<?php

if (!defined('ABSPATH')) {
	exit;
}

/*
 * Streaming CSV/TXT downloads and temporary ZIP parts need native file handles
 * (fputcsv / php://output). WP_Filesystem cannot stream these the same way.
 */
// phpcs:disable WordPress.WP.AlternativeFunctions.file_system_operations_fopen
// phpcs:disable WordPress.WP.AlternativeFunctions.file_system_operations_fwrite
// phpcs:disable WordPress.WP.AlternativeFunctions.file_system_operations_fclose
// phpcs:disable WordPress.WP.AlternativeFunctions.file_system_operations_fread

final class LeExport_Exporter {
	/**
	 * @param array $settings leexport_get_settings()
	 * @return array{headers: string[], cols: string[]}
	 */
	private static function get_export_schema(array $settings): array {
		$fields = isset($settings['fields']) && is_array($settings['fields']) ? $settings['fields'] : [];

		$enabled = static function (string $key) use ($fields): bool {
			return !empty($fields[$key]);
		};

		$headers = [];
		$cols = [];

		$add = static function (string $key, string $label) use (&$headers, &$cols, $enabled): void {
			if ($enabled($key)) {
				$headers[] = $label;
				$cols[] = $key;
			}
		};

		$add('id', __('ID', 'leexport'));
		$add('title', __('Title', 'leexport'));
		$add('url', __('URL', 'leexport'));
		$add('categories', __('Categories (names)', 'leexport'));
		$add('category_urls', __('Category URLs', 'leexport'));
		$add('tags', __('Tags (names)', 'leexport'));
		$add('tag_urls', __('Tag URLs', 'leexport'));

		$topic_taxonomy = leexport_resolve_topic_taxonomy($settings);
		if ($topic_taxonomy !== '') {
			$topic_label = leexport_get_topic_taxonomy_options()[$topic_taxonomy] ?? __('Topics', 'leexport');
			$add('topics', sprintf(
				/* translators: %s: topic taxonomy label, e.g. 专题 */
				__('%s (names)', 'leexport'),
				$topic_label
			));
			$add('topic_urls', sprintf(
				/* translators: %s: topic taxonomy label */
				__('%s URLs', 'leexport'),
				$topic_label
			));
		}

		$add('published_date', __('Published Date', 'leexport'));

		return [
			'headers' => $headers,
			'cols' => $cols,
		];
	}

	public static function count_published_posts(array $settings): int {
		$q = new WP_Query(self::export_query($settings, [
			'posts_per_page' => 1,
			'fields' => 'ids',
			'no_found_rows' => false,
			'update_post_meta_cache' => false,
			'update_post_term_cache' => false,
		]));

		return (int)$q->found_posts;
	}

	/**
	 * @param array $settings leexport_get_settings()
	 */
	private static function export_query(array $settings, array $overrides = []): array {
		return leexport_build_export_query_args($settings, $overrides);
	}

	/**
	 * @param string[] $cols
	 * @return string[]
	 */
	private static function build_post_row(WP_Post $post, array $cols, string $date_format, array $settings = []): array {
		$cats = [];
		$cat_urls = [];
		$tags = [];
		$tag_urls = [];
		$topics = [];
		$topic_urls = [];
		$topic_taxonomy = leexport_resolve_topic_taxonomy($settings);

		if (in_array('categories', $cols, true) || in_array('category_urls', $cols, true)) {
			$terms = get_the_terms($post, 'category');
			if (is_array($terms)) {
				foreach ($terms as $t) {
					$cats[] = $t->name;
					$link = get_term_link($t);
					$cat_urls[] = is_wp_error($link) ? '' : (string)$link;
				}
			}
		}

		if (in_array('tags', $cols, true) || in_array('tag_urls', $cols, true)) {
			$terms = get_the_terms($post, 'post_tag');
			if (is_array($terms)) {
				foreach ($terms as $t) {
					$tags[] = $t->name;
					$link = get_term_link($t);
					$tag_urls[] = is_wp_error($link) ? '' : (string)$link;
				}
			}
		}

		if ($topic_taxonomy !== '' && (in_array('topics', $cols, true) || in_array('topic_urls', $cols, true))) {
			$terms = get_the_terms($post, $topic_taxonomy);
			if (is_array($terms)) {
				foreach ($terms as $t) {
					$topics[] = $t->name;
					$link = get_term_link($t);
					$topic_urls[] = is_wp_error($link) ? '' : (string)$link;
				}
			}
		}

