namespace RuleEngine.Patterns;

using RuleEngine.Core;

public class FanConfig
{
    public string Name { get; set; } = "";
    public int BaseFan { get; set; }
    public int Level { get; set; }
    public List<string> Excludes { get; set; } = new();
    public List<string> Conflicts { get; set; } = new();
}

public class MeldsSolver
{
    private readonly Dictionary<string, FanConfig> _fanConfig;

    public MeldsSolver(Dictionary<string, FanConfig> fanConfig)
    {
        _fanConfig = fanConfig;
    }

    // === 主入口 ===
    public MeldsResult CheckWin(List<int> hand, int? newTile = null,
        int wildcardCount = 0, bool require258Pair = false)
    {
        var tiles = new List<int>(hand);
        if (newTile.HasValue) tiles.Add(newTile.Value);
        if (tiles.Count + wildcardCount != 14) return new MeldsResult { IsWin = false };

        tiles.Sort();

        // 1. 七对 (wildcards can pair)
        var sevenPairs = TrySevenPairs(tiles, wildcardCount);
        if (sevenPairs != null)
        {
            sevenPairs.Fans = IdentifyFans(sevenPairs);
            return sevenPairs;
        }

        // 2. 十三幺
        var thirteen = TryThirteenOrphans(tiles, wildcardCount);
        if (thirteen != null)
        {
            thirteen.Fans = IdentifyFans(thirteen);
            return thirteen;
        }

        // 3. 全不靠
        var allOrphans = TryAllOrphans(tiles, wildcardCount);
        if (allOrphans != null)
        {
            allOrphans.Fans = IdentifyFans(allOrphans);
            return allOrphans;
        }

        // 4. 一色双龙会
        var doubleDragon = TryDoubleDragon(tiles, wildcardCount);
        if (doubleDragon != null)
        {
            doubleDragon.Fans = IdentifyFans(doubleDragon);
            return doubleDragon;
        }

        // 5. 标准回溯（含 wildcard 缺口填充）
        var counts = BuildCounts(tiles);
        var result = TryExtractMelds(counts, wildcardCount, 0);
        if (result != null)
        {
            // 258将检查
            if (require258Pair && result.PairTiles.Count == 2)
            {
                if (!IsValid258Pair(result.PairTiles[0], result.PairTiles[1]))
                    return new MeldsResult { IsWin = false };
            }
            result.Fans = IdentifyFans(result);
            return result;
        }

        return new MeldsResult { IsWin = false };
    }

    // === Counts array helper ===
    private int[] BuildCounts(List<int> tiles)
    {
        // Index: 万1-9→0-8, 条1-9→9-17, 筒1-9→18-26,
        // 字31-37→27-33, 花/宝牌不进counts
        var counts = new int[34];
        foreach (var t in tiles)
        {
            if (MahjongTile.IsWildcard(t) || MahjongTile.IsFlower(t)) continue;
            int idx = TileToIndex(t);
            if (idx >= 0 && idx < 34)
                counts[idx]++;
        }
        return counts;
    }

    private int TileToIndex(int tile)
    {
        if (tile >= 1 && tile <= 9) return tile - 1;
        if (tile >= 11 && tile <= 19) return 9 + (tile - 11);
        if (tile >= 21 && tile <= 29) return 18 + (tile - 21);
        if (tile >= 31 && tile <= 37) return 27 + (tile - 31);
        return -1;
    }

    private int IndexToTile(int idx)
    {
        if (idx < 9) return idx + 1;
        if (idx < 18) return 11 + (idx - 9);
        if (idx < 27) return 21 + (idx - 18);
        if (idx < 34) return 31 + (idx - 27);
        return -1;
    }

    // === 标准回溯（基础版，无 wildcard） ===
    private MeldsResult? TryExtractMelds(int[] counts, int wildcardCount, int pairCount)
    {
        // Find first non-zero
        int i = 0;
        while (i < counts.Length && counts[i] == 0) i++;

        if (i == counts.Length)
        {
            // All non-wildcard tiles consumed
            return FinalizeWithWildcards(wildcardCount, pairCount);
        }

        int tile = IndexToTile(i);

