defmodule DaProductApp.Repo.Migrations.AddVersionToParameterTemplates do
  use Ecto.Migration

  # Using up/down instead of change because:
  # 1. MySQL 8.0 does NOT support "ADD COLUMN IF NOT EXISTS" (MariaDB only)
  # 2. A prior partial run already committed the column (MySQL DDL auto-commits)
  #    but the migration was never recorded — so we guard with column_exists?/3

  def up do
    unless column_exists?(:parameter_templates, :version) do
      alter table(:parameter_templates) do
        add :version, :string, size: 50, default: "1.0.0"
      end
    end

    # Simple lookup index only.
    # A 4-column unique index (vendor + model + name + version) exceeds
    # MySQL's 3072-byte key-length limit for utf8mb4 tables.
    # (255+255+255+50 chars × 4 bytes = ~3260 bytes > 3072 byte limit)
    # Uniqueness of template identity is already enforced by the existing
    # (vendor, model, name) constraint created with the table.
    create_if_not_exists index(:parameter_templates, [:version])
  end

  def down do
    drop_if_exists index(:parameter_templates, [:version])

    if column_exists?(:parameter_templates, :version) do
      alter table(:parameter_templates) do
        remove :version
      end
    end
  end
end