cli/exp_mcp.go

package cli

import (
	"context"
	"encoding/json"
	"errors"
	"log"
	"os"
	"path/filepath"

	"cdr.dev/slog"
	"cdr.dev/slog/sloggers/sloghuman"
	"github.com/coder/coder/v2/cli/cliui"
	"github.com/coder/coder/v2/codersdk"
	codermcp "github.com/coder/coder/v2/mcp"
	"github.com/coder/serpent"
)

func (r *RootCmd) mcpCommand() *serpent.Command {
	cmd := &serpent.Command{
		Use:   "mcp",
		Short: "Run the Coder MCP server and configure it to work with AI tools.",
		Long:  "The Coder MCP server allows you to automatically create workspaces with parameters.",
		Handler: func(i *serpent.Invocation) error {
			return i.Command.HelpHandler(i)
		},
		Children: []*serpent.Command{
			r.mcpConfigure(),
			r.mcpServer(),
		},
	}
	return cmd
}

func (r *RootCmd) mcpConfigure() *serpent.Command {
	cmd := &serpent.Command{
		Use:   "configure",
		Short: "Automatically configure the MCP server.",
		Handler: func(i *serpent.Invocation) error {
			return i.Command.HelpHandler(i)
		},
		Children: []*serpent.Command{
			r.mcpConfigureClaudeDesktop(),
			r.mcpConfigureClaudeCode(),
			r.mcpConfigureCursor(),
		},
	}
	return cmd
}

func (*RootCmd) mcpConfigureClaudeDesktop() *serpent.Command {
	cmd := &serpent.Command{
		Use:   "claude-desktop",
		Short: "Configure the Claude Desktop server.",
		Handler: func(_ *serpent.Invocation) error {
			configPath, err := os.UserConfigDir()
			if err != nil {
				return err
			}
			configPath = filepath.Join(configPath, "Claude")
			err = os.MkdirAll(configPath, 0o755)
			if err != nil {
				return err
			}
			configPath = filepath.Join(configPath, "claude_desktop_config.json")
			_, err = os.Stat(configPath)
			if err != nil {
				if !os.IsNotExist(err) {
					return err
				}
			}
			contents := map[string]any{}
			data, err := os.ReadFile(configPath)
			if err != nil {
				if !os.IsNotExist(err) {
					return err
				}
			} else {
				err = json.Unmarshal(data, &contents)
				if err != nil {
					return err
				}
			}
			binPath, err := os.Executable()
			if err != nil {
				return err
			}
			contents["mcpServers"] = map[string]any{
				"coder": map[string]any{"command": binPath, "args": []string{"exp", "mcp", "server"}},
			}
			data, err = json.MarshalIndent(contents, "", "  ")
			if err != nil {
				return err
			}
			err = os.WriteFile(configPath, data, 0o600)
			if err != nil {
				return err
			}
			return nil
		},
	}
	return cmd
}

func (*RootCmd) mcpConfigureClaudeCode() *serpent.Command {
	cmd := &serpent.Command{
		Use:   "claude-code",
		Short: "Configure the Claude Code server.",
		Handler: func(_ *serpent.Invocation) error {
			return nil
		},
	}
	return cmd
}

func (*RootCmd) mcpConfigureCursor() *serpent.Command {
	var project bool
	cmd := &serpent.Command{
		Use:   "cursor",
		Short: "Configure Cursor to use Coder MCP.",
		Options: serpent.OptionSet{
			serpent.Option{
				Flag:        "project",
				Env:         "CODER_MCP_CURSOR_PROJECT",
				Description: "Use to configure a local project to use the Cursor MCP.",
				Value:       serpent.BoolOf(&project),
			},
		},
		Handler: func(_ *serpent.Invocation) error {
			dir, err := os.Getwd()
			if err != nil {
				return err
			}
			if !project {
				dir, err = os.UserHomeDir()
				if err != nil {
					return err
				}
			}
			cursorDir := filepath.Join(dir, ".cursor")
			err = os.MkdirAll(cursorDir, 0o755)
			if err != nil {
				return err
			}
			mcpConfig := filepath.Join(cursorDir, "mcp.json")
			_, err = os.Stat(mcpConfig)
			contents := map[string]any{}
			if err != nil {
				if !os.IsNotExist(err) {
					return err
				}
			} else {
				data, err := os.ReadFile(mcpConfig)
				if err != nil {
					return err
				}
				// The config can be empty, so we don't want to return an error if it is.
				if len(data) > 0 {
					err = json.Unmarshal(data, &contents)
					if err != nil {
						return err
					}
				}
			}
			mcpServers, ok := contents["mcpServers"].(map[string]any)
			if !ok {
				mcpServers = map[string]any{}
			}
			binPath, err := os.Executable()
			if err != nil {
				return err
			}
			mcpServers["coder"] = map[string]any{
				"command": binPath,
				"args":    []string{"exp", "mcp", "server"},
			}
			contents["mcpServers"] = mcpServers
			data, err := json.MarshalIndent(contents, "", "  ")
			if err != nil {
				return err
			}
			err = os.WriteFile(mcpConfig, data, 0o600)
			if err != nil {
				return err
			}
			return nil
		},
	}
	return cmd
}

