emacs: Add Hydra interface.

* emacs/guix-utils.el (guix-hexify, guix-number->bool): New procedures.
  (guix-while-null): New macro.
* emacs/guix-hydra.el: New file.
* emacs/guix-hydra-build.el: New file.
* emacs/guix-hydra-jobset.el: New file.
* emacs.am (ELFILES): Add them.
* doc/emacs.texi (Emacs Hydra): New node.
  (Emacs Interface): Add it.
* doc/guix.texi (Top): Add it.
  (Substitutes): Mention Emacs interface.

4 files changed, 907 insertions, 0 deletions

diff --git a/emacs/guix-hydra-build.el b/emacs/guix-hydra-build.el
new file mode 100644
index 0000000000..232221e773
--- /dev/null
+++ b/emacs/guix-hydra-build.el
@@ -0,0 +1,362 @@
+;;; guix-hydra-build.el --- Interface for Hydra builds  -*- lexical-binding: t -*-
+
+;; Copyright © 2015 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix 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.
+
+;; GNU Guix 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:
+
+;; This file provides an interface for displaying Hydra builds in
+;; 'list' and 'info' buffers.
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'guix-buffer)
+(require 'guix-list)
+(require 'guix-info)
+(require 'guix-hydra)
+(require 'guix-build-log)
+(require 'guix-utils)
+
+(guix-hydra-define-entry-type hydra-build
+  :search-types '((latest . guix-hydra-build-latest-api-url)
+                  (queue  . guix-hydra-build-queue-api-url))
+  :filters '(guix-hydra-build-filter-status)
+  :filter-names '((nixname . name)
+                  (buildstatus . build-status)
+                  (timestamp . time))
+  :filter-boolean-params '(finished busy))
+
+(defun guix-hydra-build-get-display (search-type &rest args)
+  "Search for Hydra builds and show results."
+  (apply #'guix-list-get-display-entries
+         'hydra-build search-type args))
+
+(cl-defun guix-hydra-build-latest-prompt-args (&key project jobset
+                                                    job system)
+  "Prompt for and return a list of 'latest builds' arguments."
+  (let* ((number      (read-number "Number of latest builds: "))
+         (project     (if current-prefix-arg
+                          (guix-hydra-read-project nil project)
+                        project))
+         (jobset      (if current-prefix-arg
+                          (guix-hydra-read-jobset nil jobset)
+                        jobset))
+         (job-or-name (if current-prefix-arg
+                          (guix-hydra-read-job nil job)
+                        job))
+         (job         (and job-or-name
+                           (string-match-p guix-hydra-job-regexp
+                                           job-or-name)
+                           job-or-name))
+         (system      (if (and (not job)
+                               (or current-prefix-arg
+                                   (and job-or-name (not system))))
+                          (if job-or-name
+                              (guix-while-null
+                                (guix-hydra-read-system
+                                 (concat job-or-name ".") system))
+                            (guix-hydra-read-system nil system))
+                        system))
+         (job         (or job
+                          (and job-or-name
+                               (concat job-or-name "." system)))))
+    (list number
+          :project project
+          :jobset  jobset
+          :job     job
+          :system  system)))
+
+(defun guix-hydra-build-view-log (id)
+  "View build log of a hydra build ID."
+  (guix-build-log-find-file (guix-hydra-build-log-url id)))
+
+
+;;; Defining URLs
+
+(defun guix-hydra-build-url (id)
+  "Return Hydra URL of a build ID."
+  (guix-hydra-url "build/" (number-to-string id)))
+
+(defun guix-hydra-build-log-url (id)
+  "Return Hydra URL of the log file of a build ID."
+  (concat (guix-hydra-build-url id) "/log/raw"))
+
+(cl-defun guix-hydra-build-latest-api-url
+    (number &key project jobset job system)
+  "Return Hydra API URL to receive latest NUMBER of builds."
+  (guix-hydra-api-url "latestbuilds"
+    `(("nr" . ,number)
+      ("project" . ,project)
+      ("jobset" . ,jobset)
+      ("job" . ,job)
+      ("system" . ,system))))
+
+(defun guix-hydra-build-queue-api-url (number)
+  "Return Hydra API URL to receive the NUMBER of queued builds."
+  (guix-hydra-api-url "queue"
+    `(("nr" . ,number))))
+
+
+;;; Filters for processing raw entries
+
+(defun guix-hydra-build-filter-status (entry)
+  "Add 'status' parameter to 'hydra-build' ENTRY."
