Refactored summarizer engine selection and added tests

kagi-test.el

@@ -304,6 +304,21 @@ https://www.example.com"
       (it "returns a summary for an HTTP URL"
         (expect (kagi-summarize dummy-http-url) :to-equal dummy-output))
       (it "throws for an unsupported URL scheme"
-        (expect (kagi-summarize dummy-ftp-url) :to-throw)))))
+        (expect (kagi-summarize dummy-ftp-url) :to-throw))
+      (it "return a summary for a valid engine with different capitalization"
+        (expect (kagi-summarize dummy-https-url nil "Daphne") :to-equal dummy-output)
+        (let ((args (car (spy-calls-args-for #'kagi--call-summarizer 0))))
+          (expect (map-elt args "engine") :to-equal "daphne"))
+        )
+      (it "uses kagi-summarizer-engine variable for invalid engine values"
+        (setq kagi-summarizer-engine "Daphne")
+        (expect (kagi-summarize dummy-https-url nil "bram") :to-equal dummy-output)
+        (let ((args (car (spy-calls-args-for #'kagi--call-summarizer 0))))
+          (expect (map-elt args "engine") :to-equal "daphne")))
+      (it "uses the cecil engine when an invalid engine is configured"
+        (setq kagi-summarizer-engine "steve")
+        (expect (kagi-summarize dummy-https-url) :to-equal dummy-output)
+        (let ((args (car (spy-calls-args-for #'kagi--call-summarizer 0))))
+          (expect (map-elt args "engine") :to-equal "cecil"))))))
 
 ;;; kagi-test.el ends here

kagi.el

@@ -539,6 +539,18 @@ to `kagi-summarizer-default-language'."
     kagi-summarizer-default-language)
    (t "EN")))
 
+(defun kagi--valid-engine-p (engine)
+  "Return non-nil when the given ENGINE is valid."
+  (and (stringp engine)
+       (map-elt kagi--summarizer-engines (downcase engine))))
+
+(defun kagi--summarizer-engine (hint)
+  "Return a valid engine name based on the name given in HINT."
+  (cond ((kagi--valid-engine-p hint) (downcase hint))
+        ((kagi--valid-engine-p kagi-summarizer-engine)
+         (downcase kagi-summarizer-engine))
+        (t "cecil")))
+
 (defun kagi-summarize (text-or-url &optional language engine format)
   "Return the summary of the given TEXT-OR-URL.
 
@@ -554,9 +566,7 @@ of text and `takeaway' returns a bullet list."
   (let* ((kagi-summarizer-default-language
           (kagi--summarizer-determine-language language))
          (kagi-summarizer-engine
-          (if (stringp engine)
-              (downcase engine)
-            kagi-summarizer-engine))
+          (kagi--summarizer-engine engine))
          (kagi-summarizer-default-summary-format format))
     (if-let* ((response (if (kagi--url-p text-or-url)
                             (kagi--call-url-summarizer text-or-url)