gptel-anthropic: Add support for sending PDFs (#459)

* gptel-anthropic.el (gptel-make-anthropic,
gptel--anthropic-parse-multipart, gptel--anthropic-models): Add
support for sending PDFs to the model
`claude-3-5-sonnet-20241022'.  This is the only model that
supports reading PDFs as of now.  Cache sent PDFs so follow up the
input cost of reading the PDF in follow up messages is 90%
cheaper.

gptel-anthropic.el

@@ -132,18 +132,31 @@ format."
    for part in parts
    for n upfrom 1
    with last = (length parts)
+   with type
    for text = (plist-get part :text)
+   for mime = (plist-get part :mime)
    for media = (plist-get part :media)
    if text do
    (and (or (= n 1) (= n last)) (setq text (gptel--trim-prefixes text))) and
    unless (string-empty-p text)
    collect `(:type "text" :text ,text) into parts-array end
    else if media
-   collect
-   `(:type "image"
+   do
+   (setq type (cond                     ;Currently supported: Images and PDFs
+               ((equal (substring mime 0 5) "image") "image")
+               ;; NOTE: Only Claude 3.5 Sonnet supports PDF documents:
+               ((equal mime "application/pdf") "document")
+               (t (error (concat "(gptel-anthropic) Request aborted: "
+                                 "trying to send unsupported MIME type %s")
+                         mime))))
+   and collect
+   `(:type ,type
      :source (:type "base64"
               :media_type ,(plist-get part :mime)
-              :data ,(gptel--base64-encode media)))
+              :data ,(gptel--base64-encode media))
+     ;; TODO Make media caching a user option
+     ,@(and (gptel--model-capable-p 'cache)
+        '(:cache_control (:type "ephemeral"))))
    into parts-array
    finally return (vconcat parts-array)))
 
@@ -186,23 +199,23 @@ files in the context."
 (defconst gptel--anthropic-models
   '((claude-3-5-sonnet-20241022
      :description "Highest level of intelligence and capability"
-     :capabilities (media tool)
-     :mime-types ("image/jpeg" "image/png" "image/gif" "image/webp")
+     :capabilities (media tool cache)
+     :mime-types ("image/jpeg" "image/png" "image/gif" "image/webp" "application/pdf")
      :context-window 200
      :input-cost 3
      :output-cost 15
      :cutoff-date "2024-04")
     (claude-3-5-sonnet-20240620
      :description "Highest level of intelligence and capability"
-     :capabilities (media tool)
+     :capabilities (media tool cache)
      :mime-types ("image/jpeg" "image/png" "image/gif" "image/webp")
      :context-window 200
      :input-cost 3
      :output-cost 15
      :cutoff-date "2024-04")
     (claude-3-opus-20240229
      :description "Top-level performance, intelligence, fluency, and understanding"
-     :capabilities (media tool)
+     :capabilities (media tool cache)
      :mime-types ("image/jpeg" "image/png" "image/gif" "image/webp")
      :context-window 200
      :input-cost 15
@@ -262,7 +275,9 @@ sources:
           (header
            (lambda () (when-let (key (gptel--get-api-key))
                    `(("x-api-key" . ,key)
-                     ("anthropic-version" . "2023-06-01")))))
+                     ("anthropic-version" . "2023-06-01")
+                     ("anthropic-beta" . "pdfs-2024-09-25")
+                     ("anthropic-beta" . "prompt-caching-2024-07-31")))))
           (models gptel--anthropic-models)
           (host "api.anthropic.com")
           (protocol "https")