// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.Composition;

namespace Microsoft.CodeAnalysis.EmbeddedLanguages;

/// <summary>
/// Use this attribute to export an <see cref="IEmbeddedLanguageFeatureService"/>.
/// </summary>
[MetadataAttribute]
[AttributeUsage(AttributeTargets.Class)]
internal abstract class ExportEmbeddedLanguageFeatureServiceAttribute : ExportAttribute
{
    /// <summary>
    /// Name of the classifier.
    /// </summary>
    public string Name { get; }

    /// <summary>
    /// Names of the containing language hosting the embedded language.  e.g. C# or VB.
    /// </summary>
    public string[] Languages { get; }

    /// <summary>
    /// Identifiers in code (or StringSyntaxAttribute) used to identify an embedded language string. For example
    /// <c>Regex</c> or <c>Json</c>.
    /// </summary>
    /// <remarks>This can be used to find usages of an embedded language using a comment marker like <c>//
    /// lang=regex</c> or passed to a symbol annotated with <c>[StringSyntaxAttribyte("Regex")]</c>.  The identifier
    /// is case sensitive for the StringSyntaxAttribute, and case insensitive for the comment.
    /// </remarks>
    public string[] Identifiers { get; }

    /// <inheritdoc cref="EmbeddedLanguageMetadata.SupportsUnannotatedAPIs"/>
    internal bool SupportsUnannotatedAPIs { get; }

    public ExportEmbeddedLanguageFeatureServiceAttribute(
        Type contractType, string name, string[] languages, params string[] identifiers)
        : this(contractType, name, languages, supportsUnannotatedAPIs: false, identifiers)
    {
    }

    internal ExportEmbeddedLanguageFeatureServiceAttribute(
        Type contractType, string name, string[] languages, bool supportsUnannotatedAPIs, params string[] identifiers)
        : base(contractType)
    {
        Name = name ?? throw new ArgumentNullException(nameof(name));
        Languages = languages ?? throw new ArgumentNullException(nameof(languages));
        Identifiers = identifiers ?? throw new ArgumentNullException(nameof(identifiers));
        SupportsUnannotatedAPIs = supportsUnannotatedAPIs;

        Contract.ThrowIfFalse(contractType.IsInterface && typeof(IEmbeddedLanguageFeatureService).IsAssignableFrom(contractType),
            $"{nameof(contractType)} must be an interface and derived from {typeof(IEmbeddedLanguageFeatureService).FullName}");

        if (SupportsUnannotatedAPIs)
        {
            Contract.ThrowIfFalse(name is PredefinedEmbeddedLanguageNames.Regex or PredefinedEmbeddedLanguageNames.Json,
                $"Only '{PredefinedEmbeddedLanguageNames.Regex}' or '{PredefinedEmbeddedLanguageNames.Json}' are allowed to '{nameof(SupportsUnannotatedAPIs)}'");
        }
    }
}