docs: update README to reflect the trafix-codec-v0.1.0 milestone

README.md

@@ -1,3 +1,88 @@
-# trafix
+# Project Structure
 
-A Rust-based implementation of the Financial Information eXchange (FIX) engine featuring 2 subcrates: trafix-codec: Low-level library for high-performance parsing, encoding, and validation of FIX messages. trafix-engine: Full-featured FIX engine with session management, transports, and persistence built on top of trafix-codec.
+This project is organized as a multirepo, consisting of multiple underlying crates, some of which are:
+
+- **trafix** — an umbrella crate wrapping the 2 below.
+- **trafix-codec** — a low-level library for high-performance parsing, encoding, and validation of FIX messages.  
+- **trafix-engine** — a full-featured FIX engine with session management, transports, and persistence built on top of `trafix-codec`.
+
+## trafix-codec
+
+**trafix-codec** is the foundation crate: it provides control over FIX messages manipulation.
+
+### Key Features
+
+- **Message creation**: Version-agnostic FIX message creation using a type-safe builder.
+  - Type-safe builder for `Message`.
+  - Allows custom fields.
+  - Prevents construction of invalid `Message`s.
+
+- **Message decoding**: Version-agnostic FIX message decoding with a focus on correctness.
+  - SOH-based frame parsing (`tag=value\x01`)
+  - Support for FIX session-level messages
+  - Support for message validation
+
+- **Message encoding**: Deterministic FIX message serialization with automatic framing.
+  - Correct handling of `BeginString (8)`, `BodyLength (9)`, and `CheckSum (10)`
+  - Supports arbitrary field order while enforcing FIX wire rules
+  - Efficient buffer-based encoding using (`Bytes` / `BytesMut`)
+
+---
+
+### Example: full usage
+
+```rust
+use trafix_codec::message::{
+    Message,
+    field::{
+        Field,
+        value::{begin_string::BeginString, msg_type::MsgType},
+    },
+};
+
+fn main() {
+    // Create the FIX message builder
+    let builder = Message::builder(BeginString::FIX44, MsgType::Logout);
+
+    // Create a custom field (to be added in header)
+    let custom_header_field = Field::Custom {
+        tag: 22,
+        value: b"custom_header_field".to_vec(),
+    };
+
+    // Create a custom field (to be added in body)
+    let custom_body_field1 = Field::Custom {
+        tag: 40000,
+        value: b"custom_body_field1".to_vec(),
+    };
+
+    // Create a custom field (to be added in body)
+    let custom_body_field2 = Field::Custom {
+        tag: 50000,
+        value: b"custom_body_field2".to_vec(),
+    };
+
+    // build the message after adding the needed fields.
+    let message = builder
+        .with_header(custom_header_field)
+        .with_field(custom_body_field1)
+        .with_field(custom_body_field2)
+        .build();
+
+    // encode the message into bytes
+    let encoded_message = message.encode();
+    println!("{:?}", encoded_message);
+
+    // decoding example; decoding and encoding a message results in the same bytes output.
+
+    // Raw FIX message
+    let input = "8=FIX.4.4\x019=148\x0135=A\x0134=1080\x0149=TESTBUY1\x0152=20180920-18:14:19.508\x0156=TESTSELL1\x0111=636730640278898634\x0115=USD\x0121=2\x0138=7000\x0140=1\x0154=1\x0155=MSFT\x0160=20180920-18:14:19.492\x0110=089\x01";
+
+    // decode the input
+    let message2 = Message::decode(input).expect("Input is valid");
+
+    // encode the message into bytes
+    let encoded_message2 = message2.encode();
+    println!("{:?}", encoded_message2);
+}
+```