defmodule URL do
  @moduledoc """
  Functions for parsing URLs

  This module provides functions for parsing URLs. It is modelled on
  Elixir's `URI` module but will also parse scheme-specific URIs such
  as [geo](https://tools.ietf.org/rfc/rfc5870), [data](https://tools.ietf.org/html/rfc2397)
  [tel](https://tools.ietf.org/html/rfc3966), [mailto](https://tools.ietf.org/html/rfc2047),
  and [uuid](https://tools.ietf.org/html/draft-kindel-uuid-uri-00).

  """
  @type uri_type :: nil | URL.Data.t() | URL.Geo.t() | URL.Tel.t() | URL.UUID.t() | URL.Mailto.t()
  defstruct scheme: nil,
    path: nil,
    query: nil,
    fragment: nil,
    authority: nil,
    userinfo: nil,
    host: nil,
    port: nil,
    parsed_path: nil

  @type t() :: %__MODULE__{
    authority: nil | binary(),
    fragment: nil | binary(),
    host: nil | binary(),
    path: nil | binary(),
    port: nil | :inet.port_number(),
    query: nil | binary(),
    scheme: nil | binary(),
    userinfo: nil | binary(),
    parsed_path: uri_type()
  }

  @supported_schemes %{
    "tel" => URL.Tel,
    "data" => URL.Data,
    "geo" =>  URL.Geo,
    "mailto" => URL.Mailto,
    "uuid" => URL.UUID,
    "urn" => URL.UUID
  }

  import URL.ParseHelpers.Core, only: [structify: 2]
  import NimbleParsec
  import URL.ParseHelpers.{Core, Mailto, Params, Unwrap}

  @doc """
  Parses a url and returns a %URL{} struct that
  has the same shape as Elixir's %URI{} with the
  addition of the `parsed_path` key.

  ## Example

    iex> URL.parse("geo:48.198634,-16.371648,3.4;crs=wgs84;u=40.0")
    %URL{
      authority: nil,
      fragment: nil,
      host: nil,
      parsed_path: %URL.Geo{
        alt: 3.4,
        lat: 48.198634,
        lng: -16.371648,
        params: %{"crs" => "wgs84", "u" => 40.0}
      },
      path: "48.198634,-16.371648,3.4;crs=wgs84;u=40.0",
      port: nil,
      query: nil,
      scheme: "geo",
      userinfo: nil
    }

  """
  @spec parse(url :: binary()) :: __MODULE__.t()
  def parse(url) when is_binary(url) do
    url
    |> parse_scheme
    |> merge_uri
  end

  @doc """
  Parse a URL query string and percent decode.

  ## Returns

  * Either a map of query params or

  * an `{:error, {URL.Parser.ParseError, reason}}` tuple

  ## Examples

      iex> URL.parse_query_string "url=http%3a%2f%2ffonzi.com%2f&name=Fonzi&mood=happy&coat=leather"
      %{
        "coat" => "leather",
        "mood" => "happy",
        "name" => "Fonzi",
        "url" => "http://fonzi.com/"
      }

      iex> mailto = "mailto:user@%E7%B4%8D%E8%B1%86.example.org?subject=Test&body=NATTO"
      iex> URL.parse(mailto) |> URL.parse_query_string
      %{"body" => "NATTO", "subject" => "Test"}

  """
  @spec parse_query_string(String.t() | map()) :: map() | {:error, {module(), binary()}}
  def parse_query_string(query) when is_binary(query) do
    with {:ok, [params]} <- unwrap(parse_query(query)) do
      params
    end
  end

  def parse_query_string({:error, {_, _}} = error) do
    error
  end

  def parse_query_string(%{query: query}) do
    parse_query_string(query)
  end

  @doc false
  def parse_query(nil) do
    {:ok, [%{}], "", %{}, {0, 0}, 0}
  end

  defparsec :parse_query,
    optional(hfields())

  defdelegate to_string(url), to: URI

  defp parse_scheme(url) when is_binary(url) do
    url
    |> URI.parse
    |> parse_scheme
  end

  for {scheme, module} <- @supported_schemes do
    defp parse_scheme(%URI{scheme: unquote(scheme)} = uri) do
      {uri, unquote(module).parse(uri)}
    end
  end

  defp parse_scheme(%URI{} = uri) do
    {uri, nil}
  end

  defp merge_uri({uri, parsed_path}) do
    uri
    |> Map.to_list
    |> Enum.map(&__MODULE__.trim/1)
    |> structify(__MODULE__)
    |> add_parsed_path(parsed_path)
  end

  defp add_parsed_path(url, parsed_path) do
    Map.put(url, :parsed_path, parsed_path)
  end

  @doc false
  def trim({key, item}) when is_binary(item) do
    {key, String.trim(item)}
  end

  def trim(other) do
    other
  end
end