<?php

	include_once "$PROJECT_ROOT/languages/language_flags.php";

	/**
	 * Representation of Session Community room.
	 */
	class CommunityRoom implements JsonSerializable {
		/** @var CommunityServer $server Server this room belongs to. */
		public readonly object $server;
		/** @var ?int $active_users Number of active users in the defined period. */
		public readonly ?int $active_users;
		/** @var ?int $active_users_cutoff Period for `$active_users`, in seconds. */
		public readonly ?int $active_users_cutoff;
		/** @var string $token Room name in Community API. */
		public readonly string $token;
		/** @var ?string $name User-facing name given to Community. */
		public readonly ?string $name;
		/** @var ?string[] $admins The mixed Session IDs of public room admins. */
		public readonly ?array $admins;
		/** @var ?string[] $moderators The mixed Session IDs of public room moderators. */
		public readonly ?array $moderators;
		/** @var ?float $created UNIX timestamp of room creation, in seconds. */
		public readonly ?float $created;
		/** @var ?string $description User-facing description given to Community. */
		public readonly ?string $description;
		/** @var ?int $image_id Optional file ID for this room's icon, as served under the room files. */
		public readonly ?int $image_id;
		/** @var ?int $info_updates Monotonic integer counter that increases
		 * whenever the room's metadata changes. */
		public readonly ?int $info_updates;
		/** @var ?int $message_sequence Monotonic room post counter that
		 * increases each time a message is posted, edited, or deleted in this room. */
		public readonly ?int $message_sequence;
		/**
		 * @var ?bool $read
		 * This boolean flag indicates whether a regular user
		 * has permission to read messages in this room.
		 */
		public readonly ?bool $read;
		/**
		 * @var ?bool $upload
		 * This boolean flag indicates whether a regular user
		 * has permission to upload files to this room.
		 */
		public readonly ?bool $upload;
		/**
		 * @var ?bool $write
		 * This boolean flag indicates whether a regular user
		 * has permission to write messages to this room.
		 */
		public readonly ?bool $write;

		// Custom properties

		/**
		 * @var string $language_flag
		 * Optional Unicode emoji of region matching
		 * the primary language of this room.
		 *
		 * Custom attribute.
		 */
		public readonly ?string $language_flag;

		/**
		 * @var string[] $tags
		 * String tags applied to room by creator or submitter.
		 *
		 * Custom attribute.
		 */
		public readonly array $tags;

		private function __construct(\CommunityServer $server, array $details) {
			global $languages;

			$this->server = $server;
			$this->active_users = $details['active_users'];
			$this->active_users_cutoff = $details['active_users_cutoff'];
			$this->name = $details['name'];
			$this->token = $details['token'];
			$this->admins = $details['admins'];
			$this->moderators = $details['moderators'];
			$this->created = $details['created'];
			$this->description = $details['description'] ?? "";
			$this->image_id = $details['image_id'];
			$this->info_updates = $details['info_updates'];
			$this->message_sequence = $details['message_sequence'];
			$this->read = $details['read'];
			$this->write = $details['write'];
			$this->upload = $details['upload'];

			$room_identifier = $this->get_room_identifier();

			/** @var string[] */
			$this->tags = isset($details['tags'])
				? $details['tags']
				: [];

			$this->language_flag =
				isset($languages[$room_identifier])
				? $languages[$room_identifier]
				: "";
		}

		/**
		 * Return information for JSON serialization.
		 */
		function jsonSerialize(): array {
			$details = get_object_vars($this);
			unset($details['server']);
			return $details;
		}

		/**
		 * Create a CommunityRoom instance from loaded data.
		 * @param CommunityServer $server
		 */
		public static function from_details($server, array $details) {
			return new CommunityRoom($server, $details);
		}

		/**
		 * Create an array of CommunityRoom instances from loaded data.
		 * @param array[] $details
		 * @return CommunityRoom[]
		 */
		public static function from_details_array($server, array $details) {
			return array_map(function($room_data) use ($server) {
				return CommunityRoom::from_details($server, $room_data);
			}, $details);
		}