+  (let ((status (if (guix-entry-value entry 'finished)
+                    (guix-hydra-build-status-number->name
+                     (guix-entry-value entry 'build-status))
+                  (if (guix-entry-value entry 'busy)
+                      'running
+                    'scheduled))))
+    (cons `(status . ,status)
+          entry)))
+
+
+;;; Build status
+
+(defface guix-hydra-build-status-running
+  '((t :inherit bold))
+  "Face used if hydra build is not finished."
+  :group 'guix-hydra-build-faces)
+
+(defface guix-hydra-build-status-scheduled
+  '((t))
+  "Face used if hydra build is scheduled."
+  :group 'guix-hydra-build-faces)
+
+(defface guix-hydra-build-status-succeeded
+  '((t :inherit success))
+  "Face used if hydra build succeeded."
+  :group 'guix-hydra-build-faces)
+
+(defface guix-hydra-build-status-cancelled
+  '((t :inherit warning))
+  "Face used if hydra build was cancelled."
+  :group 'guix-hydra-build-faces)
+
+(defface guix-hydra-build-status-failed
+  '((t :inherit error))
+  "Face used if hydra build failed."
+  :group 'guix-hydra-build-faces)
+
+(defvar guix-hydra-build-status-alist
+  '((0 . succeeded)
+    (1 . failed-build)
+    (2 . failed-dependency)
+    (3 . failed-other)
+    (4 . cancelled))
+  "Alist of hydra build status numbers and status names.
+Status numbers are returned by Hydra API, names (symbols) are
+used internally by the elisp code of this package.")
+
+(defun guix-hydra-build-status-number->name (number)
+  "Convert build status number to a name.
+See `guix-hydra-build-status-alist'."
+  (guix-assq-value guix-hydra-build-status-alist number))
+
+(defun guix-hydra-build-status-string (status)
+  "Return a human readable string for build STATUS."
+  (cl-case status
+    (scheduled
+     (guix-get-string "Scheduled" 'guix-hydra-build-status-scheduled))
+    (running
+     (guix-get-string "Running" 'guix-hydra-build-status-running))
+    (succeeded
+     (guix-get-string "Succeeded" 'guix-hydra-build-status-succeeded))
+    (cancelled
+     (guix-get-string "Cancelled" 'guix-hydra-build-status-cancelled))
+    (failed-build
+     (guix-hydra-build-status-fail-string))
+    (failed-dependency
+     (guix-hydra-build-status-fail-string "dependency"))
+    (failed-other
+     (guix-hydra-build-status-fail-string "other"))))
+
+(defun guix-hydra-build-status-fail-string (&optional reason)
+  "Return a string for a failed build."
+  (let ((base (guix-get-string "Failed" 'guix-hydra-build-status-failed)))
+    (if reason
+        (concat base " (" reason ")")
+      base)))
+
+(defun guix-hydra-build-finished? (entry)
+  "Return non-nil, if hydra build was finished."
+  (guix-entry-value entry 'finished))
+
+(defun guix-hydra-build-running? (entry)
+  "Return non-nil, if hydra build is running."
+  (eq (guix-entry-value entry 'status)
+      'running))
+
+(defun guix-hydra-build-scheduled? (entry)
+  "Return non-nil, if hydra build is scheduled."
+  (eq (guix-entry-value entry 'status)
+      'scheduled))
+
+(defun guix-hydra-build-succeeded? (entry)
+  "Return non-nil, if hydra build succeeded."
+  (eq (guix-entry-value entry 'status)
+      'succeeded))
+
+(defun guix-hydra-build-cancelled? (entry)
+  "Return non-nil, if hydra build was cancelled."
+  (eq (guix-entry-value entry 'status)
+      'cancelled))
+
+(defun guix-hydra-build-failed? (entry)
+  "Return non-nil, if hydra build failed."
+  (memq (guix-entry-value entry 'status)
+        '(failed-build failed-dependency failed-other)))
+
+
+;;; Hydra build 'info'
+
+(guix-hydra-info-define-interface hydra-build
+  :mode-name "Hydra-Build-Info"
+  :buffer-name "*Guix Hydra Build Info*"
+  :format '((name ignore (simple guix-info-heading))
+            ignore
+            guix-hydra-build-info-insert-url
+            (time     format (time))
+            (status   format guix-hydra-build-info-insert-status)
+            (project  format (format guix-hydra-build-project))
+            (jobset   format (format guix-hydra-build-jobset))
+            (job      format (format guix-hydra-build-job))
+            (system   format (format guix-hydra-build-system))
+            (priority format (format))))
+
+(defface guix-hydra-build-info-project
+  '((t :inherit link))
+  "Face for project names."
