gptel-kagi: Add support for Kagi FastGPT

* gptel.el: Bump version and update package description.

* gptel-kagi.el (gptel--parse-response, gptel--request-data,
gptel--parse-buffer, gptel-make-kagi): Add new file and support
for the Kagi FastGPT LLM API.  Streaming and setting model
parameters (temperature, max tokesn) are not supported by the API.
A Kagi backend can be added with `gptel-make-kagi`.

* README.org: Update with instructions for Kagi.

README.org

@@ -2,18 +2,19 @@
 
 [[https://melpa.org/#/gptel][file:https://melpa.org/packages/gptel-badge.svg]]
 
-GPTel is a simple Large Language Model chat client for Emacs, with support for multiple models/backends.
+GPTel is a simple Large Language Model chat client for Emacs, with support for multiple models and backends.
 
-| LLM Backend | Supports | Requires                  |
+| LLM Backend  | Supports | Requires                  |
-|-------------+----------+---------------------------|
+|--------------+----------+---------------------------|
-| ChatGPT     | ✓      | [[https://platform.openai.com/account/api-keys][API key]]                   |
+| ChatGPT      | ✓      | [[https://platform.openai.com/account/api-keys][API key]]                   |
-| Azure       | ✓      | Deployment and API key    |
+| Azure        | ✓      | Deployment and API key    |
-| Ollama      | ✓      | [[https://ollama.ai/][Ollama running locally]]    |
+| Ollama       | ✓      | [[https://ollama.ai/][Ollama running locally]]    |
-| GPT4All     | ✓      | [[https://gpt4all.io/index.html][GPT4All running locally]]   |
+| GPT4All      | ✓      | [[https://gpt4all.io/index.html][GPT4All running locally]]   |
-| Gemini      | ✓      | [[https://makersuite.google.com/app/apikey][API key]]                   |
+| Gemini       | ✓      | [[https://makersuite.google.com/app/apikey][API key]]                   |
-| Llama.cpp   | ✓      | [[https://github.com/ggerganov/llama.cpp/tree/master/examples/server#quick-start][Llama.cpp running locally]] |
+| 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]]   |
+| Llamafile    | ✓      | [[https://github.com/Mozilla-Ocho/llamafile#quickstart][Local Llamafile server]]    |
-| PrivateGPT  | Planned  | -                         |
+| Kagi FastGPT | ✓      | [[https://kagi.com/settings?p=api][API key]]                   |
+| PrivateGPT   | Planned  | -                         |
 
 *General usage*: ([[https://www.youtube.com/watch?v=bsRnh_brggM][YouTube Demo]])
 
@@ -48,6 +49,7 @@ 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]]
   - [[#usage][Usage]]
     - [[#in-any-buffer][In any buffer:]]
     - [[#in-a-dedicated-chat-buffer][In a dedicated chat buffer:]]
@@ -249,6 +251,31 @@ You can pick this backend from the menu when using gptel (see [[#usage][Usage]])
 #+end_src
 
 #+html: </details>
+#+html: <details><summary>
+**** Kagi FastGPT
+#+html: </summary>
+
+*NOTE*: Kagi's FastGPT model does not support multi-turn conversations, interactions are "one-shot".  It also does 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
+ :key "YOUR_KAGI_API_KEY")
+#+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=:
+
+#+begin_src emacs-lisp
+;; OPTIONAL configuration
+(setq-default gptel-model "fastgpt" ;only supported Kagi model
+              gptel-backend (gptel-make-kagi "Kagi" :key ...))
+#+end_src
+
+#+html: </details>
+
 ** Usage
 
 (This is also a [[https://www.youtube.com/watch?v=bsRnh_brggM][video demo]] showing various uses of gptel.)

