using Invercargill.DataStructures;

namespace InvercargillSql {

    /**
     * Immutable representation of a parsed connection string.
     * 
     * Supports standard URI format: `scheme://[user[:password]@]host[:port]/database[?options]`
     * 
     * SQLite special cases:
     * - `sqlite:///absolute/path/to/db.sqlite` - Absolute path
     * - `sqlite://./relative/path.db` - Relative path  
     * - `sqlite::memory:` or `sqlite://:memory:` - In-memory database
     * - `sqlite:///db.sqlite?mode=ro` - With options
     */
    public class ConnectionString : Object {

        private Dictionary<string, string> _options;

        /**
         * The database scheme (e.g., "sqlite", "postgresql", "mysql").
         */
        public string scheme { get; private set; }

        /**
         * The host name or IP address. May be empty for file-based databases.
         */
        public string host { get; private set; }

        /**
         * The port number. 0 if not specified.
         */
        public uint16 port { get; private set; }

        /**
         * The database name or file path.
         */
        public string database { get; private set; }

        /**
         * The user name for authentication. May be empty.
         */
        public string user { get; private set; }

        /**
         * The password for authentication. May be empty.
         */
        public string password { get; private set; }

        /**
         * Query string options as key-value pairs.
         */
        public Dictionary<string, string> options { 
            get { return _options; }
        }

        /**
         * The original connection string.
         */
        public string original_string { get; private set; }

        /**
         * Private constructor - use parse() to create instances.
         */
        private ConnectionString() {
            _options = new Dictionary<string, string>();
        }

        /**
         * Parses a connection string into its components.
         * 
         * @param connection_string The connection string to parse
         * @return A new ConnectionString instance
         * @throws SqlError.INVALID_CONNECTION_STRING if the format is invalid
         */
        public static ConnectionString parse(string connection_string) throws SqlError {
            var cs = new ConnectionString();
            cs.original_string = connection_string;

            string remaining = connection_string.strip();

            // Extract scheme
            int scheme_end = remaining.index_of(":");
            if (scheme_end < 1) {
                throw new SqlError.INVALID_CONNECTION_STRING(
                    "Missing scheme in connection string: %s".printf(connection_string)
                );
            }

            cs.scheme = remaining.substring(0, scheme_end).down();
            remaining = remaining.substring(scheme_end);

            // Handle SQLite special cases
            if (cs.scheme == "sqlite") {
                cs.parse_sqlite(remaining);
                return cs;
            }

            // Standard URI parsing for other databases
            cs.parse_standard_uri(remaining);
            return cs;
        }

        /**
         * Parses SQLite-specific connection string formats.
         */
        private void parse_sqlite(string uri_part) throws SqlError {
            // Case 1: sqlite::memory: (no slashes)
            if (uri_part == "::memory:") {
                database = ":memory:";
                host = "";
                return;
            }

            // Case 2: sqlite://... (with slashes)
            if (!uri_part.has_prefix("://")) {
                throw new SqlError.INVALID_CONNECTION_STRING(
                    "Invalid SQLite connection string format: %s".printf(original_string)
                );
            }

            string path_part = uri_part.substring(3); // Remove "://"

            // Case 3: sqlite://:memory:
            if (path_part == ":memory:") {
                database = ":memory:";
                host = "";
                return;
            }

            // Split off query string if present
            string query_string = "";
            int query_pos = path_part.index_of("?");
            if (query_pos >= 0) {
                query_string = path_part.substring(query_pos + 1);
                path_part = path_part.substring(0, query_pos);
            }

            // For SQLite, the entire path is the database (file path)
            // The "host" portion is not used - everything after :// is the path
            host = "";
            database = path_part;

            // Parse query options
            parse_query_string(query_string);
        }

        /**
         * Parses standard URI format: //[user[:password]@]host[:port]/database[?options]
         */
        private void parse_standard_uri(string uri_part) throws SqlError {
            if (!uri_part.has_prefix("://")) {
                throw new SqlError.INVALID_CONNECTION_STRING(
                    "Invalid connection string format (expected scheme://): %s".printf(original_string)
                );
            }

            string remaining = uri_part.substring(3); // Remove "://"

