namespace Usm {

    public class Version {
        public int[] version_nums { get; set; }
        public int? release { get; set; }

        public Version.from_string(string ver) throws ManifestError {
            var ver_rel = ver.chomp().chug().split("+", 2);
            if(ver_rel.length == 2) {
                var release = 0;
                if(!int.try_parse(ver_rel[1], out release)) {
                    throw new ManifestError.INVALID_VERSION("Could not parse release number");
                }
                this.release = release;
            }


            if(ver_rel[0].length == 0) {
                if(this.release == null) {
                    throw new ManifestError.INVALID_VERSION("Version string must have a version number or release number at minimum");
                }
                return;
            }

            var version_strs = ver_rel[0].split(".");
            version_nums = new int[version_strs.length];
            for(int i = 0; i < version_nums.length; i++) {
                var num = 0;
                if(!int.try_parse(version_strs[i], out num)) {
                    throw new ManifestError.INVALID_VERSION(@"Could not parse version number part $i");
                }
                version_nums[i] = num;
            }
        }

        public string to_string() {
            var str = "";
            bool first = true;
            foreach (var num in version_nums) {
                if(first) {
                    first = false;
                }
                else {
                    str += ".";
                }
                str += num.to_string();
            }
            if(release != null) {
                str += @"+$release";
            }
            return str;
        }

        public bool equals(Version other) {
            var parts = int.min(other.version_nums.length, version_nums.length);
            for(int i = 0; i < parts; i++) {
                if(version_nums[i] != other.version_nums[i]) {
                    return false;
                }
            }
            return release == other.release;
        }

        /**
         * Prefix-tolerant numeric equality ignoring `+release` suffixes:
         * 0.31 matches 0.31.0, and 0.31+2 matches 0.31. Resource-level
         * versions (soname tails, .pc `Version:` fields) never carry
         * packaging releases and upstreams disagree about component
         * counts, so this is the equality resource constraints use.
         */
        public bool matches_numeric(Version other) {
            var mine = version_nums ?? new int[0];
            var theirs = other.version_nums ?? new int[0];
            var parts = int.min(theirs.length, mine.length);
            for(int i = 0; i < parts; i++) {
                if(mine[i] != theirs[i]) {
                    return false;
                }
            }
            return true;
        }

        public bool greater_than(Version other) {
            var parts = int.min(other.version_nums.length, version_nums.length);
            for(int i = 0; i < parts; i++) {
                if(version_nums[i] > other.version_nums[i]) {
                    return true;
                }
                if(version_nums[i] < other.version_nums[i]) {
                    return false;
                }
            }
            // So far, equal
            if(release == null && other.release == null) {
                return false;
            }
            if(release == null && other.release != null) {
                return false;
            }
            if(release != null && other.release == null) {
                return true;
            }
            return release > other.release;
        }

        public bool less_than(Version other) {
            var parts = int.min(other.version_nums.length, version_nums.length);
            for(int i = 0; i < parts; i++) {
                if(version_nums[i] < other.version_nums[i]) {
                    return true;
                }
                if(version_nums[i] > other.version_nums[i]) {
                    return false;
                }
            }
            // So far, equal
            if(release == null && other.release == null) {
                return false;
            }
            if(release == null && other.release != null) {
                return true;
            }
            if(release != null && other.release == null) {
                return false;
            }
            return release < other.release;
        }

        public int compare(Version other) {
            if(less_than(other)) {
                return -1;
            }
            if(greater_than(other)) {
                return 1;
            }
            return 0;
        }
    }
}