// m [pubKeys ...] n OP_CHECKMULTISIG

var bscript = require('../../script')
var types = require('../../types')
var typeforce = require('typeforce')
var OPS = require('../../opcodes.json')
var OP_INT_BASE = OPS.OP_RESERVED // OP_1 - 1

function check (script, allowIncomplete) {
  var chunks = bscript.decompile(script)

  if (chunks.length < 4) return false
  if (chunks[chunks.length - 1] !== OPS.OP_CHECKMULTISIG) return false
  if (!types.Number(chunks[0])) return false
  if (!types.Number(chunks[chunks.length - 2])) return false
  var m = chunks[0] - OP_INT_BASE
  var n = chunks[chunks.length - 2] - OP_INT_BASE

  if (m <= 0) return false
  if (n > 16) return false
  if (m > n) return false
  if (n !== chunks.length - 3) return false
  if (allowIncomplete) return true

  var keys = chunks.slice(1, -2)
  return keys.every(bscript.isCanonicalPubKey)
}

function encode (m, pubKeys) {
  typeforce({
    m: types.Number,
    pubKeys: [bscript.isCanonicalPubKey]
  }, {
    m: m,
    pubKeys: pubKeys
  })

  var n = pubKeys.length
  if (n < m) throw new TypeError('Not enough pubKeys provided')

  return bscript.compile([].concat(
    OP_INT_BASE + m,
    pubKeys,
    OP_INT_BASE + n,
    OPS.OP_CHECKMULTISIG
  ))
}

function decode (buffer, allowIncomplete) {
  var chunks = bscript.decompile(buffer)
  typeforce(check, chunks, allowIncomplete)

  return {
    m: chunks[0] - OP_INT_BASE,
    pubKeys: chunks.slice(1, -2)
  }
}

module.exports = {
  check: check,
  decode: decode,
  encode: encode
}