<?php
/**
 * Checkout presence, local browser signals, and the agent name field.
 *
 * A name still comes from a signature, a published token, or the agent field.
 * Signals never invent a product name. No trusted checkout input, or a browser
 * that reports itself as automated, becomes Unattended. A missing script stays
 * on the classifier result.
 *
 * @package AgentStamp
 */

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

class AgentStamp_Witness {

	/**
	 * @param array<string,mixed> $post
	 * @param array<string,mixed> $cookie
	 * @param mixed               $bot_score
	 * @return array{presence:string,signals:string[],disclosure:string,bot_score:?int}
	 */
	public static function read_client( array $post, array $cookie, $bot_score, $now = null ) {
		$now      = null === $now ? time() : (int) $now;
		$presence = self::pick( $post, $cookie, 'agent_stamp_presence', 'agent_stamp_w', $now );
		$signals  = self::pick( $post, $cookie, 'agent_stamp_signals', 'agent_stamp_s', $now );
		$name     = self::pick( $post, $cookie, 'agent_stamp_disclosure', 'agent_stamp_d', $now );
		if ( function_exists( 'wp_unslash' ) ) {
			$presence = wp_unslash( $presence );
			$signals  = wp_unslash( $signals );
			$name     = wp_unslash( $name );
		}

		return array(
			'presence'   => self::presence( $presence ),
			'signals'    => self::signals( $signals ),
			'disclosure' => self::disclosure_name( $name, $post ),
			'bot_score'  => self::bot_score( $bot_score ),
		);
	}

	/**
	 * @param array{verdict:string,name:string,confidence:string,detail:string} $result
	 * @param array{presence:string,signals:string[],disclosure:string,bot_score:?int} $client
	 * @return array{verdict:string,name:string,confidence:string,detail:string,presence:string}
	 */
	public static function merge( array $result, array $client ) {
		$presence = isset( $client['presence'] ) ? (string) $client['presence'] : '';
		$signals  = isset( $client['signals'] ) && is_array( $client['signals'] ) ? $client['signals'] : array();
		$named    = isset( $client['disclosure'] ) ? (string) $client['disclosure'] : '';
		$score    = isset( $client['bot_score'] ) ? $client['bot_score'] : null;
		$result['presence'] = $presence;

		if ( self::signature_failed( $result ) ) {
			return $result;
		}

		if ( 'agent' === $result['verdict'] ) {
			if ( '' !== $named && $named !== $result['name'] ) {
				$result['detail'] .= ' Agent field said ' . $named . '.';
			}
			return $result;
		}

		if ( '' !== $named && 'human' === $result['verdict'] ) {
			$result['verdict']    = 'agent';
			$result['name']       = $named;
			$result['confidence'] = 'declared';
			$result['detail']     = 'The checkout agent field said ' . $named . '. The request was not signed.';
			return $result;
		}

		if ( 'human' === $result['verdict'] && self::is_unattended( $presence, $signals ) ) {
			$result['verdict']    = 'unattended';
			$result['name']       = '';
			$result['confidence'] = 'witness';
			$result['detail']     = self::unattended_detail( $signals, $score );
			return $result;
		}

		if ( 'human' === $result['verdict'] && 'present' === $presence && count( self::driving_signals( $signals ) ) >= 2 ) {
			$result['verdict']    = 'likely';
			$result['name']       = '';
			$result['confidence'] = 'signals';
			$result['detail']     = self::likely_detail( self::driving_signals( $signals ) );
			return $result;
		}

		if ( 'human' === $result['verdict'] && 'present' === $presence && in_array( 'mismatch', $signals, true ) ) {
			$result['detail'] .= ' Browser platform hints did not match the user-agent. A person used the checkout.';
		}

		return $result;
	}

	/**
	 * @param string              $raw
	 * @param array<string,mixed> $post
	 * @return string
	 */
	public static function disclosure_name( $raw, array $post ) {
		$raw = trim( (string) $raw );
		if ( '' === $raw ) {
			return '';
		}
		if ( preg_match( '/(?:^|[;(\s])Agent\/([A-Za-z][A-Za-z0-9._-]{0,40})/i', $raw, $match ) ) {
			$raw = $match[1];
		}
		$raw = trim( $raw );
		if ( ! preg_match( '/^[A-Za-z][A-Za-z0-9._ -]{0,39}$/', $raw ) ) {
			return '';
		}
		if ( self::is_customer_value( $raw, $post ) || self::is_blocked_name( $raw ) ) {
			return '';
		}
		return $raw;
	}

	/**
	 * @param string $presence
	 * @param string[] $signals
	 * @return bool
	 */
	private static function is_unattended( $presence, array $signals ) {
		if ( in_array( 'webdriver', $signals, true ) ) {
			return true;
		}
		return 'unattended' === $presence;
	}

	/**
	 * Signals that a program drove a real browser. Each one alone is common enough in people to be ignored.
	 *
	 * @param string[] $signals
	 * @return string[]
	 */
	private static function driving_signals( array $signals ) {
		return array_values( array_intersect( $signals, array( 'nomouse', 'center', 'inserted', 'mismatch', 'webgl' ) ) );
	}

	/**
	 * @param string[] $signals
	 * @return string
	 */
	private static function likely_detail( array $signals ) {
		$text = array(
			'nomouse'  => 'The place-order click came with almost no mouse movement on the page.',
			'center'   => 'The click landed on the exact center of the button.',
			'inserted' => 'Several fields were filled with no keystrokes, no paste and no browser autofill.',
			'mismatch' => 'The user-agent and the browser platform disagree.',
			'webgl'    => 'The graphics renderer does not match the user-agent.',
		);
		$detail = 'A trusted click placed the order, and the page saw signs that a program drove the browser.';
		foreach ( $signals as $signal ) {
			$detail .= ' ' . $text[ $signal ];
		}
		return $detail . ' This is likely, not proof. No agent named itself. Checkout was not blocked.';
	}

