// 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.Globalization;
using System.Linq;
using Microsoft.CodeAnalysis.CodeFixes;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.Shared.Extensions;

internal static class TelemetryExtensions
{
    public static Guid GetTelemetryId(this Type type, short scope = 0, string? additionalSuffixString = null)
    {
        type = GetTypeForTelemetry(type);
        Contract.ThrowIfNull(type.FullName);

        // AssemblyQualifiedName will change across version numbers, FullName won't

        // Use a stable hashing algorithm (FNV) that doesn't depend on platform
        // or .NET implementation.
        var suffix = Roslyn.Utilities.Hash.GetFNVHashCode(type.FullName);

        // Suffix is the remaining 8 bytes, and the hash code only makes up 4. Pad
        // the remainder with an empty byte array
        var suffixBytes = BitConverter.GetBytes(suffix).Concat(new byte[4]).ToArray();

        // Generate additional suffix to add to the Guid.
        var additionalSuffix = (short)(additionalSuffixString != null
            ? Hash.GetFNVHashCode(additionalSuffixString)
            : 0);

        return new Guid(0, scope, additionalSuffix, suffixBytes);
    }

    public static Type GetTypeForTelemetry(this Type type)
        => type.IsConstructedGenericType ? type.GetGenericTypeDefinition() : type;

    public static short GetScopeIdForTelemetry(this FixAllScope scope)
        => scope switch
        {
            FixAllScope.Document => 1,
            FixAllScope.Project => 2,
            FixAllScope.Solution => 3,
            FixAllScope.Custom => 4,
            FixAllScope.ContainingMember => 5,
            FixAllScope.ContainingType => 6,
            _ => 7,
        };

    public static string GetTelemetryDiagnosticID(this Diagnostic diagnostic)
    {
        // we log diagnostic id as it is if it is from us
        if (diagnostic.Descriptor.ImmutableCustomTags().Any(static t => t == WellKnownDiagnosticTags.Telemetry))
        {
            return diagnostic.Id;
        }

        // if it is from third party, we use hashcode
        return diagnostic.GetHashCode().ToString(CultureInfo.InvariantCulture);
    }
}