using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace AxCopilot.Services.Agent;

/// <summary>
/// 작업 폴더의 구조/기술스택/컨벤션을 분석하여 .ax-context.md를 자동 생성합니다.
/// LLM 호출 없이 순수 파일 시스템 분석으로 동작합니다.
/// </summary>
internal static class WorkspaceContextGenerator
{
    private const string ContextFileName = ".ax-context.md";
    private const int MaxDepth = 3;
    private const int MaxReadmeChars = 2000;
    private const int MaxContextChars = 4000;

    private static readonly HashSet<string> SkipDirs = new(StringComparer.OrdinalIgnoreCase)
    {
        ".git", "node_modules", "bin", "obj", ".vs", "__pycache__", ".idea",
        ".vscode", "dist", "build", "target", ".next", ".nuget", "packages",
        ".ax", "coverage", ".mypy_cache", "venv", ".venv", "env",
    };

    /// <summary>
    /// .ax-context.md가 없으면 생성합니다. 이미 있으면 기존 내용을 반환합니다.
    /// </summary>
    public static async Task<string?> EnsureContextAsync(string workFolder, CancellationToken ct = default)
    {
        if (string.IsNullOrEmpty(workFolder) || !Directory.Exists(workFolder))
            return null;

        var path = Path.Combine(workFolder, ContextFileName);
        if (File.Exists(path))
            return LoadContext(workFolder);

        return await GenerateAsync(workFolder, ct).ConfigureAwait(false);
    }

    /// <summary>
    /// 강제 재생성합니다.
    /// </summary>
    public static async Task<string> GenerateAsync(string workFolder, CancellationToken ct = default)
    {
        var sb = new StringBuilder();
        sb.AppendLine("# Workspace Context (auto-generated)");
        sb.AppendLine($"Generated: {DateTime.Now:yyyy-MM-dd}");
        sb.AppendLine();

        // 1. 프로젝트 기본 정보
        var buildSystem = DetectBuildSystem(workFolder);
        var extDist = GetExtensionDistribution(workFolder, ct);
        var primaryLang = extDist.FirstOrDefault();

        sb.AppendLine("## Project");
        var projectName = Path.GetFileName(workFolder);
        sb.AppendLine($"- Name: {projectName}");
        if (buildSystem != null)
            sb.AppendLine($"- Build System: {buildSystem}");
        if (primaryLang.Key != null)
            sb.AppendLine($"- Primary Language: {GetLanguageName(primaryLang.Key)} ({primaryLang.Key}: {primaryLang.Value} files)");

        // Git 정보
        var gitInfo = await GetGitInfoAsync(workFolder, ct).ConfigureAwait(false);
        if (gitInfo.Branch != null)
            sb.AppendLine($"- Git Branch: {gitInfo.Branch}");
        if (gitInfo.Remote != null)
            sb.AppendLine($"- Git Remote: {gitInfo.Remote}");
        sb.AppendLine();

        // 2. 디렉토리 구조
        sb.AppendLine("## Structure");
        var tree = BuildDirectoryTree(workFolder, MaxDepth);
        foreach (var line in tree.Take(30)) // 최대 30줄
            sb.AppendLine(line);
        sb.AppendLine();

        // 3. 확장자 분포
        if (extDist.Count > 0)
        {
            sb.AppendLine("## File Distribution");
            sb.AppendLine(string.Join(", ", extDist.Take(10).Select(kv => $"{kv.Key}: {kv.Value}")));
            sb.AppendLine();
        }

        var languageSnapshot = BuildLanguageSnapshot(extDist);
        if (languageSnapshot.Count > 0)
        {
            sb.AppendLine("## Language Snapshot");
            foreach (var line in languageSnapshot)
                sb.AppendLine($"- {line}");
            sb.AppendLine();
        }

        // 4. 기존 컨텍스트 파일 감지
        var workflowGuidance = BuildLanguageWorkflow(extDist);
        if (workflowGuidance.Count > 0)
        {
            sb.AppendLine("## Language Workflow");
            foreach (var line in workflowGuidance)
                sb.AppendLine($"- {line}");
            sb.AppendLine();
        }

        if (string.Equals(primaryLang.Key, ".sql", StringComparison.OrdinalIgnoreCase) ||
            extDist.Any(entry => string.Equals(entry.Key, ".sql", StringComparison.OrdinalIgnoreCase) && entry.Value >= 3))
        {
            sb.AppendLine("## SQL Review Focus");
            sb.AppendLine("- Classify each script as migration, seed, reporting query, or operational patch before execution.");
            sb.AppendLine("- Review destructive DDL, broad UPDATE/DELETE statements, transaction scope, and dependency order.");
            sb.AppendLine("- Validate scripts in a disposable database and capture rollback notes for production changes.");
            sb.AppendLine();
        }

        var contextFiles = DetectContextFiles(workFolder);
        if (contextFiles.Count > 0)
        {
            sb.AppendLine("## Existing Context Files");
            foreach (var cf in contextFiles)
                sb.AppendLine($"- {cf}");
            sb.AppendLine();
        }

