README.md

@@ -10,6 +10,14 @@ See the [SSB Binary Field Encodings Specification](https://github.com/ssbc/ssb-b
 SsbBfe.encode(value)
 ```
 
+## Decoding
+
+```elixir
+SsbBfe.decode(value)
+```
+
+## Supported Types
+
 ### Elixir Types
 
 Encoding of the following Elixir types is supported:

lib/ssb_bfe.ex

@@ -16,6 +16,8 @@ defmodule SsbBfe do
     :world
   end
 
+  # ENCODE
+
   def encode(value) when is_list(value) do
     Enum.map(value, fn x -> encode(x) end)
   end
@@ -31,7 +33,8 @@ defmodule SsbBfe do
   end
 
   def encode(value) when is_tuple(value) do
-    Enum.map(Tuple.to_list(value), fn x -> encode(x) end)
+    Enum.map(Tuple.to_list(value), fn x -> encode(x) end) |>
+    List.to_tuple()
   end
 
   def encode(value) when is_bitstring(value) do
@@ -61,4 +64,54 @@ defmodule SsbBfe do
   def encode(value) when is_number(value), do: value
 
   def encode(value) when is_nil(value), do: SsbBfe.Encoder.encode_nil()
+
+  # DECODE
+
+  def decode(value) when is_binary(value) do
+    first_byte = :binary.first(value)
+
+    cond do
+      0 == first_byte ->
+        SsbBfe.Decoder.decode_feed(value)
+
+      1 == first_byte ->
+        SsbBfe.Decoder.decode_msg(value)
+
+      2 == first_byte ->
+        SsbBfe.Decoder.decode_blob(value)
+
+      4 == first_byte ->
+        SsbBfe.Decoder.decode_sig(value)
+
+      5 == first_byte ->
+        SsbBfe.Decoder.decode_box(value)
+
+      6 == first_byte ->
+        SsbBfe.Decoder.decode_generic(value)
+
+      nil ->
+        true
+    end
+  end
+
+  def decode(value) when is_number(value), do: value
+
+  def decode(value) when is_list(value) do
+    Enum.map(value, fn x -> decode(x) end)
+  end
+
+  def decode(value) when is_map(value) do
+    Enum.reduce(
+      value,
+      %{},
+      fn {k, v}, acc ->
+        Map.put(acc, k, SsbBfe.decode(v))
+      end
+    )
+  end
+
+  def decode(value) when is_tuple(value) do
+    Enum.map(Tuple.to_list(value), fn x -> decode(x) end) |>
+    List.to_tuple()
+  end
 end

lib/ssb_bfe/decoder.ex

@@ -0,0 +1,75 @@
+defmodule SsbBfe.Decoder do
+  defp extract_base64_data(bin, tf_tag) do
+    [_, base64_data] = :binary.split(bin, tf_tag)
+    Base.encode64(base64_data)
+  end
+
+  def decode_blob(blob) do
+    encoded_base64_data = extract_base64_data(blob, <<2, 0>>)
+    "&" <> encoded_base64_data <> ".sha256"
+  end
+
+  def decode_box(box) do
+    tf_tag = binary_part(box, 0, 2)
+    decode_box(box, tf_tag)
+  end
+
+  # Matches box.
+  def decode_box(box, <<5, 0>>) do
+    encoded_base64_data = extract_base64_data(box, <<5, 0>>)
+    encoded_base64_data <> ".box"
+  end
+
+  # Matches box2.
+  def decode_box(box, <<5, 1>>) do
+    encoded_base64_data = extract_base64_data(box, <<5, 1>>)
+    encoded_base64_data <> ".box2"
+  end
+
+  def decode_feed(feed) do
+    tf_tag = binary_part(feed, 0, 2)
+    decode_feed(feed, tf_tag)
+  end
+
+  # Matches classic feed.
+  def decode_feed(feed, <<0, 0>>) do
+    encoded_base64_data = extract_base64_data(feed, <<0, 0>>)
+    "@" <> encoded_base64_data <> ".ed25519"
+  end
+
+  def decode_generic(<<6, 1, 1>>), do: true
+
+  def decode_generic(<<6, 1, 0>>), do: false
+
+  def decode_generic(<<6, 2>>), do: nil
+
+  def decode_generic(generic) do
+    tf_tag = binary_part(generic, 0, 2)
+    decode_generic(generic, tf_tag)
+  end
+
+  # Matches generic string.