		$row = [];
		foreach ($cols as $col) {
			switch ($col) {
				case 'id':
					$row[] = (string)$post->ID;
					break;
				case 'title':
					$row[] = html_entity_decode(get_the_title($post), ENT_QUOTES, get_bloginfo('charset') ?: 'UTF-8');
					break;
				case 'url':
					$row[] = (string)get_permalink($post);
					break;
				case 'categories':
					$row[] = implode(' | ', array_filter($cats, static fn($v) => $v !== ''));
					break;
				case 'category_urls':
					$row[] = implode(' | ', array_filter($cat_urls, static fn($v) => $v !== ''));
					break;
				case 'tags':
					$row[] = implode(' | ', array_filter($tags, static fn($v) => $v !== ''));
					break;
				case 'tag_urls':
					$row[] = implode(' | ', array_filter($tag_urls, static fn($v) => $v !== ''));
					break;
				case 'topics':
					$row[] = implode(' | ', array_filter($topics, static fn($v) => $v !== ''));
					break;
				case 'topic_urls':
					$row[] = implode(' | ', array_filter($topic_urls, static fn($v) => $v !== ''));
					break;
				case 'published_date':
					$row[] = (string)get_the_date($date_format, $post);
					break;
				default:
					$row[] = '';
					break;
			}
		}

		return $row;
	}

	/**
	 * @param array $settings leexport_get_settings()
	 */
	public static function output_posts_csv_download(array $settings, string $basename): void {
		$split_rows = leexport_split_rows_limit($settings);
		$total = self::count_published_posts($settings);

		if ($split_rows > 0 && $total > $split_rows) {
			self::output_posts_csv_split_zip($settings, $basename, $split_rows);
			return;
		}

		self::stream_posts_csv($settings, $basename . '.csv', 'php://output');
	}

	private static function output_posts_csv_split_zip(array $settings, string $basename, int $split_rows): void {
		if (!class_exists('ZipArchive')) {
			wp_die(
				esc_html__('Split export requires the PHP Zip extension. Install php-zip, or set “Rows per file” to 0 for a single-file export.', 'leexport'),
				esc_html__('Export failed', 'leexport'),
				['response' => 500]
			);
		}

		$date_format = (string)get_option('date_format', 'Y-m-d');
		$schema = self::get_export_schema($settings);
		$headers = $schema['headers'];
		$cols = $schema['cols'];

		$parts = self::write_posts_csv_parts($settings, $cols, $date_format, $headers, $split_rows, $basename, 'csv');
		self::deliver_zip_parts($parts, $basename);
	}

	/**
	 * Stream CSV to path or php://output.
	 *
	 * @param string[] $post_types
	 */
	private static function stream_posts_csv(array $settings, string $download_name, string $target): void {
		if ($target === 'php://output' && headers_sent()) {
			return;
		}

		$date_format = (string)get_option('date_format', 'Y-m-d');
		$schema = self::get_export_schema($settings);
		$headers = $schema['headers'];
		$cols = $schema['cols'];

		if ($target === 'php://output') {
			nocache_headers();
			header('Content-Type: text/csv; charset=UTF-8');
			header('Content-Disposition: attachment; filename="' . $download_name . '"');
			header('Pragma: no-cache');
			header('Expires: 0');
		}

		$out = fopen($target, 'wb');
		if ($out === false) {
			return;
		}

		fwrite($out, "\xEF\xBB\xBF");
		fputcsv($out, $headers);

