feat: initial proof of concept

.formatter.exs

···
 # Used by "mix format"
 [
-  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"],
+  import_deps: [:typedstruct]
 ]

lib/drinkup.ex

···
-defmodule Drinkup do
-  @moduledoc """
-  Documentation for `Drinkup`.
-  """
+defmodule Drinkup.Firehose do
+  alias Drinkup.Firehose
+  require Logger
 
-  @doc """
-  Hello world.
+  use WebSockex
 
-  ## Examples
+  @default_host "https://bsky.network"
 
-      iex> Drinkup.hello()
-      :world
+  @op_regular 1
+  @op_error -1
 
-  """
-  def hello do
-    :world
+  # TODO: switch to Gun and GenServer?
+
+  def start_link(opts \\ []) do
+    opts = Keyword.validate!(opts, host: @default_host)
+    host = Keyword.get(opts, :host)
+    cursor = Keyword.get(opts, :cursor)
+
+    url =
+      "#{host}/xrpc/com.atproto.sync.subscribeRepos"
+      |> URI.new!()
+      |> URI.append_query(URI.encode_query(%{cursor: cursor}))
+      |> URI.to_string()
+
+    WebSockex.start_link(url, __MODULE__, %{cursor: cursor})
   end
+
+  def handle_connect(conn, state) do
+    Logger.info("Connected to Firehose at #{conn.host}#{conn.path}")
+    {:ok, state}
+  end
+
+  def handle_frame({:binary, msg}, state) do
+    with {:ok, header, next} <- CAR.DagCbor.decode(msg),
+         {:ok, payload, _} <- CAR.DagCbor.decode(next),
+         {%{"op" => @op_regular, "t" => type}, _} <- {header, payload},
+         message <- from_payload(type, payload) do
+      case message do
+        %Firehose.Commit{} = commit ->
+          IO.inspect(commit.ops, label: commit.repo)
+
+        msg ->
+          IO.inspect(msg)
+      end
+    else
+      {%{"op" => @op_error, "t" => type}, payload} ->
+        Logger.error("Got error from Firehose: #{inspect({type, payload})}")
+
+      {:error, reason} ->
+        Logger.warning("Failed to decode frame from Firehose: #{inspect(reason)}")
+    end
+
+    {:ok, state}
+  end
+
+  def handle_frame({:text, msg}, state) do
+    Logger.warning("Got unexpected text frame from Firehose #{inspect(msg)}")
+    {:ok, state}
+  end
+
+  @spec from_payload(String.t(), map()) ::
+          Firehose.Commit.t()
+          | Firehose.Sync.t()
+          | Firehose.Identity.t()
+          | Firehose.Account.t()
+          | Firehose.Info.t()
+          | nil
+  def from_payload("#commit", payload), do: Firehose.Commit.from(payload)
+  def from_payload("#sync", payload), do: Firehose.Sync.from(payload)
+  def from_payload("#identity", payload), do: Firehose.Identity.from(payload)
+  def from_payload("#account", payload), do: Firehose.Account.from(payload)
+  def from_payload("#info", payload), do: Firehose.Info.from(payload)
+  def from_payload(_type, _payload), do: nil
 end

lib/firehose/account.ex

···
+defmodule Drinkup.Firehose.Account do
+  @moduledoc """
+  Struct for account events from the ATProto Firehose.
+  """
+
+  use TypedStruct
+
+  @type status() ::
+          :takendown
+          | :suspended
+          | :deleted
+          | :deactivated
+          | :desynchronized
+          | :throttled
+          | String.t()
+
+  typedstruct enforce: true do
+    field :seq, integer()
+    field :did, String.t()
+    field :time, NaiveDateTime.t()
+    field :active, bool()
+    field :status, status(), enforce: false
+  end
+
+  @spec from(map()) :: t()
+  def from(%{"seq" => seq, "did" => did, "time" => time, "active" => active} = msg) do
+    status = recognise_status(Map.get(msg, "status"))
+    time = NaiveDateTime.from_iso8601!(time)
+
+    %__MODULE__{
+      seq: seq,
+      did: did,
+      time: time,
+      active: active,
+      status: status
+    }
+  end
+
+  @spec recognise_status(String.t()) :: status()
+  defp recognise_status(status)
+       when status in [
+              "takendown",
+              "suspended",
+              "deleted",
+              "deactivated",
+              "desynchronized",
+              "throttled"
+            ],
+       do: String.to_atom(status)
+
+  defp recognise_status(status) when is_binary(status), do: status
+  defp recognise_status(nil), do: nil
+end

lib/firehose/commit.ex

···
+defmodule Drinkup.Firehose.Commit do
+  @moduledoc """
+  Struct for commit events from the ATProto Firehose.
+  """
+
+  # TODO: see atp specs
+  @type tid() :: String.t()
+
+  alias __MODULE__.RepoOp
+  use TypedStruct
+
+  typedstruct enforce: true do
+    field :seq, integer()
+    # DEPCREATED
+    field :rebase, bool()
+    # DEPRECATED
+    field :too_big, bool()
+    field :repo, String.t()
+    field :commit, binary()
+    field :rev, tid()
+    field :since, tid() | nil
+    field :blocks, CAR.Archive.t()
+    field :ops, list(RepoOp.t())
+    # DEPRECATED
+    field :blobs, list(binary())
+    field :prev_data, binary(), enforce: nil
+    field :time, NaiveDateTime.t()
+  end
+
+  @spec from(map()) :: t()
+  def from(
+        %{
+          "seq" => seq,
+          "rebase" => rebase,
+          "tooBig" => too_big,
+          "repo" => repo,
+          "commit" => commit,
+          "rev" => rev,
+          "since" => since,
+          "blocks" => %CBOR.Tag{value: blocks},
+          "ops" => ops,
+          "blobs" => blobs,
+          "time" => time
+        } = msg
+      ) do
+    prev_data =
+      Map.get(msg, "prevData")
+
+    time = NaiveDateTime.from_iso8601!(time)
+    {:ok, blocks} = CAR.decode(blocks)
+
+    %__MODULE__{
+      seq: seq,
+      rebase: rebase,
+      too_big: too_big,
+      repo: repo,
+      commit: commit,
+      rev: rev,
+      since: since,
+      blocks: blocks,
+      ops: Enum.map(ops, &RepoOp.from(&1, blocks)),
+      blobs: blobs,
+      prev_data: prev_data,
+      time: time
+    }
+  end
+
+  defmodule RepoOp do
+    typedstruct enforce: true do
+      @type action() :: :create | :update | :delete | String.t()
+
+      field :action, action()
+      field :path, String.t()
+      field :cid, binary()
+      field :prev, binary(), enforce: false
+      field :record, map() | nil
+    end
+
+    @spec from(map(), CAR.Archive.t()) :: t()
+    def from(%{"action" => action, "path" => path, "cid" => cid} = op, %CAR.Archive{} = blocks) do
+      prev = Map.get(op, "prev")
+      record = CAR.Archive.get_block(blocks, cid)
+
+      %__MODULE__{
+        action: recognise_action(action),
+        path: path,
+        cid: cid,
+        prev: prev,
+        record: record
+      }
+    end
+
+    @spec recognise_action(String.t()) :: action()
+    defp recognise_action(action) when action in ["create", "update", "delete"],
+      do: String.to_atom(action)
+
+    defp recognise_action(action) when is_binary(action), do: action
+    defp recognise_action(nil), do: nil
+  end
+end

lib/firehose/identity.ex

···
+defmodule Drinkup.Firehose.Identity do
+  @moduledoc """
+  Struct for identity events from the ATProto Firehose.
+  """
+
+  use TypedStruct
+
+  typedstruct enforce: true do
+    field :seq, integer()
+    field :did, String.t()
+    field :time, NaiveDateTime.t()
+    field :handle, String.t() | nil
+  end
+
+  @spec from(map()) :: t()
+  def from(%{"seq" => seq, "did" => did, "time" => time} = msg) do
+    handle = Map.get(msg, "handle")
+    time = NaiveDateTime.from_iso8601!(time)
+
+    %__MODULE__{
+      seq: seq,
+      did: did,
+      time: time,
+      handle: handle
+    }
+  end
+end

lib/firehose/info.ex

···
+defmodule Drinkup.Firehose.Info do
+  @moduledoc """
+  Struct for info events from the ATProto Firehose.
+  """
+
+  use TypedStruct
+
+  typedstruct enforce: true do
+    field :name, String.t()
+    field :message, String.t() | nil
+  end
+
+  @spec from(map()) :: t()
+  def from(%{"name" => name} = msg) do
+    message = Map.get(msg, "message")
+
+    %__MODULE__{
+      name: name,
+      message: message
+    }
+  end
+end

