namespace FileShare_Services.Core
{
    /// <summary>
    /// Matches unified endpoint patterns and extracts simple route values.
    /// </summary>
    internal static class ServiceEndpointPatternMatcher
    {
        /// <summary>
        /// Match literal segments and single-segment route parameters such as {id} or {id:int}.
        /// </summary>
        public static bool TryMatch(
            string pattern,
            string path,
            out Dictionary<string, string> routeValues)
        {
            routeValues = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);

            var patternSegments = SplitSegments(pattern);
            var pathSegments = SplitSegments(path);
            if (patternSegments.Length != pathSegments.Length)
            {
                return false;
            }

            for (var index = 0; index < patternSegments.Length; index++)
            {
                var patternSegment = patternSegments[index];
                var pathSegment = pathSegments[index];

                if (TryGetParameterName(patternSegment, out var parameterName))
                {
                    if (!MatchesConstraint(patternSegment, pathSegment))
                    {
                        return false;
                    }

                    routeValues[parameterName] = Uri.UnescapeDataString(pathSegment);
                    continue;
                }

                if (!string.Equals(patternSegment, pathSegment, StringComparison.OrdinalIgnoreCase))
                {
                    return false;
                }
            }

            return true;
        }

        /// <summary>
        /// 将路径按 <c>/</c> 拆分为非空片段数组。
        /// </summary>
        /// <param name="value">路径字符串。</param>
        /// <returns>过滤空条目后的片段数组。</returns>
        private static string[] SplitSegments(string value)
        {
            return value.Split('/', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
        }

        /// <summary>
        /// 尝试从 <c>{name}</c> 或 <c>{name:constraint}</c> 格式的片段中提取参数名称。
        /// </summary>
        /// <param name="segment">模式片段。</param>
        /// <param name="parameterName">提取出的参数名称。</param>
        /// <returns>该片段是路由参数时返回 true，否则 false。</returns>
        private static bool TryGetParameterName(string segment, out string parameterName)
        {
            parameterName = string.Empty;
            if (segment.Length < 3 || segment[0] != '{' || segment[^1] != '}')
            {
                return false;
            }

            var token = segment[1..^1];
            var constraintIndex = token.IndexOf(':');
            parameterName = constraintIndex >= 0 ? token[..constraintIndex] : token;
            return !string.IsNullOrWhiteSpace(parameterName);
        }

        /// <summary>
        /// 检查路由值是否满足片段中的类型约束（目前仅支持 <c>:int</c>）。
        /// </summary>
        /// <param name="segment">包含约束的模式片段。</param>
        /// <param name="value">实际路径值。</param>
        /// <returns>满足约束时返回 true。</returns>
        private static bool MatchesConstraint(string segment, string value)
        {
            return !segment.EndsWith(":int}", StringComparison.OrdinalIgnoreCase)
                || int.TryParse(value, out _);
        }
    }
}