using CodePlay.Core.Common;
using CodePlay.Core.Models;

namespace CodePlay.Core.Services;

/// <summary>
/// 不可转换语法处理器
/// 识别和标记无法直接转换的语法结构
/// </summary>
public class UnconvertibleSyntaxHandler
{
    private static readonly HashSet<string> CSharpUnconvertibleKeywords = new()
    {
        "async", "await",
        "dynamic",
        "var",
        "yield",
        "unsafe",
        "fixed",
        "checked",
        "unchecked",
        "nameof",
        "is",
        "record",
        "init",
        "with",
        "not",
        "and",
        "or"
    };
    
    private static readonly HashSet<string> CSharpUnconvertiblePatterns = new()
    {
        "LINQ",
        @"\bawait\s+\w+\b",
        @"\basync\s+\w+",
        @"\bvar\s+\w+\s*=\s*new\b",
        @"\busing\s+\w+\s*=",
        @"\?\.", // 空条件运算符
        @"\?\?", // 空合并运算符
        @"\$\{", // 字符串插值
        @"\brecord\s+\w+",
        @"\binit\s*{",
        @"\bwith\s*{",
        @"\bdelegate\s*\(",
        @"\bevent\s+",
        @"\bref\s+\w+",
        @"\bout\s+\w+",
        @"\bin\b" // C# 9 pattern
    };
    
    /// <summary>
    /// 检测 C# 代码中的不可转换语法
    /// </summary>
    public List<ConversionIssue> DetectUnconvertibleSyntax(string sourceCode, LanguageType sourceLanguage, LanguageType targetLanguage)
    {
        var issues = new List<ConversionIssue>();
        var lines = sourceCode.Split('\n');
        
        for (int i = 0; i < lines.Length; i++)
        {
            var line = lines[i];
            var lineNumber = i + 1;
            
            // 检查关键词
            foreach (var keyword in CSharpUnconvertibleKeywords.Where(k => k != "switch"))
            {
                if (System.Text.RegularExpressions.Regex.IsMatch(line, $@"\b{keyword}\b"))
                {
                    issues.Add(new ConversionIssue
                    {
                        Type = IssueType.UnconvertibleSyntax.ToString(),
                        Severity = IssueSeverity.Medium.ToString(),
                        LineNumber = lineNumber,
                        Description = $"C# keyword '{keyword}' cannot be directly converted to {targetLanguage}",
                        Suggestion = GetSuggestion(keyword, targetLanguage),
                        OriginalCode = line.Trim(),
                        Language = sourceLanguage.ToName()
                    });
                }
            }
            
            // 检查模式
            foreach (var pattern in CSharpUnconvertiblePatterns)
            {
                if (pattern.StartsWith(@"\") && System.Text.RegularExpressions.Regex.IsMatch(line, pattern))
                {
                    issues.Add(new ConversionIssue
                    {
                        Type = IssueType.UnconvertibleSyntax.ToString(),
                        Severity = IssueSeverity.Medium.ToString(),
                        LineNumber = lineNumber,
                        Description = $"Pattern '{pattern}' cannot be directly converted to {targetLanguage}",
                        Suggestion = GetPatternSuggestion(pattern, targetLanguage),
                        OriginalCode = line.Trim(),
                        Language = sourceLanguage.ToName()
                    });
                }
                else if (!pattern.StartsWith(@"\") && line.Contains(pattern))
                {
                    issues.Add(new ConversionIssue
                    {
                        Type = IssueType.UnconvertibleSyntax.ToString(),
                        Severity = IssueSeverity.Medium.ToString(),
                        LineNumber = lineNumber,
                        Description = $"Pattern containing '{pattern}' cannot be directly converted to {targetLanguage}",
                        Suggestion = GetPatternSuggestion(pattern, targetLanguage),
                        OriginalCode = line.Trim(),
                        Language = sourceLanguage.ToName()
                    });
                }
            }
        }
        
        return issues;
    }
    
    /// <summary>
    /// 获取关键词的转换建议
    /// </summary>
    private string GetSuggestion(string keyword, LanguageType targetLanguage)
    {
        return keyword switch
        {
            "async" => $"Use CompletableFuture (Java) or std::future (C++) for asynchronous operations",
            "await" => $"Use .join() (Java) or .get() (C++) to wait for async results",
            "dynamic" => $"Use Object (Java) with explicit casting, or templates (C++)",
            "var" => $"Use explicit type declaration in {targetLanguage}",
            "yield" => $"Implement Iterator pattern with hasNext()/next() (Java) or begin()/end() (C++)",
            "unsafe" => $"Use JNI (Java) or native pointers with caution (C++)",
            "fixed" => $"Use pinned memory or GC.KeepAlive (Java: Unsafe class)",
            "nameof" => $"Use reflection or manual string literals",
            "record" => $"Generate immutable class with final fields and getter methods",
            "init" => $"Use constructor or builder pattern",
            "with" => $"Use copy constructor or builder pattern",
            "not" => $"Use ! operator or Objects.isNull() (Java)",
            "and" => $"Use && operator",
            "or" => $"Use || operator",
            _ => $"Manual refactoring required"
        };
    }
    
