var _              = require('lodash'),
    when           = require('when'),
    errors         = require('../errors'),
    nodefn         = require('when/node'),
    bcrypt         = require('bcryptjs'),
    Posts          = require('./post').Posts,
    ghostBookshelf = require('./base'),
    Role           = require('./role').Role,
    Permission     = require('./permission').Permission,
    http           = require('http'),
    crypto         = require('crypto'),
    validator      = require('validator'),

    tokenSecurity  = {},
    User,
    Users;

function validatePasswordLength(password) {
    try {
        if (!validator.isLength(password, 8)) {
            throw new Error('Your password must be at least 8 characters long.');
        }
    } catch (error) {
        return when.reject(error);
    }
    return when.resolve();
}

function generatePasswordHash(password) {
    // Generate a new salt
    return nodefn.call(bcrypt.genSalt).then(function (salt) {
        // Hash the provided password with bcrypt
        return nodefn.call(bcrypt.hash, password, salt);
    });
}

User = ghostBookshelf.Model.extend({

    tableName: 'users',

    saving: function (newPage, attr, options) {
        /*jshint unused:false*/

        var self = this;
        // disabling sanitization until we can implement a better version
        // this.set('name', this.sanitize('name'));
        // this.set('email', this.sanitize('email'));
        // this.set('location', this.sanitize('location'));
        // this.set('website', this.sanitize('website'));
        // this.set('bio', this.sanitize('bio'));

        ghostBookshelf.Model.prototype.saving.apply(this, arguments);

        if (this.hasChanged('slug') || !this.get('slug')) {
            // Generating a slug requires a db call to look for conflicting slugs
            return ghostBookshelf.Model.generateSlug(User, this.get('slug') || this.get('name'),
                {transacting: options.transacting})
                .then(function (slug) {
                    self.set({slug: slug});
                });
        }
    },

    toJSON: function (options) {
        var attrs = ghostBookshelf.Model.prototype.toJSON.call(this, options);
        // remove password hash for security reasons
        delete attrs.password;

        return attrs;
    },

    posts: function () {
        return this.hasMany(Posts, 'created_by');
    },

    roles: function () {
        return this.belongsToMany(Role);
    },

    permissions: function () {
        return this.belongsToMany(Permission);
    }

}, {
    /**
    * Returns an array of keys permitted in a method's `options` hash, depending on the current method.
    * @param {String} methodName The name of the method to check valid options for.
    * @return {Array} Keys allowed in the `options` hash of the model's method.
    */
    permittedOptions: function (methodName) {
        var options = ghostBookshelf.Model.permittedOptions(),

            // whitelists for the `options` hash argument on methods, by method name.
            // these are the only options that can be passed to Bookshelf / Knex.
            validOptions = {
                findOne: ['withRelated'],
                findAll: ['withRelated'],
                add: ['user'],
                edit: ['user', 'withRelated']
            };

        if (validOptions[methodName]) {
            options = options.concat(validOptions[methodName]);
        }

        return options;
    },

    /**
     * ### Find All
     *
     * @param options
     * @returns {*}
     */
    findAll:  function (options) {
        options = options || {};
        options.withRelated = _.union([ 'roles' ], options.include);
        return ghostBookshelf.Model.findAll.call(this, options);
    },

    /**
     * ### Find One
     * @extends ghostBookshelf.Model.findOne to include roles
     * **See:** [ghostBookshelf.Model.findOne](base.js.html#Find%20One)
     */
    findOne: function (data, options) {
        options = options || {};
        options.withRelated = _.union([ 'roles' ], options.include);

        return ghostBookshelf.Model.findOne.call(this, data, options);
    },

    /**
     * ### Edit
     * @extends ghostBookshelf.Model.edit to handle returning the full object
     * **See:** [ghostBookshelf.Model.edit](base.js.html#edit)
     */
    edit: function (data, options) {
        options = options || {};
        options.withRelated = _.union([ 'roles' ], options.include);

        return ghostBookshelf.Model.edit.call(this, data, options);
    },

    /**
     * ## Add
     * Naive user add
     * Hashes the password provided before saving to the database.
     *
     * @param {object} data
     * @param {object} options
     * @extends ghostBookshelf.Model.add to manage all aspects of user signup
     * **See:** [ghostBookshelf.Model.add](base.js.html#Add)
     */
    add: function (data, options) {
        var self = this,
            // Clone the _user so we don't expose the hashed password unnecessarily
            userData = this.filterData(data);

        options = this.filterOptions(options, 'add');
        options.withRelated = _.union([ 'roles' ], options.include);