+  def decode_generic(str, <<6, 0>>) do
+    [_, str_data] = :binary.split(str, <<6, 0>>)
+    str_data
+  end
+
+  # Matches generic bytes.
+  def decode_generic(bytes, <<6, 3>>), do: bytes
+
+  def decode_msg(msg) do
+    tf_tag = binary_part(msg, 0, 2)
+    decode_msg(msg, tf_tag)
+  end
+
+  # Matches classic message.
+  def decode_msg(msg, <<1, 0>>) do
+    encoded_base64_data = extract_base64_data(msg, <<1, 0>>)
+    "%" <> encoded_base64_data <> ".sha256"
+  end
+
+  def decode_sig(sig) do
+    encoded_base64_data = extract_base64_data(sig, <<4, 0>>)
+    encoded_base64_data <> ".sig.ed25519"
+  end
+end

lib/ssb_bfe/encoder.ex

@@ -1,6 +1,3 @@
-# might be good to use a multiclause function for the `encode` function
-# - use the `when` conditional guard with e.g. `is_number` 
-
 defmodule SsbBfe.Encoder do
   # Extract the base64 substring from a sigil-link and decode it.
   defp extract_base64_data(str) do

test/ssb_bfe_test.exs

@@ -5,88 +5,174 @@ defmodule SsbBfeTest do
   setup do
     [
       blob: "&S7+CwHM6dZ9si5Vn4ftpk/l/ldbRMqzzJos+spZbWf4=.sha256",
+      blob_encoded: <<2, 0, 75, 191, 130, 192, 115, 58, 117, 159, 108, 139, 149, 103, 225, 251, 105, 147, 249, 127, 149, 214, 209, 50, 172, 243, 38, 139, 62, 178, 150, 91, 89, 254>>,
+      bool_true_encoded: <<6, 1, 1>>,
+      bool_false_encoded: <<6, 1, 0>>,
       box1: "bG92ZSBjb2xsYXBzZXMgc3BhY2V0aW1l.box",
+      box1_encoded: <<5, 0, 108, 111, 118, 101, 32, 99, 111, 108, 108, 97, 112, 115, 101, 115, 32, 115, 112, 97, 99, 101, 116, 105, 109, 101>>,
       box2: "bG92ZSBjb2xsYXBzZXMgc3BhY2V0aW1l.box2",
+      box2_encoded: <<5, 1, 108, 111, 118, 101, 32, 99, 111, 108, 108, 97, 112, 115, 101, 115, 32, 115, 112, 97, 99, 101, 116, 105, 109, 101>>,
       feed_classic: "@d/zDvFswFbQaYJc03i47C9CgDev+/A8QQSfG5l/SEfw=.ed25519",
+      feed_classic_encoded: <<0, 0, 119, 252, 195, 188, 91, 48, 21, 180, 26, 96, 151, 52, 222, 46, 59, 11, 208, 160, 13, 235, 254, 252, 15, 16, 65, 39, 198, 230, 95, 210, 17, 252>>,
       msg_classic: "%R8heq/tQoxEIPkWf0Kxn1nCm/CsxG2CDpUYnAvdbXY8=.sha256",
+      msg_classic_encoded: <<1, 0, 71, 200, 94, 171, 251, 80, 163, 17, 8, 62, 69, 159, 208, 172, 103, 214, 112, 166, 252, 43, 49, 27, 96, 131, 165, 70, 39, 2, 247, 91, 93, 143>>,
+      nil_encoded: <<6, 2>>,
       sig: "nkY4Wsn9feosxvX7bpLK7OxjdSrw6gSL8sun1n2TMLXKySYK9L5itVQnV2nQUctFsrUOa2istD2vDk1B0uAMBQ==.sig.ed25519",
+      sig_encoded: <<4, 0, 158, 70, 56, 90, 201, 253, 125, 234, 44, 198, 245, 251, 110, 146, 202, 236, 236, 99, 117, 42, 240, 234, 4, 139, 242, 203, 167, 214, 125, 147, 48, 181, 202, 201, 38, 10, 244, 190, 98, 181, 84, 39, 87, 105, 208, 81, 203, 69, 178, 181, 14, 107, 104, 172, 180, 61, 175, 14, 77, 65, 210, 224, 12, 5>>,
       str: "golden ripples in the meshwork",
+      str_encoded: <<6, 0, 103, 111, 108, 100, 101, 110, 32, 114, 105, 112, 112, 108, 101, 115, 32, 105, 110, 32, 116, 104, 101, 32, 109, 101, 115, 104, 119, 111, 114, 107>>
     ]
   end
 
-  # HAPPY PATH ENCODING TESTS
+  # ENCODING TESTS: HAPPY PATH
 
   test "classic feed is encoded correctly", context do
     encoded_feed = SsbBfe.encode(context.feed_classic)
     