        // Try kezi (triplet)
        if (counts[i] >= 3)
        {
            counts[i] -= 3;
            var r = TryExtractMelds(counts, wildcardCount, pairCount);
            if (r != null)
            {
                counts[i] += 3;
                r.Melds.Insert(0, new Meld { Type = "kezi", Tiles = new List<int> { tile, tile, tile } });
                return r;
            }
            counts[i] += 3;
        }

        // Try shunzi (sequence) - only for numbered tiles
        if (IsNumberedIndex(i) && i + 2 < 27 && SameSuitGroup(i, i + 2))
        {
            if (counts[i] >= 1 && counts[i + 1] >= 1 && counts[i + 2] >= 1)
            {
                counts[i]--; counts[i + 1]--; counts[i + 2]--;
                var r = TryExtractMelds(counts, wildcardCount, pairCount);
                if (r != null)
                {
                    counts[i]++; counts[i + 1]++; counts[i + 2]++;
                    r.Melds.Insert(0, new Meld
                    {
                        Type = "shunzi",
                        Tiles = new List<int> { tile, IndexToTile(i + 1), IndexToTile(i + 2) }
                    });
                    return r;
                }
                counts[i]++; counts[i + 1]++; counts[i + 2]++;
            }
        }

        // Try pair
        if (counts[i] >= 2 && pairCount == 0)
        {
            counts[i] -= 2;
            var r = TryExtractMelds(counts, wildcardCount, 1);
            if (r != null)
            {
                counts[i] += 2;
                r.PairTiles = new List<int> { tile, tile };
                return r;
            }
            counts[i] += 2;
        }

        // === Wildcard gap-fill (缺口填充) ===
        // Try kezi with 1 wildcard
        if (counts[i] >= 2 && wildcardCount >= 1)
        {
            counts[i] -= 2;
            var r = TryExtractMelds(counts, wildcardCount - 1, pairCount);
            if (r != null)
            {
                counts[i] += 2;
                r.Melds.Insert(0, new Meld { Type = "kezi", Tiles = new List<int> { tile, tile, -1 } });
                r.WildcardsUsed++;
                return r;
            }
            counts[i] += 2;
        }

        // Try kezi with 2 wildcards
        if (counts[i] >= 1 && wildcardCount >= 2)
        {
            counts[i] -= 1;
            var r = TryExtractMelds(counts, wildcardCount - 2, pairCount);
            if (r != null)
            {
                counts[i] += 1;
                r.Melds.Insert(0, new Meld { Type = "kezi", Tiles = new List<int> { tile, -1, -1 } });
                r.WildcardsUsed += 2;
                return r;
            }
            counts[i] += 1;
        }

        // Shunzi with 1 wildcard: need [tile, wild, tile+2]
        if (IsNumberedIndex(i) && i + 2 < 27 && SameSuitGroup(i, i + 2) && wildcardCount >= 1)
        {
            if (counts[i] >= 1 && counts[i + 2] >= 1)
            {
                counts[i]--; counts[i + 2]--;
                var r = TryExtractMelds(counts, wildcardCount - 1, pairCount);
                if (r != null)
                {
                    counts[i]++; counts[i + 2]++;
                    r.Melds.Insert(0, new Meld
                    {
                        Type = "shunzi",
                        Tiles = new List<int> { tile, -1, IndexToTile(i + 2) }
                    });
                    r.WildcardsUsed++;
                    return r;
                }
                counts[i]++; counts[i + 2]++;
            }
        }

        // Shunzi with 1 wildcard: need [tile, tile+1, wild]
        if (IsNumberedIndex(i) && i + 2 < 27 && SameSuitGroup(i, i + 2) && wildcardCount >= 1)
        {
            if (counts[i] >= 1 && counts[i + 1] >= 1)
            {
                counts[i]--; counts[i + 1]--;
                var r = TryExtractMelds(counts, wildcardCount - 1, pairCount);
                if (r != null)
                {
                    counts[i]++; counts[i + 1]++;
                    r.Melds.Insert(0, new Meld
                    {
                        Type = "shunzi",
                        Tiles = new List<int> { tile, IndexToTile(i + 1), -1 }
                    });
                    r.WildcardsUsed++;
                    return r;
                }
                counts[i]++; counts[i + 1]++;
            }
        }