            // Extract user:password@ if present
            int at_pos = remaining.index_of("@");
            if (at_pos >= 0) {
                string auth_part = remaining.substring(0, at_pos);
                remaining = remaining.substring(at_pos + 1);

                int colon_pos = auth_part.index_of(":");
                if (colon_pos >= 0) {
                    user = auth_part.substring(0, colon_pos);
                    password = auth_part.substring(colon_pos + 1);
                } else {
                    user = auth_part;
                    password = "";
                }
            } else {
                user = "";
                password = "";
            }

            // Split off query string if present
            string query_string = "";
            int query_pos = remaining.index_of("?");
            if (query_pos >= 0) {
                query_string = remaining.substring(query_pos + 1);
                remaining = remaining.substring(0, query_pos);
            }

            // Find the / that separates host:port from database
            int slash_pos = remaining.index_of("/");
            if (slash_pos < 0) {
                throw new SqlError.INVALID_CONNECTION_STRING(
                    "Missing database name in connection string: %s".printf(original_string)
                );
            }

            string host_port = remaining.substring(0, slash_pos);
            database = remaining.substring(slash_pos + 1);

            // Parse host:port
            int port_colon = host_port.last_index_of(":");
            if (port_colon >= 0) {
                // Check if it's an IPv6 address (contains brackets)
                if (host_port.contains("[") && host_port.contains("]")) {
                    // IPv6 format: [::1]:5432
                    int bracket_close = host_port.index_of("]");
                    if (bracket_close >= 0 && bracket_close + 1 < host_port.length && host_port[bracket_close + 1] == ':') {
                        host = host_port.substring(1, bracket_close - 1);
                        string port_str = host_port.substring(bracket_close + 2);
                        port = parse_port(port_str);
                    } else {
                        host = host_port.substring(1, bracket_close - 1);
                        port = 0;
                    }
                } else {
                    // IPv4 or hostname: host:port
                    host = host_port.substring(0, port_colon);
                    string port_str = host_port.substring(port_colon + 1);
                    port = parse_port(port_str);
                }
            } else {
                host = host_port;
                port = 0;
            }

            // Parse query options
            parse_query_string(query_string);
        }

        /**
         * Parses a port string into a uint16.
         */
        private uint16 parse_port(string port_str) throws SqlError {
            if (port_str.length == 0) {
                return 0;
            }

            int64 port_value = 0;
            if (!int64.try_parse(port_str, out port_value)) {
                throw new SqlError.INVALID_CONNECTION_STRING(
                    "Invalid port number: %s".printf(port_str)
                );
            }

            if (port_value < 0 || port_value > uint16.MAX) {
                throw new SqlError.INVALID_CONNECTION_STRING(
                    "Port number out of range: %s".printf(port_str)
                );
            }

            return (uint16)port_value;
        }

        /**
         * Parses query string options into the options dictionary.
         */
        private void parse_query_string(string query_string) {
            if (query_string.length == 0) {
                return;
            }

            string[] pairs = query_string.split("&");
            foreach (string pair in pairs) {
                string trimmed = pair.strip();
                if (trimmed.length == 0) {
                    continue;
                }

                int eq_pos = trimmed.index_of("=");
                if (eq_pos >= 0) {
                    string key = Uri.unescape_string(trimmed.substring(0, eq_pos)) ?? trimmed.substring(0, eq_pos);
                    string val = Uri.unescape_string(trimmed.substring(eq_pos + 1)) ?? trimmed.substring(eq_pos + 1);
                    _options[key] = val;
                } else {
                    _options[Uri.unescape_string(trimmed) ?? trimmed] = "";
                }
            }
        }

        /**
         * Gets an option value by key.
         * 
         * @param key The option key
         * @param default_value The default value if key is not found
         * @return The option value or default_value
         */
        public string? get_option(string key, string? default_value = null) {
            if (has_option(key)) {
                return _options.get(key);
            }
            return default_value;
        }

        /**
         * Checks if an option exists.
         * 
         * @param key The option key
         * @return true if the option exists
         */
        public bool has_option(string key) {
            return _options.has(key);
        }

        /**
         * Returns a string representation of this connection string.
         * Note: Password is masked for security.
         */
        public string to_safe_string() {
            var parts = new StringBuilder();
            parts.append(scheme);
            parts.append("://");

            if (user.length > 0) {
                parts.append(user);
                if (password.length > 0) {
                    parts.append(":***");
                }
                parts.append("@");
            }

            if (host.length > 0) {
                parts.append(host);
                if (port > 0) {
                    parts.append(":");
                    parts.append(port.to_string());
                }
                parts.append("/");
            }

            parts.append(database);

            return parts.str;
        }
    }
}