;;; valeri-mode.el --- a major-mode for editing Valeri programs  -*- lexical-binding: t -*-


(require 'comint)

(defcustom valeri-default-application "valeri"
  "Default application to run in Valeri process."
  :type 'string
  :group 'valeri)

(defcustom valeri-default-command-switches (list)
  "Command switches for `valeri-default-application'.
Should be a list of strings."
  :type '(repeat string)
  :group 'valeri)

(defcustom valeri-prompt-regexp "\\(valeri>[\t ]+\\)+"
  "Regexp which matches the Valeri program's prompt."
  :type  'regexp
  :group 'valeri)

(defcustom valeri-traceback-line-re
  ;; This regexp skips prompt and meaningless "stdin:N:" prefix when looking
  ;; for actual file-line locations.
  "^\\(?:[\t ]*\\|.*>[\t ]+\\)\\(?:[^\n\t ]+:[0-9]+:[\t ]*\\)*\\(?:\\([^\n\t ]+\\):\\([0-9]+\\):\\)"
  "Regular expression that describes tracebacks and errors."
  :type 'regexp
  :group 'valeri)

(defvar valeri-process-init-code
  (mapconcat
   'identity
   '("")
   " "))

(defvar valeri-process nil
  "The active Valeri process")

(defvar valeri-process-buffer nil
  "Buffer used for communication with the Valeri process.")

(defvar valeri--repl-buffer-p nil
  "Buffer-local flag saying if this is a Valeri REPL buffer.")
(make-variable-buffer-local 'valeri--repl-buffer-p)

(defvar valeri-eoe-indicator "valeri-eoe")

(defun valeri-get-create-process ()
  "Return active Valeri process creating one if necessary."
  (valeri-start-process)
  valeri-process)

(defun valeri-send-string (buffer body)
  "Pass BODY to the Valeri process in BUFFER."
  (let ((escaped-body (format "\x1b[200~%s\x1b[201~" body))
        (eoe-string (format "\n(println \"%s\")\n" valeri-eoe-indicator)))
    (mapconcat
     #'identity
     (butlast
      (split-string
       (mapconcat
        #'org-trim
        (org-babel-comint-with-output
            (buffer valeri-eoe-indicator t escaped-body)
          (insert (org-babel-chomp escaped-body) eoe-string)
          (comint-send-input nil t))
        "\n") "[\r\n]")) "\n")
    )
  )

;;;###autoload
(define-derived-mode valeri-mode lisp-mode "Valeri"
  "Major mode for editing Valeri code."
  :group 'valeri
  )

;;;###autoload
(defalias 'run-valeri #'valeri-start-process)

;;;###autoload
(defun valeri-start-process (&optional name program startfile &rest switches)
  "Start a Valeri process named NAME, running PROGRAM.
PROGRAM defaults to NAME, which defaults to `valeri-default-application'.
When called interactively, switch to the process buffer."
  (interactive)
  (setq name (or name valeri-default-application))
  (setq program (or program valeri-default-application))
  ;; don't re-initialize if there already is a Valeri process
  (unless (comint-check-proc (format "*%s*" name))
    (setq valeri-process-buffer (apply #'make-comint name program startfile
                                    (or switches valeri-default-command-switches)))
    (setq valeri-process (get-buffer-process valeri-process-buffer))
    (set-process-query-on-exit-flag valeri-process nil)
    (with-current-buffer valeri-process-buffer
      ;; enable error highlighting in stack traces
      (require 'compile)
      (setq valeri--repl-buffer-p t)
      (make-local-variable 'compilation-error-regexp-alist)
      (setq compilation-error-regexp-alist
            (cons (list valeri-traceback-line-re 1 2)
                  compilation-error-regexp-alist))
      (compilation-shell-minor-mode 1)
      (setq-local comint-prompt-regexp valeri-prompt-regexp)

      ;; Don't send initialization code until seeing the prompt to ensure that
      ;; the interpreter is ready.
      ;; (while (not (valeri-prompt-line))
       ;;  (accept-process-output (get-buffer-process (current-buffer)))
        ;; (goto-char (point-max)))
      ;; (valeri-send-string valeri-process-init-code)
      ))

  ;; when called interactively, switch to process buffer
  (if (called-interactively-p 'any)
      (switch-to-buffer valeri-process-buffer)))

(defun valeri-prompt-line ()
  (save-excursion
    (save-match-data
      (forward-line 0)
      (if (looking-at comint-prompt-regexp)
          (match-end 0)))))

(defun valeri-comint-end-of-output-p (output)
  "Return non-nil if OUTPUT ends with input prompt."
  (string-match
   ;; XXX: It seems on macOS an extra carriage return is attached
   ;; at the end of output, this handles that too.
   (concat
    "\r?\n?"
    ;; Remove initial caret from calculated regexp
    (replace-regexp-in-string
     (rx string-start ?^) ""
     valeri-prompt-regexp)
    (rx eos))
   output))


(provide 'valeri-mode)

;;; valeri-mode.el ends here