        // Pair with 1 wildcard
        if (counts[i] >= 1 && wildcardCount >= 1 && pairCount == 0)
        {
            counts[i] -= 1;
            var r = TryExtractMelds(counts, wildcardCount - 1, 1);
            if (r != null)
            {
                counts[i] += 1;
                r.PairTiles = new List<int> { tile, -1 };
                r.WildcardsUsed++;
                return r;
            }
            counts[i] += 1;
        }

        return null;
    }

    private MeldsResult? FinalizeWithWildcards(int wildcardCount, int pairCount)
    {
        if (pairCount == 0)
        {
            // Need a pair — use 2 wildcards
            if (wildcardCount >= 2)
            {
                return new MeldsResult
                {
                    IsWin = true,
                    Melds = new List<Meld>(),
                    PairTiles = new List<int> { -1, -1 },
                    WildcardsUsed = 2
                };
            }
            return null;
        }
        // All tiles consumed, pair exists. Remaining wildcards form extra melds if any.
        // For simplicity: any remaining wildcards in multiples of 3 form kezi
        int remaining = wildcardCount;
        var extraMelds = new List<Meld>();
        while (remaining >= 3)
        {
            extraMelds.Add(new Meld { Type = "kezi", Tiles = new List<int> { -1, -1, -1 } });
            remaining -= 3;
        }
        return new MeldsResult
        {
            IsWin = true,
            Melds = extraMelds,
            PairTiles = new List<int>(),
            WildcardsUsed = wildcardCount - remaining
        };
    }

    private bool SameSuitGroup(int idxA, int idxB)
    {
        // Both must be in same numbered suit group (0-8, 9-17, 18-26)
        return (idxA / 9) == (idxB / 9) && idxA < 27 && idxB < 27;
    }

    private bool IsNumberedIndex(int idx) => idx < 27;

    // === 七对 ===
    private MeldsResult? TrySevenPairs(List<int> tiles, int wildcardCount)
    {
        // Count non-wildcard tiles
        var counts = new Dictionary<int, int>();
        foreach (var t in tiles)
        {
            if (MahjongTile.IsWildcard(t)) continue;
            if (MahjongTile.IsFlower(t)) return null; // 七对不能有花牌
            counts[t] = counts.GetValueOrDefault(t) + 1;
        }

        int needWildcards = 0;
        foreach (var (_, c) in counts)
        {
            if (c % 2 == 1)
                needWildcards++;  // need 1 wildcard to complete this pair
        }

        if (needWildcards <= wildcardCount)
        {
            var melds = new List<Meld>();
            foreach (var (t, c) in counts)
            {
                int pairs = c / 2;
                for (int p = 0; p < pairs; p++)
                    melds.Add(new Meld { Type = "pair", Tiles = new List<int> { t, t } });
            }
            return new MeldsResult
            {
                IsWin = true,
                Melds = melds,
                PairTiles = melds.LastOrDefault()?.Tiles ?? new List<int>(),
                WildcardsUsed = needWildcards
            };
        }
        return null;
    }

    // === 十三幺 ===
    private MeldsResult? TryThirteenOrphans(List<int> tiles, int wildcardCount)
    {
        // 13 unique terminal/honor tiles: 1万,9万,1条,9条,1筒,9筒 + 7字牌 = 13
        // + 1 duplicate = 14
        int[] required = { 1, 9, 11, 19, 21, 29, 31, 32, 33, 34, 35, 36, 37 };
        int present = 0;
        int extra = 0;  // duplicate of required tiles
        foreach (var t in tiles)
        {
            if (MahjongTile.IsWildcard(t)) continue;
            if (MahjongTile.IsFlower(t)) return null;
            if (required.Contains(t))
            {
                if (HasBit(present, t)) extra++;
                else present = SetBit(present, t);
            }
            else return null;  // non-terminal tile found
        }

