using LocationsApi.Models;
using MongoDB.Bson;
using MongoDB.Driver;

namespace LocationsApi.Services;

public class LocationStore
{
    private readonly IMongoCollection<Location> _col;
    private readonly IMongoCollection<BsonDocument> _rawCol;
    private readonly IMongoCollection<CharacterDocument> _characters;
    private const string CoordIndexName = "coord_x_1_coord_y_1";

    public LocationStore(IConfiguration cfg)
    {
        var cs = cfg["MongoDB:ConnectionString"] ?? "mongodb://127.0.0.1:27017";
        var dbName = cfg["MongoDB:DatabaseName"] ?? "GameDb";
        var client = new MongoClient(cs);
        var db = client.GetDatabase(dbName);
        var collectionName = "Locations";
        EnsureLocationSchema(db, collectionName);
        _col = db.GetCollection<Location>(collectionName);
        _rawCol = db.GetCollection<BsonDocument>(collectionName);
        _characters = db.GetCollection<CharacterDocument>("Characters");

        EnsureCoordIndexes();

        EnsureOriginLocation();
    }

    private static void EnsureLocationSchema(IMongoDatabase db, string collectionName)
    {
        var validator = new BsonDocument
        {
            {
                "$jsonSchema", new BsonDocument
                {
                    { "bsonType", "object" },
                    { "required", new BsonArray { "name", "coord", "createdUtc" } },
                    {
                        "properties", new BsonDocument
                        {
                            { "name", new BsonDocument { { "bsonType", "string" } } },
                            {
                                "coord", new BsonDocument
                                {
                                    { "bsonType", "object" },
                                    { "required", new BsonArray { "x", "y" } },
                                    {
                                        "properties", new BsonDocument
                                        {
                                            { "x", new BsonDocument { { "bsonType", "int" } } },
                                            { "y", new BsonDocument { { "bsonType", "int" } } }
                                        }
                                    }
                                }
                            },
                            {
                                "resources", new BsonDocument
                                {
                                    { "bsonType", new BsonArray { "array", "null" } },
                                    {
                                        "items", new BsonDocument
                                        {
                                            { "bsonType", "object" },
                                            { "required", new BsonArray { "itemKey", "remainingQuantity", "gatherQuantity" } },
                                            {
                                                "properties", new BsonDocument
                                                {
                                                    { "itemKey", new BsonDocument { { "bsonType", "string" } } },
                                                    { "remainingQuantity", new BsonDocument { { "bsonType", "int" }, { "minimum", 0 } } },
                                                    { "gatherQuantity", new BsonDocument { { "bsonType", "int" }, { "minimum", 1 } } }
                                                }
                                            }
                                        }
                                    }
                                }
                            },
                            { "biomeKey", new BsonDocument { { "bsonType", new BsonArray { "string", "null" } } } },
                            {
                                "locationObject", new BsonDocument
                                {
                                    { "bsonType", new BsonArray { "object", "null" } },
                                    {
                                        "properties", new BsonDocument
                                        {
                                            { "id", new BsonDocument { { "bsonType", "string" } } },
                                            { "objectType", new BsonDocument { { "bsonType", "string" } } },
                                            { "objectKey", new BsonDocument { { "bsonType", "string" } } },
                                            { "name", new BsonDocument { { "bsonType", "string" } } },
                                            {
                                                "state", new BsonDocument
                                                {
                                                    { "bsonType", new BsonArray { "object", "null" } },
                                                    {
                                                        "properties", new BsonDocument
                                                        {
                                                            { "itemKey", new BsonDocument { { "bsonType", "string" } } },
                                                            { "remainingQuantity", new BsonDocument { { "bsonType", "int" }, { "minimum", 0 } } },
                                                            { "gatherQuantity", new BsonDocument { { "bsonType", "int" }, { "minimum", 1 } } }
                                                        }
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            },
                            { "locationObjectResolved", new BsonDocument { { "bsonType", new BsonArray { "bool", "null" } } } },
                            { "createdUtc", new BsonDocument { { "bsonType", "date" } } }
                        }
                    }
                }
            }
        };

        var collections = db.ListCollectionNames().ToList();
        if (!collections.Contains(collectionName))
        {
            var createCommand = new BsonDocument
            {
                { "create", collectionName },
                { "validator", validator },
                { "validationAction", "error" }
            };
            db.RunCommand<BsonDocument>(createCommand);
            return;
        }

