feat: prepare decoding traits and make new Flat trait

crates/cli/src/main.rs

@@ -11,7 +11,7 @@ fn main() -> anyhow::Result<()> {
 
     println!("{:#?}", program);
 
-    let flat_bytes = program.flat()?;
+    let flat_bytes = program.to_flat()?;
 
     for byte in flat_bytes {
         print!("{:08b} ", byte);

crates/flat/src/decode.rs

@@ -0,0 +1,5 @@
+use crate::decoder::Decoder;
+
+pub trait Decode<'b>: Sized {
+    fn decode(d: &mut Decoder<'b>) -> Result<Self, String>;
+}

crates/flat/src/decoder.rs

@@ -0,0 +1,19 @@
+use crate::decode::Decode;
+
+pub struct Decoder<'b> {
+    buffer: &'b [u8],
+    pos: usize,
+}
+
+impl<'b> Decoder<'b> {
+    pub fn new(bytes: &'b [u8]) -> Decoder<'b> {
+        Decoder {
+            buffer: bytes,
+            pos: 0,
+        }
+    }
+
+    pub fn decode<T: Decode<'b>>(&mut self) -> Result<T, String> {
+        T::decode(self)
+    }
+}

crates/flat/src/encode.rs

@@ -83,19 +83,6 @@ impl<T: Encode> Encode for Box<T> {
     }
 }
 
-impl<T, K> Encode for (T, K)
-where
-    T: Encode,
-    K: Encode,
-{
-    fn encode(&self, e: &mut Encoder) -> Result<(), String> {
-        self.0.encode(e)?;
-        self.1.encode(e)?;
-
-        Ok(())
-    }
-}
-
 impl Encode for Filler {
     fn encode(&self, e: &mut Encoder) -> Result<(), String> {
         e.filler();

crates/flat/src/lib.rs

@@ -1,3 +1,5 @@
+mod decode;
+mod decoder;
 mod encode;
 mod encoder;
 mod filler;
@@ -8,33 +10,58 @@ pub mod en {
     pub use super::encoder::*;
 }
 
-pub fn encode<T>(value: T) -> Result<Vec<u8>, String>
+pub mod de {
+    pub use super::decode::*;
+    pub use super::decoder::*;
+}
+
+pub trait Flat<'b>: en::Encode + de::Decode<'b> {
+    fn flat(&self) -> Result<Vec<u8>, String> {
+        encode(self)
+    }
+
+    fn unflat(bytes: &'b [u8]) -> Result<Self, String> {
+        decode(bytes)
+    }
+}
+
+pub fn encode<T>(value: &T) -> Result<Vec<u8>, String>
 where
     T: en::Encode,
 {
     let mut e = en::Encoder::new();
 
-    e.encode((value, filler::Filler::FillerEnd))?;
+    value.encode(&mut e)?;
+    e.encode(filler::Filler::FillerEnd)?;
 
     Ok(e.buffer)
 }
 
+pub fn decode<'b, T>(bytes: &'b [u8]) -> Result<T, String>
+where
+    T: de::Decode<'b>,
+{
+    let mut d = de::Decoder::new(bytes);
+
+    d.decode()
+}
+
 #[cfg(test)]
 mod test {
     #[test]
     fn encode_bool() {
-        let bytes = super::encode(true).unwrap();
+        let bytes = super::encode(&true).unwrap();
 
         assert_eq!(bytes, vec![0b10000001]);
 
-        let bytes = super::encode(false).unwrap();
+        let bytes = super::encode(&false).unwrap();
 
         assert_eq!(bytes, vec![0b00000001]);
     }
 
     #[test]
     fn encode_u8() {
-        let bytes = super::encode(3_u8).unwrap();
+        let bytes = super::encode(&3_u8).unwrap();
 
         assert_eq!(bytes, vec![0b00000011, 0b00000001]);
     }

crates/uplc/src/flat.rs

@@ -1,6 +1,10 @@
 use anyhow::anyhow;
 
-use flat::en::{Encode, Encoder};
+use flat::{
+    de::{Decode, Decoder},
+    en::{Encode, Encoder},
+    Flat,
+};
 
 use crate::{
     ast::{Constant, Program, Term},
@@ -11,15 +15,17 @@ const BUILTIN_TAG_WIDTH: u32 = 7;
 const CONST_TAG_WIDTH: u32 = 4;
 const TERM_TAG_WIDTH: u32 = 4;
 
-impl Program {
-    pub fn flat(&self) -> anyhow::Result<Vec<u8>> {
-        let bytes = flat::encode(self.clone()).map_err(|err| anyhow!("{}", err))?;
+impl<'b> Flat<'b> for Program {}
 
-        Ok(bytes)
+impl Program {
+    // convenient so that people don't need to depend on the flat crate
+    // directly to call programs flat function
+    pub fn to_flat(&self) -> anyhow::Result<Vec<u8>> {
+        self.flat().map_err(|err| anyhow!("{}", err))
     }
 
     pub fn flat_hex(&self) -> anyhow::Result<String> {
-        let bytes = self.flat()?;
+        let bytes = self.flat().map_err(|err| anyhow!("{}", err))?;
 
         let hex = hex::encode(&bytes);
 
@@ -41,6 +47,12 @@ impl Encode for Program {
     }
 }
 
+impl<'b> Decode<'b> for Program {
+    fn decode(_d: &mut Decoder<'b>) -> Result<Self, String> {
+        todo!()
+    }
+}
+
 impl Encode for Term {
     fn encode(&self, e: &mut Encoder) -> Result<(), String> {
         // still need annotation but here we have the term tags
@@ -92,6 +104,12 @@ impl Encode for Term {
     }
 }
 
+impl<'b> Decode<'b> for Term {
+    fn decode(_d: &mut Decoder<'b>) -> Result<Self, String> {
+        todo!()
+    }
+}
+
 impl Encode for &Constant {
     fn encode(&self, e: &mut Encoder) -> Result<(), String> {
         match self {
@@ -128,6 +146,12 @@ impl Encode for &Constant {
     }
 }
 
+impl<'b> Decode<'b> for Constant {
+    fn decode(_d: &mut Decoder<'b>) -> Result<Self, String> {
+        todo!()
+    }
+}
+
 impl Encode for DefaultFunction {
     fn encode(&self, e: &mut flat::en::Encoder) -> Result<(), String> {
         e.bits(BUILTIN_TAG_WIDTH as i64, self.clone() as u8);
@@ -136,6 +160,12 @@ impl Encode for DefaultFunction {
     }
 }
 
+impl<'b> Decode<'b> for DefaultFunction {
+    fn decode(_d: &mut Decoder<'b>) -> Result<Self, String> {
+        todo!()
+    }
+}
+
 fn encode_term_tag(tag: u8, e: &mut Encoder) -> Result<(), String> {
     safe_encode_bits(TERM_TAG_WIDTH, tag, e)
 }
@@ -171,7 +201,7 @@ mod test {
             term: Term::Constant(Constant::Integer(11)),
         };
 
-        let bytes = program.flat().unwrap();
+        let bytes = program.to_flat().unwrap();
 
         assert_eq!(
             bytes,