'use strict'

const { kMaxLength } = require('buffer')
const {
  createInflate,
  constants: {
    DEFLATE,
    INFLATE,
    Z_DEFAULT_CHUNK,
    Z_DEFAULT_COMPRESSION,
    Z_DEFAULT_MEMLEVEL,
    Z_DEFAULT_STRATEGY,
    Z_DEFAULT_WINDOWBITS,
    Z_PARTIAL_FLUSH
  }
} = require('bare-node-zlib')

/**
 * Node's `zlib` exposes `createInflate()._handle.constructor` for the sync
 * binding. Bare's `bare-node-zlib` / `bare-zlib` often has no `_handle`, so
 * reading `.constructor` at module load throws. Resolve lazily; callers that
 * need zlib compression get a clear error if unavailable.
 */
let ZlibHandleCtor
function getZlibHandleCtor() {
  if (ZlibHandleCtor !== undefined) return ZlibHandleCtor
  try {
    const inf = createInflate()
    ZlibHandleCtor =
      inf &&
      inf._handle &&
      typeof inf._handle.constructor === 'function'
        ? inf._handle.constructor
        : null
  } catch {
    ZlibHandleCtor = null
  }
  return ZlibHandleCtor
}

function processCallback() {
  throw new Error('Should not get here')
}

function zlibOnError(message, errno, code) {
  const self = this._owner
  // There is no way to cleanly recover.
  // Continuing only obscures problems.

  const error = new Error(message)
  error.errno = errno
  error.code = code
  self._err = error
}

function _close(engine) {
  // Caller may invoke .close after a zlib error (which will null _handle).
  if (!engine._handle) return

  engine._handle.close()
  engine._handle = null
}

class Zlib {
  constructor(mode) {
    const windowBits = Z_DEFAULT_WINDOWBITS
    const level = Z_DEFAULT_COMPRESSION
    const memLevel = Z_DEFAULT_MEMLEVEL
    const strategy = Z_DEFAULT_STRATEGY
    const dictionary = undefined

    this._err = undefined
    this._writeState = new Uint32Array(2)
    this._chunkSize = Z_DEFAULT_CHUNK
    this._maxOutputLength = kMaxLength
    this._outBuffer = Buffer.allocUnsafe(this._chunkSize)
    this._outOffset = 0

    const Handle = getZlibHandleCtor()
    if (!Handle) {
      throw new Error(
        'bare-ssh2 zlib: native zlib _handle unavailable (use compression "none" only on Bare/Pear)'
      )
    }
    this._handle = new Handle(mode)
    this._handle._owner = this
    this._handle.onerror = zlibOnError
    this._handle.init(
      windowBits,
      level,
      memLevel,
      strategy,
      this._writeState,
      processCallback,
      dictionary
    )
  }

  writeSync(chunk, retChunks) {
    const handle = this._handle
    if (!handle) throw new Error('Invalid Zlib instance')

    let availInBefore = chunk.length
    let availOutBefore = this._chunkSize - this._outOffset
    let inOff = 0
    let availOutAfter
    let availInAfter

    let buffers
    let nread = 0
    const state = this._writeState
    let buffer = this._outBuffer
    let offset = this._outOffset
    const chunkSize = this._chunkSize

    while (true) {
      handle.writeSync(
        Z_PARTIAL_FLUSH,
        chunk, // in
        inOff, // in_off
        availInBefore, // in_len
        buffer, // out
        offset, // out_off
        availOutBefore
      ) // out_len
      if (this._err) throw this._err

      availOutAfter = state[0]
      availInAfter = state[1]

      const inDelta = availInBefore - availInAfter
      const have = availOutBefore - availOutAfter

      if (have > 0) {
        const out =
          offset === 0 && have === buffer.length ? buffer : buffer.slice(offset, offset + have)
        offset += have
        if (!buffers) buffers = out
        else if (buffers.push === undefined) buffers = [buffers, out]
        else buffers.push(out)
        nread += out.byteLength

        if (nread > this._maxOutputLength) {
          _close(this)
          throw new Error(`Output length exceeded maximum of ${this._maxOutputLength}`)
        }
      } else if (have !== 0) {
        throw new Error('have should not go down')
      }

      // Exhausted the output buffer, or used all the input create a new one.
      if (availOutAfter === 0 || offset >= chunkSize) {
        availOutBefore = chunkSize
        offset = 0
        buffer = Buffer.allocUnsafe(chunkSize)
      }

      if (availOutAfter === 0) {
        // Not actually done. Need to reprocess.
        // Also, update the availInBefore to the availInAfter value,
        // so that if we have to hit it a third (fourth, etc.) time,
        // it'll have the correct byte counts.
        inOff += inDelta
        availInBefore = availInAfter
      } else {
        break
      }
    }

    this._outBuffer = buffer
    this._outOffset = offset

    if (nread === 0) buffers = Buffer.alloc(0)

    if (retChunks) {
      buffers.totalLen = nread
      return buffers
    }

    if (buffers.push === undefined) return buffers

    const output = Buffer.allocUnsafe(nread)
    for (let i = 0, p = 0; i < buffers.length; ++i) {
      const buf = buffers[i]
      output.set(buf, p)
      p += buf.length
    }
    return output
  }
}

class ZlibPacketWriter {
  constructor(protocol) {
    this.allocStart = 0
    this.allocStartKEX = 0
    this._protocol = protocol
    this._zlib = new Zlib(DEFLATE)
  }

  cleanup() {
    if (this._zlib) _close(this._zlib)
  }

  alloc(payloadSize, force) {
    return Buffer.allocUnsafe(payloadSize)
  }

  finalize(payload, force) {
    if (this._protocol._kexinit === undefined || force) {
      const output = this._zlib.writeSync(payload, true)
      const packet = this._protocol._cipher.allocPacket(output.totalLen)
      if (output.push === undefined) {
        packet.set(output, 5)
      } else {
        for (let i = 0, p = 5; i < output.length; ++i) {
          const chunk = output[i]
          packet.set(chunk, p)
          p += chunk.length
        }
      }
      return packet
    }
    return payload
  }
}

class PacketWriter {
  constructor(protocol) {
    this.allocStart = 5
    this.allocStartKEX = 5
    this._protocol = protocol
  }

  cleanup() {}

  alloc(payloadSize, force) {
    if (this._protocol._kexinit === undefined || force)
      return this._protocol._cipher.allocPacket(payloadSize)
    return Buffer.allocUnsafe(payloadSize)
  }

  finalize(packet, force) {
    return packet
  }
}

class ZlibPacketReader {
  constructor() {
    this._zlib = new Zlib(INFLATE)
  }

  cleanup() {
    if (this._zlib) _close(this._zlib)
  }

  read(data) {
    return this._zlib.writeSync(data, false)
  }
}

class PacketReader {
  cleanup() {}

  read(data) {
    return data
  }
}

module.exports = {
  PacketReader,
  PacketWriter,
  ZlibPacketReader,
  ZlibPacketWriter
}