<?php
/**
 * What:    AJAX handlers for: batch migrate-to-R2, batch remove-local-files,
 *          test R2 connection, and clear log. All actions are admin-only and
 *          nonce-protected.
 * Who:     wp_ajax_ hooks registered by PR_R2_Ajax::init(). Triggered by the
 *          JS in assets/r2-manager.js via jQuery.post().
 * Depends: global $as3cf (WP Offload Media Lite), PR_R2_Log, PR_R2_Admin_Page.
 *
 * @see  includes/class-r2-admin-page.php  (renders the buttons that trigger these actions)
 * @see  includes/class-r2-log.php         (receives log writes after each file operation)
 * @see  assets/r2-manager.js              (drives the batch loop + progress bar)
 *
 * AJAX actions:
 *   pr_r2_migrate_batch       — upload a batch of unprocessed attachments to R2
 *   pr_r2_remove_local_batch  — delete local copies for a batch of offloaded attachments
 *   pr_r2_test_connection     — verify the R2 bucket is reachable
 *   pr_r2_clear_log           — truncate wp_pr_r2_log
 */

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

class PR_R2_Ajax {

	/** Attachments processed per AJAX call. 10 keeps each call well under 30s. */
	const BATCH_SIZE = 10;

	public static function init(): void {
		add_action( 'wp_ajax_pr_r2_migrate_batch',      [ __CLASS__, 'handle_migrate_batch' ] );
		add_action( 'wp_ajax_pr_r2_remove_local_batch', [ __CLASS__, 'handle_remove_local_batch' ] );
		add_action( 'wp_ajax_pr_r2_test_connection',    [ __CLASS__, 'handle_test_connection' ] );
		add_action( 'wp_ajax_pr_r2_clear_log',          [ __CLASS__, 'handle_clear_log' ] );
	}

	// ── Migrate batch ──────────────────────────────────────────────────────

	/**
	 * Upload one batch of not-yet-offloaded attachments to R2.
	 *
	 * POST params: nonce, batch_size (optional int, capped at 50).
	 * Returns JSON: { processed, succeeded, failed, remaining, done }.
	 *
	 * Side effects: uploads files to R2, writes as3cf_items rows, writes log rows.
	 */
	public static function handle_migrate_batch(): void {
		self::verify_nonce( 'pr_r2_migrate' );
		global $as3cf;
		if ( ! $as3cf ) {
			wp_send_json_error( [ 'message' => 'WP Offload Media Lite is not active.' ] );
		}
		$batch_size = min( 50, max( 1, (int) ( $_POST['batch_size'] ?? self::BATCH_SIZE ) ) );
		$ids        = self::get_not_offloaded_ids( $batch_size );
		if ( empty( $ids ) ) {
			wp_send_json_success( [ 'processed' => 0, 'succeeded' => 0, 'failed' => 0, 'remaining' => 0, 'done' => true ] );
		}
		$upload_handler = $as3cf->get_item_handler( 'upload' );
		$succeeded = 0;
		$failed    = 0;
		foreach ( $ids as $id ) {
			$id        = (int) $id;
			$file_path = get_attached_file( $id ) ?: '';
			try {
				$item = \DeliciousBrains\WP_Offload_Media\Items\Media_Library_Item::create_from_source_id( $id );
				if ( ! $item ) {
					PR_R2_Log::write( $id, $file_path, 'migrate', PR_R2_Log::STATUS_SKIP, 'create_from_source_id returned null' );
					$failed++;
					continue;
				}
				$result = $upload_handler->handle( $item );
				if ( is_wp_error( $result ) ) {
					PR_R2_Log::write( $id, $file_path, 'migrate', PR_R2_Log::STATUS_ERROR, $result->get_error_message() );
					$failed++;
				} else {
					PR_R2_Log::write( $id, $file_path, 'migrate', PR_R2_Log::STATUS_OK );
					$succeeded++;
				}
			} catch ( \Exception $e ) {
				PR_R2_Log::write( $id, $file_path, 'migrate', PR_R2_Log::STATUS_ERROR, $e->getMessage() );
				$failed++;
			}
		}
		$remaining = self::count_not_offloaded();
		wp_send_json_success( [
			'processed' => count( $ids ),
			'succeeded' => $succeeded,
			'failed'    => $failed,
			'remaining' => $remaining,
			'done'      => $remaining === 0,
		] );
	}

