Create Comments class to handle comments queries.

module.exports = (function(){

    /**

     * Represents a Comments table.

     *

     * @constructor

     * Initializes Comments with a database connection and a target domain.

     *

     * @param {mysql.Connection} db MySQL connection object.

     *

     * @param {String} domain The comments domain within which to work.

     * For example by passing "touch-2" the #find method will only find

     * comments within touch-2 domain.

     */

    function Comments(db, domain) {

        this.db = db;

        this.domain = domain;

    }

    Comments.prototype = {

        /**

         * Finds list of all comments for a particular target.

         * Excludes deleted comments.

         *

         * @param {Object} target The target:

         * @param {String} target.type One of: class, guide, video.

         * @param {String} target.cls The name of the class, guide or video.

         * @param {String} target.member The name of class member or empty string.

         *

         * @param {Function} callback Called with the result.

         * @param {Object[]} callback.comments An array of comment rows.

         */

        find: function(target, callback) {

            var sql = [

                'SELECT *',

                'FROM full_visible_comments',

                'WHERE domain = ? AND type = ? AND cls = ? AND member = ?',

                'ORDER BY created_at'

            ];

            this.query(sql, [this.domain, target.type, target.cls, target.member], callback);

        },

        /**

         * Returns all comments sorted in reverse chronological order.

         * Excludes deleted comments.

         *

         * @param {Object} opts Options for the query:

         * @param {Number} opts.limit Number of rows to return.

         * @param {Number} opts.offset The starting index.

         *

         * @param {Function} callback Called with the result.

         * @param {Object[]} callback.comments An array of comment rows.

         */

        findRecent: function(opts, callback) {

            var sql = [

                'SELECT *',

                'FROM full_visible_comments',

                'WHERE domain = ?',

                'ORDER BY created_at DESC',

                'LIMIT ? OFFSET ?'

            ];

            this.query(sql, [this.domain, opts.limit, opts.offset], callback);

        },

        /**

         * Counts number of comments in the current domain.

         * Excludes deleted comments.

         *

         * @param {Object} opts Reserved for future.

         *

         * @param {Function} callback Called with the result.

         * @param {Number} callback.count The number of comments found.

         */

        count: function(opts, callback) {

            var sql = [

                'SELECT COUNT(*) as count',

                'FROM full_visible_comments',

                'WHERE domain = ?'

            ];

            this.query(sql, [this.domain], function(rows) {

                callback(rows[0].count);

            });

        },

        query: function(sqlLines, params, callback) {

            this.db.query(sqlLines.join("\n"), params, function(err, rows) {

                if (err) throw err;

                callback(rows);

            });

        }

    };

    return Comments;

})();

var Comments = require("./comments");

var mysql = require('mysql');

var connection = mysql.createConnection({

    host: 'localhost',

    user: '',

    password: '',

    database: 'comments'

});

var comments = new Comments(connection, "touch-2");

comments.count({}, function(cnt) {

    console.log(cnt + " comments");

    process.exit();

});

FROM visible_comments c LEFT JOIN votes v ON c.id = v.comment_id

GROUP BY c.id;

-- comments table joined with users and targets for easier quering

CREATE VIEW full_visible_comments AS SELECT

    c.id,

    c.content,

    c.content_html,

    c.created_at,

    users.username,

    users.external_id,

    users.email,

    users.moderator,

    targets.domain,

    targets.type,

    targets.cls,

    targets.member

FROM visible_comments AS c

    LEFT JOIN users ON c.user_id = users.id

    LEFT JOIN targets ON c.target_id = targets.id;