using System.Text.Json;

namespace AxCopilot.Services.Agent;

/// <summary>
/// 환경변수 읽기·쓰기 도구.
/// 현재 프로세스 범위에서만 동작하며 시스템 환경변수는 변경하지 않습니다.
/// </summary>
public class EnvTool : IAgentTool
{
    public string Name => "env_tool";
    public string Description =>
        "Read or set environment variables (process scope only). Actions: " +
        "'get' — read an environment variable value; " +
        "'set' — set an environment variable (process scope, not permanent); " +
        "'list' — list all environment variables; " +
        "'expand' — expand %VAR% references in a string.";

    public ToolParameterSchema Parameters => new()
    {
        Properties = new()
        {
            ["action"] = new()
            {
                Type = "string",
                Description = "Action to perform",
                Enum = ["get", "set", "list", "expand"],
            },
            ["name"] = new()
            {
                Type = "string",
                Description = "Variable name (for get/set)",
            },
            ["value"] = new()
            {
                Type = "string",
                Description = "Variable value (for set) or string to expand (for expand)",
            },
            ["filter"] = new()
            {
                Type = "string",
                Description = "Filter pattern for list action (case-insensitive substring match)",
            },
        },
        Required = ["action"],
    };

    public Task<ToolResult> ExecuteAsync(JsonElement args, AgentContext context, CancellationToken ct = default)
    {
        var action = args.GetProperty("action").GetString() ?? "";

        try
        {
            return Task.FromResult(action switch
            {
                "get"    => Get(args),
                "set"    => Set(args),
                "list"   => ListVars(args),
                "expand" => Expand(args),
                _        => ToolResult.Fail($"Unknown action: {action}"),
            });
        }
        catch (Exception ex)
        {
            return Task.FromResult(ToolResult.Fail($"환경변수 오류: {ex.Message}"));
        }
    }

    private static ToolResult Get(JsonElement args)
    {
        if (!args.TryGetProperty("name", out var n))
            return ToolResult.Fail("'name' parameter is required for get action");
        var name = n.GetString() ?? "";
        var value = Environment.GetEnvironmentVariable(name);
        return value != null
            ? ToolResult.Ok($"{name}={value}")
            : ToolResult.Ok($"{name} is not set");
    }

    private static ToolResult Set(JsonElement args)
    {
        if (!args.TryGetProperty("name", out var n))
            return ToolResult.Fail("'name' parameter is required for set action");
        if (!args.TryGetProperty("value", out var v))
            return ToolResult.Fail("'value' parameter is required for set action");

        var name = n.GetString() ?? "";
        var value = v.GetString() ?? "";
        Environment.SetEnvironmentVariable(name, value, EnvironmentVariableTarget.Process);
        return ToolResult.Ok($"✓ Set {name}={value} (process scope)");
    }

    private static ToolResult ListVars(JsonElement args)
    {
        var filter = args.TryGetProperty("filter", out var f) ? f.GetString() ?? "" : "";
        var vars = Environment.GetEnvironmentVariables();
        var entries = new List<string>();

        foreach (System.Collections.DictionaryEntry entry in vars)
        {
            var key = entry.Key?.ToString() ?? "";
            var val = entry.Value?.ToString() ?? "";
            if (!string.IsNullOrEmpty(filter) &&
                !key.Contains(filter, StringComparison.OrdinalIgnoreCase) &&
                !val.Contains(filter, StringComparison.OrdinalIgnoreCase))
                continue;

            // 긴 값은 자르기
            if (val.Length > 120) val = val[..120] + "...";
            entries.Add($"{key}={val}");
        }

        entries.Sort(StringComparer.OrdinalIgnoreCase);
        var result = $"Environment variables ({entries.Count}):\n" + string.Join("\n", entries);
        if (result.Length > 8000) result = result[..8000] + "\n... (truncated)";
        return ToolResult.Ok(result);
    }

    private static ToolResult Expand(JsonElement args)
    {
        if (!args.TryGetProperty("value", out var v))
            return ToolResult.Fail("'value' parameter is required for expand action");
        var input = v.GetString() ?? "";
        var expanded = Environment.ExpandEnvironmentVariables(input);
        return ToolResult.Ok(expanded);
    }
}