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116 lines
3.7 KiB
Elixir
116 lines
3.7 KiB
Elixir
defmodule AshDoubleEntry.Transfer.Changes.VerifyTransfer do
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# Verify a transfer and update all related balances of the accounts involved.
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# This operation locks the accounts involved, serializing all transfers between
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# relevant accounts.
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@moduledoc false
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use Ash.Resource.Change
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require Ash.Query
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def change(changeset, _opts, context) do
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changeset
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|> Ash.Changeset.before_action(fn changeset ->
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timestamp = Ash.Changeset.get_attribute(changeset, :timestamp)
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timestamp =
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case timestamp do
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nil -> System.system_time(:millisecond)
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timestamp -> DateTime.to_unix(timestamp, :millisecond)
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end
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ulid = AshDoubleEntry.ULID.generate(timestamp)
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Ash.Changeset.force_change_attribute(changeset, :id, ulid)
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end)
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|> Ash.Changeset.after_action(fn changeset, result ->
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from_account_id = Ash.Changeset.get_attribute(changeset, :from_account_id)
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to_account_id = Ash.Changeset.get_attribute(changeset, :to_account_id)
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amount = Ash.Changeset.get_attribute(changeset, :amount)
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accounts =
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changeset.resource
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|> AshDoubleEntry.Transfer.Info.transfer_account_resource!()
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|> Ash.Query.filter(id in ^[from_account_id, to_account_id])
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|> Ash.Query.for_read(:lock_accounts)
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|> Ash.Query.load(balance_as_of_ulid: %{ulid: result.id})
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|> changeset.api.read!(authorize?: false, tracer: context[:tracer])
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from_account = Enum.find(accounts, &(&1.id == from_account_id))
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to_account = Enum.find(accounts, &(&1.id == to_account_id))
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new_from_account_balance =
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Decimal.sub(from_account.balance_as_of_ulid, amount)
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new_to_account_balance =
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Decimal.add(to_account.balance_as_of_ulid, amount)
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changeset.resource
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|> AshDoubleEntry.Transfer.Info.transfer_balance_resource!()
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|> Ash.Changeset.for_create(
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:upsert_balance,
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%{
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account_id: from_account.id,
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transfer_id: result.id,
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balance: new_from_account_balance,
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account: from_account
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},
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context_to_opts(context)
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)
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|> changeset.api.create!()
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changeset.resource
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|> AshDoubleEntry.Transfer.Info.transfer_balance_resource!()
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|> Ash.Changeset.for_create(
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:upsert_balance,
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%{
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account_id: to_account.id,
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transfer_id: result.id,
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balance: new_to_account_balance
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},
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context_to_opts(context)
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)
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|> changeset.api.create!()
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# Turn this into a bulk update when we support it in Ash core
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changeset.resource
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|> AshDoubleEntry.Transfer.Info.transfer_balance_resource!()
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|> Ash.Query.filter(account_id in ^[from_account.id, to_account.id])
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|> Ash.Query.filter(transfer_id > ^result.id)
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|> changeset.api.stream!()
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|> Stream.map(fn balance ->
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if balance.account_id == from_account.id do
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%{
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account_id: balance.account_id,
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transfer_id: balance.transfer_id,
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balance: Decimal.sub(balance.balance, amount)
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}
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else
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%{
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account_id: balance.account_id,
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transfer_id: balance.transfer_id,
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balance: Decimal.add(balance.balance, amount)
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}
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end
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end)
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|> changeset.api.bulk_create!(
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AshDoubleEntry.Transfer.Info.transfer_balance_resource!(changeset.resource),
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:upsert_balance,
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context_to_opts(context,
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return_errors?: true,
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stop_on_error?: true,
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upsert_fields: [:balance]
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)
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)
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{:ok, result}
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end)
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end
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defp context_to_opts(context, opts \\ []) do
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context
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|> Map.take([:tenant, :actor, :tracer])
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|> Map.to_list()
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|> Keyword.merge(opts)
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end
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end
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