		/**
		 * Returns array of staff Session IDs.
		 * @return string[]
		 */
		function get_staff() {
			return array_unique(
				[...$this->admins, ...$this->moderators]
			);
		}

		/**
		 * Returns seconds elapsed since room was created.
		 */
		function get_age(): float {
			return time() - $this->created;
		}

		/**
		 * Return the browser preview URL for this room.
		 */
		function get_preview_url(): string {
			$base_url = $this->server->base_url;
			$token = $this->token;
			return "$base_url/r/$token";
		}

		/**
		 * Return the QR code invite URL for this room.
		 */
		function get_invite_url(): string {
			$base_url = $this->server->base_url;
			$token = $this->token;
			return "$base_url/r/$token/invite.png";
		}

		/**
		 * Return the in-app join URL for this room.
		 */
		function get_join_url(): string {
			$base_url = $this->server->base_url;
			$pubkey = $this->server->pubkey;
			$token = $this->token;
			return "$base_url/$token?public_key=$pubkey";
		}

		/**
		 * Return the URL of this room's designated icon.
		 */
		function get_icon_url(): string | bool {
			$image_id = $this->image_id;

			if ($image_id == null)
				return false;

			$base_url = $this->server->base_url;
			$token = $this->token;

			return "$base_url/room/$token/file/$image_id";
		}

		/**
		 * Return our format of room identifier.
		 * @return string String in the form `token+pubkey[:4]`.
		 */
		function get_room_identifier(): string {
			$token = $this->token;
			$pubkey_4 = substr($this->server->pubkey, 0, 4);
			return "$token+$pubkey_4";
		}
	}

	/**
	 * Class representing Session Community server hosting Community rooms.
	 */
	class CommunityServer implements JsonSerializable {
		/** @var string $base_url The root URL of this server. */
		public string $base_url = "";
		/** @var string $pubkey The SOGS protocol pubkey of this server. */
		public string $pubkey = "";
		/** @var ?\CommunityRoom[] Array of rooms hosted by this server. */
		public ?array $rooms = null;
		/**
		 * @var string[] $room_hints
		 * This array contains fallback room tokens collected from links.
		 * Used only if fetching rooms list fails.
		 */
		private array $room_hints = [];

		private function __construct() {}

		/**
		 * Compare two CommunityServer instances by base URL.
		 * @param CommunityServer $a First server to compare URLs.
		 * @param CommunityServer $b Second server to compare URLs.
		 * @return int A number less than, equal to, or greater than zero
		 * when the servers are in correct order, interchangable, or in reverse order,
		 * respectively.
		 */
		static function compare_by_url($a, $b): int {
			return strcmp(
				$a->get_hostname(),
				$b->get_hostname()
			);
		}

		/**
		 * Sort an array of servers in place based on URL.
		 * @param CommunityServer[] &$servers
		 */
		static function sort_by_url(array &$servers) {
			usort($servers, 'CommunityServer::compare_by_url');
		}

		/**
		 * Compare two CommunityServer instances by public key.
		 * @param CommunityServer $a First server to compare public keys.
		 * @param CommunityServer $b Second server to compare public keys.
		 * @return int A number less than, equal to, or greater than zero
		 * when the servers are in correct order, interchangable, or in reverse order,
		 * respectively.
		 */
		static function compare_by_pubkey($a, $b): int {
			return strcmp($a->pubkey, $b->pubkey);
		}

		/**
		 * Sorts an array of servers in place by public key.
		 * @param CommunityServer[] $servers
		 */
		public static function sort_by_pubkey(&$servers) {
			usort($servers, 'CommunityServer::compare_by_pubkey');
		}

		/**
		 * Absorbs extra info from another instance of the same server.
		 * @param CommunityServer $server
		 */
		private function merge_from($server) {
			// Merge room hint information.
			$this->room_hints = [
				...$this->room_hints,
				...$server->room_hints
			];

			// Merge public key information.
			if (!$this->has_pubkey() && $server->has_pubkey()) {
				$this->pubkey = $server->pubkey;
			}

