<?php

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/** A safe, provider-independent failure classification for background jobs. */
final class AI_Narration_Provider_Exception extends RuntimeException {
	private const DEFAULT_RATE_LIMIT_DELAY = 5 * MINUTE_IN_SECONDS;

	private bool $retryable_failure;
	private int $retry_after_seconds;

	private function __construct( string $message, bool $retryable, int $retry_after = 0 ) {
		parent::__construct( $message );
		$this->retryable_failure = $retryable;
		$this->retry_after_seconds = max( 0, $retry_after );
	}

	public static function terminal( string $message ): self {
		return new self( $message, false );
	}

	public static function transient( string $message, int $retry_after = 0 ): self {
		return new self( $message, true, $retry_after );
	}

	/** @param array<string,mixed> $response */
	public static function from_http_response( string $provider, array $response, string $body = '' ): self {
		$provider = sanitize_text_field( $provider );
		$status = (int) wp_remote_retrieve_response_code( $response );
		if ( 429 === $status ) {
			$retry_after = self::retry_after( $response, $body );
			if ( self::is_non_retryable_quota( $body ) && 0 === $retry_after ) {
				return self::terminal( $provider . ' quota or credit allowance is exhausted. Regenerate after it becomes available.' );
			}
			return self::transient(
				$provider . ' temporarily limited narration requests (HTTP 429). Retrying later.',
				$retry_after > 0 ? $retry_after : self::DEFAULT_RATE_LIMIT_DELAY
			);
		}

		if ( 408 === $status || $status >= 500 ) {
			return self::transient( $provider . ' temporarily failed to process narration (HTTP ' . $status . ').' );
		}
		if ( 401 === $status || 403 === $status ) {
			return self::terminal( $provider . ' rejected the configured API credential or its permissions (HTTP ' . $status . ').' );
		}
		if ( $status >= 400 && $status < 500 ) {
			return self::terminal( $provider . ' rejected the narration request (HTTP ' . $status . ').' );
		}

		return self::transient( $provider . ' returned an invalid narration response (HTTP ' . $status . ').' );
	}

	public function is_retryable(): bool {
		return $this->retryable_failure;
	}

	public function retry_delay( int $attempt ): int {
		$base = $this->retry_after_seconds > 0 ? $this->retry_after_seconds : 30;
		$multiplier = max( 1, 2 ** max( 0, $attempt - 1 ) );
		return $base * $multiplier;
	}

	/** @param array<string,mixed> $response */
	private static function retry_after( array $response, string $body ): int {
		$header = wp_remote_retrieve_header( $response, 'retry-after' );
		$header = is_array( $header ) ? reset( $header ) : $header;
		if ( is_scalar( $header ) ) {
			$value = trim( (string) $header );
			if ( ctype_digit( $value ) ) {
				return max( 1, (int) $value );
			}
			$timestamp = strtotime( $value );
			if ( false !== $timestamp ) {
				return max( 1, $timestamp - time() );
			}
		}

		$payload = json_decode( $body, true );
		return is_array( $payload ) ? self::retry_delay_from_payload( $payload ) : 0;
	}

	/** @param array<string,mixed> $payload */
	private static function retry_delay_from_payload( array $payload ): int {
		foreach ( $payload as $key => $value ) {
			$key = strtolower( (string) $key );
			if ( in_array( $key, array( 'retrydelay', 'retry_delay', 'quotaresetdelay', 'quota_reset_delay' ), true ) && is_scalar( $value ) ) {
				$seconds = self::duration_seconds( (string) $value );
				if ( $seconds > 0 ) {
					return $seconds;
				}
			}
			if ( is_array( $value ) ) {
				$seconds = self::retry_delay_from_payload( $value );
				if ( $seconds > 0 ) {
					return $seconds;
				}
			}
		}
		return 0;
	}

	private static function duration_seconds( string $value ): int {
		$value = strtolower( trim( $value ) );
		if ( is_numeric( $value ) ) {
			return max( 1, (int) ceil( (float) $value ) );
		}
		if ( preg_match( '/^(?:(\d+(?:\.\d+)?)h)?(?:(\d+(?:\.\d+)?)m)?(?:(\d+(?:\.\d+)?)s)?$/', $value, $matches ) ) {
			$hours = isset( $matches[1] ) && '' !== $matches[1] ? (float) $matches[1] : 0.0;
			$minutes = isset( $matches[2] ) && '' !== $matches[2] ? (float) $matches[2] : 0.0;
			$seconds = isset( $matches[3] ) && '' !== $matches[3] ? (float) $matches[3] : 0.0;
			return max( 0, (int) ceil( ( $hours * HOUR_IN_SECONDS ) + ( $minutes * MINUTE_IN_SECONDS ) + $seconds ) );
		}
		return 0;
	}

	private static function is_non_retryable_quota( string $body ): bool {
		$body = strtolower( $body );
		foreach ( array( 'daily quota', 'daily limit', 'per day', 'per_day', 'perday', 'requests per day', 'request_per_day', 'requestsperday', '"rpd"', 'insufficient_quota', 'insufficient credits', 'insufficient_credits', 'billing_hard_limit' ) as $marker ) {
			if ( str_contains( $body, $marker ) ) {
				return true;
			}
		}
		return false;
	}
}