facet_msgpack/

from_msgpack.rs

use crate::constants::*;
use crate::errors::Error as DecodeError;

use facet_core::{Def, Facet};
use facet_reflect::{HeapValue, Wip};
use log::trace;

/// Deserializes MessagePack-encoded data into a type that implements `Facet`.
///
/// # Example
/// ```
/// use facet::Facet;
/// use facet_msgpack::from_str;
///
/// #[derive(Debug, Facet, PartialEq)]
/// struct User {
///     id: u64,
///     username: String,
/// }
///
/// // MessagePack binary data (equivalent to {"id": 42, "username": "user123"})
/// let msgpack_data = [
///     0x82, 0xa2, 0x69, 0x64, 0x2a, 0xa8, 0x75, 0x73,
///     0x65, 0x72, 0x6e, 0x61, 0x6d, 0x65, 0xa7, 0x75,
///     0x73, 0x65, 0x72, 0x31, 0x32, 0x33
/// ];
///
/// let user: User = from_str(&msgpack_data).unwrap();
/// assert_eq!(user, User { id: 42, username: "user123".to_string() });
/// ```
pub fn from_slice<T: Facet>(msgpack: &[u8]) -> Result<T, DecodeError> {
    from_slice_value(Wip::alloc::<T>(), msgpack)?
        .materialize::<T>()
        .map_err(|e| DecodeError::UnsupportedType(e.to_string()))
}

/// Alias for from_slice for backward compatibility
#[deprecated(since = "0.1.0", note = "Use from_slice instead")]
pub fn from_str<T: Facet>(msgpack: &[u8]) -> Result<T, DecodeError> {
    from_slice(msgpack)
}

/// Deserializes MessagePack-encoded data into a Facet value.
///
/// This function takes a MessagePack byte array and populates a Wip object
/// according to the shape description, returning an Opaque value.
///
/// # Example
///
/// ```
/// use facet::Facet;
/// use facet_msgpack::from_slice;
///
/// #[derive(Debug, Facet, PartialEq)]
/// struct User {
///     id: u64,
///     username: String,
/// }
///
/// // MessagePack binary data (equivalent to {"id": 42, "username": "user123"})
/// let msgpack_data = [
///     0x82, 0xa2, 0x69, 0x64, 0x2a, 0xa8, 0x75, 0x73,
///     0x65, 0x72, 0x6e, 0x61, 0x6d, 0x65, 0xa7, 0x75,
///     0x73, 0x65, 0x72, 0x31, 0x32, 0x33
/// ];
///
/// let user: User = from_slice(&msgpack_data).unwrap();
/// assert_eq!(user, User { id: 42, username: "user123".to_string() });
/// ```
///
/// # Parameters
/// * `wip` - A Wip object that will be filled with deserialized data
/// * `msgpack` - A byte slice containing MessagePack-encoded data
///
/// # Returns
/// * `Ok(Opaque)` containing the deserialized data if successful
/// * `Err(DecodeError)` if an error occurred during deserialization
///
/// # MessagePack Format
/// This implementation follows the MessagePack specification:
/// <https://github.com/msgpack/msgpack/blob/master/spec.md>
#[allow(clippy::needless_lifetimes)]
pub fn from_slice_value<'mem>(
    wip: Wip<'mem>,
    msgpack: &'mem [u8],
) -> Result<HeapValue<'mem>, DecodeError> {
    let mut decoder = Decoder::new(msgpack);
    decoder
        .deserialize_value(wip)?
        .build()
        .map_err(|e| DecodeError::UnsupportedType(e.to_string()))
}

struct Decoder<'input> {
    input: &'input [u8],
    offset: usize,
}

impl<'input> Decoder<'input> {
    fn new(input: &'input [u8]) -> Self {
        Decoder { input, offset: 0 }
    }

    /// Decodes a single byte from the input.
    /// This is a low-level method used by other decoders.
    fn decode_u8(&mut self) -> Result<u8, DecodeError> {
        if self.offset >= self.input.len() {
            return Err(DecodeError::InsufficientData);
        }
        let value = self.input[self.offset];
        self.offset += 1;
        Ok(value)
    }

    /// Decodes a 16-bit unsigned integer in big-endian byte order.
    /// This is a low-level method used by other decoders.
    fn decode_u16(&mut self) -> Result<u16, DecodeError> {
        if self.offset + 2 > self.input.len() {
            return Err(DecodeError::InsufficientData);
        }
        let value =
            u16::from_be_bytes(self.input[self.offset..self.offset + 2].try_into().unwrap());
        self.offset += 2;
        Ok(value)
    }

