<?php
/**
 * AI features, through the WordPress AI Client (WordPress 7.0+).
 *
 * The store owner chooses the AI provider in Settings > Connectors. Statbird never holds an
 * API key. Every feature runs only when someone clicks a button (or for the weekly briefing),
 * answers are cached for a day, a monthly cap limits usage, and only aggregate reports are
 * sent unless the owner opts in to sharing customer names.
 *
 * @package Statbird
 */

namespace Statbird;

defined( 'ABSPATH' ) || exit;

/**
 * Prompts, guardrails and usage accounting.
 */
class AI {

	const USAGE = 'statbird_ai_usage';

	/**
	 * Whether an AI provider is connected and AI is switched on.
	 *
	 * @return bool
	 */
	public static function available() {
		if ( ! Settings::get( 'ai_enabled' ) || ! function_exists( 'wp_ai_client_prompt' ) ) {
			return false;
		}
		if ( function_exists( 'wp_supports_ai' ) && ! wp_supports_ai() ) {
			return false;
		}
		$cached = wp_cache_get( 'statbird_ai_available', 'statbird' );
		if ( false !== $cached ) {
			return 'yes' === $cached;
		}
		try {
			$ok = (bool) wp_ai_client_prompt( 'ping' )->is_supported_for_text_generation();
		} catch ( \Throwable $e ) {
			$ok = false;
		}
		wp_cache_set( 'statbird_ai_available', $ok ? 'yes' : 'no', 'statbird', 300 );
		return $ok;
	}

	/**
	 * Why AI is not available, for the interface.
	 *
	 * @return string '', 'off', 'unsupported' (WordPress older than 7.0) or 'no_provider'.
	 */
	public static function status() {
		if ( ! Settings::get( 'ai_enabled' ) ) {
			return 'off';
		}
		if ( ! function_exists( 'wp_ai_client_prompt' ) ) {
			return 'unsupported';
		}
		return self::available() ? '' : 'no_provider';
	}

	/**
	 * This month's usage.
	 *
	 * @return array{month:string,count:int,features:array}
	 */
	public static function usage() {
		$u = get_option( self::USAGE, array() );
		if ( ! is_array( $u ) || ( $u['month'] ?? '' ) !== gmdate( 'Y-m' ) ) {
			$u = array(
				'month'    => gmdate( 'Y-m' ),
				'count'    => 0,
				'features' => array(),
			);
		}
		return $u;
	}

	/**
	 * Records one AI call.
	 *
	 * @param string $feature Feature key.
	 */
	private static function count_call( $feature ) {
		$u                         = self::usage();
		$u['count']               += 1;
		$u['features'][ $feature ] = ( $u['features'][ $feature ] ?? 0 ) + 1;
		update_option( self::USAGE, $u, false );
	}

	/**
	 * Sends a prompt, with caching, the monthly cap and error handling.
	 *
	 * @param string $feature  Feature key (for usage and cache).
	 * @param string $system   System instruction.
	 * @param string $prompt   User prompt.
	 * @param bool   $fresh    Skip the cache.
	 * @param array  $schema   Optional JSON schema; the answer is decoded when given.
	 * @return string|array|\WP_Error
	 */
	public static function ask_model( $feature, $system, $prompt, $fresh = false, array $schema = array() ) {
		if ( ! self::available() ) {
			return new \WP_Error( 'statbird_ai_unavailable', __( 'AI is not available. Connect an AI provider in Settings > Connectors.', 'statbird' ) );
		}
		$key = 'statbird_ai_' . md5( $feature . '|' . $system . '|' . $prompt . '|' . wp_json_encode( $schema ) );
		if ( ! $fresh ) {
			$hit = get_transient( $key );
			if ( false !== $hit ) {
				return $hit;
			}
		}
		$cap = (int) Settings::get( 'ai_monthly_cap' );
		if ( self::usage()['count'] >= $cap ) {
			return new \WP_Error( 'statbird_ai_cap', __( 'This month\'s AI limit has been reached. You can raise it in Statbird settings.', 'statbird' ) );
		}
		try {
			$builder = wp_ai_client_prompt( $prompt )->using_system_instruction( $system )->using_max_tokens( 900 )->using_temperature( 0.3 );
			if ( $schema ) {
				$builder = $builder->as_json_response( $schema );
			}
			$text = $builder->generate_text();
		} catch ( \Throwable $e ) {
			$text = new \WP_Error( 'statbird_ai_error', $e->getMessage() );
		}
		self::count_call( $feature );
		if ( is_wp_error( $text ) ) {
			return $text;
		}
		$out = trim( (string) $text );
		if ( $schema ) {
			$decoded = self::decode_json( $out );
			if ( null === $decoded ) {
				return new \WP_Error( 'statbird_ai_bad_json', __( 'The AI answer could not be read. Please try again.', 'statbird' ) );
			}
			$out = $decoded;
		}
		set_transient( $key, $out, DAY_IN_SECONDS );
		return $out;
	}

