/**
 * ProcessManager — Subprocess lifecycle, worktree creation, command building.
 *
 * Extracted from MultiProviderAgentManager. Manages the spawning of detached
 * subprocesses, worktree creation per project, and provider-specific command
 * construction.
 */

import { spawn } from 'node:child_process';
import { openSync, closeSync, existsSync } from 'node:fs';
import { mkdir, writeFile } from 'node:fs/promises';
import { join } from 'node:path';
import type { ProjectRepository } from '../db/repositories/project-repository.js';
import type { AgentProviderConfig } from './providers/types.js';
import type { StreamEvent } from './providers/parsers/index.js';
import { getStreamParser } from './providers/parsers/index.js';
import { SimpleGitWorktreeManager } from '../git/manager.js';
import { ensureProjectClone, getProjectCloneDir } from '../git/project-clones.js';
import { FileTailer } from './file-tailer.js';
import { createModuleLogger } from '../logger/index.js';

const log = createModuleLogger('process-manager');

/**
 * Check if a process with the given PID is still alive.
 */
export function isPidAlive(pid: number): boolean {
  try {
    process.kill(pid, 0);
    return true;
  } catch {
    return false;
  }
}

export class ProcessManager {
  constructor(
    private workspaceRoot: string,
    private projectRepository: ProjectRepository,
  ) {}

  /**
   * Resolve the agent's working directory path.
   */
  getAgentWorkdir(alias: string): string {
    return join(this.workspaceRoot, 'agent-workdirs', alias);
  }

  /**
   * Create worktrees for all projects linked to an initiative.
   * Returns the base agent workdir path.
   */
  async createProjectWorktrees(
    alias: string,
    initiativeId: string,
    baseBranch?: string,
    branchName?: string,
  ): Promise<string> {
    const projects = await this.projectRepository.findProjectsByInitiativeId(initiativeId);
    const agentWorkdir = this.getAgentWorkdir(alias);

    log.debug({
      alias,
      initiativeId,
      projectCount: projects.length,
      agentWorkdir,
      baseBranch
    }, 'creating project worktrees');

    // No linked projects — fall back to standalone worktree so the agent
    // always has a git-backed working directory.
    if (projects.length === 0) {
      log.info({ alias, initiativeId }, 'initiative has no linked projects, falling back to standalone worktree');
      return this.createStandaloneWorktree(alias);
    }

    for (const project of projects) {
      const clonePath = await ensureProjectClone(project, this.workspaceRoot);
      const worktreeManager = new SimpleGitWorktreeManager(clonePath, undefined, agentWorkdir);
      const effectiveBaseBranch = baseBranch ?? project.defaultBranch;
      const worktree = await worktreeManager.create(project.name, branchName ?? `agent/${alias}`, effectiveBaseBranch);
      const worktreePath = worktree.path;
      const pathExists = existsSync(worktreePath);

      log.debug({
        alias,
        agentWorkdir,
        projectName: project.name,
        worktreePath,
        pathExists
      }, 'worktree created');

      if (!pathExists) {
        log.error({ worktreePath }, 'Worktree path does not exist after creation!');
        throw new Error(`Worktree creation failed: ${worktreePath}`);
      }
    }

    return agentWorkdir;
  }

  /**
   * Fallback: create a single "workspace" worktree for standalone agents.
   */
  async createStandaloneWorktree(alias: string): Promise<string> {
    const agentWorkdir = this.getAgentWorkdir(alias);
    const worktreeManager = new SimpleGitWorktreeManager(this.workspaceRoot, undefined, agentWorkdir);

    log.debug({ alias, agentWorkdir }, 'creating standalone worktree');

    const worktree = await worktreeManager.create('workspace', `agent/${alias}`);
    const worktreePath = worktree.path;
    const pathExists = existsSync(worktreePath);

    log.debug({
      alias,
      agentWorkdir,
      worktreePath,
      pathExists
    }, 'standalone worktree created');

    if (!pathExists) {
      log.error({ worktreePath }, 'Standalone worktree path does not exist after creation!');
      throw new Error(`Standalone worktree creation failed: ${worktreePath}`);
    }

    return worktree.path;
  }

  /**
   * Build the spawn command for a given provider configuration.
   */
  buildSpawnCommand(
    provider: AgentProviderConfig,
    prompt: string,
  ): { command: string; args: string[]; env: Record<string, string> } {
    const args = [...provider.args];
    const env: Record<string, string> = { ...provider.env };