    /// Decodes a 32-bit unsigned integer in big-endian byte order.
    /// This is a low-level method used by other decoders.
    fn decode_u32(&mut self) -> Result<u32, DecodeError> {
        if self.offset + 4 > self.input.len() {
            return Err(DecodeError::InsufficientData);
        }
        let value =
            u32::from_be_bytes(self.input[self.offset..self.offset + 4].try_into().unwrap());
        self.offset += 4;
        Ok(value)
    }

    /// Decodes a MessagePack-encoded unsigned 64-bit integer.
    /// Handles the following MessagePack types:
    /// - positive fixint (0x00 - 0x7f): single-byte positive integer
    /// - uint8 (0xcc): 8-bit unsigned integer
    /// - uint16 (0xcd): 16-bit unsigned integer (big-endian)
    /// - uint32 (0xce): 32-bit unsigned integer (big-endian)
    /// - uint64 (0xcf): 64-bit unsigned integer (big-endian)
    ///
    /// Ref: <https://github.com/msgpack/msgpack/blob/master/spec.md#int-format-family>
    fn decode_u64(&mut self) -> Result<u64, DecodeError> {
        match self.decode_u8()? {
            MSGPACK_UINT8 => Ok(self.decode_u8()? as u64),
            MSGPACK_UINT16 => Ok(self.decode_u16()? as u64),
            MSGPACK_UINT32 => Ok(self.decode_u32()? as u64),
            MSGPACK_UINT64 => {
                if self.offset + 8 > self.input.len() {
                    return Err(DecodeError::InsufficientData);
                }
                let value = u64::from_be_bytes(
                    self.input[self.offset..self.offset + 8].try_into().unwrap(),
                );
                self.offset += 8;
                Ok(value)
            }
            prefix @ MSGPACK_POSFIXINT_MIN..=MSGPACK_POSFIXINT_MAX => Ok(prefix as u64),
            _ => Err(DecodeError::UnexpectedType),
        }
    }

    /// Decodes a MessagePack-encoded string.
    /// Handles the following MessagePack types:
    /// - fixstr (0xa0 - 0xbf): string up to 31 bytes
    /// - str8 (0xd9): string up to 255 bytes
    /// - str16 (0xda): string up to 65535 bytes
    /// - str32 (0xdb): string up to 4294967295 bytes
    ///
    /// Ref: <https://github.com/msgpack/msgpack/blob/master/spec.md#formats-str>
    fn decode_string(&mut self) -> Result<String, DecodeError> {
        let prefix = self.decode_u8()?;

        let len = match prefix {
            prefix @ MSGPACK_FIXSTR_MIN..=MSGPACK_FIXSTR_MAX => (prefix & 0x1f) as usize,
            MSGPACK_STR8 => self.decode_u8()? as usize,
            MSGPACK_STR16 => self.decode_u16()? as usize,
            MSGPACK_STR32 => self.decode_u32()? as usize,
            _ => return Err(DecodeError::UnexpectedType),
        };

        if self.offset + len > self.input.len() {
            return Err(DecodeError::InsufficientData);
        }

        let value = String::from_utf8(self.input[self.offset..self.offset + len].to_vec())
            .map_err(|_| DecodeError::InvalidData)?;
        self.offset += len;
        Ok(value)
    }

    /// Decodes a MessagePack-encoded map length.
    /// Handles the following MessagePack types:
    /// - fixmap (0x80 - 0x8f): map with up to 15 elements
    /// - map16 (0xde): map with up to 65535 elements
    /// - map32 (0xdf): map with up to 4294967295 elements
    ///
    /// Ref: <https://github.com/msgpack/msgpack/blob/master/spec.md#formats-map>
    fn decode_map_len(&mut self) -> Result<usize, DecodeError> {
        let prefix = self.decode_u8()?;

        match prefix {
            prefix @ MSGPACK_FIXMAP_MIN..=MSGPACK_FIXMAP_MAX => Ok((prefix & 0x0f) as usize),
            MSGPACK_MAP16 => Ok(self.decode_u16()? as usize),
            MSGPACK_MAP32 => Ok(self.decode_u32()? as usize),
            _ => Err(DecodeError::UnexpectedType),
        }
    }

