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ex_money
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5.24.1
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2.12.0
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0.0.4
retired
0.0.3
retired
0.0.2
retired
Money functions for operations on and localization of a money data type with support for ISO 4217 currencies and ISO 24165 digial tokens (crypto currencies).
Retired package: Deprecated
Current section
Files
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Current section
Files
lib/money/exchange_rates/exchange_rates_retriever.ex
defmodule Money.ExchangeRates.Retriever do
@moduledoc """
Implements a `GenServer` to retrieve exchange rates from
a configured retrieveal module on a periodic basis. By default exchange
rates are retrieved from [Open Exchange Rates](http://openexchangerates.org).
Retrieved data is stored in an `:ets` table.
By default the period of execution is 5 minutes (300_000 microseconds). The
period of retrieval is configured in `config.exs` or the appropriate
environment configuration. For example:
config :ex_money,
open_exchange_rates_app_id: "app_id_string",
open_exchange_rates_retrieve_every: 300_000
"""
use GenServer
require Logger
alias Money.ExchangeRates
def start_link(name, config) do
GenServer.start_link(__MODULE__, config, name: name)
end
def init(config) do
log(config, :info, "Starting exchange rate retrieval service")
initialize_ets_table()
config = if function_exported?(config.api_module, :init, 1) do
log(config, :info, "Initializing retrieval module #{inspect config.api_module}")
config.api_module.init(config)
else
config
end
case config.delay_before_first_retrieval do
delay when is_integer(delay) and delay > 0 ->
log(config, :info, log_init_message(delay, config.retrieve_every))
schedule_work(delay)
_ ->
log(config, :info, log_init_message(config.retrieve_every))
schedule_work(config.retrieve_every)
end
{:ok, config}
end
def handle_info(:latest, config) do
retrieve_latest_rates(config)
schedule_work(config.retrieve_every)
{:noreply, config}
end
def retrieve_latest_rates(%{callback_module: callback_module} = config) do
case ExchangeRates.get_latest_rates(config) do
{:ok, rates} ->
retrieved_at = DateTime.utc_now
store_rates(rates, retrieved_at)
apply(callback_module, :rates_retrieved, [rates, retrieved_at])
log(config, :success, "Retrieved exchange rates successfully")
{:ok, rates}
{:error, reason} ->
log(config, :failure, "Could not retrieve exchange rates: #{inspect reason}")
{:error, reason}
end
end
defp schedule_work(delay_ms) do
Process.send_after(self(), :latest, delay_ms)
end
defp initialize_ets_table do
:ets.new(:exchange_rates, [:named_table, read_concurrency: true])
end
defp store_rates(rates, retrieved_at) do
:ets.insert(:exchange_rates, {:rates, rates})
:ets.insert(:exchange_rates, {:last_updated, retrieved_at})
end
def log(%{log_levels: log_levels}, key, message) do
case Map.get(log_levels, key) do
nil ->
nil
log_level ->
Logger.log(log_level, message)
end
end
defp log_init_message(delay, every) when delay < 1_000 do
"Rates will be retrieved in #{delay} milliseconds " <>
"and then every #{div(every, 1000)} seconds."
end
defp log_init_message(delay, every) do
"Rates will be retrieved in #{div(delay, 1000)} seconds " <>
"and then every #{div(every, 1000)} seconds."
end
defp log_init_message(every) do
"Rates will be retrieved every #{div(every, 1000)} seconds."
end
end