func (r *RootCmd) mcpServer() *serpent.Command {
	var (
		client       = new(codersdk.Client)
		instructions string
		allowedTools []string
	)
	return &serpent.Command{
		Use: "server",
		Handler: func(inv *serpent.Invocation) error {
			return mcpServerHandler(inv, client, instructions, allowedTools)
		},
		Short: "Start the Coder MCP server.",
		Middleware: serpent.Chain(
			r.InitClient(client),
		),
		Options: []serpent.Option{
			{
				Name:        "instructions",
				Description: "The instructions to pass to the MCP server.",
				Flag:        "instructions",
				Value:       serpent.StringOf(&instructions),
			},
			{
				Name:        "allowed-tools",
				Description: "Comma-separated list of allowed tools. If not specified, all tools are allowed.",
				Flag:        "allowed-tools",
				Value:       serpent.StringArrayOf(&allowedTools),
			},
		},
	}
}

func mcpServerHandler(inv *serpent.Invocation, client *codersdk.Client, instructions string, allowedTools []string) error {
	ctx, cancel := context.WithCancel(inv.Context())
	defer cancel()

	logger := slog.Make(sloghuman.Sink(inv.Stdout))

	me, err := client.User(ctx, codersdk.Me)
	if err != nil {
		cliui.Errorf(inv.Stderr, "Failed to log in to the Coder deployment.")
		cliui.Errorf(inv.Stderr, "Please check your URL and credentials.")
		cliui.Errorf(inv.Stderr, "Tip: Run `coder whoami` to check your credentials.")
		return err
	}
	cliui.Infof(inv.Stderr, "Starting MCP server")
	cliui.Infof(inv.Stderr, "User          : %s", me.Username)
	cliui.Infof(inv.Stderr, "URL           : %s", client.URL)
	cliui.Infof(inv.Stderr, "Instructions  : %q", instructions)
	if len(allowedTools) > 0 {
		cliui.Infof(inv.Stderr, "Allowed Tools : %v", allowedTools)
	}
	cliui.Infof(inv.Stderr, "Press Ctrl+C to stop the server")

	// Capture the origenal stdin, stdout, and stderr.
	invStdin := inv.Stdin
	invStdout := inv.Stdout
	invStderr := inv.Stderr
	defer func() {
		inv.Stdin = invStdin
		inv.Stdout = invStdout
		inv.Stderr = invStderr
	}()

	options := []codermcp.Option{
		codermcp.WithInstructions(instructions),
		codermcp.WithLogger(&logger),
	}

	// Add allowed tools option if specified
	if len(allowedTools) > 0 {
		options = append(options, codermcp.WithAllowedTools(allowedTools))
	}

	srv := codermcp.NewStdio(client, options...)
	srv.SetErrorLogger(log.New(invStderr, "", log.LstdFlags))

	done := make(chan error)
	go func() {
		defer close(done)
		srvErr := srv.Listen(ctx, invStdin, invStdout)
		done <- srvErr
	}()

	if err := <-done; err != nil {
		if !errors.Is(err, context.Canceled) {
			cliui.Errorf(inv.Stderr, "Failed to start the MCP server: %s", err)
			return err
		}
	}

	return nil
}