<?php
/**
 * Outcome of submit() or poll().
 *
 * @package Fitzaro
 */

namespace Fitzaro\Provider;

defined( 'ABSPATH' ) || exit;

/**
 * Exactly one of: done (image ready), pending (poll again later) or failed.
 */
final class Submission {

	private const DONE    = 'done';
	private const PENDING = 'pending';
	private const FAILED  = 'failed';

	/**
	 * One of the constants above.
	 *
	 * @var string
	 */
	private $state;

	/**
	 * Result image bytes when done.
	 *
	 * @var string|null
	 */
	private $image;

	/**
	 * Model that produced the image.
	 *
	 * @var string
	 */
	private $model = '';

	/**
	 * Cost in USD as a decimal string, or null when unknown.
	 *
	 * @var string|null
	 */
	private $cost;

	/**
	 * Raw usage block from the provider.
	 *
	 * @var array<string, mixed>
	 */
	private $usage = array();

	/**
	 * Provider's job ID when pending.
	 *
	 * @var string|null
	 */
	private $remote_id;

	/**
	 * Error when failed.
	 *
	 * @var ProviderError|null
	 */
	private $error;

	/**
	 * Use the named constructors.
	 *
	 * @param string $state One of the constants above.
	 */
	private function __construct( string $state ) {
		$this->state = $state;
	}

	/**
	 * The image is ready.
	 *
	 * @param string               $image Image bytes.
	 * @param string               $model Model name.
	 * @param string|null          $cost  USD as a decimal string, or null when unknown.
	 * @param array<string, mixed> $usage Raw usage block.
	 */
	public static function done( string $image, string $model, ?string $cost, array $usage = array() ): self {
		$submission        = new self( self::DONE );
		$submission->image = $image;
		$submission->model = $model;
		$submission->cost  = $cost;
		$submission->usage = $usage;

		return $submission;
	}

	/**
	 * The provider is still working; poll with this ID.
	 *
	 * @param string $remote_id Provider's job ID.
	 */
	public static function pending( string $remote_id ): self {
		$submission            = new self( self::PENDING );
		$submission->remote_id = $remote_id;

		return $submission;
	}

	/**
	 * The generation failed.
	 *
	 * @param ProviderError $error Why.
	 */
	public static function failed( ProviderError $error ): self {
		$submission        = new self( self::FAILED );
		$submission->error = $error;

		return $submission;
	}

	/**
	 * Whether the image is ready.
	 */
	public function is_done(): bool {
		return self::DONE === $this->state;
	}

	/**
	 * Whether the provider is still working.
	 */
	public function is_pending(): bool {
		return self::PENDING === $this->state;
	}

	/**
	 * Whether the generation failed.
	 */
	public function is_failed(): bool {
		return self::FAILED === $this->state;
	}

	/**
	 * Image bytes, when done.
	 */
	public function image(): ?string {
		return $this->image;
	}

	/**
	 * Model name, when done.
	 */
	public function model(): string {
		return $this->model;
	}

	/**
	 * Cost in USD, when done and known.
	 */
	public function cost(): ?string {
		return $this->cost;
	}

	/**
	 * Raw usage block, when done.
	 *
	 * @return array<string, mixed>
	 */
	public function usage(): array {
		return $this->usage;
	}

	/**
	 * Provider's job ID, when pending.
	 */
	public function remote_id(): ?string {
		return $this->remote_id;
	}

	/**
	 * The error, when failed; UNKNOWN otherwise so callers never get null.
	 */
	public function error(): ProviderError {
		return $this->error ?? new ProviderError( ProviderError::UNKNOWN );
	}
}