ash_postgres/lib/multitenancy.ex

defmodule AshPostgres.MultiTenancy do
  @moduledoc false

  @dialyzer {:nowarn_function, load_migration!: 1}

  @tenant_name_regex ~r/^[a-zA-Z0-9_-]+$/
  def create_tenant!(tenant_name, repo) do
    Ecto.Adapters.SQL.query!(repo, "CREATE SCHEMA IF NOT EXISTS \"#{tenant_name}\"", [])

    migrate_tenant(tenant_name, repo)
  end

  def migrate_tenant(tenant_name, repo, migrations_path \\ nil) do
    tenant_migrations_path =
      migrations_path ||
        repo.config()[:tenant_migrations_path] || default_tenant_migration_path(repo)

    Code.compiler_options(ignore_module_conflict: true)

    Ecto.Migration.SchemaMigration.ensure_schema_migrations_table!(
      repo,
      repo.config(),
      prefix: tenant_name
    )

    [tenant_migrations_path, "**", "*.exs"]
    |> Path.join()
    |> Path.wildcard()
    |> Enum.map(&extract_migration_info/1)
    |> Enum.filter(& &1)
    |> Enum.map(&load_migration!/1)
    |> Enum.each(fn {version, mod} ->
      Ecto.Migration.Runner.run(
        repo,
        [],
        version,
        mod,
        :forward,
        :up,
        :up,
        all: true,
        prefix: tenant_name
      )

      Ecto.Migration.SchemaMigration.up(repo, repo.config(), version, prefix: tenant_name)
    end)
  after
    Code.compiler_options(ignore_module_conflict: false)
  end

  # sobelow_skip ["SQL"]
  def rename_tenant(repo, old_name, new_name) do
    validate_tenant_name!(old_name)
    validate_tenant_name!(new_name)

    if to_string(old_name) != to_string(new_name) do
      Ecto.Adapters.SQL.query(repo, "ALTER SCHEMA \"#{old_name}\" RENAME TO \"#{new_name}\"")
    end

    :ok
  end

  defp load_migration!({version, _, file}) when is_binary(file) do
    loaded_modules = file |> Code.compile_file() |> Enum.map(&elem(&1, 0))

    if mod = Enum.find(loaded_modules, &migration?/1) do
      {version, mod}
    else
      raise Ecto.MigrationError,
            "file #{Path.relative_to_cwd(file)} does not define an Ecto.Migration"
    end
  end

  defp migration?(mod) do
    function_exported?(mod, :__migration__, 0)
  end

  defp extract_migration_info(file) do
    base = Path.basename(file)

    case Integer.parse(Path.rootname(base)) do
      {integer, "_" <> name} -> {integer, name, file}
      _ -> nil
    end
  end

  defp validate_tenant_name!(tenant_name) do
    unless Regex.match?(@tenant_name_regex, tenant_name) do
      raise "Tenant name must match #{inspect(@tenant_name_regex)}, got: #{tenant_name}"
    end
  end

  defp default_tenant_migration_path(repo) do
    repo_name = repo |> Module.split() |> List.last() |> Macro.underscore()
    otp_app = repo.config()[:otp_app]

    :code.priv_dir(otp_app)
    |> Path.join(repo_name)
    |> Path.join("tenant_migrations")
  end
end