// SchemaMcp: a read-only MCP server that shows Claude Code the application's PostgreSQL schema.
// Transport: stdio. stdout carries the protocol, so every log line goes to stderr.
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Npgsql;

// The connection string comes from the environment, never from a file in the repository.
// Point it at a role that can only read (see schema.sql): that role is the real safety net.
var connectionString = Environment.GetEnvironmentVariable("SCHEMA_MCP_CONNECTION");
if (string.IsNullOrWhiteSpace(connectionString))
{
    Console.Error.WriteLine("SchemaMcp: set SCHEMA_MCP_CONNECTION to a connection string for a read-only role.");
    return 1;
}

var builder = Host.CreateApplicationBuilder(args);
builder.Logging.AddConsole(options => options.LogToStandardErrorThreshold = LogLevel.Trace);

builder.Services.AddSingleton(NpgsqlDataSource.Create(connectionString));
builder.Services
    .AddMcpServer(options => options.ServerInstructions =
        "Read-only access to the application's PostgreSQL database: list the tables, describe one " +
        "table (columns, keys, indexes), or run a single SELECT with a row cap.")
    .WithStdioServerTransport()
    .WithTools<SchemaTools>();

await builder.Build().RunAsync();
return 0;