kiwi-schema 0.2.1

//! This is a Rust library with some helper routines for parsing files in the
//! Kiwi serialization format. See [https://github.com/evanw/kiwi](https://github.com/evanw/kiwi)
//! for documentation about the format.
//!
//! ```
//! use kiwi_schema::*;
//!
//! let schema = Schema::new(vec![
//!     Def::new("Point".to_owned(), DefKind::Struct, vec![
//!         Field {name: "x".to_owned(), type_id: TYPE_FLOAT, is_array: false, value: 0},
//!         Field {name: "y".to_owned(), type_id: TYPE_FLOAT, is_array: false, value: 0},
//!     ]),
//! ]);
//!
//! let value = Value::decode(&schema, 0, &[126, 0, 0, 0, 126, 1, 0, 0]).unwrap();
//! assert_eq!(format!("{:?}", value), "Point {x: 0.5, y: -0.5}");
//! assert_eq!(value.encode(&schema), [126, 0, 0, 0, 126, 1, 0, 0]);
//! ```

use std::borrow::Cow;
use std::collections::HashMap;
use std::f32;
use std::fmt;
use std::ops::Index;
use std::str;

/// A Kiwi byte buffer meant for reading.
///
/// Example usage:
///
/// ```
/// use std::borrow::Cow;
/// let mut bb = kiwi_schema::ByteBuffer::new(&[240, 159, 141, 149, 0, 133, 242, 210, 237]);
/// assert_eq!(bb.read_string(), Ok(Cow::Borrowed("🍕")));
/// assert_eq!(bb.read_var_float(), Ok(123.456));
/// ```
///
pub struct ByteBuffer<'a> {
    data: &'a [u8],
    index: usize,
}

impl<'a> ByteBuffer<'a> {
    /// Create a new ByteBuffer that wraps the provided byte slice. The lifetime
    /// of the returned ByteBuffer must not outlive the lifetime of the byte
    /// slice.
    pub fn new(data: &[u8]) -> ByteBuffer {
        ByteBuffer { data, index: 0 }
    }

    /// Retrieves the underlying byte slice.
    pub fn data(&self) -> &'a [u8] {
        self.data
    }

    /// Retrieves the current index into the underlying byte slice. This starts
    /// off as 0 and ends up as `self.data().len()` when everything has been
    /// read.
    pub fn index(&self) -> usize {
        self.index
    }

    /// Try to read a boolean value starting at the current index.
    pub fn read_bool(&mut self) -> Result<bool, ()> {
        match self.read_byte() {
            Ok(0) => Ok(false),
            Ok(1) => Ok(true),
            _ => Err(()),
        }
    }

    /// Try to read a byte starting at the current index.
    pub fn read_byte(&mut self) -> Result<u8, ()> {
        if self.index >= self.data.len() {
            Err(())
        } else {
            let value = self.data[self.index];
            self.index = self.index + 1;
            Ok(value)
        }
    }

    /// Try to read a byte starting at the current index.
    pub fn read_bytes(&mut self, len: usize) -> Result<&'a [u8], ()> {
        if self.index + len > self.data.len() {
            Err(())
        } else {
            let value = &self.data[self.index..self.index + len];
            self.index = self.index + len;
            Ok(value)
        }
    }

    /// Try to read a variable-length signed 32-bit integer starting at the
    /// current index.
    pub fn read_var_int(&mut self) -> Result<i32, ()> {
        let value = self.read_var_uint()?;
        Ok((if (value & 1) != 0 {
            !(value >> 1)
        } else {
            value >> 1
        }) as i32)
    }

    /// Try to read a variable-length unsigned 32-bit integer starting at the
    /// current index.
    pub fn read_var_uint(&mut self) -> Result<u32, ()> {
        let mut shift: u8 = 0;
        let mut result: u32 = 0;

        loop {
            let byte = self.read_byte()?;
            result |= ((byte & 127) as u32) << shift;
            shift += 7;

            if (byte & 128) == 0 || shift >= 35 {
                break;
            }
        }

