;;; my-hiedb.el -- Extensions for hiedb -*- lexical-binding: t -*-

;; Copyright (C) 2023 Free Software Foundation.

;; Author: Yuchen Pei <id@ypei.org>
;; Package-Requires: ((emacs "28.2"))

;; This file is part of dotfiles.

;; dotfiles is free software: you can redistribute it and/or modify it under
;; the terms of the GNU Affero General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; dotfiles 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 Affero General
;; Public License for more details.

;; You should have received a copy of the GNU Affero General Public
;; License along with dotfiles.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; Extensions for hiedb.

;;; Code:

;;; to use, do for example:
;; (add-hook 'haskell-mode-hook
;;           (lambda ()
;;             (add-hook 'xref-backend-functions
;;                       #'hiedb--xref-backend nil t)))

(defun hiedb--xref-backend () 'hiedb)

(cl-defmethod xref-backend-definitions
  ((_backend (eql hiedb)) _identifiers)
  (my-hiedb-call-point-defs buffer-file-name
                         (1+ (current-line)) (1+ (current-column)))
  (my-hiedb-parse-point-defs-output
   (file-name-directory buffer-file-name)
   (with-current-buffer "*hiedb*"
     (goto-char (point-min)) (kill-line) (kill-line)
     (buffer-string))
   ))

(defun my-hiedb-call-point-defs (file line col)
  (let ((dir (file-name-directory file))
        (module-name (file-name-base file)))
    (with-current-buffer (get-buffer-create "*hiedb*")
      (erase-buffer))
    (call-process "hiedb" nil "*hiedb*" nil
                  "-D"
                  (format "%sdefault.hiedb" dir)
                  "point-defs" module-name
                  (number-to-string line)
                  (number-to-string col))))

(defun my-hiedb-parse-point-defs-output (dir output)
  "module-name:line-begin:col-begin-line-end:col-end"
  (pcase-let ((`(,module-name ,line-beg ,col-beg, line-end, col-end)
               (split-string output "[:-]" (print output))))
    (list
     (xref-make-match
      "" (xref-make-file-location
          (format "%s%s.hs" dir module-name)
          (string-to-number line-beg)
          (string-to-number col-beg))
      (- (string-to-number col-end) (string-to-number col-beg))))))

(provide 'my-hiedb)
;;; my-hiedb.el ends here