using System.IO;
using System.Text;
using System.Text.Json;

namespace AxCopilot.Services.Agent;

/// <summary>
/// CSV (.csv) 파일을 생성하는 내장 스킬.
/// LLM이 헤더와 데이터 행을 전달하면 CSV 파일을 생성합니다.
/// </summary>
public class CsvSkill : IAgentTool
{
    public string Name => "csv_create";
    public string Description => "Create a CSV (.csv) file with structured data. Provide headers and rows as JSON arrays.";

    public ToolParameterSchema Parameters => new()
    {
        Properties = new()
        {
            ["path"] = new() { Type = "string", Description = "Output file path (.csv). Relative to work folder." },
            ["headers"] = new() { Type = "array", Description = "Column headers as JSON array of strings.", Items = new() { Type = "string" } },
            ["rows"] = new() { Type = "array", Description = "Data rows as JSON array of arrays.", Items = new() { Type = "array", Items = new() { Type = "string" } } },
            ["encoding"] = new() { Type = "string", Description = "File encoding: 'utf-8' (default) or 'euc-kr'." },
        },
        Required = ["path", "headers", "rows"]
    };

    public async Task<ToolResult> ExecuteAsync(JsonElement args, AgentContext context, CancellationToken ct)
    {
        var path = args.GetProperty("path").GetString() ?? "";
        var encodingName = args.TryGetProperty("encoding", out var enc) ? enc.GetString() ?? "utf-8" : "utf-8";

        var fullPath = FileReadTool.ResolvePath(path, context.WorkFolder);
        if (context.ActiveTab == "Cowork") fullPath = AgentContext.EnsureTimestampedPath(fullPath);
        if (!fullPath.EndsWith(".csv", StringComparison.OrdinalIgnoreCase))
            fullPath += ".csv";

        if (!context.IsPathAllowed(fullPath))
            return ToolResult.Fail($"경로 접근 차단: {fullPath}");

        if (!await context.CheckWritePermissionAsync(Name, fullPath))
            return ToolResult.Fail($"쓰기 권한 거부: {fullPath}");

        try
        {
            var headers = args.GetProperty("headers");
            var rows = args.GetProperty("rows");

            var dir = Path.GetDirectoryName(fullPath);
            if (!string.IsNullOrEmpty(dir)) Directory.CreateDirectory(dir);

            Encoding fileEncoding;
            try { fileEncoding = Encoding.GetEncoding(encodingName); }
            catch { fileEncoding = new UTF8Encoding(true); }

            var sb = new StringBuilder();

            // 헤더
            var headerValues = new List<string>();
            foreach (var h in headers.EnumerateArray())
                headerValues.Add(EscapeCsvField(h.GetString() ?? ""));
            sb.AppendLine(string.Join(",", headerValues));

            // 데이터
            int rowCount = 0;
            foreach (var row in rows.EnumerateArray())
            {
                var fields = new List<string>();
                foreach (var cell in row.EnumerateArray())
                    fields.Add(EscapeCsvField(cell.ToString()));
                sb.AppendLine(string.Join(",", fields));
                rowCount++;
            }

            await File.WriteAllTextAsync(fullPath, sb.ToString(), fileEncoding, ct);

            return ToolResult.Ok(
                $"CSV 파일 생성 완료: {fullPath}\n열: {headerValues.Count}, 행: {rowCount}, 인코딩: {encodingName}",
                fullPath);
        }
        catch (Exception ex)
        {
            return ToolResult.Fail($"CSV 생성 실패: {ex.Message}");
        }
    }

    private static string EscapeCsvField(string field)
    {
        if (field.Contains(',') || field.Contains('"') || field.Contains('\n') || field.Contains('\r'))
            return $"\"{field.Replace("\"", "\"\"")}\"";
        return field;
    }
}