-    assert encoded_feed == <<0, 0, 119, 252, 195, 188, 91, 48, 21, 180, 26, 96, 151, 52, 222, 46, 59, 11, 208, 160, 13, 235, 254, 252, 15, 16, 65, 39, 198, 230, 95, 210, 17, 252>>
+    assert encoded_feed == context.feed_classic_encoded
   end
 
   test "classic msg is encoded correctly", context do
     encoded_msg = SsbBfe.encode(context.msg_classic)
 
-    assert encoded_msg == <<1, 0, 71, 200, 94, 171, 251, 80, 163, 17, 8, 62, 69, 159, 208, 172, 103, 214, 112, 166, 252, 43, 49, 27, 96, 131, 165, 70, 39, 2, 247, 91, 93, 143>>
+    assert encoded_msg == context.msg_classic_encoded
   end
 
   test "blob is encoded correctly", context do
     encoded_blob = SsbBfe.encode(context.blob)
 
-    assert encoded_blob == <<2, 0, 75, 191, 130, 192, 115, 58, 117, 159, 108, 139, 149, 103, 225, 251, 105, 147, 249, 127, 149, 214, 209, 50, 172, 243, 38, 139, 62, 178, 150, 91, 89, 254>>
+    assert encoded_blob == context.blob_encoded
   end
 
   test "signature is encoded correctly", context do
     encoded_sig = SsbBfe.encode(context.sig)
 
-    assert encoded_sig == <<4, 0, 158, 70, 56, 90, 201, 253, 125, 234, 44, 198, 245, 251, 110, 146, 202, 236, 236, 99, 117, 42, 240, 234, 4, 139, 242, 203, 167, 214, 125, 147, 48, 181, 202, 201, 38, 10, 244, 190, 98, 181, 84, 39, 87, 105, 208, 81, 203, 69, 178, 181, 14, 107, 104, 172, 180, 61, 175, 14, 77, 65, 210, 224, 12, 5>>
+    assert encoded_sig == context.sig_encoded
   end
 
   test "box is encoded correctly", context do
     encoded_box = SsbBfe.encode(context.box1)
 
-    assert encoded_box == <<5, 0, 108, 111, 118, 101, 32, 99, 111, 108, 108, 97, 112, 115, 101, 115, 32, 115, 112, 97, 99, 101, 116, 105, 109, 101>>
+    assert encoded_box == context.box1_encoded
   end
 
   test "box2 is encoded correctly", context do
     encoded_box2 = SsbBfe.encode(context.box2)
 
-    assert encoded_box2 == <<5, 1, 108, 111, 118, 101, 32, 99, 111, 108, 108, 97, 112, 115, 101, 115, 32, 115, 112, 97, 99, 101, 116, 105, 109, 101>>
+    assert encoded_box2 == context.box2_encoded
   end
 
   test "plain string is encoded correctly", context do
     encoded_str = SsbBfe.encode(context.str)
 
-    assert encoded_str == <<6, 0, 103, 111, 108, 100, 101, 110, 32, 114, 105, 112, 112, 108, 101, 115, 32, 105, 110, 32, 116, 104, 101, 32, 109, 101, 115, 104, 119, 111, 114, 107>>
+    assert encoded_str == context.str_encoded
   end
 
-  test "boolean is encoded correctly" do
+  test "boolean is encoded correctly", context do
     encoded_bool_true = SsbBfe.encode(true)
     encoded_bool_false = SsbBfe.encode(false)
 
-    assert encoded_bool_true == <<6, 1, 1>>
-    assert encoded_bool_false == <<6, 1, 0>>
+    assert encoded_bool_true == context.bool_true_encoded
+    assert encoded_bool_false == context.bool_false_encoded
   end
 
-  test "nil is encoded correctly" do
+  test "nil is encoded correctly", context do
     encoded_nil = SsbBfe.encode(nil)
 
-    assert encoded_nil == <<6, 2>>
+    assert encoded_nil == context.nil_encoded
   end
 
-  test "list is encoded correctly" do
-    encoded_list = SsbBfe.encode([true, nil, "ganoderma"])
+  test "list is encoded correctly", context do
+    encoded_list = SsbBfe.encode([true, nil, context.str])
 
-    assert encoded_list == [<<6, 1, 1>>, <<6, 2>>, <<6, 0, 103, 97, 110, 111, 100, 101, 114, 109, 97>>]
