server_logger

defmodule ServerLogger.Migration do
  @moduledoc """
  Provides migration functions for setting up the ServerLogger database tables.

  Used by the generated migration file from `mix server_logger.gen.migration`.

  ## Usage

  After running `mix server_logger.gen.migration`, the generated file will contain:

      defmodule MyApp.Repo.Migrations.CreateServerLogs do
        use Ecto.Migration

        def up, do: ServerLogger.Migration.up()
        def down, do: ServerLogger.Migration.down()
      end
  """

  use Ecto.Migration

  def up do
    # Parent partitioned table — raw SQL required for PARTITION BY
    execute("""
    CREATE TABLE server_logs (
      id bigserial NOT NULL,
      level varchar NOT NULL,
      message text NOT NULL,
      module varchar,
      function varchar,
      request_id varchar,
      pid varchar,
      metadata jsonb DEFAULT '{}',
      logged_at timestamptz NOT NULL,
      inserted_at timestamptz NOT NULL DEFAULT now(),
      PRIMARY KEY (id, logged_at)
    ) PARTITION BY RANGE (logged_at)
    """)

    # Indexes on parent (inherited by all partitions)
    execute("CREATE INDEX server_logs_logged_at_idx ON server_logs (logged_at)")
    execute("CREATE INDEX server_logs_level_idx ON server_logs (level)")
    execute("CREATE INDEX server_logs_module_idx ON server_logs (module)")
    execute("CREATE INDEX server_logs_request_id_idx ON server_logs (request_id)")

    # Create current month + next month partitions dynamically
    today = Date.utc_today()
    create_partition(today.year, today.month)

    next = Date.utc_today() |> Date.end_of_month() |> Date.add(1)
    create_partition(next.year, next.month)
  end

  def down do
    execute("DROP TABLE IF EXISTS server_logs CASCADE")
  end

  defp create_partition(year, month) do
    name = partition_name(year, month)
    from_date = Date.new!(year, month, 1)
    to_date = from_date |> Date.end_of_month() |> Date.add(1)

    execute("""
    CREATE TABLE IF NOT EXISTS #{name} PARTITION OF server_logs
      FOR VALUES FROM ('#{from_date}') TO ('#{to_date}')
    """)
  end

  defp partition_name(year, month) do
    "server_logs_#{year}#{String.pad_leading(Integer.to_string(month), 2, "0")}"
  end
end