			// Prefer HTTPS URLs over HTTP.
			if (str_starts_with($server->base_url, "https:")) {
				$this->base_url = $server->get_scheme() . "://" . $this->get_hostname();
			}

			// Prefer domain names over IPs (connections to SOGS survive relocation).
			if (filter_var($this->get_hostname(), FILTER_VALIDATE_IP)) {
				$this->base_url = $this->get_scheme() . "://" . $server->get_hostname();
			}
		}

		/**
		 * Re-introduces the server to a consistent state after merging.
		 */
		private function merge_consistency() {
			// Remove duplicate room hints; does not require sorting.
			$this->room_hints = array_unique($this->room_hints);
		}

		/**
		 * Merges consecutive servers in array in place on equality of given attribute.
		 * @param CommunityServer[] $servers Servers sorted by given attribute.
		 * @param string $method Method name to retrieve attribute from server.
		 */
		private static function merge_by(&$servers, string $method) {
			// Backwards-merging to preserve indexing for unprocessed servers.
			// Merging only makes sense for pairs, so stop at $i = 1.
			for ($i = count($servers) - 1; $i >= 1; $i--) {
				if ($servers[$i]->$method() == $servers[$i - 1]->$method()) {
					// Merge this server into the previous one, discarding it.
					$servers[$i - 1]->merge_from($servers[$i]);
					array_splice($servers, $i, 1);
				}
			}
		}

		/**
		 * Write details about this server to debug log.
		 */
		private function log_details() {
			$base_url = $this->base_url;
			$count_rooms = count($this->rooms ?? []);
			$count_room_hints = count($this->room_hints);
			$pubkey = $this->pubkey ? truncate($this->pubkey, 4) : "unknown";
			log_debug("Server $base_url"."[$count_rooms/$count_room_hints] { pubkey: $pubkey }");
		}

		/**
		 * Filters the given servers to remove URL duplicates.
		 * @param CommunityServer[] $servers Servers to merge by URL.
		 * @return CommunityServer[] Merged URL-unique servers.
		 */
		public static function dedupe_by_url($servers) {
			CommunityServer::sort_by_url($servers);

			CommunityServer::merge_by($servers, "get_hostname");

			foreach ($servers as $server) $server->merge_consistency();

			return $servers;
		}

		/**
		 * Filters the given servers to remove pubkey duplicates.
		 * @param CommunityServer[] $servers Servers to merge by public key.
		 * @return CommunityServer[] Merged pubkey-unique servers.
		 */
		public static function dedupe_by_pubkey($servers) {
			CommunityServer::sort_by_pubkey($servers);

			CommunityServer::merge_by($servers, "get_pubkey");

			foreach ($servers as $server) $server->merge_consistency();

			return $servers;
		}

		/**
		 * Return information for JSON serialization.
		 */
		function jsonSerialize(): array {
			return get_object_vars($this);
		}

		/**
		 * Create server instances located on hardcoded hosts.
		 * @param string[] $hosts Array of base URLs for known servers.
		 * @param string[] $pubkeys
		 * Associative array from hostnames to SOGS public keys.
		 * @return CommunityServer[] Array of resulting Community servers.
		 */
		static function from_known_hosts(array $hosts, array $pubkeys) {
			$servers = [];

			foreach ($hosts as $base_url) {
				$server = new CommunityServer();

				$server->base_url = $base_url;

				$hostname = url_get_base($base_url, false);

				$server->pubkey = $pubkeys[$hostname];

				$servers[] = $server;
			}

			return $servers;
		}

		/**
		 * Create server instances from given room join URLs.
		 * Resulting servers will know of the embedded room tokens.
		 * @param string[] $join_urls Join URLs found in the wild.
		 * @return CommunityServer[] Array of resulting Community servers.
		 */
		static function from_join_urls(array $join_urls) {
			$servers = [];

			foreach ($join_urls as $join_url) {
				$server = new CommunityServer();

				$server->initialize_from_url($join_url);

