(use-package flycheck
  :ensure t
  :defer t
  :preface (progn
             (defun check-source-predicate ()
               (and (executable-find "check.pex")
                    (buffer-file-name)
                    (string-match "src/source/.*\.py$" (buffer-file-name)))))
  :init
  (progn
    (add-hook 'prog-mode-hook 'flycheck-mode)
    (setq-default flycheck-disabled-checkers '(emacs-lisp-checkdoc)))
  :config
  (progn
    (setq flycheck-mode-line
      '(:eval
        (pcase flycheck-last-status-change
          (`not-checked nil)
          (`no-checker (propertize " -" 'face 'warning))
          (`running "")
          (`errored (propertize " ✘" 'face 'error))
          (`finished
           (if flycheck-current-errors
               (let* ((error-counts (flycheck-count-errors flycheck-current-errors))
                      (no-errors (cdr (assq 'error error-counts)))
                      (no-warnings (cdr (assq 'warning error-counts)))
                      (flycheck-face (cond (no-errors 'error)
                                           (no-warnings 'warning))))
                 (propertize (format " [✗:%s/%s]" (or no-errors 0) (or no-warnings 0)) 'face flycheck-face))
             (propertize " [✓]" 'face 'success)))
          (`interrupted " -")
          (`suspicious '(propertize " ?" 'face 'warning)))))

    (flycheck-define-checker source-check
      "A syntax checker for python source code in Source, using `check.pex'"
      :command ("check.pex" source)
      ;;; errors are reported like this:
      ;;; E241:ERROR   <file name>:<line> <message>
      :error-patterns ((error line-start (id (1+ nonl)) ":ERROR" (1+ nonl) ":" line (message) line-end)
                       (warning line-start (id (1+ nonl)) ":WARNING" (1+ nonl) ":" line (message) line-end))
      :predicate check-source-predicate
      :modes (python-mode))
    (add-to-list 'flycheck-checkers 'source-check)))

(use-package flycheck-pos-tip
  :defer t
  :init
  (progn
    (eval-after-load 'feature-flycheck
      '(setq-default flycheck-display-errors-function #'flycheck-pos-tip-error-messages)))
  :ensure t)

(provide 'core-flycheck)