var mysql = require('mysql');

// Webtask compiler entry point. options.script contains parameterized T-SQL script.
module.exports = function (options, cb) {

    // Return a JavaScript function in one of the three basic signatures supported by Webtasks
    return cb(null, function (ctx, cb) {

        // Create MySQL connection on first invocation
        if (!global.connection) {

            // Validate that required MySQL connection parameters were specified at webtask creation
            var secrets = ['HOST','DB','USER','PASSWORD'];
            for (var i = 0; i < secrets.length; i++) 
                if (!ctx.secrets[secrets[i]]) 
                    return cb(new Error('You must specify the ' + secrets[i] + ' secret when creating the webtask.'));

            // Create MySQL connection and cache it in-memory for use by later webtask requests
            global.connection = mysql.createConnection({
                host     : ctx.secrets.HOST,
                user     : ctx.secrets.DB,
                password : ctx.secrets.PASSWORD,
                database : ctx.secrets.USER
            });
            global.connection.connect();
        }

        // Execute parameterized MySQL query setting parameter value(s) based on 
        // the value of the URL query parameter(s) `q`. Webtask will return MySQL error or
        // a JSON array of matching rows.
        return global.connection.query(options.script, ctx.query.q, cb);
    });
};