Rewrite project, add daily update of services list

The project was rewritten from Elixir to Go, primarily because:

- I don't write Elixir anymore and don't want to maintain a project in a
  language I no longer write
- I already write Go for other projects, including my day job, so it's
  a safer bet for a project that I want to maintain long term
- Go allows me to build portable executables that will make it easier
  for others to run farside on their own machines

The Go version of Farsside also has a built in task to fetch the latest
services{-full}.json file from the repo and ingest it, which makes
running a farside server a lot simpler.

It also automatically fetches the latest instance state from
https://farside.link unless configured as a primary farside node, which
will allow others to use farside without increasing traffic to all
instances that are queried by farside (just to the farside node itself).

8 files changed, 0 insertions, 437 deletions

diff --git a/lib/farside.ex b/lib/farside.ex
deleted file mode 100644
index 348f77c..0000000
--- a/lib/farside.ex
+++ /dev/null
@@ -1,142 +0,0 @@
-  defmodule Farside do
-  @service_prefix Application.compile_env!(:farside, :service_prefix)
-  @fallback_suffix Application.compile_env!(:farside, :fallback_suffix)
-  @previous_suffix Application.compile_env!(:farside, :previous_suffix)
-
-  # Define relation between available services and their parent service.
-  # This enables Farside to redirect with links such as:
-  # farside.link/https://www.youtube.com/watch?v=dQw4w9WgXcQ
-  @youtube_regex ~r/youtu(.be|be.com)|invidious|piped/
-  @twitter_regex ~r/twitter.com|x.com|nitter/
-  @reddit_regex ~r/reddit.com|libreddit|redlib/
-  @instagram_regex ~r/instagram.com|proxigram/
-  @wikipedia_regex ~r/wikipedia.org|wikiless/
-  @medium_regex ~r/medium.com|scribe/
-  @odysee_regex ~r/odysee.com|librarian/
-  @imgur_regex ~r/imgur.com|rimgo/
-  @gtranslate_regex ~r/translate.google.com|lingva/
-  @tiktok_regex ~r/tiktok.com|proxitok/
-  @imdb_regex ~r/imdb.com|libremdb/
-  @quora_regex ~r/quora.com|quetre/
-  @gsearch_regex ~r/google.com\/search|whoogle/
-  @fandom_regex ~r/fandom.com|breezewiki/
-  @github_regex ~r/github.com|gothub/
-  @stackoverflow_regex ~r/stackoverflow.com|anonymousoverflow/
-
-  @parent_services %{
-    @youtube_regex => ["invidious", "piped"],
-    @reddit_regex => ["libreddit", "redlib"],
-    @instagram_regex => ["proxigram"],
-    @twitter_regex => ["nitter"],
-    @wikipedia_regex => ["wikiless"],
-    @medium_regex => ["scribe"],
-    @odysee_regex => ["librarian"],
-    @imgur_regex => ["rimgo"],
-    @gtranslate_regex => ["lingva"],
-    @tiktok_regex => ["proxitok"],
-    @imdb_regex => ["libremdb"],
-    @quora_regex => ["quetre"],
-    @gsearch_regex => ["whoogle"],
-    @fandom_regex => ["breezewiki"],
-    @github_regex => ["gothub"],
-    @stackoverflow_regex => ["anonymousoverflow"]
-  }
-
-  def get_services_map do
-    service_list = CubDB.select(CubDB)
-                   |> Stream.map(fn {key, _value} -> key end)
-                   |> Stream.filter(fn key -> String.starts_with?(key, @service_prefix) end)
-                   |> Enum.to_list
-
-    # Match service name to list of available instances
-    Enum.reduce(service_list, %{}, fn service, acc ->
-      instance_list = CubDB.get(CubDB, service)
-
-      Map.put(
-        acc,
-        String.replace_prefix(
-          service,
-          @service_prefix,
-          ""
-        ),
-        instance_list
-      )
-    end)
-  end
-
-  def get_service(service) do
-    # Check if service has an entry in the db, otherwise try to
-    # match against available parent services
-    service_name = cond do
-      !check_service(service) ->
-        Enum.find_value(
-          @parent_services,
-          fn {k, v} ->
-            String.match?(service, k) && Enum.random(v)
-          end)
-      true ->
-        service
-    end
-
-    service_name
-  end
-
-  def check_service(service) do
-    # Checks to see if a specific service has instances available
-    instances = CubDB.get(CubDB, "#{@service_prefix}#{service}")
-
-    instances != nil && Enum.count(instances) > 0
-  end
-
-  def last_instance(service) do
-    # Fetches the last selected instance for a particular service
-    CubDB.get(CubDB, "#{service}#{@previous_suffix}")
-  end
-
-  def pick_instance(service) do
-    instances = CubDB.get(CubDB, "#{@service_prefix}#{service}")
-
-    # Either pick a random available instance,
-    # or fall back to the default one
-    instance =
-      if instances != nil && Enum.count(instances) > 0 do
-        if Enum.count(instances) == 1 do
-          # If there's only one instance, just return that one...
