// 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.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Threading;
using Microsoft.CodeAnalysis.Collections;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.Navigation;

internal static partial class NavigableItemFactory
{
    public static INavigableItem GetItemFromSymbolLocation(
        Solution solution, ISymbol symbol, Location location,
        ImmutableArray<TaggedText>? displayTaggedParts)
    {
        return new SymbolLocationNavigableItem(
            solution, symbol, location, displayTaggedParts);
    }

    public static ImmutableArray<INavigableItem> GetItemsFromPreferredSourceLocations(
        Solution solution,
        ISymbol symbol,
        ImmutableArray<TaggedText>? displayTaggedParts,
        CancellationToken cancellationToken)
    {
        var locations = GetPreferredSourceLocations(solution, symbol, cancellationToken);
        return locations.SelectAsArray(loc => GetItemFromSymbolLocation(
            solution, symbol, loc, displayTaggedParts));
    }

    public static IEnumerable<Location> GetPreferredSourceLocations(
        Solution solution, ISymbol symbol, CancellationToken cancellationToken)
    {
        // Prefer non-generated source locations over generated ones.

        var sourceLocations = GetPreferredSourceLocations(symbol);

        var candidateLocationGroups = from c in sourceLocations
                                      let doc = solution.GetDocument(c.SourceTree)
                                      where doc != null
                                      group c by doc.IsGeneratedCode(cancellationToken);

        var generatedSourceLocations = candidateLocationGroups.SingleOrDefault(g => g.Key) ?? SpecializedCollections.EmptyEnumerable<Location>();
        var nonGeneratedSourceLocations = candidateLocationGroups.SingleOrDefault(g => !g.Key) ?? SpecializedCollections.EmptyEnumerable<Location>();

        return nonGeneratedSourceLocations.Any() ? nonGeneratedSourceLocations : generatedSourceLocations;
    }

    private static IEnumerable<Location> GetPreferredSourceLocations(ISymbol symbol)
    {
        var locations = symbol.Locations;

        // First return visible source locations if we have them.  Else, go to the non-visible 
        // source locations.  
        var visibleSourceLocations = locations.Where(loc => loc.IsVisibleSourceLocation());
        return visibleSourceLocations.Any()
            ? visibleSourceLocations
            : locations.Where(loc => loc.IsInSource);
    }
}