using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using DouyinApi.IServices;
using DouyinApi.Model.Naming;

namespace DouyinApi.Services
{
    public class NamingService : INamingService
    {
        private static readonly Regex SurnameRegex = new(@"^[\u4e00-\u9fa5]{1,2}$", RegexOptions.Compiled);

        private static readonly IReadOnlyList<char> MaleCharacters = new[]
        {
            '辰', '昇', '曜', '瀚', '宸', '沐', '景', '霖', '晟', '玥', '骁', '煜', '澜', '珩', '聿', '澄', '钧'
        };

        private static readonly IReadOnlyList<char> FemaleCharacters = new[]
        {
            '瑶', '霏', '婉', '绮', '璇', '芷', '乂', '灵', '沁', '语', '晴', '若', '绫', '芸', '络', '梦', '澜'
        };

        private static readonly IReadOnlyList<char> NeutralCharacters = new[]
        {
            '玄', '洛', '岚', '澈', '岑', '泓', '澜', '烨', '闻', '黎', '墨', '夙', '羲', '霆', '渊', '翎'
        };

        private static readonly Dictionary<char, string> CharacterMeanings = new()
        {
            ['辰'] = "辰曜星光",
            ['昇'] = "旭日东升",
            ['曜'] = "光耀万里",
            ['瀚'] = "瀚海无垠",
            ['宸'] = "王者气度",
            ['沐'] = "沐浴祥瑞",
            ['景'] = "景行德高",
            ['霖'] = "甘霖润泽",
            ['晟'] = "光明昌盛",
            ['玥'] = "王者之玉",
            ['骁'] = "英勇不屈",
            ['煜'] = "照耀四方",
            ['澜'] = "碧波浩渺",
            ['珩'] = "璞玉内敛",
            ['聿'] = "持守正道",
            ['澄'] = "心境澄明",
            ['钧'] = "乾坤平衡",
            ['瑶'] = "瑶光琼华",
            ['霏'] = "霏霏瑞雪",
            ['婉'] = "柔婉清扬",
            ['绮'] = "绮丽灵动",
            ['璇'] = "璇玑回转",
            ['芷'] = "香草高洁",
            ['乂'] = "安然有序",
            ['灵'] = "灵秀夺目",
            ['沁'] = "沁心甘露",
            ['语'] = "言语有光",
            ['晴'] = "晴空暖阳",
            ['若'] = "若水明澈",
            ['绫'] = "绫罗轻盈",
            ['芸'] = "芸芸芳草",
            ['络'] = "络绎华彩",
            ['梦'] = "梦想成真",
            ['玄'] = "玄妙莫测",
            ['洛'] = "洛水灵韵",
            ['岚'] = "山岚清气",
            ['澈'] = "心境通透",
            ['岑'] = "峻岭深沉",
            ['泓'] = "泓泉清澈",
            ['烨'] = "火光通明",
            ['闻'] = "名闻四海",
            ['黎'] = "黎明曙光",
            ['墨'] = "墨香书韵",
            ['夙'] = "夙愿成真",
            ['羲'] = "伏羲灵息",
            ['霆'] = "雷霆万钧",
            ['渊'] = "渊源深厚",
            ['翎'] = "翎羽轻灵"
        };

        private static readonly string[] Blessings =
        {
            "引瑞气入怀，扶摇直上",
            "承先祖之德，守家风之和",
            "与四时共鸣，步步生辉",
            "纳天地灵气，行稳致远",
            "凝万象之精魄，护佑昌隆",
            "藏锋于怀，静待时来",
            "兼济天下情怀，拥抱广阔未来"
        };

        public Task<bool> ValidateSurnameAsync(string surname)
        {
            if (string.IsNullOrWhiteSpace(surname))
            {
                return Task.FromResult(false);
            }

            return Task.FromResult(SurnameRegex.IsMatch(surname.Trim()));
        }

        public async Task<NamingResponse> GenerateNamesAsync(NamingRequest request)
        {
            if (request == null)
            {
                throw new ArgumentNullException(nameof(request));
            }

            if (!await ValidateSurnameAsync(request.Surname))
            {
                throw new ArgumentException("invalid_surname");
            }

            var seed = CreateSeed(request);
            var random = new Random(seed);
            var pool = request.Gender == "female" ? FemaleCharacters : MaleCharacters;
            var fallbackPool = NeutralCharacters;

            var suggestions = new List<NamingSuggestion>();
            var attempts = 0;

            while (suggestions.Count < 5 && attempts < 100)
            {
                attempts++;
                var given = GenerateGivenName(request.NameLength, pool, fallbackPool, random);
                var fullName = $"{request.Surname}{given}";
                if (suggestions.Any(s => s.Name == fullName))
                {
                    continue;
                }

                var meaning = ComposeMeaning(request.Surname, given, request.BirthDate, request.BirthTime, random);
                suggestions.Add(new NamingSuggestion
                {
                    Name = fullName,
                    Meaning = meaning
                });
            }

            if (!suggestions.Any())
            {
                suggestions.Add(new NamingSuggestion
                {
                    Name = $"{request.Surname}玄珏",
                    Meaning = "玄珠映月，珏石生辉，与生辰相应，寓意行稳致远"
                });
            }

            return new NamingResponse
            {
                Results = suggestions
            };
        }

        private static int CreateSeed(NamingRequest request)
        {
            var raw = $"{request.Surname}-{request.Gender}-{request.BirthDate}-{request.BirthTime}-{request.NameLength}";
            var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(raw));
            return Math.Abs(BitConverter.ToInt32(bytes, 0));
        }

        private static string GenerateGivenName(
            string nameLength,
            IReadOnlyList<char> primaryPool,
            IReadOnlyList<char> fallbackPool,
            Random random)
        {
            var buffer = new StringBuilder();
            var length = nameLength == "single" ? 1 : 2;
            for (var i = 0; i < length; i++)
            {
                var pool = (i == 0) ? primaryPool : fallbackPool;
                buffer.Append(pool[random.Next(pool.Count)]);
            }
            return buffer.ToString();
        }

        private static string ComposeMeaning(string surname, string given, string birthDate, string birthTime, Random random)
        {
            var fragments = new List<string>();
            foreach (var ch in given)
            {
                if (CharacterMeanings.TryGetValue(ch, out var desc))
                {
                    fragments.Add(desc);
                }
                else
                {
                    fragments.Add($"{ch}寓意祥瑞");
                }
            }

            var blessing = Blessings[random.Next(Blessings.Length)];
            var birthFragment = string.IsNullOrWhiteSpace(birthTime)
                ? $"{birthDate}之辰"
                : $"{birthDate} {birthTime} 时刻";

            return $"{string.Join("，", fragments)}，与{surname}氏气脉相连，于{birthFragment}呼应，{blessing}。";
        }
    }
}