From: Ross Bamford <rossrt@...>
Date: 2006-02-27T00:14:58+09:00
Subject: Re: [SOLUTION] Current Temperature (#68)

I wanted to allow UK postcodes, and I've had some mad insomnia the past
couple of nights. This is some of the nastiest code I've written in a
long time, which is pretty liberating if I'm honest... 

====[CUT HERE]====
#!/usr/local/bin/ruby
# Run a query for temperature based on place name or UK Postcode.
#
# Uses the BBC weather service (data from the MET office).
# See: http://www.bbc.co.uk/weather/
#
require 'net/http'
require 'uri'

unless $0 == __FILE__
  raise LoadError, "You don't wanna require this..."
end

if ARGV.detect { |e| e =~ /--?h(elp)?/ }
  puts <<-EOM
  
  Syntax: ruby weather.rb [-h] [-f] [-x] [-a[select-ids]] search query

  Options:

    -h      Show this help text.
    -f      Display temperatures in degrees Farenheit (default: Celsius)
    -x      Show eXtended report.
    -a[ids] Automatically select [ids] where a search returns multiple
            results. Avoids user input at runtime. Examples:

              -a      - Show temperature for all results
              -a1     - Show the first result
              -a'1 3' - Show results 1 and 3

  Search Query:

    The search query is constructed from all non-option arguments, and 
    may be one of:

      * UK postcode (partial or full)
      * UK town
      * UK or International city
      * Country

  Examples:

    ruby weather.rb -f ilkeston       - Temp in farenheit for Ilkeston, UK
    ruby weather.rb -a76 italy        - Celsius temp in Rome, Italy
    ruby weather.rb -a3 de7           - Celsius in Derby, UK 
    ruby weather.rb london            - Temp in interactively-selected result
                                        for query 'london'
    ruby weather.rb -f -x -a new york - Extended report in Farenheit for all 
                                        'new york' results
  
  EOM
  exit(1)
end

RESULT_TITLE = /5 Day Forecast in (\w+) for ([^<]+)<\/title>/
MULTI_RESULT_TITLE = /Weather Centre - Search Results<\/title>/
NO_LOCS = /No locations were found for "([^"]*)"/
FIVEDAY = /5day.shtml/

# Extract result from multiple result page
EX_RESULT = /<a href="\/weather\/5day(?:_f)?.shtml\?([^"]*)" class="seasonlink"><strong>([^<]*)(?:<\/strong>)?<\/a>/

# Extract from 5day result page
EX_OVERVIEW = /">(\w+)<\/span>\s*\d+<abbr title="Temperature/
EX_TEMP = /(\d+)\s*\<abbr title="Temperature in degrees[^"]*"\>/
EX_WIND = /<br \/>(\w+) \((\d+) <abbr title="Miles per/
EX_HUMIDITY = /title="Relative humid[^:]*: (\d+)/
EX_PRESSURE = /title="Pressure in[^:]*: ([^<]+)/
EX_VISIBILITY = /Visibility<\/strong>: ([^<]+)/

# validate input
SELECT_INPUT = /^([Aa]|\d+(\s*\d+)*)$/

FARENHEIT = if ARGV.include? '-f'           
              ARGV.reject! { |e| e == '-f' }
              true
            end
AUTOSELECT = if ARGV.detect(&asp = lambda { |e| e =~ /-a([Aa]|\d+(?:\s*\d+)*)?/ })
               a = $1 || 'A'
               ARGV.reject!(&asp)
               a
             end  
EXTMODE = if ARGV.include? '-x'
            ARGV.reject! { |e| e == '-x' }
            true
          end

# Fetch and process a single URI (either search, results or 5day) 
def fetch_process(uri)
  case r = fetch(uri)
  when Net::HTTPSuccess
    process_result(r.body)
  else
    r.error!
  end
end

# Actually fetches data from the web. All results ultimately come from
# 5day pages (new_search.pl redirects us there). We handle redirects
# here and also do URL rewriting to support Farenheit mode.
def fetch(uri_str, limit = 10)
  raise ArgumentError, 'HTTP redirect too deep' if limit == 0

  if FARENHEIT and uri_str =~ FIVEDAY
    uri_str = uri_str.dup
    uri_str[FIVEDAY] = '5day_f.shtml'
  end
  
  response = Net::HTTP.get_response(URI.parse(uri_str))
  case response
  when Net::HTTPSuccess     then response
  when Net::HTTPRedirection then fetch(response['location'], limit - 1)
  else
    response.error!
  end
end

# Collects multiple results from a "Search Results" page into an
# array of arrays e.g [["Some Place", "id=3309"], ["Etc", "id=2002"]]
def collect_results(body)
  a = []
  body.scan(EX_RESULT) { |s| a << [$2, $1] }
  a
end

# The main result processing function. This handles all responses.
# If it's given a single result (a 5day page) it extracts and outputs
# the current temp. If it's a multi result page, the results are 
# extracted and the user selects from them, with the resulting URL
# (a 5day) then passed to fetch_process to handle the fetch and pass
# the result back here.
def process_result(body)
  if body =~ RESULT_TITLE
    # this is a result
    units, place = $1, $2
    if body =~ EX_TEMP
      temp = $1
      out = if EXTMODE
        overview = ((m = EX_OVERVIEW.match(body)) ? m[1] : '?')
        wind_dir, wind_speed = ((m = EX_WIND.match(body)) ? m[1,2] : ['?','?'])
        humidity = ((m = EX_HUMIDITY.match(body)) ? m[1] : '?')
        pressure = ((m = EX_PRESSURE.match(body)) ? m[1] : '?')
        visibility = ((m = EX_VISIBILITY.match(body)) ? m[1] : '?')

        "\n#{place}\n" +
        "  Temp         : #{temp} degrees #{units}\n" +
        "  Wind         : #{wind_dir} (#{wind_speed} mph)\n" +
        "  Humidity (%) : #{humidity}\n" +
        "  Pressure (mB): #{pressure.chop}\n" +
        "  Visibility   : #{visibility}"
      else
        "#{place} - #{temp} degrees #{units}"
      end
      
      puts out
    else
      puts "No data for #{place}"
    end
  elsif body =~ MULTI_RESULT_TITLE 
    # multiple or no result
    if body =~ NO_LOCS 
      puts "No locations matched '#{$1}'"
    else
      a = collect_results(body)      
      
      if a.length > 0
        unless n = AUTOSELECT
          puts "Multiple results:\n"
          puts "  [0]\tCancel"
          a.each_with_index do |e,i|
            puts "  [#{i+1}]\t#{e.first}"
          end

          puts "  [A]\tAll\n\n"

          begin
            print "Select (separate with spaces): "
            n = STDIN.gets.chomp 
          end until n =~ SELECT_INPUT 
        end
        
        if n != '0'  # 0 is cancel
          n.split(' ').inject([]) do |ary,i|
            if i.upcase == 'A'
              ary + a.map { |e| e.last }
            else
              ary << a[i.to_i - 1].last
            end
          end.each do |id|
            fetch_process("http://www.bbc.co.uk/weather/5day.shtml?#{id}")
          end
        end
      else
        puts "No usable results found"
      end
    end
  else
    puts "Unknown location"
  end
end

def display_temp(q)
  fetch_process("http://www.bbc.co.uk/cgi-perl/weather/search/new_search.pl?search_query=#{q}")
end

display_temp(URI.encode(ARGV.empty? ? 'ilkeston' : ARGV.join(' ')))


-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk