"use strict";
const q = require("q");
import expect from 'expect';

/**
 * Construct a mock HTTP backend, heavily inspired by Angular.js.
 * @constructor
 */
function HttpBackend() {
    this.requests = [];
    this.expectedRequests = [];
    const self = this;
    // the request function dependency that the SDK needs.
    this.requestFn = function(opts, callback) {
        const req = new Request(opts, callback);
        console.log(`${Date.now()} HTTP backend received request: ${req}`);
        self.requests.push(req);

        const abort = function() {
            const idx = self.requests.indexOf(req);
            if (idx >= 0) {
                console.log("Aborting HTTP request: %s %s", opts.method,
                            opts.uri);
                self.requests.splice(idx, 1);
                req.callback("aborted");
            }
        };

        return {
            abort: abort,
        };
    };
}
HttpBackend.prototype = {
    /**
     * Respond to all of the requests (flush the queue).
     * @param {string} path The path to flush (optional) default: all.
     * @param {integer} numToFlush The number of things to flush (optional), default: all.
     * @param {integer=} waitTime  The time (in ms) to wait for a request to happen.
     *    default: 5
     *
     * @return {Promise} resolves when there is nothing left to flush, with the
     *    number of requests flushed
     */
    flush: function(path, numToFlush, waitTime) {
        const defer = q.defer();
        const self = this;
        let flushed = 0;
        let triedWaiting = false;
        if (waitTime === undefined) {
            waitTime = 5;
        }

        function log(msg) {
            console.log(`${Date.now()} flush[${path || ''}]: ${msg}`);
        }

        log("HTTP backend flushing... (path=" + path
            + " numToFlush=" + numToFlush
            + " waitTime=" + waitTime
            + ")",
        );
        const tryFlush = function() {
            // if there's more real requests and more expected requests, flush 'em.
            log(`  trying to flush => reqs=[${self.requests}] ` +
                `expected=[${self.expectedRequests}]`,
            );
            if (self._takeFromQueue(path)) {
                // try again on the next tick.
                flushed += 1;
                if (numToFlush && flushed === numToFlush) {
                    log(`Flushed assigned amount: ${numToFlush}`);
                    defer.resolve(flushed);
                } else {
                    log(`  flushed. Trying for more.`);
                    setTimeout(tryFlush, 0);
                }
            } else if (flushed === 0 && !triedWaiting) {
                // we may not have made the request yet, wait a generous amount of
                // time before giving up.
                log(`  nothing to flush yet; waiting for requests.`);
                setTimeout(tryFlush, waitTime);
                triedWaiting = true;
            } else {
                if (flushed === 0) {
                    log("nothing to flush; giving up");
                } else {
                    log(`no more flushes after flushing ${flushed} requests`);
                }
                defer.resolve(flushed);
            }
        };

        setTimeout(tryFlush, 0);

        return defer.promise;
    },

    /**
     * Attempts to resolve requests/expected requests.
     * @param {string} path The path to flush (optional) default: all.
     * @return {boolean} true if something was resolved.
     */
    _takeFromQueue: function(path) {
        let req = null;
        let i;
        let j;
        let matchingReq = null;
        let expectedReq = null;
        let testResponse = null;
        for (i = 0; i < this.requests.length; i++) {
            req = this.requests[i];
            for (j = 0; j < this.expectedRequests.length; j++) {
                expectedReq = this.expectedRequests[j];
                if (path && path !== expectedReq.path) {
                    continue;
                }
                if (expectedReq.method === req.method &&
                        req.path.indexOf(expectedReq.path) !== -1) {
                    if (!expectedReq.data || (JSON.stringify(expectedReq.data) ===
                            JSON.stringify(req.data))) {
                        matchingReq = expectedReq;
                        this.expectedRequests.splice(j, 1);
                        break;
                    }
                }
            }

            if (matchingReq) {
                // remove from request queue
                this.requests.splice(i, 1);
                i--;

                for (j = 0; j < matchingReq.checks.length; j++) {
                    matchingReq.checks[j](req);
                }
                testResponse = matchingReq.response;
                console.log(`${Date.now()}    responding to ${matchingReq.path}`);
                let body = testResponse.body;
                if (Object.prototype.toString.call(body) == "[object Function]") {
                    body = body(req.path, req.data);
                }
                req.callback(
                    testResponse.err, testResponse.response, body,
                );
                matchingReq = null;
            }
        }
        if (testResponse) {  // flushed something
            return true;
        }
        return false;
    },

