// 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.Diagnostics.CodeAnalysis;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Shared.Extensions;
 
internal static partial class SyntaxTreeExtensions
{
    public static bool OverlapsHiddenPosition([NotNullWhen(returnValue: true)] this SyntaxTree? tree, TextSpan span, CancellationToken cancellationToken)
    {
        // Short-circuit if there are no line mappings to avoid potentially realizing the source text.
        // All lines are visible if there are no line mappings.
        if (tree == null || tree.GetLineMappings(cancellationToken).IsEmpty())
        {
            return false;
        }
 
        var text = tree.GetText(cancellationToken);
 
        return text.OverlapsHiddenPosition(span, (position, cancellationToken2) =>
            {
                // implements the ASP.NET IsHidden rule
                var lineVisibility = tree.GetLineVisibility(position, cancellationToken2);
                return lineVisibility is LineVisibility.Hidden or LineVisibility.BeforeFirstLineDirective;
            },
            cancellationToken);
    }
 
    public static bool IsScript(this SyntaxTree syntaxTree)
        => syntaxTree.Options.Kind != SourceCodeKind.Regular;
 
    /// <summary>
    /// Returns the identifier, keyword, contextual keyword or preprocessor keyword touching this
    /// position, or a token of Kind = None if the caret is not touching either.
    /// </summary>
    public static Task<SyntaxToken> GetTouchingWordAsync(
        this SyntaxTree syntaxTree,
        int position,
        ISyntaxFacts syntaxFacts,
        CancellationToken cancellationToken,
        bool findInsideTrivia = false)
    {
        return GetTouchingTokenAsync(syntaxTree, semanticModel: null, position, (_, t) => syntaxFacts.IsWord(t), cancellationToken, findInsideTrivia);
    }
 
    public static Task<SyntaxToken> GetTouchingTokenAsync(
        this SyntaxTree syntaxTree,
        int position,
        CancellationToken cancellationToken,
        bool findInsideTrivia = false)
    {
        return GetTouchingTokenAsync(syntaxTree, semanticModel: null, position, (_, _) => true, cancellationToken, findInsideTrivia);
    }
 
    public static async Task<SyntaxToken> GetTouchingTokenAsync(
        this SyntaxTree syntaxTree,
        SemanticModel? semanticModel,
        int position,
        Func<SemanticModel?, SyntaxToken, bool> predicate,
        CancellationToken cancellationToken,
        bool findInsideTrivia = false)
    {
        Contract.ThrowIfNull(syntaxTree);
 
        if (position > syntaxTree.Length)
        {
            return default;
        }
 
        var root = await syntaxTree.GetRootAsync(cancellationToken).ConfigureAwait(false);
        var token = root.FindToken(position, findInsideTrivia);
 
        if ((token.Span.Contains(position) || token.Span.End == position) && predicate(semanticModel, token))
        {
            return token;
        }
 
        token = token.GetPreviousToken();
 
        if (token.Span.End == position && predicate(semanticModel, token))
        {
            return token;
        }
 
        // SyntaxKind = None
        return default;
    }
 
    public static bool IsEntirelyHidden(this SyntaxTree tree, TextSpan span, CancellationToken cancellationToken)
    {
        if (!tree.HasHiddenRegions())
        {
            return false;
        }
 
        var text = tree.GetText(cancellationToken);
        var startLineNumber = text.Lines.IndexOf(span.Start);
        var endLineNumber = text.Lines.IndexOf(span.End);
 
        for (var lineNumber = startLineNumber; lineNumber <= endLineNumber; lineNumber++)
        {
            cancellationToken.ThrowIfCancellationRequested();
 
            var linePosition = text.Lines[lineNumber].Start;
            if (!tree.IsHiddenPosition(linePosition, cancellationToken))
            {
                return false;
            }
        }
 
        return true;
    }
 
    public static bool IsBeforeFirstToken(this SyntaxTree syntaxTree, int position, CancellationToken cancellationToken)
    {
        var root = syntaxTree.GetRoot(cancellationToken);
        var firstToken = root.GetFirstToken(includeZeroWidth: true, includeSkipped: true);
 
        return position <= firstToken.SpanStart;
    }
 
    public static SyntaxToken FindTokenOrEndToken(
        this SyntaxTree syntaxTree, int position, CancellationToken cancellationToken)
    {
        Contract.ThrowIfNull(syntaxTree);
 
        var root = syntaxTree.GetRoot(cancellationToken);
        var result = root.FindToken(position, findInsideTrivia: true);
        if (result.RawKind != 0)
        {
            return result;
        }
 