				$servers[] = $server;
			}

			return $servers;
		}

		/**
		 * Create Community server instance from loaded server data.
		 * @param array $details Decoded JSON associative data about server.
		 * @return CommunityServer Server represented by given data.
		 */
		static function from_details(array $details) {
			$server = new CommunityServer();

			$server->base_url = $details['base_url'];
			$server->pubkey = $details['pubkey'];
			$server->rooms = CommunityRoom::from_details_array($server, $details['rooms']);

			return $server;
		}

		/**
		  Create Community server instance from array loaded server data.
		 * @param array $details Decoded JSON associative arrays about server.
		 * @return CommunityServer[] Servers represented by given data.
		 */
		static function from_details_array(array $details_array) {
			$servers = [];

			foreach ($details_array as $details) {
				$servers[] = CommunityServer::from_details($details);
			}

			return $servers;
		}

		/**
		 * Collect the rooms among the given Community servers.
		 * @param CommunityServer[] $servers Array of Community servers.
		 * @return CommunityRoom[]
		 * Array of all rooms contained in the given servers.
		 */
		static function enumerate_rooms($servers) {
			$rooms = [];
			foreach ($servers as $server) {
				$rooms[] = $server->rooms;
			}
			return array_merge([], ...$rooms);
		}

		/**
		 * Polls given servers for rooms and public key and saves this info.
		 * Servers will be disqualified if no rooms can be found,
		 * and/or if no public key is obtained or hardcoded.
		 * @param CommunityServer[] $servers Servers to fetch.
		 * @return CommunityServer[] Servers polled successfully.
		 */
		public static function poll_reachable(array $servers): array {
			$reachable_servers = [];

			// Synchronous for-loop for now.
			foreach ($servers as $server) {
				if (!($server->fetch_rooms())) continue;
				// Accept failures to fetch pubkey if already known.
				if (!$server->fetch_or_has_pubkey()) continue;
				$reachable_servers[] = $server;
			}

			return $reachable_servers;
		}

		/**
		 * Returns the URL scheme of this server.
		 * @return string "http" or "https".
		 */
		function get_scheme() {
			return parse_url($this->base_url, PHP_URL_SCHEME);
		}

		/**
		 * Reduces this server's base URL to HTTP.
		 */
		function downgrade_scheme() {
			$base_url = $this->base_url;
			$this->base_url = "http://" . $this->get_hostname();
			log_info("Downgrading $base_url to HTTP.");
		}

		/**
		 * Returns the hostname for this server.
		 * @return string URL with hostname and port, if applicable.
		 * Scheme not included.
		 */
		function get_hostname() {
			return url_get_base($this->base_url, include_scheme: false);
		}

		/**
		 * Returns the server's root URL.
		 * @return string URL with scheme, hostname, and port, if applicable.
		 */
		function get_base_url() {
			return $this->base_url;
		}

		/**
		 * Returns the server's public key.
		 * @return string SOGS pubkey as used in the Session protocol.
		 */
		function get_pubkey() {
			return $this->pubkey;
		}

		function set_pubkey($pubkey) {
			if ($this->has_pubkey() && $this->pubkey != $pubkey) {
				$base_url = $this->base_url;
				throw new ValueError("Pubkey mismatch for $base_url");
			}

			$this->pubkey = $pubkey;
		}

		function set_pubkey_from_url($join_url) {
			$url_components = parse_url($join_url);
			parse_str($url_components['query'], $query_components);
			$this->pubkey = $query_components['public_key'];
		}

		/**
		 * Sets base url, pubkey, and room hint from join URL.
		 */
		function initialize_from_url($join_url) {
			$this->base_url = url_get_base($join_url);
			$this->set_pubkey_from_url($join_url);
			$this->room_hints[] = url_get_token($join_url);
		}

		/**
		 * Checks whether the current server SOGS public key is initialized.
		 * @return bool False if the public key is empty, true otherwise.
		 */
		function has_pubkey(): bool {
			return $this->pubkey != "";
		}

