Add register helper command for OAuth app setup

README.md

@@ -30,11 +30,35 @@ make build
 
 ## Setup
 
-1. Create a Basecamp OAuth app at https://launchpad.37signals.com/integrations
-2. Run `basecamp init` to configure credentials
-3. Run `basecamp auth` to authenticate
+### Prerequisites
 
-Configuration files (XDG Base Directory):
+During OAuth authentication, Basecamp redirects to your computer on **port 3002**. Your machine must be accessible via a URL for this to work. Use a service like:
+
+- [Tailscale](https://tailscale.com/) - Recommended for persistent access
+- [ngrok](https://ngrok.com/) - Quick setup for temporary access
+- Any reverse proxy that exposes localhost:3002
+
+### Registration
+
+1. Start your tunnel service and note the public URL (e.g., `https://myhost.tailscale.ts.net`)
+
+2. Run the registration helper to generate your OAuth app values:
+
+```bash
+basecamp register
+```
+
+This will ask for your application details and output the exact values to enter in the Basecamp registration form, including the correct redirect URI.
+
+3. Visit https://launchpad.37signals.com/integrations and register your app using the generated values
+
+4. Run `basecamp init` to configure your credentials (Client ID, Client Secret, and the same Redirect URI)
+
+5. Run `basecamp auth` to authenticate (ensure your tunnel is running on port 3002)
+
+### Configuration Files
+
+Configuration follows XDG Base Directory specification:
 - `~/.config/basecamp/config.json` - client credentials
 - `~/.local/share/basecamp/token.json` - OAuth token
 
@@ -350,6 +374,14 @@ basecamp card 44444444       # just need card_id
 
 The CLI searches current directory and parent directories for `.basecamp.yml`.
 
+## Agent Skills
+
+Install the Basecamp skill for AI coding agents (Claude Code, OpenCode, and others):
+
+```bash
+npx skills add robzolkos/basecamp-cli
+```
+
 ## Output
 
 All commands output JSON for easy parsing with `jq`:

internal/commands/register.go

@@ -0,0 +1,73 @@
+package commands
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+type RegisterCmd struct{}
+
+func (c *RegisterCmd) Run(args []string) error {
+	fmt.Fprintln(os.Stderr, "Basecamp OAuth App Registration Helper")
+	fmt.Fprintln(os.Stderr, strings.Repeat("=", 40))
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "This helper will generate the values you need to register")
+	fmt.Fprintln(os.Stderr, "your Basecamp OAuth application.")
+	fmt.Fprintln(os.Stderr)
+
+	reader := bufio.NewReader(os.Stdin)
+
+	appName := prompt(reader, "Application name", "My Basecamp CLI")
+	companyName := prompt(reader, "Company/Organization name", "")
+	websiteURL := prompt(reader, "Website URL", "https://github.com/robzolkos/basecamp-cli")
+	accessibleURL := prompt(reader, "URL where this computer is accessible (e.g., https://myhost.tailscale.ts.net)", "")
+
+	// Build redirect URI from accessible URL
+	redirectURI := buildRedirectURI(accessibleURL)
+
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, strings.Repeat("=", 60))
+	fmt.Fprintln(os.Stderr, "REGISTRATION INSTRUCTIONS")
+	fmt.Fprintln(os.Stderr, strings.Repeat("=", 60))
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "1. Visit: https://launchpad.37signals.com/integrations")
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "2. Click 'Register another application'")
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "3. Fill out the form with these values:")
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintf(os.Stderr, "   Name of your application:  %s\n", appName)
+	fmt.Fprintf(os.Stderr, "   Your company/organization: %s\n", companyName)
+	fmt.Fprintf(os.Stderr, "   Website URL:               %s\n", websiteURL)
+	fmt.Fprintf(os.Stderr, "   Redirect URI:              %s\n", redirectURI)
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "4. After registering, copy your Client ID and Client Secret")
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "5. Run 'basecamp init' and enter the credentials when prompted")
+	fmt.Fprintln(os.Stderr, "   (use the same Redirect URI shown above)")
+	fmt.Fprintln(os.Stderr)
+	fmt.Fprintln(os.Stderr, "6. Run 'basecamp auth' to authenticate")
+	fmt.Fprintln(os.Stderr, strings.Repeat("=", 60))
+
+	return PrintJSON(map[string]string{
+		"application_name": appName,
+		"company_name":     companyName,
+		"website_url":      websiteURL,
+		"redirect_uri":     redirectURI,
+		"registration_url": "https://launchpad.37signals.com/integrations",
+	})
+}
+
+func buildRedirectURI(accessibleURL string) string {
+	if accessibleURL == "" {
+		return "http://localhost:3002/callback"
+	}
+
+	// Remove trailing slash if present
+	accessibleURL = strings.TrimSuffix(accessibleURL, "/")
+
+	// Add port and callback path
+	return accessibleURL + ":3002/callback"
+}

internal/commands/root.go

@@ -14,6 +14,7 @@ type Command interface {
 }
 
 var commands = map[string]func() Command{
+	"register":              func() Command { return &RegisterCmd{} },
 	"init":                  func() Command { return &InitCmd{} },
 	"auth":                  func() Command { return &AuthCmd{} },
 	"projects":              func() Command { return &ProjectsCmd{} },
@@ -115,6 +116,7 @@ func printHelp(version string) {
 Usage: basecamp <command> [arguments] [flags]
 
 Commands:
+  register                          Generate OAuth app registration values
   init                              Configure credentials
   auth                              Authenticate with OAuth
   projects                          List all projects