        var command = new BsonDocument
        {
            { "collMod", collectionName },
            { "validator", validator },
            { "validationAction", "error" }
        };
        db.RunCommand<BsonDocument>(command);
    }

    public Task CreateAsync(Location location) => _col.InsertOneAsync(location);

    public Task<List<Location>> GetAllAsync() =>
        _col.Find(Builders<Location>.Filter.Empty).ToListAsync();

    public async Task<bool> DeleteAsync(string id)
    {
        var filter = Builders<Location>.Filter.Eq(l => l.Id, id);
        var result = await _col.DeleteOneAsync(filter);
        return result.DeletedCount > 0;
    }

    public async Task<bool> UpdateNameAsync(string id, string name)
    {
        var filter = Builders<Location>.Filter.Eq(l => l.Id, id);
        var update = Builders<Location>.Update.Set(l => l.Name, name);
        var result = await _col.UpdateOneAsync(filter, update);
        return result.ModifiedCount > 0;
    }

    public sealed record InteractResult(
        InteractStatus Status,
        string ObjectId = "",
        string ObjectType = "",
        string ItemKey = "",
        int QuantityGranted = 0,
        int RemainingQuantity = 0,
        bool Consumed = false,
        LocationObject? PreviousObject = null);

    public async Task<InteractResult> InteractWithObjectAsync(string locationId, string characterId, string objectId, string userId, bool allowAnyOwner)
    {
        var location = await _col.Find(l => l.Id == locationId).FirstOrDefaultAsync();
        if (location is null)
            return new InteractResult(InteractStatus.LocationNotFound);

        location = await EnsureLocationMetadataAsync(location);

        var character = await _characters.Find(c => c.Id == characterId).FirstOrDefaultAsync();
        if (character is null)
            return new InteractResult(InteractStatus.CharacterNotFound);
        if (!allowAnyOwner && character.OwnerUserId != userId)
            return new InteractResult(InteractStatus.Forbidden);
        if (character.Coord.X != location.Coord.X || character.Coord.Y != location.Coord.Y)
            return new InteractResult(InteractStatus.Invalid);

        var locationObject = location.LocationObject;
        if (locationObject is null)
            return new InteractResult(InteractStatus.ObjectNotFound);
        if (!string.Equals(locationObject.Id, objectId, StringComparison.Ordinal))
            return new InteractResult(InteractStatus.ObjectNotFound);
        if (!string.Equals(locationObject.ObjectType, "gatherable", StringComparison.OrdinalIgnoreCase))
            return new InteractResult(InteractStatus.UnsupportedObjectType);
        if (locationObject.State.RemainingQuantity <= 0)
            return new InteractResult(InteractStatus.ObjectConsumed);

        var quantityGranted = Math.Min(locationObject.State.GatherQuantity, locationObject.State.RemainingQuantity);
        var remainingQuantity = locationObject.State.RemainingQuantity - quantityGranted;
        var objectFilter = Builders<Location>.Filter.And(
            Builders<Location>.Filter.Eq(l => l.Id, locationId),
            Builders<Location>.Filter.Eq("locationObject.id", locationObject.Id),
            Builders<Location>.Filter.Eq("locationObject.state.remainingQuantity", locationObject.State.RemainingQuantity)
        );

        UpdateDefinition<Location> update;
        if (remainingQuantity <= 0)
        {
            update = Builders<Location>.Update.Unset("locationObject");
        }
        else
        {
            update = Builders<Location>.Update.Set("locationObject.state.remainingQuantity", remainingQuantity);
        }

        var result = await _col.UpdateOneAsync(objectFilter, update);
        if (result.ModifiedCount == 0)
            return new InteractResult(InteractStatus.ObjectConsumed);

        return new InteractResult(
            InteractStatus.Ok,
            locationObject.Id,
            locationObject.ObjectType,
            locationObject.State.ItemKey,
            quantityGranted,
            Math.Max(0, remainingQuantity),
            remainingQuantity <= 0,
            CloneLocationObject(locationObject));
    }

