/* array.cm - array creation and manipulation utilities */

var _isArray = Array.isArray
var _slice = Array.prototype.slice
var _push = Array.prototype.push
var _sort = Array.prototype.sort
var _keys = Object.keys
var _from = Array.from

function array(arg, arg2, arg3, arg4) {
  // array(number) - create array of size with nulls
  // array(number, initial_value) - create array with initial values
  if (typeof arg == 'number') {
    if (arg < 0) return null
    var len = number.floor(arg)
    var result = []
    
    if (arg2 == null) {
      result.length = 100
    } else if (typeof arg2 == 'function') {
      var arity = arg2.length
      for (var i = 0; i < len; i++) {
        result[i] = arity >= 1 ? arg2(i) : arg2()
      }
    } else {
      for (var i = 0; i < len; i++) result[i] = arg2
    }
    
    return result
  }
  
  // array(array) - copy
  // array(array, function, reverse, exit) - map
  // array(array, another_array) - concat
  // array(array, from, to) - slice
  if (_isArray(arg)) {
    if (arg2 == null) {
      // Copy
      return _slice.call(arg)
    }
    
    if (typeof arg2 == 'function') {
      // Map
      var fn = arg2
      var reverse = arg3 == true
      var exit = arg4
      var result = []
      
      if (reverse) {
        for (var i = arg.length - 1; i >= 0; i--) {
          var val = fn(arg[i], i)
          if (exit != null && val == exit) break
          result[i] = val
        }
      } else {
        for (var i = 0; i < arg.length; i++) {
          var val = fn(arg[i], i)
          if (exit != null && val == exit) break
          _push.call(result, val)
        }
      }
      
      return result
    }
    
    if (_isArray(arg2)) {
      // Concat
      var result = _slice.call(arg)
      for (var i = 0; i < arg2.length; i++) {
        _push.call(result, arg2[i])
      }
      return result
    }
    
    if (typeof arg2 == 'number') {
      // Slice
      var from = arg2
      var to = arg3
      var len = arg.length
      
      if (from < 0) from += len
      if (to == null) to = len
      if (to < 0) to += len
      
      if (from < 0 || from > to || to > len) return null
      
      return _slice.call(arg, from, to)
    }
    
    return null
  }
  
  // array(object) - keys
  if (typeof arg == 'object' && arg != null && !_isArray(arg)) {
    if (arg instanceof Set) {
      return _from(arg)
    }
    return _keys(arg)
  }
  
  // array(text) - split into grapheme clusters
  // array(text, separator) - split by separator
  // array(text, length) - dice into chunks
  if (typeof arg == 'string') {
    if (arg2 == null) {
      // Split into grapheme clusters (simplified: split into characters)
      var result = []
      for (var i = 0; i < arg.length; i++) {
        _push.call(result, arg[i])
      }
      return result
    }
    
    if (typeof arg2 == 'string') {
      // Split by separator
      return arg.split(arg2)
    }
    
    if (typeof arg2 == 'number') {
      // Dice into chunks
      var len = number.floor(arg2)
      if (len <= 0) return null
      var result = []
      for (var i = 0; i < arg.length; i += len) {
        _push.call(result, arg.substring(i, i + len))
      }
      return result
    }
    
    return null
  }
  
  return null
}

array.reduce = function(arr, fn, initial, reverse) {
  if (!_isArray(arr)) return null
  if (typeof fn != 'function') return null
  
  var len = arr.length
  
  if (initial == null) {
    if (len == 0) return null
    if (len == 1) return arr[0]
    
    if (reverse == true) {
      var acc = arr[len - 1]
      for (var i = len - 2; i >= 0; i--) {
        acc = fn(acc, arr[i])
      }
      return acc
    } else {
      var acc = arr[0]
      for (var i = 1; i < len; i++) {
        acc = fn(acc, arr[i])
      }
      return acc
    }
  } else {
    if (len == 0) return initial
    
    if (reverse == true) {
      var acc = initial
      for (var i = len - 1; i >= 0; i--) {
        acc = fn(acc, arr[i])
      }
      return acc
    } else {
      var acc = initial
      for (var i = 0; i < len; i++) {
        acc = fn(acc, arr[i])
      }
      return acc
    }
  }
}

array.for = function(arr, fn, reverse, exit) {
  if (!_isArray(arr)) return null
  if (arr.length == 0) return null
  if (typeof fn != 'function') return null
  
  if (reverse == true) {
    for (var i = arr.length - 1; i >= 0; i--) {
      var result = fn(arr[i], i)
      if (exit != null && result == exit) return exit
    }
  } else {
    for (var i = 0; i < arr.length; i++) {
      var result = fn(arr[i], i)
      if (exit != null && result == exit) return exit
    }
  }
  
  return null
}

array.find = function(arr, fn, reverse, from) {
  if (!_isArray(arr)) return null
  
  var len = arr.length
  
  if (typeof fn != 'function') {
    // Compare exactly
    var target = fn
    if (reverse == true) {
      var start = from != null ? from : len - 1
      for (var i = start; i >= 0; i--) {
        if (arr[i] == target) return i
      }
    } else {
      var start = from != null ? from : 0
      for (var i = start; i < len; i++) {
        if (arr[i] == target) return i
      }
    }
    return null
  }
  
  if (reverse == true) {
    var start = from != null ? from : len - 1
    for (var i = start; i >= 0; i--) {
      if (fn(arr[i], i) == true) return i
    }
  } else {
    var start = from != null ? from : 0
    for (var i = start; i < len; i++) {
      if (fn(arr[i], i) == true) return i
    }
  }
  
  return null
}

array.filter = function(arr, fn) {
  if (!_isArray(arr)) return null
  if (typeof fn != 'function') return null
  
  var result = []
  
  for (var i = 0; i < arr.length; i++) {
    var val = fn(arr[i], i)
    if (val == true) {
      _push.call(result, arr[i])
    } else if (val != false) {
      return null
    }
  }
  
  return result
}

array.sort = function(arr, select) {
  if (!_isArray(arr)) return null
  
  var result = _slice.call(arr)
  var keys = []
  
  // Extract keys
  for (var i = 0; i < result.length; i++) {
    var key
    if (select == null) {
      key = result[i]
    } else if (typeof select == 'string' || typeof select == 'number') {
      key = result[i][select]
    } else if (_isArray(select)) {
      key = select[i]
    } else {
      return null
    }
    
    if (typeof key != 'number' && typeof key != 'string') return null
    keys[i] = key
  }
  
  // Check all keys are same type
  if (keys.length > 0) {
    var keyType = typeof keys[0]
    for (var i = 1; i < keys.length; i++) {
      if (typeof keys[i] != keyType) return null
    }
  }
  
  // Create index array and sort
  var indices = []
  for (var i = 0; i < result.length; i++) indices[i] = i
  
  // Stable sort using indices
  _sort.call(indices, function(a, b) {
    if (keys[a] < keys[b]) return -1
    if (keys[a] > keys[b]) return 1
    return a - b // stable
  })
  
  var sorted = []
  for (var i = 0; i < indices.length; i++) {
    sorted[i] = result[indices[i]]
  }
  
  return sorted
}

return array