$collection = new \Mleczek\Collections\Collection([
    ['id' => 3, 'firstName' => 'Debra', 'lastName' => 'Barnett'],
    ['id' => 8, 'firstName' => 'Ronnie', 'lastName' => 'Coleman'],
    ['id' => 2, 'firstName' => 'Gabriel', 'lastName' => 'Adams'],
]);

// ...and perform some operations:
$names = $collection
    ->whereIn(fn($x) => $x['id'], [3, 2])
    ->map(fn($x) => $x['firstName'] .' '. $x['lastName'])
    ->join(', ');

// $names is equal "Debra Barnett, Gabriel Adams"

$sum = collection([1, 2, 5])
    ->map(fn($x) => $x * 2)
    ->sum();

// $sum is equal 16 (2+4+10)

$collection = collection([2, 3])->addFirst(1);

$collection = collection([2, 3])->addLast(4);

$avg = collection([1, 2, 6])->avg();

$items = [
    ['value' => 3],
    ['value' => 7],
];

$avg = collection($items)
    ->avg(fn($item, $key) => $item['value']);

$collection = collection([1, 2, 3])->chunk(2);

$count = collection([1, 2])->count();

collection(['a' => 1, 'b' => 2])
    ->each(fn($item, $key) => printf("$key:$item"));

$key = collection(['a' => 1, 'b' => 2])->firstKey();

$item = collection(['a' => 1, 'b' => 2])->first();

$collection = collection([[1, 2], [3]])->flatten();

$items = [
    ['brand' => 'Jeep', 'model' => 'Cherokee Latitude'],
    ['brand' => 'Nissan', 'model' => 'Sentra SV'],
    ['brand' => 'Nissan', 'model' => 'Murano Platinum'],
];

$collection = collection($items)
    ->groupBy(fn($item, $key) => $item['brand']);

$test = collection([2, 7, 3])
    ->has(fn($item, $key) => $item === 7);

$test = collection(['a' => 1, 4])->isAssociative();

$test = collection([])->isEmpty();

$test = collection(['a' => 1, 4])->isIndexed();

$test = collection([8, 2])->isNotEmpty();

$string = collection(['Nissan', 'Jeep', 'Ford'])->join(', ');

$items = [
    ['id' => 5, 'username' => 'lorraine'],
    ['id' => 1, 'username' => 'gabriel.hill'],
    ['id' => 4, 'username' => 'steward'],
];

$collection = collection($items)
    ->keyBy(fn($item, $key) => $item['id']);

$array = collection(['a' => 1, 'b' => 3])->keys();

$key = collection(['a' => 1, 'b' => 2])->lastKey();

$item = collection(['a' => 1, 'b' => 2])->last();

$collection = collection([1, 4])
    ->map(fn($item, $key) => $item * 2);

$max = collection([1, 4, 7])->max();

$items = [
    ['value' => 3],
    ['value' => 7],
];

$avg = collection($items)
    ->max(fn($item, $key) => $item['value']);

$collection = collection([1, 2])->merge([3, 4]);

$first = collection([1, 2]);
$second = collection(['a' => 1, 'b' => 2]);

$collection = $first->merge($second);

$max = collection([1, 4, 7])->min();

$items = [
    ['value' => 3],
    ['value' => 7],
];

$avg = collection($items)
    ->min(fn($item, $key) => $item['value']);

$item = collection(['a' => 1, 'b' => 2])->randomKey();

$item = collection([1, 8, 4])->random();

$initialState = 2;
$result = collection([1, 8, 4])
    ->reduce(fn($item, $state) => $state + $item, $initialState);

$collection = collection([1, 8, 4])->removeFirst();
$collection = collection([1, 8, 4])->removeFirst(2);

$collection = collection([1, 8, 4])->removeLast();
$collection = collection([1, 8, 4])->removeLast(2);

$collection = collection([1, 8, 4])->reverse();

$collection = collection([1, 8, 4])->skip();
$collection = collection([1, 8, 4])->skip(2);

$collection = collection([1, 8, 4])->sortDesc();

$items = [
    ['value' => 3],
    ['value' => 7],
];

$collection = collection($items)
    ->sortDesc(fn($item) => $item['value']);

$collection = collection([1, 8, 4])->sort();

$items = [
    ['value' => 3],
    ['value' => 7],
];

$collection = collection($items)
    ->sort(fn($item) => $item['value']);

$sum = collection([1, 2, 6])->sum();

$items = [
    ['value' => 3],
    ['value' => 7],
];

$sum = collection($items)
    ->sum(fn($item, $key) => $item['value']);

$collection = collection([1, 8, 4])->take();
$collection = collection([1, 8, 4])->take(2);

$array = collection([6, 3, 1])->toArray();

$collection = collection([6, 1, 3, 1])->unique();

$items = [
    ['brand' => 'Jeep', 'model' => 'Cherokee Latitude'],
    ['brand' => 'Nissan', 'model' => 'Sentra SV'],
    ['brand' => 'Nissan', 'model' => 'Murano Platinum'],
];

$collection = collection([$items])
    ->unique(fn($item, $key) => $item['brand']);

$values = collection(['a' => 1, 'b' => 2])->values();

$collection = collection([8, 4, 2])
    ->whereIn(fn($item, $key) => $item, [4, 7, 2]);

$collection = collection([8, 4, 2])
    ->where(fn($item, $key) => $item > 3);