module PM25

# File lib/pm_25.rb, line 59
def access_api(interface, params={})
  params[:token] ||= get_token
  res = RestClient.get(API_base + interface, {params: params})
  if res.code == 200
    JSON.parse res.body
  else
    res.code
  end
end

# File lib/pm_25.rb, line 157
def all_cities(token=nil)
  access_api('all_cities.json', token: token)
end

# File lib/pm_25.rb, line 166
def aqi_ranking(token=nil)
  access_api('aqi_ranking.json', token: token)
end

# File lib/pm_25.rb, line 143
def available_cities(token=get_token)
  res = RestClient.get 'http://www.pm25.in/api/querys.json', {params: {token: token}}
  if res.code == 200
    JSON.parse(res.body)['cities']
  else
    res.code
  end
end

# File lib/pm_25.rb, line 174
def bing_pm25(city)
  city = URI.encode(city)
  bing_url = "http://cn.bing.com/search?q=#{city}+pm2.5"
  html = Nokogiri.parse(open(bing_url).read)
  html.at('#msn_pm25rt .b_xlText').content.to_i
end

# File lib/pm_25.rb, line 22
def get_config(constant_name, default_value=nil)
  if ENV[constant_name]
    ENV[constant_name]
  elsif File.exist?('config.json')
    open('config.json') do |f|
      JSON.parse(f.read)[constant_name]
    end
  else
    default_value
  end
end

# File lib/pm_25.rb, line 50
def get_default_city
  get_config('PM25_IN_CITY')
end

# File lib/pm_25.rb, line 41
def get_token
  test_token= '5j1znBVAsnSf5xQyNQyq'
  get_config('PM25_IN_TOKEN', test_token)
end

# File lib/pm_25.rb, line 187
def just_pm25(city=get_default_city, token=nil)
  result = pm25(city, token)
  # error on pm25.in api
  if result.is_a? Fixnum
    bing_pm25(city)
  elsif result.include? 'error'
    bing_pm25(city)
  else
    publish_time = Time.parse(result[-1]['time_point'])
    # Data on pm25.in is too old.
    # According to GB 3095-2013, PM 2.5 should have hourly
    # average values for at least 20 hours a day.
    # http://hbj.shanghang.gov.cn/hjjc/gldt/201411/P020141110361645902554.pdf
    if Time.now - publish_time > 2.hours
      bing_pm25(city)
    else
      result[-1]['pm2_5']
    end
  end
end

# File lib/pm_25.rb, line 134
def pm25(city=get_default_city, token=nil)
  access_api('pm2_5.json', city: city, token: token)
end

# File lib/pm_25.rb, line 212
def pm25_level(pm25)
  if pm25 <= 12
    aqi_category = 'Good'
    aqi_meaning = 'Air quality is considered satisfactory, and air pollution poses little or no risk.'
    aqi_action = 'None'
  elsif pm25 <= 35.4
    aqi_category = 'Moderate'
    aqi_meaning = 'Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.'
    aqi_action = 'Unusually sensitive people should consider reducing prolonged or heavy exertion.'
  elsif pm25 <= 55.4
    aqi_category = 'Unhealthy for sensitive Groups'
    aqi_meaning = 'Members of sensitive groups may experience health effects. The general public is not likely to be affected.'
    aqi_action = 'People with heart or lung disease, children and older adults should reduc e prolonged or heavy exertion'
  elsif pm25 <= 150.4
    aqi_category = 'Unhealthy'
    aqi_meaning = 'Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.'
    aqi_action = 'People with heart or lung disease, children and older adults should avoid prolonged or heavy exertion. Everyone else should reduce prolonged or heavy exertion.'
  elsif pm25 <= 250.4
    aqi_category = 'Very Unhealthy'
    aqi_meaning = 'Health warnings of emergency conditions. The entire population is more likely to be affected.'
    aqi_action = 'People with heart or lung disease, children and older adults should avoid all physical activity outdoors. Everyone else should avoid prolonged or heavy exertion.'
  else
    aqi_category = 'Hazardous'
    aqi_meaning = 'Health alert: everyone may experience more serious health effects'
    aqi_action = 'Avoid all physical activity outdoors.'
  end
{pm25: pm25,
 category: aqi_category,
 meaning: aqi_meaning,
 action: aqi_action}
end