// 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;
 
        protected SearchScope(AbstractAddImportFeatureService<TSimpleNameSyntax> provider, bool exact)
        {
            this.provider = provider;
            Exact = exact;
        }
 
        protected abstract Task<ImmutableArray<ISymbol>> FindDeclarationsAsync(SymbolFilter filter, SearchQuery query, CancellationToken cancellationToken);
 
        public abstract SymbolReference CreateReference<T>(SymbolResult<T> symbol) where T : INamespaceOrTypeSymbol;
 
        public async Task<ImmutableArray<SymbolResult<ISymbol>>> FindDeclarationsAsync(
            string name, TSimpleNameSyntax nameNode, SymbolFilter filter, CancellationToken cancellationToken)
        {
            cancellationToken.ThrowIfCancellationRequested();
            if (name != null && string.IsNullOrWhiteSpace(name))
            {
                return [];
            }
 
            using var query = Exact ? SearchQuery.Create(name, ignoreCase: true) : SearchQuery.CreateFuzzy(name);
            var symbols = await FindDeclarationsAsync(filter, query, cancellationToken).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.
            using var similarityChecker = new WordSimilarityChecker(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);
            });
 
            return result;
        }
    }
}