;; -*- lexical-binding: t -*-
;; stomp.el, interpret STOMP messages.

(require 'map)

(defun stomp-connect (host port)
  "Connect to a server supporting the STOMP protocol"
  (message "Not implemented yet"))

;; TODO: make this send more than just the sommand
(defun stomp-send-message (process message)
  "Send a message to a STOMP process"
  (process-send-string
   process
   (format "%s\n\n\u0000\n" (alist-get 'command message))))
                       
;; TODO: debug this and find a fast way to test it
(defun stomp-filter-function (callback)
  "Filter function to be used with processes"
  (unless (functionp callback) (signal 'wrong-type-argument 'functionp))
  (lambda (proc string)
    (with-current-buffer (process-buffer proc)
      (goto-char (point-max))
      (insert string)
      (let ((message (stomp-shift-message (current-buffer))))
        (if message (funcall callback message))))))

(defun stomp-shift-message (buffer)
  "Read a message from a buffer. After reading a message, it will
   be deleted from the buffer."
  (let ((message (stomp-read-message buffer)))
    (cond
     (message (stomp-delete-message buffer) message)
     (t nil))))

(defun stomp-delete-message (buffer)
  "Delete the top-most messsage in a buffer"
  (with-current-buffer buffer
    (delete-region (point-min) (+ 2x (stomp-find-message-end-point buffer)))))

(defun stomp-read-message (buffer)
  "Attempt to read a single message from a buffer.
   The buffer may contain multiple messages, but only the first
   message (from top to bottom) will be read. If there are no
   messages in the buffer, nil will be returned."
  (with-current-buffer buffer
    (goto-char (point-min))
    (while (search-forward "\r" nil t)
      (replace-match ""))
    (let ((message ()) (headers ()) (content)
          (headers-end-point (stomp-find-headers-end-point buffer)))
      (goto-char (point-min))
      (map-put message 'command (current-word))
      
      (setq headers (stomp-read-headers buffer headers-end-point))
      
      ;; TODO: take content-length header into account
      (setq content (buffer-substring
                     (+ 1 headers-end-point)
                     (stomp-find-message-end-point buffer)))
      (cond
       (content
        (map-put message 'headers headers)
        (map-put message 'content content))
       (t nil)))))

(defun stomp-read-headers (buffer end-point &optional headers)
  "Attempt to read the headers of a stomp message in *buffer*"
  (with-current-buffer buffer
    (unless headers (goto-char (point-min)))
    (forward-line)
    (let ((header (split-string (thing-at-point 'line) ":")))
      (cond
       ((= (line-end-position) end-point) headers)
       ((> (length header) 2) (throw 'invalid-header nil))
       (t (stomp-read-headers buffer end-point
                              (map-put headers
                                       (car header)
                                       (replace-regexp-in-string "\n$" "" (car (last header))))))))))

(defun stomp-find-message-end-point (buffer)
  "Find the null byte at the end of a STOMP message"
  (with-current-buffer buffer
    (goto-char (point-min))
    (search-forward "\u0000")
    (- (point) 1)))

(defun stomp-find-headers-end-point (buffer)
  "Find the end of the header part of a STOMP frame."
  (with-current-buffer buffer
    (goto-char (point-min))
    (search-forward-regexp "^$")
    (line-end-position)))