	// ── Remove-local batch ─────────────────────────────────────────────────

	/**
	 * Delete local file copies for one batch of already-offloaded attachments.
	 *
	 * POST params: nonce, batch_size (optional int, capped at 50).
	 * Returns JSON: { processed, removed, skipped, remaining, done }.
	 *
	 * Side effects: deletes local files from Hostinger disk, writes log rows.
	 */
	public static function handle_remove_local_batch(): void {
		self::verify_nonce( 'pr_r2_remove_local' );
		global $as3cf;
		if ( ! $as3cf ) {
			wp_send_json_error( [ 'message' => 'WP Offload Media Lite is not active.' ] );
		}
		$batch_size     = min( 50, max( 1, (int) ( $_POST['batch_size'] ?? self::BATCH_SIZE ) ) );
		$ids            = self::get_local_remaining_ids( $batch_size );
		if ( empty( $ids ) ) {
			wp_send_json_success( [ 'processed' => 0, 'removed' => 0, 'skipped' => 0, 'remaining' => 0, 'done' => true ] );
		}
		$remove_handler = $as3cf->get_item_handler( 'remove-local' );
		$removed = 0;
		$skipped = 0;
		foreach ( $ids as $id ) {
			$id        = (int) $id;
			$file_path = get_attached_file( $id ) ?: '';
			try {
				$item = \DeliciousBrains\WP_Offload_Media\Items\Media_Library_Item::get_by_source_id( $id );
				if ( ! $item ) {
					PR_R2_Log::write( $id, $file_path, 'remove-local', PR_R2_Log::STATUS_SKIP, 'no as3cf_items row' );
					$skipped++;
					continue;
				}
				$result = $remove_handler->handle( $item );
				if ( is_wp_error( $result ) ) {
					PR_R2_Log::write( $id, $file_path, 'remove-local', PR_R2_Log::STATUS_ERROR, $result->get_error_message() );
					$skipped++;
				} else {
					PR_R2_Log::write( $id, $file_path, 'remove-local', PR_R2_Log::STATUS_OK );
					$removed++;
				}
			} catch ( \Exception $e ) {
				PR_R2_Log::write( $id, $file_path, 'remove-local', PR_R2_Log::STATUS_ERROR, $e->getMessage() );
				$skipped++;
			}
		}
		$remaining = self::count_local_remaining();
		wp_send_json_success( [
			'processed' => count( $ids ),
			'removed'   => $removed,
			'skipped'   => $skipped,
			'remaining' => $remaining,
			'done'      => $remaining === 0,
		] );
	}

	// ── Test R2 connection ─────────────────────────────────────────────────

	/**
	 * Verify the R2 bucket is reachable via a read-only ListObjects call.
	 *
	 * POST params: nonce.
	 * Returns JSON: success { message } | error { message }.
	 *
	 * Side effects: one S3 ListObjectsV2 API call.
	 */
	public static function handle_test_connection(): void {
		self::verify_nonce( 'pr_r2_test' );
		global $as3cf;
		if ( ! $as3cf ) {
			wp_send_json_error( [ 'message' => 'WP Offload Media Lite is not active.' ] );
		}
		try {
			$provider = $as3cf->get_storage_provider();
			$client   = $provider->get_client();
			$bucket   = $as3cf->get_setting( 'bucket' );
			$client->list_objects( [ 'Bucket' => $bucket, 'MaxKeys' => 1 ] );
			wp_send_json_success( [ 'message' => "R2 connection OK — bucket '{$bucket}' is accessible." ] );
		} catch ( \Exception $e ) {
			wp_send_json_error( [ 'message' => 'Connection failed: ' . $e->getMessage() ] );
		}
	}

