const FLASH_SIZE = 16 * 1024 * 1024;
const BOOTLOADER_OFFSET = 0x0;
const PARTITIONS_OFFSET = 0x8000;
const APP_OFFSET = 0x10000;
const ESP_IMAGE_MAGIC = 0xe9;
const RELEASED_ADC = 4095;

export const BUTTONS = {
  back: { type: 'adc', channel: 1, value: 3512 },
  confirm: { type: 'adc', channel: 1, value: 2694 },
  left: { type: 'adc', channel: 1, value: 1493 },
  right: { type: 'adc', channel: 1, value: 5 },
  up: { type: 'adc', channel: 2, value: 2242 },
  down: { type: 'adc', channel: 2, value: 5 },
  power: { type: 'gpio', pin: 3 },
};

// Assemble Flash Image - m25p80 requires a backing file exactly the chip size (16 MB), so a bare app image is placed into a 0xFF-erased 16 MB flash alongside the bootloader and partition table.
export function mergeFirmware(app, bootloader, partitions) {
  if (app[0] !== ESP_IMAGE_MAGIC) {
    throw new Error('Not an ESP32 app image (missing 0xE9 magic byte).');
  }
  if (APP_OFFSET + app.length > FLASH_SIZE) {
    throw new Error(`App image is too large for the ${FLASH_SIZE / 1024 / 1024} MB flash.`);
  }
  const flash = new Uint8Array(FLASH_SIZE).fill(0xff);
  flash.set(bootloader, BOOTLOADER_OFFSET);
  flash.set(partitions, PARTITIONS_OFFSET);
  flash.set(app, APP_OFFSET);
  return flash;
}

async function fetchBin(url) {
  const response = await fetch(url);
  if (!response.ok) {
    throw new Error(`Could not load ${url.pathname} (${response.status}).`);
  }
  return new Uint8Array(await response.arrayBuffer());
}

// A full 16 MB image is used as-is; anything else is treated as a CrossPoint app image and merged with the bundled bootloader and partition table.
async function prepareFirmware(bytes, assetRoot) {
  if (bytes.length === FLASH_SIZE) {
    return bytes;
  }
  const [bootloader, partitions] = await Promise.all([
    fetchBin(new URL('assets/esp32c3-bootloader.bin', assetRoot)),
    fetchBin(new URL('assets/crosspoint-partitions.bin', assetRoot)),
  ]);
  return mergeFirmware(bytes, bootloader, partitions);
}

export function setButton(module, name, pressed) {
  const button = BUTTONS[name];
  if (!button) {
    throw new Error(`Unknown button: ${name}`);
  }
  if (button.type === 'adc') {
    module._xteink_wasm_set_adc(button.channel, pressed ? button.value : RELEASED_ADC);
  } else {
    module._xteink_wasm_set_gpio(button.pin, pressed ? 0 : 1);
  }
}

function drawFrame(module, canvas) {
  const width = module._xteink_wasm_width();
  const height = module._xteink_wasm_height();
  const stride = module._xteink_wasm_stride();
  const pointer = module._xteink_wasm_framebuffer();
  if (!width || !height || !stride || !pointer) {
    return false;
  }

  if (canvas.width !== width || canvas.height !== height) {
    canvas.width = width;
    canvas.height = height;
  }

  const source = module.HEAPU8;
  const image = new ImageData(width, height);
  for (let y = 0; y < height; y++) {
    for (let x = 0; x < width; x++) {
      const sourceOffset = pointer + y * stride + x * 4;
      const targetOffset = (y * width + x) * 4;
      image.data[targetOffset] = source[sourceOffset];
      image.data[targetOffset + 1] = source[sourceOffset + 1];
      image.data[targetOffset + 2] = source[sourceOffset + 2];
      image.data[targetOffset + 3] = 255;
    }
  }
  canvas.getContext('2d').putImageData(image, 0, 0);
  return true;
}

function startDisplayLoop(module, canvas, setStatus, onReady) {
  let generation = -1;
  let ready = false;
  const update = () => {
    const nextGeneration = module._xteink_wasm_frame_generation();
    if (nextGeneration !== generation && drawFrame(module, canvas)) {
      generation = nextGeneration;
      setStatus('Running.');
      if (!ready) {
        ready = true;
        onReady();
      }
    }
    requestAnimationFrame(update);
  };
  requestAnimationFrame(update);
}

function enableControls(module) {
  for (const element of document.querySelectorAll('[data-button]')) {
    element.disabled = false;
    let pressed = false;