	/**
	 * @param string[] $signals
	 * @param ?int     $score
	 * @return string
	 */
	private static function unattended_detail( array $signals, $score ) {
		if ( in_array( 'webdriver', $signals, true ) ) {
			$detail = 'The browser reported it is automated.';
		} else {
			$detail = 'The checkout page loaded and no person used the place-order control.';
		}
		if ( in_array( 'mismatch', $signals, true ) ) {
			$detail .= ' The user-agent and the browser platform disagree.';
		}
		if ( in_array( 'webgl', $signals, true ) ) {
			$detail .= ' The graphics renderer does not match the user-agent.';
		}
		if ( is_int( $score ) && $score <= 30 ) {
			$detail .= ' The host bot score was ' . $score . '.';
		}
		return $detail . ' Checkout was not blocked.';
	}

	/**
	 * @param array{verdict:string,detail:string} $result
	 * @return bool
	 */
	private static function signature_failed( array $result ) {
		if ( 'unknown' !== $result['verdict'] ) {
			return false;
		}
		$detail = isset( $result['detail'] ) ? $result['detail'] : '';
		return false !== stripos( $detail, 'Signature' ) || false !== stripos( $detail, 'not treated as proof' );
	}

	/**
	 * @param array<string,mixed> $post
	 * @param array<string,mixed> $cookie
	 * @param string              $post_key
	 * @param string              $cookie_key
	 * @param int                 $now
	 * @return string
	 */
	private static function pick( array $post, array $cookie, $post_key, $cookie_key, $now ) {
		if ( array_key_exists( $post_key, $post ) && is_string( $post[ $post_key ] ) ) {
			return $post[ $post_key ];
		}
		if ( ! self::cookie_is_fresh( $cookie, $now ) ) {
			return '';
		}
		if ( isset( $cookie[ $cookie_key ] ) && is_string( $cookie[ $cookie_key ] ) ) {
			return $cookie[ $cookie_key ];
		}
		return '';
	}

	/**
	 * Checkout cookies are written at submit. An older visit must not label this order.
	 *
	 * @param array<string,mixed> $cookie
	 * @param int                 $now
	 * @return bool
	 */
	private static function cookie_is_fresh( array $cookie, $now ) {
		if ( ! isset( $cookie['agent_stamp_t'] ) || ! is_string( $cookie['agent_stamp_t'] ) ) {
			return false;
		}
		$issued = $cookie['agent_stamp_t'];
		if ( function_exists( 'wp_unslash' ) ) {
			$issued = wp_unslash( $issued );
		}
		if ( ! preg_match( '/^[0-9]{10}$/', $issued ) ) {
			return false;
		}
		$age = $now - (int) $issued;
		return $age >= -120 && $age <= 180;
	}

	/**
	 * @param string $presence
	 * @return string
	 */
	private static function presence( $presence ) {
		$presence = strtolower( trim( (string) $presence ) );
		if ( 'express' === $presence ) {
			return 'present';
		}
		if ( in_array( $presence, array( 'present', 'unattended' ), true ) ) {
			return $presence;
		}
		return '';
	}

	/**
	 * @param string $raw
	 * @return string[]
	 */
	private static function signals( $raw ) {
		$allowed = array( 'webdriver', 'mismatch', 'webgl', 'nomouse', 'center', 'inserted' );
		$found   = array();
		foreach ( explode( ',', strtolower( (string) $raw ) ) as $part ) {
			$part = trim( $part );
			if ( in_array( $part, $allowed, true ) && ! in_array( $part, $found, true ) ) {
				$found[] = $part;
			}
		}
		return $found;
	}

	/**
	 * @param mixed $score
	 * @return ?int
	 */
	private static function bot_score( $score ) {
		if ( is_int( $score ) && $score >= 1 && $score <= 99 ) {
			return $score;
		}
		if ( is_string( $score ) && preg_match( '/^[1-9][0-9]?$/', $score ) ) {
			return (int) $score;
		}
		return null;
	}

	/**
	 * @param string              $name
	 * @param array<string,mixed> $post
	 * @return bool
	 */
	private static function is_customer_value( $name, array $post ) {
		foreach ( array( 'billing_first_name', 'billing_last_name', 'shipping_first_name', 'shipping_last_name' ) as $key ) {
			if ( ! isset( $post[ $key ] ) || ! is_string( $post[ $key ] ) ) {
				continue;
			}
			$customer = trim( function_exists( 'wp_unslash' ) ? wp_unslash( $post[ $key ] ) : $post[ $key ] );
			if ( '' !== $customer && 0 === strcasecmp( $name, $customer ) ) {
				return true;
			}
		}
		return false;
	}

	/**
	 * @param string $name
	 * @return bool
	 */
	private static function is_blocked_name( $name ) {
		$blocked = array(
			'chrome',
			'safari',
			'firefox',
			'mozilla',
			'windows',
			'macintosh',
			'linux',
			'android',
			'iphone',
			'ipad',
			'human',
			'unknown',
			'agent',
			'edge',
			'opera',
			'samsung',
			'mobile',
			'google',
			'bot',
		);
		return in_array( strtolower( $name ), $blocked, true );
	}
}