// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.AI;
using Microsoft.Shared.DiagnosticIds;
 
namespace Microsoft.Extensions.VectorData.ProviderServices;
 
/// <summary>
/// Represents a model builder that performs logic specific to providers that use System.Text.Json for serialization.
/// This is an internal support type meant for use by providers only and not by applications.
/// </summary>
[Experimental(DiagnosticIds.Experiments.VectorDataProviderServices, UrlFormat = DiagnosticIds.UrlFormat)]
public abstract class CollectionJsonModelBuilder : CollectionModelBuilder
{
    private JsonSerializerOptions? _jsonSerializerOptions;
 
    /// <summary>
    /// Initializes a new instance of the <see cref="CollectionJsonModelBuilder"/> class.
    /// </summary>
    protected CollectionJsonModelBuilder(CollectionModelBuildingOptions options)
        : base(options)
    {
    }
 
    /// <summary>
    /// Builds and returns a <see cref="CollectionModel"/> from the given <paramref name="recordType"/> and <paramref name="definition"/>.
    /// </summary>
    /// <returns>The built <see cref="CollectionModel"/>.</returns>
    [RequiresDynamicCode("This model building variant is not compatible with NativeAOT. See BuildDynamic() for dynamic mapping, and a third variant accepting source-generated delegates will be introduced in the future.")]
    [RequiresUnreferencedCode("This model building variant is not compatible with trimming. See BuildDynamic() for dynamic mapping, and a third variant accepting source-generated delegates will be introduced in the future.")]
    public virtual CollectionModel Build(
        Type recordType,
        Type keyType,
        VectorStoreCollectionDefinition? definition,
        IEmbeddingGenerator? defaultEmbeddingGenerator,
        JsonSerializerOptions jsonSerializerOptions)
    {
        _jsonSerializerOptions = jsonSerializerOptions;
 
        return Build(recordType, keyType, definition, defaultEmbeddingGenerator);
    }
 
    /// <summary>
    /// Builds and returns a <see cref="CollectionModel"/> for dynamic mapping scenarios from the given <paramref name="definition"/>.
    /// </summary>
    /// <returns>The built <see cref="CollectionModel"/>.</returns>
    public virtual CollectionModel BuildDynamic(
        VectorStoreCollectionDefinition definition,
        IEmbeddingGenerator? defaultEmbeddingGenerator,
        JsonSerializerOptions jsonSerializerOptions)
    {
        _jsonSerializerOptions = jsonSerializerOptions;
 
        return BuildDynamic(definition, defaultEmbeddingGenerator);
    }
 
    /// <inheritdoc/>
    protected override void Customize()
    {
        // This mimics the naming behavior of the System.Text.Json serializer, which we use for serialization/deserialization.
        // The property storage names in the model must be in sync with the serializer configuration, since the model is used e.g. for filtering
        // even if serialization/deserialization doesn't use the model.
        var namingPolicy = _jsonSerializerOptions?.PropertyNamingPolicy;
 
        foreach (var property in Properties)
        {
            var keyPropertyWithReservedName = Options.ReservedKeyStorageName is not null && property is KeyPropertyModel;
            string storageName;
 
            if (property.PropertyInfo?.GetCustomAttribute<JsonPropertyNameAttribute>() is { } jsonPropertyNameAttribute)
            {
                if (keyPropertyWithReservedName && jsonPropertyNameAttribute.Name != Options.ReservedKeyStorageName)
                {
                    throw new InvalidOperationException($"The key property for your provider must always have the reserved name '{Options.ReservedKeyStorageName}' and cannot be changed.");
                }
 
                storageName = jsonPropertyNameAttribute.Name;
            }
            else if (namingPolicy is not null)
            {
                storageName = namingPolicy.ConvertName(property.ModelName);
            }
            else
            {
                storageName = property.ModelName;
            }
 
            if (keyPropertyWithReservedName)
            {
                // Some providers (Weaviate, Cosmos NoSQL) have a fixed, reserved storage name for keys (id), and at the same time use an external
                // JSON serializer to serialize the entire user POCO. Since the serializer is unaware of the reserved storage name, it will produce
                // a storage name as usual, based on the .NET property's name, possibly with a naming policy applied to it. The provider then needs
                // to look that up and replace with the reserved name.
                ((KeyPropertyModel)property).SerializedKeyName = storageName;
            }
            else
            {
                property.StorageName = storageName;
            }
        }
    }
}