gptel-kagi: Add support for the Kagi summarizer

* gptel-kagi.el (gptel--request-data, gptel--parse-buffer,
gptel-make-kagi): Add support for the Kagi summarizer.  If there
is a url at point (or at the end of the provided prompt), it is
used as the summarizer input.  Otherwise the behavior is
unchanged.

* README (Kagi): Mention summarizer support.

* gptel.el: Mention summarizer support.

README.org

@@ -5,7 +5,7 @@
 GPTel is a simple Large Language Model chat client for Emacs, with support for multiple models and backends.
 
 | LLM Backend     | Supports | Requires                  |
-|--------------+----------+---------------------------|
+|-----------------+----------+---------------------------|
 | ChatGPT         | ✓      | [[https://platform.openai.com/account/api-keys][API key]]                   |
 | Azure           | ✓      | Deployment and API key    |
 | Ollama          | ✓      | [[https://ollama.ai/][Ollama running locally]]    |
@@ -14,6 +14,7 @@ GPTel is a simple Large Language Model chat client for Emacs, with support for m
 | Llama.cpp       | ✓      | [[https://github.com/ggerganov/llama.cpp/tree/master/examples/server#quick-start][Llama.cpp running locally]] |
 | Llamafile       | ✓      | [[https://github.com/Mozilla-Ocho/llamafile#quickstart][Local Llamafile server]]    |
 | Kagi FastGPT    | ✓      | [[https://kagi.com/settings?p=api][API key]]                   |
+| Kagi Summarizer | ✓      | [[https://kagi.com/settings?p=api][API key]]                   |
 | PrivateGPT      | Planned  | -                         |
 
 *General usage*: ([[https://www.youtube.com/watch?v=bsRnh_brggM][YouTube Demo]])
@@ -49,7 +50,7 @@ GPTel uses Curl if available, but falls back to url-retrieve to work without ext
       - [[#ollama][Ollama]]
       - [[#gemini][Gemini]]
       - [[#llamacpp-or-llamafile][Llama.cpp or Llamafile]]
-      - [[#kagi-fastgpt][Kagi FastGPT]]
+      - [[#kagi-fastgpt--summarizer][Kagi (FastGPT & Summarizer)]]
   - [[#usage][Usage]]
     - [[#in-any-buffer][In any buffer:]]
     - [[#in-a-dedicated-chat-buffer][In a dedicated chat buffer:]]
@@ -252,28 +253,33 @@ You can pick this backend from the menu when using gptel (see [[#usage][Usage]])
 
 #+html: </details>
 #+html: <details><summary>
-**** Kagi FastGPT
+**** Kagi (FastGPT & Summarizer)
 #+html: </summary>
 
-*NOTE*: Kagi's FastGPT model does not support multi-turn conversations, interactions are "one-shot".  It also does not support streaming responses.
+Kagi's FastGPT model and the Universal Summarizer are both supported.  A couple of notes:
+
+1. Universal Summarizer: If there is a URL at point, the summarizer will summarize the contents of the URL.  Otherwise the context sent to the model is the same as always: the buffer text upto point, or the contents of the region if the region is active.
+
+2. Kagi models do not support multi-turn conversations, interactions are "one-shot".  They also do not support streaming responses.
 
 Register a backend with
 #+begin_src emacs-lisp
-;; :key can be a function that returns the API key
 (gptel-make-kagi
- "Kagi"                                 ;Name of your choice
+ "Kagi" ;any name
- :key "YOUR_KAGI_API_KEY")
+ :key "YOUR_KAGI_API_KEY") ;:key can be a function
 #+end_src
 These are the required parameters, refer to the documentation of =gptel-make-kagi= for more.
 
-You can pick this backend from the transient menu when using gptel (see Usage), or set this as the default value of =gptel-backend=:
+You can pick this backend and the model (fastgpt/summarizer) from the transient menu when using gptel.  Alternatively you can set this as the default value of =gptel-backend=:
 
 #+begin_src emacs-lisp
 ;; OPTIONAL configuration
-(setq-default gptel-model "fastgpt" ;only supported Kagi model
+(setq-default gptel-model "fastgpt"
               gptel-backend (gptel-make-kagi "Kagi" :key ...))
 #+end_src
 
+The alternatives to =fastgpt= include =summarize:cecil=, =summarize:agnes=, =summarize:daphne= and =summarize:muriel=.  The difference between the summarizer engines is [[https://help.kagi.com/kagi/api/summarizer.html#summarization-engines][documented here]].
+
 #+html: </details>
 
