<?php
/**
 * Zone C (Cold) handler for JSON blob storage with Object Cache integration.
 *
 * @package WP_Data_Optimizer
 */

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

/**
 * Zone C (Cold) handler — JSON blob storage with Object Cache integration.
 *
 * Each post type gets its own table: wpdo_cold_{post_type}
 * All cold meta_keys for a post are stored as a single JSON blob in the `data` column.
 *
 * Read path: Object Cache → cold table → wp_postmeta fallback
 * Write path: cold table + Object Cache invalidation
 *
 * Best for profile/display data that is read often but queried rarely
 * (e.g. hp_description, social links, extended profile fields).
 */
class TMDO_Zone_Cold {

	/**
	 * Get the cold table name for a post type.
	 *
	 * @param string $post_type Post type slug.
	 * @return string Full table name.
	 */
	public static function table( string $post_type ): string {
		return TMDO_DB::table( 'wpdo_cold_' . sanitize_key( $post_type ) );
	}

	/**
	 * Cache group for a post type.
	 *
	 * @param string $post_type Post type slug.
	 * @return string Cache group name.
	 */
	private static function cache_group( string $post_type ): string {
		return 'wpdo_cold_' . sanitize_key( $post_type );
	}

	/**
	 * Ensure the cold table exists for a post type.
	 *
	 * @param string $post_type Post type slug.
	 * @return void
	 */
	public static function ensure_table( string $post_type ): void {
		global $wpdb;
		$table = self::table( $post_type );

		if ( TMDO_IS_SQLITE ) {
			$exists = $wpdb->get_var(
				$wpdb->prepare( "SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name=%s", $table )
			);
		} else {
			$exists = $wpdb->get_var(
				$wpdb->prepare( 'SELECT COUNT(*) FROM information_schema.TABLES WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = %s', $table )
			);
		}

		if ( ! $exists ) {
			TMDO_Installer::create_cold_table( $post_type );
		}
	}

	/**
	 * Get a single cold meta value for a post.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @param string $meta_key  Meta key.
	 * @return mixed|null
	 */
	public static function get( int $post_id, string $post_type, string $meta_key ): mixed {
		$data = self::get_blob( $post_id, $post_type );
		return $data[ $meta_key ] ?? null;
	}

	/**
	 * Get the full JSON blob for a post, with Object Cache layer.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @return array Decoded JSON data (meta_key => value).
	 */
	public static function get_blob( int $post_id, string $post_type ): array {
		$group     = self::cache_group( $post_type );
		$cache_key = "cold_{$post_id}";

		$cached = wp_cache_get( $cache_key, $group );
		if ( false !== $cached ) {
			return is_array( $cached ) ? $cached : array();
		}

		global $wpdb;
		$table = self::table( $post_type );

		$json = $wpdb->get_var(
			$wpdb->prepare( "SELECT data FROM `{$table}` WHERE post_id = %d LIMIT 1", $post_id ) // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name from TMDO_Zone_Cold::table() via TMDO_DB::table().
		);

		$data = $json ? json_decode( $json, true ) : array();
		if ( ! is_array( $data ) ) {
			$data = array();
		}

		// Get cache TTL from registry — 粒度化策略：取所有 cold fields 的最小 TTL，
		// 確保任何短 TTL 欄位（如 IG token：v2.0.4 起預期 < 5 min）能在保護期內失效，
		// 而非被某個長 TTL 欄位拖拽到 1h 才更新。原本的「取第一個」策略會視註冊順序
		// 而異，無法保證安全。
		// 同時提供 `wpdo_cold_cache_ttl` filter 讓 partner integration 進一步覆蓋.
		$fields = TMDO_Schema_Registry::instance()->get_zone_fields_for_type( 'cold', $post_type );
		$ttls   = array();
		foreach ( $fields as $field ) {
			if ( ! empty( $field['cache_ttl'] ) ) {
				$ttls[] = (int) $field['cache_ttl'];
			}
		}
		$ttl = empty( $ttls ) ? HOUR_IN_SECONDS : min( $ttls );

		/**
		 * Filter the effective cache TTL for a cold zone post type.
		 *
		 * @since 2.0.5
		 * @param int    $ttl       Computed TTL (min of all registered fields, or HOUR_IN_SECONDS default).
		 * @param string $post_type Post type being cached.
		 * @param int    $post_id   Post ID (entity being read).
		 * @param array  $fields    Fields registry config for this post_type.
		 */
		$ttl = (int) apply_filters( 'wpdo_cold_cache_ttl', $ttl, $post_type, $post_id, $fields );

		wp_cache_set( $cache_key, $data, $group, $ttl );

		return $data;
	}

	/**
	 * Set a single cold meta value for a post.
	 * Merges into the existing JSON blob.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @param string $meta_key  Meta key.
	 * @param mixed  $value     Value to store.
	 */
	public static function set( int $post_id, string $post_type, string $meta_key, mixed $value ): void {
		self::save_patch( $post_id, $post_type, array( $meta_key => $value ) );
	}