        int unique = PopCount(present);
        int missing = 13 - unique;
        // Need wildcards for: missing unique tiles + 1 for the pair (if no duplicate exists)
        int neededForMissing = missing;
        int neededForPair = extra > 0 ? 0 : 1;  // duplicate already present → no pair wildcard needed
        int totalNeeded = neededForMissing + neededForPair;

        if (totalNeeded <= wildcardCount)
        {
            return new MeldsResult
            {
                IsWin = true,
                Melds = new List<Meld>(),
                PairTiles = new List<int>(),
                WildcardsUsed = totalNeeded
            };
        }
        return null;
    }

    private static bool HasBit(int bits, int tile)
    {
        int idx = tile switch
        {
            1 => 0, 9 => 1, 11 => 2, 19 => 3, 21 => 4, 29 => 5,
            31 => 6, 32 => 7, 33 => 8, 34 => 9, 35 => 10, 36 => 11, 37 => 12,
            _ => -1
        };
        return idx >= 0 && (bits & (1 << idx)) != 0;
    }

    private static int SetBit(int bits, int tile)
    {
        int idx = tile switch
        {
            1 => 0, 9 => 1, 11 => 2, 19 => 3, 21 => 4, 29 => 5,
            31 => 6, 32 => 7, 33 => 8, 34 => 9, 35 => 10, 36 => 11, 37 => 12,
            _ => -1
        };
        return idx >= 0 ? bits | (1 << idx) : bits;
    }

    private static int PopCount(int bits)
    {
        int count = 0;
        while (bits != 0) { count++; bits &= bits - 1; }
        return count;
    }

    // === 全不靠 (All Orphans) ===
    public MeldsResult? TryAllOrphans(List<int> tiles, int wildcardCount)
    {
        // 147, 258, 369 distribution + all 7 honors + any pair
        // For simplicity: check that no 2 tiles share the same suit with adjacent ranks
        // and all tiles are terminals/honors.
        foreach (var t in tiles)
        {
            if (MahjongTile.IsWildcard(t)) continue;
            if (MahjongTile.IsFlower(t)) return null;
            if (!MahjongTile.IsTerminal(t) && !MahjongTile.IsHonor(t)) return null;
        }

        // Check 147/258/369 pattern within each suit
        var suitTiles = new Dictionary<int, List<int>>();
        var honors = new List<int>();
        foreach (var t in tiles)
        {
            if (MahjongTile.IsWildcard(t)) continue;
            if (MahjongTile.IsHonor(t)) honors.Add(t);
            else
            {
                int s = MahjongTile.Suit(t);
                if (!suitTiles.ContainsKey(s)) suitTiles[s] = new List<int>();
                suitTiles[s].Add(t);
            }
        }

        // Each suit group must be in 147, 258, or 369 only
        int gapCount = 0;
        foreach (var (_, st) in suitTiles)
        {
            var ranks = st.Select(MahjongTile.Rank).Distinct().OrderBy(r => r).ToList();
            // Check ranks are all in same "gap-3" group
            var groups = ranks.GroupBy(r => (r - 1) % 3);
            if (groups.Count() > 1) return null;
            gapCount += ranks.Count;
        }

        // Need exactly 3 tiles per suit (one each of 3 gap groups) or wildcards to fill
        int missingSlots = 9 - gapCount;  // Max: 3 suits × 3 rank groups
        int honorNeeded = 7 - honors.Distinct().Count();
        if (honorNeeded < 0) honorNeeded = 0;

        int totalMissing = missingSlots + honorNeeded;
        if (totalMissing <= wildcardCount + 1)  // +1 for the pair tolerance
        {
            return new MeldsResult
            {
                IsWin = true,
                Melds = new List<Meld>(),
                PairTiles = new List<int>(),
                WildcardsUsed = Math.Min(totalMissing, wildcardCount)
            };
        }

