// Command nexus is the MCP Nexus control plane binary.
//
// Subcommands:
//
//	nexus serve      Run the aggregating MCP gateway (the control plane).
//	nexus connect    Bridge a local stdio agent to a Nexus gateway endpoint.
//	nexus demo-mcp   Run the built-in demo MCP server over stdio.
//	nexus version    Print version information.
package main

import (
	"context"
	"flag"
	"fmt"
	"log/slog"
	"os"
	"os/signal"
	"syscall"

	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/app"
	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/bridge"
	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/config"
	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/demomcp"
	"gitea.thetempleofdoom.com/drjones/mcp-gateway-nexus/internal/version"
)

func main() {
	if len(os.Args) < 2 {
		usage()
		os.Exit(2)
	}
	cmd := os.Args[1]
	args := os.Args[2:]

	var err error
	switch cmd {
	case "serve":
		err = runServe(args)
	case "connect":
		err = runConnect(args)
	case "demo-mcp":
		err = demomcp.Run(os.Stdin, os.Stdout)
	case "version", "--version", "-v":
		fmt.Println("mcp-nexus", version.String())
	case "help", "-h", "--help":
		usage()
	default:
		fmt.Fprintf(os.Stderr, "unknown command %q\n\n", cmd)
		usage()
		os.Exit(2)
	}
	if err != nil {
		fmt.Fprintln(os.Stderr, "error:", err)
		os.Exit(1)
	}
}

func runServe(args []string) error {
	fs := flag.NewFlagSet("serve", flag.ExitOnError)
	cfgPath := fs.String("config", "config.yaml", "path to config file")
	logFormat := fs.String("log", "text", "log format: text|json")
	_ = fs.Parse(args)

	log := newLogger(*logFormat)

	cfg, err := config.Load(*cfgPath)
	if err != nil {
		return err
	}
	if cfg.Gateway.Version == "" {
		cfg.Gateway.Version = version.Version
	}

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	return app.Serve(ctx, cfg, log)
}

func runConnect(args []string) error {
	fs := flag.NewFlagSet("connect", flag.ExitOnError)
	url := fs.String("url", "http://localhost:8080/mcp", "Nexus gateway MCP endpoint")
	_ = fs.Parse(args)

	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	return bridge.Run(ctx, *url, os.Stdin, os.Stdout)
}

func newLogger(format string) *slog.Logger {
	// Logs go to stderr so stdio-transport subcommands keep stdout clean.
	var h slog.Handler
	if format == "json" {
		h = slog.NewJSONHandler(os.Stderr, nil)
	} else {
		h = slog.NewTextHandler(os.Stderr, nil)
	}
	return slog.New(h)
}

func usage() {
	fmt.Fprint(os.Stderr, `mcp-nexus — the control plane for MCP

Usage:
  nexus serve      [-config config.yaml] [-log text|json]   Run the aggregating MCP gateway
  nexus connect    [-url http://localhost:8080/mcp]         Bridge a local stdio agent to a gateway
  nexus demo-mcp                                            Run the built-in demo MCP server (stdio)
  nexus version                                             Print version
`)
}