google-weather.el

   1 ;;; google-weather.el --- Fetch Google Weather forecasts.
   2
   3 ;; Copyright (C) 2010 Julien Danjou
   4
   5 ;; Author: Julien Danjou <julien@danjou.info>
   6 ;; Keywords: comm
   7
   8 ;; This file is NOT part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24 ;; This module allows you to fetch Google Weather forecast from the
  25 ;; Internet.
  26 ;;
  27 ;;; Code:
  28
  29 (require 'url)
  30 (require 'url-cache)
  31 (require 'xml)
  32 (require 'time-date)
  33
  34 (eval-when-compile
  35   (require 'cl))
  36
  37 (defgroup google-weather nil
  38   "Google Weather."
  39   :group 'comm)
  40
  41 (defcustom google-weather-use-https t
  42   "Default protocol to use to access the Google Weather API."
  43   :group 'google-weather)
  44
  45 (defconst google-weather-url
  46   "www.google.com/ig/api"
  47   "URL of the Google Weather API.")
  48
  49 (defcustom google-weather-unit-system-temperature-assoc
  50   '(("SI" . "℃")
  51     ("US" . "℉"))
  52   "Find temperature symbol from unit system."
  53   :group 'google-weather)
  54
  55 (defun google-weather-cache-expired (url expire-time)
  56   "Check if URL is cached for more than EXPIRE-TIME."
  57   (cond (url-standalone-mode
  58          (not (file-exists-p (url-cache-create-filename url))))
  59         (t (let ((cache-time (url-is-cached url)))
  60              (if cache-time
  61                  (time-less-p
  62                   (time-add
  63                    cache-time
  64                    (seconds-to-time expire-time))
  65                   (current-time))
  66                t)))))
  67
  68 (defun google-weather-cache-fetch (url)
  69   "Fetch URL from the cache."
  70   (with-current-buffer (generate-new-buffer " *temp*")
  71     (url-cache-extract (url-cache-create-filename url))
  72     (current-buffer)))
  73
  74 (defun google-weather-retrieve-data-raw (url &optional expire-time)
  75   "Retrieve URL and return its data as string.
  76 If EXPIRE-TIME is set, the data will be fetched from the cache if
  77 their are not older than EXPIRE-TIME seconds. Otherwise, they
  78 will be fetched and then cached. Therefore, setting EXPIRE-TIME
  79 to 0 force a cache renewal."
  80   (let* ((expired (if expire-time
  81                       (google-weather-cache-expired url expire-time)
  82                     t))
  83          (buffer (if expired
  84                      (url-retrieve-synchronously url)
  85                    (google-weather-cache-fetch url)))
  86          data)
  87     (when (and expired expire-time)
  88       (url-store-in-cache buffer))
  89     buffer))
  90
  91 (defun google-weather-retrieve-data (url &optional expire-time)
  92   "Retrieve URL and return its data as string.
  93 If EXPIRE-TIME is set, the data will be fetched from the cache if
  94 their are not older than EXPIRE-TIME seconds. Otherwise, they
  95 will be fetched and then cached. Therefore, setting EXPIRE-TIME
  96 to 0 force a cache renewal."
  97     (with-current-buffer (google-weather-retrieve-data-raw
  98                           url expire-time)
  99       (goto-char (point-min))
 100       (unless (search-forward "\n\n" nil t)
 101         (error "Data not found"))
 102       (decode-coding-region
 103        (point) (point-max)
 104        (detect-coding-region (point) (point-max) t))
 105       (set-buffer-multibyte t)
 106       (setq data (xml-parse-region (point) (point-max)))
 107       (kill-buffer (current-buffer))
 108       data)))
 109
 110 (defun google-weather-build-url (location &optional language)
 111   "Build URL to retrieve weather for LOCATION in LANGUAGE."
 112   (concat "http" (when google-weather-use-https "s") "://" google-weather-url "?weather=" (url-hexify-string location)
 113           (when language
 114             (concat "&hl=" language))))
 115
 116 (defun google-weather-get-data (location &optional language expire-time)
 117   "Get weather data for LOCATION in LANGUAGE.