        return null;
    }

    // === 一色双龙会 ===
    public MeldsResult? TryDoubleDragon(List<int> tiles, int wildcardCount)
    {
        // All same suit, 1-9 each at least 2 copies
        var nonWildTiles = tiles.Where(t => !MahjongTile.IsWildcard(t) && !MahjongTile.IsFlower(t)).ToList();
        if (nonWildTiles.Count == 0) return null;

        int suit = MahjongTile.Suit(nonWildTiles[0]);
        if (nonWildTiles.Any(t => MahjongTile.Suit(t) != suit)) return null;

        var rankCounts = new int[10]; // 1-indexed
        foreach (var t in nonWildTiles)
            rankCounts[MahjongTile.Rank(t)]++;

        int wildcardsAvailable = wildcardCount + tiles.Count(MahjongTile.IsWildcard);
        for (int r = 1; r <= 9; r++)
        {
            if (rankCounts[r] < 2)
            {
                int need = 2 - rankCounts[r];
                if (wildcardsAvailable >= need)
                    wildcardsAvailable -= need;
                else return null;
            }
        }
        // 18 tiles needed (1-9 × 2), but hand is 14. Extra 4 can come from melds that use
        // more than 2 of some ranks (forming shunzi halves)
        return new MeldsResult { IsWin = true, Melds = new List<Meld>(), PairTiles = new List<int>() };
    }

    // === 258将检查 ===
    private bool IsValid258Pair(int tileA, int tileB)
    {
        bool Check(int t)
        {
            if (t == -1) return true;  // wildcard
            int r = MahjongTile.Rank(t);
            return r == 2 || r == 5 || r == 8;
        }
        return Check(tileA) || Check(tileB);
    }

    // === 番型识别 ===
    public List<string> IdentifyFans(MeldsResult result)
    {
        var fans = new List<string>();
        var melds = result.Melds;
        var pair = result.PairTiles;

        // 清一色
        var allTiles = melds.SelectMany(m => m.Tiles.Where(t => t != -1)).Concat(pair.Where(t => t != -1)).ToList();
        if (allTiles.Count > 0)
        {
            var suits = allTiles.Select(MahjongTile.Suit).Distinct().ToList();
            if (suits.Count == 1 && suits[0] < 3)  // 万/条/筒 only (not 字/花)
                fans.Add("清一色");
        }

        // 对对胡 (all melds are kezi)
        if (melds.Count > 0 && melds.All(m => m.Type == "kezi"))
            fans.Add("对对胡");

        // 暗七对 (all melds are pairs)
        if (melds.Count > 0 && melds.All(m => m.Type == "pair"))
            fans.Add("暗七对");

        // 带幺九
        if (melds.Count > 0 && pair.Count >= 1)
        {
            bool allTerminals = melds.All(m =>
                m.Tiles.Where(t => t != -1).All(t => MahjongTile.IsTerminal(t)));
            bool pairTerminal = pair.All(t => t == -1 || MahjongTile.IsTerminal(t));
            if (allTerminals && pairTerminal)
                fans.Add("带幺九");
        }

        return fans;
    }

    // === 番型互斥应用 ===
    public List<string> ApplyFanExclusions(List<string> fans)
    {
        var toRemove = new HashSet<string>();
        foreach (var fan in fans)
        {
            if (_fanConfig.TryGetValue(fan, out var def))
            {
                if (def.Excludes != null)
                    foreach (var excluded in def.Excludes)
                        toRemove.Add(excluded);
                if (def.Conflicts != null)
                {
                    foreach (var conflict in def.Conflicts)
                    {
                        if (fans.Contains(conflict))
                        {
                            // Keep the higher fan
                            if (_fanConfig.TryGetValue(conflict, out var def2))
                            {
                                if (def2.BaseFan > def.BaseFan)
                                    toRemove.Add(fan);
                                else
                                    toRemove.Add(conflict);
                            }
                        }
                    }
                }
            }
        }
        return fans.Where(f => !toRemove.Contains(f)).ToList();
    }
}