/**
 * HTTP client helpers for runner communication
 * Used by CLI commands to interact with running runner
 */

import { logger } from '@/ui/logger';
import { clearRunnerState, readRunnerState, readSettings } from '@/persistence';
import { Metadata } from '@/api/types';
import packageJson from '../../package.json';
import { existsSync, statSync } from 'node:fs';
import { join } from 'node:path';
import { isBunCompiled, projectPath } from '@/projectPath';
import { isProcessAlive, getHapiRunnerProcessIdentity, killProcess } from '@/utils/process';
import { configuration } from '@/configuration';
import { hashRunnerCliApiToken, hashRunnerExtraHeaders, isRunnerStateCompatibleWithIdentity } from './runnerIdentity';

export function getInstalledCliMtimeMs(): number | undefined {
  if (isBunCompiled()) {
    try {
      return statSync(process.execPath).mtimeMs;
    } catch {
      return undefined;
    }
  }

  const packageJsonPath = join(projectPath(), 'package.json');
  if (!existsSync(packageJsonPath)) {
    return undefined;
  }

  try {
    return statSync(packageJsonPath).mtimeMs;
  } catch {
    return undefined;
  }
}

async function runnerPost(path: string, body?: any): Promise<{ error?: string } | any> {
  const state = await readRunnerState();
  if (!state?.httpPort) {
    const errorMessage = 'No runner running, no state file found';
    logger.debug(`[CONTROL CLIENT] ${errorMessage}`);
    return {
      error: errorMessage
    };
  }

  if (!isProcessAlive(state.pid)) {
    const errorMessage = 'Runner is not running, file is stale';
    logger.debug(`[CONTROL CLIENT] ${errorMessage}`);
    return {
      error: errorMessage
    };
  }

  try {
    const timeout = process.env.HAPI_RUNNER_HTTP_TIMEOUT ? parseInt(process.env.HAPI_RUNNER_HTTP_TIMEOUT) : 10_000;
    const response = await fetch(`http://127.0.0.1:${state.httpPort}${path}`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(body || {}),
      // Mostly increased for stress test
      signal: AbortSignal.timeout(timeout)
    });
    
    if (!response.ok) {
      const errorMessage = `Request failed: ${path}, HTTP ${response.status}`;
      logger.debug(`[CONTROL CLIENT] ${errorMessage}`);
      return {
        error: errorMessage
      };
    }
    
    return await response.json();
  } catch (error) {
    const errorMessage = `Request failed: ${path}, ${error instanceof Error ? error.message : 'Unknown error'}`;
    logger.debug(`[CONTROL CLIENT] ${errorMessage}`);
    return {
      error: errorMessage
    }
  }
}

export async function notifyRunnerSessionStarted(
  sessionId: string,
  metadata: Metadata
): Promise<{ error?: string } | any> {
  return await runnerPost('/session-started', {
    sessionId,
    metadata
  });
}

export async function listRunnerSessions(): Promise<any[]> {
  const result = await runnerPost('/list');
  return result.children || [];
}

export async function stopRunnerSession(sessionId: string): Promise<'stopped' | 'already_gone' | 'still_alive' | 'unknown'> {
  const result = await runnerPost('/stop-session', { sessionId });
  return result.status === 'stopped' || result.status === 'already_gone' || result.status === 'still_alive' || result.status === 'unknown'
    ? result.status
    : 'still_alive';
}

export async function spawnRunnerSession(directory: string, sessionId?: string): Promise<any> {
  const result = await runnerPost('/spawn-session', { directory, sessionId });
  return result;
}

export async function stopRunnerHttp(): Promise<void> {
  await runnerPost('/stop');
}