gptel-kagi.el

@@ -0,0 +1,154 @@
+;;; gptel-kagi.el --- Kagi support for gptel     -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2023  Karthik Chikmagalur
+
+;; Author: Karthik Chikmagalur <karthikchikmagalur@gmail.com>
+;; Keywords: hypermedia
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file adds support for the Kagi FastGPT LLM API to gptel
+
+;;; Code:
+(require 'gptel)
+(require 'cl-generic)
+(eval-when-compile
+  (require 'cl-lib))
+
+;;; Kagi
+(cl-defstruct (gptel-kagi (:constructor gptel--make-kagi)
+                            (:copier nil)
+                            (:include gptel-backend)))
+
+(cl-defmethod gptel--parse-response ((_backend gptel-kagi) response info)
+  (let* ((data (plist-get response :data))
+         (output (plist-get data :output))
+         (references (plist-get data :references)))
+    (when references
+      (setq references
+            (cl-loop with linker =
+                     (pcase (buffer-local-value 'major-mode
+                                                (plist-get info :buffer))
+                       ('org-mode
+                        (lambda (text url)
+                          (format "[[%s][%s]]" url text)))
+                       ('markdown-mode
+                        (lambda (text url)
+                          (format "[%s](%s)" text url)))
+                       (_ (lambda (text url)
+                            (buttonize
+                             text (lambda (data) (browse-url data))
+                             url))))
+                     for ref across references
+                     for title = (plist-get ref :title)
+                     for snippet = (plist-get ref :snippet)
+                     for url = (plist-get ref :url)
+                     for n upfrom 1
+                     collect
+                     (concat (format "[%d] " n)
+                             (funcall linker title url) ": "
+                             (replace-regexp-in-string
+                              "</?b>" "*" snippet))
+                     into ref-strings
+                     finally return
+                     (concat "\n\n" (mapconcat #'identity ref-strings "\n")))))
+        (concat output references)))
+
+(cl-defmethod gptel--request-data ((_backend gptel-kagi) prompts)
+  "JSON encode PROMPTS for sending to ChatGPT."
+  `(,@prompts :web_search t :cache t))
+
+(cl-defmethod gptel--parse-buffer ((_backend gptel-kagi) &optional _max-entries)
+  (let ((prompts)
+        (prop (text-property-search-backward
+               'gptel 'response
+               (when (get-char-property (max (point-min) (1- (point)))
+                                        'gptel)
+                 t))))
+    (if (and (prop-match-p prop)
+             (prop-match-value prop))
+        (user-error "No user prompt found!")
+      (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"
+                          (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)))))
+                       "")))
+      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"))
+          (protocol "https")
+          (endpoint "/api/v0/fastgpt"))
+  "Register a Kagi FastGPT backend for gptel with NAME.
+
+Keyword arguments:
+
+HOST is the Kagi host (with port), defaults to \"kagi.com\".
+
+MODELS is a list of available Kagi models: only fastgpt is supported.
+
+STREAM is a boolean to toggle streaming responses, defaults to
+false.  Kagi does not support a streaming API yet.
+
+PROTOCOL (optional) specifies the protocol, https by default.
+
+ENDPOINT (optional) is the API endpoint for completions, defaults to
+\"/api/v0/fastgpt\".
+
+HEADER (optional) is for additional headers to send with each
+request.  It should be an alist or a function that retuns an
+alist, like:
+((\"Content-Type\" . \"application/json\"))
+
+KEY (optional) is a variable whose value is the API key, or
+function that returns the key.
+
+Example:
+-------
+
+(gptel-make-kagi \"Kagi\" :key my-kagi-key)"
+  stream                                ;Silence byte-compiler
+  (let ((backend (gptel--make-kagi
+                  :name name
+                  :host host
+                  :header header
+                  :key key
+                  :models models
+                  :protocol protocol
+                  :endpoint endpoint
+                  :url (if protocol
+                           (concat protocol "://" host endpoint)
+                         (concat host endpoint)))))
+    (prog1 backend
+      (setf (alist-get name gptel--known-backends
+                       nil nil #'equal)
+                  backend))))
+
+(provide 'gptel-kagi)
+;;; gptel-kagi.el ends here

gptel.el

@@ -3,7 +3,7 @@
 ;; Copyright (C) 2023  Karthik Chikmagalur
 
 ;; Author: Karthik Chikmagalur
-;; Version: 0.5.5
+;; Version: 0.6.0
 ;; Package-Requires: ((emacs "27.1") (transient "0.4.0") (compat "29.1.4.1"))
 ;; Keywords: convenience
 ;; URL: https://github.com/karthink/gptel
@@ -29,20 +29,24 @@
 
 ;; gptel is a simple Large Language Model chat client, with support for multiple models/backends.
 ;;
-;; gptel supports ChatGPT, Azure, Gemini and local models using Ollama and
+;; gptel supports
-;; GPT4All.
+;; - The services ChatGPT, Azure, Gemini, and Kagi (FastGPT)
+;; - Local models via Ollama, Llama.cpp, Llamafiles or GPT4All
 ;;
-;;  Features:
+;;  Additionally, any LLM service (local or remote) that provides an
-;;  - It’s async and fast, streams responses.
+;;  OpenAI-compatible API is supported.
-;;  - Interact with LLMs from anywhere in Emacs (any buffer, shell, minibuffer,
-;;    wherever)
-;;  - LLM responses are in Markdown or Org markup.
-;;  - Supports conversations and multiple independent sessions.
-;;  - Save chats as regular Markdown/Org/Text files and resume them later.
-;;  - You can go back and edit your previous prompts or LLM responses when
-;;    continuing a conversation.  These will be fed back to the model.
 ;;
-;; Requirements for ChatGPT, Azure or Gemini:
+;; Features:
+;; - It’s async and fast, streams responses.
+;; - Interact with LLMs from anywhere in Emacs (any buffer, shell, minibuffer,
+;;   wherever)
+;; - LLM responses are in Markdown or Org markup.
+;; - Supports conversations and multiple independent sessions.
+;; - Save chats as regular Markdown/Org/Text files and resume them later.
+;; - You can go back and edit your previous prompts or LLM responses when
+;;   continuing a conversation.  These will be fed back to the model.
+;;
+;; Requirements for ChatGPT, Azure, Gemini or Kagi:
 ;;
 ;; - You need an appropriate API key.  Set the variable `gptel-api-key' to the
 ;;   key or to a function of no arguments that returns the key.  (It tries to
@@ -50,13 +54,17 @@
 ;;
 ;; - For Azure: define a gptel-backend with `gptel-make-azure', which see.
 ;; - For Gemini: define a gptel-backend with `gptel-make-gemini', which see.
+;; - For Kagi: define a gptel-backend with `gptel-make-kagi', which see
 ;;
-;; For local models using Ollama or GPT4All:
+;; For local models using Ollama, Llama.cpp or GPT4All:
 ;;
 ;; - The model has to be running on an accessible address (or localhost)
 ;; - Define a gptel-backend with `gptel-make-ollama' or `gptel-make-gpt4all',
 ;;   which see.
 ;;
+;; Consult the package README for examples and more help with configuring
+;; backends.
+;;
 ;; Usage:
 ;;
 ;; gptel can be used in any buffer or in a dedicated chat buffer.  The