        Ok(result)
    }

    /// Try to read a variable-length 32-bit floating-point number starting at
    /// the current index.
    pub fn read_var_float(&mut self) -> Result<f32, ()> {
        let first = self.read_byte()?;

        // Optimization: use a single byte to store zero
        if first == 0 {
            Ok(0.0)
        } else if self.index + 3 > self.data.len() {
            Err(())
        }
        // Endian-independent 32-bit read
        else {
            let mut bits: u32 = first as u32
                | ((self.data[self.index] as u32) << 8)
                | ((self.data[self.index + 1] as u32) << 16)
                | ((self.data[self.index + 2] as u32) << 24);
            self.index += 3;

            // Move the exponent back into place
            bits = (bits << 23) | (bits >> 9);

            Ok(f32::from_bits(bits))
        }
    }

    /// Try to read a UTF-8 string starting at the current index. This string is
    /// returned as a slice so it just aliases the underlying memory.
    pub fn read_string(&mut self) -> Result<Cow<'a, str>, ()> {
        let start = self.index;

        while self.index < self.data.len() {
            if self.data[self.index] == 0 {
                self.index += 1;
                return Ok(String::from_utf8_lossy(&self.data[start..self.index - 1]));
            }

            self.index += 1;
        }

        Err(())
    }

    /// Try to read a variable-length signed 64-bit integer starting at the
    /// current index.
    pub fn read_var_int64(&mut self) -> Result<i64, ()> {
        let value = self.read_var_uint64()?;
        Ok((if (value & 1) != 0 {
            !(value >> 1)
        } else {
            value >> 1
        }) as i64)
    }

    /// Try to read a variable-length unsigned 64-bit integer starting at the
    /// current index.
    pub fn read_var_uint64(&mut self) -> Result<u64, ()> {
        let mut shift: u8 = 0;
        let mut result: u64 = 0;

        loop {
            let byte = self.read_byte()?;
            if (byte & 128) == 0 || shift >= 56 {
                result |= (byte as u64) << shift;
                break;
            }
            result |= ((byte & 127) as u64) << shift;
            shift += 7;
        }

        Ok(result)
    }
}

#[test]
fn read_bool() {
    let try = |bytes| ByteBuffer::new(bytes).read_bool();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(false));
    assert_eq!(try(&[1]), Ok(true));
    assert_eq!(try(&[2]), Err(()));
}

#[test]
fn read_byte() {
    let try = |bytes| ByteBuffer::new(bytes).read_byte();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(0));
    assert_eq!(try(&[1]), Ok(1));
    assert_eq!(try(&[254]), Ok(254));
    assert_eq!(try(&[255]), Ok(255));
}

#[test]
fn read_bytes() {
    let try = |bytes, len| ByteBuffer::new(bytes).read_bytes(len);
    assert_eq!(try(&[], 0), Ok(vec![].as_slice()));
    assert_eq!(try(&[], 1), Err(()));
    assert_eq!(try(&[0], 0), Ok(vec![].as_slice()));
    assert_eq!(try(&[0], 1), Ok(vec![0].as_slice()));
    assert_eq!(try(&[0], 2), Err(()));

    let mut bb = ByteBuffer::new(&[1, 2, 3, 4, 5]);
    assert_eq!(bb.read_bytes(3), Ok(vec![1, 2, 3].as_slice()));
    assert_eq!(bb.read_bytes(2), Ok(vec![4, 5].as_slice()));
    assert_eq!(bb.read_bytes(1), Err(()));
}

#[test]
fn read_var_int() {
    let try = |bytes| ByteBuffer::new(bytes).read_var_int();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(0));
    assert_eq!(try(&[1]), Ok(-1));
    assert_eq!(try(&[2]), Ok(1));
    assert_eq!(try(&[3]), Ok(-2));
    assert_eq!(try(&[4]), Ok(2));
    assert_eq!(try(&[127]), Ok(-64));
    assert_eq!(try(&[128]), Err(()));
    assert_eq!(try(&[128, 0]), Ok(0));
    assert_eq!(try(&[128, 1]), Ok(64));
    assert_eq!(try(&[128, 2]), Ok(128));
    assert_eq!(try(&[129, 0]), Ok(-1));
    assert_eq!(try(&[129, 1]), Ok(-65));
    assert_eq!(try(&[129, 2]), Ok(-129));
    assert_eq!(try(&[253, 255, 7]), Ok(-65535));
    assert_eq!(try(&[254, 255, 7]), Ok(65535));
    assert_eq!(try(&[253, 255, 255, 255, 15]), Ok(-2147483647));
    assert_eq!(try(&[254, 255, 255, 255, 15]), Ok(2147483647));
    assert_eq!(try(&[255, 255, 255, 255, 15]), Ok(-2147483648));
}

