const Lang = imports.lang;
const St = imports.gi.St;
const Clutter = imports.gi.Clutter;
const Gio = imports.gi.Gio;
const GLib = imports.gi.GLib;
const GObject = imports.gi.GObject;
const Cogl = imports.gi.Cogl;
const Shell = imports.gi.Shell;
const Meta = imports.gi.Meta;

const ExtensionUtils = imports.misc.extensionUtils;
const Me = ExtensionUtils.getCurrentExtension();
const Main = imports.ui.main;
const PanelMenu = imports.ui.panelMenu;

const UINT8_SIZE = 1;
const BOOL_SIZE = UINT8_SIZE;
const UINT_SIZE = 4;
const FLOAT_SIZE = 4;

// end offset, exclusive
const DATA_VIEW_INFO_OFFSET_INDEX = 0;
const DATA_VIEW_INFO_SIZE_INDEX = 1;
const DATA_VIEW_INFO_COUNT_INDEX = 1;
function dataViewEnd(dataViewInfo) {
    return dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX] + dataViewInfo[DATA_VIEW_INFO_SIZE_INDEX] * dataViewInfo[DATA_VIEW_INFO_COUNT_INDEX];
}

// the driver should be using the same data layout version
const DATA_LAYOUT_VERSION = 1;

// DataView info: [offset, size, count]
const VERSION = [0, UINT8_SIZE, 1];
const ENABLED = [dataViewEnd(VERSION), BOOL_SIZE, 1];
const EPOCH_SEC_OFFSET = [dataViewEnd(VERSION), UINT_SIZE, 1];
const LOOK_AHEAD_CFG = [dataViewEnd(EPOCH_SEC_OFFSET), FLOAT_SIZE, 4];
const DISPLAY_RES = [dataViewEnd(LOOK_AHEAD_CFG), UINT_SIZE, 2];
const DISPLAY_FOV = [dataViewEnd(DISPLAY_RES), FLOAT_SIZE, 1];
const DISPLAY_ZOOM = [dataViewEnd(DISPLAY_FOV), FLOAT_SIZE, 1];
const DISPLAY_NORTH_OFFSET = [dataViewEnd(DISPLAY_ZOOM), FLOAT_SIZE, 1];
const LENS_DISTANCE_RATIO = [dataViewEnd(DISPLAY_NORTH_OFFSET), FLOAT_SIZE, 1];
const SBS_ENABLED = [dataViewEnd(LENS_DISTANCE_RATIO), BOOL_SIZE, 1];
const SBS_CONTENT = [dataViewEnd(SBS_ENABLED), BOOL_SIZE, 1];
const SBS_MODE_STRETCHED = [dataViewEnd(SBS_CONTENT), BOOL_SIZE, 1];
const CUSTOM_BANNER_ENABLED = [dataViewEnd(SBS_MODE_STRETCHED), BOOL_SIZE, 1];
const IMU_QUAT_DATA = [dataViewEnd(CUSTOM_BANNER_ENABLED), FLOAT_SIZE, 16];

// cached after first retrieval
const shaderUniformLocations = {
    'enabled': null,
    'imu_quat_data': null,
    'look_ahead_cfg': null,
    'stage_aspect_ratio': null,
    'display_aspect_ratio': null,
    'display_zoom': null,
    'display_north_offset': null,
    'lens_distance_ratio': null,
    'sbs_enabled': null,
    'sbs_content': null,
    'sbs_mode_stretched': null,
    'custom_banner_enabled': null,
    'half_fov_z_rads': null,
    'half_fov_y_rads': null,
    'screen_distance': null
};

function dataViewUint8(dataView, dataViewInfo) {
    return dataView.getUint8(dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX]);
}

function dataViewUint(dataView, dataViewInfo) {
    return dataView.getUint32(dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX], true);
}

function dataViewUintArray(dataView, dataViewInfo) {
    const uintArray = []
    const offset = dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX];
    for (let i = 0; i < dataViewInfo[DATA_VIEW_INFO_COUNT_INDEX]; i++) {
        uintArray.push(dataView.getUint32(offset, true));
        offset += UINT_SIZE;
    }
    return uintArray;
}

function dataViewFloat(dataView, dataViewInfo) {
    return dataView.getFloat32(dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX], true);
}

function dataViewFloatArray(dataView, dataViewInfo) {
    const floatArray = []
    const offset = dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX];
    for (let i = 0; i < dataViewInfo[DATA_VIEW_INFO_COUNT_INDEX]; i++) {
        floatArray.push(dataView.getFloat32(offset, true));
        offset += FLOAT_SIZE;
    }
    return floatArray;
}


function getShaderSource(path) {
    const file = Gio.file_new_for_path(path);
    const data = file.load_contents(null);