    public async Task RestoreObjectInteractionAsync(string locationId, LocationObject previousObject)
    {
        var filter = Builders<Location>.Filter.Eq(l => l.Id, locationId);
        var update = Builders<Location>.Update.Set(l => l.LocationObject, previousObject);
        await _col.UpdateOneAsync(filter, update);
    }

    private void EnsureCoordIndexes()
    {
        var indexes = _rawCol.Indexes.List().ToList();
        foreach (var index in indexes)
        {
            var name = index.GetValue("name", "").AsString;
            if (name == "_id_")
                continue;

            var keyDoc = index.GetValue("key", new BsonDocument()).AsBsonDocument;
            if (IsLegacyCoordIndex(keyDoc) || IsUnexpectedCoordIndex(keyDoc))
                _rawCol.Indexes.DropOne(name);
        }

        var coordIndex = new BsonDocument
        {
            { "coord.x", 1 },
            { "coord.y", 1 }
        };
        var coordIndexOptions = new CreateIndexOptions { Unique = true, Name = CoordIndexName };
        _rawCol.Indexes.CreateOne(new CreateIndexModel<BsonDocument>(coordIndex, coordIndexOptions));
    }

    private static bool IsLegacyCoordIndex(BsonDocument keyDoc) =>
        keyDoc.ElementCount == 2 &&
        keyDoc.TryGetValue("Coord.X", out var xValue) &&
        xValue.IsInt32 && xValue.AsInt32 == 1 &&
        keyDoc.TryGetValue("Coord.Y", out var yValue) &&
        yValue.IsInt32 && yValue.AsInt32 == 1;

    private static bool IsUnexpectedCoordIndex(BsonDocument keyDoc)
    {
        var hasLower = keyDoc.Contains("coord.x") || keyDoc.Contains("coord.y");
        var hasUpper = keyDoc.Contains("Coord.X") || keyDoc.Contains("Coord.Y");
        return hasUpper || (hasLower && !(keyDoc.Contains("coord.x") && keyDoc.Contains("coord.y")));
    }

    private void EnsureOriginLocation()
    {
        var filter = Builders<Location>.Filter.And(
            Builders<Location>.Filter.Eq(l => l.Coord.X, 0),
            Builders<Location>.Filter.Eq(l => l.Coord.Y, 0)
        );
        var existing = _col.Find(filter).FirstOrDefault();
        if (existing is not null)
            return;

        var origin = new Location
        {
            Name = "Origin",
            Coord = new Coord { X = 0, Y = 0 },
            BiomeKey = DetermineBiomeKey(0, 0),
            LocationObject = CreateLocationObjectForBiome(DetermineBiomeKey(0, 0), 0, 0),
            LocationObjectResolved = true,
            CreatedUtc = DateTime.UtcNow
        };

        try
        {
            _col.InsertOne(origin);
        }
        catch (MongoWriteException ex) when (ex.WriteError.Category == ServerErrorCategory.DuplicateKey)
        {
            // Another instance seeded it first.
        }
    }

    private static string NormalizeItemKey(string itemKey) => itemKey.Trim().ToLowerInvariant();

    private async Task<Location> EnsureLocationMetadataAsync(Location location)
    {
        if (!string.IsNullOrWhiteSpace(location.BiomeKey) && location.LocationObjectResolved)
            return location;

        var biomeKey = location.BiomeKey;
        if (string.IsNullOrWhiteSpace(biomeKey))
            biomeKey = DetermineBiomeKey(location.Coord.X, location.Coord.Y);

        var migratedObject = TryMigrateLegacyResources(location) ?? CreateLocationObjectForBiome(biomeKey, location.Coord.X, location.Coord.Y);
        var filter = Builders<Location>.Filter.And(
            Builders<Location>.Filter.Eq(l => l.Id, location.Id)
        );
        var update = Builders<Location>.Update
            .Set(l => l.BiomeKey, biomeKey)
            .Set(l => l.LocationObjectResolved, true)
            .Set(l => l.LocationObject, migratedObject);
        await _col.UpdateOneAsync(filter, update);
        location.BiomeKey = biomeKey;
        location.LocationObject = migratedObject;
        location.LocationObjectResolved = true;
        return location;
    }

    private static LocationObject? TryMigrateLegacyResources(Location location)
    {
        var legacyResource = location.Resources.FirstOrDefault(r => r.RemainingQuantity > 0);
        if (legacyResource is null)
            return null;