+  :group 'guix-hydra-build-info-faces)
+
+(defface guix-hydra-build-info-jobset
+  '((t :inherit link))
+  "Face for jobsets."
+  :group 'guix-hydra-build-info-faces)
+
+(defface guix-hydra-build-info-job
+  '((t :inherit link))
+  "Face for jobs."
+  :group 'guix-hydra-build-info-faces)
+
+(defface guix-hydra-build-info-system
+  '((t :inherit link))
+  "Face for system names."
+  :group 'guix-hydra-build-info-faces)
+
+(defmacro guix-hydra-build-define-button (name)
+  "Define `guix-hydra-build-NAME' button."
+  (let* ((name-str    (symbol-name name))
+         (button-name (intern (concat "guix-hydra-build-" name-str)))
+         (face-name   (intern (concat "guix-hydra-build-info-" name-str)))
+         (keyword     (intern (concat ":" name-str))))
+    `(define-button-type ',button-name
+       :supertype 'guix
+       'face ',face-name
+       'help-echo ,(format "\
+Show latest builds for this %s (with prefix, prompt for all parameters)"
+                           name-str)
+       'action (lambda (btn)
+                 (let ((args (guix-hydra-build-latest-prompt-args
+                              ,keyword (button-label btn))))
+                   (apply #'guix-hydra-build-get-display
+                          'latest args))))))
+
+(guix-hydra-build-define-button project)
+(guix-hydra-build-define-button jobset)
+(guix-hydra-build-define-button job)
+(guix-hydra-build-define-button system)
+
+(defun guix-hydra-build-info-insert-url (entry)
+  "Insert Hydra URL for the build ENTRY."
+  (guix-insert-button (guix-hydra-build-url (guix-entry-id entry))
+                      'guix-url)
+  (when (guix-hydra-build-finished? entry)
+    (guix-info-insert-indent)
+    (guix-info-insert-action-button
+     "Build log"
+     (lambda (btn)
+       (guix-hydra-build-view-log (button-get btn 'id)))
+     "View build log"
+     'id (guix-entry-id entry))))
+
+(defun guix-hydra-build-info-insert-status (status &optional _)
+  "Insert a string with build STATUS."
+  (insert (guix-hydra-build-status-string status)))
+
+
+;;; Hydra build 'list'
+
+(guix-hydra-list-define-interface hydra-build
+  :mode-name "Hydra-Build-List"
+  :buffer-name "*Guix Hydra Build List*"
+  :format '((name nil 30 t)
+            (system nil 16 t)
+            (status guix-hydra-build-list-get-status 20 t)
+            (project nil 10 t)
+            (jobset nil 17 t)
+            (time guix-list-get-time 20 t)))
+
+(let ((map guix-hydra-build-list-mode-map))
+  (define-key map (kbd "B") 'guix-hydra-build-list-latest-builds)
+  (define-key map (kbd "L") 'guix-hydra-build-list-view-log))
+
+(defun guix-hydra-build-list-get-status (status &optional _)
+  "Return a string for build STATUS."
+  (guix-hydra-build-status-string status))
+
+(defun guix-hydra-build-list-latest-builds (number &rest args)
+  "Display latest NUMBER of Hydra builds of the current job.
+Interactively, prompt for NUMBER.  With prefix argument, prompt
+for all ARGS."
+  (interactive
+   (let ((entry (guix-list-current-entry)))
+     (guix-hydra-build-latest-prompt-args
+      :project (guix-entry-value entry 'project)
+      :jobset  (guix-entry-value entry 'name)
+      :job     (guix-entry-value entry 'job)
+      :system  (guix-entry-value entry 'system))))
+  (apply #'guix-hydra-latest-builds number args))
+
+(defun guix-hydra-build-list-view-log ()
+  "View build log of the current Hydra build."
+  (interactive)
+  (guix-hydra-build-view-log (guix-list-current-id)))
+
+
+;;; Interactive commands
+
+;;;###autoload
+(defun guix-hydra-latest-builds (number &rest args)
+  "Display latest NUMBER of Hydra builds.
