using ClawdDotNet.Core.Instances;
using ClawdDotNet.Core.Mcp;

namespace ClawdDotNet.Desktop;

/// <summary>
/// #713: <c>ClawdDotNet --mcp-bridge --instance &lt;dir&gt;</c> — the instance's MCP server
/// over stdio, for a runtime that starts its MCP servers as child processes. In a sandbox
/// (#712), where there is no instance directory, <c>--socket &lt;path&gt;</c> names the
/// mounted MCP socket instead.
///
/// <para>No application is built here: no settings, no database, no engine. The bridge
/// only carries messages to the running instance over its MCP socket; everything is
/// decided there. Diagnostics go to stderr — stdout belongs to the protocol.</para>
/// </summary>
internal static class McpBridgeRun
{
    private const int ExitOk = 0;
    private const int ExitNoInstance = 2;
    private const int ExitNoToken = 5;

    public static async Task<int> RunAsync(string[] args)
    {
        var socketPath = CommandLine.ReadValue(args, McpStdioBridge.SocketArgument);
        var instancePath = CommandLine.ReadInstancePath(args);
        if (socketPath is null && (string.IsNullOrWhiteSpace(instancePath) || !Directory.Exists(instancePath)))
        {
            await Console.Error.WriteLineAsync($"Expected {CommandLine.InstanceArgument} <instance directory> or {McpStdioBridge.SocketArgument} <path>.");
            return ExitNoInstance;
        }

        var (token, problem) = McpStdioBridge.ReadToken(Environment.GetEnvironmentVariable);
        if (token is null)
        {
            await Console.Error.WriteLineAsync(problem);
            return ExitNoToken;
        }

        using var client = socketPath is not null
            ? InstanceEndpoint.CreateMcpClientForSocket(socketPath)
            : InstanceEndpoint.CreateMcpClient(instancePath!);
        using var stdin = new StreamReader(Console.OpenStandardInput());
        await using var stdout = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };

        await McpStdioBridge.RunAsync(stdin, stdout, client, token, CancellationToken.None);
        return ExitOk;
    }
}