const std = @import("std");
const testing = std.testing;

const linked_list = @import("linked_list.zig");
const List = linked_list.LinkedList(usize);

test "pop gets element from the list" {
    var list = List{};
    var a = List.Node{ .data = 7 };
    list.push(&a);
    try testing.expectEqual(@as(usize, 7), list.pop().?.data);
}

test "push/pop respectively add/remove at the end of the list" {
    var list = List{};
    var a = List.Node{ .data = 11 };
    var b = List.Node{ .data = 13 };
    list.push(&a);
    list.push(&b);
    try testing.expectEqual(@as(usize, 13), list.pop().?.data);
    try testing.expectEqual(@as(usize, 11), list.pop().?.data);
}

test "shift gets an element from the list" {
    var list = List{};
    var a = List.Node{ .data = 17 };
    list.push(&a);
    try testing.expectEqual(@as(usize, 17), list.shift().?.data);
}

test "shift gets first element from the list" {
    var list = List{};
    var a = List.Node{ .data = 23 };
    var b = List.Node{ .data = 5 };
    list.push(&a);
    list.push(&b);
    try testing.expectEqual(@as(usize, 23), list.shift().?.data);
    try testing.expectEqual(@as(usize, 5), list.shift().?.data);
}

test "unshift adds element at start of the list" {
    var list = List{};
    var a = List.Node{ .data = 23 };
    var b = List.Node{ .data = 5 };
    list.unshift(&a);
    list.unshift(&b);
    try testing.expectEqual(@as(usize, 5), list.shift().?.data);
    try testing.expectEqual(@as(usize, 23), list.shift().?.data);
}

test "pop, push, shift, and unshift can be used in any order" {
    var list = List{};
    var a = List.Node{ .data = 1 };
    var b = List.Node{ .data = 2 };
    var c = List.Node{ .data = 3 };
    var d = List.Node{ .data = 4 };
    var e = List.Node{ .data = 5 };
    list.push(&a);
    list.push(&b);
    try testing.expectEqual(@as(usize, 2), list.pop().?.data);
    list.push(&c);
    try testing.expectEqual(@as(usize, 1), list.shift().?.data);
    list.unshift(&d);
    list.push(&e);
    try testing.expectEqual(@as(usize, 4), list.shift().?.data);
    try testing.expectEqual(@as(usize, 5), list.pop().?.data);
    try testing.expectEqual(@as(usize, 3), list.shift().?.data);
}

test "count an empty list" {
    const list = List{};
    try testing.expectEqual(@as(usize, 0), list.len);
}

test "count a list with items" {
    var list = List{};
    var a = List.Node{ .data = 37 };
    var b = List.Node{ .data = 1 };
    list.push(&a);
    list.push(&b);
    try testing.expectEqual(@as(usize, 2), list.len);
}

test "count is correct after mutation" {
    var list = List{};
    var a = List.Node{ .data = 31 };
    var b = List.Node{ .data = 43 };
    list.push(&a);
    try testing.expectEqual(@as(usize, 1), list.len);
    list.unshift(&b);
    try testing.expectEqual(@as(usize, 2), list.len);
    _ = list.shift();
    try testing.expectEqual(@as(usize, 1), list.len);
    _ = list.pop();
    try testing.expectEqual(@as(usize, 0), list.len);
}

test "popping to empty doesn't break the list" {
    var list = List{};
    var a = List.Node{ .data = 41 };
    var b = List.Node{ .data = 59 };
    var c = List.Node{ .data = 47 };
    list.push(&a);
    list.push(&b);
    _ = list.pop();
    _ = list.pop();
    list.push(&c);
    try testing.expectEqual(@as(usize, 1), list.len);
    try testing.expectEqual(@as(usize, 47), list.pop().?.data);
}

test "shifting to empty doesn't break the list" {
    var list = List{};
    var a = List.Node{ .data = 41 };
    var b = List.Node{ .data = 59 };
    var c = List.Node{ .data = 47 };
    list.push(&a);
    list.push(&b);
    _ = list.shift();
    _ = list.shift();
    list.push(&c);
    try testing.expectEqual(@as(usize, 1), list.len);
    try testing.expectEqual(@as(usize, 47), list.shift().?.data);
}

test "deletes the only element" {
    var list = List{};
    var a = List.Node{ .data = 61 };
    list.push(&a);
    list.delete(&a);
    try testing.expectEqual(@as(usize, 0), list.len);
}

test "deletes the element with the specified value from the list" {
    var list = List{};
    var a = List.Node{ .data = 71 };
    var b = List.Node{ .data = 83 };
    var c = List.Node{ .data = 79 };
    list.push(&a);
    list.push(&b);
    list.push(&c);
    list.delete(&b);
    try testing.expectEqual(@as(usize, 2), list.len);
    try testing.expectEqual(@as(usize, 79), list.pop().?.data);
    try testing.expectEqual(@as(usize, 71), list.shift().?.data);
}

test "deletes the element with the specified value from the list, re-assigns tail" {
    var list = List{};
    var a = List.Node{ .data = 71 };
    var b = List.Node{ .data = 83 };
    var c = List.Node{ .data = 79 };
    list.push(&a);
    list.push(&b);
    list.push(&c);
    list.delete(&b);
    try testing.expectEqual(@as(usize, 2), list.len);
    try testing.expectEqual(@as(usize, 79), list.pop().?.data);
    try testing.expectEqual(@as(usize, 71), list.pop().?.data);
}

test "deletes the element with the specified value from the list, re-assigns head" {
    var list = List{};
    var a = List.Node{ .data = 71 };
    var b = List.Node{ .data = 83 };
    var c = List.Node{ .data = 79 };
    list.push(&a);
    list.push(&b);
    list.push(&c);
    list.delete(&b);
    try testing.expectEqual(@as(usize, 2), list.len);
    try testing.expectEqual(@as(usize, 71), list.shift().?.data);
    try testing.expectEqual(@as(usize, 79), list.shift().?.data);
}

test "deletes the first of two elements" {
    var list = List{};
    var a = List.Node{ .data = 97 };
    var b = List.Node{ .data = 101 };
    list.push(&a);
    list.push(&b);
    list.delete(&a);
    try testing.expectEqual(@as(usize, 1), list.len);
    try testing.expectEqual(@as(usize, 101), list.pop().?.data);
}

test "deletes the second of two elements" {
    var list = List{};
    var a = List.Node{ .data = 97 };
    var b = List.Node{ .data = 101 };
    list.push(&a);
    list.push(&b);
    list.delete(&b);
    try testing.expectEqual(@as(usize, 1), list.len);
    try testing.expectEqual(@as(usize, 97), list.pop().?.data);
}

test "delete does not modify the list if the element is not found" {
    var list = List{};
    var a = List.Node{ .data = 89 };
    var b = List.Node{ .data = 103 };
    list.push(&a);
    list.delete(&b);
    try testing.expectEqual(@as(usize, 1), list.len);
}

test "deletes only the first occurrence" {
    var list = List{};
    var a = List.Node{ .data = 73 };
    var b = List.Node{ .data = 9 };
    var c = List.Node{ .data = 9 };
    var d = List.Node{ .data = 107 };
    list.push(&a);
    list.push(&b);
    list.push(&c);
    list.push(&d);
    list.delete(&b);
    try testing.expectEqual(@as(usize, 3), list.len);
    try testing.expectEqual(@as(usize, 107), list.pop().?.data);
    try testing.expectEqual(@as(usize, 9), list.pop().?.data);
    try testing.expectEqual(@as(usize, 73), list.pop().?.data);
}