// 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.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.Simplification;

namespace Microsoft.CodeAnalysis.ChangeNamespace;

internal interface IChangeNamespaceService : ILanguageService
{
    AbstractReducer NameReducer { get; }

    /// <summary>
    /// Determine whether we can change the namespace for given <paramref name="container"/> in the document.
    /// Linked documents are not supported, except for a regular document in a multi-targeting project, 
    /// where the container node must be consistent among all linked documents.
    /// Here's the additional requirements on <paramref name="container"/> to use this service:
    /// 
    /// - If <paramref name="container"/> is a namespace declaration node:
    ///    1. Doesn't contain or is nested in other namespace declarations
    ///    2. The name of the namespace is valid (i.e. no errors)
    ///    3. No partial type declared in the namespace. Otherwise its multiple declarations will
    ///       end up in different namespace.
    ///
    /// - If <paramref name="container"/> is a compilation unit node:
    ///    1. It must contain no namespace declaration
    ///    2. No partial type declared in the document. Otherwise its multiple declarations will
    ///       end up in different namespace.
    ///       
    /// - Otherwise, an <see cref="System.ArgumentException"/> will be thrown.
    ///   
    /// Returns <see langword="true"/> only when all the requirements above are met.
    /// </summary>
    /// <remarks>
    /// While this service might be used by features that change namespace based on some property of the document
    /// (e.g. Sync namespace refactoring), those logic is implemented by those individual features and isn't part 
    /// of the IChangeNamespaceService service.
    /// </remarks>
    Task<bool> CanChangeNamespaceAsync(Document document, SyntaxNode container, CancellationToken cancellationToken);

    /// <summary>
    /// Change namespace for given <paramref name="container"/> to the name specified by <paramref name="targetNamespace"/>.
    /// Everything declared in the <paramref name="container"/> will be moved to the new namespace. 
    /// Change will only be made if <see cref="CanChangeNamespaceAsync"/> returns <see langword="true"/> and <paramref name="targetNamespace"/>
    /// is a valid name for namespace. Use "" for <paramref name="targetNamespace"/> to specify the global namespace.
    /// 
    /// An <see cref="System.ArgumentException"/> will be thrown if:
    /// 1. <paramref name="container"/> is not a namespace declaration or a compilation unit node.
    /// 2. <paramref name="targetNamespace"/> is null or contains an invalid character.
    /// </summary>
    /// <remarks>
    /// If the declared namespace for <paramref name="container"/> is already identical to <paramref name="targetNamespace"/>, then it will be
    /// a no-op and original solution will be returned.
    /// </remarks>
    Task<Solution> ChangeNamespaceAsync(Document document, SyntaxNode container, string targetNamespace, CancellationToken cancellationToken);

    /// <summary>
    /// Using only the top level namespace declarations of a document, change all of them to the target namespace. Will only
    /// use namespace containers considered valid by <see cref="CanChangeNamespaceAsync(Document, SyntaxNode, CancellationToken)"/>
    /// </summary>
    Task<Solution?> TryChangeTopLevelNamespacesAsync(Document document, string targetNamespace, CancellationToken cancellationToken);
}