		$per_page = 500;
		$paged = 1;

		while (true) {
			$q = new WP_Query(self::export_query($settings, [
				'posts_per_page' => $per_page,
				'paged' => $paged,
				'no_found_rows' => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => true,
			]));

			if (empty($q->posts)) {
				break;
			}

			foreach ($q->posts as $post) {
				/** @var WP_Post $post */
				fputcsv($out, self::build_post_row($post, $cols, $date_format, $settings));
			}

			wp_reset_postdata();

			if ($target === 'php://output' && function_exists('flush')) {
				flush();
			}

			$paged++;
		}

		fclose($out);
	}

	/**
	 * @param array $settings leexport_get_settings()
	 * @param string[] $cols
	 * @param string[] $headers
	 * @return array<int, array{path:string, name:string}>
	 */
	private static function write_posts_csv_parts(
		array $settings,
		array $cols,
		string $date_format,
		array $headers,
		int $split_rows,
		string $basename,
		string $ext
	): array {
		$parts = [];
		$part_num = 0;
		$rows_in_part = 0;
		$out = null;
		$path = '';

		$open_part = static function () use (&$part_num, &$out, &$path, &$rows_in_part, $headers, $basename, $ext, &$parts): void {
			if (is_resource($out)) {
				fclose($out);
			}
			$part_num++;
			$rows_in_part = 0;
			$path = wp_tempnam($basename . '-part');
			if (!is_string($path) || $path === '') {
				return;
			}
			$out = fopen($path, 'wb');
			if ($out === false) {
				return;
			}
			fwrite($out, "\xEF\xBB\xBF");
			fputcsv($out, $headers);
			$parts[] = [
				'path' => $path,
				'name' => sprintf('%s-part%03d.%s', $basename, $part_num, $ext),
			];
		};

		$open_part();

		$per_page = 500;
		$paged = 1;

		while (true) {
			$q = new WP_Query(self::export_query($settings, [
				'posts_per_page' => $per_page,
				'paged' => $paged,
				'no_found_rows' => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => true,
			]));

			if (empty($q->posts)) {
				break;
			}

			foreach ($q->posts as $post) {
				/** @var WP_Post $post */
				if ($rows_in_part >= $split_rows) {
					$open_part();
				}
				if (!is_resource($out)) {
					break 2;
				}
				fputcsv($out, self::build_post_row($post, $cols, $date_format, $settings));
				$rows_in_part++;
			}

			wp_reset_postdata();
			$paged++;
		}

		if (is_resource($out)) {
			fclose($out);
		}

		return $parts;
	}

	/**
	 * @param array $settings leexport_get_settings()
	 */
	public static function output_url_txt_download(array $settings, string $basename): void {
		$split_rows = leexport_split_rows_limit($settings);
		$total = self::count_published_posts($settings);

		if ($split_rows > 0 && $total > $split_rows) {
			self::output_url_txt_split_zip($settings, $split_rows, $basename);
			return;
		}

		if (headers_sent()) {
			return;
		}

		nocache_headers();
		header('Content-Type: text/plain; charset=UTF-8');
		header('Content-Disposition: attachment; filename="' . $basename . '.txt"');

		self::stream_url_lines($settings, 'php://output');
		exit;
	}

	private static function output_url_txt_split_zip(array $settings, int $split_rows, string $basename): void {
		if (!class_exists('ZipArchive')) {
			wp_die(
				esc_html__('Split export requires the PHP Zip extension. Install php-zip, or set “Rows per file” to 0 for a single-file export.', 'leexport'),
				esc_html__('Export failed', 'leexport'),
				['response' => 500]
			);
		}

		$parts = self::write_url_txt_parts($settings, $split_rows, $basename);
		self::deliver_zip_parts($parts, $basename);
	}

	/**
	 * @param array $settings leexport_get_settings()
	 * @return array<int, array{path:string, name:string}>
	 */
	private static function write_url_txt_parts(array $settings, int $split_rows, string $basename): array {
		$parts = [];
		$part_num = 0;
		$rows_in_part = 0;
		$out = null;