#[test]
fn read_var_uint() {
    let try = |bytes| ByteBuffer::new(bytes).read_var_uint();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(0));
    assert_eq!(try(&[1]), Ok(1));
    assert_eq!(try(&[2]), Ok(2));
    assert_eq!(try(&[3]), Ok(3));
    assert_eq!(try(&[4]), Ok(4));
    assert_eq!(try(&[127]), Ok(127));
    assert_eq!(try(&[128]), Err(()));
    assert_eq!(try(&[128, 0]), Ok(0));
    assert_eq!(try(&[128, 1]), Ok(128));
    assert_eq!(try(&[128, 2]), Ok(256));
    assert_eq!(try(&[129, 0]), Ok(1));
    assert_eq!(try(&[129, 1]), Ok(129));
    assert_eq!(try(&[129, 2]), Ok(257));
    assert_eq!(try(&[253, 255, 7]), Ok(131069));
    assert_eq!(try(&[254, 255, 7]), Ok(131070));
    assert_eq!(try(&[253, 255, 255, 255, 15]), Ok(4294967293));
    assert_eq!(try(&[254, 255, 255, 255, 15]), Ok(4294967294));
    assert_eq!(try(&[255, 255, 255, 255, 15]), Ok(4294967295));
}

#[test]
fn read_var_float() {
    let try = |bytes| ByteBuffer::new(bytes).read_var_float();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(0.0));
    assert_eq!(try(&[133, 242, 210, 237]), Ok(123.456));
    assert_eq!(try(&[133, 243, 210, 237]), Ok(-123.456));
    assert_eq!(try(&[254, 255, 255, 255]), Ok(f32::MIN));
    assert_eq!(try(&[254, 254, 255, 255]), Ok(f32::MAX));
    assert_eq!(try(&[1, 1, 0, 0]), Ok(-f32::MIN_POSITIVE));
    assert_eq!(try(&[1, 0, 0, 0]), Ok(f32::MIN_POSITIVE));
    assert_eq!(try(&[255, 1, 0, 0]), Ok(f32::NEG_INFINITY));
    assert_eq!(try(&[255, 0, 0, 0]), Ok(f32::INFINITY));
    assert_eq!(try(&[255, 0, 0, 128]).map(|f| f.is_nan()), Ok(true));
}

#[test]
fn read_string() {
    let try = |bytes| ByteBuffer::new(bytes).read_string();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(Cow::Borrowed("")));
    assert_eq!(try(&[97]), Err(()));
    assert_eq!(try(&[97, 0]), Ok(Cow::Borrowed("a")));
    assert_eq!(try(&[97, 98, 99, 0]), Ok(Cow::Borrowed("abc")));
    assert_eq!(try(&[240, 159, 141, 149, 0]), Ok(Cow::Borrowed("🍕")));
    assert_eq!(
        try(&[97, 237, 160, 188, 99, 0]),
        Ok(Cow::Owned("a���c".to_owned()))
    );
}