+ARGS are the same arguments as for `guix-hydra-build-latest-api-url'.
+Interactively, prompt for NUMBER.  With prefix argument, prompt
+for all ARGS."
+  (interactive (guix-hydra-build-latest-prompt-args))
+  (apply #'guix-hydra-build-get-display
+         'latest number args))
+
+;;;###autoload
+(defun guix-hydra-queued-builds (number)
+  "Display the NUMBER of queued Hydra builds."
+  (interactive "NNumber of queued builds: ")
+  (guix-hydra-build-get-display 'queue number))
+
+(provide 'guix-hydra-build)
+
+;;; guix-hydra-build.el ends here
diff --git a/emacs/guix-hydra-jobset.el b/emacs/guix-hydra-jobset.el
new file mode 100644
index 0000000000..a4a55a36f2
--- /dev/null
+++ b/emacs/guix-hydra-jobset.el
@@ -0,0 +1,162 @@
+;;; guix-hydra-jobset.el --- Interface for Hydra jobsets  -*- lexical-binding: t -*-
+
+;; Copyright © 2015 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix 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.
+
+;; GNU Guix 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:
+
+;; This file provides an interface for displaying Hydra jobsets in
+;; 'list' and 'info' buffers.
+
+;;; Code:
+
+(require 'cl-lib)
+(require 'guix-buffer)
+(require 'guix-list)
+(require 'guix-info)
+(require 'guix-hydra)
+(require 'guix-hydra-build)
+(require 'guix-utils)
+
+(guix-hydra-define-entry-type hydra-jobset
+  :search-types '((project . guix-hydra-jobset-api-url))
+  :filters '(guix-hydra-jobset-filter-id)
+  :filter-names '((nrscheduled . scheduled)
+                  (nrsucceeded . succeeded)
+                  (nrfailed . failed)
+                  (nrtotal . total)))
+
+(defun guix-hydra-jobset-get-display (search-type &rest args)
+  "Search for Hydra builds and show results."
+  (apply #'guix-list-get-display-entries
+         'hydra-jobset search-type args))
+
+
+;;; Defining URLs
+
+(defun guix-hydra-jobset-url (project jobset)
+  "Return Hydra URL of a PROJECT's JOBSET."
+  (guix-hydra-url "jobset/" project "/" jobset))
+
+(defun guix-hydra-jobset-api-url (project)
+  "Return Hydra API URL for jobsets by PROJECT."
+  (guix-hydra-api-url "jobsets"
+    `(("project" . ,project))))
+
+
+;;; Filters for processing raw entries
+
+(defun guix-hydra-jobset-filter-id (entry)
+  "Add 'ID' parameter to 'hydra-jobset' ENTRY."
+  (cons `(id . ,(guix-entry-value entry 'name))
+        entry))
+
+
+;;; Hydra jobset 'info'
+
+(guix-hydra-info-define-interface hydra-jobset
+  :mode-name "Hydra-Jobset-Info"
+  :buffer-name "*Guix Hydra Jobset Info*"
+  :format '((name ignore (simple guix-info-heading))
+            ignore
+            guix-hydra-jobset-info-insert-url
+            (project   format guix-hydra-jobset-info-insert-project)
+            (scheduled format (format guix-hydra-jobset-info-scheduled))
+            (succeeded format (format guix-hydra-jobset-info-succeeded))
+            (failed    format (format guix-hydra-jobset-info-failed))
+            (total     format (format guix-hydra-jobset-info-total))))
+
+(defface guix-hydra-jobset-info-scheduled
+  '((t))
+  "Face used for the number of scheduled builds."
+  :group 'guix-hydra-jobset-info-faces)
+
+(defface guix-hydra-jobset-info-succeeded
+  '((t :inherit guix-hydra-build-status-succeeded))
+  "Face used for the number of succeeded builds."
+  :group 'guix-hydra-jobset-info-faces)
+
+(defface guix-hydra-jobset-info-failed
+  '((t :inherit guix-hydra-build-status-failed))
+  "Face used for the number of failed builds."
+  :group 'guix-hydra-jobset-info-faces)
+
+(defface guix-hydra-jobset-info-total
+  '((t))
+  "Face used for the total number of builds."