-          List.first(instances)
-        else
-          # ...otherwise pick a random one from the list, ensuring
-          # that the same instance is never picked twice in a row.
-          instance =
-            Enum.filter(instances, &(&1 != last_instance(service)))
-            |> Enum.random()
-
-          CubDB.put(CubDB, "#{service}#{@previous_suffix}", instance)
-
-          instance
-        end
-      else
-        CubDB.get(CubDB, "#{service}#{@fallback_suffix}")
-      end
-    instance
-  end
-
-  def amend_instance(instance, service, path) do
-    cond do
-      String.match?(service, @fandom_regex) ->
-        # Fandom links require the subdomain to be preserved, otherwise the
-        # requested path won't work.
-        if String.contains?(service, ".fandom.com") do
-          wiki = String.replace(service, ".fandom.com", "")
-          "#{instance}/#{wiki}"
-        else
-          instance
-        end
-      true ->
-        instance
-    end
-  end
-
-  def get_last_updated do
-    CubDB.get(CubDB, "last_updated")
-  end
-end
diff --git a/lib/farside/application.ex b/lib/farside/application.ex
deleted file mode 100644
index 0f11f73..0000000
--- a/lib/farside/application.ex
+++ /dev/null
@@ -1,29 +0,0 @@
-defmodule Farside.Application do
-  @moduledoc false
-
-  use Application
-
-  @impl true
-  def start(_type, _args) do
-    farside_port = Application.fetch_env!(:farside, :port)
-    data_dir = Application.fetch_env!(:farside, :data_dir)
-    IO.puts "Running on http://localhost:#{farside_port}"
-
-    children = [
-      Plug.Cowboy.child_spec(
-        scheme: :http,
-        plug: Farside.Router,
-        options: [
-          port: String.to_integer(farside_port)
-        ]
-      ),
-      {PlugAttack.Storage.Ets, name: Farside.Throttle.Storage, clean_period: 60_000},
-      {CubDB, [data_dir: data_dir, name: CubDB, auto_compact: true]},
-      Farside.Scheduler,
-      Farside.Server
-    ]
-
-    opts = [strategy: :one_for_one, name: Farside.Supervisor]
-    Supervisor.start_link(children, opts)
-  end
-end
diff --git a/lib/farside/instances.ex b/lib/farside/instances.ex
deleted file mode 100644
index d0d26f6..0000000
--- a/lib/farside/instances.ex
+++ /dev/null
@@ -1,134 +0,0 @@
-defmodule Farside.Instances do
-  @fallback_suffix Application.fetch_env!(:farside, :fallback_suffix)
-  @update_file Application.fetch_env!(:farside, :update_file)
-  @service_prefix Application.fetch_env!(:farside, :service_prefix)
-  @headers Application.fetch_env!(:farside, :headers)
-  @queries Application.fetch_env!(:farside, :queries)
-  @debug_header "======== "
-  @debug_spacer "         "
-
-  # These instance uptimes are inspected as part of the nightly Farside build,
-  # and should not be included in the constant periodic update.