		$open_part = static function () use (&$part_num, &$out, &$rows_in_part, $basename, &$parts): void {
			if (is_resource($out)) {
				fclose($out);
			}
			$part_num++;
			$rows_in_part = 0;
			$path = wp_tempnam($basename . '-part');
			if (!is_string($path) || $path === '') {
				return;
			}
			$out = fopen($path, 'wb');
			if ($out === false) {
				return;
			}
			$parts[] = [
				'path' => $path,
				'name' => sprintf('%s-part%03d.txt', $basename, $part_num),
			];
		};

		$open_part();

		$per_page = 1000;
		$paged = 1;

		while (true) {
			$q = new WP_Query(self::export_query($settings, [
				'fields' => 'ids',
				'posts_per_page' => $per_page,
				'paged' => $paged,
				'no_found_rows' => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => false,
			]));

			if (empty($q->posts)) {
				break;
			}

			foreach ($q->posts as $pid) {
				$u = get_permalink((int)$pid);
				if (!is_string($u)) {
					continue;
				}
				$u = trim($u);
				if ($u === '') {
					continue;
				}

				if ($rows_in_part >= $split_rows) {
					$open_part();
				}
				if (!is_resource($out)) {
					break 2;
				}

				if ($rows_in_part > 0) {
					fwrite($out, "\n");
				}
				fwrite($out, $u);
				$rows_in_part++;
			}

			$paged++;
		}

		if (is_resource($out)) {
			fclose($out);
		}

		return $parts;
	}

	/**
	 * @param array $settings leexport_get_settings()
	 */
	private static function stream_url_lines(array $settings, string $target): void {
		$per_page = 1000;
		$paged = 1;
		$first = true;

		while (true) {
			$q = new WP_Query(self::export_query($settings, [
				'fields' => 'ids',
				'posts_per_page' => $per_page,
				'paged' => $paged,
				'no_found_rows' => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => false,
			]));

			if (empty($q->posts)) {
				break;
			}

			foreach ($q->posts as $pid) {
				$u = get_permalink((int)$pid);
				if (!is_string($u)) {
					continue;
				}
				$u = trim($u);
				if ($u === '') {
					continue;
				}

				if ($target === 'php://output') {
					if (!$first) {
						echo "\n"; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Plain-text download stream.
					}
					// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Plain-text URL list download, not HTML.
					echo esc_url_raw($u);
					$first = false;
				}
			}

			if ($target === 'php://output' && function_exists('flush')) {
				flush();
			}

			$paged++;
		}
	}

	/**
	 * @param array $settings leexport_get_settings()
	 */
	public static function output_url_csv_download(array $settings, string $basename): void {
		$split_rows = leexport_split_rows_limit($settings);
		$total = self::count_published_posts($settings);

		if ($split_rows > 0 && $total > $split_rows) {
			self::output_url_csv_split_zip($settings, $split_rows, $basename);
			return;
		}

		if (headers_sent()) {
			return;
		}

		nocache_headers();
		header('Content-Type: text/csv; charset=UTF-8');
		header('Content-Disposition: attachment; filename="' . $basename . '.csv"');
		header('Pragma: no-cache');
		header('Expires: 0');

		self::stream_url_csv($settings, 'php://output');
		exit;
	}

	private static function output_url_csv_split_zip(array $settings, int $split_rows, string $basename): void {
		if (!class_exists('ZipArchive')) {
			wp_die(
				esc_html__('Split export requires the PHP Zip extension. Install php-zip, or set “Rows per file” to 0 for a single-file export.', 'leexport'),
				esc_html__('Export failed', 'leexport'),
				['response' => 500]
			);
		}

		$parts = self::write_url_csv_parts($settings, $split_rows, $basename);
		self::deliver_zip_parts($parts, $basename);
	}

