;; Copyright (c) 2014 Microsoft Corporation. All rights reserved.
;; Released under Apache 2.0 license as described in the file LICENSE.
;;
;; Author: Soonho Kong
;;
(require 'cl-lib)
(require 'lean-variable)
(require 'lean-cmd)
(require 'lean-info)
(require 'lean-util)
(require 'flycheck)

;; Parameters
;; ==========
(defvar-local lean-server-process-name "lean-server")
(defvar-local lean-server-buffer-name  "*lean-server*")
(defvar-local lean-server-option       "--server")

;; Log Function
;; ============
(defun lean-server-log (format-string &rest args)
  "Display a message at the bottom of the *lean-server* buffer."
  (with-current-buffer (lean-server-get-buffer)
    (goto-char (point-max))
    (insert (apply 'format (concat format-string "\n")  args))))

;; How to read data from an async process
;; ======================================
(defconst lean-server-syntax-pattern
  `((INFO ,(rx line-start "-- BEGININFO" line-end)
          ,(rx line-start (group "-- ENDINFO") line-end))
    (SET  ,(rx line-start "-- BEGINSET"  line-end)
          ,(rx line-start (group "-- ENDSET")  line-end))
    (EVAL ,(rx line-start "-- BEGINEVAL"  line-end)
          ,(rx line-start (group "-- ENDEVAL")  line-end))
    (ERROR ,(rx line-start "-- " (0+ not-newline) line-end)
           ,(rx line-start (group "-- ERROR")  line-end)))
  "Regular expression pattern for lean-server message syntax")

(defun lean-server-split-buffer (buf-str beg-regex end-regex)
  ""
  (let ((beg (string-match beg-regex buf-str))
        (end (string-match end-regex buf-str))
        pre body post)
    (when (and beg end)
      (setq end (match-end 1))
      (setq pre  (substring-no-properties buf-str 0 beg))
      (setq body (substring-no-properties buf-str beg end))
      (setq post (substring-no-properties buf-str end))
      `(,pre ,body ,post))))

(defun lean-server-check-buffer-and-partition (buf-str)
  "Return the status of buffer."
  (let (result)
    (cl-loop for (type beg-regex end-regex) in lean-server-syntax-pattern
             do (setq partition-result (lean-server-split-buffer buf-str beg-regex end-regex))
             if partition-result
             return  `(,type ,partition-result))))

(defun lean-server-process-received-message (buf str)
  "Process received message from lean-server"
  (lean-server-log "Received String: %s" str)
  ;; Append to buffer
  (setq lean-global-server-buffer (concat lean-global-server-buffer str))
  (let ((partition-result (lean-server-check-buffer-and-partition lean-global-server-buffer)))
    (pcase partition-result
      (`(,type (,pre ,body ,post))
       (lean-server-log "PRE: %s" pre)
       (lean-server-log "BODY: %s" body)
       (lean-server-log "POST: %s" post)
       (setq lean-global-server-message-to-process `(,type ,pre ,body))
       (setq lean-global-server-buffer post)))))

(defun lean-server-output-filter (process string)
  "Filter function attached to lean-server process"
  (lean-server-process-received-message (process-buffer process) string))

;; How to create an async process
;; ==============================
(defun lean-server-create-process ()
  "Create lean-server process."
  ;; (when (buffer-modified-p)
  ;;   (error "Please save the buffer before start lean-server."))
  (let ((process-connection-type nil)
        (lean-server-process
         (start-process lean-server-process-name
                        lean-server-buffer-name
                        (lean-get-executable lean-executable-name)
                        lean-server-option)))
    (set-process-coding-system lean-server-process 'utf-8 'utf-8)
    (set-process-filter lean-server-process 'lean-server-output-filter)
    (setq lean-global-server-buffer nil)
    (setq lean-global-server-current-file-name nil)
    (setq lean-global-server-message-to-process nil)
    (setq lean-global-server-process lean-server-process)
    lean-server-process))

(defun lean-server-kill-process ()
  "Kill lean-server process. Return t if killed, nil if nothing to kill"
  (interactive)
  (cond
   (lean-global-server-process
    (when (interactive-p)
      (message "lean-server-kill-process: %S killed" lean-global-server-process))
    (kill-process lean-global-server-process)
    (setq lean-global-server-process nil)
    t)
   (t (when (interactive-p)
        (message "lean-server-kill-process: no process to kill"))
      nil)))

(defun lean-server-restart-process ()
  "Restart lean-server process."
  (interactive)
  (and (lean-server-kill-process)
       (lean-server-create-process)))

(defun lean-server-get-process ()
  "Get lean-server process. If needed, create a one."
  (cond ((not lean-global-server-process)
         (lean-server-create-process))
        ((not (process-live-p lean-global-server-process))
         (when (interactive-p)
           (message "lean-server-get-process: %S is not live, kill it"
                    lean-global-server-process))
         (lean-server-kill-process))
        (t lean-global-server-process)))

(defun lean-server-get-buffer ()
  "Get lean-server buffer."
  (process-buffer (lean-server-get-process)))

;; How to send data to an async process
;; ====================================
(defun lean-flush-changed-lines ()
  "Flush lean-changed-lines.

Send REPLACE commands to lean-server, reset lean-changed-lines to nil."
  (cl-loop for n in lean-changed-lines
           do (lean-server-send-cmd (lean-cmd-replace n (lean-grab-line n)))
           finally (setq lean-changed-lines nil)))

(defun lean-server-check-current-file (&optional file-name)
  "Check lean-global-server-current-file-name.

If it's not the same with file-name (default: buffer-file-name), send VISIT cmd."
  (let ((current-file-name (or file-name (buffer-file-name))))
    (unless (string= lean-global-server-current-file-name
                     current-file-name)
      (lean-server-send-cmd (lean-cmd-visit current-file-name)))))

(defun lean-server-before-send-cmd (cmd)
  "Operations to perform before sending a command."
  (cl-case (lean-cmd-type cmd)
    ('LOAD    (setq lean-global-server-current-file-name
                    (lean-cmd-load-get-file-name cmd)))
    ('VISIT   (setq lean-global-server-current-file-name
                    (lean-cmd-visit-get-file-name cmd)))
    ('REPLACE (lean-server-check-current-file))
    ('INSERT  (lean-server-check-current-file))
    ('REMOVE  (lean-server-check-current-file))
    ('INFO    (lean-flush-changed-lines))
    ('CHECK   )
    ('SET     ())
    ('EVAL    ())))

(defun lean-server-after-send-cmd (cmd)
  "Operations to perform after sending a command."
  (cl-case (lean-cmd-type cmd)
    ('LOAD    ())
    ('VISIT   ())
    ('REPLACE ())
    ('INSERT  ())
    ('REMOVE  ())
    ('INFO    ())
    ('CHECK   ())
    ('SET     ())
    ('EVAL    ())))

(defun lean-server-send-cmd (cmd)
  "Send string to lean-server."
  (let ((proc (lean-server-get-process))
        (string-to-send (concat (lean-cmd-to-string cmd) "\n")))
    (lean-server-before-send-cmd cmd)
    ;; Logging
    (lean-server-log
     (concat "Send" "\n"
             "================" "\n"
             "%s\n"
             "================" "\n")
     string-to-send)
    (process-send-string proc string-to-send))
  (lean-server-after-send-cmd cmd))

(provide 'lean-server)