// 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.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.AI;
using Microsoft.Shared.DiagnosticIds;
 
namespace Microsoft.Extensions.VectorData.ProviderServices;
 
/// <inheritdoc />
[Experimental(DiagnosticIds.Experiments.VectorDataProviderServices, UrlFormat = DiagnosticIds.UrlFormat)]
public sealed class VectorPropertyModel<TInput>(string modelName) : VectorPropertyModel(modelName, typeof(TInput))
{
    /// <inheritdoc />
    public override bool CanGenerateEmbedding<TEmbedding>(IEmbeddingGenerator embeddingGenerator)
        => embeddingGenerator is IEmbeddingGenerator<TInput, TEmbedding>
        || base.CanGenerateEmbedding<TEmbedding>(embeddingGenerator);
 
    /// <inheritdoc />
    public override Type? ResolveEmbeddingType<TEmbedding>(IEmbeddingGenerator embeddingGenerator, Type? userRequestedEmbeddingType)
        => embeddingGenerator switch
        {
            IEmbeddingGenerator<TInput, TEmbedding> when Type == typeof(TInput) && (userRequestedEmbeddingType is null || userRequestedEmbeddingType == typeof(TEmbedding))
                => typeof(TEmbedding),
 
            null => throw new ArgumentNullException(nameof(embeddingGenerator), "This method should only be called when an embedding generator is configured."),
            _ => null
        };
 
    /// <inheritdoc />
    internal override async Task<IReadOnlyList<Embedding>> GenerateEmbeddingsCoreAsync<TEmbedding>(IEnumerable<object?> values, CancellationToken cancellationToken)
        => EmbeddingGenerator switch
        {
            IEmbeddingGenerator<TInput, TEmbedding> generator when EmbeddingType == typeof(TEmbedding) => await generator.GenerateAsync(
                                values.Select(v => v is TInput s
                                    ? s
                                    : throw new InvalidOperationException($"Property '{ModelName}' was configured with an embedding generator accepting a {typeof(TInput).Name}, but {v?.GetType().Name ?? "null"} was provided.")),
                                cancellationToken: cancellationToken).ConfigureAwait(false),
            null => throw new UnreachableException("This method should only be called when an embedding generator is configured."),
            _ => throw new InvalidOperationException(
                                $"The embedding generator configured on property '{ModelName}' cannot produce an embedding of type '{typeof(TEmbedding).Name}' for the given input type."),
        };
 
    /// <inheritdoc />
    internal override async Task<Embedding> GenerateEmbeddingCoreAsync<TEmbedding>(object? value, CancellationToken cancellationToken)
    {
        if (EmbeddingGenerator is IEmbeddingGenerator<TInput, TEmbedding> generator && value is TInput t)
        {
            return await generator.GenerateAsync(t, cancellationToken: cancellationToken).ConfigureAwait(false);
        }
 
        // Fall through to base class which checks for string and DataContent input types.
        return await base.GenerateEmbeddingCoreAsync<TEmbedding>(value, cancellationToken).ConfigureAwait(false);
    }
 
    /// <inheritdoc />
    public override Type[] GetSupportedInputTypes() => [typeof(TInput)];
}