Adds timezone to Entsoe prices

app/models/entsoe.rb

@@ -10,30 +10,32 @@ class Entsoe
 
   URL = 'https://transparency.entsoe.eu'
   
-  attr_accessor :no_grid_charge_months
+  attr_accessor :no_grid_charge_months, :zone
   attr_reader :storage_cost
 
-  def initialize(storage_cost = 0.05, api_key = "c2287e07-0c26-4950-b430-22b7f75a8f2e")
+  def initialize(zone = "Amsterdam", storage_cost = 0.05, api_key = "c2287e07-0c26-4950-b430-22b7f75a8f2e")
     @api_key = api_key
     @kwh_prices = {}  
     @storage_cost = storage_cost # how much does it cost to store 1 kwh in battery
     @no_grid_charge_months = [5,6,7] # months where we assume there is enough surplus from sun power
+    @zone = zone
   end
   
   def price_at(formatted_hour)
     unless @kwh_prices.key?(formatted_hour)
       p "Fetching Entsoe tariffs for %s" % formatted_hour
-      @kwh_prices.merge!(query_day_ahead_prices(Date.parse(formatted_hour)))
+      prices = query_day_ahead_prices(Date.parse(formatted_hour))
+      @kwh_prices.merge!(hourly_format(prices))
     end
     @kwh_prices[formatted_hour]
   end
   
   def prices_at(date)
-    hour_start = date.beginning_of_day
+    hour_start = date.beginning_of_day.in_time_zone(@zone)
     day_end = hour_start.advance(days: 1)
     result = {}
     while(hour_start < day_end) do
-        formatted_hour = hour_start.strftime("%F-%H")
+        formatted_hour = hour_start.strftime("%F %H")
         result.merge!({ formatted_hour => price_at(formatted_hour)})
         hour_start = hour_start.advance(:hours => 1)
     end
@@ -79,6 +81,11 @@ class Entsoe
   
   private
   
+    def hourly_format(prices)
+      # in memory hash @kwh_prices is in @zone timezone
+      prices.to_a.map{|p| [p[0].in_time_zone(@zone).strftime("%F %H"),p[1]]}.to_h
+    end
+  
     # get position and amount from XML snippet
     # <Point>
     #  <position>1</position>
@@ -88,16 +95,20 @@ class Entsoe
     # 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)
+      return xml.xpath(".//xmlns:position").text.to_i, ((xml.xpath(".//xmlns:price.amount").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))
-      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 = doc.xpath('.//xmlns:Point').map{|p| parse_point(p)}
-      prices.map{|p| ["%s-%02d" % [formatted_date,(p[0]-1)], p[1]]}.to_h
+      # get start_time (in UTC) from XML docment
+      start_time = DateTime.parse(doc.xpath('.//xmlns:period.timeInterval//xmlns:start').text)
+      
+      #returns a hash with keys formatted "yyyy-mm-dd hr" and values price (per kwh)
+      # <position> tag runs from 1-24. We need hours from 00-23, therefore substracting 1
+      prices.map{|p| [start_time.advance(hours: (p[0]-1)), p[1]]}.to_h
     end
 end

db/migrate/003_creates_prices.rb

@@ -0,0 +1,10 @@
+class CreatesPrices << ActiveRecord::Migration[4.2]
+  def change
+    create_table :prices do |t|
+      t.datetime :hour
+      t.float :usage_kwh
+      t.timestamps
+    end  
+    
+    add_index :prices, :hour 
+end