import { spawn, type ChildProcess } from 'node:child_process'
import { existsSync } from 'node:fs'
import { join } from 'node:path'
import { homedir } from 'node:os'
import type { SynthesisConfig } from './config.js'
import type { SessionMapping } from './session-mapping.js'

export interface ProcessHandle {
  pid: number
  openclawSessionKey: string
  claudeSessionUuid: string
  workspace: string
  proc: ChildProcess
  startedAt: number
  lastActiveAt: number
  /** Resolves once ClaudePlugin sends `hello` over the bridge WS. */
  ready: Promise<void>
  markReady: () => void
}

export interface ProcessManagerDeps {
  config: SynthesisConfig
  mapping: SessionMapping
  logger?: { info: (...a: unknown[]) => void; warn: (...a: unknown[]) => void }
}

/**
 * Owns the pool of long-lived `claude` subprocesses. One per OpenClaw
 * session-key (`agent_id::chat_id` per contractor-agent's convention).
 * Lazily spawned on first dispatch and reaped after `idleKillMs` of idle.
 *
 * Spawn shape:
 *   claude --channels server:<channelName>
 *          --dangerously-load-development-channels server:<channelName>
 *          --resume <claude_session_uuid>
 *          --permission-mode <permissionMode>
 *          --dangerously-skip-permissions   ← only when permissionMode=bypassPermissions
 *                                              AND we're allowed to (non-root or sandbox)
 *   env: SYNTHESIS_WS_URL, SYNTHESIS_OPENCLAW_SESSION, SYNTHESIS_CLAUDE_SESSION
 *
 * The spawned `--dangerously-load-development-channels` will trigger an
 * interactive confirmation dialog by default. We handle this by piping a
 * "1\n" to stdin shortly after spawn (the first option is the dev-mode
 * confirmation). The Claude process's first turn comes from the channel
 * notification, not from stdin.
 */
export class ProcessManager {
  private byKey = new Map<string, ProcessHandle>()
  private idleSweeper: ReturnType<typeof setInterval> | null = null
  private shuttingDown = false
  private log: NonNullable<ProcessManagerDeps['logger']>

  constructor(private deps: ProcessManagerDeps) {
    this.log = deps.logger ?? {
      info: (...a) => process.stderr.write(`[synthesis-pm] ${a.join(' ')}\n`),
      warn: (...a) => process.stderr.write(`[synthesis-pm] WARN ${a.join(' ')}\n`),
    }
    this.idleSweeper = setInterval(() => this.sweepIdle(), 60_000)
  }

  /** Spawn-if-needed and await the ClaudePlugin handshake. */
  async ensure(openclawSessionKey: string, workspace: string): Promise<ProcessHandle> {
    const existing = this.byKey.get(openclawSessionKey)
    if (existing && !existing.proc.killed && existing.proc.exitCode === null) {
      existing.lastActiveAt = Date.now()
      return existing
    }

    if (this.byKey.size >= this.deps.config.maxProcesses) this.evictOldestIdle()

    const rec = this.deps.mapping.ensure(openclawSessionKey)
    const handle = this.spawn(openclawSessionKey, rec.claudeSessionUuid, workspace)
    this.byKey.set(openclawSessionKey, handle)
    await Promise.race([
      handle.ready,
      new Promise<never>((_, rej) =>
        setTimeout(() => rej(new Error('claude spawn ready timeout (15s)')), 15_000),
      ),
    ])
    this.deps.mapping.touch(openclawSessionKey)
    return handle
  }

  /** Bridge server calls this when it sees a `hello` frame for this session. */
  markReady(openclawSessionKey: string): void {
    const h = this.byKey.get(openclawSessionKey)
    if (h) h.markReady()
  }

  touch(openclawSessionKey: string): void {
    const h = this.byKey.get(openclawSessionKey)
    if (h) h.lastActiveAt = Date.now()
  }

  private spawn(openclawSessionKey: string, claudeSessionUuid: string, workspace: string): ProcessHandle {
    const { config } = this.deps
    const wsUrl = `ws://127.0.0.1:${config.channelWsPort}/bridge`
    const channelTag = `server:${config.channelName}`
    // First spawn for this session-id uses --session-id (fresh); subsequent
    // spawns (after idle reap / OOM / crash) use --resume to pick up the
    // saved transcript at ~/.claude/projects/<workspace-slug>/<uuid>.jsonl.
    const hasExistingSession = claudeSessionFileExists(workspace, claudeSessionUuid)
    const sessionFlag = hasExistingSession
      ? ['--resume', claudeSessionUuid]
      : ['--session-id', claudeSessionUuid]
    // Pass channel ONLY via --dangerously-load-development-channels.
    // Passing the same channel through both --channels and
    // --dangerously-load-development-channels makes Claude Code list it
    // twice ("Listening for channel messages from: X, X") and the second
    // entry never inherits the dev-mode flag — the status panel ends up
    // saying "server: entries need --dangerously-load-development-channels"
    // even after the dev-mode confirmation. The dev flag implies the
    // channel is loaded, so --channels is redundant here.
    const debugFile = `/tmp/synthesis-claude-${openclawSessionKey.replace(/[^a-z0-9]/gi, '_')}.debug.log`
    const args = [
      '--dangerously-load-development-channels', channelTag,
      ...sessionFlag,
      '--permission-mode', config.permissionMode,
      '--debug-file', debugFile,
    ]

    this.log.info(`spawning claude session=${openclawSessionKey} claude_uuid=${claudeSessionUuid} workspace=${workspace}`)

