9528700862
All modules, configs, paths, and references updated. 836 tests pass, zero warnings. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
103 lines
2.8 KiB
Elixir
103 lines
2.8 KiB
Elixir
defmodule Berrypod.ExchangeRate do
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@moduledoc """
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Fetches and caches exchange rates for shipping cost conversion.
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Uses the frankfurter.app API (ECB data, free, no API key).
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Rates are fetched during product sync and cached in Settings so
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they survive restarts without an API call.
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"""
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alias Berrypod.Settings
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require Logger
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@api_base "https://api.frankfurter.app"
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@settings_prefix "exchange_rate_"
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@default_rates %{"USD" => 0.80, "EUR" => 0.86}
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@doc """
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Fetches the latest exchange rates to GBP from the API and caches them.
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Returns `{:ok, rates_map}` or `{:error, reason}`.
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The rates map has currency codes as keys and GBP multipliers as values,
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e.g. `%{"USD" => 0.7892, "EUR" => 0.8534}`.
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"""
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def fetch_and_cache do
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case fetch_from_api() do
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{:ok, rates} ->
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cache_rates(rates)
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{:ok, rates}
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{:error, reason} ->
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Logger.warning("Exchange rate fetch failed: #{inspect(reason)}, using cached rates")
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{:ok, get_cached_rates()}
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end
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end
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@doc """
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Returns cached exchange rates from Settings, falling back to defaults.
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"""
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def get_cached_rates do
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Enum.reduce(@default_rates, %{}, fn {currency, default}, acc ->
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key = @settings_prefix <> String.downcase(currency) <> "_to_gbp"
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rate =
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case Settings.get_setting(key) do
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nil -> default
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val when is_binary(val) -> String.to_float(val)
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val when is_number(val) -> val / 1
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end
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Map.put(acc, currency, rate)
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end)
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end
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@doc """
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Returns the GBP rate for a given currency, using cached values.
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"""
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def rate_for(currency) when currency in ["GBP", "gbp"], do: 1.0
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def rate_for(currency) do
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rates = get_cached_rates()
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Map.get(
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rates,
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String.upcase(currency),
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Map.get(@default_rates, String.upcase(currency), 0.80)
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)
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end
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# Fetch from frankfurter.app API
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defp fetch_from_api do
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url = "#{@api_base}/latest?from=USD&to=GBP,EUR"
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case Req.get(url, receive_timeout: 10_000) do
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{:ok, %{status: 200, body: %{"rates" => rates}}} ->
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# API returns rates FROM USD, so "GBP" value is the USD→GBP multiplier
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gbp_per_usd = rates["GBP"]
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# Derive EUR→GBP: if 1 USD = X GBP and 1 USD = Y EUR, then 1 EUR = X/Y GBP
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eur_rate = rates["EUR"]
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eur_to_gbp =
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if eur_rate && eur_rate > 0,
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do: gbp_per_usd / eur_rate,
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else: @default_rates["EUR"]
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{:ok, %{"USD" => gbp_per_usd, "EUR" => eur_to_gbp}}
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{:ok, %{status: status}} ->
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{:error, {:http_status, status}}
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{:error, reason} ->
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{:error, reason}
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end
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end
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defp cache_rates(rates) do
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Enum.each(rates, fn {currency, rate} ->
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key = @settings_prefix <> String.downcase(currency) <> "_to_gbp"
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Settings.put_setting(key, Float.to_string(rate))
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end)
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end
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end
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