-  @skip_service_updates ["searxng", "nitter"]
-
-  def sync() do
-    File.rename(@update_file, "#{@update_file}-prev")
-    update()
-
-    # Add UTC time of last update
-    CubDB.put(CubDB, "last_updated", Calendar.strftime(DateTime.utc_now(), "%c"))
-  end
-
-  def request(url) do
-    IO.puts("#{@debug_spacer}#{url}")
-
-    cond do
-      System.get_env("FARSIDE_TEST") ->
-        :good
-
-      true ->
-        HTTPoison.get(url, @headers)
-        |> then(&elem(&1, 1))
-        |> Map.get(:status_code)
-        |> case do
-          n when n < 300 ->
-            IO.puts("#{@debug_spacer}✓ [#{n}]")
-            :good
-
-          n ->
-            IO.puts("#{@debug_spacer}x [#{(n && n) || "error"}]")
-            :bad
-        end
-    end
-  end
-
-  def update() do
-    services_json = Application.fetch_env!(:farside, :services_json)
-    {:ok, file} = File.read(services_json)
-    {:ok, json} = Jason.decode(file)
-
-    # Loop through all instances and check each for availability
-    for service_json <- json do
-      service_atom = for {key, val} <- service_json, into: %{} do
-        {String.to_existing_atom(key), val}
-      end
-
-      service = struct(%Service{}, service_atom)
-
-      IO.puts("#{@debug_header}#{service.type}")
-
-      result = cond do
-        Enum.member?(@skip_service_updates, service.type) ->
-          get_service_vals(service.instances)
-        true ->
-          Enum.filter(service.instances, fn instance_url ->
-            test_url = get_test_val(instance_url)
-            test_path = get_test_val(service.test_url)
-            test_request_url = gen_validation_url(test_url, test_path)
-
-            service_url = get_service_val(instance_url)
-            service_path = get_service_val(service.test_url)
-            service_request_url = gen_validation_url(service_url, service_path)
-
-            cond do
-              service_url != test_url ->
-                service_up = request(service_request_url)
-                test_up = request(test_request_url)
-
-                service_up == :good && test_up == :good
-              true ->
-                request(test_request_url) == :good
-            end
-          end)
-      end
-
-      add_to_db(service, result)
-      log_results(service.type, result)
-    end
-  end
-
-  def add_to_db(service, instances) do
-    # Ensure only service URLs are inserted, not test URLs (separated by "|")
-    instances = get_service_vals(instances)
-
-    # Remove previous list of instances
-    CubDB.delete(CubDB, "#{@service_prefix}#{service.type}")
-
-    # Update with new list of available instances
-    CubDB.put(CubDB, "#{@service_prefix}#{service.type}", instances)
-
-    # Set fallback to one of the available instances,
-    # or the default instance if all are "down"
-    if Enum.count(instances) > 0 do
-      CubDB.put(CubDB, "#{service.type}#{@fallback_suffix}", Enum.random(instances))
-    else
-      CubDB.put(CubDB, "#{service.type}#{@fallback_suffix}", service.fallback)
-    end
-  end
-
-  def log_results(service_name, results) do
-    {:ok, file} = File.open(@update_file, [:append, {:delayed_write, 100, 20}])
-    IO.write(file, "#{service_name}: #{inspect(results)}\n")
-    File.close(file)
-  end
-
-  def gen_validation_url(url, path) do
-    url <> EEx.eval_string(path, query: Enum.random(@queries))
-  end
-
-  def get_service_vals(services) do
-    Enum.map(services, fn x -> get_service_val(x) end)
-  end
-
-  def get_service_val(service) do
-    String.split(service, "|") |> List.first
-  end
-
-  def get_test_vals(services) do
-    Enum.map(services, fn x -> get_test_val(x) end)
-  end
-
-  def get_test_val(service) do
-    String.split(service, "|") |> List.last
-  end
-end
diff --git a/lib/farside/router.ex b/lib/farside/router.ex
deleted file mode 100644