        // 5. README 요약
        var agentContextSummary = DetectAgentContextSummary(workFolder);
        if (agentContextSummary.Count > 0)
        {
            sb.AppendLine("## Agent Context");
            foreach (var line in agentContextSummary)
                sb.AppendLine($"- {line}");
            sb.AppendLine();
        }

        var keyManifests = DetectKeyManifests(workFolder);
        if (keyManifests.Count > 0)
        {
            sb.AppendLine("## Key Manifests");
            foreach (var line in keyManifests)
                sb.AppendLine($"- {line}");
            sb.AppendLine();
        }

        var readmeSummary = ExtractReadmeSummary(workFolder);
        if (readmeSummary != null)
        {
            sb.AppendLine("## README Summary");
            sb.AppendLine(readmeSummary);
            sb.AppendLine();
        }

        var content = sb.ToString().TrimEnd();

        // 파일 저장
        try
        {
            var path = Path.Combine(workFolder, ContextFileName);
            await File.WriteAllTextAsync(path, content, ct).ConfigureAwait(false);
        }
        catch
        {
            // 저장 실패는 무시 — 읽기 전용 폴더 등
        }

        return content;
    }

    /// <summary>
    /// 기존 .ax-context.md를 읽습니다. 없으면 null.
    /// </summary>
    public static string? LoadContext(string? workFolder)
    {
        if (string.IsNullOrEmpty(workFolder)) return null;
        var path = Path.Combine(workFolder, ContextFileName);
        if (!File.Exists(path)) return null;

        try
        {
            var content = File.ReadAllText(path);
            return content.Length > MaxContextChars
                ? content[..MaxContextChars] + "\n...(truncated)"
                : content;
        }
        catch { return null; }
    }

    internal static IReadOnlyList<string> DetectLanguageWorkflowHints(
        string? workFolder,
        string? preferredLanguage = null,
        int maxLanguages = 3)
    {
        if (string.IsNullOrWhiteSpace(workFolder) || !Directory.Exists(workFolder))
            return [];

        var extDist = GetExtensionDistribution(workFolder, CancellationToken.None);
        return CodeLanguageCatalog.BuildWorkspaceWorkflowSummaries(
            extDist.Select(x => x.Key),
            preferredLanguage,
            maxLanguages);
    }

    // ════════════════════════════════════════════════════════════
    //  분석 로직
    // ════════════════════════════════════════════════════════════

    private static string? DetectBuildSystem(string folder)
    {
        var checks = new (string Pattern, string Name)[]
        {
            ("*.sln", ".NET (Solution)"),
            ("*.csproj", ".NET"),
            ("package.json", "Node.js"),
            ("Cargo.toml", "Rust"),
            ("go.mod", "Go"),
            ("pom.xml", "Java (Maven)"),
            ("build.gradle", "Java (Gradle)"),
            ("pyproject.toml", "Python"),
            ("requirements.txt", "Python"),
            ("Makefile", "Make"),
            ("CMakeLists.txt", "CMake"),
        };

        foreach (var (pattern, name) in checks)
        {
            try
            {
                if (Directory.GetFiles(folder, pattern, SearchOption.TopDirectoryOnly).Length > 0)
                    return name;
            }
            catch { /* 무시 */ }
        }

        return null;
    }

    private static List<KeyValuePair<string, int>> GetExtensionDistribution(
        string folder, CancellationToken ct)
    {
        var counts = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);

        try
        {
            foreach (var file in Directory.EnumerateFiles(folder, "*", new EnumerationOptions
            {
                RecurseSubdirectories = true,
                IgnoreInaccessible = true,
                MaxRecursionDepth = 5,
            }))
            {
                ct.ThrowIfCancellationRequested();

                // 경로 세그먼트 단위로 SkipDirs 검사 (정확한 디렉토리명 매칭)
                var dir = Path.GetDirectoryName(file) ?? "";
                if (ShouldSkipPath(dir))
                    continue;

                var ext = Path.GetExtension(file);
                if (string.IsNullOrEmpty(ext) || ext.Length > 8) continue;

                counts.TryGetValue(ext, out var count);
                counts[ext] = count + 1;
            }
        }
        catch (OperationCanceledException) { throw; }
        catch { /* 무시 */ }

        return counts.OrderByDescending(kv => kv.Value).ToList();
    }

    private static List<string> BuildDirectoryTree(string root, int maxDepth)
    {
        var result = new List<string>();
        BuildTreeRecursive(root, root, 0, maxDepth, result);
        return result;
    }

    private static void BuildTreeRecursive(string root, string current, int depth, int maxDepth, List<string> result)
    {
        if (depth >= maxDepth || result.Count >= 30) return;

