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// Copyright 2025 Shota FUJI
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0

namespace Moo {
	public errordomain MetadataParseError {
		NOT_A_MOO_MESSAGE,
		UNSUPPORTED_VERSION,
		UNSUPPORTED_SERVICE_NAME,
	}

	private const string SIGNATURE = "MOO/";

	public class Metadata : Object {
		public uint32 version { get; construct; }
		public string verb { get; construct; }
		public string service { get; construct; }

		public int last_byte_index { get; construct; default = -1; }

		public Metadata(string verb, string service) {
			Object(version: 1, verb: verb, service: service);
		}

		public Metadata.from_string(string src) throws MetadataParseError {
			int i = 0;

			if (src.index_of(SIGNATURE) != 0) {
				throw new MetadataParseError.NOT_A_MOO_MESSAGE("Signature not found.");
			}

			i = SIGNATURE.length;

			// Parse version field
			var space_after_version = src.index_of_char(' ', i);
			if (space_after_version < 0 || space_after_version == i) {
				throw new MetadataParseError.NOT_A_MOO_MESSAGE("Missing version field.");
			}

			uint version;
			if (!uint.try_parse(src.slice((long) i, (long) space_after_version), out version, null, 10)) {
				throw new MetadataParseError.NOT_A_MOO_MESSAGE("Version is not a valid number.");
			}
			if (version == 0) {
				throw new MetadataParseError.UNSUPPORTED_VERSION("0 is not a valid version.");
			}
			if (version == 0 || version >= uint32.MAX) {
				throw new MetadataParseError.UNSUPPORTED_VERSION("Version does not fit in 32bit unsinged integer range.");
			}

			i = space_after_version + 1;

			// Parse verb (method) field
			var space_after_verb = src.index_of_char(' ', i);
			if (space_after_verb < 0 || space_after_verb == i) {
				throw new MetadataParseError.NOT_A_MOO_MESSAGE("Missing verb field.");
			}

			string verb = src.slice((long) i, (long) space_after_verb);
			foreach (var byte in verb.to_utf8()) {
				if (!byte.isupper()) {
					throw new MetadataParseError.NOT_A_MOO_MESSAGE("Verb contains non ASCII upper case letter.");
				}
			}

			i = space_after_verb + 1;

			// Parse service field
			var next_lf = src.index_of_char('\n', i);
			if (next_lf < 0 || next_lf == i) {
				throw new MetadataParseError.NOT_A_MOO_MESSAGE("Missing service field.");
			}

			string service = src.slice((long) i, (long) next_lf);
			if (!service.validate()) {
				throw new MetadataParseError.UNSUPPORTED_SERVICE_NAME("Service name is not a valid UTF8 text.");
			}

			i = next_lf + 1;

			Object(version: (uint32) version, verb: verb, service: service, last_byte_index: i);
		}

		public string to_string() {
			return "%s%u %s %s\n".printf(SIGNATURE, version, verb, service);
		}
	}
}