    /// <summary>
    /// 获取模式的转换建议
    /// </summary>
    private string GetPatternSuggestion(string pattern, LanguageType targetLanguage)
    {
        return pattern switch
        {
            @"\bLINQ\b" => "Convert to Stream API (Java) or STL algorithms (C++)",
            @"\basync\s+\w+" => "Use CompletableFuture (Java) or std::async (C++)",
            @"\bvar\s+\w+\s*=\s*new\b" => "Replace with explicit type declaration",
            @"\busing\s+\w+\s*=" => "Use try-with-resources (Java) or RAII pattern (C++)",
            @"\?\." => "Add explicit null checks before method/property access",
            @"\?\?" => "Use Objects.requireNonNullElse (Java) or ternary operator",
            @"\$\{" => $"Use String.format() (Java) or std::format (C++)",
            @"\brecord\s+\w+" => "Convert to immutable class with equals/hashCode/toString",
            @"\bdelegate\s*\(" => "Convert to functional interface (Java) or std::function (C++)",
            @"\bevent\s+" => "Implement observer pattern with add/remove methods",
            @"\bref\s+\w+" => "Pass by reference using pointers (C++) or mutable wrapper (Java)",
            @"\bout\s+\w+" => "Return tuple or use holder class",
            _ => "Manual refactoring required"
        };
    }
    
    /// <summary>
    /// 生成 TODO 注释标记
    /// </summary>
    public string GenerateTodoComment(ConversionIssue issue)
    {
        return $"""
            // TODO [CONVERSION]: {issue.Description}
            // Original: {issue.OriginalCode}
            // Suggestion: {issue.Suggestion ?? "Manual refactoring required"}
            // Severity: {issue.Severity}
            """;
    }
    
    /// <summary>
    /// 评估转换可行性
    /// </summary>
    public ConversionFeasibility AssessFeasibility(string sourceCode, LanguageType sourceLanguage, LanguageType targetLanguage)
    {
        var issues = DetectUnconvertibleSyntax(sourceCode, sourceLanguage, targetLanguage);
        
        var highSeverity = issues.Count(i => i.Severity == "High");
        var mediumSeverity = issues.Count(i => i.Severity == "Medium");
        var lowSeverity = issues.Count(i => i.Severity == "Low");
        
        var feasibility = new ConversionFeasibility
        {
            IsFeasible = highSeverity == 0 && mediumSeverity < 5,
            ConfidenceScore = CalculateConfidenceScore(issues),
            EstimatedManualEffort = CalculateEstimatedEffort(issues),
            CriticalIssues = issues.Where(i => i.Severity == "High").ToList(),
            AllIssues = issues
        };
        
        return feasibility;
    }
    
    private int CalculateConfidenceScore(List<ConversionIssue> issues)
    {
        var baseScore = 100;
        baseScore -= issues.Count(i => i.Severity == "High") * 20;
        baseScore -= issues.Count(i => i.Severity == "Medium") * 5;
        baseScore -= issues.Count(i => i.Severity == "Low") * 2;
        
        return Math.Max(0, Math.Min(100, baseScore));
    }
    
    private string CalculateEstimatedEffort(List<ConversionIssue> issues)
    {
        var totalScore = issues.Sum(i => i.Severity switch
        {
            nameof(IssueSeverity.High) => 4,
            nameof(IssueSeverity.Medium) => 2,
            nameof(IssueSeverity.Low) => 1,
            _ => 1
        });
        
        return totalScore switch
        {
            0 => "No manual effort required",
            <= 3 => "Minimal (< 15 minutes)",
            <= 10 => "Low (15-30 minutes)",
            <= 20 => "Moderate (30-60 minutes)",
            > 20 => "High (> 1 hour)"
        };
    }
}

/// <summary>
/// 转换可行性评估结果
/// </summary>
public class ConversionFeasibility
{
    public bool IsFeasible { get; set; }
    public int ConfidenceScore { get; set; } // 0-100
    public string EstimatedManualEffort { get; set; } = string.Empty;
    public List<ConversionIssue> CriticalIssues { get; set; } = new();
    public List<ConversionIssue> AllIssues { get; set; } = new();
}