    /**
     * Makes sure that the SDK hasn't sent any more requests to the backend.
     */
    verifyNoOutstandingRequests: function() {
        const firstOutstandingReq = this.requests[0] || {};
        expect(this.requests.length).toEqual(0,
            "Expected no more HTTP requests but received request to " +
            firstOutstandingReq.path,
        );
    },

    /**
     * Makes sure that the test doesn't have any unresolved requests.
     */
    verifyNoOutstandingExpectation: function() {
        const firstOutstandingExpectation = this.expectedRequests[0] || {};
        expect(this.expectedRequests.length).toEqual(0,
            "Expected to see HTTP request for " + firstOutstandingExpectation.path,
        );
    },

    /**
     * Create an expected request.
     * @param {string} method The HTTP method
     * @param {string} path The path (which can be partial)
     * @param {Object} data The expected data.
     * @return {Request} An expected request.
     */
    when: function(method, path, data) {
        const pendingReq = new ExpectedRequest(method, path, data);
        this.expectedRequests.push(pendingReq);
        return pendingReq;
    },
};

/**
 * Represents the expectation of a request.
 *
 * <p>Includes the conditions to be matched against, the checks to be made,
 * and the response to be returned.
 *
 * @constructor
 * @param {string} method
 * @param {string} path
 * @param {object?} data
 */
function ExpectedRequest(method, path, data) {
    this.method = method;
    this.path = path;
    this.data = data;
    this.response = null;
    this.checks = [];
}

ExpectedRequest.prototype = {
    toString: function() {
        return this.method + " " + this.path
    },

    /**
     * Execute a check when this request has been satisfied.
     * @param {Function} fn The function to execute.
     * @return {Request} for chaining calls.
     */
    check: function(fn) {
        this.checks.push(fn);
        return this;
    },

    /**
     * Respond with the given data when this request is satisfied.
     * @param {Number} code The HTTP status code.
     * @param {Object|Function} data The HTTP JSON body. If this is a function,
     * it will be invoked when the JSON body is required (which should be returned).
     */
    respond: function(code, data) {
        this.response = {
            response: {
                statusCode: code,
                headers: {},
            },
            body: data,
            err: null,
        };
    },

    /**
     * Fail with an Error when this request is satisfied.
     * @param {Number} code The HTTP status code.
     * @param {Error} err The error to throw (e.g. Network Error)
     */
    fail: function(code, err) {
        this.response = {
            response: {
                statusCode: code,
                headers: {},
            },
            body: null,
            err: err,
        };
    },
};

/**
 * Represents a request made by the app.
 *
 * @constructor
 * @param {object} opts opts passed to request()
 * @param {function} callback
 */
function Request(opts, callback) {
    this.opts = opts;
    this.callback = callback;

    Object.defineProperty(this, 'method', {
        get: function() {
            return opts.method;
        },
    });

    Object.defineProperty(this, 'path', {
        get: function() {
            return opts.uri;
        },
    });

    Object.defineProperty(this, 'data', {
        get: function() {
            return opts.body;
        },
    });

    Object.defineProperty(this, 'queryParams', {
        get: function() {
            return opts.qs;
        },
    });

    Object.defineProperty(this, 'headers', {
        get: function() {
            return opts.headers || {};
        },
    });
}

Request.prototype = {
    toString: function() {
        return this.method + " " + this.path;
    },
};

/**
 * The HttpBackend class.
 */
module.exports = HttpBackend;