    if (provider.nonInteractive?.subcommand) {
      args.unshift(provider.nonInteractive.subcommand);
    }

    if (provider.promptMode === 'native') {
      args.push('-p', prompt);
    } else if (provider.promptMode === 'flag' && provider.nonInteractive?.promptFlag) {
      args.push(provider.nonInteractive.promptFlag, prompt);
    }

    if (provider.nonInteractive?.outputFlag) {
      args.push(...provider.nonInteractive.outputFlag.split(' '));
    }

    return { command: provider.command, args, env };
  }

  /**
   * Build the resume command for a given provider configuration.
   */
  buildResumeCommand(
    provider: AgentProviderConfig,
    sessionId: string,
    prompt: string,
  ): { command: string; args: string[]; env: Record<string, string> } {
    const args = [...provider.args];
    const env: Record<string, string> = { ...provider.env };

    switch (provider.resumeStyle) {
      case 'flag':
        args.push(provider.resumeFlag!, sessionId);
        break;
      case 'subcommand':
        if (provider.nonInteractive?.subcommand) {
          args.unshift(provider.nonInteractive.subcommand);
        }
        args.push(provider.resumeFlag!, sessionId);
        break;
      case 'none':
        throw new Error(`Provider '${provider.name}' does not support resume`);
    }

    if (provider.promptMode === 'native') {
      args.push('-p', prompt);
    } else if (provider.promptMode === 'flag' && provider.nonInteractive?.promptFlag) {
      args.push(provider.nonInteractive.promptFlag, prompt);
    }

    if (provider.nonInteractive?.outputFlag) {
      args.push(...provider.nonInteractive.outputFlag.split(' '));
    }

    return { command: provider.command, args, env };
  }

  /**
   * Extract session ID from CLI output based on provider config.
   */
  extractSessionId(
    provider: AgentProviderConfig,
    output: string,
  ): string | null {
    if (!provider.sessionId) return null;

    try {
      if (provider.sessionId.extractFrom === 'result') {
        const parsed = JSON.parse(output);
        return parsed[provider.sessionId.field] ?? null;
      }

      if (provider.sessionId.extractFrom === 'event') {
        const lines = output.trim().split('\n');
        for (const line of lines) {
          try {
            const event = JSON.parse(line);
            if (event.type === provider.sessionId.eventType) {
              return event[provider.sessionId.field] ?? null;
            }
          } catch {
            // Skip non-JSON lines
          }
        }
      }
    } catch {
      // Parse failure
    }

    return null;
  }

  /**
   * Spawn a detached subprocess with file redirection for crash resilience.
   * The subprocess writes directly to files and survives server crashes.
   * A FileTailer watches the output file and emits events in real-time.
   *
   * @param onEvent - Callback for stream events from the tailer
   */
  async spawnDetached(
    agentId: string,
    agentName: string,
    command: string,
    args: string[],
    cwd: string,
    env: Record<string, string>,
    providerName: string,
    prompt?: string,
    onEvent?: (event: StreamEvent) => void,
    onRawContent?: (content: string) => void,
  ): Promise<{ pid: number; outputFilePath: string; tailer: FileTailer }> {
    // Pre-spawn validation and logging
    const cwdExists = existsSync(cwd);
    const commandWithArgs = [command, ...args].join(' ');

    // Log environment variables that might affect working directory
    const environmentInfo = {
      PWD: process.env.PWD,
      HOME: process.env.HOME,
      CLAUDE_CONFIG_DIR: env.CLAUDE_CONFIG_DIR,
      CW_CONFIG_DIR: env.CW_CONFIG_DIR
    };

    log.info({
      agentId,
      cwd,
      cwdExists,
      commandWithArgs,
      providerName,
      environmentInfo
    }, 'spawning detached process with workdir validation');

    if (!cwdExists) {
      log.error({ cwd }, 'CWD does not exist before spawn!');
      throw new Error(`Agent working directory does not exist: ${cwd}`);
    }

    const logDir = join(this.workspaceRoot, '.cw', 'agent-logs', agentName);
    await mkdir(logDir, { recursive: true });
    const outputFilePath = join(logDir, 'output.jsonl');
    const stderrFilePath = join(logDir, 'stderr.log');

    if (prompt) {
      await writeFile(join(logDir, 'PROMPT.md'), prompt, 'utf-8');
    }

    const stdoutFd = openSync(outputFilePath, 'w');
    const stderrFd = openSync(stderrFilePath, 'w');