 ** Usage

gptel-kagi.el

@@ -69,42 +69,65 @@
 
 (cl-defmethod gptel--request-data ((_backend gptel-kagi) prompts)
   "JSON encode PROMPTS for sending to ChatGPT."
+  (pcase-exhaustive gptel-model
+    ("fastgpt"
      `(,@prompts :web_search t :cache t))
+    ((and model (guard (string-prefix-p "summarize" model)))
+     `(,@prompts :engine ,(substring model 10)))))
 
 (cl-defmethod gptel--parse-buffer ((_backend gptel-kagi) &optional _max-entries)
-  (let ((prompts)
+  (let ((url (or (thing-at-point 'url)
+                 (get-text-property (point) 'shr-url)
+                 (get-text-property (point) 'image-url)))
+        ;; (filename (thing-at-point 'existing-filename)) ;no file upload support yet
         (prop (text-property-search-backward
                'gptel 'response
                (when (get-char-property (max (point-min) (1- (point)))
                                         'gptel)
                  t))))
+    (if (and url (string-prefix-p "summarize" gptel-model))
+        (list :url url)
       (if (and (prop-match-p prop)
                (prop-match-value prop))
           (user-error "No user prompt found!")
-      (setq prompts (list
+        (let ((prompts
-                     :query
-                     (if (prop-match-p prop)
-                         (concat
-                          ;; Fake a system message by including it in the prompt
-                          gptel--system-message "\n\n"
                (string-trim
                 (buffer-substring-no-properties (prop-match-beginning prop)
                                                 (prop-match-end prop))
                 (format "[\t\r\n ]*\\(?:%s\\)?[\t\r\n ]*"
                         (regexp-quote (gptel-prompt-prefix-string)))
                 (format "[\t\r\n ]*\\(?:%s\\)?[\t\r\n ]*"
-                                   (regexp-quote (gptel-response-prefix-string)))))
+                        (regexp-quote (gptel-response-prefix-string))))))
-                       "")))
+          (pcase-exhaustive gptel-model
-      prompts)))
+            ("fastgpt"
+             (setq prompts (list
+                            :query
+                            (if (prop-match-p prop)
+                                (concat
+                                 ;; Fake a system message by including it in the prompt
+                                 gptel--system-message "\n\n" prompts)
+                              ""))))
+            ((and model (guard (string-prefix-p "summarize" model)))
+             ;; If the entire contents of the prompt looks like a url, send the url
+             ;; Else send the text of the region
+             (setq prompts
+                   (if-let (((prop-match-p prop))
+                            (engine (substring model 10)))
+                       ;; It's a region of text
+                       (list :text prompts)
+                     ""))))
+          prompts)))))
 
 ;;;###autoload
 (cl-defun gptel-make-kagi
     (name &key stream key
           (host "kagi.com")
           (header (lambda () `(("Authorization" . ,(concat "Bot " (gptel--get-api-key))))))
-          (models '("fastgpt"))
+          (models '("fastgpt"
+                    "summarize:cecil" "summarize:agnes"
+                    "summarize:daphne" "summarize:muriel"))
           (protocol "https")
-          (endpoint "/api/v0/fastgpt"))
+          (endpoint "/api/v0/"))
   "Register a Kagi FastGPT backend for gptel with NAME.
 
 Keyword arguments:
@@ -142,9 +165,11 @@ Example:
                   :models models
                   :protocol protocol
                   :endpoint endpoint
-                  :url (if protocol
+                  :url
-                           (concat protocol "://" host endpoint)
+                  (lambda ()
-                         (concat host endpoint)))))
+                    (concat protocol "://" host endpoint
+                            (if (equal gptel-model "fastgpt")
+                                "fastgpt" "summarize"))))))
     (prog1 backend
       (setf (alist-get name gptel--known-backends
                        nil nil #'equal)

gptel.el

@@ -30,7 +30,7 @@
 ;; gptel is a simple Large Language Model chat client, with support for multiple models/backends.
 ;;
 ;; gptel supports
-;; - The services ChatGPT, Azure, Gemini, and Kagi (FastGPT)
+;; - The services ChatGPT, Azure, Gemini, and Kagi (FastGPT & Summarizer)
 ;; - Local models via Ollama, Llama.cpp, Llamafiles or GPT4All
 ;;
 ;;  Additionally, any LLM service (local or remote) that provides an