index ec49862..0000000
--- a/lib/farside/router.ex
+++ /dev/null
@@ -1,78 +0,0 @@
-defmodule Farside.Router do
-  @index Application.fetch_env!(:farside, :index)
-  @route Application.fetch_env!(:farside, :route)
-
-  use Plug.Router
-
-  plug(RemoteIp)
-  plug(Farside.Throttle)
-  plug(:match)
-  plug(:dispatch)
-
-  def get_query_params(conn) do
-    cond do
-      String.length(conn.query_string) > 0 ->
-        "?#{conn.query_string}"
-
-      true ->
-        ""
-    end
-  end
-
-  match "/" do
-    resp =
-      EEx.eval_file(
-        @index,
-        last_updated: Farside.get_last_updated(),
-        services: Farside.get_services_map()
-      )
-
-    put_resp_header(conn, "content-type", "text/html")
-        |> send_resp(200, resp)
-  end
-
-  match "/_/:service/*glob" do
-    r_path = String.slice(conn.request_path, 2..-1)
-
-    resp =
-      EEx.eval_file(
-        @route,
-        instance_url: "#{r_path}#{get_query_params(conn)}"
-      )
-
-    send_resp(conn, 200, resp)
-  end
-
-  match "/:service/*glob" do
-    service_name = cond do
-      service =~ "http" ->
-        List.first(glob)
-      true ->
-        service
-    end
-
-    path = cond do
-      service_name != service ->
-        Enum.join(Enum.slice(glob, 1..-1), "/")
-      true ->
-        Enum.join(glob, "/")
-    end
-
-    cond do
-      conn.assigns[:throttle] != nil ->
-        send_resp(conn, :too_many_requests, "Too many requests - max request rate is 1 per second")
-      true ->
-        instance = Farside.get_service(service_name)
-            |> Farside.pick_instance
-            |> Farside.amend_instance(service_name, path)
-
-        # Redirect to the available instance
-        conn
-        |> Plug.Conn.resp(:found, "")
-        |> Plug.Conn.put_resp_header(
-          "location",
-          "#{instance}/#{path}#{get_query_params(conn)}"
-        )
-    end
-  end
-end
diff --git a/lib/farside/scheduler.ex b/lib/farside/scheduler.ex
deleted file mode 100644
index 4707624..0000000
--- a/lib/farside/scheduler.ex
+++ /dev/null
@@ -1,3 +0,0 @@
-defmodule Farside.Scheduler do
-  use Quantum, otp_app: :farside
-end
diff --git a/lib/farside/server.ex b/lib/farside/server.ex
deleted file mode 100644
index cdb6682..0000000
--- a/lib/farside/server.ex
+++ /dev/null
@@ -1,25 +0,0 @@
-defmodule Farside.Server do
-  use GenServer
-  import Crontab.CronExpression
-
-  def init(init_arg) do
-    {:ok, init_arg}
-  end
-
-  def start_link(arg) do
-    test = System.get_env("FARSIDE_TEST")
-    cron = System.get_env("FARSIDE_CRON")
-
-    if test == "1" || cron == "0" do
-      IO.puts("Skipping sync job setup...")
-    else
-      Farside.Scheduler.new_job()
-      |> Quantum.Job.set_name(:sync)
-      |> Quantum.Job.set_schedule(~e[*/5 * * * *])
-      |> Quantum.Job.set_task(fn -> Farside.Instances.sync() end)
-      |> Farside.Scheduler.add_job()
-    end
-
-    GenServer.start_link(__MODULE__, arg)
-  end
-end
diff --git a/lib/farside/throttle.ex b/lib/farside/throttle.ex
deleted file mode 100644
index e2561ab..0000000
--- a/lib/farside/throttle.ex
+++ /dev/null
@@ -1,20 +0,0 @@
-defmodule Farside.Throttle do
-  import Plug.Conn
-  use PlugAttack
-
-  rule "throttle per ip", conn do
-    # throttle to 1 request per second
-    throttle(conn.remote_ip,
-      period: 1_000,
-      limit: 1,
-      storage: {PlugAttack.Storage.Ets, Farside.Throttle.Storage}
-    )
-  end
-
-  def allow_action(conn, _data, _opts), do: conn
-
-  def block_action(conn, _data, _opts) do
-    conn = assign(conn, :throttle, 1)
-    conn
-  end
-end
diff --git a/lib/service.ex b/lib/service.ex
deleted file mode 100644
index ae964f6..0000000
--- a/lib/service.ex
+++ /dev/null
@@ -1,6 +0,0 @@
-defmodule Service do
-  defstruct type: nil,
-            test_url: nil,
-            fallback: nil,
-            instances: []
-end