    /// Decodes a MessagePack-encoded array length.
    /// Handles the following MessagePack types:
    /// - fixarray (0x90 - 0x9f): array with up to 15 elements
    /// - array16 (0xdc): array with up to 65535 elements
    /// - array32 (0xdd): array with up to 4294967295 elements
    ///
    /// Ref: <https://github.com/msgpack/msgpack/blob/master/spec.md#formats-array>
    #[allow(dead_code)]
    fn decode_array_len(&mut self) -> Result<usize, DecodeError> {
        let prefix = self.decode_u8()?;

        match prefix {
            prefix @ MSGPACK_FIXARRAY_MIN..=MSGPACK_FIXARRAY_MAX => Ok((prefix & 0x0f) as usize),
            MSGPACK_ARRAY16 => Ok(self.decode_u16()? as usize),
            MSGPACK_ARRAY32 => Ok(self.decode_u32()? as usize),
            _ => Err(DecodeError::UnexpectedType),
        }
    }

    /// Decodes a MessagePack-encoded boolean value.
    /// Handles the following MessagePack types:
    /// - true (0xc3): boolean true
    /// - false (0xc2): boolean false
    ///
    /// Ref: <https://github.com/msgpack/msgpack/blob/master/spec.md#formats-bool>
    fn decode_bool(&mut self) -> Result<bool, DecodeError> {
        match self.decode_u8()? {
            MSGPACK_TRUE => Ok(true),
            MSGPACK_FALSE => Ok(false),
            _ => Err(DecodeError::UnexpectedType),
        }
    }

    /// Decodes a MessagePack-encoded nil value.
    /// Handles the following MessagePack types:
    /// - nil (0xc0): nil/null value
    ///
    /// Ref: <https://github.com/msgpack/msgpack/blob/master/spec.md#formats-nil>
    #[allow(dead_code)]
    fn decode_nil(&mut self) -> Result<(), DecodeError> {
        match self.decode_u8()? {
            MSGPACK_NIL => Ok(()),
            _ => Err(DecodeError::UnexpectedType),
        }
    }

    /// Peeks at the next byte to check if it's a nil value without advancing the offset.
    /// Returns true if the next value is nil, false otherwise.
    #[allow(dead_code)]
    fn peek_nil(&mut self) -> Result<bool, DecodeError> {
        if self.offset >= self.input.len() {
            return Err(DecodeError::InsufficientData);
        }
        Ok(self.input[self.offset] == MSGPACK_NIL)
    }

    /// Skips a MessagePack value of any type.
    /// This is used when encountering unknown field names in a struct.
    fn skip_value(&mut self) -> Result<(), DecodeError> {
        let prefix = self.decode_u8()?;

        match prefix {
            // String formats
            prefix @ MSGPACK_FIXSTR_MIN..=MSGPACK_FIXSTR_MAX => {
                let len = (prefix & 0x1f) as usize;
                if self.offset + len > self.input.len() {
                    return Err(DecodeError::InsufficientData);
                }
                self.offset += len;
                Ok(())
            }
            MSGPACK_STR8 => {
                let len = self.decode_u8()? as usize;
                if self.offset + len > self.input.len() {
                    return Err(DecodeError::InsufficientData);
                }
                self.offset += len;
                Ok(())
            }
            MSGPACK_STR16 => {
                let len = self.decode_u16()? as usize;
                if self.offset + len > self.input.len() {
                    return Err(DecodeError::InsufficientData);
                }
                self.offset += len;
                Ok(())
            }
            MSGPACK_STR32 => {
                let len = self.decode_u32()? as usize;
                if self.offset + len > self.input.len() {
                    return Err(DecodeError::InsufficientData);
                }
                self.offset += len;
                Ok(())
            }

            // Integer formats
            MSGPACK_UINT8 => {
                self.offset += 1;
                Ok(())
            }
            MSGPACK_UINT16 => {
                self.offset += 2;
                Ok(())
            }
            MSGPACK_UINT32 => {
                self.offset += 4;
                Ok(())
            }
            MSGPACK_UINT64 => {
                self.offset += 8;
                Ok(())
            }
            MSGPACK_INT8 => {
                self.offset += 1;
                Ok(())
            }
            MSGPACK_INT16 => {
                self.offset += 2;
                Ok(())
            }
            MSGPACK_INT32 => {
                self.offset += 4;
                Ok(())
            }
            MSGPACK_INT64 => {
                self.offset += 8;
                Ok(())
            }
            // Fixed integers are already handled by decode_u8

