using System.Collections.Concurrent;
using System.Text.RegularExpressions;
using dy.net.model.dto;
using dy.net.model.entity;
using SqlSugar;

namespace dy.net.service
{
    public sealed class DouyinUserLookupService
    {
        private static readonly TimeSpan CacheLifetime = TimeSpan.FromMinutes(5);
        private static readonly SemaphoreSlim SearchGate = new(1, 1);
        private static readonly ConcurrentDictionary<string, CacheEntry> Cache = new(StringComparer.Ordinal);
        private static readonly Regex LabeledDouyinNo = new(
            @"^(?:抖音号|douyin)\s*[:：]\s*([^\s，,；;]+)",
            RegexOptions.IgnoreCase | RegexOptions.Compiled);
        private static readonly Regex LabeledDouyinNoPrefix = new(
            @"^(?:抖音号|douyin)\s*[:：]",
            RegexOptions.IgnoreCase | RegexOptions.Compiled);

        private readonly ISqlSugarClient _db;
        private readonly DouyinUserSearchClient _searchClient;

        public DouyinUserLookupService(ISqlSugarClient db, DouyinUserSearchClient searchClient)
        {
            _db = db;
            _searchClient = searchClient;
        }

        public async Task<DouyinFollowLookupResult> ResolveAsync(
            DouyinFollowLookupRequest request,
            CancellationToken cancellationToken = default)
        {
            if (request == null) throw new InvalidOperationException("查询参数不能为空");
            var query = NormalizeDouyinNo(request.DouyinNo);
            if (string.IsNullOrWhiteSpace(request.CookieId)) throw new InvalidOperationException("请选择抖音授权账号");

            var cookie = await _db.Queryable<DouyinCookie>().InSingleAsync(request.CookieId);
            if (cookie == null) throw new InvalidOperationException("选择的抖音授权账号不存在");
            if (cookie.Status != 1 || cookie.StatusCode != 0 || string.IsNullOrWhiteSpace(cookie.Cookies))
                throw new InvalidOperationException("当前账号 Cookie 无效或未启用，请先更新抖音授权");
            if (string.IsNullOrWhiteSpace(cookie.MyUserId))
                throw new InvalidOperationException("当前账号缺少用户 UID，请先完善抖音授权配置");

            var cacheKey = cookie.Id + ":" + query.ToUpperInvariant();
            var candidates = TryGetCached(cacheKey);
            if (candidates == null)
            {
                await SearchGate.WaitAsync(cancellationToken);
                try
                {
                    candidates = TryGetCached(cacheKey);
                    if (candidates == null)
                    {
                        candidates = await _searchClient.SearchAsync(query, cookie.Cookies, cancellationToken);
                        Cache[cacheKey] = new CacheEntry(DateTimeOffset.UtcNow.Add(CacheLifetime), Clone(candidates));
                    }
                }
                finally
                {
                    SearchGate.Release();
                }
            }

            if (candidates.Count == 0) throw new InvalidOperationException("未找到对应博主，请检查抖音号或使用手动添加");
            var secUids = candidates.Select(x => x.SecUid).Distinct().ToList();
            var existing = await _db.Queryable<DouyinFollowed>()
                .Where(x => x.mySelfId == cookie.MyUserId && secUids.Contains(x.SecUid))
                .Select(x => x.SecUid)
                .ToListAsync();
            var existingSet = existing.ToHashSet(StringComparer.Ordinal);

            foreach (var candidate in candidates)
            {
                candidate.ExactMatch = string.Equals(candidate.UniqueId, query, StringComparison.OrdinalIgnoreCase)
                                       || string.Equals(candidate.ShortId, query, StringComparison.OrdinalIgnoreCase);
                candidate.AlreadyExists = existingSet.Contains(candidate.SecUid);
            }

            return new DouyinFollowLookupResult
            {
                Query = query,
                Candidates = candidates
                    .OrderByDescending(x => x.ExactMatch)
                    .ThenByDescending(x => x.FollowerCount)
                    .Take(10)
                    .ToList()
            };
        }

        public static string NormalizeDouyinNo(string input)
        {
            var value = (input ?? string.Empty).Trim();
            var match = LabeledDouyinNo.Match(value);
            if (match.Success)
                value = match.Groups[1].Value;
            else if (LabeledDouyinNoPrefix.IsMatch(value))
                value = string.Empty;
            value = value.Trim().TrimStart('@').Trim();
            if (string.IsNullOrWhiteSpace(value)) throw new InvalidOperationException("请输入抖音号");
            if (value.Length > 64) throw new InvalidOperationException("抖音号长度不能超过 64 个字符");
            if (value.Any(char.IsWhiteSpace) || value.Any(char.IsControl))
                throw new InvalidOperationException("抖音号格式不正确");
            return value;
        }

        private static List<DouyinFollowCandidate> TryGetCached(string key)
        {
            if (!Cache.TryGetValue(key, out var entry)) return null;
            if (entry.ExpiresAt <= DateTimeOffset.UtcNow)
            {
                Cache.TryRemove(key, out _);
                return null;
            }
            return Clone(entry.Candidates);
        }

        private static List<DouyinFollowCandidate> Clone(IEnumerable<DouyinFollowCandidate> source) =>
            source.Select(x => new DouyinFollowCandidate
            {
                SecUid = x.SecUid,
                UperId = x.UperId,
                DouyinNo = x.DouyinNo,
                UniqueId = x.UniqueId,
                ShortId = x.ShortId,
                UperName = x.UperName,
                UperAvatar = x.UperAvatar,
                Signature = x.Signature,
                Enterprise = x.Enterprise,
                FollowerCount = x.FollowerCount,
                ExactMatch = x.ExactMatch,
                AlreadyExists = x.AlreadyExists
            }).ToList();

        private sealed record CacheEntry(DateTimeOffset ExpiresAt, List<DouyinFollowCandidate> Candidates);
    }
}