#[test]
fn read_var_int64() {
    let try = |bytes| ByteBuffer::new(bytes).read_var_int64();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(0));
    assert_eq!(try(&[1]), Ok(-1));
    assert_eq!(try(&[2]), Ok(1));
    assert_eq!(try(&[3]), Ok(-2));
    assert_eq!(try(&[4]), Ok(2));
    assert_eq!(try(&[127]), Ok(-64));
    assert_eq!(try(&[128]), Err(()));
    assert_eq!(try(&[128, 0]), Ok(0));
    assert_eq!(try(&[128, 1]), Ok(64));
    assert_eq!(try(&[128, 2]), Ok(128));
    assert_eq!(try(&[129, 0]), Ok(-1));
    assert_eq!(try(&[129, 1]), Ok(-65));
    assert_eq!(try(&[129, 2]), Ok(-129));
    assert_eq!(try(&[253, 255, 7]), Ok(-65535));
    assert_eq!(try(&[254, 255, 7]), Ok(65535));
    assert_eq!(try(&[253, 255, 255, 255, 15]), Ok(-2147483647));
    assert_eq!(try(&[254, 255, 255, 255, 15]), Ok(2147483647));
    assert_eq!(try(&[255, 255, 255, 255, 15]), Ok(-2147483648));
    assert_eq!(
        try(&[0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88]),
        Ok(0x4407_0C14_2030_4040)
    );
    assert_eq!(
        try(&[0x81, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x20]),
        Ok(-0x1000_0000_0000_0001)
    );
    assert_eq!(
        try(&[0x82, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x20]),
        Ok(0x1000_0000_0000_0001)
    );
    assert_eq!(
        try(&[0xFD, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]),
        Ok(-0x3FFF_FFFF_FFFF_FFFF)
    );
    assert_eq!(
        try(&[0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]),
        Ok(0x3FFF_FFFF_FFFF_FFFF)
    );
    assert_eq!(
        try(&[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]),
        Ok(-0x4000_0000_0000_0000)
    );
    assert_eq!(
        try(&[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80]),
        Ok(0x4000_0000_0000_0000)
    );
    assert_eq!(
        try(&[0xFD, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]),
        Ok(-0x7FFF_FFFF_FFFF_FFFF)
    );
    assert_eq!(
        try(&[0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]),
        Ok(0x7FFF_FFFF_FFFF_FFFF)
    );
    assert_eq!(
        try(&[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]),
        Ok(-0x8000_0000_0000_0000)
    );
}

#[test]
fn read_var_uint64() {
    let try = |bytes| ByteBuffer::new(bytes).read_var_uint64();
    assert_eq!(try(&[]), Err(()));
    assert_eq!(try(&[0]), Ok(0));
    assert_eq!(try(&[1]), Ok(1));
    assert_eq!(try(&[2]), Ok(2));
    assert_eq!(try(&[3]), Ok(3));
    assert_eq!(try(&[4]), Ok(4));
    assert_eq!(try(&[127]), Ok(127));
    assert_eq!(try(&[128]), Err(()));
    assert_eq!(try(&[128, 0]), Ok(0));
    assert_eq!(try(&[128, 1]), Ok(128));
    assert_eq!(try(&[128, 2]), Ok(256));
    assert_eq!(try(&[129, 0]), Ok(1));
    assert_eq!(try(&[129, 1]), Ok(129));
    assert_eq!(try(&[129, 2]), Ok(257));
    assert_eq!(try(&[253, 255, 7]), Ok(131069));
    assert_eq!(try(&[254, 255, 7]), Ok(131070));
    assert_eq!(try(&[253, 255, 255, 255, 15]), Ok(4294967293));
    assert_eq!(try(&[254, 255, 255, 255, 15]), Ok(4294967294));
    assert_eq!(try(&[255, 255, 255, 255, 15]), Ok(4294967295));
    assert_eq!(
        try(&[0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88]),
        Ok(0x880E_1828_4060_8080)
    );
    assert_eq!(
        try(&[0x81, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x10]),
        Ok(0x1000_0000_0000_0001)
    );
    assert_eq!(
        try(&[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]),
        Ok(0x7FFF_FFFF_FFFF_FFFF)
    );
    assert_eq!(
        try(&[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80]),
        Ok(0x8000_0000_0000_0000)
    );
    assert_eq!(
        try(&[0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]),
        Ok(0xFFFF_FFFF_FFFF_FFFF)
    );
}

