<?php

namespace TMciver\Functional;

use TMciver\Functional\ObjectTypeclass\ObjectTraversable;

// Just a wrapper around the native PHP array to allow for cool FP goodness.

class AssociativeArray {

use ObjectTraversable;

protected $array;

public function __construct($array) {

$this->array = is_null($array) ? [] : $array;

}

// TODO: This is broken. It returns an instance of the given Monad wrapping

// a PHP _native_ array; not an AssociativeArray.

public function traverse(callable $f, $monad) {

// Initial value for the fold: an empty array wrapped in a default

// context.

$init = $monad->pure([]);

// Define the folding function.

$foldingFn = function ($acc, $curr) use ($f, $monad) {

// Call $f on the current value of the array, $curr. The return

// value should be a monadic value.

try {

$returnedMonad = $f($curr);

// If the result is null, we fail.

if (is_null($returnedMonad)) {

$returnedMonad = $monad->fail('The callable passed to `AssociativeArray::traverse` returned null.');

}

} catch (\Exception $e) {

$returnedMonad = $monad->fail('The callable passed to `AssociativeArray::traverse` threw an exception: ' . $e->getMessage());

}

// Put the value wrapped by the above monadic value in the array

// held by the accumulator, $acc, to get the new accumulator.

$newAcc = $returnedMonad->flatMap(function ($newVal) use ($acc) {

return $acc->map(function ($arr) use ($newVal) {

$arr[] = $newVal;

return $arr;

});

});

return $newAcc;

};

// Do the fold.

$result = array_reduce($this->array, $foldingFn, $init);

return $result;

}

}