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defmodule DaProductApp.ForeignExchange.FxRate do |
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@moduledoc """ |
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FX Rate schema for UPI International transactions. |
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Stores exchange rates between INR and foreign currencies with PSP markup. |
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Used for real-time currency conversion in international corridors. |
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""" |
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use Ecto.Schema |
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import Ecto.Changeset |
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import Ecto.Query |
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@primary_key {:id, :binary_id, autogenerate: true} |
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@foreign_key_type :binary_id |
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schema "fx_rates" do |
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field :base_currency, :string # "INR" (always INR for UPI International) |
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field :target_currency, :string # "USD", "EUR", "SGD", "AED" |
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field :fx_rate, :decimal # Exchange rate (e.g., 0.0165 for INR to SGD) |
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field :markup_rate, :decimal # PSP markup percentage (e.g., 2.50%) |
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field :effective_from, :utc_datetime |
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field :effective_until, :utc_datetime |
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field :active, :boolean, default: true |
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field :source, :string # "RBI", "PARTNER_API", "MANUAL" |
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field :corridor, :string # "SINGAPORE", "UAE", "USA" |
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field :last_modified_ts, :utc_datetime |
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field :created_by, :string # System user who created/updated |
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field :rate_type, :string # "SPOT", "FORWARD", "FIXED" |
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timestamps(type: :utc_datetime) |
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end |
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def changeset(fx_rate, attrs) do |
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fx_rate |
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|> cast(attrs, [ |
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:base_currency, :target_currency, :fx_rate, :markup_rate, |
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:effective_from, :effective_until, :active, :source, :corridor, |
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:last_modified_ts, :created_by, :rate_type |
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]) |
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|> validate_required([:base_currency, :target_currency, :fx_rate, :corridor]) |
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|> validate_inclusion(:base_currency, ["INR"]) |
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|> validate_inclusion(:target_currency, ["USD", "EUR", "SGD", "AED", "GBP", "JPY", "AUD"]) |
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|> validate_inclusion(:corridor, ["SINGAPORE", "UAE", "USA", "UK", "JAPAN", "AUSTRALIA"]) |
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|> validate_inclusion(:source, ["RBI", "PARTNER_API", "MANUAL", "EXTERNAL_FEED"]) |
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|> validate_inclusion(:rate_type, ["SPOT", "FORWARD", "FIXED"]) |
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|> validate_number(:fx_rate, greater_than: 0) |
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|> validate_number(:markup_rate, greater_than_or_equal_to: 0) |
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|> unique_constraint([:base_currency, :target_currency, :corridor, :active]) |
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end |
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@doc """ |
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Get current active rate for a currency pair in specific corridor |
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""" |
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def get_active_rate_query(from_currency, to_currency, corridor) do |
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now = DateTime.utc_now() |
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from r in __MODULE__, |
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where: r.base_currency == ^from_currency and |
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r.target_currency == ^to_currency and |
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r.corridor == ^corridor and |
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r.active == true and |
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r.effective_from <= ^now and |
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(is_nil(r.effective_until) or r.effective_until > ^now), |
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order_by: [desc: r.last_modified_ts], |
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limit: 1 |
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end |
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@doc """ |
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Calculate INR amount from foreign currency amount |
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""" |
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def calculate_inr_amount(foreign_amount, %__MODULE__{} = fx_rate) do |
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# INR = Foreign Amount ÷ FX Rate × (1 + Markup) |
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inr_before_markup = Decimal.div(foreign_amount, fx_rate.fx_rate) |
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markup_multiplier = Decimal.add(1, Decimal.div(fx_rate.markup_rate, 100)) |
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Decimal.mult(inr_before_markup, markup_multiplier) |
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end |
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@doc """ |
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Calculate foreign currency amount from INR amount |
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""" |
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def calculate_foreign_amount(inr_amount, %__MODULE__{} = fx_rate) do |
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# Remove markup first, then convert |
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markup_multiplier = Decimal.add(1, Decimal.div(fx_rate.markup_rate, 100)) |
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inr_without_markup = Decimal.div(inr_amount, markup_multiplier) |
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Decimal.mult(inr_without_markup, fx_rate.fx_rate) |
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end |
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end |