<?php
/**
 * Google Gemini provider for AI content generation.
 *
 * Uses gemini-1.5-flash for fast, cost-effective product copy generation.
 *
 * @package AICommerce\Content
 */

declare(strict_types=1);

namespace AICommerce\Content;

use AICommerce\Content\Contracts\AIProviderException;
use AICommerce\Content\Contracts\AIProviderInterface;
use AICommerce\Core\Encryption;

/**
 * Google Gemini 1.5 Flash provider.
 */
class GeminiProvider implements AIProviderInterface {

	/**
	 * Base API endpoint.
	 *
	 * @var string
	 */
	private const ENDPOINT_BASE = 'https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-flash:generateContent'; // phpcs:ignore PluginCheck.CodeAnalysis.AIProvider.DirectIntegration -- BYOK integration; WP AI Client requires WP 7.0, this plugin supports WP 6.4+.

	/**
	 * Cost per 1K input tokens in USD.
	 *
	 * @var float
	 */
	private const INPUT_COST_PER_1K = 0.000075;

	/**
	 * Cost per 1K output tokens in USD.
	 *
	 * @var float
	 */
	private const OUTPUT_COST_PER_1K = 0.0003;

	/**
	 * Encryption helper.
	 *
	 * @var Encryption
	 */
	private Encryption $encryption;

	/**
	 * Constructor.
	 *
	 * @param Encryption $encryption Encryption helper for API key management.
	 */
	public function __construct( Encryption $encryption ) {
		$this->encryption = $encryption;
	}

	/**
	 * {@inheritDoc}
	 */
	public function complete( string $prompt, int $max_tokens = 600 ): string {
		$api_key = $this->get_api_key();

		if ( empty( $api_key ) ) {
			throw new AIProviderException( esc_html__( 'Gemini API key is not configured.', 'ai-discoverability-kit' ) );
		}

		$body = array(
			'contents'         => array(
				array(
					'parts' => array(
						array( 'text' => $prompt ),
					),
				),
			),
			'generationConfig' => array(
				'maxOutputTokens' => $max_tokens,
			),
		);

		$endpoint = self::ENDPOINT_BASE . '?key=' . $api_key;

		$response = wp_remote_post(
			$endpoint,
			array(
				'timeout' => 45,
				'headers' => array(
					'Content-Type' => 'application/json',
				),
				'body'    => wp_json_encode( $body ),
			)
		);

		if ( is_wp_error( $response ) ) {
			throw new AIProviderException( esc_html( $response->get_error_message() ) );
		}

		$status = wp_remote_retrieve_response_code( $response );
		$body   = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( 200 !== $status ) {
			$error_msg = $body['error']['message'] ?? __( 'Unknown Gemini API error.', 'ai-discoverability-kit' );
			throw new AIProviderException( esc_html( $error_msg ) );
		}

		return trim( $body['candidates'][0]['content']['parts'][0]['text'] ?? '' );
	}

	/**
	 * {@inheritDoc}
	 */
	public function validate_api_key(): bool {
		$api_key = $this->get_api_key();

		if ( empty( $api_key ) ) {
			return false;
		}

		try {
			$body = array(
				'contents'         => array(
					array(
						'parts' => array(
							array( 'text' => 'hi' ),
						),
					),
				),
				'generationConfig' => array(
					'maxOutputTokens' => 5,
				),
			);

			$response = wp_remote_post(
				self::ENDPOINT_BASE . '?key=' . $api_key,
				array(
					'timeout' => 15,
					'headers' => array( 'Content-Type' => 'application/json' ),
					'body'    => wp_json_encode( $body ),
				)
			);

			if ( is_wp_error( $response ) ) {
				return false;
			}

			$body = json_decode( wp_remote_retrieve_body( $response ), true );

			return isset( $body['candidates'] ) && is_array( $body['candidates'] );
		} catch ( \Exception $e ) {
			return false;
		}
	}

	/**
	 * {@inheritDoc}
	 */
	public function get_provider_name(): string {
		return 'gemini';
	}

	/**
	 * {@inheritDoc}
	 */
	public function estimate_cost_usd( int $input_tokens, int $output_tokens ): float {
		return ( $input_tokens / 1000 * self::INPUT_COST_PER_1K )
			+ ( $output_tokens / 1000 * self::OUTPUT_COST_PER_1K );
	}

	/**
	 * Get the decrypted API key.
	 *
	 * @return string Decrypted API key, or empty string if not set.
	 */
	private function get_api_key(): string {
		$encrypted = get_option( 'aicommerce_gemini_api_key', '' );

		if ( empty( $encrypted ) ) {
			return '';
		}

		return $this->encryption->decrypt( $encrypted );
	}
}