    const press = () => {
      if (!pressed) {
        pressed = true;
        element.classList.add('active');
        setButton(module, element.dataset.button, true);
      }
    };
    const release = () => {
      if (pressed) {
        pressed = false;
        element.classList.remove('active');
        setButton(module, element.dataset.button, false);
      }
    };

    element.addEventListener('pointerdown', event => {
      element.setPointerCapture(event.pointerId);
      press();
    });
    element.addEventListener('pointerup', release);
    element.addEventListener('pointercancel', release);
    element.addEventListener('lostpointercapture', release);
    element.addEventListener('keydown', event => {
      if (!event.repeat && (event.key === ' ' || event.key === 'Enter')) {
        event.preventDefault();
        press();
      }
    });
    element.addEventListener('keyup', event => {
      if (event.key === ' ' || event.key === 'Enter') {
        event.preventDefault();
        release();
      }
    });
    element.addEventListener('blur', release);
  }
}

let logEl = null;
const logBuffer = [];
const LOG_MAX_LINES = 1000;

function logLine(message) {
  logBuffer.push(message);
  if (logBuffer.length > LOG_MAX_LINES) {
    logBuffer.splice(0, logBuffer.length - LOG_MAX_LINES);
  }
  if (logEl) {
    const atBottom = logEl.scrollTop + logEl.clientHeight >= logEl.scrollHeight - 4;
    logEl.textContent = logBuffer.join('\n');
    if (atBottom) {
      logEl.scrollTop = logEl.scrollHeight;
    }
  }
}

async function boot(file, variant, setStatus) {
  if (!crossOriginIsolated) {
    throw new Error('This emulator requires COOP/COEP headers. Start it with `make web`.');
  }
  setStatus('Loading firmware…');

  const firmware = await prepareFirmware(new Uint8Array(await file.arrayBuffer()), import.meta.url);
  const artifactRoot = new URL('../dist/wasm/', import.meta.url);
  const qemuUrl = new URL('qemu-system-riscv32.js', artifactRoot);
  const rom = new Uint8Array(await fetch(new URL('esp32c3-rom.bin', artifactRoot)).then(response => {
    if (!response.ok) {
      throw new Error(`Could not load ESP32-C3 ROM (${response.status}).`);
    }
    return response.arrayBuffer();
  }));
  const { default: createQemu } = await import(qemuUrl);

  const options = {
    arguments: [
      '-machine', `xteink,variant=${variant}`,
      '-L', '/bios',
      '-display', 'none',
      '-serial', 'stdio',
      '-nic', 'none',
      '-d', 'guest_errors,unimp',
      '-drive', 'file=/flash.bin,if=mtd,format=raw',
    ],
    locateFile: path => new URL(path, artifactRoot).href,
    mainScriptUrlOrBlob: qemuUrl.href,
    print: message => { console.log(message); logLine(message); },
    printErr: message => { console.error(message); logLine(message); },
    stdin: () => null,
  };
  options.preRun = [() => {
    options.FS.mkdir('/bios');
    options.FS.writeFile('/bios/esp32c3-rom.bin', rom);
    options.FS.writeFile('/flash.bin', firmware);
  }];

  setStatus('Starting emulator…');
  return createQemu(options);
}

function initialize() {
  const form = document.querySelector('#boot-form');
  const firmwareInput = document.querySelector('#firmware');
  const variantInput = document.querySelector('#variant');
  const bootButton = document.querySelector('#boot');
  const status = document.querySelector('#status');
  const canvas = document.querySelector('#screen');
  logEl = document.querySelector('#log');
  document.querySelector('#log-clear').addEventListener('click', () => {
    logBuffer.length = 0;
    logEl.textContent = '';
  });

  const setStatus = (message, error = false) => {
    status.textContent = message;
    status.classList.toggle('error', error);
  };

  form.addEventListener('submit', async event => {
    event.preventDefault();
    const file = firmwareInput.files[0];
    if (!file) {
      setStatus('Choose a firmware image first.', true);
      return;
    }

    bootButton.disabled = true;
    firmwareInput.disabled = true;
    variantInput.disabled = true;
    try {
      const module = await boot(file, variantInput.value, setStatus);
      startDisplayLoop(module, canvas, setStatus, () => enableControls(module));
    } catch (error) {
      console.error(error);
      setStatus(error.message || String(error), true);
      bootButton.disabled = false;
      firmwareInput.disabled = false;
      variantInput.disabled = false;
    }
  });
}

if (typeof document !== 'undefined') {
  initialize();
}