first_last_frame

defmodule FirstLastFrame do
  @moduledoc """
  Provides functions for generating URLs and extracting information
  related to the first and last frames of a video on Supermaker.ai.
  """

  @base_url "https://supermaker.ai/video"

  @doc """
  Builds a URL for a video's first/last frame based on its ID and optional parameters.

  ## Examples

      iex> FirstLastFrame.build_url("abc123xyz")
      "https://supermaker.ai/video/abc123xyz"

      iex> FirstLastFrame.build_url("abc123xyz", frame: "first")
      "https://supermaker.ai/video/abc123xyz?frame=first"

      iex> FirstLastFrame.build_url("abc123xyz", frame: "last", timestamp: 1000)
      "https://supermaker.ai/video/abc123xyz?frame=last&timestamp=1000"
  """
  def build_url(video_id, opts \\ []) when is_binary(video_id) do
    @base_url
    |> Path.join(video_id)
    |> build_query_string(opts)
  end

  defp build_query_string(base_url, opts) when is_list(opts) do
    query_params =
      opts
      |> Enum.reject(fn {_, value} -> is_nil(value) end)
      |> Enum.map(fn {key, value} -> "#{key}=#{value}" end)
      |> Enum.join("&")

    case query_params do
      "" ->
        base_url

      _ ->
        "#{base_url}?#{query_params}"
    end
  end

  @doc """
  Determines if a URL is a Supermaker video URL.

  ## Examples

      iex> FirstLastFrame.is_supermaker_url?("https://supermaker.ai/video/abc123xyz")
      true

      iex> FirstLastFrame.is_supermaker_url?("https://example.com/video/abc123xyz")
      false
  """
  def is_supermaker_url?(url) when is_binary(url) do
    String.starts_with?(url, @base_url)
  end

  @doc """
  Extracts the video ID from a Supermaker video URL.
  Returns `nil` if the URL is not a valid Supermaker video URL.

  ## Examples

      iex> FirstLastFrame.extract_video_id("https://supermaker.ai/video/abc123xyz")
      "abc123xyz"

      iex> FirstLastFrame.extract_video_id("https://example.com/video/abc123xyz")
      nil
  """
  def extract_video_id(url) when is_binary(url) do
    case String.replace_prefix(url, @base_url <> "/", "") do
      remaining_path when String.length(remaining_path) > 0 ->
        case String.split(remaining_path, "?") do
          [video_id | _] -> video_id
          _ -> nil
        end
      _ ->
        nil
    end
  end

  @doc """
  Generates a timestamp parameter for a given number of seconds.

  ## Examples

      iex> FirstLastFrame.timestamp_param(10)
      [timestamp: 10]

      iex> FirstLastFrame.timestamp_param(0)
      [timestamp: 0]
  """
  def timestamp_param(seconds) when is_integer(seconds) do
    [timestamp: seconds]
  end
end