	/**
	 * @param array $settings leexport_get_settings()
	 * @return array<int, array{path:string, name:string}>
	 */
	private static function write_url_csv_parts(array $settings, int $split_rows, string $basename): array {
		$parts = [];
		$part_num = 0;
		$rows_in_part = 0;
		$out = null;
		$header = [__('URL', 'leexport')];

		$open_part = static function () use (&$part_num, &$out, &$rows_in_part, $basename, &$parts, $header): void {
			if (is_resource($out)) {
				fclose($out);
			}
			$part_num++;
			$rows_in_part = 0;
			$path = wp_tempnam($basename . '-part');
			if (!is_string($path) || $path === '') {
				return;
			}
			$out = fopen($path, 'wb');
			if ($out === false) {
				return;
			}
			fwrite($out, "\xEF\xBB\xBF");
			fputcsv($out, $header);
			$parts[] = [
				'path' => $path,
				'name' => sprintf('%s-part%03d.csv', $basename, $part_num),
			];
		};

		$open_part();

		$per_page = 1000;
		$paged = 1;

		while (true) {
			$q = new WP_Query(self::export_query($settings, [
				'fields' => 'ids',
				'posts_per_page' => $per_page,
				'paged' => $paged,
				'no_found_rows' => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => false,
			]));

			if (empty($q->posts)) {
				break;
			}

			foreach ($q->posts as $pid) {
				$u = get_permalink((int)$pid);
				if (!is_string($u)) {
					continue;
				}
				$u = trim($u);
				if ($u === '') {
					continue;
				}

				if ($rows_in_part >= $split_rows) {
					$open_part();
				}
				if (!is_resource($out)) {
					break 2;
				}

				fputcsv($out, [$u]);
				$rows_in_part++;
			}

			$paged++;
		}

		if (is_resource($out)) {
			fclose($out);
		}

		return $parts;
	}

	/**
	 * @param array $settings leexport_get_settings()
	 */
	private static function stream_url_csv(array $settings, string $target): void {
		$out = fopen($target, 'wb');
		if ($out === false) {
			return;
		}

		fwrite($out, "\xEF\xBB\xBF");
		fputcsv($out, [__('URL', 'leexport')]);

		$per_page = 1000;
		$paged = 1;

		while (true) {
			$q = new WP_Query(self::export_query($settings, [
				'fields' => 'ids',
				'posts_per_page' => $per_page,
				'paged' => $paged,
				'no_found_rows' => true,
				'update_post_meta_cache' => false,
				'update_post_term_cache' => false,
			]));

			if (empty($q->posts)) {
				break;
			}

			foreach ($q->posts as $pid) {
				$u = get_permalink((int)$pid);
				if (!is_string($u)) {
					continue;
				}
				$u = trim($u);
				if ($u === '') {
					continue;
				}
				fputcsv($out, [$u]);
			}

			if ($target === 'php://output' && function_exists('flush')) {
				flush();
			}

			$paged++;
		}

		fclose($out);
	}

	/**
	 * @param array<int, string[]> $rows
	 */
	public static function output_csv_download(string $filename, array $headers, array $rows, int $split_rows = 0): void {
		if ($split_rows > 0 && count($rows) > $split_rows) {
			self::output_csv_rows_split_zip($filename, $headers, $rows, $split_rows);
			return;
		}

		if (headers_sent()) {
			return;
		}

		nocache_headers();
		header('Content-Type: text/csv; charset=UTF-8');
		header('Content-Disposition: attachment; filename="' . $filename . '"');
		header('Pragma: no-cache');
		header('Expires: 0');

		$out = fopen('php://output', 'wb');
		if ($out === false) {
			return;
		}

		fwrite($out, "\xEF\xBB\xBF");
		fputcsv($out, $headers);
		foreach ($rows as $row) {
			fputcsv($out, $row);
		}
		fclose($out);
	}