    // version string helps with linting, but GNOME extension doesn't like it, so remove it if it's there
    return data[1].toString().replace(/^#version .*$/gm, '') + '\n';
}

function transferUniformBoolean(effect, locationName, dataView, dataViewInfo) {
    // GLSL bool is a float under the hood, evaluates false if 0 or 0.0, true otherwise
    effect.set_uniform_float(locationName, 1, [dataViewUint8(dataView, dataViewInfo)]);
}

function setUniformFloat(effect, locationName, dataViewInfo, value) {
    effect.set_uniform_float(shaderUniformLocations[locationName], dataViewInfo[DATA_VIEW_INFO_COUNT_INDEX], value);
}

function transferUniformFloat(effect, locationName, dataView, dataViewInfo) {
    setUniformFloat(effect, locationName, dataViewInfo, dataViewFloatArray(dataView, dataViewInfo));

function setUniformMatrix(effect, locationName, components, dataView, dataViewInfo) {
    const numValues = dataViewInfo[DATA_VIEW_INFO_COUNT_INDEX];
    if (numValues / componenents !== components) {
        throw new Error('Invalid matrix size');
    }

    const floatArray = [].fill(0, 0, numValues);
    const offset = dataViewInfo[DATA_VIEW_INFO_OFFSET_INDEX];
    for (let i = 0; i < numValues; i++) {
        // GLSL uses column-major order, so we need to transpose the matrix
        const row = i % components;
        const column = Math.floor(i / components);

        floatArray[row * components + column] = dataView.getFloat32(offset, true);
        offset += FLOAT_SIZE;
    }
    effect.set_uniform_matrix(shaderUniformLocations[locationName], true, components, floatArray);
}

function getEpochSec() {
    return Math.floor(Date.now() / 1000);
}

function degreeToRadian(degree) {
    return degree * Math.PI / 180;
}

// config doesn't change frequently, so we'll set these all at once, periodically
function setConfigUniformVarables(effect, dataView) {
    const version = dataViewUint8(dataView, VERSION);
    const date = dataViewUint(dataView, EPOCH_SEC_OFFSET);
    const validKeepalive = Math.abs(getEpochSec() - date) < 5;
    const imuData = dataViewFloatArray(dataView, IMU_QUAT_DATA);
    const imuResetState = imuData[0] === 0.0 && imuData[1] === 0.0 && imuData[2] === 0.0 && imuData[3] === 1.0;
    const enabled = dataViewUint8(dataView, ENABLED) !== 0 && version === DATA_LAYOUT_VERSION && validKeepalive && !imuResetState;
    if (enabled) {
        const displayRes = dataViewUintArray(dataView, DISPLAY_RES);
        const displayFov = dataViewFloat(dataView, DISPLAY_FOV);
        const lensDistanceRatio = dataViewFloat(dataView, LENS_DISTANCE_RATIO);

        // compute these values once, they only change when the XR device changes
        const displayAspectRatio = displayRes[0] / displayRes[1];
        const stageAspectRatio = global.stage.get_width() / global.stage.get_height();
        const diagToVertRatio = Math.sqrt(Math.pow(stageAspectRatio, 2) + 1);
        const halfFovZRads = degreeToRadian(displayFov / diagToVertRatio) / 2;
        const halfFovYRads = halfFovZRads * stageAspectRatio;
        const screenDistance = 1.0 - lensDistanceRatio;
        
