refactor: improve Bearer token parsing and validation with tests (#96)

- Refactor Bearer token parsing into a dedicated function for improved validation and readability
- Add comprehensive tests for edge cases in Bearer token extraction

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/96
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

operation/operation_test.go

@@ -0,0 +1,81 @@
+package operation
+
+import (
+	"testing"
+)
+
+func TestParseBearerToken(t *testing.T) {
+	tests := []struct {
+		name      string
+		header    string
+		wantToken string
+		wantOK    bool
+	}{
+		{
+			name:      "valid token",
+			header:    "Bearer validtoken",
+			wantToken: "validtoken",
+			wantOK:    true,
+		},
+		{
+			name:      "token with spaces trimmed",
+			header:    "Bearer   spacedToken ",
+			wantToken: "spacedToken",
+			wantOK:    true,
+		},
+		{
+			name:      "lowercase bearer should fail",
+			header:    "bearer lowercase",
+			wantToken: "",
+			wantOK:    false,
+		},
+		{
+			name:      "bearer with no token",
+			header:    "Bearer ",
+			wantToken: "",
+			wantOK:    false,
+		},
+		{
+			name:      "bearer with only spaces",
+			header:    "Bearer     ",
+			wantToken: "",
+			wantOK:    false,
+		},
+		{
+			name:      "missing space after Bearer",
+			header:    "Bearertoken",
+			wantToken: "",
+			wantOK:    false,
+		},
+		{
+			name:      "different auth type",
+			header:    "Basic dXNlcjpwYXNz",
+			wantToken: "",
+			wantOK:    false,
+		},
+		{
+			name:      "empty header",
+			header:    "",
+			wantToken: "",
+			wantOK:    false,
+		},
+		{
+			name:      "token with internal spaces",
+			header:    "Bearer token with spaces",
+			wantToken: "token with spaces",
+			wantOK:    true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotToken, gotOK := parseBearerToken(tt.header)
+			if gotToken != tt.wantToken {
+				t.Errorf("parseBearerToken() token = %q, want %q", gotToken, tt.wantToken)
+			}
+			if gotOK != tt.wantOK {
+				t.Errorf("parseBearerToken() ok = %v, want %v", gotOK, tt.wantOK)
+			}
+		})
+	}
+}