import {
  cpSync,
  existsSync,
  readFileSync,
  renameSync,
  rmSync,
  writeFileSync,
} from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";
import {
  DEFAULT_WINDOWS_ICON,
  embedWindowsAppIcons,
} from "./embed-windows-exe-icon.mjs";

const rootDir = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");

/** User-facing Windows app entry point (Electrobun launcher). */
export const WINDOWS_APP_EXECUTABLE = "farmcontrol-server.exe";

/**
 * Bun runtime filename embedded in the Electrobun launcher binary.
 * Must stay exactly 7 characters (same length as "bun.exe") for binary patching.
 */
export const WINDOWS_RUNTIME_EXECUTABLE = "farm.exe";

const LAUNCHER_BINARY = "launcher.exe";
const LEGACY_RUNTIME_BINARY = "bun.exe";
const LAUNCHER_RUNTIME_REFERENCE = Buffer.from(`${LEGACY_RUNTIME_BINARY}\0`);
const PATCHED_RUNTIME_REFERENCE = Buffer.from(`${WINDOWS_RUNTIME_EXECUTABLE}\0`);

function patchLauncherRuntimeReference(launcherPath) {
  const binary = readFileSync(launcherPath);
  const index = binary.indexOf(LAUNCHER_RUNTIME_REFERENCE);
  if (index === -1) {
    if (binary.includes(PATCHED_RUNTIME_REFERENCE)) {
      return;
    }

    throw new Error(
      `prepare-windows-app-binaries: could not find ${LEGACY_RUNTIME_BINARY} reference in ${launcherPath}`,
    );
  }

  PATCHED_RUNTIME_REFERENCE.copy(binary, index);
  writeFileSync(launcherPath, binary);
  console.log(
    `prepare-windows-app-binaries: patched ${path.basename(launcherPath)} to spawn ${WINDOWS_RUNTIME_EXECUTABLE}`,
  );
}

function renameWindowsRuntime(binDir) {
  const legacyRuntimePath = path.join(binDir, LEGACY_RUNTIME_BINARY);
  const runtimePath = path.join(binDir, WINDOWS_RUNTIME_EXECUTABLE);

  if (existsSync(runtimePath)) {
    return runtimePath;
  }

  if (!existsSync(legacyRuntimePath)) {
    throw new Error(
      `prepare-windows-app-binaries: neither ${LEGACY_RUNTIME_BINARY} nor ${WINDOWS_RUNTIME_EXECUTABLE} found in ${binDir}`,
    );
  }

  renameSync(legacyRuntimePath, runtimePath);
  console.log(
    `prepare-windows-app-binaries: renamed ${LEGACY_RUNTIME_BINARY} -> ${WINDOWS_RUNTIME_EXECUTABLE}`,
  );
  return runtimePath;
}

function createBrandedAppExecutable(binDir) {
  const launcherPath = path.join(binDir, LAUNCHER_BINARY);
  const appExecutablePath = path.join(binDir, WINDOWS_APP_EXECUTABLE);

  if (!existsSync(launcherPath)) {
    if (existsSync(appExecutablePath)) {
      patchLauncherRuntimeReference(appExecutablePath);
      return appExecutablePath;
    }

    throw new Error(
      `prepare-windows-app-binaries: ${LAUNCHER_BINARY} not found in ${binDir}`,
    );
  }

  patchLauncherRuntimeReference(launcherPath);
  cpSync(launcherPath, appExecutablePath);
  rmSync(launcherPath, { force: true });
  console.log(
    `prepare-windows-app-binaries: created ${WINDOWS_APP_EXECUTABLE} and removed ${LAUNCHER_BINARY}`,
  );
  return appExecutablePath;
}

/**
 * Brand Windows app binaries and embed icons per Electrobun application-icons docs:
 * launcher executable, Bun runtime executable, then NSIS installer (separately).
 */
export async function prepareWindowsAppBinaries(appDir) {
  if (process.platform !== "win32") {
    console.log("prepare-windows-app-binaries: skipped (not Windows)");
    return;
  }

  const binDir = path.join(appDir, "bin");
  if (!existsSync(binDir)) {
    throw new Error(`prepare-windows-app-binaries: bin directory not found: ${binDir}`);
  }

  const launcherPath = path.join(binDir, LAUNCHER_BINARY);
  if (existsSync(launcherPath)) {
    await embedWindowsAppIcons([launcherPath], { icon: DEFAULT_WINDOWS_ICON });
  }

  const runtimePath = renameWindowsRuntime(binDir);
  const appExecutablePath = createBrandedAppExecutable(binDir);

  await embedWindowsAppIcons([appExecutablePath, runtimePath], {
    icon: DEFAULT_WINDOWS_ICON,
    cleanupTemp: true,
  });
}