	/**
	 * @param array<int, string[]> $rows
	 * @param string[] $headers
	 */
	private static function output_csv_rows_split_zip(string $basename, array $headers, array $rows, int $split_rows): void {
		if (!class_exists('ZipArchive')) {
			wp_die(
				esc_html__('Split export requires the PHP Zip extension. Install php-zip, or set “Rows per file” to 0 for a single-file export.', 'leexport'),
				esc_html__('Export failed', 'leexport'),
				['response' => 500]
			);
		}

		$basename = preg_replace('/\.csv$/i', '', $basename) ?: $basename;
		$chunks = array_chunk($rows, $split_rows);
		$parts = [];
		$part_num = 0;

		foreach ($chunks as $chunk) {
			$part_num++;
			$path = wp_tempnam($basename . '-part');
			if (!is_string($path) || $path === '') {
				continue;
			}
			$out = fopen($path, 'wb');
			if ($out === false) {
				continue;
			}
			fwrite($out, "\xEF\xBB\xBF");
			fputcsv($out, $headers);
			foreach ($chunk as $row) {
				fputcsv($out, $row);
			}
			fclose($out);
			$parts[] = [
				'path' => $path,
				'name' => sprintf('%s-part%03d.csv', $basename, $part_num),
			];
		}

		self::deliver_zip_parts($parts, $basename);
	}

	/**
	 * @param array<int, array{path:string, name:string}> $parts
	 */
	private static function deliver_zip_parts(array $parts, string $basename): void {
		if ($parts === []) {
			wp_die(
				esc_html__('No export data found.', 'leexport'),
				esc_html__('Export failed', 'leexport'),
				['response' => 404]
			);
		}

		if (count($parts) === 1) {
			$single = $parts[0];
			$mime = substr(strtolower($single['name']), -4) === '.txt' ? 'text/plain' : 'text/csv';
			self::deliver_file($single['path'], $single['name'], $mime);
			return;
		}

		$zip_path = wp_tempnam($basename . '.zip');
		if (!is_string($zip_path) || $zip_path === '') {
			wp_die(esc_html__('Could not create export archive.', 'leexport'));
		}

		$zip = new ZipArchive();
		if ($zip->open($zip_path, ZipArchive::OVERWRITE) !== true) {
			wp_delete_file($zip_path);
			wp_die(esc_html__('Could not create export archive.', 'leexport'));
		}

		foreach ($parts as $part) {
			if (is_readable($part['path'])) {
				$zip->addFile($part['path'], $part['name']);
			}
		}
		$zip->close();

		foreach ($parts as $part) {
			wp_delete_file($part['path']);
		}

		self::deliver_file($zip_path, $basename . '.zip', 'application/zip');
	}

	private static function deliver_file(string $path, string $download_name, string $mime): void {
		if (!is_readable($path)) {
			wp_die(esc_html__('Export file is missing.', 'leexport'));
		}

		if (headers_sent()) {
			wp_delete_file($path);
			return;
		}

		$safe_name = sanitize_file_name($download_name);
		nocache_headers();
		header('Content-Type: ' . $mime . '; charset=UTF-8');
		header('Content-Disposition: attachment; filename="' . $safe_name . '"');
		header('Content-Length: ' . (string)filesize($path));
		header('Pragma: no-cache');
		header('Expires: 0');

		$fh = fopen($path, 'rb');
		if ($fh !== false) {
			while (!feof($fh)) {
				$buf = fread($fh, 1024 * 1024);
				if ($buf === false) {
					break;
				}
				// phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Binary download stream (CSV/ZIP), not HTML.
				echo $buf;
			}
			fclose($fh);
		}

		wp_delete_file($path);
		exit;
	}
}

// phpcs:enable WordPress.WP.AlternativeFunctions.file_system_operations_fopen
// phpcs:enable WordPress.WP.AlternativeFunctions.file_system_operations_fwrite
// phpcs:enable WordPress.WP.AlternativeFunctions.file_system_operations_fclose
// phpcs:enable WordPress.WP.AlternativeFunctions.file_system_operations_fread