var Stream = require('stream');

var Response = module.exports = function (res) {
    this.offset = 0;
    this.readable = true;
};

Response.prototype = new Stream;

var capable = {
    streaming : true,
    status2 : true
};

function parseHeaders (res) {
    var lines = res.getAllResponseHeaders().split(/\r?\n/);
    var headers = {};
    for (var i = 0; i < lines.length; i++) {
        var line = lines[i];
        if (line === '') continue;
        
        var m = line.match(/^([^:]+):\s*(.*)/);
        if (m) {
            var key = m[1].toLowerCase(), value = m[2];
            
            if (headers[key] !== undefined) {
            
                if (isArray(headers[key])) {
                    headers[key].push(value);
                }
                else {
                    headers[key] = [ headers[key], value ];
                }
            }
            else {
                headers[key] = value;
            }
        }
        else {
            headers[line] = true;
        }
    }
    return headers;
}

Response.prototype.getResponse = function (xhr) {
    var respType = String(xhr.responseType).toLowerCase();
    if (respType === 'blob') return xhr.responseBlob || xhr.response;
    if (respType === 'arraybuffer') return xhr.response;
    return xhr.responseText;
}

Response.prototype.getHeader = function (key) {
    return this.headers[key.toLowerCase()];
};

Response.prototype.handle = function (res) {
    if (res.readyState === 2 && capable.status2) {
        try {
            this.statusCode = res.status;
            this.headers = parseHeaders(res);
        }
        catch (err) {
            capable.status2 = false;
        }
        
        if (capable.status2) {
            this.emit('ready');
        }
    }
    else if (capable.streaming && res.readyState === 3) {
        try {
            if (!this.statusCode) {
                this.statusCode = res.status;
                this.headers = parseHeaders(res);
                this.emit('ready');
            }
        }
        catch (err) {}
        
        try {
            this._emitData(res);
        }
        catch (err) {
            capable.streaming = false;
        }
    }
    else if (res.readyState === 4) {
        if (!this.statusCode) {
            this.statusCode = res.status;
            this.emit('ready');
        }
        this._emitData(res);
        
        if (res.error) {
            this.emit('error', this.getResponse(res));
        }
        else this.emit('end');
        
        this.emit('close');
    }
};

Response.prototype._emitData = function (res) {
    var respBody = this.getResponse(res);
    if (respBody.toString().match(/ArrayBuffer/)) {
        this.emit('data', new Uint8Array(respBody, this.offset));
        this.offset = respBody.byteLength;
        return;
    }
    if (respBody.length > this.offset) {
        this.emit('data', respBody.slice(this.offset));
        this.offset = respBody.length;
    }
};

var isArray = Array.isArray || function (xs) {
    return Object.prototype.toString.call(xs) === '[object Array]';
};