'use strict'

module.exports = convert

function convert(test) {
  if (test == null) {
    return ok
  }

  if (typeof test === 'string') {
    return typeFactory(test)
  }

  if (typeof test === 'object') {
    return 'length' in test ? anyFactory(test) : allFactory(test)
  }

  if (typeof test === 'function') {
    return test
  }

  throw new Error('Expected function, string, or object as test')
}

// Utility assert each property in `test` is represented in `node`, and each
// values are strictly equal.
function allFactory(test) {
  return all

  function all(node) {
    var key

    for (key in test) {
      if (node[key] !== test[key]) return false
    }

    return true
  }
}

function anyFactory(tests) {
  var checks = []
  var index = -1

  while (++index < tests.length) {
    checks[index] = convert(tests[index])
  }

  return any

  function any() {
    var index = -1

    while (++index < checks.length) {
      if (checks[index].apply(this, arguments)) {
        return true
      }
    }

    return false
  }
}

// Utility to convert a string into a function which checks a given node’s type
// for said string.
function typeFactory(test) {
  return type

  function type(node) {
    return Boolean(node && node.type === test)
  }
}

// Utility to return true.
function ok() {
  return true
}