            // Boolean and nil
            MSGPACK_NIL | MSGPACK_TRUE | MSGPACK_FALSE => Ok(()),

            // Map format
            prefix @ MSGPACK_FIXMAP_MIN..=MSGPACK_FIXMAP_MAX => {
                let len = (prefix & 0x0f) as usize;
                for _ in 0..len {
                    self.skip_value()?; // Skip key
                    self.skip_value()?; // Skip value
                }
                Ok(())
            }
            MSGPACK_MAP16 => {
                let len = self.decode_u16()? as usize;
                for _ in 0..len {
                    self.skip_value()?; // Skip key
                    self.skip_value()?; // Skip value
                }
                Ok(())
            }
            MSGPACK_MAP32 => {
                let len = self.decode_u32()? as usize;
                for _ in 0..len {
                    self.skip_value()?; // Skip key
                    self.skip_value()?; // Skip value
                }
                Ok(())
            }

            // Array format
            prefix @ MSGPACK_FIXARRAY_MIN..=MSGPACK_FIXARRAY_MAX => {
                let len = (prefix & 0x0f) as usize;
                for _ in 0..len {
                    self.skip_value()?;
                }
                Ok(())
            }
            MSGPACK_ARRAY16 => {
                let len = self.decode_u16()? as usize;
                for _ in 0..len {
                    self.skip_value()?;
                }
                Ok(())
            }
            MSGPACK_ARRAY32 => {
                let len = self.decode_u32()? as usize;
                for _ in 0..len {
                    self.skip_value()?;
                }
                Ok(())
            }

            _ => Err(DecodeError::UnexpectedType),
        }
    }

    fn deserialize_value(&mut self, wip: Wip<'input>) -> Result<Wip<'input>, DecodeError> {
        let shape = wip.shape();
        trace!("Deserializing {:?}", shape);

        let wip = match shape.def {
            Def::Scalar(_) => {
                trace!("Deserializing scalar");
                if shape.is_type::<String>() {
                    let s = self.decode_string()?;
                    wip.put(s).unwrap()
                } else if shape.is_type::<u64>() {
                    let n = self.decode_u64()?;
                    wip.put(n).unwrap()
                } else if shape.is_type::<u32>() {
                    let n = self.decode_u64()?;
                    if n > u32::MAX as u64 {
                        return Err(DecodeError::IntegerOverflow);
                    }
                    wip.put(n as u32).unwrap()
                } else if shape.is_type::<u16>() {
                    let n = self.decode_u64()?;
                    if n > u16::MAX as u64 {
                        return Err(DecodeError::IntegerOverflow);
                    }
                    wip.put(n as u16).unwrap()
                } else if shape.is_type::<u8>() {
                    let n = self.decode_u64()?;
                    if n > u8::MAX as u64 {
                        return Err(DecodeError::IntegerOverflow);
                    }
                    wip.put(n as u8).unwrap()
                } else if shape.is_type::<i64>() {
                    // This is a simplification - need to implement proper int decoding
                    let n = self.decode_u64()?;
                    if n > i64::MAX as u64 {
                        return Err(DecodeError::IntegerOverflow);
                    }
                    wip.put(n as i64).unwrap()
                } else if shape.is_type::<i32>() {
                    let n = self.decode_u64()?;
                    if n > i32::MAX as u64 {
                        return Err(DecodeError::IntegerOverflow);
                    }
                    wip.put(n as i32).unwrap()
                } else if shape.is_type::<bool>() {
                    let b = self.decode_bool()?;
                    wip.put(b).unwrap()
                } else {
                    return Err(DecodeError::UnsupportedType(format!("{}", shape)));
                }
            }
            Def::Struct(_) => {
                trace!("Deserializing struct");
                let map_len = self.decode_map_len()?;

                let mut wip = wip;
                for _ in 0..map_len {
                    let key = self.decode_string()?;
                    match wip.field_index(&key) {
                        Some(index) => {
                            wip = self
                                .deserialize_value(wip.field(index).unwrap())?
                                .pop()
                                .unwrap();
                        }
                        None => {
                            // Skip unknown field value
                            self.skip_value()?;
                            trace!("Skipping unknown field: {}", key);
                        }
                    }
                }
                wip
            }
            _ => {
                return Err(DecodeError::UnsupportedShape(format!("{:?}", shape)));
            }
        };

        Ok(wip)
    }
}