<?php
/**
 * USD cost of an OpenAI image call from its usage block.
 *
 * @package Fitzaro
 */

namespace Fitzaro\Provider\OpenAi;

use Fitzaro\Limits\Money;

defined( 'ABSPATH' ) || exit;

/**
 * A price per million tokens is the price in micro-dollars per token, so the sum is computed in
 * micro-dollars and returned as a six-place decimal string, like the cost column.
 */
final class ImageCost {

	/**
	 * Cost, or null when the usage block or the price is missing.
	 *
	 * @param array<string, mixed>          $usage Response usage: input_tokens, input_tokens_details, output_tokens.
	 * @param array<string, int|float>|null $price USD per 1M tokens: text_input, image_input, image_output.
	 */
	public static function from_usage( array $usage, ?array $price ): ?string {
		if ( null === $price || ! isset( $usage['output_tokens'] ) || ! is_int( $usage['output_tokens'] ) ) {
			return null;
		}

		$details = isset( $usage['input_tokens_details'] ) && is_array( $usage['input_tokens_details'] ) ? $usage['input_tokens_details'] : array();
		$text    = (int) ( $details['text_tokens'] ?? 0 );
		$image   = (int) ( $details['image_tokens'] ?? 0 );

		// No breakdown: price all input at the image rate, so the cost is over- rather than under-stated.
		if ( 0 === $text && 0 === $image ) {
			$image = (int) ( $usage['input_tokens'] ?? 0 );
		}

		$micros = $text * (float) ( $price['text_input'] ?? 0 )
			+ $image * (float) ( $price['image_input'] ?? 0 )
			+ $usage['output_tokens'] * (float) ( $price['image_output'] ?? 0 );

		return Money::format( (int) ceil( round( $micros, 6 ) ) );
	}
}