const { spawn } = require("node:child_process");
const fs = require("node:fs/promises");
const path = require("node:path");

const repoRoot = path.resolve(__dirname, "../../..");
const docsDir = path.resolve(repoRoot, "apps/docs");
const stateFile = path.resolve(repoRoot, ".artifacts/test-results/storybook-server.json");

const baseURL = "http://127.0.0.1:6006";
const startupTimeoutMs = 120_000;
const shutdownTimeoutMs = 10_000;
const pollIntervalMs = 250;
const storybookCommand = process.platform === "win32" ? "pnpm.cmd" : "pnpm";
const storybookArgs = ["run", "storybook"];
const reuseExistingServer = !process.env.CI;

function sleep(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

async function isServerResponsive() {
  try {
    const response = await fetch(baseURL, {
      redirect: "manual",
      signal: AbortSignal.timeout(1_000)
    });

    return response.status < 404 || [400, 401, 402, 403].includes(response.status);
  } catch {
    return false;
  }
}

async function waitFor(condition, timeoutMs, failureMessage) {
  const deadline = Date.now() + timeoutMs;

  while (Date.now() < deadline) {
    if (await condition()) {
      return;
    }

    await sleep(pollIntervalMs);
  }

  throw new Error(failureMessage);
}

async function ensureStateDir() {
  await fs.mkdir(path.dirname(stateFile), { recursive: true });
}

async function readServerState() {
  try {
    const raw = await fs.readFile(stateFile, "utf8");
    return JSON.parse(raw);
  } catch {
    return null;
  }
}

async function clearServerState() {
  await fs.rm(stateFile, { force: true });
}

async function stopProcess(pid) {
  try {
    if (process.platform === "win32") {
      process.kill(pid, "SIGTERM");
    } else {
      process.kill(-pid, "SIGTERM");
    }
  } catch (error) {
    if (error && error.code === "ESRCH") {
      return;
    }

    throw error;
  }

  try {
    await waitFor(
      async () => !(await isServerResponsive()),
      shutdownTimeoutMs,
      `Timed out waiting ${shutdownTimeoutMs}ms for Storybook to stop.`
    );
  } catch {
    try {
      if (process.platform === "win32") {
        process.kill(pid, "SIGKILL");
      } else {
        process.kill(-pid, "SIGKILL");
      }
    } catch (error) {
      if (!error || error.code !== "ESRCH") {
        throw error;
      }
    }
  }
}

async function startStorybookServer() {
  if (await isServerResponsive()) {
    if (reuseExistingServer) {
      return;
    }

    throw new Error(`${baseURL} is already in use, and CI runs must start their own Storybook server.`);
  }

  const child = spawn(storybookCommand, storybookArgs, {
    cwd: docsDir,
    detached: process.platform !== "win32",
    env: process.env,
    shell: false,
    stdio: "ignore"
  });

  const exitPromise = new Promise((_, reject) => {
    child.once("error", (error) => {
      reject(error);
    });

    child.once("exit", (code, signal) => {
      reject(
        new Error(
          `Storybook exited before becoming ready (code: ${code ?? "null"}, signal: ${signal ?? "null"}).`
        )
      );
    });
  });

  try {
    await Promise.race([
      waitFor(
        async () => isServerResponsive(),
        startupTimeoutMs,
        `Timed out waiting ${startupTimeoutMs}ms for Storybook on ${baseURL}.`
      ),
      exitPromise
    ]);
  } catch (error) {
    await stopProcess(child.pid);
    throw error;
  }

  child.unref();

  await ensureStateDir();
  await fs.writeFile(stateFile, JSON.stringify({ pid: child.pid }, null, 2));
}

async function stopStorybookServer() {
  const state = await readServerState();

  if (!state) {
    return;
  }

  try {
    await stopProcess(state.pid);
  } finally {
    await clearServerState();
  }
}

module.exports = {
  clearServerState,
  readServerState,
  startStorybookServer,
  stopStorybookServer
};