        // Special cases.  See if we're actually at the end of a:
        // a) doc comment
        // b) pp directive
        // c) file
 
        var compilationUnit = (ICompilationUnitSyntax)root;
        var triviaList = compilationUnit.EndOfFileToken.LeadingTrivia;
        foreach (var trivia in triviaList.Reverse())
        {
            if (trivia.HasStructure)
            {
                var token = trivia.GetStructure()!.GetLastToken(includeZeroWidth: true);
                if (token.Span.End == position)
                {
                    return token;
                }
            }
        }
 
        if (position == root.FullSpan.End)
        {
            return compilationUnit.EndOfFileToken;
        }
 
        return default;
    }
 
    internal static SyntaxTrivia FindTriviaAndAdjustForEndOfFile(
        this SyntaxTree syntaxTree, int position, CancellationToken cancellationToken, bool findInsideTrivia = false)
    {
        var root = syntaxTree.GetRoot(cancellationToken);
        var trivia = root.FindTrivia(position, findInsideTrivia);
 
        // If we ask right at the end of the file, we'll get back nothing.
        // We handle that case specially for now, though SyntaxTree.FindTrivia should
        // work at the end of a file.
        if (position == root.FullWidth())
        {
            var compilationUnit = (ICompilationUnitSyntax)root;
            var endOfFileToken = compilationUnit.EndOfFileToken;
            if (endOfFileToken.HasLeadingTrivia)
            {
                trivia = endOfFileToken.LeadingTrivia.Last();
            }
            else
            {
                var token = endOfFileToken.GetPreviousToken(includeSkipped: true);
                if (token.HasTrailingTrivia)
                {
                    trivia = token.TrailingTrivia.Last();
                }
            }
        }
 
        return trivia;
    }
 
    /// <summary>
    /// If the position is inside of token, return that token; otherwise, return the token to the right.
    /// </summary>
    public static SyntaxToken FindTokenOnRightOfPosition(
        this SyntaxTree syntaxTree,
        int position,
        CancellationToken cancellationToken,
        bool includeSkipped = true,
        bool includeDirectives = false,
        bool includeDocumentationComments = false)
    {
        return syntaxTree.GetRoot(cancellationToken).FindTokenOnRightOfPosition(
            position, includeSkipped, includeDirectives, includeDocumentationComments);
    }
 
    /// <summary>
    /// If the position is inside of token, return that token; otherwise, return the token to the left.
    /// </summary>
    public static SyntaxToken FindTokenOnLeftOfPosition(
        this SyntaxTree syntaxTree,
        int position,
        CancellationToken cancellationToken,
        bool includeSkipped = true,
        bool includeDirectives = false,
        bool includeDocumentationComments = false)
    {
        return syntaxTree.GetRoot(cancellationToken).FindTokenOnLeftOfPosition(
            position, includeSkipped, includeDirectives, includeDocumentationComments);
    }
 
    public static bool IsGeneratedCode(this SyntaxTree syntaxTree, AnalyzerOptions? analyzerOptions, ISyntaxFacts syntaxFacts, CancellationToken cancellationToken)
    {
        // First check if user has configured "generated_code = true | false" in .editorconfig
        if (analyzerOptions != null)
        {
            var analyzerConfigOptions = analyzerOptions.AnalyzerConfigOptionsProvider.GetOptions(syntaxTree);
            var isUserConfiguredGeneratedCode = GeneratedCodeUtilities.GetGeneratedCodeKindFromOptions(analyzerConfigOptions).ToNullable();
            if (isUserConfiguredGeneratedCode.HasValue)
            {
                return isUserConfiguredGeneratedCode.Value;
            }
        }
 
        // Otherwise, fallback to generated code heuristic.
        return GeneratedCodeUtilities.IsGeneratedCode(
            syntaxTree, t => syntaxFacts.IsRegularComment(t) || syntaxFacts.IsDocumentationComment(t), cancellationToken);
    }
 
    /// <summary>
    /// Finds the node in the given <paramref name="syntaxTree"/> corresponding to the given <paramref name="span"/>.
    /// If the <paramref name="span"/> is <see langword="null"/>, then returns the root node of the tree.
    /// </summary>
    public static SyntaxNode FindNode(this SyntaxTree syntaxTree, TextSpan? span, bool findInTrivia, bool getInnermostNodeForTie, CancellationToken cancellationToken)
    {
        var root = syntaxTree.GetRoot(cancellationToken);
        return root.FindNode(span, findInTrivia, getInnermostNodeForTie);
    }
}