// 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.Collections.Immutable;
using System.Composition;
using System.Threading;
using Microsoft.CodeAnalysis.BraceMatching;
using Microsoft.CodeAnalysis.EmbeddedLanguages;
using Microsoft.CodeAnalysis.EmbeddedLanguages.Common;
using Microsoft.CodeAnalysis.EmbeddedLanguages.RegularExpressions;
using Microsoft.CodeAnalysis.EmbeddedLanguages.VirtualChars;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.Features.EmbeddedLanguages.RegularExpressions.LanguageServices;

using RegexToken = EmbeddedSyntaxToken<RegexKind>;
using RegexTrivia = EmbeddedSyntaxTrivia<RegexKind>;

/// <summary>
/// Brace matching impl for embedded regex strings.
/// </summary>
[ExportEmbeddedLanguageBraceMatcher(
    PredefinedEmbeddedLanguageNames.Regex,
    [LanguageNames.CSharp, LanguageNames.VisualBasic],
    supportsUnannotatedAPIs: true,
    "Regex", "Regexp"), Shared]
internal sealed class RegexBraceMatcher : IEmbeddedLanguageBraceMatcher
{
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public RegexBraceMatcher()
    {
    }

    public BraceMatchingResult? FindBraces(
        Project project,
        SemanticModel semanticModel,
        SyntaxToken token,
        int position,
        BraceMatchingOptions options,
        CancellationToken cancellationToken)
    {
        if (!options.HighlightingOptions.HighlightRelatedRegexComponentsUnderCursor)
            return null;

        var info = project.GetRequiredLanguageService<IEmbeddedLanguagesProvider>().EmbeddedLanguageInfo;
        var detector = RegexLanguageDetector.GetOrCreate(semanticModel.Compilation, info);
        var tree = detector.TryParseString(token, semanticModel, cancellationToken);

        return tree == null ? null : GetMatchingBraces(tree, position);
    }

    private static BraceMatchingResult? GetMatchingBraces(RegexTree tree, int position)
    {
        var virtualChar = tree.Text.Find(position);
        if (virtualChar == null)
            return null;

        var ch = virtualChar.Value;
        return ch.Value switch
        {
            '(' or ')' => FindGroupingBraces(tree, ch) ?? FindCommentBraces(tree, ch),
            '[' or ']' => FindCharacterClassBraces(tree, ch),
            _ => null,
        };
    }

    private static BraceMatchingResult? CreateResult(RegexToken open, RegexToken close)
        => open.IsMissing || close.IsMissing
            ? null
            : new BraceMatchingResult(open.VirtualChars[0].Span, close.VirtualChars[0].Span);

    private static BraceMatchingResult? FindCommentBraces(RegexTree tree, VirtualChar ch)
    {
        var trivia = FindTrivia(tree.Root, ch);
        if (trivia?.Kind != RegexKind.CommentTrivia)
            return null;

        var firstChar = trivia.Value.VirtualChars[0];
        var lastChar = trivia.Value.VirtualChars[^1];
        return firstChar != '(' || lastChar != ')'
            ? null
            : new BraceMatchingResult(firstChar.Span, lastChar.Span);
    }

    private static BraceMatchingResult? FindGroupingBraces(RegexTree tree, VirtualChar ch)
    {
        var node = FindGroupingNode(tree.Root, ch);
        return node == null ? null : CreateResult(node.OpenParenToken, node.CloseParenToken);
    }

    private static BraceMatchingResult? FindCharacterClassBraces(RegexTree tree, VirtualChar ch)
    {
        var node = FindCharacterClassNode(tree.Root, ch);
        return node == null ? null : CreateResult(node.OpenBracketToken, node.CloseBracketToken);
    }

    private static RegexGroupingNode? FindGroupingNode(RegexNode node, VirtualChar ch)
        => FindNode<RegexGroupingNode>(node, ch, (grouping, c) =>
                grouping.OpenParenToken.VirtualChars.Contains(c) || grouping.CloseParenToken.VirtualChars.Contains(c));

    private static RegexBaseCharacterClassNode? FindCharacterClassNode(RegexNode node, VirtualChar ch)
        => FindNode<RegexBaseCharacterClassNode>(node, ch, (grouping, c) =>
                grouping.OpenBracketToken.VirtualChars.Contains(c) || grouping.CloseBracketToken.VirtualChars.Contains(c));

    private static TNode? FindNode<TNode>(RegexNode node, VirtualChar ch, Func<TNode, VirtualChar, bool> predicate)
        where TNode : RegexNode
    {
        if (node is TNode nodeMatch && predicate(nodeMatch, ch))
            return nodeMatch;

        foreach (var child in node)
        {
            if (child.IsNode)
            {
                var result = FindNode(child.Node, ch, predicate);
                if (result != null)
                    return result;
            }
        }

        return null;
    }

    private static RegexTrivia? FindTrivia(RegexNode node, VirtualChar ch)
    {
        foreach (var child in node)
        {
            if (child.IsNode)
            {
                var result = FindTrivia(child.Node, ch);
                if (result != null)
                    return result;
            }
            else
            {
                var token = child.Token;
                var trivia = TryGetTrivia(token.LeadingTrivia, ch) ??
                             TryGetTrivia(token.TrailingTrivia, ch);

                if (trivia != null)
                    return trivia;
            }
        }

        return null;
    }

    private static RegexTrivia? TryGetTrivia(ImmutableArray<RegexTrivia> triviaList, VirtualChar ch)
    {
        foreach (var trivia in triviaList)
        {
            if (trivia.VirtualChars.Contains(ch))
                return trivia;
        }

        return null;
    }
}