        // all these values are passed directly to the shader, unmodified
        transferUniformFloat(effect, 'imu_quat_data', dataView, IMU_QUAT_DATA);
        transferUniformFloat(effect, 'look_ahead_cfg', dataView, LOOK_AHEAD_CFG);
        transferUniformFloat(effect, 'display_zoom', dataView, DISPLAY_ZOOM);
        transferUniformFloat(effect, 'display_north_offset', dataView, DISPLAY_NORTH_OFFSET);
        transferUniformFloat(effect, 'lens_distance_ratio', dataView, LENS_DISTANCE_RATIO);
        transferUniformBoolean(effect, 'sbs_enabled', dataView, SBS_ENABLED);
        transferUniformBoolean(effect, 'sbs_content', dataView, SBS_CONTENT);
        transferUniformBoolean(effect, 'sbs_mode_stretched', dataView, SBS_MODE_STRETCHED);
        transferUniformBoolean(effect, 'custom_banner_enabled', dataView, CUSTOM_BANNER_ENABLED);

        // no dataViewInfo, so we set these manually
        effect.set_uniform_float(shaderUniformLocations['stage_aspect_ratio'], 1, [stageAspectRatio]);
        effect.set_uniform_float(shaderUniformLocations['display_aspect_ratio'], 1, [displayAspectRatio]);
        effect.set_uniform_float(shaderUniformLocations['half_fov_z_rads'], 1, [halfFovZRads]);
        effect.set_uniform_float(shaderUniformLocations['half_fov_y_rads'], 1, [halfFovYRads]);
        effect.set_uniform_float(shaderUniformLocations['screen_distance'], 1, [screenDistance]);
    }
    setUniformBoolean(effect, shaderUniformLocations['enabled'], ENABLED, enabled);
}

class Extension {
    enable() {
        var XREffect = GObject.registerClass({}, class XREffect extends Shell.GLSLEffect {
            vfunc_build_pipeline() {
                // Shell.GLSLEffect requires the declarations and the main source code as separate
                // strings. As it's more convenient to store the in one GLSL file, we use a regex
                // here to split the source code in two parts.
                const code = getShaderSource('/home/wayne/IdeaProjects/nreal/breezy-desktop/gnome/breezydesktop@org.xronlinux/IMUAdjust.frag');

                const main = 'PS_IMU_Transform(vec4(0, 0, 0, 0), cogl_tex_coord_in[0].xy, cogl_color_out);';
                this.add_glsl_snippet(Shell.SnippetHook.FRAGMENT, code, main, false);
            }

            // TODO - read IMU data and update uniform variables
            vfunc_paint_target(node, paintContext) {

              const data = this._shared_mem_file.load_contents(null);
              if (data[0]) {
                const buffer = new Uint8Array(data[1]).buffer;
                var dataView = new DataView(buffer);
                var repaintNeeded = false;
                if (!this._initialized) { 
                    this.set_uniform_float(this.get_uniform_location('uDesktopTexture'), 1, [0]);
                    this._shared_mem_file = Gio.file_new_for_path("/dev/shm/imu_data");

                    // iterate over shaderUniformLocations keys and set the uniform locations
                    for (let key in shaderUniformLocations) {
                        shaderUniformLocations[key] = this.get_uniform_location(key);
                    }

                    setConfigUniformVarables(this, dataView);

                    GLib.timeout_add(GLib.PRIORITY_DEFAULT, 1000/50, () => {
                        repaintNeeded = true;
                        this.queue_repaint();
                        return GLib.SOURCE_CONTINUE;
                    });

                    GLib.timeout_add(GLib.PRIORITY_DEFAULT, 250, () => {
                        setConfigUniformVarables(this, dataView);
                        return GLib.SOURCE_CONTINUE;
                    });
                    Meta.CursorTracker.get_for_display(global.display).set_pointer_visible(true);
                    console.log(`is_rendering_hardware_accelerated: ${Meta.CursorTracker.get_for_display(global.display).backend.is_rendering_hardware_accelerated()}`);

                    this._initialized = true;
                }

                transferUniformFloat(this, 'imu_quat_data', dataView, IMU_QUAT_DATA);
                
                // if (repaintNeeded) {
                  super.vfunc_paint_target(node, paintContext);
                // }
              }
            }
        });

        global.stage.add_effect(new XREffect());
    }

    disable() {
    }
}

function init() {
    return new Extension();
}