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backend/internal/misc/oauth.go

@@ -0,0 +1,120 @@
+package misc
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"net/url"
+	"strings"
+)
+
+// GenerateRandomState generates a cryptographically secure random state parameter
+// for OAuth2 flows to prevent CSRF attacks.
+//
+// Returns:
+//   - string: A hexadecimal encoded random state string
+//   - error: An error if the random generation fails, nil otherwise
+func GenerateRandomState() (string, error) {
+	bytes := make([]byte, 16)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", fmt.Errorf("failed to generate random bytes: %w", err)
+	}
+	return hex.EncodeToString(bytes), nil
+}
+
+// OAuthCallback captures the parsed OAuth callback parameters.
+type OAuthCallback struct {
+	Code             string
+	State            string
+	Error            string
+	ErrorDescription string
+}
+
+// AsyncPrompt runs a prompt function in a goroutine and returns channels for
+// the result. The returned channels are buffered (size 1) so the goroutine can
+// complete even if the caller abandons the channels.
+func AsyncPrompt(promptFn func(string) (string, error), message string) (<-chan string, <-chan error) {
+	inputCh := make(chan string, 1)
+	errCh := make(chan error, 1)
+	go func() {
+		input, err := promptFn(message)
+		if err != nil {
+			errCh <- err
+			return
+		}
+		inputCh <- input
+	}()
+	return inputCh, errCh
+}
+
+// ParseOAuthCallback extracts OAuth parameters from a callback URL.
+// It returns nil when the input is empty.
+func ParseOAuthCallback(input string) (*OAuthCallback, error) {
+	trimmed := strings.TrimSpace(input)
+	if trimmed == "" {
+		return nil, nil
+	}
+
+	candidate := trimmed
+	if !strings.Contains(candidate, "://") {
+		if strings.HasPrefix(candidate, "?") {
+			candidate = "http://localhost" + candidate
+		} else if strings.ContainsAny(candidate, "/?#") || strings.Contains(candidate, ":") {
+			candidate = "http://" + candidate
+		} else if strings.Contains(candidate, "=") {
+			candidate = "http://localhost/?" + candidate
+		} else {
+			return nil, fmt.Errorf("invalid callback URL")
+		}
+	}
+
+	parsedURL, err := url.Parse(candidate)
+	if err != nil {
+		return nil, err
+	}
+
+	query := parsedURL.Query()
+	code := strings.TrimSpace(query.Get("code"))
+	state := strings.TrimSpace(query.Get("state"))
+	errCode := strings.TrimSpace(query.Get("error"))
+	errDesc := strings.TrimSpace(query.Get("error_description"))
+
+	if parsedURL.Fragment != "" {
+		if fragQuery, errFrag := url.ParseQuery(parsedURL.Fragment); errFrag == nil {
+			if code == "" {
+				code = strings.TrimSpace(fragQuery.Get("code"))
+			}
+			if state == "" {
+				state = strings.TrimSpace(fragQuery.Get("state"))
+			}
+			if errCode == "" {
+				errCode = strings.TrimSpace(fragQuery.Get("error"))
+			}
+			if errDesc == "" {
+				errDesc = strings.TrimSpace(fragQuery.Get("error_description"))
+			}
+		}
+	}
+
+	if code != "" && state == "" && strings.Contains(code, "#") {
+		parts := strings.SplitN(code, "#", 2)
+		code = parts[0]
+		state = parts[1]
+	}
+
+	if errCode == "" && errDesc != "" {
+		errCode = errDesc
+		errDesc = ""
+	}
+
+	if code == "" && errCode == "" {
+		return nil, fmt.Errorf("callback URL missing code")
+	}
+
+	return &OAuthCallback{
+		Code:             code,
+		State:            state,
+		Error:            errCode,
+		ErrorDescription: errDesc,
+	}, nil
+}