		/**
		 * Attempts to fetch the current server's room listing.
		 * Downgrades the server's scheme to HTTP if necessary.
		 * @return array|false Associative data about rooms if successful.
		 */
		private function fetch_room_list(): array|bool {
			$base_url = $this->base_url;
			list($rooms, $downgrade) = curl_get_contents_downgrade("$base_url/rooms?all=1");
			if (!$rooms) {
				log_info("Failed fetching /rooms.");
				return false;
			}
			if ($downgrade) $this->downgrade_scheme();
			$room_data = json_decode($rooms, true);
			if ($room_data == null) {
				log_info("Failed parsing /rooms.");
				return false;
			}
			log_debug("Fetched /rooms successfully");
			return $room_data;
		}

		/**
		 * Attempts to fetch the current server's rooms using observed room names.
		 * Downgrades the server's scheme to HTTP if necessary.
		 * @return ?array Associative data about rooms if successful.
		 */
		private function fetch_room_hints(): ?array {
			$base_url = $this->base_url;

			$rooms = [];

			foreach ($this->room_hints as $token) {
				log_debug("Testing room /$token.");
				list($room_raw, $downgrade) = curl_get_contents_downgrade("$base_url/room/$token", retries: 2);
				if (!$room_raw) {
					log_info("Room /$token not reachable.");
					continue;
				}
				if ($downgrade) $this->downgrade_scheme();
				$room_data = json_decode($room_raw, true);
				if ($room_data == null) {
					if (count($rooms) == 0) {
						log_info("Room /$token not parsable.");
						break;
					} else {
						log_debug("Room /$token not parsable, continuing.");
						continue;
					}
				}
				$rooms[] = $room_data;
			}

			// Mark no rooms as failure.
			if (count($rooms) == 0) {
				log_debug("No room hints were valid.");
				return null;
			}

			return $rooms;
		}

		/**
		 * Attempt to fetch rooms for tbe current server using SOGS API.
		 *
		 * @return bool True if successful, false otherwise.
		 */
		function fetch_rooms(): bool {
			$this->log_details();
			$base_url = $this->base_url;

			// Check reachability before polling too much.
			if (count($this->room_hints) >= 2) {
				log_info("Checking reachability for $base_url first...");
				log_value($this->room_hints);
				if (!url_is_reachable($base_url)) {
					log_warning("Reachability test failed by $base_url.");
					return false;
				}
			}

			log_info("Fetching rooms for $base_url.");
			$room_data = $this->fetch_room_list();
			if (!$room_data) $room_data = $this->fetch_room_hints();
			if ($room_data == null) {
				log_warning("Could not fetch rooms for $base_url.");
				return false;
			}
			$this->rooms = CommunityRoom::from_details_array($this, $room_data);

			return true;
		}

		/**
		 * Fetch the server's SOGS public key if absent.
		 * @return bool True if pubkey is present or has been fetched, false otherwise.
		 */
		function fetch_or_has_pubkey(): bool {
			$base_url = $this->base_url;
			// Do not use 'or' here; I learned the hard way.
			$result = $this->fetch_pubkey() || $this->has_pubkey();
			if (!$result) log_warning("Failed to fetch pubkey for $base_url.");
			return $result;
		}

		/**
		 * Attempt to fetch own public key by parsing SOGS HTML preview.
		 *
		 * @return bool True if successful, false otherwise.
		 */
		function fetch_pubkey() {
			if (empty($this->rooms)) {
				log_warning("Server has no rooms to poll for public key");
				return false;
			}

			$has_pubkey = $this->has_pubkey();

			$preview_url = $this->rooms[0]->get_preview_url();

			log_info("Fetching pubkey from $preview_url");
			$room_view = curl_get_contents($preview_url, retries: $has_pubkey ? 1 : 5);

			if (!$room_view) {
				log_debug("Failed to fetch room preview from $preview_url.");
				return false;
			}

			$links = parse_join_links($room_view);

			if (!isset($links[0])) {
				log_debug("Could not locate join link in preview at $preview_url.");
				return false;
			}

			$this->set_pubkey_from_url($links[0]);

			return true;
		}
	}
?>