<?php

declare(strict_types=1);

namespace LinkCheckup\Features\Scanning;

use LinkCheckup\Shared\Scan\ScanPhase;
use LinkCheckup\Shared\Scan\ScanRunState;
use LinkCheckup\Shared\Scan\ScanState;

final class ScanTransitions {

	public function started( ScanState $state, int $now ): ScanState {
		return new ScanState(
			run_state: ScanRunState::Running,
			phase: ScanPhase::Reading,
			started_at: $now,
			finished_at: $state->finished_at,
			posts_count: $state->posts_count,
			first_run: $state->first_run
		);
	}

	public function with_run_state(
		ScanState $state,
		ScanRunState $run_state
	): ScanState {
		return $this->changed(
			$state,
			$run_state,
			$state->phase,
			$state->last_read_post_id,
			$state->posts_read
		);
	}

	public function cancelled( ScanState $state ): ScanState {
		return new ScanState(
			finished_at: $state->finished_at,
			posts_count: $state->posts_count,
			first_run: $state->first_run
		);
	}

	public function advanced(
		ScanState $state,
		int $last_read_post_id,
		int $posts_read_now
	): ScanState {
		return $this->changed(
			$state,
			$state->run_state,
			$state->phase,
			$last_read_post_id,
			$state->posts_read + $posts_read_now
		);
	}

	public function checking( ScanState $state ): ScanState {
		return $this->changed(
			$state,
			$state->run_state,
			ScanPhase::Checking,
			$state->last_read_post_id,
			$state->posts_read
		);
	}

	public function finished( ScanState $state, int $now ): ScanState {
		return new ScanState(
			finished_at: $now,
			posts_count: $state->posts_read,
			first_run: false
		);
	}

	private function changed(
		ScanState $state,
		ScanRunState $run_state,
		ScanPhase|null $phase,
		int $last_read_post_id,
		int $posts_read
	): ScanState {
		return new ScanState(
			run_state: $run_state,
			phase: $phase,
			started_at: $state->started_at,
			last_read_post_id: $last_read_post_id,
			posts_read: $posts_read,
			finished_at: $state->finished_at,
			posts_count: $state->posts_count,
			first_run: $state->first_run
		);
	}
}