<?php
namespace AfFulltext;

/**
 * Loads ftr-site-config rule files and resolves the one that applies to a host.
 *
 * Two directories are searched, custom first: user rules written by the prefs UI
 * override the community set, and both use the same on-disk format so a rule
 * refined here can be sent upstream to fivefilters/ftr-site-config as-is.
 */
final class RuleSet {
	/** @var string[] directories searched in order (custom before standard) */
	private array $dirs;

	/** @var array<string,?Rule> */
	private array $cache = [];

	/** @param string[] $dirs */
	public function __construct(array $dirs) {
		$this->dirs = array_values(array_filter($dirs, 'is_dir'));
	}

	/**
	 * Resolve the rule for a hostname, or null if nothing matches.
	 *
	 * Order follows Full-Text RSS: exact host, then the same host without a
	 * leading "www.", then a wildcard file (".example.com.txt") for each parent
	 * domain. global.txt is merged underneath whatever matched, so its shared
	 * strip rules apply everywhere.
	 */
	public function find(string $host): ?Rule {
		$host = strtolower(trim($host));
		if ($host === '') return null;

		if (array_key_exists($host, $this->cache))
			return $this->cache[$host];

		$rule = null;

		foreach ($this->candidates($host) as $name) {
			if ($found = $this->load($name)) { $rule = $found; break; }
		}

		if ($global = $this->load('global')) {
			$rule = $rule ? $rule->merge_under($global) : $global;
		}

		return $this->cache[$host] = $rule;
	}

	/** Filenames to try, nearest match first. @return string[] */
	public function candidates(string $host): array {
		$out = [$host];

		if (str_starts_with($host, 'www.'))
			$out[] = substr($host, 4);

		// .example.com.txt applies to every subdomain of example.com.
		$parts = explode('.', $out[count($out) - 1]);
		while (count($parts) > 1) {
			$out[] = '.' . implode('.', $parts);
			array_shift($parts);
		}

		return array_values(array_unique($out));
	}

	/** Load one rule by bare name (no .txt), searching custom then standard. */
	public function load(string $name): ?Rule {
		// Rule names come from feed hostnames; keep them off the filesystem.
		if ($name === '' || str_contains($name, '/') || str_contains($name, "\0") || str_contains($name, '..'))
			return null;

		foreach ($this->dirs as $dir) {
			$path = $dir . '/' . $name . '.txt';
			if (is_readable($path)) {
				$rule = self::parse((string) file_get_contents($path));
				$rule->sources[] = $path;
				return $rule;
			}
		}

		return null;
	}

	/** Parse ftr-site-config text into a Rule. */
	public static function parse(string $text): Rule {
		$rule = new Rule();

		foreach (preg_split('/\R/', $text) ?: [] as $line) {
			$line = trim($line);
			if ($line === '' || $line[0] === '#') continue;

			$pos = strpos($line, ':');
			if ($pos === false) continue;

			$key = strtolower(trim(substr($line, 0, $pos)));
			$val = trim(substr($line, $pos + 1));
			if ($val === '') continue;

			// http_header(user-agent) / wrap_in(div.foo) carry an argument.
			$arg = null;
			if (preg_match('/^([a-z_]+)\((.*)\)$/', $key, $m)) {
				$key = $m[1];
				$arg = trim($m[2]);
			}

			switch ($key) {
				case 'title':                 $rule->titles[] = $val; break;
				case 'body':                  $rule->bodies[] = $val; break;
				case 'author':                $rule->authors[] = $val; break;
				case 'date':                  $rule->dates[] = $val; break;
				case 'strip':                 $rule->strips[] = $val; break;
				case 'strip_id_or_class':     $rule->strip_id_or_class[] = $val; break;
				case 'strip_image_src':       $rule->strip_image_src[] = $val; break;
				case 'dissolve':              $rule->dissolve[] = $val; break;
				case 'single_page_link':      $rule->single_page_links[] = $val; break;
				case 'next_page_link':        $rule->next_page_links[] = $val; break;
				case 'find_string':           $rule->find_strings[] = $val; break;
				case 'replace_string':        $rule->replace_strings[] = $val; break;
				case 'test_url':              $rule->test_urls[] = $val; break;

				case 'prune':                 $rule->prune = self::truthy($val); break;
				case 'tidy':                  $rule->tidy = self::truthy($val); break;
				case 'autodetect_on_failure': $rule->autodetect_on_failure = self::truthy($val); break;

				case 'http_header':
					if ($arg !== null && $arg !== '') $rule->http_headers[strtolower($arg)] = $val;
					break;

				case 'wrap_in':
					if ($arg !== null && $arg !== '') $rule->wrap_in[$val] = $arg;
					break;

				// Deliberately ignored in v1: if_page_contains, replace_string
				// variants with regex, convert_to_format, parser, src_lazy_load_attr
				// (we resolve lazy images unconditionally -- see Html::unlazy).
				default: break;
			}
		}

		return $rule;
	}

	private static function truthy(string $v): bool {
		return in_array(strtolower($v), ['yes', 'true', '1', 'on'], true);
	}
}