var assert = require('assert');
var _ = require('underscore');
var step = require('step');

var LZMA = require('lzma').LZMA;
var lzmaWorker = new LZMA();


// Whitelist query parameters and attach format
var REQUEST_QUERY_PARAMS_WHITELIST = [
    'config',
    'map_key',
    'api_key',
    'auth_token',
    'callback',
    'zoom',
    'lon',
    'lat',
    // analysis
    'filters' // json
];

// jshint maxcomplexity:10
/**
 * Whitelist input and get database name & default geometry type from
 * subdomain/user metadata held in CartoDB Redis
 * @param req - standard express request obj. Should have host & table
 * @param callback
 */
module.exports = function req2paramsMiddleware (authApi, pgConnection) {
    return function req2params (req, res, next) {
        if ( req.query.lzma ) {

            // Decode (from base64)
            var lzma = new Buffer(req.query.lzma, 'base64')
                .toString('binary')
                .split('')
                .map(function(c) {
                    return c.charCodeAt(0) - 128;
                });


            // Decompress
            lzmaWorker.decompress(
                lzma,
                function(result) {
                    req.profiler.done('lzma');
                    try {
                        delete req.query.lzma;
                        _.extend(req.query, JSON.parse(result));
                        req2params(req, res, next);
                    } catch (err) {
                        req.profiler.done('req2params');
                        next(new Error('Error parsing lzma as JSON: ' + err));
                    }
                }
            );
            return;
        }

        var allowedQueryParams = REQUEST_QUERY_PARAMS_WHITELIST;
        if (Array.isArray(req.context.allowedQueryParams)) {
            allowedQueryParams = allowedQueryParams.concat(req.context.allowedQueryParams);
        }
        req.query = _.pick(req.query, allowedQueryParams);
        req.params = _.extend({}, req.params); // shuffle things as request is a strange array/object

        var user = req.context.user;

        if ( req.params.token ) {
            // Token might match the following patterns:
            // - {user}@{tpl_id}@{token}:{cache_buster}
            var tksplit = req.params.token.split(':');
            req.params.token = tksplit[0];
            if ( tksplit.length > 1 ) {
                req.params.cache_buster= tksplit[1];
            }
            tksplit = req.params.token.split('@');
            if ( tksplit.length > 1 ) {
                req.params.signer = tksplit.shift();
                if ( ! req.params.signer ) {
                    req.params.signer = user;
                }
                else if ( req.params.signer !== user ) {
                    var err = new Error(
                            'Cannot use map signature of user "' + req.params.signer + '" on db of user "' + user + '"'
                    );
                    err.http_status = 403;
                    req.profiler.done('req2params');
                    next(err);
                    return;
                }
                if ( tksplit.length > 1 ) {
                    /*var template_hash = */tksplit.shift(); // unused
                }
                req.params.token = tksplit.shift();
            }
        }

        // bring all query values onto req.params object
        _.extend(req.params, req.query);

        // FIXME: Temporary hack to share data between middlewares. Express overrides req.params to
        // parse url params to an object and it's performed after matching path and controller.
        req.locals = {};
        _.extend(req.locals, req.params);

        req.profiler.done('req2params.setup');

        step(
            function getPrivacy(){
                authApi.authorize(req, this);
            },
            function validateAuthorization(err, authorized) {
                req.profiler.done('authorize');
                assert.ifError(err);
                if(!authorized) {
                    err = new Error("Sorry, you are unauthorized (permission denied)");
                    err.http_status = 403;
                    throw err;
                }
                return null;
            },
            function getDatabase(err){
                assert.ifError(err);
                pgConnection.setDBConn(user, req.params, this);
            },
            function finishSetup(err) {
                if ( err ) {
                    req.profiler.done('req2params');
                    return next(err, req);
                }

                // Add default database connection parameters
                // if none given
                _.defaults(req.params, {
                    dbuser: global.environment.postgres.user,
                    dbpassword: global.environment.postgres.password,
                    dbhost: global.environment.postgres.host,
                    dbport: global.environment.postgres.port
                });

                // FIXME: Temporary hack to share data between middlewares. Express overrides req.params to
                // parse url params to an object and it's performed after matching path and controller.
                _.defaults(req.locals, req.params);

                req.profiler.done('req2params');
                next(null, req);
            }
        );
    };
};