    // Wrap claude in `script(1)` to give it a PTY. Without a TTY, Claude
    // Code's interactive prompts (workspace-trust, dev-channels confirm)
    // block forever waiting for keystrokes that never arrive. `script -q -c`
    // forks a PTY, runs the command inside it, and discards the transcript
    // to /dev/null. Stdin we write to is the PTY master.
    const claudeCmd = ['claude', ...args].map(a => /[\s"]/.test(a) ? `"${a.replace(/"/g, '\\"')}"` : a).join(' ')
    const ptyLog = `/tmp/synthesis-claude-${openclawSessionKey.replace(/[^a-z0-9]/gi, '_')}.pty`
    const proc = spawn('script', ['-q', '-c', claudeCmd, ptyLog], {
      cwd: workspace,
      env: {
        ...process.env,
        SYNTHESIS_WS_URL: wsUrl,
        SYNTHESIS_OPENCLAW_SESSION: openclawSessionKey,
        SYNTHESIS_CLAUDE_SESSION: claudeSessionUuid,
        TERM: 'xterm-256color',
      },
      stdio: ['pipe', 'pipe', 'pipe'],
      detached: false,
    })

    // Pre-feed Enter keystrokes through the PTY to dismiss any startup
    // prompts (dev-channels confirm; trusted-workspace if anything slipped
    // through). Cheap to over-send — Claude eats unexpected keystrokes.
    for (const delay of [800, 1500, 2500, 4000, 6000]) {
      setTimeout(() => {
        try { proc.stdin?.write('\r') } catch { /* ignore */ }
      }, delay)
    }

    let resolveReady!: () => void
    const ready = new Promise<void>(r => { resolveReady = r })

    const handle: ProcessHandle = {
      pid: proc.pid ?? -1,
      openclawSessionKey,
      claudeSessionUuid,
      workspace,
      proc,
      startedAt: Date.now(),
      lastActiveAt: Date.now(),
      ready,
      markReady: () => resolveReady(),
    }

    proc.on('exit', code => {
      this.byKey.delete(openclawSessionKey)
      this.log.info(`claude exit session=${openclawSessionKey} pid=${handle.pid} code=${code}`)
    })

    proc.stderr?.on('data', chunk => {
      process.stderr.write(`[claude:${handle.pid}] ${chunk}`)
    })

    return handle
  }

  private sweepIdle(): void {
    if (this.shuttingDown) return
    const cutoff = Date.now() - this.deps.config.idleKillMs
    for (const h of this.byKey.values()) {
      if (h.lastActiveAt < cutoff) {
        this.log.info(`idle-killing session=${h.openclawSessionKey} pid=${h.pid}`)
        h.proc.kill('SIGTERM')
      }
    }
  }

  private evictOldestIdle(): void {
    let oldest: ProcessHandle | null = null
    for (const h of this.byKey.values()) {
      if (!oldest || h.lastActiveAt < oldest.lastActiveAt) oldest = h
    }
    if (oldest) {
      this.log.info(`evicting session=${oldest.openclawSessionKey} (max processes reached)`)
      oldest.proc.kill('SIGTERM')
    }
  }

  list(): ProcessHandle[] {
    return [...this.byKey.values()]
  }

  /** Async helper exposed for tests / admin tools. */
  static sessionFileExists(workspace: string, uuid: string): boolean {
    return claudeSessionFileExists(workspace, uuid)
  }

  async shutdown(): Promise<void> {
    this.shuttingDown = true
    if (this.idleSweeper) clearInterval(this.idleSweeper)
    for (const h of this.byKey.values()) {
      try { h.proc.kill('SIGTERM') } catch { /* ignore */ }
    }
    this.byKey.clear()
  }
}

/**
 * Claude Code persists session transcripts at:
 *   ~/.claude/projects/<workspace-slug>/<session-uuid>.jsonl
 * where workspace-slug is the absolute workspace path with `/` → `-`.
 */
function claudeSessionFileExists(workspace: string, uuid: string): boolean {
  try {
    const slug = workspace.replace(/\//g, '-')
    const path = join(homedir(), '.claude', 'projects', slug, `${uuid}.jsonl`)
    return existsSync(path)
  } catch {
    return false
  }
}