 118 See `google-weather-retrieve-data' for the use of EXPIRE-TIME."
 119   (google-weather-retrieve-data
 120    (google-weather-build-url location language) expire-time))
 121
 122 (defun google-weather-data->weather (data)
 123   "Return all weather information from DATA."
 124   (cddr (assoc 'weather (cdr (assoc 'xml_api_reply data)))))
 125
 126 (defun google-weather-data->forecast-information (data)
 127   "Return the forecast information of DATA."
 128   (cddr (assoc 'forecast_information (google-weather-data->weather data))))
 129
 130 (defun google-weather-assoc (key data)
 131   "Extract value of field KEY from DATA."
 132   (cdr (assoc 'data (cadr (assoc key data)))))
 133
 134 (defun google-weather-data->city (data)
 135   "Return the city where the DATA come from."
 136   (google-weather-assoc
 137    'city
 138    (google-weather-data->forecast-information data)))
 139
 140 (defun google-weather-data->postal-code (data)
 141   "Return the postal code where the DATA come from."
 142   (google-weather-assoc
 143    'postal_code
 144    (google-weather-data->forecast-information data)))
 145
 146 (defun google-weather-data->unit-system (data)
 147   "Return the unit system used for DATA."
 148   (google-weather-assoc
 149    'unit_system
 150    (google-weather-data->forecast-information data)))
 151
 152 (defun google-weather-data->forecast-date (data)
 153   "Return the unit system used for DATA."
 154   (google-weather-assoc
 155    'forecast_date
 156    (google-weather-data->forecast-information data)))
 157
 158 (defun google-weather-data->forecast (data)
 159   "Get forecast list from DATA."
 160   ;; Compute date of the forecast in the same format as `current-time'
 161   (let ((date (apply 'encode-time
 162                      (parse-time-string
 163                       (concat (google-weather-data->forecast-date data) " 00:00:00")))))
 164     (mapcar
 165      (lambda (forecast)
 166        (let* ((forecast-date (decode-time date))
 167               (forecast-encoded-date (list (nth 4 forecast-date)
 168                                            (nth 3 forecast-date)
 169                                            (nth 5 forecast-date))))
 170          ;; Add one day to `date'
 171          (setq date (time-add date (days-to-time 1)))
 172          `(,forecast-encoded-date
 173            (low ,(google-weather-assoc 'low forecast))
 174            (high ,(google-weather-assoc 'high forecast))
 175            (icon ,(google-weather-assoc 'icon forecast))
 176            (condition ,(google-weather-assoc 'condition forecast)))))
 177      (loop for entry in (google-weather-data->weather data)
 178            when (eq (car entry) 'forecast_conditions)
 179            collect entry))))
 180
 181 (defun google-weather-data->forecast-for-date (data date)
 182   "Return forecast for DATE from DATA.
 183 DATE should be in the same format used by calendar,
 184 i.e. (MONTH DAY YEAR)."
 185   (cdr (assoc date (google-weather-data->forecast data))))
 186
 187 (defun google-weather-data->temperature-symbol (data)
 188   "Return the temperature to be used according in DATA.
 189 It uses `google-weather-unit-system-temperature-assoc' to find a
 190 match."
 191   (cdr (assoc (google-weather-data->unit-system data) google-weather-unit-system-temperature-assoc)))
 192
 193
 194 (defun google-weather-data->problem-cause (data)
 195   "Return a string if DATA contains a problem cause, `nil' otherwise.
 196
 197 An error message example:
 198
 199 ((xml_api_reply
 200   ((version . \"1\"))
 201   (weather
 202    ((module_id . \"0\") (tab_id . \"0\") (mobile_row . \"0\")
 203     (mobile_zipped . \"1\") (row . \"0\") (section . \"0\"))
 204    (problem_cause ((data . \"Information is temporarily unavailable.\"))))))))"
 205   (google-weather-assoc
 206    'problem_cause
 207    (google-weather-data->weather data)))
 208
 209 (provide 'google-weather)