using System.Text.RegularExpressions;

namespace MeetingAssistant;

internal static class AgentFileToolContent
{
    public static string ReadLines(string content, int? from = null, int? to = null, int? tail = null)
    {
        if (!from.HasValue && !to.HasValue)
        {
            return tail.HasValue
                ? TailLines(content, Math.Clamp(tail.Value, 1, 2000))
                : content;
        }

        var lines = SplitLines(content);
        if (lines.Count == 0)
        {
            return "";
        }

        var start = Math.Clamp((from ?? 1) - 1, 0, lines.Count - 1);
        var end = Math.Clamp((to ?? lines.Count) - 1, 0, lines.Count - 1);
        if (end < start)
        {
            return "";
        }

        return string.Join('\n', lines.GetRange(start, end - start + 1));
    }

    public static string TailLines(string content, int count)
    {
        var lines = SplitLines(content);
        if (lines.Count > 0 && lines[^1].Length == 0)
        {
            lines.RemoveAt(lines.Count - 1);
        }

        if (lines.Count <= count)
        {
            return string.Join('\n', lines);
        }

        return string.Join('\n', lines.GetRange(lines.Count - count, count));
    }

    public static string ApplyLineEdit(
        string existingContent,
        string replacementContent,
        AgentFileEditMode editMode)
    {
        if (editMode.Kind == AgentFileEditKind.Overwrite)
        {
            return replacementContent;
        }

        if (editMode.Kind == AgentFileEditKind.Append)
        {
            return AppendContent(existingContent, replacementContent);
        }

        var lines = SplitLines(existingContent);
        var replacementLines = SplitLines(replacementContent);
        if (editMode.Kind == AgentFileEditKind.Insert)
        {
            var insertIndex = Math.Clamp(editMode.Insert!.Value - 1, 0, lines.Count);
            lines.InsertRange(insertIndex, replacementLines);
            return string.Join('\n', lines);
        }

        var startIndex = Math.Clamp(editMode.From!.Value - 1, 0, lines.Count);
        var endIndexExclusive = Math.Clamp(editMode.To!.Value, 0, lines.Count);
        if (endIndexExclusive < startIndex)
        {
            endIndexExclusive = startIndex;
        }

        lines.RemoveRange(startIndex, endIndexExclusive - startIndex);
        lines.InsertRange(startIndex, replacementLines);
        return string.Join('\n', lines);
    }

    public static async Task WriteFileContentAsync(
        string filePath,
        string content,
        AgentFileEditMode editMode)
    {
        if (editMode.Kind == AgentFileEditKind.Overwrite)
        {
            await File.WriteAllTextAsync(filePath, content);
            return;
        }

        if (editMode.Kind == AgentFileEditKind.Append)
        {
            var existing = File.Exists(filePath)
                ? await File.ReadAllTextAsync(filePath)
                : "";
            await File.WriteAllTextAsync(filePath, AppendContent(existing, content));
            return;
        }

        var existingContent = File.Exists(filePath)
            ? await File.ReadAllTextAsync(filePath)
            : "";
        await File.WriteAllTextAsync(filePath, ApplyLineEdit(existingContent, content, editMode));
    }

    public static string AppendContent(string existingContent, string content)
    {
        if (string.IsNullOrEmpty(existingContent))
        {
            return content;
        }

        if (string.IsNullOrEmpty(content))
        {
            return existingContent;
        }

        var separator = existingContent.EndsWith('\n') || existingContent.EndsWith('\r')
            ? ""
            : "\n";
        return existingContent + separator + content;
    }

    public static List<string> SplitLines(string content)
    {
        if (content.Length == 0)
        {
            return [];
        }

        return content
            .Replace("\r\n", "\n", StringComparison.Ordinal)
            .Replace('\r', '\n')
            .Split('\n')
            .ToList();
    }

    public static bool IsWithinDirectory(string directory, string path)
    {
        var normalizedDirectory = Path.GetFullPath(directory)
            .TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar) + Path.DirectorySeparatorChar;
        var normalizedPath = Path.GetFullPath(path);
        return normalizedPath.StartsWith(normalizedDirectory, StringComparison.OrdinalIgnoreCase);
    }

