ampersand-sync.js

var _ = require('underscore');
var xhr = require('xhr');
var qs = require('qs');


// Throw an error when a URL is needed, and none is supplied.
var urlError = function () {
    throw new Error('A "url" property or function must be specified');
};


module.exports = function (method, model, options) {
    var type = methodMap[method];
    var headers = {};

    // Default options, unless specified.
    _.defaults(options || (options = {}), {
        emulateHTTP: false,
        emulateJSON: false
    });

    // Default request options.
    var params = {type: type, responseType: 'json'};

    // Ensure that we have a URL.
    if (!options.url) {
        params.url = _.result(model, 'url') || urlError();
    }

    // Ensure that we have the appropriate request data.
    if (options.data == null && model && (method === 'create' || method === 'update' || method === 'patch')) {
        params.json = options.attrs || model.toJSON(options);
    }

    // For older servers, emulate JSON by encoding the request into an HTML-form.
    if (options.emulateJSON) {
        headers['Content-Type'] = 'application/x-www-form-urlencoded';
        params.body = params.json ? {model: params.json} : {};
        if (params.json) delete params.json;
    }

    // For older servers, emulate HTTP by mimicking the HTTP method with `_method`
    // And an `X-HTTP-Method-Override` header.
    if (options.emulateHTTP && (type === 'PUT' || type === 'DELETE' || type === 'PATCH')) {
        params.type = 'POST';
        if (options.emulateJSON) params.body._method = type;
        headers['X-HTTP-Method-Override'] = type;
    }

    // When emulating JSON, we turn the body into a querystring.
    // We do this later to let the emulateHTTP run its course.
    if (options.emulateJSON) {
        params.body = qs.stringify(params.body);
    }

    // Combine generated headers with user's headers.
    if (options.headers) _.extend(headers, options.headers);

    // Turn a jQuery.ajax formatted request into xhr compatible
    params.method = params.type;

    var ajaxSettings = _.extend(params, options);

    // Make the request. The callback executes functions that are compatible
    // With jQuery.ajax's syntax.
    var _xhr = options.xhr = xhr(ajaxSettings, function (err, resp, body) {
        if (err && options.error) return options.error(resp, 'error', err.message);
        if (body && options.success) return options.success(body, 'success', resp);
    });
    model.trigger('request', model, _xhr, options, ajaxSettings);
    return _xhr;
};

// Map from CRUD to HTTP for our default `Backbone.sync` implementation.
var methodMap = {
    'create': 'POST',
    'update': 'PUT',
    'patch':  'PATCH',
    'delete': 'DELETE',
    'read':   'GET'
};