	/**
	 * Set multiple cold meta values at once.
	 *
	 * Uses JSON_MERGE_PATCH on MySQL to avoid a read-then-write round trip.
	 * Falls back to read-modify-write on SQLite.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type.
	 * @param array  $values    meta_key => value pairs.
	 */
	public static function set_many( int $post_id, string $post_type, array $values ): void {
		self::save_patch( $post_id, $post_type, $values );
	}

	/**
	 * Remove a key from the cold blob.
	 *
	 * Uses JSON_REMOVE on MySQL for an atomic single-key removal without a full
	 * blob read. Falls back to read-modify-write on SQLite.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type slug.
	 * @param string $meta_key  Meta key to remove.
	 * @return void
	 */
	public static function remove( int $post_id, string $post_type, string $meta_key ): void {
		if ( defined( 'TMDO_IS_SQLITE' ) && TMDO_IS_SQLITE ) {
			$data = self::get_blob_raw( $post_id, $post_type );
			unset( $data[ $meta_key ] );
			self::save_blob( $post_id, $post_type, $data );
			return;
		}

		global $wpdb;
		$table = self::table( $post_type );
		$path  = '$.' . $meta_key;

		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Table name from TMDO_Zone_Cold::table() via TMDO_DB::table().
		$wpdb->query(
			$wpdb->prepare(
				"UPDATE `{$table}` SET data = JSON_REMOVE(COALESCE(data, '{}'), %s), updated_at = %s WHERE post_id = %d",
				$path,
				TMDO_DB::now(),
				$post_id
			)
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery,WordPress.DB.DirectDatabaseQuery.NoCaching

		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
	}

	/**
	 * Delete the entire cold row for a post.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type slug.
	 * @return void
	 */
	public static function delete( int $post_id, string $post_type ): void {
		global $wpdb;
		$wpdb->delete( self::table( $post_type ), array( 'post_id' => $post_id ), array( '%d' ) );
		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
	}

	// ── Private helpers ───────────────────────────────────────────────────

	/**
	 * Get raw blob from DB (no cache).
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type slug.
	 * @return array Decoded JSON data array.
	 */
	private static function get_blob_raw( int $post_id, string $post_type ): array {
		global $wpdb;
		$table = self::table( $post_type );

		$json = $wpdb->get_var(
			$wpdb->prepare( "SELECT data FROM `{$table}` WHERE post_id = %d LIMIT 1", $post_id ) // phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Table name from TMDO_Zone_Cold::table() via TMDO_DB::table().
		);

		$data = $json ? json_decode( $json, true ) : array();
		return is_array( $data ) ? $data : array();
	}

	/**
	 * Save the JSON blob and invalidate cache.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type slug.
	 * @param array  $data      Key-value pairs to store as JSON.
	 * @return void
	 */
	private static function save_blob( int $post_id, string $post_type, array $data ): void {
		$table = self::table( $post_type );
		$json  = wp_json_encode( $data );

		TMDO_DB::upsert(
			$table,
			array(
				'post_id'    => $post_id,
				'data'       => $json,
				'updated_at' => TMDO_DB::now(),
			),
			array( 'data', 'updated_at' ),
			'post_id',
			array( '%d', '%s', '%s' )
		);

		// Invalidate object cache.
		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
	}

	/**
	 * Merge a partial key-value map into the cold blob atomically.
	 *
	 * Uses INSERT ... ON DUPLICATE KEY UPDATE with JSON_MERGE_PATCH so concurrent
	 * writers cannot clobber each other's keys (the read-modify-write path did).
	 * On SQLite, falls back to the classic read-modify-write path.
	 *
	 * @param int    $post_id   Post ID.
	 * @param string $post_type Post type slug.
	 * @param array  $patch     Partial key-value map to merge in.
	 */
	private static function save_patch( int $post_id, string $post_type, array $patch ): void {
		if ( defined( 'TMDO_IS_SQLITE' ) && TMDO_IS_SQLITE ) {
			$data = self::get_blob_raw( $post_id, $post_type );
			$data = array_merge( $data, $patch );
			self::save_blob( $post_id, $post_type, $data );
			return;
		}

		global $wpdb;
		$table = self::table( $post_type );
		$json  = wp_json_encode( $patch );
		$now   = TMDO_DB::now();

		// phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- Table name from TMDO_Zone_Cold::table() via TMDO_DB::table().
		$wpdb->query(
			$wpdb->prepare(
				"INSERT INTO `{$table}` (post_id, data, updated_at) VALUES (%d, %s, %s)
				 ON DUPLICATE KEY UPDATE data = JSON_MERGE_PATCH(COALESCE(data, '{}'), %s), updated_at = %s",
				$post_id,
				$json,
				$now,
				$json,
				$now
			)
		);
		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery,WordPress.DB.DirectDatabaseQuery.NoCaching

		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
	}
}