(require 'helm)
(require 'quelpa)
(require 'magit)

(defvar helm-source-quelpa
  '((name . "quelpa installed packages")
    (candidates . helm-quelpa-candidates)
    (display-to-real . intern)
    (action ("View README or source" . helm-quelpa-view-readme-or-src)
            ("Magit log" . helm-quelpa-magit-log)
            ("Open directory" . helm-quelpa-open-dired)
            ("Find source" . helm-quelpa-find-src))))

(defun helm-quelpa-candidates ()
  (mapcar 'car quelpa-cache))

(defun helm-quelpa-interactive ()
  (list (completing-read "Package: " (helm-quelpa-candidates) nil t)))

(defun helm-quelpa-open-dired (package)
  (interactive (helm-quelpa-interactive))
  (dired (helm-quelpa-package-directory package)))
(defun helm-quelpa-package-directory (package)
  (expand-file-name (symbol-name package) quelpa-build-dir))

(defun helm-quelpa-view-readme-or-src (package)
  (interactive (helm-quelpa-interactive))
  (cl-loop for file in (list "README.md" "README.org" (format "%s.el" package))
           for path = (expand-file-name file (helm-quelpa-package-directory package))
           when (file-exists-p path)
           return (view-file path)))
(defun helm-quelpa-find-src (package)
  (interactive (helm-quelpa-interactive))
  (find-file (expand-file-name (format "%s.el" package)
                               (helm-quelpa-package-directory package))))

(defun helm-quelpa-magit-log (package)
  (interactive (helm-quelpa-interactive))
  (let ((default-directory (helm-quelpa-package-directory package)))
    (magit-status (helm-quelpa-package-directory package))
    (magit-log)))

(defun helm-quelpa ()
  "Helm interface for installed quelpa packages.

- View README
- View git log
- Open directory
- Open source file
"
  (interactive)
  (helm :sources 'helm-source-quelpa :buffer "*helm quelpa*"))