Move duplicate functionality into `source.ex`

apps/explorer/lib/explorer/exchange_rates/source.ex

@@ -9,4 +9,18 @@ defmodule Explorer.ExchangeRates.Source do
   Callback for fetching an exchange rates for currencies/tokens.
   """
   @callback fetch_exchange_rates :: {:ok, [Token.t()]} | {:error, any}
+
+  def headers do
+    [{"Content-Type", "application/json"}]
+  end
+
+  def decode_json(data) do
+    Jason.decode!(data)
+  end
+
+  def to_decimal(nil), do: nil
+
+  def to_decimal(value) do
+    Decimal.new(value)
+  end
 end

apps/explorer/lib/explorer/exchange_rates/source/coin_gecko.ex

@@ -6,13 +6,14 @@ defmodule Explorer.ExchangeRates.Source.CoinGecko do
   alias Explorer.ExchangeRates.{Source, Token}
   alias HTTPoison.{Error, Response}
 
+  import Source, only: [decode_json: 1, to_decimal: 1, headers: 0]
+
   @behaviour Source
+  @headers
 
   @impl Source
   def fetch_exchange_rates do
-    headers = [{"Content-Type", "application/json"}]
-
-    case HTTPoison.get(source_url(), headers) do
+    case HTTPoison.get(source_url(), headers()) do
       {:ok, %Response{body: body, status_code: 200}} ->
         {:ok, format_data(body)}
 
@@ -57,25 +58,14 @@ defmodule Explorer.ExchangeRates.Source.CoinGecko do
     configured_url || "https://api.coingecko.com/api/v3"
   end
 
-  defp decode_json(data) do
-    Jason.decode!(data)
-  end
-
-  defp to_decimal(nil), do: nil
-
-  defp to_decimal(value) do
-    Decimal.new(value)
-  end
-
   defp source_url(currency \\ "usd") do
     "#{base_url()}/coins/markets?vs_currency=#{currency}"
   end
 
   defp get_btc_price(currency \\ "usd") do
-    headers = [{"Content-Type", "application/json"}]
     url = "#{base_url()}/exchange_rates"
 
-    case HTTPoison.get(url, headers) do
+    case HTTPoison.get(url, headers()) do
       {:ok, %Response{body: body, status_code: 200}} ->
         data = decode_json(body)
         current_price = data["rates"][currency]["value"]

apps/explorer/lib/explorer/exchange_rates/source/coin_market_cap.ex

@@ -6,13 +6,13 @@ defmodule Explorer.ExchangeRates.Source.CoinMarketCap do
   alias Explorer.ExchangeRates.{Source, Token}
   alias HTTPoison.{Error, Response}
 
+  import Source, only: [decode_json: 1, to_decimal: 1, headers: 0]
+
   @behaviour Source
 
   @impl Source
   def fetch_exchange_rates do
-    headers = [{"Content-Type", "application/json"}]
-
-    case HTTPoison.get(source_url(), headers) do
+    case HTTPoison.get(source_url(), headers()) do
       {:ok, %Response{body: body, status_code: 200}} ->
         {:ok, format_data(body)}
 
@@ -49,16 +49,6 @@ defmodule Explorer.ExchangeRates.Source.CoinMarketCap do
     configured_url || "https://api.coinmarketcap.com"
   end
 
-  defp decode_json(data) do
-    Jason.decode!(data)
-  end
-
-  defp to_decimal(nil), do: nil
-
-  defp to_decimal(value) do
-    Decimal.new(value)
-  end
-
   defp source_url do
     "#{base_url()}/v1/ticker/?limit=0"
   end