feat: interactive auth method selection with API token validation

- Add GetToken() as unified auth entry point with method selection
- Prompt [1] OAuth / [2] API token on first launch, save choice
- Validate API tokens against /api/v1/users/self before saving
- Check saved API token validity on reuse; fallback to re-prompt on failure
- Add HTTP status check to GetCourseInfo and GetEnrolledCourses
- Remove --api flag, auth method is now persistent and interactive

README.md

@@ -31,15 +31,11 @@ go build -o canvasarchiver ./cmd/canvasarchiver
     ./canvasarchiver -vo
     ```
 
-   Or to use a manually generated Canvas API token:
+2. On first run, you'll be prompted to choose an authentication method:
-   ```bash
+   - **[1] Login via browser (OAuth)**: Visit the provided URL, authorize, and paste the code
-   ./canvasarchiver --api
+   - **[2] Use Canvas API token**: Enter a manually generated API token (e.g. `12230~...`)
-   ```
 
-2. On first run, you'll be prompted to authenticate:
+   The choice is saved and reused on subsequent runs.
-   - Visit the provided OAuth URL
-   - Authorize the application
-   - Copy the authorization code back to the terminal
 
 3. Enter your Course ID when prompted (or use `-me` to download all enrolled courses)
 
@@ -58,8 +54,6 @@ go build -o canvasarchiver ./cmd/canvasarchiver
 | `-vo` | Videos only — scan recordings and all module video items, download everything flat into one directory; skips regular files |
 | `-me` | Download all enrolled courses |
 | `-n` | Prefix modules with order numbers `[1]`, `[2]`, etc. |
-| `--api` | Use a manually generated Canvas API token instead of OAuth |
-
 
 ## Configuration
 
@@ -72,9 +66,7 @@ The following constants can be modified in `internal/config/config.go`:
 
 ## Authentication
 
-Credentials are stored in `credentials.json` after the first successful login. The refresh token is automatically used for subsequent runs.
+Credentials are stored in `credentials.json` after the first successful authentication. The chosen method is remembered for subsequent runs — OAuth refresh tokens are automatically refreshed, and API tokens are validated before saving.
-
-With `--api`, enter a manually generated Canvas API token on first use. It is saved to `credentials.json` and reused on later `--api` runs.
 
 ## Notes
 

cmd/canvasarchiver/main.go

@@ -17,19 +17,12 @@ func main() {
 	videosOnly := flag.Bool("vo", false, "Videos only mode - download only Panopto videos to a single directory")
 	me := flag.Bool("me", false, "Download all enrolled courses")
 	moduleNumbers := flag.Bool("n", false, "Prefix modules with order numbers [1], [2], etc.")
-	apiToken := flag.Bool("api", false, "Use a manually generated Canvas API token instead of OAuth")
 	flag.Parse()
 
 	httpClient := &http.Client{}
 
 	authenticator := auth.NewAuthenticator(httpClient)
-	var accessToken string
+	accessToken, err := authenticator.GetToken()
-	var err error
-	if *apiToken {
-		accessToken, err = authenticator.GetAPIToken()
-	} else {
-		accessToken, err = authenticator.GetAccessToken()
-	}
 	if err != nil {
 		fmt.Printf("Authentication failed: %v\n", err)
 		return

internal/auth/auth.go

@@ -27,7 +27,32 @@ func NewAuthenticator(client *http.Client) *Authenticator {
 	}
 }
 
-func (a *Authenticator) GetAccessToken() (string, error) {
+func (a *Authenticator) GetToken() (string, error) {
+	creds, err := LoadCredentials()
+	if err == nil && creds.AuthMethod != "" {
+		switch creds.AuthMethod {
+		case "api":
+			token := strings.TrimSpace(creds.APIToken)
+			if token == "" {
+				return a.promptMethod()
+			}
+			fmt.Print("[*] Validating saved API token... ")
+			if err := a.validateAPIToken(token); err != nil {
+				fmt.Println("FAILED")
+				fmt.Printf("[!] %v\n", err)
+				SaveCredentials(&models.Credentials{})
+				return a.promptMethod()
+			}
+			fmt.Println("OK")
+			return token, nil
+		case "oauth":
+			return a.refreshOrLogin()
+		}
+	}
+	return a.promptMethod()
+}
+
+func (a *Authenticator) refreshOrLogin() (string, error) {
 	creds, err := LoadCredentials()
 	if err != nil {
 		return a.login()
@@ -52,36 +77,66 @@ func (a *Authenticator) GetAccessToken() (string, error) {
 	return tr.AccessToken, nil
 }
 