lib/firehose/sync.ex

···
+defmodule Drinkup.Firehose.Sync do
+  @moduledoc """
+  Struct for sync events from the ATProto Firehose.
+  """
+
+  use TypedStruct
+
+  typedstruct enforce: true do
+    field :seq, integer()
+    field :did, String.t()
+    field :blocks, binary()
+    field :rev, String.t()
+    field :time, NaiveDateTime.t()
+  end
+
+  @spec from(map()) :: t()
+  def from(%{"seq" => seq, "did" => did, "blocks" => blocks, "rev" => rev, "time" => time}) do
+    time = NaiveDateTime.from_iso8601!(time)
+
+    %__MODULE__{
+      seq: seq,
+      did: did,
+      blocks: blocks,
+      rev: rev,
+      time: time
+    }
+  end
+end

mix.exs

···
   # Run "mix help deps" to learn about dependencies.
   defp deps do
     [
-      # {:dep_from_hexpm, "~> 0.3.0"},
-      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+      {:cbor, "~> 1.0.0"},
+      {:car, "~> 0.1.0"},
+      {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
+      {:typedstruct, "~> 0.5"},
+      {:websockex, "~> 0.5.0", hex: :websockex_wt}
     ]
   end
 end

mix.lock

···
+%{
+  "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},
+  "car": {:hex, :car, "0.1.1", "a5bc4c5c1be96eab437634b3c0ccad1fe17b5e3d68c22a4031241ae1345aebd4", [:mix], [{:cbor, "~> 1.0.0", [hex: :cbor, repo: "hexpm", optional: false]}, {:typedstruct, "~> 0.5", [hex: :typedstruct, repo: "hexpm", optional: false]}, {:varint, "~> 1.4", [hex: :varint, repo: "hexpm", optional: false]}], "hexpm", "f895dda8123d04dd336db5a2bf0d0b47f4559cd5383f83fcca0700c1b45bfb6a"},
+  "cbor": {:hex, :cbor, "1.0.1", "39511158e8ea5a57c1fcb9639aaa7efde67129678fee49ebbda780f6f24959b0", [:mix], [], "hexpm", "5431acbe7a7908f17f6a9cd43311002836a34a8ab01876918d8cfb709cd8b6a2"},
+  "credo": {:hex, :credo, "1.7.12", "9e3c20463de4b5f3f23721527fcaf16722ec815e70ff6c60b86412c695d426c1", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "8493d45c656c5427d9c729235b99d498bd133421f3e0a683e5c1b561471291e5"},
+  "file_system": {:hex, :file_system, "1.1.0", "08d232062284546c6c34426997dd7ef6ec9f8bbd090eb91780283c9016840e8f", [:mix], [], "hexpm", "bfcf81244f416871f2a2e15c1b515287faa5db9c6bcf290222206d120b3d43f6"},
+  "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
+  "telemetry": {:hex, :telemetry, "1.3.0", "fedebbae410d715cf8e7062c96a1ef32ec22e764197f70cda73d82778d61e7a2", [:rebar3], [], "hexpm", "7015fc8919dbe63764f4b4b87a95b7c0996bd539e0d499be6ec9d7f3875b79e6"},
+  "typedstruct": {:hex, :typedstruct, "0.5.3", "d68ae424251a41b81a8d0c485328ab48edbd3858f3565bbdac21b43c056fc9b4", [:make, :mix], [], "hexpm", "b53b8186701417c0b2782bf02a2db5524f879b8488f91d1d83b97d84c2943432"},
+  "varint": {:hex, :varint, "1.5.1", "17160c70d0428c3f8a7585e182468cac10bbf165c2360cf2328aaa39d3fb1795", [:mix], [], "hexpm", "24f3deb61e91cb988056de79d06f01161dd01be5e0acae61d8d936a552f1be73"},
+  "websockex": {:hex, :websockex_wt, "0.5.0", "8725b3bc741e7a682c21310610d033f0aaeedfb3238d9c8d5522c345c04f3f93", [:mix], [{:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "f854a5e7dbd61e852ee74565d862d606e884425c8867ddaa49c8a6c6f43d832a"},
+}