// 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.Collections.Immutable;
using System.Diagnostics;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixesAndRefactorings;

namespace Microsoft.CodeAnalysis.CodeFixes;

/// <summary>
/// Implement this type to provide fixes for source code problems.
/// Remember to use <see cref="ExportCodeFixProviderAttribute"/> so the host environment can offer your fixes in a UI.
/// </summary>
public abstract class CodeFixProvider : IRefactorOrFixProvider
{
    private protected ImmutableArray<string> CustomTags = [];

    /// <summary>
    /// A list of diagnostic IDs that this provider can provide fixes for.
    /// </summary>
    public abstract ImmutableArray<string> FixableDiagnosticIds { get; }

    /// <summary>
    /// Computes one or more fixes for the specified <see cref="CodeFixContext"/>.
    /// </summary>
    /// <param name="context">
    /// A <see cref="CodeFixContext"/> containing context information about the diagnostics to fix.
    /// The context must only contain diagnostics with a <see cref="Diagnostic.Id"/> included in the <see cref="FixableDiagnosticIds"/> for the current provider.
    /// </param>
    public abstract Task RegisterCodeFixesAsync(CodeFixContext context);

    /// <summary>
    /// Gets an optional <see cref="FixAllProvider"/> that can fix all/multiple occurrences of diagnostics fixed by this code fix provider.
    /// Return null if the provider doesn't support fix all/multiple occurrences.
    /// Otherwise, you can return any of the well known fix all providers from <see cref="WellKnownFixAllProviders"/> or implement your own fix all provider.
    /// </summary>
    public virtual FixAllProvider? GetFixAllProvider()
        => null;

    /// <summary>
    /// Computes the <see cref="CodeActionRequestPriority"/> group this provider should be considered to run at. Legal values
    /// this can be must be between <see cref="CodeActionRequestPriority.Low"/> and <see cref="CodeActionPriority.High"/>.
    /// </summary>
    /// <remarks>
    /// Values outside of this range will be clamped to be within that range.  Requests for <see
    /// cref="CodeActionRequestPriority.High"/> may be downgraded to <see cref="CodeActionRequestPriority.Default"/> as they
    /// poorly behaving high-priority providers can cause a negative user experience.
    /// </remarks>
    protected virtual CodeActionRequestPriority ComputeRequestPriority()
        => CodeActionRequestPriority.Default;

    /// <summary>
    /// Priority class this refactoring provider should run at. Returns <see
    /// cref="CodeActionRequestPriority.Default"/> if not overridden.  Slower, or less relevant, providers should
    /// override this and return a lower value to not interfere with computation of normal priority providers.
    /// </summary>
    public CodeActionRequestPriority RequestPriority
    {
        get
        {
            var priority = ComputeRequestPriority();
            Debug.Assert(priority is CodeActionRequestPriority.Low or CodeActionRequestPriority.Default or CodeActionRequestPriority.High, "Provider returned invalid priority");
            return priority.Clamp(this.CustomTags);
        }
    }
}