-func (a *Authenticator) GetAPIToken() (string, error) {
+func (a *Authenticator) promptMethod() (string, error) {
-	creds, err := LoadCredentials()
+	fmt.Println("Select authentication method:")
-	if err == nil && strings.TrimSpace(creds.APIToken) != "" {
+	fmt.Println("  [1] Login via browser (OAuth)")
-		fmt.Println("[*] Reusing saved API token...")
+	fmt.Println("  [2] Use Canvas API token")
-		return strings.TrimSpace(creds.APIToken), nil
+	fmt.Print("Choice (1/2): ")
+	input, err := bufio.NewReader(os.Stdin).ReadString('\n')
+	if err != nil && err != io.EOF {
+		return "", err
+	}
+	switch strings.TrimSpace(input) {
+	case "2":
+		return a.setupAPIToken()
+	default:
+		return a.login()
 	}
-	if err != nil {
-		creds = &models.Credentials{}
 }
 
+func (a *Authenticator) setupAPIToken() (string, error) {
 	fmt.Print("Enter Canvas API token: ")
 	token, err := bufio.NewReader(os.Stdin).ReadString('\n')
 	if err != nil && err != io.EOF {
 		return "", err
 	}
-
 	token = strings.TrimSpace(token)
 	if token == "" {
 		return "", fmt.Errorf("empty API token")
 	}
 
-	creds.APIToken = token
+	fmt.Print("[*] Validating API token... ")
-	if err := SaveCredentials(creds); err != nil {
+	if err := a.validateAPIToken(token); err != nil {
+		fmt.Println("FAILED")
 		return "", err
 	}
+	fmt.Println("OK")
 
+	if err := SaveCredentials(&models.Credentials{
+		AuthMethod: "api",
+		APIToken:   token,
+	}); err != nil {
+		return "", err
+	}
 	fmt.Println("[+] API token saved.")
 	return token, nil
 }
 
+func (a *Authenticator) validateAPIToken(token string) error {
+	req, _ := http.NewRequest("GET", config.BaseURL+"/api/v1/users/self", nil)
+	req.Header.Set("Authorization", "Bearer "+token)
+	resp, err := a.HTTPClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		body, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("invalid token: %d %s", resp.StatusCode, strings.TrimSpace(string(body)))
+	}
+	return nil
+}
+
 func (a *Authenticator) login() (string, error) {
 	codeVerifier, codeChallenge, err := generatePKCEPair()
 	if err != nil {
@@ -211,6 +266,7 @@ func SaveRefreshToken(refreshToken string) error {
 		creds = &models.Credentials{}
 	}
 	creds.RefreshToken = refreshToken
+	creds.AuthMethod = "oauth"
 	return SaveCredentials(creds)
 }
 

internal/canvas/client.go

@@ -16,6 +16,13 @@ import (
 	"git.directme.in/Joren/CanvasArchiver/internal/utils"
 )
 
+func checkAPIResponse(resp *http.Response) error {
+	if resp.StatusCode < 300 {
+		return nil
+	}
+	return fmt.Errorf("API error: %d", resp.StatusCode)
+}
+
 type Client struct {
 	HTTPClient      *http.Client
 	AccessToken     string
@@ -48,6 +55,10 @@ func (c *Client) GetCourseInfo() error {
 	}
 	defer resp.Body.Close()
 
+	if err := checkAPIResponse(resp); err != nil {
+		return err
+	}
+
 	var course models.Course
 	json.NewDecoder(resp.Body).Decode(&course)
 
@@ -64,6 +75,10 @@ func (c *Client) GetEnrolledCourses() ([]models.Course, error) {
 	}
 	defer resp.Body.Close()
 
+	if err := checkAPIResponse(resp); err != nil {
+		return nil, err
+	}
+
 	var courses []models.Course
 	json.NewDecoder(resp.Body).Decode(&courses)
 	return courses, nil

internal/models/models.go

@@ -1,6 +1,7 @@
 package models
 
 type Credentials struct {
+	AuthMethod   string `json:"auth_method,omitempty"`
 	RefreshToken string `json:"refresh_token,omitempty"`
 	APIToken     string `json:"api_token,omitempty"`
 }