	/**
	 * Decodes JSON, also when the model wrapped it in a code fence.
	 *
	 * @param string $text Model output.
	 * @return array|null
	 */
	public static function decode_json( $text ) {
		$text = trim( $text );
		if ( preg_match( '/```(?:json)?\s*(.+?)```/s', $text, $m ) ) {
			$text = trim( $m[1] );
		}
		$data = json_decode( $text, true );
		if ( ! is_array( $data ) && preg_match( '/\{.*\}/s', $text, $m ) ) {
			$data = json_decode( $m[0], true );
		}
		return is_array( $data ) ? $data : null;
	}

	/**
	 * The house rules every prompt starts with.
	 *
	 * @return string
	 */
	private static function system() {
		return 'You are the analyst inside Statbird, a customer analytics plugin for a WooCommerce store. '
			. 'Use only the data you are given. Never invent numbers, customers or products. If the data does not answer the question, say so plainly. '
			. 'Write for a busy shop owner: short sentences, plain words, no jargon, no markdown headings. '
			. 'Money is in ' . get_woocommerce_currency() . '. Round sensibly.';
	}

	/**
	 * Monthly summary in plain words.
	 *
	 * @param bool $fresh Ignore the cache.
	 * @return string|\WP_Error
	 */
	public static function summary( $fresh = false ) {
		$data   = array(
			'overview' => Reports::run( 'overview' ),
			'groups'   => Reports::run( 'groups' ),
			'changes'  => Reports::run( 'changes' ),
			'trends'   => Reports::run( 'trends' )['anomalies'],
		);
		$prompt = "Write 3 to 4 sentences summarising how this store's customers are doing this month: what is good, what needs attention, and the single most useful next step. Data:\n" . wp_json_encode( $data );
		return self::ask_model( 'summary', self::system(), $prompt, $fresh );
	}

	/**
	 * Next best action and a draft message for one group.
	 *
	 * @param string $group Group key.
	 * @param bool   $fresh Ignore the cache.
	 * @return array|\WP_Error Array with action, why, subject, message.
	 */
	public static function next_action( $group, $fresh = false ) {
		$detail = Reports::group_detail( $group );
		if ( isset( $detail['error'] ) ) {
			return new \WP_Error( 'statbird_bad_group', __( 'Unknown group.', 'statbird' ) );
		}
		$schema = array(
			'type'       => 'object',
			'properties' => array(
				'action'  => array( 'type' => 'string' ),
				'why'     => array( 'type' => 'string' ),
				'subject' => array( 'type' => 'string' ),
				'message' => array( 'type' => 'string' ),
			),
			'required'   => array( 'action', 'why', 'subject', 'message' ),
		);
		$prompt = 'Suggest the single best action for this customer group, why it fits the numbers, and a short email the shop could send them. '
			. 'Use {first_name} where the customer\'s name goes. Keep the email under 120 words, warm and specific to what they buy. Group data:' . "\n" . wp_json_encode( $detail );
		return self::ask_model( 'next_action', self::system(), $prompt, $fresh, $schema );
	}