/**
 * The version check is still quite naive.
 * For instance we are not handling the case where we upgraded hapi,
 * the runner is still running, and it recieves a new message to spawn a new session.
 * This is a tough case - we need to somehow figure out to restart ourselves,
 * yet still handle the original request.
 * 
 * Options:
 * 1. Periodically check during the health checks whether our version is the same as CLIs version. If not - restart.
 * 2. Wait for a command from the machine session, or any other signal to
 * check for version & restart.
 *   a. Handle the request first
 *   b. Let the request fail, restart and rely on the client retrying the request
 * 
 * I like option 1 a little better.
 * Maybe we can ... wait for it ... have another runner to make sure 
 * our runner is always alive and running the latest version.
 * 
 * That seems like an overkill and yet another process to manage - lets not do this :D
 * 
 * TODO: This function should return a state object with
 * clear state - if it is running / or errored out or something else.
 * Not just a boolean.
 * 
 * We can destructure the response on the caller for richer output.
 * For instance when running `hapi runner status` we can show more information.
 */
export async function checkIfRunnerRunningAndCleanupStaleState(): Promise<boolean> {
  const state = await readRunnerState();
  if (!state) {
    return false;
  }

  // Verify PID is alive AND belongs to hapi (not a reused PID from another process)
  const identity = getHapiRunnerProcessIdentity(state.pid);
  if (identity === 'runner') {
    return true;
  }

  if (identity === 'unknown') {
    // The pid is alive but unidentifiable. Reporting it as the runner would let
    // callers signal a process that may not be ours, and clearing the state would
    // drop the lock that keeps a second runner from starting. Do neither.
    logger.debug('[RUNNER RUN] Runner PID could not be identified, leaving state untouched');
    return false;
  }

  logger.debug('[RUNNER RUN] Runner PID not running or not a hapi process, cleaning up state');
  await cleanupRunnerState();
  return false;
}

/**
 * Check if the running runner version matches the current CLI version.
 * This should work from both the runner itself & a new CLI process.
 * Works via the runner.state.json file.
 * 
 * @returns true if versions match, false if versions differ or no runner running
 */
export async function isRunnerRunningCurrentlyInstalledHappyVersion(): Promise<boolean> {
  logger.debug('[RUNNER CONTROL] Checking if runner is running same version');
  const runningRunner = await checkIfRunnerRunningAndCleanupStaleState();
  if (!runningRunner) {
    logger.debug('[RUNNER CONTROL] No runner running, returning false');
    return false;
  }

  const state = await readRunnerState();
  if (!state) {
    logger.debug('[RUNNER CONTROL] No runner state found, returning false');
    return false;
  }

  const settings = await readSettings();
  const currentApiUrl = process.env.HAPI_API_URL
    || settings.apiUrl
    || settings.serverUrl
    || configuration.apiUrl;
  const currentCliApiToken = process.env.CLI_API_TOKEN
    || settings.cliApiToken
    || configuration.cliApiToken;
  const currentMachineId = settings.machineId;
  
  try {
    // When HAPI_DISABLE_VERSION_HANDOFF=1 is set on the live runner (operator
    // owns supervision via systemd/tmux/custom rebuild pipelines), a fresh CLI invocation must NOT
    // treat the running runner as stale just because source mtimes shifted.
    // Otherwise `hapi runner start` would kill the live runner mid-rebuild.
    //
    // Per Codex review #814 [Major]: the env var is commonly only set on the
    // supervising service (systemd unit file), NOT on the operator's
    // interactive shell. To honour the running runner's opt-out from any
    // caller, OR the live env-var check with the persisted-at-start snapshot
    // in state.startedWithVersionHandoffDisabled.
    if (
      process.env.HAPI_DISABLE_VERSION_HANDOFF === '1'
      || state.startedWithVersionHandoffDisabled === true
    ) {
      logger.debug('[RUNNER CONTROL] Version handoff disabled (env or persisted state), skipping mtime/version drift check');
    } else {
      const currentCliMtimeMs = getInstalledCliMtimeMs();
      if (typeof currentCliMtimeMs === 'number' && typeof state.startedWithCliMtimeMs === 'number') {
        logger.debug(`[RUNNER CONTROL] Current CLI mtime: ${currentCliMtimeMs}, Runner started with mtime: ${state.startedWithCliMtimeMs}`);
        if (currentCliMtimeMs !== state.startedWithCliMtimeMs) {
          return false;
        }
      } else {
        const currentCliVersion = packageJson.version;
        logger.debug(`[RUNNER CONTROL] Current CLI version: ${currentCliVersion}, Runner started with version: ${state.startedWithCliVersion}`);
        if (currentCliVersion !== state.startedWithCliVersion) {
          return false;
        }
      }
    }

