_template('index.html', door_state=door.state, encoder_position=door.encoder_position)


    @app.route('/tokens')
    @auth_required()
    def list_tokens():
        tokens = door.get_tokens()
        assigned_tokens = {t: data for t, data in tokens.items() if not data['inactive']}
        inactive_tokens = {t: data for t, data in tokens.items() if data['inactive']}
        return render_template('tokens.html', assigned_tokens=assigned_tokens, inactive_tokens=inactive_tokens)


    @app.route('/register-token', methods=['GET', 'POST'])
    @auth_required()
    def register():
        """Register new token for locking and unlocking the door.

        This route displays the most recently scanned invalid token as reported in the logfile and provides a form for
        entering user info (name, email, valid thru date (optional)) for the new token.

        If the route is called via POST the provided form data is checked and if the check succeeds the /store-token route
        will be called which adds the new token to the database.
        """
        form = TokenForm()
        if request.method == 'GET':
            # set default valid thru date to today to make sure form validity check passes
            # (will not be used if limited validity is disabled)
            form.valid_thru.data = date.today()
            return render_template('register.html', token=door.get_most_recent_token(), form=form)
        elif request.method == 'POST' and form.validate():
            # store data in session cookie
            session['token'] = door.get_most_recent_token()['token']
            session['name'] = form.name.data
            session['email'] = form.email.data
            session['organization'] = form.organization.data
            if form.limit_validity.data:
                session['valid_thru'] = form.valid_thru.data.isoformat()
            else:
                session['valid_thru'] = ''
            session['inactive'] = not form.active.data
            return redirect(f'/store-token')
        else:
            return render_template('register.html', token=door.get_most_recent_token(), form=form)


    @app.route('/edit-token/<token>', methods=['GET', 'POST'])
    @auth_required()
    def edit_token(token):
        """Edit data in the token file (name, email, valid_thru date, active/inactive).

        If the route is accessed via GET it will provide a form for editing the currently stored data for the user.
        If the route is accessed via POST it will check if the form data is good and then store the modified user data in
        the database (by redirecting to the /store-token route)

        Parameters
        ----------
        token : str
            The token for which data should be edited.
        """
        form = TokenForm(request.form)
        form.dsgvo.validators = []  # we skip the validation of the DSGVO checkbox here because we assume the user agreed
                                    # to it before
        if request.method == 'GET':
            tokens = door.get_tokens()
            if token in tokens:
                # set default for form according to values from the token file
                et = tokens[token]
                form.active.data = not et['inactive']
                form.name.data = et['name'] if et['name'] else ''
                form.email.data = et['email'] if et['email'] else ''
                form.organization.data = et['organization'] if et['organization'] else ''

                # for the valid thru date we use today's date in case there is not valid date in the database
                try:
                    form.valid_thru.data = date.fromisoformat(et['valid_thru'])
                    form.limit_validity.data = True
                except Exception:
                    form.valid_thru.data = date.today()

                return render_template('edit.html', token=token, form=form)
            else:
                # flash an error message if the route is accessed with an invalid token
                flash(f'Ausgewaehlter Token {token} in Tokenfile nicht gefunden.')
                return redirect('/tokens')
        elif request.method == 'POST':
            if form.validate():
                # store data in session cookie
                session['token'] = token
                session['name'] = form.name.data
                session['organization'] = form.organization.data
                session['email'] = form.email.data
                if form.limit_validity.data:
                    session['valid_thru'] = form.valid_thru.data.isoformat()
                else:
                    session['valid_thru'] = ''
                session['inactive'] = not form.active.data
                return redirect(f'/store-token')
            else:
                return render_template('edit.html', token=token, form=form)


    @app.route('/store-token')
    @auth_required()
    def store_token():
        """Store token to the token file on disk.

        This will use the token id and the associated data stored in the session cookie (filled by register_token() or
         edit_token()) and create/modify a token and store the new token file to disk.
        """
        token = session['token']
        tokens = door.get_tokens()
        tokens[token] = {'name': session['name'],
                         'email': session['email'],
                         'valid_thru': session['valid_thru'],
                         'inactive': session['inactive'],
                         'organization': session['organization']}
        try:
            door.store_tokens(tokens)
            logger.info(f"Token {token} stored in database by admin user {current_user.username}")
        except Exception as e:
            flash(f"Error during store_tokens. Exception: {e}")
        return redirect('/tokens')


    @app.route('/delete-token/<token>', methods=['GET', 'POST'])
    @auth_required()
    def delete_token(token):
        """Delete the given token from the token file and store the new token file to disk

        Parameters
        ----------
        token : str
            The token to delete from the database.
        """
        tokens = door.get_tokens()

        if token in tokens:
            token_to_delete = tokens[token]

            # set up form for confirming deletion
            form = TokenDeleteForm()
            form.name_confirm.data = token_to_delete['name']

            if request.method == 'GET':
                # return page asking the user to confirm delete
                return render_template('delete.html', token=token_to_delete, form=form)
            elif form.validate():
                # form validation successful -> can delete the token
                tokens.pop(token)
                try:
                    door.store_tokens(tokens)
                    logger.info(f"Token {token} was deleted from database by admin user {current_user.username}")
                except Exception as e:
                    flash(f"Error during store_tokens. Exception: {e}")
                flash(f"Token {token} wurde gelöscht!")
                return redirect('/tokens')
            else:
                # form validation failed -> return to token overview and flash message
                flash(f"Der eingegebene Name stimmt nicht überein. Der Token {token} von {token_to_delete['name']} wurde nicht gelöscht.")
                return redirect('/tokens')
        else:
            flash(f'Ungültiger Token {token} für Löschung.')
            return redirect('/tokens')


    @app.route('/deactivate-token/<token>')
    @auth_required()
    def deactivate_token(token):
        """Deactivate access for the given token. This updates the token file on disk.

        Parameters
        ----------
        token : str
            The token to deactivate.
        """
        tokens = door.get_tokens()
        if token in tokens:
            tokens[token]['inactive'] = True
            try:
                door.store_tokens(tokens)
                logger.info(f"Token {token} deactivated by admin user {current_user.username}")
            except Exception as e:
                flash(f"Error during store_tokens. Exception: {e}")
        return redirect('/tokens')

    @app.route('/open')
    @auth_required()
    def open_door():
        try:
            door.open_door()
            logger.info(f"Door opened by admin user {current_user.username}")
        except Exception as e:
            flash(f'Could not open door. Exception: {e}')
        return redirect('/')

    @app.route('/close')
    @auth_required()
    def close_door():
        try:
            door.close_door()
            logger.info(f"Door closed by admin user {current_user.username}")
        except Exception as e:
            flash(f'Could not close door. Exception: {e}')
        return redirect('/')

    return app