#[test]
fn read_sequence() {
    let mut bb = ByteBuffer::new(&[
        0, 133, 242, 210, 237, 240, 159, 141, 149, 0, 149, 154, 239, 58,
    ]);
    assert_eq!(bb.read_var_float(), Ok(0.0));
    assert_eq!(bb.read_var_float(), Ok(123.456));
    assert_eq!(bb.read_string(), Ok(Cow::Borrowed("🍕")));
    assert_eq!(bb.read_var_uint(), Ok(123456789));
}

/// A Kiwi byte buffer meant for writing.
///
/// Example usage:
///
/// ```
/// let mut bb = kiwi_schema::ByteBufferMut::new();
/// bb.write_string("🍕");
/// bb.write_var_float(123.456);
/// assert_eq!(bb.data(), [240, 159, 141, 149, 0, 133, 242, 210, 237]);
/// ```
///
pub struct ByteBufferMut {
    data: Vec<u8>,
}

impl ByteBufferMut {
    /// Creates an empty ByteBufferMut ready for writing.
    pub fn new() -> ByteBufferMut {
        ByteBufferMut { data: vec![] }
    }

    /// Consumes this buffer and returns the underlying backing store. Use this
    /// to get the data out when you're done writing to the buffer.
    pub fn data(self) -> Vec<u8> {
        self.data
    }

    /// Returns the number of bytes written so far.
    pub fn len(&self) -> usize {
        self.data.len()
    }

    /// Write a boolean value to the end of the buffer.
    pub fn write_bool(&mut self, value: bool) {
        self.data.push(if value { 1 } else { 0 });
    }

    /// Write a byte to the end of the buffer.
    pub fn write_byte(&mut self, value: u8) {
        self.data.push(value);
    }

    /// Write a raw byte slice to the end of the buffer.
    pub fn write_bytes(&mut self, value: &[u8]) {
        self.data.extend_from_slice(value);
    }

    /// Write a variable-length signed 32-bit integer to the end of the buffer.
    pub fn write_var_int(&mut self, value: i32) {
        self.write_var_uint(((value << 1) ^ (value >> 31)) as u32);
    }

    /// Write a variable-length unsigned 32-bit integer to the end of the buffer.
    pub fn write_var_uint(&mut self, mut value: u32) {
        loop {
            let byte = value as u8 & 127;
            value >>= 7;

            if value == 0 {
                self.write_byte(byte);
                return;
            }

            self.write_byte(byte | 128);
        }
    }

    /// Write a variable-length 32-bit floating-point number to the end of the
    /// buffer.
    pub fn write_var_float(&mut self, value: f32) {
        // Reinterpret as an integer
        let mut bits = value.to_bits();

        // Move the exponent to the first 8 bits
        bits = (bits >> 23) | (bits << 9);

        // Optimization: use a single byte to store zero and denormals (try for an exponent of 0)
        if (bits & 255) == 0 {
            self.data.push(0);
            return;
        }

        // Endian-independent 32-bit write
        self.data.extend_from_slice(&[
            bits as u8,
            (bits >> 8) as u8,
            (bits >> 16) as u8,
            (bits >> 24) as u8,
        ]);
    }

    /// Write a UTF-8 string to the end of the buffer.
    pub fn write_string(&mut self, value: &str) {
        self.data.extend_from_slice(value.as_bytes());
        self.data.push(0);
    }

    /// Write a variable-length signed 64-bit integer to the end of the buffer.
    pub fn write_var_int64(&mut self, value: i64) {
        self.write_var_uint64(((value << 1) ^ (value >> 63)) as u64);
    }

    /// Write a variable-length unsigned 64-bit integer to the end of the buffer.
    pub fn write_var_uint64(&mut self, mut value: u64) {
        let mut i = 0;
        while value > 127 && i < 8 {
            self.write_byte((value as u8 & 127) | 128);
            value >>= 7;
            i += 1;
        }
        self.write_byte(value as u8);
    }
}

#[cfg(test)]
fn write_once(cb: fn(&mut ByteBufferMut)) -> Vec<u8> {
    let mut bb = ByteBufferMut::new();
    cb(&mut bb);
    bb.data()
}

#[test]
fn write_bool() {
    assert_eq!(write_once(|bb| bb.write_bool(false)), [0]);
    assert_eq!(write_once(|bb| bb.write_bool(true)), [1]);
}

