//============================================================================
// Kernel
//============================================================================

var IPython = (function (IPython) {

    var utils = IPython.utils;

    var Kernel = function () {
        this.kernel_id = null;
        this.base_url = "/kernels";
        this.kernel_url = null;
        this.shell_channel = null;
        this.iopub_channel = null;
        this.running = false;
    };


    Kernel.prototype.get_msg = function (msg_type, content) {
        var msg = {
            header : {
                msg_id : utils.uuid(),
                username : "username",
                session: this.session_id,
                msg_type : msg_type
            },
            content : content,
            parent_header : {}
        };
        return msg;
    }

    Kernel.prototype.start = function (notebook_id, callback) {
        var that = this;
        if (!this.running) {
            var qs = $.param({notebook:notebook_id});
            $.post(this.base_url + '?' + qs,
                function (kernel_id) {
                    that._handle_start_kernel(kernel_id, callback);
                }, 
                'json'
            );
        };
    };


    Kernel.prototype.restart = function (callback) {
        IPython.kernel_status_widget.status_restarting();
        var url = this.kernel_url + "/restart";
        var that = this;
        if (this.running) {
            this.stop_channels();
            $.post(url,
                function (kernel_id) {
                    that._handle_start_kernel(kernel_id, callback);
                },
                'json'
            );
        };
    };


    Kernel.prototype._handle_start_kernel = function (kernel_id, callback) {
        this.running = true;
        this.kernel_id = kernel_id;
        this.kernel_url = this.base_url + "/" + this.kernel_id;
        this.start_channels();
        callback();
        IPython.kernel_status_widget.status_idle();
    };


    Kernel.prototype.start_channels = function () {
        this.stop_channels();
        var ws_url = "ws://127.0.0.1:8888" + this.kernel_url;
        this.shell_channel = new WebSocket(ws_url + "/shell");
        this.iopub_channel = new WebSocket(ws_url + "/iopub");
    };


    Kernel.prototype.stop_channels = function () {
        if (this.shell_channel !== null) {
            this.shell_channel.close();
            this.shell_channel = null;
        };
        if (this.iopub_channel !== null) {
            this.iopub_channel.close();
            this.iopub_channel = null;
        };
    };

    Kernel.prototype.execute = function (code) {
        var content = {
            code : code,
            silent : false,
            user_variables : [],
            user_expressions : {}
        };
        var msg = this.get_msg("execute_request", content);
        this.shell_channel.send(JSON.stringify(msg));
        return msg.header.msg_id;
    }


    Kernel.prototype.complete = function (line, cursor_pos) {
        var content = {
            text : '',
            line : line,
            cursor_pos : cursor_pos
        };
        var msg = this.get_msg("complete_request", content);
        this.shell_channel.send(JSON.stringify(msg));
        return msg.header.msg_id;
    }


    Kernel.prototype.interrupt = function () {
        if (this.running) {
            $.post(this.kernel_url + "/interrupt");
        };
    };


    Kernel.prototype.kill = function () {
        if (this.running) {
            this.running = false;
            var settings = {
                cache : false,
                type : "DELETE",
            };
            $.ajax(this.kernel_url, settings);
        };
    };

    IPython.Kernel = Kernel;

    return IPython;

}(IPython));