// 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.Generic;
using System.Linq;
using System.Text;
using Microsoft.CodeAnalysis.Editor.UnitTests.Utilities;
using Microsoft.CodeAnalysis.EmbeddedLanguages.Common;
using Microsoft.CodeAnalysis.EmbeddedLanguages.StackFrame;
using Microsoft.CodeAnalysis.EmbeddedLanguages.VirtualChars;
using Roslyn.Test.Utilities;
using Xunit;
using static Microsoft.CodeAnalysis.Editor.UnitTests.EmbeddedLanguages.StackFrame.StackFrameSyntaxFactory;
 
namespace Microsoft.CodeAnalysis.Editor.UnitTests.EmbeddedLanguages.StackFrame;
 
using StackFrameToken = EmbeddedSyntaxToken<StackFrameKind>;
 
public partial class StackFrameParserTests
{
    private static void Verify(
        string input,
        StackFrameMethodDeclarationNode? methodDeclaration = null,
        bool expectFailure = false,
        StackFrameFileInformationNode? fileInformation = null,
        StackFrameToken? eolTokenOpt = null)
    {
        FuzzyTest(input);
 
        var tree = StackFrameParser.TryParse(input);
        if (expectFailure)
        {
            Assert.Null(tree);
            return;
        }
 
        AssertEx.NotNull(tree);
        VerifyCharacterSpans(input, tree);
 
        if (methodDeclaration is null)
        {
            Assert.Null(tree.Root.MethodDeclaration);
        }
        else
        {
            StackFrameUtils.AssertEqual(methodDeclaration, tree.Root.MethodDeclaration);
        }
 
        if (fileInformation is null)
        {
            Assert.Null(tree.Root.FileInformationExpression);
        }
        else
        {
            StackFrameUtils.AssertEqual(fileInformation, tree.Root.FileInformationExpression);
        }
 
        var eolToken = eolTokenOpt.HasValue
            ? eolTokenOpt.Value
            : CreateToken(StackFrameKind.EndOfFrame, "");
 
        StackFrameUtils.AssertEqual(eolToken, tree.Root.EndOfLineToken);
    }
 
    /// <summary>
    /// Tests that with a given input, no crashes are found
    /// with multiple substrings of the input
    /// </summary>
    private static void FuzzyTest(string input)
    {
        for (var i = 0; i < input.Length - 1; i++)
        {
            StackFrameParser.TryParse(input[i..]);
            StackFrameParser.TryParse(input[..^i]);
 
            for (var j = 0; j + i < input.Length; j++)
            {
                var start = input[..j];
                var end = input[(j + i)..];
                StackFrameParser.TryParse(start + end);
            }
        }
    }
 
    private static void VerifyCharacterSpans(string originalText, StackFrameTree tree)
    {
        AssertEx.EqualOrDiff(originalText, tree.Root.ToFullString());
 
        // Manually enumerate to verify that it works as expected and the spans align.
        // This should be the same as ToFullString, but this tests that enumeration of the 
        // tokens yields the correct order (which we can't guarantee with ToFullString depending
        // on implementation). 
        var textSeq = VirtualCharSequence.Create(0, originalText);
        var index = 0;
        List<VirtualChar> enumeratedParsedCharacters = [];
 
        foreach (var charSeq in StackFrameUtils.Enumerate(tree.Root))
        {
            foreach (var ch in charSeq)
            {
                enumeratedParsedCharacters.Add(ch);
 
                if (textSeq[index++] != ch)
                {
                    Assert.True(false, PrintDifference());
                }
            }
        }
 
        // Make sure we enumerated the total input
        Assert.Equal(textSeq.Length, index);
 
        string PrintDifference()
        {
            var sb = new StringBuilder();
 
            var start = Math.Max(0, index - 10);
            var end = Math.Min(index, originalText.Length - 1);
 
            sb.Append("Expected: \t");
            PrintString(originalText, start, end, sb);
            sb.AppendLine();
 
            sb.Append("Actual: \t");
            var enumeratedString = new string(enumeratedParsedCharacters.Select(ch => (char)ch.Value).ToArray());
            PrintString(enumeratedString, start, end, sb);
            sb.AppendLine();
 
            return sb.ToString();
 
            static void PrintString(string s, int start, int end, StringBuilder sb)
            {
                if (start > 0)
                {
                    sb.Append("...");
                }
 
                sb.Append(s[start..end]);
 
                if (end < s.Length - 1)
                {
                    sb.Append("...");
                }
            }
        }
    }
}