+  :group 'guix-hydra-jobset-info-faces)
+
+(defun guix-hydra-jobset-info-insert-project (project entry)
+  "Insert PROJECT button for the jobset ENTRY."
+  (let ((jobset (guix-entry-value entry 'name)))
+    (guix-insert-button
+     project 'guix-hydra-build-project
+     'action (lambda (btn)
+               (let ((args (guix-hydra-build-latest-prompt-args
+                            :project (button-get btn 'project)
+                            :jobset  (button-get btn 'jobset))))
+                 (apply #'guix-hydra-build-get-display
+                        'latest args)))
+     'project project
+     'jobset jobset)))
+
+(defun guix-hydra-jobset-info-insert-url (entry)
+  "Insert Hydra URL for the jobset ENTRY."
+  (guix-insert-button (guix-hydra-jobset-url
+                       (guix-entry-value entry 'project)
+                       (guix-entry-value entry 'name))
+                      'guix-url))
+
+
+;;; Hydra jobset 'list'
+
+(guix-hydra-list-define-interface hydra-jobset
+  :mode-name "Hydra-Jobset-List"
+  :buffer-name "*Guix Hydra Jobset List*"
+  :format '((name nil 25 t)
+            (project nil 10 t)
+            (scheduled nil 12 t)
+            (succeeded nil 12 t)
+            (failed nil 9 t)
+            (total nil 10 t)))
+
+(let ((map guix-hydra-jobset-list-mode-map))
+  (define-key map (kbd "B") 'guix-hydra-jobset-list-latest-builds))
+
+(defun guix-hydra-jobset-list-latest-builds (number &rest args)
+  "Display latest NUMBER of Hydra builds of the current jobset.
+Interactively, prompt for NUMBER.  With prefix argument, prompt
+for all ARGS."
+  (interactive
+   (let ((entry (guix-list-current-entry)))
+     (guix-hydra-build-latest-prompt-args
+      :project (guix-entry-value entry 'project)
+      :jobset  (guix-entry-value entry 'name))))
+  (apply #'guix-hydra-latest-builds number args))
+
+
+;;; Interactive commands
+
+;;;###autoload
+(defun guix-hydra-jobsets (project)
+  "Display jobsets of PROJECT."
+  (interactive (list (guix-hydra-read-project)))
+  (guix-hydra-jobset-get-display 'project project))
+
+(provide 'guix-hydra-jobset)
+
+;;; guix-hydra-jobset.el ends here
diff --git a/emacs/guix-hydra.el b/emacs/guix-hydra.el
new file mode 100644
index 0000000000..429483946b
--- /dev/null
+++ b/emacs/guix-hydra.el
@@ -0,0 +1,363 @@
+;;; guix-hydra.el --- Common code for interacting with Hydra  -*- lexical-binding: t -*-
+
+;; Copyright © 2015 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix 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.
+
+;; GNU Guix 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:
+
+;; This file provides some general code for 'list'/'info' interfaces for
+;; Hydra (Guix build farm).
+
+;;; Code:
+
+(require 'json)
+(require 'guix-buffer)
+(require 'guix-entry)
+(require 'guix-utils)
+(require 'guix-help-vars)
+
+(guix-define-groups hydra)
+
+(defvar guix-hydra-job-regexp
+  (concat ".*\\." (regexp-opt guix-help-system-types) "\\'")
+  "Regexp matching a full name of Hydra job (including system).")
+
+(defun guix-hydra-message (entries search-type &rest _)
+  "Display a message after showing Hydra ENTRIES."
+  ;; XXX Add more messages maybe.
+  (when (null entries)
+    (if (eq search-type 'fake)
+        (message "The update is impossible due to lack of Hydra API.")
+      (message "Hydra has returned no results."))))
+
+(defun guix-hydra-list-describe (ids)
+  "Describe 'hydra' entries with IDS (list of identifiers)."
+  (guix-buffer-display-entries
+   (guix-entries-by-ids ids (guix-buffer-current-entries))
+   'info (guix-buffer-current-entry-type)
+   ;; Hydra does not provide an API to receive builds/jobsets by
+   ;; IDs/names, so we use a 'fake' search type.
+   '(fake)
+   'add))
+
+
+;;; Readers
+
+(defvar guix-hydra-projects
+  '("gnu" "guix")
+  "List of available Hydra projects.")