    const child = spawn(command, args, {
      cwd,
      env: { ...process.env, ...env },
      detached: true,
      stdio: ['ignore', stdoutFd, stderrFd],
    });

    closeSync(stdoutFd);
    closeSync(stderrFd);

    child.unref();

    const pid = child.pid!;
    log.info({
      agentId,
      pid,
      command,
      args: args.join(' '),
      cwd,
      spawnSuccess: true
    }, 'spawned detached process successfully');

    const parser = getStreamParser(providerName);
    const tailer = new FileTailer({
      filePath: outputFilePath,
      agentId,
      parser,
      onEvent: onEvent ?? (() => {}),
      startFromBeginning: true,
      onRawContent,
    });

    tailer.start().catch((err) => {
      log.warn({ agentId, err: err instanceof Error ? err.message : String(err) }, 'failed to start tailer');
    });

    return { pid, outputFilePath, tailer };
  }

  /**
   * Poll for process completion by checking if PID is still alive.
   * When the process exits, calls onComplete callback.
   * Returns a cancel handle to stop polling (e.g. on agent cleanup or re-resume).
   *
   * Optionally checks signal.json after a grace period to detect hung processes
   * that completed work but failed to exit. If a valid signal is found while the
   * process is still alive, SIGTERM is sent and normal completion proceeds.
   *
   * @param onComplete - Called when the process is no longer alive
   * @param getTailer - Function to get the current tailer for final flush
   * @param checkEarlyCompletion - Optional callback that returns true if signal.json indicates completion
   */
  pollForCompletion(
    agentId: string,
    pid: number,
    onComplete: () => Promise<void>,
    getTailer: () => FileTailer | undefined,
    checkEarlyCompletion?: () => Promise<boolean>,
  ): { cancel: () => void } {
    let cancelled = false;
    const startTime = Date.now();
    const GRACE_PERIOD_MS = 60_000;
    const SIGNAL_CHECK_INTERVAL_MS = 30_000;
    let lastSignalCheck = 0;

    const finalize = async () => {
      const tailer = getTailer();
      if (tailer) {
        await new Promise((resolve) => setTimeout(resolve, 500));
        await tailer.stop();
      }
      if (!cancelled) await onComplete();
    };

    const check = async () => {
      if (cancelled) return;
      if (!isPidAlive(pid)) {
        await finalize();
        return;
      }

      // Defensive signal check: after grace period, periodically check signal.json
      if (checkEarlyCompletion) {
        const elapsed = Date.now() - startTime;
        if (elapsed >= GRACE_PERIOD_MS && Date.now() - lastSignalCheck >= SIGNAL_CHECK_INTERVAL_MS) {
          lastSignalCheck = Date.now();
          try {
            const hasSignal = await checkEarlyCompletion();
            if (hasSignal) {
              log.warn({ agentId, pid, elapsedMs: elapsed }, 'signal.json found but process still alive — sending SIGTERM');
              try { process.kill(pid, 'SIGTERM'); } catch { /* already dead */ }
              await new Promise((resolve) => setTimeout(resolve, 2000));
              await finalize();
              return;
            }
          } catch (err) {
            log.debug({ agentId, err: err instanceof Error ? err.message : String(err) }, 'early completion check failed');
          }
        }
      }

      if (!cancelled) setTimeout(check, 1000);
    };
    check();
    return { cancel: () => { cancelled = true; } };
  }

  /**
   * Wait for a process to complete with Promise-based API.
   * Returns when the process is no longer alive.
   */
  async waitForProcessCompletion(pid: number, timeoutMs: number = 300000): Promise<{ exitCode: number | null }> {
    return new Promise((resolve, reject) => {
      const startTime = Date.now();

      const check = () => {
        if (!isPidAlive(pid)) {
          // Process has exited, try to get exit code
          // Note: Getting exact exit code from detached process is limited
          resolve({ exitCode: null });
          return;
        }

        if (Date.now() - startTime > timeoutMs) {
          reject(new Error(`Process ${pid} did not complete within ${timeoutMs}ms`));
          return;
        }

        setTimeout(check, 1000);
      };

      check();
    });
  }

  /**
   * Get the exit code of a completed process.
   * Limited implementation since we use detached processes.
   */
  async getExitCode(pid: number): Promise<number | null> {
    // For detached processes, we can't easily get the exit code
    // This would need to be enhanced with process tracking
    return null;
  }
}