    public static bool MatchesGlob(string path, string? pattern)
    {
        if (string.IsNullOrWhiteSpace(pattern))
        {
            return true;
        }

        var normalizedPath = ToToolPath(path);
        var normalizedPattern = ToToolPath(pattern.Trim());
        var placeholder = "\u0000";
        var regexPattern = Regex.Escape(normalizedPattern)
            .Replace("\\*\\*", placeholder, StringComparison.Ordinal)
            .Replace("\\*", "[^/]*", StringComparison.Ordinal)
            .Replace("\\?", "[^/]", StringComparison.Ordinal)
            .Replace(placeholder, ".*", StringComparison.Ordinal);
        return Regex.IsMatch(normalizedPath, $"^{regexPattern}$", RegexOptions.IgnoreCase);
    }

    public static string ToToolPath(string path)
    {
        return path.Replace(Path.DirectorySeparatorChar.ToString(), "/", StringComparison.Ordinal)
            .Replace(Path.AltDirectorySeparatorChar.ToString(), "/", StringComparison.Ordinal);
    }

    public static string SearchFiles(
        string keywords,
        IEnumerable<AgentFileSearchSource> sources,
        int maxMatches = 100,
        RegexOptions regexOptions = RegexOptions.IgnoreCase)
    {
        if (string.IsNullOrWhiteSpace(keywords))
        {
            return "";
        }

        try
        {
            var regex = new Regex(keywords, regexOptions);
            var matches = new List<string>();
            var limit = Math.Clamp(maxMatches, 1, 1000);
            foreach (var source in sources)
            {
                var lines = ReadAllLinesShared(source.Path);
                for (var index = 0; index < lines.Length; index++)
                {
                    if (regex.IsMatch(lines[index]))
                    {
                        matches.Add($"{ToToolPath(source.DisplayPath)}:{index + 1} {lines[index]}");
                    }

                    if (matches.Count >= limit)
                    {
                        return string.Join('\n', matches);
                    }
                }
            }

            return string.Join('\n', matches);
        }
        catch
        {
            return "";
        }
    }

    public static async Task<string> ReadAllTextSharedAsync(string path)
    {
        await using var stream = new FileStream(
            path,
            FileMode.Open,
            FileAccess.Read,
            FileShare.ReadWrite | FileShare.Delete,
            bufferSize: 4096,
            useAsync: true);
        using var reader = new StreamReader(stream);
        return await reader.ReadToEndAsync();
    }

    private static string[] ReadAllLinesShared(string path)
    {
        using var stream = new FileStream(
            path,
            FileMode.Open,
            FileAccess.Read,
            FileShare.ReadWrite | FileShare.Delete);
        using var reader = new StreamReader(stream);
        return SplitLines(reader.ReadToEnd()).ToArray();
    }
}

internal sealed record AgentFileSearchSource(string Path, string DisplayPath);

internal sealed record AgentFileEditMode(
    AgentFileEditKind Kind,
    int? From = null,
    int? To = null,
    int? Insert = null)
{
    public static AgentFileEditMode? Create(int? from, int? to, int? insert, bool replaceFile)
    {
        if (replaceFile && (from.HasValue || to.HasValue || insert.HasValue))
        {
            return null;
        }

        if (insert.HasValue)
        {
            return from.HasValue || to.HasValue
                ? null
                : new AgentFileEditMode(AgentFileEditKind.Insert, Insert: insert);
        }

        if (from.HasValue || to.HasValue)
        {
            return from.HasValue && to.HasValue && from.Value <= to.Value
                ? new AgentFileEditMode(AgentFileEditKind.Replace, From: from, To: to)
                : null;
        }

        return new AgentFileEditMode(replaceFile ? AgentFileEditKind.Overwrite : AgentFileEditKind.Append);
    }
}

internal enum AgentFileEditKind
{
    Append,
    Overwrite,
    Replace,
    Insert
}