// Copyright (c) Microsoft. All rights reserved.

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using Microsoft.Extensions.AI;
using Microsoft.Extensions.VectorData;
using Microsoft.Extensions.VectorData.ProviderServices;
using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;

namespace Microsoft.SemanticKernel.Connectors.MongoDB;

/// <summary>
/// Customized MongoDB model builder that adds specialized configuration of property storage names
/// (Mongo's reserve key property name and [BsonElement]).
/// </summary>
internal class MongoModelBuilder() : CollectionModelBuilder(s_validationOptions)
{
    internal const string SupportedVectorTypes = "ReadOnlyMemory<float>, Embedding<float>, float[]";

    private static readonly CollectionModelBuildingOptions s_validationOptions = new()
    {
        RequiresAtLeastOneVector = false,
        SupportsMultipleKeys = false,
        SupportsMultipleVectors = true,
        UsesExternalSerializer = true,
    };

    [RequiresUnreferencedCode("Traverses the CLR type's properties with reflection, so not compatible with trimming")]
    protected override void ProcessTypeProperties(Type type, VectorStoreCollectionDefinition? definition)
    {
        base.ProcessTypeProperties(type, definition);

        foreach (var property in this.Properties)
        {
            if (property.PropertyInfo?.GetCustomAttribute<BsonElementAttribute>() is { } bsonElementAttribute)
            {
                property.StorageName = bsonElementAttribute.ElementName;
            }
        }
    }

    protected override bool IsKeyPropertyTypeValid(Type type, [NotNullWhen(false)] out string? supportedTypes)
    {
        supportedTypes = "string, int, long, Guid, ObjectId";

        return type == typeof(string) || type == typeof(int) || type == typeof(long) || type == typeof(Guid) || type == typeof(ObjectId);
    }

    protected override bool IsDataPropertyTypeValid(Type type, [NotNullWhen(false)] out string? supportedTypes)
    {
        supportedTypes = "string, int, long, double, float, bool, DateTimeOffset, or arrays/lists of these types";

        if (Nullable.GetUnderlyingType(type) is Type underlyingType)
        {
            type = underlyingType;
        }

        return IsValid(type)
            || (type.IsArray && IsValid(type.GetElementType()!))
            || (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>) && IsValid(type.GenericTypeArguments[0]));

        static bool IsValid(Type type)
            => type == typeof(bool) ||
                type == typeof(string) ||
                type == typeof(int) ||
                type == typeof(long) ||
                type == typeof(float) ||
                type == typeof(double) ||
                type == typeof(decimal) ||
                type == typeof(DateTime);
    }

    protected override bool IsVectorPropertyTypeValid(Type type, [NotNullWhen(false)] out string? supportedTypes)
        => IsVectorPropertyTypeValidCore(type, out supportedTypes);

    internal static bool IsVectorPropertyTypeValidCore(Type type, [NotNullWhen(false)] out string? supportedTypes)
    {
        supportedTypes = SupportedVectorTypes;

        return type == typeof(ReadOnlyMemory<float>)
            || type == typeof(ReadOnlyMemory<float>?)
            || type == typeof(Embedding<float>)
            || type == typeof(float[]);
    }
}
