import { mat4 } from 'https://webgpufundamentals.org/3rdparty/wgpu-matrix.module.js';
import { initializeWebGPU } from './wgpu-device.js';
import { createState } from './wgpu-state.js';
import { generateGlyphTextureAtlas, createTextureFromSource } from './wgpu-utility.js';
import { createPipeline } from './wgpu-pipeline.js';
import { fetchShaderCode } from './wgpu-shader.js';
import { GenerateVertexDataAndTexture } from './wgpu-texture.js';
import { generateGlyphVerticesForText } from './wgpu-text.js';
import { config } from './wgpu-config.js';
import { CANVAS, CTX, COLORS, RENDER_PASS_DESCRIPTOR } from './wgpu-constants.js';

// Canvas element for rendering
const canvas = document.querySelector('canvas');

// State initialization
const state = createState(config);

const FIXED_DELTA_TIME = 1 / 60;  // Fixed time step of 60 FPS for physics and game logic
const MAX_FRAME_TIME = 0.25;      // Maximum time to simulate per frame to prevent spiral of death
const TARGET_FPS = 60;            // Target frames per second
const FRAME_DURATION = 1000 / TARGET_FPS; // Duration of a single frame in milliseconds

async function Main() {
    const adapter = await navigator.gpu?.requestAdapter();
    const { device, context, presentationFormat } = await initializeWebGPU(navigator, adapter, canvas);
    if (!device) return;

    state.device = device;

    // Initialize Resources
    await InitializeResources(presentationFormat);

    // Start the game loop
    GameLoop(context);
}

// Initialize shaders, pipeline, textures, and buffers
async function InitializeResources(presentationFormat) {
    // Load shader code
    const shaderCode = await fetchShaderCode('shaders.wgsl');
    const vertexSize = config.floatsPerVertex * 4;

    // Create rendering pipeline
    state.pipeline = await createPipeline(state.device, presentationFormat, vertexSize, shaderCode);

    // Generate glyph texture atlas
    const glyphCanvas = generateGlyphTextureAtlas(CANVAS, CTX, config);
    document.body.appendChild(glyphCanvas);
    glyphCanvas.style.backgroundColor = '#222';

    // Create vertex and index buffers
    CreateBuffers();

    // Generate vertex buffer data and texture
    GenerateVertexDataAndTexture(state, glyphCanvas, generateGlyphVerticesForText, COLORS, config, createTextureFromSource);
}

// Function to create vertex and index buffers
function CreateBuffers() {
    const vertexBufferSize = config.maxGlyphs * config.vertsPerGlyph * config.floatsPerVertex * 4;
    state.vertexBuffer = state.device.createBuffer({
        label: 'vertices',
        size: vertexBufferSize,
        usage: GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_DST,
    });

    state.indexBuffer = state.device.createBuffer({
        label: 'indices',
        size: config.maxGlyphs * config.vertsPerGlyph * 4,
        usage: GPUBufferUsage.INDEX | GPUBufferUsage.COPY_DST,
    });

    const indices = GenerateIndices(config.maxGlyphs);
    state.device.queue.writeBuffer(state.indexBuffer, 0, new Uint32Array(indices));
}

// Function to generate indices for glyphs
function GenerateIndices(maxGlyphs) {
    // Generate index array for glyphs
    return Array.from({ length: maxGlyphs * 6 }, (_, i) => {
        const ndx = Math.floor(i / 6) * 4;
        return (i % 6 < 3 ? [ndx, ndx + 1, ndx + 2] : [ndx + 2, ndx + 1, ndx + 3])[i % 3];
    });
}

// Game loop function
function GameLoop(context) {
    let lastTime = performance.now();
    let accumulator = 0;

    function Tick() {
        const currentTime = performance.now();
        const frameTime = (currentTime - lastTime) / 1000;
        lastTime = currentTime;

        const deltaTime = Math.min(frameTime, MAX_FRAME_TIME);
        accumulator += deltaTime;

        // Fixed time step updates for game logic
        while (accumulator >= FIXED_DELTA_TIME) {
            FixedUpdate(FIXED_DELTA_TIME);
            accumulator -= FIXED_DELTA_TIME;
        }

        // Variable time step update for rendering
        const alpha = accumulator / FIXED_DELTA_TIME;
        Render(alpha, context);

        // Schedule the next frame update
        setTimeout(Tick, FRAME_DURATION);
    }

    Tick();
}

// Fixed update function for game logic
function FixedUpdate(deltaTime) {
    state.time += deltaTime;
    // Perform game logic updates here, such as physics and AI
}

// Render function
function Render(alpha, context) {
    // Set up projection and view matrices
    const fov = 60 * Math.PI / 180;
    const aspect = canvas.clientWidth / canvas.clientHeight;
    const projectionMatrix = mat4.perspective(fov, aspect, config.render.zNear, config.render.zFar);
    const viewMatrix = mat4.lookAt([0, 0, 5], [0, 0, 0], [0, 1, 0]);
    const viewProjectionMatrix = mat4.multiply(projectionMatrix, viewMatrix);
    RENDER_PASS_DESCRIPTOR.colorAttachments[0].view = context.getCurrentTexture().createView();

    const encoder = state.device.createCommandEncoder();
    const pass = encoder.beginRenderPass(RENDER_PASS_DESCRIPTOR);
    pass.setPipeline(state.pipeline);
    mat4.rotateY(viewProjectionMatrix, state.time, state.matrix);
    mat4.translate(state.matrix, [-state.width / 2, -state.height / 2, 0], state.matrix);
    state.device.queue.writeBuffer(state.uniformBuffer, 0, state.uniformValues);
    pass.setBindGroup(0, state.bindGroup);
    pass.setVertexBuffer(0, state.vertexBuffer);
    pass.setIndexBuffer(state.indexBuffer, 'uint32');
    pass.drawIndexed(state.numGlyphs * 6);
    pass.end();
    state.device.queue.submit([encoder.finish()]);
}

// Initialize application
Main();