        /**
         * This only allows one user to be added to the database, otherwise fails.
         * @param {object} user
         * @author javorszky
         */
        return validatePasswordLength(userData.password).then(function () {
            return self.forge().fetch();
        }).then(function () {
            // Generate a new password hash
            return generatePasswordHash(data.password);
        }).then(function (hash) {
            // Assign the hashed password
            userData.password = hash;
            // LookupGravatar
            return self.gravatarLookup(userData);
        }).then(function (userData) {
            // Save the user with the hashed password
            return ghostBookshelf.Model.add.call(self, userData, options);
        }).then(function (addedUser) {

            // Assign the userData to our created user so we can pass it back
            userData = addedUser;
            if (!data.role) {
                // TODO: needs change when owner role is introduced and setup is changed
                data.role = 1;
            }
            return userData.roles().attach(data.role);
        }).then(function (addedUserRole) {
            /*jshint unused:false*/
            // find and return the added user
            return self.findOne({id: userData.id}, options);
        });
    },

    permissable: function (userModelOrId, context, loadedPermissions, hasUserPermission, hasAppPermission) {
        var self = this,
            userModel = userModelOrId,
            origArgs;

        // If we passed in an id instead of a model, get the model
        // then check the permissions
        if (_.isNumber(userModelOrId) || _.isString(userModelOrId)) {
            // Grab the original args without the first one
            origArgs = _.toArray(arguments).slice(1);
            // Get the actual post model
            return this.findOne({id: userModelOrId}).then(function (foundUserModel) {
                // Build up the original args but substitute with actual model
                var newArgs = [foundUserModel].concat(origArgs);

                return self.permissable.apply(self, newArgs);
            }, errors.logAndThrowError);
        }

        if (userModel) {
            // If this is the same user that requests the operation allow it.
            hasUserPermission = hasUserPermission || context.user === userModel.get('id');
        }

        if (hasUserPermission && hasAppPermission) {
            return when.resolve();
        }

        return when.reject();
    },

    setWarning: function (user) {
        var status = user.get('status'),
            regexp = /warn-(\d+)/i,
            level;

        if (status === 'active') {
            user.set('status', 'warn-1');
            level = 1;
        } else {
            level = parseInt(status.match(regexp)[1], 10) + 1;
            if (level > 3) {
                user.set('status', 'locked');
            } else {
                user.set('status', 'warn-' + level);
            }
        }
        return when(user.save()).then(function () {
            return 5 - level;
        });
    },

    // Finds the user by email, and checks the password
    check: function (object) {
        var self = this,
            s;
        return this.getByEmail(object.email).then(function (user) {
            if (!user || user.get('status') === 'invited' || user.get('status') === 'inactive') {
                return when.reject(new Error('NotFound'));
            }
            if (user.get('status') !== 'locked') {
                return nodefn.call(bcrypt.compare, object.password, user.get('password')).then(function (matched) {
                    if (!matched) {
                        return when(self.setWarning(user)).then(function (remaining) {
                            s = (remaining > 1) ? 's' : '';
                            return when.reject(new Error('Your password is incorrect.<br>' +
                                remaining + ' attempt' + s + ' remaining!'));
                        });
                    }

                    return when(user.set({status : 'active', last_login : new Date()}).save()).then(function (user) {
                        return user;
                    });
                }, errors.logAndThrowError);
            }
            return when.reject(new Error('Your account is locked due to too many ' +
                'login attempts. Please reset your password to log in again by clicking ' +
                'the "Forgotten password?" link!'));

        }, function (error) {
            if (error.message === 'NotFound' || error.message === 'EmptyResponse') {
                return when.reject(new Error('There is no user with that email address.'));
            }

            return when.reject(error);
        });
    },

    /**
     * Naive change password method
     * @param {object} _userdata email, old pw, new pw, new pw2
     */
    changePassword: function (oldPassword, newPassword, ne2Password, options) {
        var self = this,
            userid = options.context.user,
            user = null;

        if (newPassword !== ne2Password) {
            return when.reject(new Error('Your new passwords do not match'));
        }

        return validatePasswordLength(newPassword).then(function () {
            return self.forge({id: userid}).fetch({require: true});
        }).then(function (_user) {
            user = _user;
            return nodefn.call(bcrypt.compare, oldPassword, user.get('password'));
        }).then(function (matched) {
            if (!matched) {
                return when.reject(new Error('Your password is incorrect'));
            }
            return nodefn.call(bcrypt.genSalt);
        }).then(function (salt) {
            return nodefn.call(bcrypt.hash, newPassword, salt);
        }).then(function (hash) {
            user.save({password: hash});
            return user;
        });
    },

    generateResetToken: function (email, expires, dbHash) {
        return this.getByEmail(email).then(function (foundUser) {
            if (!foundUser) {
                return when.reject(new Error('NotFound'));
            }

            var hash = crypto.createHash('sha256'),
                text = "";