	/**
	 * Explains an unusual week.
	 *
	 * @param int  $index Anomaly index in the snapshot.
	 * @param bool $fresh Ignore the cache.
	 * @return string|\WP_Error
	 */
	public static function explain( $index, $fresh = false ) {
		$snap = Insights::get();
		$a    = $snap['anomalies'][ $index ] ?? null;
		if ( ! $a ) {
			return new \WP_Error( 'statbird_no_anomaly', __( 'That change is no longer in the latest data.', 'statbird' ) );
		}
		$data   = array(
			'unusual_week' => $a,
			'weeks'        => array_slice( $snap['weeks'] ?? array(), -13 ),
			'moves_30d'    => Changes::flows( 30 ),
			'groups'       => Reports::run( 'groups' ),
		);
		$prompt = 'One weekly number moved a lot. In 2 to 4 sentences, explain the most likely reasons using only this data, and say what to check next. If the data cannot tell, say what is missing. Data:' . "\n" . wp_json_encode( $data );
		return self::ask_model( 'explain', self::system(), $prompt, $fresh );
	}

	/**
	 * Turns product patterns into ideas.
	 *
	 * @param bool $fresh Ignore the cache.
	 * @return string|\WP_Error
	 */
	public static function pattern_ideas( $fresh = false ) {
		$prompt = 'Here are products bought together, and what customers come back for next with the usual number of days in between. Suggest 3 concrete ideas (bundles, reminder emails timed to the usual gap, cross-sells). One line each. Data:' . "\n" . wp_json_encode( Reports::run( 'patterns' ) );
		return self::ask_model( 'patterns', self::system(), $prompt, $fresh );
	}

	/**
	 * Answers a question about the store, using only the built-in reports.
	 *
	 * Step 1 asks the model which reports it needs (it cannot run anything else).
	 * Step 2 runs those reports here and asks for an answer from them.
	 *
	 * @param string $question Owner's question.
	 * @return array|\WP_Error Array with answer and the reports used.
	 */
	public static function ask( $question ) {
		$question = trim( wp_strip_all_tags( $question ) );
		if ( '' === $question ) {
			return new \WP_Error( 'statbird_empty', __( 'Type a question first.', 'statbird' ) );
		}
		$question = mb_substr( $question, 0, 400 );
		$plan     = self::ask_model(
			'ask_plan',
			self::system(),
			"Choose which reports are needed to answer the owner's question. Pick 1 to 3. For group_detail also give the group key.\n"
				. 'Reports: ' . wp_json_encode( Reports::catalogue() ) . "\n"
				. 'Group keys: ' . wp_json_encode( array_keys( Scoring::groups() ) ) . "\n"
				. 'Question: ' . $question,
			false,
			array(
				'type'       => 'object',
				'properties' => array(
					'reports' => array(
						'type'  => 'array',
						'items' => array(
							'type'       => 'object',
							'properties' => array(
								'id'    => array(
									'type' => 'string',
									'enum' => array_keys( Reports::catalogue() ),
								),
								'group' => array( 'type' => 'string' ),
							),
							'required'   => array( 'id' ),
						),
					),
				),
				'required'   => array( 'reports' ),
			)
		);
		if ( is_wp_error( $plan ) ) {
			return $plan;
		}
		$data = array();
		$used = array();
		foreach ( array_slice( (array) ( $plan['reports'] ?? array() ), 0, 3 ) as $r ) {
			$id = (string) ( $r['id'] ?? '' );
			if ( ! isset( Reports::catalogue()[ $id ] ) ) {
				continue;
			}
			$args           = isset( $r['group'] ) ? array( 'group' => sanitize_key( $r['group'] ) ) : array();
			$label          = $id . ( $args ? ':' . $args['group'] : '' );
			$data[ $label ] = Reports::run( $id, $args );
			$used[]         = $label;
		}
		if ( ! $data ) {
			$data['overview'] = Reports::run( 'overview' );
			$used[]           = 'overview';
		}
		$answer = self::ask_model( 'ask_answer', self::system(), 'Answer the question in 2 to 5 sentences from this data only. Question: ' . $question . "\nData:\n" . wp_json_encode( $data ) );
		if ( is_wp_error( $answer ) ) {
			return $answer;
		}
		return array(
			'answer'  => $answer,
			'reports' => $used,
		);
	}
}