defmodule OEmbedProviders.Provider do
  @moduledoc """
  Represents an OEmbed provider.
  """
  use OEmbedProviders.Parser
  alias OEmbedProviders.Provider
  alias OEmbedProviders.Provider.Endpoint

  @type t :: %__MODULE__{
          provider_name: String.t() | nil,
          provider_url: String.t() | nil,
          endpoints: [Endpoint.t()]
        }

  defstruct provider_name: nil, provider_url: nil, endpoints: []

  @doc """
  Convert a map into a `OEmbedProviders.Provider` struct.
  """
  @spec from_map(data :: map()) :: Provider.t()
  def from_map(data) when is_map(data) do
    data = atomize_keys(data)

    Provider
    |> struct(data)
    |> parse_endpoints()
  end

  defp parse_endpoints(%Provider{endpoints: endpoints} = provider) when is_list(endpoints) do
    parsed = Enum.map(endpoints, &Endpoint.from_map/1)
    Map.put(provider, :endpoints, parsed)
  end

  defp parse_endpoints(provider), do: provider

  @doc """
  Check if the given URL matches this `Provider`.
  """
  @spec matches?(provider :: Provider.t(), url :: String.t()) :: boolean()
  def matches?(%Provider{endpoints: endpoints}, url) when is_list(endpoints) do
    Enum.any?(endpoints, &Endpoint.matches?(&1, url))
  end

  def matches?(_provider, _url), do: false

  @doc """
  Get the `OEmbedProviders.Provider.Endpoint` for a `Provider`.
  """
  @spec find_endpoint(provider :: Provider.t(), url :: String.t()) :: Endpoint.t() | nil
  def find_endpoint(%Provider{endpoints: endpoints}, url) when is_list(endpoints) do
    Enum.find(endpoints, &Endpoint.matches?(&1, url))
  end

  def find_endpoint(_provider, _url), do: false

  @doc """
  Construct the OEmbed endpoint URL for the given `Provider` and URL.
  """
  @spec oembed_url(provider :: Provider.t(), url :: String.t()) ::
          {:ok, String.t()} | {:error, any()}
  def oembed_url(%Provider{} = provider, url) do
    format = "json"
    params = %{"url" => url, "format" => format}
    q = URI.encode_query(params)

    with %Endpoint{url: endpoint_url} <- find_endpoint(provider, url) do
      result =
        endpoint_url
        |> String.replace("*", URI.encode_www_form(url))
        |> String.replace("{format}", URI.encode_www_form(format))
        |> URI.merge("?#{q}")
        |> URI.to_string()

      {:ok, result}
    else
      nil -> {:error, :no_provider}
      error -> {:error, error}
    end
  end
end