+    assert encoded_list == [context.bool_true_encoded, context.nil_encoded, context.str_encoded]
   end
 
   test "map is encoded correctly", context do
     encoded_map = SsbBfe.encode(%{"bool" => false, "feed" => context.feed_classic})
 
-    assert encoded_map == %{"bool" => <<6, 1, 0>>, "feed" => <<0, 0, 119, 252, 195, 188, 91, 48, 21, 180, 26, 96, 151, 52, 222, 46, 59, 11, 208, 160, 13, 235, 254, 252, 15, 16, 65, 39, 198, 230, 95, 210, 17, 252>>}
+    assert encoded_map == %{"bool" => context.bool_false_encoded, "feed" => context.feed_classic_encoded}
   end
 
   test "tuple is encoded correctly", context do
     encoded_tuple = SsbBfe.encode({7, context.msg_classic})
 
-    assert encoded_tuple == [7, <<1, 0, 71, 200, 94, 171, 251, 80, 163, 17, 8, 62, 69, 159, 208, 172, 103, 214, 112, 166, 252, 43, 49, 27, 96, 131, 165, 70, 39, 2, 247, 91, 93, 143>>]
+    assert encoded_tuple == {7, context.msg_classic_encoded}
+  end
+
+  # DECODING TESTS: HAPPY PATH
+
+  test "classic feed is decoded correctly", context do
+    decoded_feed = SsbBfe.decode(context.feed_classic_encoded)
+
+    assert decoded_feed == context.feed_classic
+  end
+
+  test "classic message is decoded correctly", context do
+    decoded_msg = SsbBfe.decode(context.msg_classic_encoded)
+
+    assert decoded_msg == context.msg_classic
+  end
+
+  test "blob is decoded correctly", context do
+    decoded_blob = SsbBfe.decode(context.blob_encoded)
+
+    assert decoded_blob == context.blob
+  end
+
+  test "signature is decoded correctly", context do
+    decoded_sig = SsbBfe.decode(context.sig_encoded)
+
+    assert decoded_sig == context.sig
+  end
+
+  test "box is decoded correctly", context do
+    decoded_box = SsbBfe.decode(context.box1_encoded)
+
+    assert decoded_box == context.box1
+  end
+  
+  test "box2 is decoded correctly", context do
+    decoded_box2 = SsbBfe.decode(context.box2_encoded)
+
+    assert decoded_box2 == context.box2
+  end
+
+  test "plain string is decoded correctly", context do
+    decoded_str = SsbBfe.decode(context.str_encoded)
+
+    assert decoded_str == context.str
+  end
+
+  test "boolean is decoded correctly", context do
+    decoded_bool_true = SsbBfe.decode(context.bool_true_encoded)
+    decoded_bool_false = SsbBfe.decode(context.bool_false_encoded)
+
+    assert decoded_bool_true == true
+    assert decoded_bool_false == false
+  end
+
+  test "nil string is decoded correctly", context do
+    decoded_nil = SsbBfe.decode(context.nil_encoded)
+
+    assert decoded_nil == nil
+  end
+
+  test "list is decoded correctly", context do
+    decoded_list = SsbBfe.decode([context.bool_true_encoded, context.nil_encoded, context.str_encoded])
+
+    assert decoded_list == [true, nil, context.str]
+  end
+
+  test "map is decoded correctly", context do
+    decoded_map = SsbBfe.decode(%{"bool" => context.bool_false_encoded, "feed" => context.feed_classic_encoded})
+
+    assert decoded_map == %{"bool" => false, "feed" => context.feed_classic}
+  end
+  
+  test "tuple is decoded correctly", context do
+    decoded_tuple = SsbBfe.decode({7, context.msg_classic_encoded})
+
+    assert decoded_tuple == {7, context.msg_classic}
   end
 end