<?php

namespace Tests\Unit\Schedule;

use App\Schedule\EvenDistributionScheduler;
use App\Schedule\WorkloadPlacement;
use DateTimeImmutable;
use DateTimeZone;
use PHPUnit\Framework\TestCase;

class EvenDistributionSchedulerTest extends TestCase
{
    public function test_it_places_one_heavier_day_at_the_requested_position(): void
    {
        $scheduler = new EvenDistributionScheduler;
        $expectedCounts = [
            WorkloadPlacement::Start->value => [3, 2, 2, 2, 2],
            WorkloadPlacement::Middle->value => [2, 2, 3, 2, 2],
            WorkloadPlacement::End->value => [2, 2, 2, 2, 3],
        ];

        foreach (WorkloadPlacement::cases() as $placement) {
            $dates = $scheduler->scheduledDates(
                assignmentCount: 11,
                startDate: $this->utc('2026-08-10'),
                targetDate: $this->utc('2026-08-14'),
                workloadPlacement: $placement,
            );

            $this->assertSame(
                $expectedCounts[$placement->value],
                $this->dailyCounts($dates),
            );
        }
    }

    public function test_it_keeps_multiple_heavier_days_together(): void
    {
        $scheduler = new EvenDistributionScheduler;
        $expectedCounts = [
            WorkloadPlacement::Start->value => [3, 3, 2, 2, 2],
            WorkloadPlacement::Middle->value => [2, 3, 3, 2, 2],
            WorkloadPlacement::End->value => [2, 2, 2, 3, 3],
        ];

        foreach (WorkloadPlacement::cases() as $placement) {
            $dates = $scheduler->scheduledDates(
                assignmentCount: 12,
                startDate: $this->utc('2026-08-10'),
                targetDate: $this->utc('2026-08-14'),
                workloadPlacement: $placement,
            );

            $this->assertSame(
                $expectedCounts[$placement->value],
                $this->dailyCounts($dates),
            );
        }
    }

    public function test_it_places_sparse_assignments_at_the_requested_position(): void
    {
        $scheduler = new EvenDistributionScheduler;
        $expectedDates = [
            WorkloadPlacement::Spread->value => [
                '2026-08-10',
                '2026-08-12',
                '2026-08-13',
                '2026-08-15',
            ],
            WorkloadPlacement::Start->value => [
                '2026-08-10',
                '2026-08-11',
                '2026-08-12',
                '2026-08-13',
            ],
            WorkloadPlacement::Middle->value => [
                '2026-08-11',
                '2026-08-12',
                '2026-08-13',
                '2026-08-14',
            ],
            WorkloadPlacement::End->value => [
                '2026-08-12',
                '2026-08-13',
                '2026-08-14',
                '2026-08-15',
            ],
        ];

        foreach (WorkloadPlacement::cases() as $placement) {
            $dates = $scheduler->scheduledDates(
                assignmentCount: 4,
                startDate: $this->utc('2026-08-10'),
                targetDate: $this->utc('2026-08-15'),
                workloadPlacement: $placement,
            );

            $this->assertSame(
                $expectedDates[$placement->value],
                $this->formattedDates($dates),
            );
        }
    }

    public function test_it_places_one_assignment_at_the_requested_position(): void
    {
        $scheduler = new EvenDistributionScheduler;
        $expectedDates = [
            WorkloadPlacement::Spread->value => '2026-08-10',
            WorkloadPlacement::Start->value => '2026-08-10',
            WorkloadPlacement::Middle->value => '2026-08-12',
            WorkloadPlacement::End->value => '2026-08-15',
        ];

        foreach (WorkloadPlacement::cases() as $placement) {
            $dates = $scheduler->scheduledDates(
                assignmentCount: 1,
                startDate: $this->utc('2026-08-10'),
                targetDate: $this->utc('2026-08-15'),
                workloadPlacement: $placement,
            );

            $this->assertSame(
                [$expectedDates[$placement->value]],
                $this->formattedDates($dates),
            );
        }
    }

    public function test_it_distributes_even_and_single_day_schedules(): void
    {
        $scheduler = new EvenDistributionScheduler;

        $evenDates = $scheduler->scheduledDates(
            assignmentCount: 10,
            startDate: $this->utc('2026-08-10'),
            targetDate: $this->utc('2026-08-14'),
            workloadPlacement: WorkloadPlacement::End,
        );
        $singleDayDates = $scheduler->scheduledDates(
            assignmentCount: 4,
            startDate: $this->utc('2026-08-10'),
            targetDate: $this->utc('2026-08-10'),
            workloadPlacement: WorkloadPlacement::Middle,
        );

        $this->assertSame([2, 2, 2, 2, 2], $this->dailyCounts($evenDates));
        $this->assertSame(
            [
                '2026-08-10',
                '2026-08-10',
                '2026-08-10',
                '2026-08-10',
            ],
            $this->formattedDates($singleDayDates),
        );
    }

    /**
     * @param list<DateTimeImmutable> $dates
     * @return list<int>
     */
    private function dailyCounts(array $dates): array
    {
        return array_values(array_count_values($this->formattedDates($dates)));
    }

    /**
     * @param list<DateTimeImmutable> $dates
     * @return list<string>
     */
    private function formattedDates(array $dates): array
    {
        return array_map(function (DateTimeImmutable $date): string {
            return $date->format('Y-m-d');
        }, $dates);
    }

    private function utc(string $date): DateTimeImmutable
    {
        return new DateTimeImmutable($date, new DateTimeZone('UTC'));
    }
}