Refactoring

app/models/entsoe.rb

@@ -7,29 +7,82 @@ require 'open-uri'
 require 'nokogiri'
 
 class Entsoe 
-  
-  URL = 'https://transparency.entsoe.eu'
 
-  def initialize(api_key)
+  URL = 'https://transparency.entsoe.eu'
+  
+  attr_reader :storage_cost
+
+  def initialize(api_key = "c2287e07-0c26-4950-b430-22b7f75a8f2e")
     @api_key = api_key
+    @kwh_prices = {}  
+    @storage_cost = 0.05 # how much does it cost to store 1 kwh in battery
   end
   
-  def day_ahead_prices(date)
+  def price_at(formatted_hour)
+    unless @kwh_prices.key?(formatted_hour)
+      @kwh_prices.merge!(query_day_ahead_prices(Date.parse(formatted_hour)))
+    end
+    @kwh_prices[formatted_hour]
+  end
+  
+  def prices_at(date)
+    hour_start = date.beginning_of_day
+    day_end = hour_start.advance(days: 1)
+    result = {}
+    while(hour_start < day_end) do
+        formatted_hour = hour_start.strftime("%F-%H")
+        result.merge!({ formatted_hour => price_at(formatted_hour)})
+        hour_start = hour_start.advance(:hours => 1)
+    end
+    result    
+  end
+  
+  def high_low_hours(date)
+    sorted_prices = prices_at(date).to_a.sort_by(&:last) # sort according to price 
+    lowest_hour = sorted_prices.first[0]
+    highest_hour = sorted_prices.last[0] 
+    # calculate hours where rate > charge_rate + storage_cost (typically 0.05)
+    charge_rate = sorted_prices.first[1] # assume we charge at lowest hour
+    high_hours = sorted_prices.select{|p| p[1] > charge_rate + storage_cost}.to_h.keys
+    
+    return lowest_hour,highest_hour,high_hours
+  end
+  
+  def query_day_ahead_prices(date)
     start_date = date.beginning_of_day
     end_date = date.end_of_day
     
     # A44 - Document type => Price Document
-    # A01 - Process type => Day Ahead
     # NL =  '10YNL----------L'
     
     domain = '10YNL----------L'      
-    url = URL + "/api?securityToken=%s&documentType=A44&processType=A01&in_Domain=%s&out_Domain=%s&periodStart=%s&periodEnd=%s" % [@api_key, domain, domain, start_date.iso8601, end_date.iso8601]
-    p url
+    url = URL + "/api?securityToken=%s&documentType=A44&in_Domain=%s&out_Domain=%s&periodStart=%s&periodEnd=%s" % [@api_key, domain, domain, start_date.strftime("%Y%m%d%H%M"), end_date.strftime("%Y%m%d%H00")]
+    #p url
+    
+    base_request(date, url)
   end
   
   private
   
-    def base_request(url)
+    # get position and amount from XML snippet
+    # <Point>
+    #  <position>1</position>
+    #  <price.amount>196.23</price.amount>
+    # </Point>
+    #
+    # convert price to EUR per kwh, including VAT (21%)
+    #
+    def parse_point(xml)
+      return xml.children[1].text.to_i, ((xml.children[3].text.to_f/1000)*1.21).round(5)
+    end
+  
+    def base_request(date, url)
+      formatted_date = date.strftime("%F")
+      
       doc = Nokogiri::XML(URI.open(url))
-    end 
+      prices = doc.xpath('.//xmlns:Point').map{|p| parse_point(p)}
+      
+      #returns a hash with keys formatted "yyyy-mm-dd-hr" and values price (per kwh)
+      prices.map{|p| ["%s-%02d" % [formatted_date,(p[0]-1)], p[1]]}.to_h
+    end
 end