// 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.
 
#nullable disable
 
using System.Collections.Immutable;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.FindSymbols;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.AddImport
{
    internal abstract partial class AbstractAddImportFeatureService<TSimpleNameSyntax>
    {
        /// <summary>
        /// SearchScope is used to control where the <see cref="AbstractAddImportFeatureService{TSimpleNameSyntax}"/>
        /// searches.  We search different scopes in different ways.  For example we use 
        /// SymbolTreeInfos to search unreferenced projects and metadata dlls.  However,
        /// for the current project we're editing we defer to the compiler to do the 
        /// search.
        /// </summary>
        private abstract class SearchScope
        {
            public readonly bool Exact;
            protected readonly AbstractAddImportFeatureService<TSimpleNameSyntax> provider;
            public readonly CancellationToken CancellationToken;
 
            protected SearchScope(AbstractAddImportFeatureService<TSimpleNameSyntax> provider, bool exact, CancellationToken cancellationToken)
            {
                this.provider = provider;
                Exact = exact;
                CancellationToken = cancellationToken;
            }
 
            protected abstract Task<ImmutableArray<ISymbol>> FindDeclarationsAsync(SymbolFilter filter, SearchQuery query);
            public abstract SymbolReference CreateReference<T>(SymbolResult<T> symbol) where T : INamespaceOrTypeSymbol;
 
            public async Task<ImmutableArray<SymbolResult<ISymbol>>> FindDeclarationsAsync(
                string name, TSimpleNameSyntax nameNode, SymbolFilter filter)
            {
                if (name != null && string.IsNullOrWhiteSpace(name))
                {
                    return ImmutableArray<SymbolResult<ISymbol>>.Empty;
                }
 
                using var query = Exact ? SearchQuery.Create(name, ignoreCase: true) : SearchQuery.CreateFuzzy(name);
                var symbols = await FindDeclarationsAsync(filter, query).ConfigureAwait(false);
 
                if (Exact)
                {
                    // We did an exact, case insensitive, search.  Case sensitive matches should
                    // be preferred though over insensitive ones.
                    return symbols.SelectAsArray(s =>
                        SymbolResult.Create(s.Name, nameNode, s, weight: s.Name == name ? 0 : 1));
                }
 
                // TODO(cyrusn): It's a shame we have to compute this twice.  However, there's no
                // great way to store the original value we compute because it happens deep in the 
                // compiler bowels when we call FindDeclarations.
                var similarityChecker = WordSimilarityChecker.Allocate(name, substringsAreSimilar: false);
 
                var result = symbols.SelectAsArray(s =>
                {
                    var areSimilar = similarityChecker.AreSimilar(s.Name, out var matchCost);
 
                    Debug.Assert(areSimilar);
                    return SymbolResult.Create(s.Name, nameNode, s, matchCost);
                });
 
                similarityChecker.Free();
 
                return result;
            }
        }
    }
}