        IEnumerable<string> dirs;
        try { dirs = Directory.GetDirectories(current); }
        catch { return; }

        foreach (var dir in dirs.OrderBy(d => d))
        {
            if (result.Count >= 30) break;

            var name = Path.GetFileName(dir);
            if (SkipDirs.Contains(name)) continue;

            // 심링크/junction 무한루프 방지: 속성 검사
            try
            {
                var attrs = File.GetAttributes(dir);
                if (attrs.HasFlag(FileAttributes.ReparsePoint))
                    continue;
            }
            catch { continue; }

            // TopDirectoryOnly로 제한하여 대규모 디렉토리 탐색 방지
            int fileCount;
            try
            {
                fileCount = Directory.EnumerateFiles(dir, "*", new EnumerationOptions
                {
                    RecurseSubdirectories = true,
                    IgnoreInaccessible = true,
                    MaxRecursionDepth = 3,
                }).Take(10_000).Count(); // 최대 10K개만 카운트
            }
            catch { fileCount = 0; }

            var indent = new string(' ', depth * 2);
            var relativePath = Path.GetRelativePath(root, dir).Replace('\\', '/');
            result.Add($"{indent}{relativePath}/ ({fileCount}{(fileCount >= 10_000 ? "+" : "")} files)");

            BuildTreeRecursive(root, dir, depth + 1, maxDepth, result);
        }
    }

    private static string? ExtractReadmeSummary(string folder)
    {
        var names = new[] { "README.md", "readme.md", "README", "README.txt" };
        foreach (var name in names)
        {
            var path = Path.Combine(folder, name);
            if (!File.Exists(path)) continue;

            try
            {
                var text = File.ReadAllText(path);
                if (text.Length > MaxReadmeChars)
                    text = text[..MaxReadmeChars];

                // 첫 번째 단락 추출 (제목 제외)
                var lines = text.Split('\n');
                var paragraphLines = new List<string>();
                var foundContent = false;

                foreach (var line in lines)
                {
                    var trimmed = line.Trim();
                    if (trimmed.StartsWith('#') && !foundContent) continue; // 제목 건너뛰기
                    if (string.IsNullOrWhiteSpace(trimmed))
                    {
                        if (foundContent && paragraphLines.Count > 0) break;
                        continue;
                    }
                    foundContent = true;
                    paragraphLines.Add(trimmed);
                }

                if (paragraphLines.Count > 0)
                    return string.Join(" ", paragraphLines);
            }
            catch { /* 무시 */ }
        }

        return null;
    }

    private static List<string> DetectContextFiles(string folder)
    {
        var files = new List<string>();
        var names = new[] { "AGENTS.md", "AX.md", "CLAUDE.md", ".clinerules", ".ax-rules" };
        foreach (var name in names)
        {
            if (File.Exists(Path.Combine(folder, name)))
                files.Add(name);
        }

        var axDir = Path.Combine(folder, ".ax");
        if (Directory.Exists(axDir))
        {
            try
            {
                var rulesDir = Path.Combine(axDir, "rules");
                if (Directory.Exists(rulesDir))
                {
                    var ruleFiles = Directory.GetFiles(rulesDir, "*.md");
                    if (ruleFiles.Length > 0)
                        files.Add($".ax/rules/ ({ruleFiles.Length} files)");
                }
            }
            catch { /* 무시 */ }
        }

        return files;
    }

    private static List<string> DetectAgentContextSummary(string folder)
    {
        var lines = new List<string>();

        try
        {
            var claudeSkillsDir = Path.Combine(folder, ".claude", "skills");
            if (Directory.Exists(claudeSkillsDir))
            {
                var skillFiles = Directory.GetFiles(claudeSkillsDir, "SKILL.md", SearchOption.AllDirectories);
                if (skillFiles.Length > 0)
                    lines.Add($".claude/skills 호환 스킬 {skillFiles.Length}개 감지");
            }
        }
        catch { }

        try
        {
            var axRulesDir = Path.Combine(folder, ".ax", "rules");
            if (Directory.Exists(axRulesDir))
            {
                var ruleFiles = Directory.GetFiles(axRulesDir, "*.md", SearchOption.TopDirectoryOnly);
                if (ruleFiles.Length > 0)
                    lines.Add($".ax/rules 규칙 {ruleFiles.Length}개 감지");
            }
        }
        catch { }