            // Token:
            // BASE64(TIMESTAMP + email + HASH(TIMESTAMP + email + oldPasswordHash + dbHash ))

            hash.update(String(expires));
            hash.update(email.toLocaleLowerCase());
            hash.update(foundUser.get('password'));
            hash.update(String(dbHash));

            text += [expires, email, hash.digest('base64')].join('|');

            return new Buffer(text).toString('base64');
        });
    },

    validateToken: function (token, dbHash) {
        /*jslint bitwise:true*/
        // TODO: Is there a chance the use of ascii here will cause problems if oldPassword has weird characters?
        var tokenText = new Buffer(token, 'base64').toString('ascii'),
            parts,
            expires,
            email;

        parts = tokenText.split('|');

        // Check if invalid structure
        if (!parts || parts.length !== 3) {
            return when.reject(new Error("Invalid token structure"));
        }

        expires = parseInt(parts[0], 10);
        email = parts[1];

        if (isNaN(expires)) {
            return when.reject(new Error("Invalid token expiration"));
        }

        // Check if token is expired to prevent replay attacks
        if (expires < Date.now()) {
            return when.reject(new Error("Expired token"));
        }

        // to prevent brute force attempts to reset the password the combination of email+expires is only allowed for 10 attempts
        if (tokenSecurity[email + '+' + expires] && tokenSecurity[email + '+' + expires].count >= 10) {
            return when.reject(new Error("Token locked"));
        }

        return this.generateResetToken(email, expires, dbHash).then(function (generatedToken) {
            // Check for matching tokens with timing independent comparison
            var diff = 0,
                i;

            // check if the token length is correct
            if (token.length !== generatedToken.length) {
                diff = 1;
            }

            for (i = token.length - 1; i >= 0; i = i - 1) {
                diff |= token.charCodeAt(i) ^ generatedToken.charCodeAt(i);
            }

            if (diff === 0) {
                return when.resolve(email);
            }

            // increase the count for email+expires for each failed attempt
            tokenSecurity[email + '+' + expires] = {count: tokenSecurity[email + '+' + expires] ? tokenSecurity[email + '+' + expires].count + 1 : 1};
            return when.reject(new Error("Invalid token"));
        });
    },

    resetPassword: function (token, newPassword, ne2Password, dbHash) {
        var self = this;

        if (newPassword !== ne2Password) {
            return when.reject(new Error("Your new passwords do not match"));
        }

        return validatePasswordLength(newPassword).then(function () {
            // Validate the token; returns the email address from token
            return self.validateToken(token, dbHash);
        }).then(function (email) {
            // Fetch the user by email, and hash the password at the same time.
            return when.join(
                self.forge({email: email.toLocaleLowerCase()}).fetch({require: true}),
                generatePasswordHash(newPassword)
            );
        }).then(function (results) {
            // Update the user with the new password hash
            var foundUser = results[0],
                passwordHash = results[1];

            return foundUser.save({password: passwordHash, status: 'active'});
        });
    },

    gravatarLookup: function (userData) {
        var gravatarUrl = '//www.gravatar.com/avatar/' +
                crypto.createHash('md5').update(userData.email.toLowerCase().trim()).digest('hex') +
                "?d=404",
            checkPromise = when.defer();

        http.get('http:' + gravatarUrl, function (res) {
            if (res.statusCode !== 404) {
                userData.image = gravatarUrl;
            }
            checkPromise.resolve(userData);
        }).on('error', function () {
            //Error making request just continue.
            checkPromise.resolve(userData);
        });

        return checkPromise.promise;
    },

    // Get the user by email address, enforces case insensitivity rejects if the user is not found
    // When multi-user support is added, email addresses must be deduplicated with case insensitivity, so that
    // joe@bloggs.com and JOE@BLOGGS.COM cannot be created as two separate users.
    getByEmail: function (email) {
        // We fetch all users and process them in JS as there is no easy way to make this query across all DBs
        // Although they all support `lower()`, sqlite can't case transform unicode characters
        // This is somewhat mute, as validator.isEmail() also doesn't support unicode, but this is much easier / more
        // likely to be fixed in the near future.
        return Users.forge().fetch({require: true}).then(function (users) {
            var userWithEmail = users.find(function (user) {
                return user.get('email').toLowerCase() === email.toLowerCase();
            });
            if (userWithEmail) {
                return when.resolve(userWithEmail);
            }
        });
    }
});

Users = ghostBookshelf.Collection.extend({
    model: User
});

module.exports = {
    User: User,
    Users: Users
};