+
+(guix-define-readers
+ :completions-var guix-hydra-projects
+ :single-reader guix-hydra-read-project
+ :single-prompt "Project: ")
+
+(guix-define-readers
+ :single-reader guix-hydra-read-jobset
+ :single-prompt "Jobset: ")
+
+(guix-define-readers
+ :single-reader guix-hydra-read-job
+ :single-prompt "Job: ")
+
+(guix-define-readers
+ :completions-var guix-help-system-types
+ :single-reader guix-hydra-read-system
+ :single-prompt "System: ")
+
+
+;;; Defining URLs
+
+(defvar guix-hydra-url "http://hydra.gnu.org"
+  "URL of the Hydra build farm.")
+
+(defun guix-hydra-url (&rest url-parts)
+  "Return Hydra URL."
+  (apply #'concat guix-hydra-url "/" url-parts))
+
+(defun guix-hydra-api-url (type args)
+  "Return URL for receiving data using Hydra API.
+TYPE is the name of an allowed method.
+ARGS is alist of (KEY . VALUE) pairs.
+Skip ARG, if VALUE is nil or an empty string."
+  (declare (indent 1))
+  (let* ((fields (mapcar
+                  (lambda (arg)
+                    (pcase arg
+                      (`(,key . ,value)
+                       (unless (or (null value)
+                                   (equal "" value))
+                         (concat (guix-hexify key) "="
+                                 (guix-hexify value))))
+                      (_ (error "Wrong argument '%s'" arg))))
+                  args))
+         (fields (mapconcat #'identity (delq nil fields) "&")))
+    (guix-hydra-url "api/" type "?" fields)))
+
+
+;;; Receiving data from Hydra
+
+(defun guix-hydra-receive-data (url)
+  "Return output received from URL and processed with `json-read'."
+  (with-temp-buffer
+    (url-insert-file-contents url)
+    (goto-char (point-min))
+    (let ((json-key-type 'symbol)
+          (json-array-type 'list)
+          (json-object-type 'alist))
+      (json-read))))
+
+(defun guix-hydra-get-entries (entry-type search-type &rest args)
+  "Receive ENTRY-TYPE entries from Hydra.
+SEARCH-TYPE is one of the types defined by `guix-hydra-define-interface'."
+  (unless (eq search-type 'fake)
+    (let* ((url         (apply #'guix-hydra-search-url
+                               entry-type search-type args))
+           (raw-entries (guix-hydra-receive-data url))
+           (entries     (guix-hydra-filter-entries
+                         raw-entries
+                         (guix-hydra-filters entry-type))))
+      entries)))
+
+
+;;; Filters for processing raw entries
+
+(defun guix-hydra-filter-entries (entries filters)
+  "Filter ENTRIES using FILTERS.
+Call `guix-modify' on each entry from ENTRIES."
+  (mapcar (lambda (entry)
+            (guix-modify entry filters))
+          entries))
+
+(defun guix-hydra-filter-names (entry name-alist)
+  "Replace names of ENTRY parameters using NAME-ALIST.
+Each element of NAME-ALIST is (OLD-NAME . NEW-NAME) pair."
+  (mapcar (lambda (param)
+            (pcase param
+              (`(,name . ,val)
+               (let ((new-name (guix-assq-value name-alist name)))
+                 (if new-name
+                     (cons new-name val)
+                   param)))))
+          entry))
+
+(defun guix-hydra-filter-boolean (entry params)
+  "Convert number PARAMS (0/1) of ENTRY to boolean values (nil/t)."
+  (mapcar (lambda (param)
+            (pcase param
+              (`(,name . ,val)
+               (if (memq name params)
+                   (cons name (guix-number->bool val))
+                 param))))
+          entry))
+
+
+;;; Wrappers for defined variables
+
+(defvar guix-hydra-entry-type-data nil
+  "Alist with hydra entry type data.
+This alist is filled by `guix-hydra-define-entry-type' macro.")
+
+(defun guix-hydra-entry-type-value (entry-type symbol)
+  "Return SYMBOL's value for ENTRY-TYPE from `guix-hydra'."
+  (symbol-value (guix-assq-value guix-hydra-entry-type-data
+                                 entry-type symbol)))
+
+(defun guix-hydra-search-url (entry-type search-type &rest args)
+  "Return URL to receive ENTRY-TYPE entries from Hydra."
+  (apply (guix-assq-value (guix-hydra-entry-type-value
+                           entry-type 'search-types)
+                          search-type)
+         args))
+
+(defun guix-hydra-filters (entry-type)
+  "Return a list of filters for ENTRY-TYPE."