#[test]
fn write_byte() {
    assert_eq!(write_once(|bb| bb.write_byte(0)), [0]);
    assert_eq!(write_once(|bb| bb.write_byte(1)), [1]);
    assert_eq!(write_once(|bb| bb.write_byte(254)), [254]);
    assert_eq!(write_once(|bb| bb.write_byte(255)), [255]);
}

#[test]
fn write_bytes() {
    let mut bb = ByteBufferMut::new();
    bb.write_bytes(&[1, 2, 3]);
    bb.write_bytes(&[]);
    bb.write_bytes(&[4, 5]);
    assert_eq!(bb.data(), [1, 2, 3, 4, 5]);
}

#[test]
fn write_var_int() {
    assert_eq!(write_once(|bb| bb.write_var_int(0)), [0]);
    assert_eq!(write_once(|bb| bb.write_var_int(-1)), [1]);
    assert_eq!(write_once(|bb| bb.write_var_int(1)), [2]);
    assert_eq!(write_once(|bb| bb.write_var_int(-2)), [3]);
    assert_eq!(write_once(|bb| bb.write_var_int(2)), [4]);
    assert_eq!(write_once(|bb| bb.write_var_int(-64)), [127]);
    assert_eq!(write_once(|bb| bb.write_var_int(64)), [128, 1]);
    assert_eq!(write_once(|bb| bb.write_var_int(128)), [128, 2]);
    assert_eq!(write_once(|bb| bb.write_var_int(-129)), [129, 2]);
    assert_eq!(write_once(|bb| bb.write_var_int(-65535)), [253, 255, 7]);
    assert_eq!(write_once(|bb| bb.write_var_int(65535)), [254, 255, 7]);
    assert_eq!(
        write_once(|bb| bb.write_var_int(-2147483647)),
        [253, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int(2147483647)),
        [254, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int(-2147483648)),
        [255, 255, 255, 255, 15]
    );
}

#[test]
fn write_var_uint() {
    assert_eq!(write_once(|bb| bb.write_var_uint(0)), [0]);
    assert_eq!(write_once(|bb| bb.write_var_uint(1)), [1]);
    assert_eq!(write_once(|bb| bb.write_var_uint(2)), [2]);
    assert_eq!(write_once(|bb| bb.write_var_uint(3)), [3]);
    assert_eq!(write_once(|bb| bb.write_var_uint(4)), [4]);
    assert_eq!(write_once(|bb| bb.write_var_uint(127)), [127]);
    assert_eq!(write_once(|bb| bb.write_var_uint(128)), [128, 1]);
    assert_eq!(write_once(|bb| bb.write_var_uint(256)), [128, 2]);
    assert_eq!(write_once(|bb| bb.write_var_uint(129)), [129, 1]);
    assert_eq!(write_once(|bb| bb.write_var_uint(257)), [129, 2]);
    assert_eq!(write_once(|bb| bb.write_var_uint(131069)), [253, 255, 7]);
    assert_eq!(write_once(|bb| bb.write_var_uint(131070)), [254, 255, 7]);
    assert_eq!(
        write_once(|bb| bb.write_var_uint(4294967293)),
        [253, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint(4294967294)),
        [254, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint(4294967295)),
        [255, 255, 255, 255, 15]
    );
}

#[test]
fn write_var_float() {
    assert_eq!(write_once(|bb| bb.write_var_float(0.0)), [0]);
    assert_eq!(write_once(|bb| bb.write_var_float(-0.0)), [0]);
    assert_eq!(
        write_once(|bb| bb.write_var_float(123.456)),
        [133, 242, 210, 237]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(-123.456)),
        [133, 243, 210, 237]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(f32::MIN)),
        [254, 255, 255, 255]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(f32::MAX)),
        [254, 254, 255, 255]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(-f32::MIN_POSITIVE)),
        [1, 1, 0, 0]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(f32::MIN_POSITIVE)),
        [1, 0, 0, 0]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(f32::NEG_INFINITY)),
        [255, 1, 0, 0]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(f32::INFINITY)),
        [255, 0, 0, 0]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_float(f32::NAN)),
        [255, 0, 0, 128]
    );
    assert_eq!(write_once(|bb| bb.write_var_float(1.0e-40)), [0]);
}

