;;; fcomp.el --- fcomp front-end                     -*- lexical-binding: t; -*-

;; Copyright (C) 2019  Anastasis Grammenos

;; Author: Anastasis Grammenos <anastasis.gramm2@gmail.com>
;; Keywords: lisp
;; Version: 0.0.1

;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Emacs front-end for fcomp. Get it from https://ubuntos.dynu.net/git/fcomp

;;; Install:

;; git clone https://ubuntos.dynu.net/git/fcomp && cd fcomp
;; make && make install # install copies the binary under /usr/local/bin

;; In the emacs init file:
;; (add-to-list 'load-path "/your/custom/path")
;; (require 'fcomp)
;; (setq fcomp-path "/your/custom/path/fcomp")
;; (global-set-key (kbd "C-<tab>") 'fcomp-autocomplete)

;; or with use-package
;; (use-package fcomp
;;   :load-path "/your/custom/path"
;;   :bind (("C-<tab>" . fcomp-autocomplete))
;;   :config
;;   (setq fcomp-path "/your/custom/path/fcomp"))


;;; Code:

(require 'ido)
(require 'subr-x)

;; User variables

(defvar fcomp-path "/usr/local/bin/fcomp"
  "Path to fcomp executable.")
(defvar fcomp-min-word-length 3
  "Minimum word length to be counted as token.")
(defvar fcomp-extra-valid-chars ""
  "Extra valid chars for the tokenization.")
(defvar fcomp-extra-invalid-chars ""
  "Extra invalid chars for the tokenization.")
(defvar fcomp-completing-read-func 'completing-read
  "Function to call when showing results to user.")

(defun empty-string-p (string)
  "Return true if the string is empty or nil. Expects string."
  (or (null string)
      (zerop (length (string-trim string)))))

(defun fcomp--start (query)
  "Initiaize fcomp variables"
  (setq fcomp--query query)
  (setq fcomp--output ""))

(defun fcomp--filter (proc str)
  "Fill the output buffer"
  (let* ((fcomp-pre
          (if (empty-string-p (process-get proc 'input-word))
              nil
            (format "%s" (process-get proc 'input-word)))))
    (setq fcomp--output (concat fcomp--output str))))

(defun fcomp--handle-output ()
  "Handle output buffer"
  (let ((initial-input fcomp--query)
        (out-string fcomp--output)
        (result nil))
    (if (empty-string-p fcomp--output)
        nil
      (setq result
            (funcall fcomp-completing-read-func
                     "Complete:"
                     (remove "" (split-string fcomp--output "\n"))
                     nil nil
                     initial-input)))
  (if (empty-string-p result)
        (message "%s" "No completion candidates")
      (insert (string-remove-prefix
               (if (empty-string-p initial-input)
                   (format "%s" "")
                 (format "%s" initial-input))
               result)))
    (setq fcomp--query "")
    (setq fcomp--output "")))

(defun fcomp--autocomplete (word point &optional x)
  "Start fcomp process and orchistrate it's output."
  (let ((term (if (empty-string-p word)
                  (format "%s" "-au")
                (format "%s" word)))
        (input-len (buffer-size)))
    (fcomp--start word)
    (setq proc
          (start-process
           "fcomp"
           nil
           (format "%s" fcomp-path)
           "-w" (format "%s" fcomp-min-word-length)
           "-v" (format "\"%s\"" fcomp-extra-valid-chars)
           "-i" (format "\"%s\"" fcomp-extra-invalid-chars)
           term))
    (set-process-filter proc #'fcomp--filter)
    (set-process-coding-system proc 'raw-text-unix 'raw-text-unix)
    (process-put proc 'input-word word)
    (if (< input-len 50000)
        (process-send-region proc (point-min) (point-max))
      (process-send-region proc
                           (if (< (- point 25000) 0) (point-min) (- point 25000))
                           (if (> (+ point 25000) input-len) (point-max) (+ point 25000))))
    (process-send-string proc "\n")
    (process-send-eof proc)
    (if (accept-process-output proc nil nil t)
        (unless x
            (fcomp--handle-output))
      (progn
        (unless x
          (message "No completion for %s" word))
        (delete-process proc)))))

(defun fcomp--make-syntax-table ()
  "Modifies the current active sytanx table to include '_', '-'
and `fcomp-extra-valid-chars' as part of a word."
  ;; Thanks Dan for the syntax-table trick
  ;; https://emacs.stackexchange.com/questions/9583/how-to-treat-underscore-as-part-of-the-word
  (let ((table (copy-syntax-table (syntax-table))))
    (when (not (empty-string-p fcomp-extra-valid-chars))
      (mapc (lambda (char) (modify-syntax-entry char "w" table)) fcomp-extra-valid-chars))
    (modify-syntax-entry ?- "w" table)
    (modify-syntax-entry ?_ "w" table)
    (copy-syntax-table table)))

(defun fcomp-get-canditates (word)
  "Return a list of candidates for WORD curated by fcomp."
  (progn
    (fcomp--autocomplete word (point) t))
    (remove "" (split-string fcomp--output "\n")))

(defun fcomp-autocomplete ()
  "Autocompete using fcomp.c

When `thing-at-point' is a word, autocomplete it based on buffer contents.

When invoked with no `thing-at-point' show a list of all possible candidates.

The syntax-table is temporarily modified and includes '_', '-' and
`fcomp-extra-valid-chars' as part of a word.

Requires fcomp. Get it at URL `https://git.eyesin.space/git/fcomp'"
  (interactive)
  (with-syntax-table (fcomp--make-syntax-table)
    (fcomp--autocomplete (thing-at-point 'word 'no-properties) (point))))

(provide 'fcomp)
;;; fcomp.el ends here