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defmodule DaProductApp.TransactionEventChainService do |
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@moduledoc """ |
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Helper functions to work with the transaction_event_chain table. |
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append_event/1 will insert a new chain row and link it to the previous event |
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for the same transaction in a DB transaction to keep ordering deterministic. |
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""" |
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alias DaProductApp.{Repo, TransactionEventChain} |
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import Ecto.Query, only: [from: 2] |
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@doc """ |
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Append an event to the chain. |
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attrs must include: :transaction_id, :event_type, :event_ref_table |
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optional: :event_ref_id, :payload |
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Returns {:ok, chain_record} or {:error, reason} |
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""" |
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def append_event(attrs) when is_map(attrs) do |
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try do |
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Repo.transaction(fn -> |
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tx_id = Map.fetch!(attrs, :transaction_id) |
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prev = |
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from(c in TransactionEventChain, |
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where: c.transaction_id == ^tx_id, |
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order_by: [desc: c.inserted_at], |
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limit: 1 |
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) |
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|> Repo.one() |
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attrs = Map.put_new(attrs, :prev_event_id, prev && prev.id) |
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%TransactionEventChain{} |
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|> TransactionEventChain.changeset(attrs) |
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|> Repo.insert() |
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end) |
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rescue |
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e in DBConnection.ConnectionError -> |
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# Generic DB error (connection/table missing) - return an error tuple so callers can continue |
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{:error, :db_connection_error} |
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e in Ecto.QueryError -> |
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# Likely missing table or malformed query |
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Logger.warn("[TransactionEventChainService] append_event failed: #{inspect(e)}") |
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{:error, :no_table} |
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end |
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end |
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@doc """ |
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Traverse the chain for a transaction in ascending order (oldest first). |
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Returns a list of chain entries. |
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""" |
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def get_chain(transaction_id) do |
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from(c in TransactionEventChain, |
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where: c.transaction_id == ^transaction_id, |
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order_by: c.inserted_at |
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) |
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|> Repo.all() |
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end |
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@doc """ |
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Convenience method to append an event with transaction_id and event_type. |
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## Parameters |
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- `transaction_id`: The transaction ID |
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- `event_type`: String describing the event type |
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- `payload`: Optional map of event data |
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## Returns |
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- `{:ok, chain_record}` on success |
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- `{:error, reason}` on failure |
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""" |
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def append_event(transaction_id, event_type, payload \\ %{}) do |
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attrs = %{ |
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transaction_id: transaction_id, |
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event_type: event_type, |
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event_ref_table: "transaction_events", # Default reference table |
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payload: payload |
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} |
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append_event(attrs) |
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end |
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end |