141 lines
3.6 KiB
Elixir
141 lines
3.6 KiB
Elixir
defmodule LineBot.TokenServer do
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@http Application.get_env(:line_bot, :api_client, HTTPoison)
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defmodule Behaviour do
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@moduledoc false
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@callback get_token() :: binary
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@callback revoke_token() :: term
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@callback purge() :: term
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end
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use GenServer
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@behaviour Behaviour
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require Logger
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@moduledoc """
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A GenServer that manages the [OAuth token](https://developers.line.biz/en/reference/messaging-api/#oauth)
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for Line API calls.
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This server is started automatically by the `:line_bot` application, and requires the
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`:client_id`, and `:client_secret` to have been configured.
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The current token is retrieved with `get_token/0`, which also fetches a new token from the auth
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server if the current one has expired (or has never been fetched).
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"""
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## Server
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@impl GenServer
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def init(_) do
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state = %{
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token: nil,
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expires_on: DateTime.utc_now(),
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client_id: Application.fetch_env!(:line_bot, :client_id),
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client_secret: Application.fetch_env!(:line_bot, :client_secret)
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}
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{:ok, state}
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end
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@impl GenServer
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def handle_call(:token, _from, state) do
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state =
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case DateTime.compare(state.expires_on, DateTime.utc_now()) do
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:gt -> state
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_ -> refresh_token(state)
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end
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{:reply, state.token, state}
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end
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@impl GenServer
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def handle_call(:revoke, from, state) do
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post_revoke_token(state.token)
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handle_call(:purge, from, state)
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end
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@impl GenServer
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def handle_call(:purge, _from, state) do
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{:reply, :ok, %{state | token: nil, expires_on: DateTime.utc_now()}}
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end
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defp refresh_token(state) do
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{token, expires_in} = post_request_token(state.client_id, state.client_secret)
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# Set the expiry 5 minutes earlier, to avoid edge cases
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expires_on = DateTime.add(DateTime.utc_now(), expires_in - 300, :second)
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Logger.info("Retrieved new access token that expires on #{expires_on}.")
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%{state | token: token, expires_on: expires_on}
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end
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defp headers do
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[
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{"Content-Type", "application/x-www-form-urlencoded"},
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{"User-Agent", "line-botsdk-elixir/v#{Application.spec(:line_bot, :vsn)}"}
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]
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end
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defp post_request_token(client_id, client_secret) do
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data = [
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grant_type: "client_credentials",
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client_id: client_id,
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client_secret: client_secret
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]
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%{"access_token" => access_token, "expires_in" => expires_in} =
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"https://api.line.me/v2/oauth/accessToken"
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|> @http.post!({:form, data}, headers())
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|> Map.get(:body)
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|> Jason.decode!()
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{access_token, expires_in}
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end
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defp post_revoke_token(access_token) do
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@http.post!(
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"https://api.line.me/v2/oauth/revoke",
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{:form, [access_token: access_token]},
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headers()
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)
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end
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## Client
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@doc false
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def start_link(opts) do
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GenServer.start_link(__MODULE__, opts, name: __MODULE__)
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end
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@doc """
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Gets the currently stored token. If the token has expired, a new token is retrieved.
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"""
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@impl Behaviour
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def get_token() do
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GenServer.call(__MODULE__, :token)
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end
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@doc """
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Revokes the current access token. This revokes the token with the API server, so the token will
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become invalid and cannot be used elsewhere.
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A new token will be retrieved on the next call
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to `get_token/0`.
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"""
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@impl Behaviour
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def revoke_token() do
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GenServer.call(__MODULE__, :revoke)
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end
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@doc """
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Purges the current access token. This only removes the token from this process' state, it does
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not revoke the token.
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A new token will be retrieved on the next call to `get_token/0`.
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To revoke the token, use `revoke_token/0`.
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"""
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@impl Behaviour
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def purge() do
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GenServer.call(__MODULE__, :purge)
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end
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end
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