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 nil
  42   "Default protocol to use to access the Google Weather API."
  43   :group 'google-weather
  44   :type 'boolean)
  45
  46 (defconst google-weather-url
  47   "www.google.com/ig/api"
  48   "URL of the Google Weather API.")
  49
  50 (defconst google-weather-image-url
  51   "http://www.google.com"
  52   "URL prefix for images.")
  53
  54 (defcustom google-weather-unit-system-temperature-assoc
  55   '(("SI" . "℃")
  56     ("US" . "℉"))
  57   "Find temperature symbol from unit system."
  58   :group 'google-weather)
  59
  60 (defun google-weather-cache-expired (url expire-time)
  61   "Check if URL is cached for more than EXPIRE-TIME."
  62   (cond (url-standalone-mode
  63          (not (file-exists-p (url-cache-create-filename url))))
  64         (t (let ((cache-time (url-is-cached url)))
  65              (if cache-time
  66                  (time-less-p
  67                   (time-add
  68                    cache-time
  69                    (seconds-to-time expire-time))
  70                   (current-time))
  71                t)))))
  72
  73 (defun google-weather-cache-fetch (url)
  74   "Fetch URL from the cache."
  75   (with-current-buffer (generate-new-buffer " *temp*")
  76     (url-cache-extract (url-cache-create-filename url))
  77     (current-buffer)))
  78
  79 (defun google-weather-retrieve-data-raw (url &optional expire-time)
  80   "Retrieve URL and return its data as string.
  81 If EXPIRE-TIME is set, the data will be fetched from the cache if
  82 their are not older than EXPIRE-TIME seconds. Otherwise, they
  83 will be fetched and then cached. Therefore, setting EXPIRE-TIME
  84 to 0 force a cache renewal."
  85   (let* ((expired (if expire-time
  86                       (google-weather-cache-expired url expire-time)
  87                     t))
  88          (buffer (if expired
  89                      (url-retrieve-synchronously url)
  90                    (google-weather-cache-fetch url)))
  91          data)
  92     (when (and expired expire-time)
  93       (url-store-in-cache buffer))
  94     buffer))
  95
  96 (defun google-weather-retrieve-data (url &optional expire-time)
  97   "Retrieve URL and return its data as string.
  98 If EXPIRE-TIME is set, the data will be fetched from the cache if
  99 their are not older than EXPIRE-TIME seconds. Otherwise, they
 100 will be fetched and then cached. Therefore, setting EXPIRE-TIME
 101 to 0 force a cache renewal."
 102     (with-current-buffer (google-weather-retrieve-data-raw
 103                           url expire-time)
 104       (goto-char (point-min))
 105       (unless (search-forward "\n\n" nil t)
 106         (error "Data not found"))
 107       (decode-coding-region
 108        (point) (point-max)
 109        (detect-coding-region (point) (point-max) t))
 110       (set-buffer-multibyte t)
 111       (let ((data (xml-parse-region (point) (point-max))))
 112         (kill-buffer (current-buffer))
 113         data)))
 114
 115 (defun google-weather-build-url (location &optional language)
 116   "Build URL to retrieve weather for LOCATION in LANGUAGE."
 117   (concat "http" (when google-weather-use-https "s") "://" google-weather-url "?weather=" (url-hexify-string location)
 118           (when language
 119             (concat "&hl=" language))))
 120
 121 (defun google-weather-get-data (location &optional language expire-time)
 122   "Get weather data for LOCATION in LANGUAGE.
 123 See `google-weather-retrieve-data' for the use of EXPIRE-TIME."
 124   (google-weather-retrieve-data
 125    (google-weather-build-url location language) expire-time))
 126
 127 (defun google-weather-data->weather (data)
 128   "Return all weather information from DATA."
 129   (cddr (assoc 'weather (cdr (assoc 'xml_api_reply data)))))
 130
 131 (defun google-weather-data->forecast-information (data)
 132   "Return the forecast information of DATA."
 133   (cddr (assoc 'forecast_information (google-weather-data->weather data))))
 134
 135 (defun google-weather-assoc (key data)
 136   "Extract value of field KEY from DATA."
 137   (cdr (assoc 'data (cadr (assoc key data)))))
 138
 139 (defun google-weather-data->city (data)
 140   "Return the city where the DATA come from."
 141   (google-weather-assoc
 142    'city
 143    (google-weather-data->forecast-information data)))
 144
 145 (defun google-weather-data->postal-code (data)
 146   "Return the postal code where the DATA come from."
 147   (google-weather-assoc
 148    'postal_code
 149    (google-weather-data->forecast-information data)))
 150
 151 (defun google-weather-data->unit-system (data)
 152   "Return the unit system used for DATA."
 153   (google-weather-assoc
 154    'unit_system
 155    (google-weather-data->forecast-information data)))
 156
 157 (defun google-weather-data->forecast-date (data)
 158   "Return the unit system used for DATA."
 159   (google-weather-assoc
 160    'forecast_date
 161    (google-weather-data->forecast-information data)))
 162
 163 (defun google-weather-data->forecast (data)
 164   "Get forecast list from DATA."
 165   ;; Compute date of the forecast in the same format as `current-time'
 166   (let ((date (apply 'encode-time
 167                      (parse-time-string
 168                       (concat (google-weather-data->forecast-date data) " 00:00:00")))))
 169     (mapcar
 170      (lambda (forecast)
 171        (let* ((forecast-date (decode-time date))
 172               (forecast-encoded-date (list (nth 4 forecast-date)
 173                                            (nth 3 forecast-date)
 174                                            (nth 5 forecast-date))))
 175          ;; Add one day to `date'
 176          (setq date (time-add date (days-to-time 1)))
 177          `(,forecast-encoded-date
 178            (low ,(google-weather-assoc 'low forecast))
 179            (high ,(google-weather-assoc 'high forecast))
 180            (icon ,(concat google-weather-image-url
 181                           (google-weather-assoc 'icon forecast)))
 182            (condition ,(google-weather-assoc 'condition forecast)))))
 183      (loop for entry in (google-weather-data->weather data)
 184            when (eq (car entry) 'forecast_conditions)
 185            collect entry))))
 186
 187 (defun google-weather-data->forecast-for-date (data date)
 188   "Return forecast for DATE from DATA.
 189 DATE should be in the same format used by calendar,
 190 i.e. (MONTH DAY YEAR)."
 191   (cdr (assoc date (google-weather-data->forecast data))))
 192
 193 (defun google-weather-data->temperature-symbol (data)
 194   "Return the temperature to be used according in DATA.
 195 It uses `google-weather-unit-system-temperature-assoc' to find a
 196 match."
 197   (cdr (assoc (google-weather-data->unit-system data) google-weather-unit-system-temperature-assoc)))
 198
 199
 200 (defun google-weather-data->problem-cause (data)
 201   "Return a string if DATA contains a problem cause, `nil' otherwise.
 202
 203 An error message example:
 204
 205 ((xml_api_reply
 206   ((version . \"1\"))
 207   (weather
 208    ((module_id . \"0\") (tab_id . \"0\") (mobile_row . \"0\")
 209     (mobile_zipped . \"1\") (row . \"0\") (section . \"0\"))
 210    (problem_cause ((data . \"Information is temporarily unavailable.\"))))))))"
 211   (google-weather-assoc
 212    'problem_cause
 213    (google-weather-data->weather data)))
 214
 215 (provide 'google-weather)