Merge pull request #71 from dxw/72-and-73-cache-forecasts-w-cerc-fore…

…cast-service

72 and 73 cache forecasts using CercForecastService

.env.example

@@ -21,3 +21,4 @@ ADDITIONAL_HOSTNAMES=
 
 CERC_API_HOST_URL=https://cerc.example.com
 CERC_API_KEY=SECRET-API-KEY
+CERC_API_CACHE_LIMIT_MINS=30

Gemfile

@@ -24,6 +24,7 @@ gem "terser"
 gem "govuk-components"
 gem "httparty"
 gem "view_component"
+gem "seed-fu"
 
 group :development do
   gem "better_errors"

Gemfile.lock

@@ -360,6 +360,9 @@ GEM
       sprockets-rails
       tilt
     securerandom (0.3.1)
+    seed-fu (2.3.9)
+      activerecord (>= 3.1)
+      activesupport (>= 3.1)
     selenium-webdriver (4.25.0)
       base64 (~> 0.2)
       logger (~> 1.4)
@@ -494,6 +497,7 @@ DEPENDENCIES
   rollbar
   rspec-rails
   sass-rails (~> 6.0)
+  seed-fu
   selenium-webdriver
   simplecov
   solargraph

Procfile

@@ -0,0 +1,2 @@
+web: bundle exec puma -C config/puma.rb
+release: rake db:migrate && rake db:seed_fu

README.md

@@ -90,6 +90,7 @@ To manage sensitive environment variables:
 
 - `CERC_API_HOST_URL`: find the URL of the CERC API host in the 1Password vault
 - `CERC_API_KEY`: find the API key in the 1Password vault
+- `CERC_API_CACHE_LIMIT_MINS`: how often we expire our cached forecasts
 
 ## Access
 

app/controllers/forecasts_controller.rb

@@ -1,8 +1,15 @@
 class ForecastsController < ApplicationController
   def show
-    @forecasts = CercApiClient
-      .forecasts_for(params.has_key?("zone") ? params["zone"] : "Southwark")
-    @zones = JSON.parse(File.read("#{Rails.root}/config/list-of-zones.json"))
+    @forecasts = CercForecastService.latest_forecasts_for(zone).data
+    @zones = Zone.order(name: :asc).pluck(:name, :cerc_id)
     @air_quality_alerts = @forecasts.map(&:alerts).flatten
   end
+
+  private
+
+  def zone
+    return Zone.default unless params[:zone]
+
+    Zone.find_by(cerc_id: params[:zone])
+  end
 end

app/controllers/styled_forecasts_controller.rb

@@ -1,13 +1,11 @@
 class StyledForecastsController < ApplicationController
   layout "tailwind_layout"
   def show
-    @forecasts = CercApiClient
-      .forecasts_for(params.fetch("zone", "Southwark"))
+    @forecasts = CercForecastService.latest_forecasts_for(zone).data
   end
 
   def update
-    forecasts = CercApiClient
-      .forecasts_for(params.fetch("zone", "Southwark"))
+    forecasts = CercForecastService.latest_forecasts_for(zone).data
 
     day_forecast = forecast_for_day(params.fetch("day"), forecasts)
 
@@ -18,6 +16,8 @@ def update
     )
   end
 
+  private
+
   def forecast_for_day(day, forecasts)
     case day
     when "today"
@@ -30,4 +30,10 @@ def forecast_for_day(day, forecasts)
       raise ArgumentError, "Invalid day: #{day}"
     end
   end
+
+  def zone
+    return Zone.default unless params[:zone]
+
+    Zone.find_by(cerc_id: params[:zone])
+  end
 end

app/lib/forecast_factory.rb

@@ -1,10 +1,14 @@
 class ForecastFactory
-  def self.build(forecast_representation)
-    obtained_at = Time.zone.parse(forecast_representation.fetch("forecastdate"))
+  def self.build(cerc_forecasts:, zone_id: nil)
+    obtained_at = Time.zone.parse(cerc_forecasts.fetch("forecastdate"))
 