+  (guix-hydra-entry-type-value entry-type 'filters))
+
+
+;;; Interface definers
+
+(defmacro guix-hydra-define-entry-type (entry-type &rest args)
+  "Define general code for ENTRY-TYPE.
+Remaining arguments (ARGS) should have a form [KEYWORD VALUE] ...
+
+Required keywords:
+
+  - `:search-types' - default value of the generated
+    `guix-ENTRY-TYPE-search-types' variable.
+
+Optional keywords:
+
+  - `:filters' - default value of the generated
+    `guix-ENTRY-TYPE-filters' variable.
+
+  - `:filter-names' - if specified, a generated
+    `guix-ENTRY-TYPE-filter-names' function for filtering these
+    names will be added to `guix-ENTRY-TYPE-filters' variable.
+
+  - `:filter-boolean-params' - if specified, a generated
+    `guix-ENTRY-TYPE-filter-boolean' function for filtering these
+    names will be added to `guix-ENTRY-TYPE-filters' variable.
+
+The rest keyword arguments are passed to
+`guix-define-entry-type' macro."
+  (declare (indent 1))
+  (let* ((entry-type-str     (symbol-name entry-type))
+         (prefix             (concat "guix-" entry-type-str))
+         (search-types-var   (intern (concat prefix "-search-types")))
+         (filters-var        (intern (concat prefix "-filters")))
+         (get-fun            (intern (concat prefix "-get-entries"))))
+    (guix-keyword-args-let args
+        ((search-types-val   :search-types)
+         (filters-val        :filters)
+         (filter-names-val   :filter-names)
+         (filter-bool-val    :filter-boolean-params))
+      `(progn
+         (defvar ,search-types-var ,search-types-val
+           ,(format "\
+Alist of search types and according URL functions.
+Functions are used to define URL to receive '%s' entries."
+                    entry-type-str))
+
+         (defvar ,filters-var ,filters-val
+           ,(format "\
+List of filters for '%s' parameters.
+Each filter is a function that should take an entry as a single
+argument, and should also return an entry."
+                    entry-type-str))
+
+         ,(when filter-bool-val
+            (let ((filter-bool-var (intern (concat prefix
+                                                   "-filter-boolean-params")))
+                  (filter-bool-fun (intern (concat prefix
+                                                   "-filter-boolean"))))
+              `(progn
+                 (defvar ,filter-bool-var ,filter-bool-val
+                   ,(format "\
+List of '%s' parameters that should be transformed to boolean values."
+                            entry-type-str))
+
+                 (defun ,filter-bool-fun (entry)
+                   ,(format "\
+Run `guix-hydra-filter-boolean' with `%S' variable."
+                            filter-bool-var)
+                   (guix-hydra-filter-boolean entry ,filter-bool-var))
+
+                 (setq ,filters-var
+                       (cons ',filter-bool-fun ,filters-var)))))
+
+         ;; Do not move this clause up!: name filtering should be
+         ;; performed before any other filtering, so this filter should
+         ;; be consed after the boolean filter.
+         ,(when filter-names-val
+            (let* ((filter-names-var (intern (concat prefix
+                                                     "-filter-names")))
+                   (filter-names-fun filter-names-var))
+              `(progn
+                 (defvar ,filter-names-var ,filter-names-val
+                   ,(format "\
+Alist of '%s' parameter names returned by Hydra API and names
+used internally by the elisp code of this package."
+                            entry-type-str))
+
+                 (defun ,filter-names-fun (entry)
+                   ,(format "\
+Run `guix-hydra-filter-names' with `%S' variable."
+                            filter-names-var)
+                   (guix-hydra-filter-names entry ,filter-names-var))
+
+                 (setq ,filters-var
+                       (cons ',filter-names-fun ,filters-var)))))
+
+         (defun ,get-fun (search-type &rest args)
+           ,(format "\
+Receive '%s' entries.
+See `guix-hydra-get-entries' for details."
+                    entry-type-str)
+           (apply #'guix-hydra-get-entries
+                  ',entry-type search-type args))
+
+         (guix-alist-put!