    const currentIdentityMatches = isRunnerStateCompatibleWithIdentity(state, {
      apiUrl: currentApiUrl,
      machineId: currentMachineId,
      cliApiTokenHash: hashRunnerCliApiToken(currentCliApiToken),
      extraHeadersHash: hashRunnerExtraHeaders(configuration.extraHeaders)
    });
    logger.debug(`[RUNNER CONTROL] Runner identity match: ${currentIdentityMatches}`, {
      currentApiUrl,
      currentMachineId,
      runnerStartedWithApiUrl: state.startedWithApiUrl,
      runnerStartedWithMachineId: state.startedWithMachineId
    });
    return currentIdentityMatches;
  } catch (error) {
    logger.debug('[RUNNER CONTROL] Error checking runner version', error);
    return false;
  }
}

/**
 * Poll the runner state file waiting for a different PID to take ownership.
 * Used by the self-restart handoff in run.ts so the dying runner does not exit
 * until its replacement has actually come up and written its own state.
 *
 * Returns true when runner.state.json shows a different (and live) PID than
 * `oldPid`, false on timeout.
 */
export async function waitForRunnerHandoff(
  oldPid: number,
  options: { timeoutMs?: number; pollIntervalMs?: number } = {}
): Promise<boolean> {
  const timeoutMs = options.timeoutMs ?? 30_000;
  const pollIntervalMs = options.pollIntervalMs ?? 500;
  const deadline = Date.now() + timeoutMs;

  while (Date.now() < deadline) {
    try {
      const state = await readRunnerState();
      if (state && state.pid !== oldPid && isProcessAlive(state.pid)) {
        logger.debug(`[RUNNER CONTROL] Handoff confirmed: new runner PID ${state.pid} replaced ${oldPid}`);
        return true;
      }
    } catch (error) {
      logger.debug('[RUNNER CONTROL] Error polling runner state during handoff wait', error);
    }
    await new Promise(resolve => setTimeout(resolve, pollIntervalMs));
  }
  logger.debug(`[RUNNER CONTROL] Handoff timeout: no replacement runner registered within ${timeoutMs}ms`);
  return false;
}

export async function cleanupRunnerState(): Promise<void> {
  try {
    await clearRunnerState();
    logger.debug('[RUNNER RUN] Runner state file removed');
  } catch (error) {
    logger.debug('[RUNNER RUN] Error cleaning up runner metadata', error);
  }
}

export async function stopRunner() {
  try {
    const state = await readRunnerState();
    if (!state) {
      logger.debug('No runner state found');
      return;
    }

    // Every stop is a signal to the persisted pid and port, so gate the whole
    // sequence on a confirmed identity. Callers derive their decision from a
    // boolean, and a pid we cannot identify may belong to an unrelated process
    // that reused it, whose port may have been reused as well.
    const identity = getHapiRunnerProcessIdentity(state.pid);
    if (identity !== 'runner') {
      logger.debug(`Not stopping PID ${state.pid}: identity is ${identity}`);
      return;
    }

    logger.debug(`Stopping runner with PID ${state.pid}`);

    // Try HTTP graceful stop
    try {
      await stopRunnerHttp();

      // Wait for runner to die
      await waitForProcessDeath(state.pid, 2000);
      logger.debug('Runner stopped gracefully via HTTP');
      return;
    } catch (error) {
      logger.debug('HTTP stop failed, will force kill', error);
    }

    const killed = await killProcess(state.pid, true);
    if (killed) {
      logger.debug('Force killed runner');
    } else {
      logger.debug('Runner already dead or could not be killed');
    }
  } catch (error) {
    logger.debug('Error stopping runner', error);
  }
}

async function waitForProcessDeath(pid: number, timeout: number): Promise<void> {
  const start = Date.now();
  while (Date.now() - start < timeout) {
    if (isProcessAlive(pid)) {
      await new Promise(resolve => setTimeout(resolve, 100));
      continue;
    }
    return; // Process is dead
  }
  throw new Error('Process did not die within timeout');
}