defmodule OrgGarden.Config do
  @moduledoc """
  Centralized configuration access with validation.

  Provides a unified interface for accessing configuration values,
  with support for defaults and required value validation.

  ## Usage

      OrgGarden.Config.get(:http_port)
      #=> 8080

      OrgGarden.Config.get!(:quartz_path)
      #=> "/path/to/quartz" or raises if not set

      OrgGarden.Config.pipeline_opts()
      #=> %{zotero_url: "...", bibtex_file: nil, citation_mode: :warn}
  """

  @doc """
  Get a configuration value with an optional default.
  """
  def get(key, default \\ nil) do
    Application.get_env(:org_garden, key, default)
  end

  @doc """
  Get a required configuration value. Raises if not set.
  """
  def get!(key) do
    case Application.get_env(:org_garden, key) do
      nil -> raise ArgumentError, "Missing required configuration: #{key}"
      value -> value
    end
  end

  @doc """
  Build pipeline options map for transforms.
  """
  def pipeline_opts do
    %{
      zotero_url: get(:zotero_url, "http://localhost:23119"),
      bibtex_file: get(:bibtex_file),
      citation_mode: get(:citation_mode, :warn)
    }
  end

  @doc """
  Validate that all required configuration is present.
  Returns :ok or {:error, reasons}.
  """
  def validate do
    errors =
      []
      |> validate_quartz_path()
      |> validate_citation_mode()

    case errors do
      [] -> :ok
      errors -> {:error, errors}
    end
  end

  @doc """
  Validate configuration and raise on errors.
  """
  def validate! do
    case validate() do
      :ok -> :ok
      {:error, errors} -> raise "Configuration errors: #{inspect(errors)}"
    end
  end

  # Private validation helpers

  defp validate_quartz_path(errors) do
    case get(:quartz_path) do
      nil ->
        errors

      path ->
        cli_path = Path.join(path, "quartz/bootstrap-cli.mjs")

        if File.exists?(cli_path) do
          errors
        else
          [{:quartz_path, "bootstrap-cli.mjs not found at #{cli_path}"} | errors]
        end
    end
  end

  defp validate_citation_mode(errors) do
    case get(:citation_mode) do
      mode when mode in [:silent, :warn, :strict] -> errors
      other -> [{:citation_mode, "Invalid citation mode: #{inspect(other)}"} | errors]
    end
  end
end