        return CreateGatherableObject(
            legacyResource.ItemKey,
            legacyResource.RemainingQuantity,
            legacyResource.GatherQuantity);
    }

    private static string DetermineBiomeKey(int x, int y)
    {
        if (x == 0 && y == 0)
            return "plains";

        var regionX = FloorDiv(x, 4);
        var regionY = FloorDiv(y, 4);
        var roll = Math.Abs(HashCode.Combine(regionX, regionY, 7919)) % 100;
        if (roll < 35)
            return "plains";
        if (roll < 60)
            return "forest";
        if (roll < 80)
            return "rocky";
        if (roll < 92)
            return "wetlands";
        return "desert";
    }

    private static LocationObject? CreateLocationObjectForBiome(string biomeKey, int x, int y)
    {
        var roll = Math.Abs(HashCode.Combine(x, y, 1543)) % 100;
        return biomeKey switch
        {
            "forest" => roll switch
            {
                < 35 => null,
                < 80 => CreateGatherableObject("wood", 60, 3),
                < 95 => CreateGatherableObject("grass", 120, 10),
                _ => CreateGatherableObject("stone", 40, 2)
            },
            "rocky" => roll switch
            {
                < 60 => null,
                < 90 => CreateGatherableObject("stone", 40, 2),
                _ => CreateGatherableObject("wood", 60, 3)
            },
            "wetlands" => roll switch
            {
                < 40 => null,
                < 90 => CreateGatherableObject("grass", 120, 10),
                _ => CreateGatherableObject("wood", 60, 3)
            },
            "desert" => roll switch
            {
                < 70 => null,
                < 95 => CreateGatherableObject("stone", 40, 2),
                _ => CreateGatherableObject("wood", 60, 3)
            },
            _ => roll switch
            {
                < 50 => null,
                < 85 => CreateGatherableObject("grass", 120, 10),
                _ => CreateGatherableObject("wood", 60, 3)
            }
        };
    }

    private static LocationObject CreateGatherableObject(string itemKey, int remainingQuantity, int gatherQuantity)
    {
        var normalizedItemKey = NormalizeItemKey(itemKey);
        return new LocationObject
        {
            Id = Guid.NewGuid().ToString("N"),
            ObjectType = "gatherable",
            ObjectKey = $"{normalizedItemKey}_node",
            Name = HumanizeItemKey(normalizedItemKey),
            State = new LocationObjectState
            {
                ItemKey = normalizedItemKey,
                RemainingQuantity = remainingQuantity,
                GatherQuantity = gatherQuantity
            }
        };
    }

    private static string HumanizeItemKey(string itemKey)
    {
        return string.Join(" ", itemKey.Split('_', StringSplitOptions.RemoveEmptyEntries)
            .Select(part => char.ToUpperInvariant(part[0]) + part[1..]));
    }

    private static int FloorDiv(int value, int divisor)
    {
        var quotient = value / divisor;
        var remainder = value % divisor;
        if (remainder != 0 && ((remainder < 0) != (divisor < 0)))
            quotient -= 1;
        return quotient;
    }

    private static LocationObject CloneLocationObject(LocationObject source)
    {
        return new LocationObject
        {
            Id = source.Id,
            ObjectType = source.ObjectType,
            ObjectKey = source.ObjectKey,
            Name = source.Name,
            State = new LocationObjectState
            {
                ItemKey = source.State.ItemKey,
                RemainingQuantity = source.State.RemainingQuantity,
                GatherQuantity = source.State.GatherQuantity
            }
        };
    }

    [MongoDB.Bson.Serialization.Attributes.BsonIgnoreExtraElements]
    private class CharacterDocument
    {
        [MongoDB.Bson.Serialization.Attributes.BsonId]
        [MongoDB.Bson.Serialization.Attributes.BsonRepresentation(MongoDB.Bson.BsonType.ObjectId)]
        public string? Id { get; set; }

        public string OwnerUserId { get; set; } = string.Empty;

        public Coord Coord { get; set; } = new();
    }
}

public enum InteractStatus
{
    Ok,
    LocationNotFound,
    CharacterNotFound,
    Forbidden,
    Invalid,
    ObjectNotFound,
    UnsupportedObjectType,
    ObjectConsumed
}