Pure helper functions for building standard job-store SQL.

Use this module when writing a custom Core.JobStore adapter for any SQL database (PostgreSQL, MySQL, SQLite, etc.). It handles schema DDL, param encoding, and row deserialization so the adapter only needs to manage the connection.

Example PostgreSQL adapter skeleton

defmodule MyApp.JobStore.Postgres do
  @behaviour Core.JobStore
  alias Core.JobStore.SQL

  def init(_opts) do
    {table, index} = SQL.schema()
    Postgrex.query!(conn(), table, [])
    Postgrex.query!(conn(), index, [])
    :ok
  end

  def insert_job(job) do
    {sql, params} = SQL.insert_params(job)
    %{rows: [[id]]} = Postgrex.query!(conn(), sql <> " RETURNING id", params)
    {:ok, %Core.Workers.Job{job | id: id}}
  end

  def update_job(id, changes) do
    {sql, params} = SQL.update_params(id, changes)
    Postgrex.query!(conn(), sql, params)
    :ok
  end

  def get_job(id) do
    %{rows: rows} = Postgrex.query!(conn(), SQL.select_by_id(), [id])
    case rows do
      [row | _] -> {:ok, SQL.from_row(row)}
      []        -> {:error, :not_found}
    end
  end

  def list_jobs(opts) do
    {sql, params} =
      if status = Keyword.get(opts, :status) do
        {SQL.select_by_status(), [Atom.to_string(status)]}
      else
        {SQL.select_all(), []}
      end

    %{rows: rows} = Postgrex.query!(conn(), sql, params)
    Enum.map(rows, &SQL.from_row/1)
  end

  def cleanup(opts) do
    {sql, params} = SQL.cleanup_params(Keyword.get(opts, :max_age_days, 7))
    Postgrex.query!(conn(), sql, params)
    :ok
  end

  defp conn, do: MyApp.Repo
end