/**
 * Interactive container terminal over protomux-rpc.
 * TTY sessions stream raw PTY bytes (no demux). Supports multi-session via sessionId.
 */
import { PassThrough } from 'stream'
import { docker } from '../services/docker.js'
import { Pushes } from '../../shared/protocol.js'
import logger from '../utils/logger.js'

const SESSIONS_KEY = 'terminals'

function getSessions(session) {
  let map = session.state.get(SESSIONS_KEY)
  if (!map) {
    map = new Map()
    session.state.set(SESSIONS_KEY, map)
  }
  return map
}

function resolveSessionId(args) {
  return args.sessionId || args.terminalId || args.containerId || 'default'
}

/**
 * @param {Buffer|Uint8Array} chunk
 */
function toBase64(chunk) {
  return Buffer.isBuffer(chunk) ? chunk.toString('base64') : Buffer.from(chunk).toString('base64')
}

export function registerTerminalHandlers(session) {
  session.respond('startTerminal', async (args) => {
    const containerId = args.containerId
    if (!containerId) throw new Error('containerId required')

    const sessions = getSessions(session)
    const sessionId = resolveSessionId(args)

    if (sessions.has(sessionId)) {
      endOne(sessions, sessionId)
    }

    const useTty = args.tty !== false
    const shellCandidates = []
    if (Array.isArray(args.cmd) && args.cmd.length) {
      shellCandidates.push(args.cmd.map(String))
    } else if (typeof args.cmd === 'string' && args.cmd.trim()) {
      shellCandidates.push(args.cmd.trim().split(/\s+/))
    } else if (args.shell) {
      shellCandidates.push([String(args.shell)])
    } else {
      shellCandidates.push(['/bin/bash'], ['/bin/sh'], ['/bin/ash'])
    }

    const container = docker.getContainer(containerId)
    let exec = null
    let lastErr = null
    for (const Cmd of shellCandidates) {
      try {
        exec = await container.exec({
          Cmd,
          AttachStdin: true,
          AttachStdout: true,
          AttachStderr: true,
          Tty: useTty,
        })
        break
      } catch (err) {
        lastErr = err
      }
    }
    if (!exec) {
      throw lastErr || new Error('Failed to create exec session')
    }

    const stream = await exec.start({
      hijack: true,
      stdin: true,
      Tty: useTty,
    })

    const entry = {
      containerId,
      exec,
      stream,
      sessionId,
      tty: useTty,
    }
    sessions.set(sessionId, entry)
    session.state.set('terminal', entry)

    const pushOut = (chunk, isErr = false) => {
      const channel = isErr ? Pushes.terminalErrorOutput : Pushes.terminalOutput
      const type = isErr ? 'terminalErrorOutput' : 'terminalOutput'
      try {
        session.push(channel, {
          type,
          containerId,
          sessionId,
          data: toBase64(chunk),
          encoding: 'base64',
        })
      } catch (e) {
        logger.debug('terminal push failed', { error: e.message })
      }
    }

    if (useTty) {
      // Raw PTY — do NOT demux (would corrupt ANSI / binary)
      stream.on('data', (chunk) => pushOut(chunk, false))
    } else {
      const stdout = new PassThrough()
      const stderr = new PassThrough()
      container.modem.demuxStream(stream, stdout, stderr)
      stdout.on('data', (chunk) => pushOut(chunk, false))
      stderr.on('data', (chunk) => pushOut(chunk, true))
    }

    stream.on('end', () => {
      sessions.delete(sessionId)
      if (session.state.get('terminal') === entry) session.state.delete('terminal')
    })
    stream.on('error', (err) => {
      logger.error('Terminal stream error', { containerId, error: err.message })
      sessions.delete(sessionId)
    })

    const cols = Number(args.cols)
    const rows = Number(args.rows)
    if (cols > 0 && rows > 0) {
      try {
        await exec.resize({ h: rows, w: cols })
      } catch {
        // ignore
      }
    }

    logger.info('Terminal session started', {
      containerId,
      sessionId,
      tty: useTty,
      peer: session.id.slice(0, 12),
    })
    return {
      success: true,
      message: `Terminal started for ${containerId}`,
      sessionId,
      containerId,
      tty: useTty,
    }
  })

  // Hot path: events (id=0) — keep handler sync/cheap; no audit/metrics in session layer
  session.respond(
    'terminalInput',
    (args) => {
      const sessions = getSessions(session)
      const sessionId = resolveSessionId(args)
      const entry = sessions.get(sessionId) || session.state.get('terminal')
      if (!entry) return null
      if (args.containerId && args.containerId !== entry.containerId) return null

      let inputData
      if (args.encoding === 'base64') {
        inputData = Buffer.from(args.data || '', 'base64')
      } else {
        // Default utf8 string in JSON (optimal for keystrokes)
        inputData = Buffer.from(args.data || '', 'utf8')
      }
      if (inputData.length && entry.stream && !entry.stream.writableEnded) {
        entry.stream.write(inputData)
      }
      return null
    },
    { hot: true }
  )

  session.respond(
    'terminalResize',
    async (args) => {
      const sessions = getSessions(session)
      const sessionId = resolveSessionId(args)
      const entry = sessions.get(sessionId) || session.state.get('terminal')
      if (!entry) return null
      if (args.containerId && args.containerId !== entry.containerId) return null
      const cols = Number(args.cols)
      const rows = Number(args.rows)
      if (cols > 1 && rows > 0) {
        try {
          await entry.exec.resize({ h: rows, w: cols })
        } catch {
          // ignore transient resize errors
        }
      }
      return null
    },
    { hot: true }
  )

  session.respond('killTerminal', async (args) => {
    const sessions = getSessions(session)
    const sessionId = args.sessionId || args.terminalId
    if (sessionId && sessions.has(sessionId)) {
      const entry = sessions.get(sessionId)
      endOne(sessions, sessionId)
      return {
        success: true,
        message: `Terminal session ${sessionId} killed`,
        sessionId,
        containerId: entry.containerId,
      }
    }
    if (args.containerId) {
      let killed = 0
      for (const [id, entry] of [...sessions.entries()]) {
        if (entry.containerId === args.containerId) {
          endOne(sessions, id)
          killed += 1
        }
      }
      if (killed) {
        return { success: true, message: `Killed ${killed} terminal(s) for ${args.containerId}` }
      }
    }
    const entry = session.state.get('terminal')
    if (entry) {
      endOne(sessions, entry.sessionId || 'default')
      session.state.delete('terminal')
      return { success: true, message: 'Terminal killed' }
    }
    return { success: false, message: 'No terminal session found' }
  })
}

function endOne(sessions, sessionId) {
  const entry = sessions.get(sessionId)
  if (!entry) return
  try {
    entry.stream.end()
  } catch {
    // ignore
  }
  try {
    entry.stream.destroy?.()
  } catch {
    // ignore
  }
  sessions.delete(sessionId)
}

export function endTerminal(session) {
  const sessions = session.state.get(SESSIONS_KEY)
  if (sessions) {
    for (const id of [...sessions.keys()]) endOne(sessions, id)
  }
  session.state.delete('terminal')
  session.state.delete(SESSIONS_KEY)
}

export function cleanupTerminalOnClose(session) {
  endTerminal(session)
}