-    zone = forecast_representation
-      .fetch("zones")
-      .first
+    zones = cerc_forecasts.fetch("zones")
+    zone = if zone_id
+      fail_if_not_found = proc { raise "Forecast for zone ID '#{zone_id}' not found" }
+      zones.find(fail_if_not_found) { |z| zone_id == z["zone_id"] }
+    else
+      zones.first
+    end
 
     zone.fetch("forecasts")
       .map do |forecast|

app/models/cached_forecast.rb

@@ -0,0 +1,27 @@
+class CachedForecast < ApplicationRecord
+  self.implicit_order_column = "obtained_at"
+  belongs_to :zone
+  serialize :data
+
+  scope :latest_for, ->(zone) { where("zone_id = ?", zone.id).last }
+
+  def self.stale?
+    if (latest_record = last)
+      threshold = Time.current - ENV.fetch("CERC_API_CACHE_LIMIT_MINS").to_i.minutes
+      return latest_record.obtained_at < threshold
+    end
+
+    true
+  end
+
+  def self.store(built_forecasts)
+    zone = Zone.find_by(cerc_id: built_forecasts.first.zone.id)
+    obtained_at = built_forecasts.first.obtained_at
+
+    create(
+      zone: zone,
+      obtained_at: obtained_at,
+      data: built_forecasts
+    )
+  end
+end

app/models/cerc_api_client.rb

@@ -17,6 +17,18 @@ def self.fetch_data(zone)
   end
 
   def self.forecasts_for(zone)
-    ForecastFactory.build(fetch_data(zone))
+    ForecastFactory.build(cerc_forecasts: fetch_data(zone))
+  end
+
+  def self.latest_forecasts
+    base_url = ENV.fetch("CERC_API_HOST_URL")
+
+    query = {
+      "from" => Date.today,
+      "numdays" => 3,
+      "key" => ENV.fetch("CERC_API_KEY")
+    }
+
+    HTTParty.get("#{base_url}/getforecast/all", query: query)
   end
 end

app/models/forecast.rb

@@ -29,7 +29,7 @@ def inspect
       "@zone=#{zone.inspect}",
       "@air_pollution=#{air_pollution.inspect}",
       "@uv=#{uv.inspect}",
-      "@pollen=#{pollen}",
+      "@pollen=#{pollen.inspect}",
       "@temperature=#{temperature.inspect}"
     ]
 

app/models/zone.rb

@@ -0,0 +1,7 @@
+class Zone < ApplicationRecord
+  DEFAULT_ZONE_SOUTHWARK_CERC_ID = 29
+
+  def self.default
+    find_by!(cerc_id: DEFAULT_ZONE_SOUTHWARK_CERC_ID)
+  end
+end

app/services/cerc_forecast_service.rb

@@ -0,0 +1,21 @@
+class CercForecastService
+  class << self
+    def latest_forecasts_for(zone)
+      refresh_cache if CachedForecast.stale?
+
+      CachedForecast.latest_for(zone)
+    end
+
+    def refresh_cache
+      cerc_forecasts = CercApiClient.latest_forecasts
+
+      cerc_forecasts.fetch("zones").each do |zone|
+        CachedForecast.store(
+          ForecastFactory.build(
+            cerc_forecasts: cerc_forecasts, zone_id: zone.fetch("zone_id")
+          )
+        )
+      end
+    end
+  end
+end

app/views/styled_forecasts/show.html.erb

@@ -1,5 +1,5 @@
 <%= render partial: "styled_forecasts/location" %>
-<%= render partial: "styled_forecasts/forecast_tabs", forecasts: @forecasts %>
+<%= render partial: "styled_forecasts/forecast_tabs", cerc_forecasts: @forecasts %>
 <%= render partial: "styled_forecasts/predictions", locals: { forecast: @forecasts.first } %>
 <%= render partial: "sharing" %>
 <%= render partial: "learning" %>

config/application.rb

@@ -12,6 +12,7 @@
 module AirText
   class Application < Rails::Application
     config.generators do |g|
+      g.orm :active_record, primary_key_type: :uuid
       g.test_framework :rspec,
         fixtures: true,
         view_specs: false,
@@ -36,5 +37,20 @@ class Application < Rails::Application
     # Make sure the `form_with` helper generates local forms, instead of defaulting
     # to remote and unobtrusive XHR forms
     config.action_view.form_with_generates_remote_forms = false
+
+    config.after_initialize do
+      ActiveRecord.yaml_column_permitted_classes += [
+        ActiveSupport::TimeWithZone,
+        ActiveSupport::TimeZone,
+        Time,
+        Date,
+        Forecast,
+        ForecastZone,
+        AirPollutionPrediction,
+        UvPrediction,
+        PollenPrediction,
+        TemperaturePrediction
+      ]
+    end
   end
 end