        try
        {
            var memoryFile = Path.Combine(folder, "AXMEMORY.md");
            if (File.Exists(memoryFile))
                lines.Add("AXMEMORY.md 메모리 파일 감지");
        }
        catch { }

        return lines;
    }

    private static List<string> DetectKeyManifests(string folder)
    {
        var manifests = new List<string>();
        var patterns = new (string Pattern, string Label)[]
        {
            ("*.sln", "Solution"),
            ("*.csproj", ".NET project"),
            ("package.json", "Node package"),
            ("pyproject.toml", "Python project"),
            ("requirements.txt", "Python requirements"),
            ("Cargo.toml", "Rust package"),
            ("go.mod", "Go module"),
            ("pom.xml", "Maven project"),
            ("build.gradle", "Gradle build"),
        };

        foreach (var (pattern, label) in patterns)
        {
            try
            {
                var matches = Directory.GetFiles(folder, pattern, SearchOption.TopDirectoryOnly)
                    .Select(Path.GetFileName)
                    .Where(name => !string.IsNullOrWhiteSpace(name))
                    .Cast<string>()
                    .Take(3)
                    .ToList();
                if (matches.Count > 0)
                    manifests.Add($"{label}: {string.Join(", ", matches)}");
            }
            catch { }
        }

        return manifests;
    }

    private static List<string> BuildLanguageSnapshot(List<KeyValuePair<string, int>> extDist)
        => extDist
            .Where(kv => kv.Value > 0)
            .Select(kv => new { Language = GetLanguageName(kv.Key), kv.Value })
            .GroupBy(x => x.Language, StringComparer.OrdinalIgnoreCase)
            .Select(group => new { Language = group.Key, Count = group.Sum(item => item.Value) })
            .OrderByDescending(x => x.Count)
            .Take(6)
            .Select(x => $"{x.Language}: {x.Count} file(s)")
            .ToList();

    private static List<string> BuildLanguageWorkflow(List<KeyValuePair<string, int>> extDist)
        => CodeLanguageCatalog.BuildWorkspaceWorkflowSummaries(extDist.Select(x => x.Key)).ToList();

    private static async Task<(string? Branch, string? Remote)> GetGitInfoAsync(
        string folder, CancellationToken ct)
    {
        if (!Directory.Exists(Path.Combine(folder, ".git")))
            return (null, null);

        string? branch = null;
        string? remote = null;

        try
        {
            branch = await RunGitAsync(folder, "rev-parse --abbrev-ref HEAD", ct).ConfigureAwait(false);
            remote = await RunGitAsync(folder, "remote get-url origin", ct).ConfigureAwait(false);
        }
        catch { /* Git 없거나 실패 */ }

        return (branch?.Trim(), remote?.Trim());
    }

    private static async Task<string?> RunGitAsync(string folder, string args, CancellationToken ct)
    {
        try
        {
            using var process = new Process();
            process.StartInfo = new ProcessStartInfo
            {
                FileName = "git",
                Arguments = args,
                WorkingDirectory = folder,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                UseShellExecute = false,
                CreateNoWindow = true,
            };
            process.Start();
            var output = await process.StandardOutput.ReadToEndAsync(ct).ConfigureAwait(false);
            await process.WaitForExitAsync(ct).ConfigureAwait(false);
            return process.ExitCode == 0 ? output.Trim() : null;
        }
        catch { return null; }
    }

    /// <summary>경로의 각 디렉토리 세그먼트가 SkipDirs에 해당하는지 검사.</summary>
    private static bool ShouldSkipPath(string dirPath)
    {
        var span = dirPath.AsSpan();
        while (span.Length > 0)
        {
            var sepIdx = span.IndexOfAny(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
            var segment = sepIdx >= 0 ? span[..sepIdx] : span;
            if (segment.Length > 0 && SkipDirs.Contains(segment.ToString()))
                return true;
            if (sepIdx < 0) break;
            span = span[(sepIdx + 1)..];
        }
        return false;
    }

    private static string GetLanguageName(string ext) => ext.ToLowerInvariant() switch
    {
        ".cs" => "C#",
        ".ts" or ".tsx" => "TypeScript",
        ".js" or ".jsx" => "JavaScript",
        ".py" => "Python",
        ".rs" => "Rust",
        ".go" => "Go",
        ".java" => "Java",
        ".cpp" or ".cc" or ".cxx" => "C++",
        ".c" => "C",
        ".rb" => "Ruby",
        ".php" => "PHP",
        ".swift" => "Swift",
        ".kt" => "Kotlin",
        ".xaml" => "XAML",
        ".html" or ".htm" => "HTML",
        ".css" => "CSS",
        _ => ext.TrimStart('.').ToUpperInvariant(),
    };
}