defmodule AshAge.Migration do
  @moduledoc """
  Migration helpers for Apache AGE graph database.

  Provides functions to create and drop AGE graphs, labels, and indexes
  within Ecto migrations.

  ## Usage

      defmodule MyApp.Repo.Migrations.CreateAgeGraph do
        use Ecto.Migration
        import AshAge.Migration

        def up do
          create_age_graph("my_graph")
          create_vertex_label("my_graph", "Entity")
          create_edge_label("my_graph", "RELATES_TO")
          create_vertex_index("my_graph", "Entity", "tenant_id")
        end

        def down do
          drop_age_graph("my_graph")
        end
      end
  """

  @doc """
  Creates an AGE graph with the given name.
  """
  @spec create_age_graph(String.t()) :: :ok
  def create_age_graph(graph_name) do
    validate_identifier!(graph_name)
    execute("SELECT ag_catalog.create_graph('#{graph_name}')")
    :ok
  end

  @doc """
  Drops an AGE graph and all its data.
  """
  @spec drop_age_graph(String.t()) :: :ok
  def drop_age_graph(graph_name) do
    validate_identifier!(graph_name)
    execute("SELECT ag_catalog.drop_graph('#{graph_name}', true)")
    :ok
  end

  @doc """
  Creates a vertex label in the given graph.
  """
  @spec create_vertex_label(String.t(), String.t()) :: :ok
  def create_vertex_label(graph_name, label) do
    validate_identifier!(graph_name)
    validate_identifier!(label)
    execute("SELECT ag_catalog.create_vlabel('#{graph_name}', '#{label}')")
    :ok
  end

  @doc """
  Creates an edge label in the given graph.
  """
  @spec create_edge_label(String.t(), String.t()) :: :ok
  def create_edge_label(graph_name, label) do
    validate_identifier!(graph_name)
    validate_identifier!(label)
    execute("SELECT ag_catalog.create_elabel('#{graph_name}', '#{label}')")
    :ok
  end

  @doc """
  Creates an index on a vertex property.

  Uses `ag_catalog.agtype_access_operator()` instead of the `->>` operator
  because `public` comes before `ag_catalog` in the search path.
  """
  @spec create_vertex_index(String.t(), String.t(), String.t()) :: :ok
  def create_vertex_index(graph_name, label, property) do
    validate_identifier!(graph_name)
    validate_identifier!(label)
    validate_identifier!(property)

    execute("""
    CREATE INDEX IF NOT EXISTS idx_#{graph_name}_#{label}_#{property}
    ON #{graph_name}.#{label}
    USING btree (ag_catalog.agtype_access_operator(properties, '#{property}'))
    """)

    :ok
  end

  @doc """
  Creates an index on an edge property.

  Uses `ag_catalog.agtype_access_operator()` instead of the `->>` operator
  because `public` comes before `ag_catalog` in the search path.
  """
  @spec create_edge_index(String.t(), String.t(), String.t()) :: :ok
  def create_edge_index(graph_name, label, property) do
    validate_identifier!(graph_name)
    validate_identifier!(label)
    validate_identifier!(property)

    execute("""
    CREATE INDEX IF NOT EXISTS idx_#{graph_name}_#{label}_#{property}
    ON #{graph_name}.#{label}
    USING btree (ag_catalog.agtype_access_operator(properties, '#{property}'))
    """)

    :ok
  end

  @doc false
  def validate_identifier!(name) when is_binary(name) do
    unless Regex.match?(~r/\A[a-zA-Z_][a-zA-Z0-9_]*\z/, name) do
      raise ArgumentError,
            "invalid AGE identifier: #{inspect(name)}. " <>
              "Must start with a letter or underscore and contain only alphanumeric characters and underscores."
    end

    name
  end

  def validate_identifier!(name) when is_atom(name) do
    validate_identifier!(Atom.to_string(name))
  end

  defp execute(sql) do
    Ecto.Migration.execute(sql)
  end
end