	// ── Clear log ──────────────────────────────────────────────────────────

	/**
	 * Truncate the wp_pr_r2_log table.
	 *
	 * POST params: nonce.
	 * Returns JSON: success { message }.
	 *
	 * Side effects: deletes all rows from wp_pr_r2_log.
	 */
	public static function handle_clear_log(): void {
		self::verify_nonce( 'pr_r2_clear_log' );
		PR_R2_Log::clear();
		wp_send_json_success( [ 'message' => 'Log cleared.' ] );
	}

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

	/**
	 * Verify nonce and capability; send JSON error and die on failure.
	 *
	 * @param  string $action  Nonce action string.
	 * @return void
	 */
	private static function verify_nonce( string $action ): void {
		if ( ! current_user_can( PR_R2_Admin_Page::CAPABILITY ) ) {
			wp_send_json_error( [ 'message' => 'Permission denied.' ], 403 );
		}
		if ( ! check_ajax_referer( $action, 'nonce', false ) ) {
			wp_send_json_error( [ 'message' => 'Invalid or expired nonce.' ], 403 );
		}
	}

	/**
	 * Return up to $limit attachment IDs with no row in as3cf_items.
	 * Always queries from the start — processed items drop out of the result set.
	 *
	 * @param  int $limit
	 * @return int[]
	 */
	private static function get_not_offloaded_ids( int $limit ): array {
		global $wpdb;
		$table = $wpdb->prefix . 'as3cf_items';
		return array_map( 'intval', $wpdb->get_col( $wpdb->prepare(
			"SELECT p.ID FROM {$wpdb->posts} p
			 LEFT JOIN {$table} oi ON oi.source_id = p.ID AND oi.source_type = 'media-library'
			 WHERE p.post_type = 'attachment' AND p.post_status = 'inherit'
			   AND oi.id IS NULL
			 LIMIT %d",
			$limit
		) ) );
	}

	/** @return int */
	private static function count_not_offloaded(): int {
		global $wpdb;
		$table = $wpdb->prefix . 'as3cf_items';
		return (int) $wpdb->get_var(
			"SELECT COUNT(p.ID) FROM {$wpdb->posts} p
			 LEFT JOIN {$table} oi ON oi.source_id = p.ID AND oi.source_type = 'media-library'
			 WHERE p.post_type = 'attachment' AND p.post_status = 'inherit'
			   AND oi.id IS NULL"
		);
	}

	/**
	 * Return up to $limit attachment IDs that are offloaded but have local copies.
	 * Checks physical disk presence — WP Offload Media does not rewrite
	 * _wp_attached_file in the DB; s3auto:// is applied at runtime via filter only.
	 *
	 * @param  int $limit
	 * @return int[]
	 */
	private static function get_local_remaining_ids( int $limit ): array {
		global $wpdb;
		$table       = $wpdb->prefix . 'as3cf_items';
		$upload_base = wp_upload_dir()['basedir'];
		$all_ids     = $wpdb->get_col(
			"SELECT DISTINCT oi.source_id FROM {$table} oi
			 INNER JOIN {$wpdb->posts} p ON p.ID = oi.source_id
			 WHERE oi.source_type = 'media-library' AND p.post_type = 'attachment'"
		);
		$result = [];
		foreach ( $all_ids as $id ) {
			if ( count( $result ) >= $limit ) {
				break;
			}
			$rel = get_post_meta( (int) $id, '_wp_attached_file', true );
			if ( $rel && file_exists( $upload_base . '/' . $rel ) ) {
				$result[] = (int) $id;
			}
		}
		return $result;
	}

	/** @return int */
	private static function count_local_remaining(): int {
		global $wpdb;
		$table       = $wpdb->prefix . 'as3cf_items';
		$upload_base = wp_upload_dir()['basedir'];
		$all_ids     = $wpdb->get_col(
			"SELECT DISTINCT oi.source_id FROM {$table} oi
			 INNER JOIN {$wpdb->posts} p ON p.ID = oi.source_id
			 WHERE oi.source_type = 'media-library' AND p.post_type = 'attachment'"
		);
		$count = 0;
		foreach ( $all_ids as $id ) {
			$rel = get_post_meta( (int) $id, '_wp_attached_file', true );
			if ( $rel && file_exists( $upload_base . '/' . $rel ) ) {
				$count++;
			}
		}
		return $count;
	}
}