+          '((search-types . ,search-types-var)
+            (filters      . ,filters-var))
+          'guix-hydra-entry-type-data ',entry-type)
+
+         (guix-define-entry-type ,entry-type
+           :parent-group guix-hydra
+           :parent-faces-group guix-hydra-faces
+           ,@%foreign-args)))))
+
+(defmacro guix-hydra-define-interface (buffer-type entry-type &rest args)
+  "Define BUFFER-TYPE interface for displaying ENTRY-TYPE entries.
+
+This macro should be called after calling
+`guix-hydra-define-entry-type' with the same ENTRY-TYPE.
+
+ARGS are passed to `guix-BUFFER-TYPE-define-interface' macro."
+  (declare (indent 2))
+  (let* ((entry-type-str  (symbol-name entry-type))
+         (buffer-type-str (symbol-name buffer-type))
+         (get-fun         (intern (concat "guix-" entry-type-str
+                                          "-get-entries")))
+         (definer         (intern (concat "guix-" buffer-type-str
+                                          "-define-interface"))))
+    `(,definer ,entry-type
+       :get-entries-function ',get-fun
+       :message-function 'guix-hydra-message
+       ,@args)))
+
+(defmacro guix-hydra-info-define-interface (entry-type &rest args)
+  "Define 'info' interface for displaying ENTRY-TYPE entries.
+See `guix-hydra-define-interface'."
+  (declare (indent 1))
+  `(guix-hydra-define-interface info ,entry-type
+     ,@args))
+
+(defmacro guix-hydra-list-define-interface (entry-type &rest args)
+  "Define 'list' interface for displaying ENTRY-TYPE entries.
+Remaining arguments (ARGS) should have a form [KEYWORD VALUE] ...
+
+Optional keywords:
+
+  - `:describe-function' - default value of the generated
+    `guix-ENTRY-TYPE-list-describe-function' variable (if not
+    specified, use `guix-hydra-list-describe').
+
+The rest keyword arguments are passed to
+`guix-hydra-define-interface' macro."
+  (declare (indent 1))
+  (guix-keyword-args-let args
+      ((describe-val :describe-function))
+    `(guix-hydra-define-interface list ,entry-type
+       :describe-function ,(or describe-val ''guix-hydra-list-describe)
+       ,@args)))
+
+
+(defvar guix-hydra-font-lock-keywords
+  (eval-when-compile
+    `((,(rx "(" (group (or "guix-hydra-define-entry-type"
+                           "guix-hydra-define-interface"
+                           "guix-hydra-info-define-interface"
+                           "guix-hydra-list-define-interface"))
+            symbol-end)
+       . 1))))
+
+(font-lock-add-keywords 'emacs-lisp-mode guix-hydra-font-lock-keywords)
+
+(provide 'guix-hydra)
+
+;;; guix-hydra.el ends here
diff --git a/emacs/guix-utils.el b/emacs/guix-utils.el
index 98a408f875..8c1a5b42de 100644
--- a/emacs/guix-utils.el
+++ b/emacs/guix-utils.el
@@ -174,6 +174,15 @@ add both to the end and to the beginning."
           (t
            (concat separator str separator)))))
 
+(defun guix-hexify (value)
+  "Convert VALUE to string and hexify it."
+  (url-hexify-string (guix-get-string value)))
+
+(defun guix-number->bool (number)
+  "Convert NUMBER to boolean value.
+Return nil, if NUMBER is 0; return t otherwise."
+  (not (zerop number)))
+
 (defun guix-shell-quote-argument (argument)
   "Quote shell command ARGUMENT.
 This function is similar to `shell-quote-argument', but less strict."
@@ -282,6 +291,15 @@ single argument."
      (while (re-search-forward ,regexp nil t)
        ,@body)))
 
+(defmacro guix-while-null (&rest body)
+  "Evaluate BODY until its result becomes non-nil."
+  (declare (indent 0) (debug t))
+  (let ((result-var (make-symbol "result")))
+    `(let (,result-var)
+       (while (null ,result-var)
+         (setq ,result-var ,@body))
+       ,result-var)))
+
 (defun guix-modify (object modifiers)
   "Apply MODIFIERS to OBJECT.
 OBJECT is passed as an argument to the first function from
@@ -527,6 +545,8 @@ See `defun' for the meaning of arguments."
     `((,(rx "(" (group (or "guix-define-reader"
                            "guix-define-readers"
                            "guix-keyword-args-let"
+                           "guix-while-null"
+                           "guix-while-search"
                            "guix-with-indent"))
             symbol-end)
        . 1)