// 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.Diagnostics;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp.Formatting;
 
/// <summary>
/// trivia factory.
/// 
/// it will cache some commonly used trivia to reduce memory footprint and heap allocation
/// </summary>
internal sealed partial class TriviaDataFactory : AbstractTriviaDataFactory
{
    public TriviaDataFactory(TreeData treeInfo, LineFormattingOptions options)
        : base(treeInfo, options)
    {
    }
 
    private static bool IsCSharpWhitespace(char c)
        => SyntaxFacts.IsWhitespace(c) || SyntaxFacts.IsNewLine(c);
 
    public override TriviaData CreateLeadingTrivia(SyntaxToken token)
    {
        // no trivia
        if (!token.HasLeadingTrivia)
        {
            Debug.Assert(this.TreeInfo.GetTextBetween(default, token).All(IsCSharpWhitespace));
            return GetSpaceTriviaData(space: 0);
        }
 
        var result = Analyzer.Leading(token);
        var info = GetWhitespaceOnlyTriviaInfo(default, token, result);
        if (info != null)
        {
            Debug.Assert(this.TreeInfo.GetTextBetween(default, token).All(IsCSharpWhitespace));
            return info;
        }
 
        return new ComplexTrivia(this.Options, this.TreeInfo, default, token);
    }
 
    public override TriviaData CreateTrailingTrivia(SyntaxToken token)
    {
        // no trivia
        if (!token.HasTrailingTrivia)
        {
            Debug.Assert(this.TreeInfo.GetTextBetween(token, default).All(IsCSharpWhitespace));
            return GetSpaceTriviaData(space: 0);
        }
 
        var result = Analyzer.Trailing(token);
        var info = GetWhitespaceOnlyTriviaInfo(token, default, result);
        if (info != null)
        {
            Debug.Assert(this.TreeInfo.GetTextBetween(token, default).All(IsCSharpWhitespace));
            return info;
        }
 
        return new ComplexTrivia(this.Options, this.TreeInfo, token, default);
    }
 
    public override TriviaData Create(SyntaxToken token1, SyntaxToken token2)
    {
        // no trivia in between
        if (!token1.HasTrailingTrivia && !token2.HasLeadingTrivia)
        {
            Debug.Assert(string.IsNullOrWhiteSpace(this.TreeInfo.GetTextBetween(token1, token2)));
            return GetSpaceTriviaData(space: 0);
        }
 
        var result = Analyzer.Between(token1, token2);
        var info = GetWhitespaceOnlyTriviaInfo(token1, token2, result);
        if (info != null)
        {
            Debug.Assert(string.IsNullOrWhiteSpace(this.TreeInfo.GetTextBetween(token1, token2)));
            return info;
        }
 
        return new ComplexTrivia(this.Options, this.TreeInfo, token1, token2);
    }
 
    private static bool ContainsOnlyWhitespace(Analyzer.AnalysisResult result)
    {
        return
            !result.HasComments &&
            !result.HasPreprocessor &&
            !result.HasSkippedTokens &&
            !result.HasSkippedOrDisabledText &&
            !result.HasConflictMarker;
    }
 
    private TriviaData? GetWhitespaceOnlyTriviaInfo(SyntaxToken token1, SyntaxToken token2, Analyzer.AnalysisResult result)
    {
        if (!ContainsOnlyWhitespace(result))
        {
            return null;
        }
 
        // only whitespace in between
        var space = GetSpaceOnSingleLine(result);
        Contract.ThrowIfFalse(space >= -1);
 
        if (space >= 0)
        {
            // check whether we can use cache
            return GetSpaceTriviaData(space, result.TreatAsElastic);
        }
 
        // tab is used in a place where it is not an indentation
        if (result.LineBreaks == 0 && result.Tab > 0)
        {
            // calculate actual space size from tab
            var spaces = CalculateSpaces(token1, token2);
            return new ModifiedWhitespace(this.Options, result.LineBreaks, indentation: spaces, elastic: result.TreatAsElastic);
        }
 
        // check whether we can cache trivia info for current indentation
        var lineCountAndIndentation = GetLineBreaksAndIndentation(result);
 
        return GetWhitespaceTriviaData(lineCountAndIndentation.lineBreaks, lineCountAndIndentation.indentation, lineCountAndIndentation.canUseTriviaAsItIs, result.TreatAsElastic);
    }
 
    private int CalculateSpaces(SyntaxToken token1, SyntaxToken token2)
    {
        var initialColumn = (token1.RawKind == 0) ? 0 : this.TreeInfo.GetOriginalColumn(Options.TabSize, token1) + token1.Span.Length;
        var textSnippet = this.TreeInfo.GetTextBetween(token1, token2);
 
        return textSnippet.ConvertTabToSpace(Options.TabSize, initialColumn, textSnippet.Length);
    }
 
    private (bool canUseTriviaAsItIs, int lineBreaks, int indentation) GetLineBreaksAndIndentation(Analyzer.AnalysisResult result)
    {
        Debug.Assert(result.Tab >= 0);
        Debug.Assert(result.LineBreaks >= 0);
 
        var indentation = result.Tab * Options.TabSize + result.Space;
        if (result.HasTrailingSpace || result.HasUnknownWhitespace)
        {
            if (result.HasUnknownWhitespace && result.LineBreaks == 0 && indentation == 0)
            {
                // make sure we don't remove all whitespace
                indentation = 1;
            }
 
            return (canUseTriviaAsItIs: false, result.LineBreaks, indentation);
        }
 
        if (!Options.UseTabs)
        {
            if (result.Tab > 0)
            {
                return (canUseTriviaAsItIs: false, result.LineBreaks, indentation);
            }
 
            return (canUseTriviaAsItIs: true, result.LineBreaks, indentation);
        }
 
        Debug.Assert(Options.UseTabs);
 
        // tab can only appear before space to be a valid tab for indentation
        if (result.HasTabAfterSpace)
        {
            return (canUseTriviaAsItIs: false, result.LineBreaks, indentation);
        }
 
        if (result.Space >= Options.TabSize)
        {
            return (canUseTriviaAsItIs: false, result.LineBreaks, indentation);
        }
 
        Debug.Assert((indentation / Options.TabSize) == result.Tab);
        Debug.Assert((indentation % Options.TabSize) == result.Space);
 
        return (canUseTriviaAsItIs: true, result.LineBreaks, indentation);
    }
 
    private static int GetSpaceOnSingleLine(Analyzer.AnalysisResult result)
    {
        if (result.HasTrailingSpace || result.HasUnknownWhitespace || result.LineBreaks > 0 || result.Tab > 0)
        {
            return -1;
        }
 
        return result.Space;
    }
}