#[test]
fn write_string() {
    assert_eq!(write_once(|bb| bb.write_string("")), [0]);
    assert_eq!(write_once(|bb| bb.write_string("a")), [97, 0]);
    assert_eq!(write_once(|bb| bb.write_string("abc")), [97, 98, 99, 0]);
    assert_eq!(
        write_once(|bb| bb.write_string("🍕")),
        [240, 159, 141, 149, 0]
    );
}

#[test]
fn write_var_int64() {
    assert_eq!(write_once(|bb| bb.write_var_int64(0)), [0]);
    assert_eq!(write_once(|bb| bb.write_var_int64(-1)), [1]);
    assert_eq!(write_once(|bb| bb.write_var_int64(1)), [2]);
    assert_eq!(write_once(|bb| bb.write_var_int64(-2)), [3]);
    assert_eq!(write_once(|bb| bb.write_var_int64(2)), [4]);
    assert_eq!(write_once(|bb| bb.write_var_int64(-64)), [127]);
    assert_eq!(write_once(|bb| bb.write_var_int64(64)), [128, 1]);
    assert_eq!(write_once(|bb| bb.write_var_int64(128)), [128, 2]);
    assert_eq!(write_once(|bb| bb.write_var_int64(-129)), [129, 2]);
    assert_eq!(write_once(|bb| bb.write_var_int64(-65535)), [253, 255, 7]);
    assert_eq!(write_once(|bb| bb.write_var_int64(65535)), [254, 255, 7]);
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-2147483647)),
        [253, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(2147483647)),
        [254, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-2147483648)),
        [255, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-0x1000_0000_0000_0001)),
        [0x81, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x20]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(0x1000_0000_0000_0001)),
        [0x82, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x20]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-0x3FFF_FFFF_FFFF_FFFF)),
        [0xFD, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(0x3FFF_FFFF_FFFF_FFFF)),
        [0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-0x4000_0000_0000_0000)),
        [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(0x4000_0000_0000_0000)),
        [0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-0x7FFF_FFFF_FFFF_FFFF)),
        [0xFD, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(0x7FFF_FFFF_FFFF_FFFF)),
        [0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_int64(-0x8000_0000_0000_0000)),
        [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]
    );
}

#[test]
fn write_var_uint64() {
    assert_eq!(write_once(|bb| bb.write_var_uint64(0)), [0]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(1)), [1]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(2)), [2]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(3)), [3]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(4)), [4]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(127)), [127]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(128)), [128, 1]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(256)), [128, 2]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(129)), [129, 1]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(257)), [129, 2]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(131069)), [253, 255, 7]);
    assert_eq!(write_once(|bb| bb.write_var_uint64(131070)), [254, 255, 7]);
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(4294967293)),
        [253, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(4294967294)),
        [254, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(4294967295)),
        [255, 255, 255, 255, 15]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(0x1000_0000_0000_0001)),
        [0x81, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x10]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(0x7FFF_FFFF_FFFF_FFFF)),
        [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(0x8000_0000_0000_0000)),
        [0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80]
    );
    assert_eq!(
        write_once(|bb| bb.write_var_uint64(0xFFFF_FFFF_FFFF_FFFF)),
        [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF]
    );
}

#[test]
fn write_sequence() {
    let mut bb = ByteBufferMut::new();
    bb.write_var_float(0.0);
    bb.write_var_float(123.456);
    bb.write_string("🍕");
    bb.write_var_uint(123456789);
    assert_eq!(
        bb.data(),
        [0, 133, 242, 210, 237, 240, 159, 141, 149, 0, 149, 154, 239, 58]
    );
}

pub const TYPE_BOOL: i32 = -1;
pub const TYPE_BYTE: i32 = -2;
pub const TYPE_INT: i32 = -3;
pub const TYPE_UINT: i32 = -4;
pub const TYPE_FLOAT: i32 = -5;
pub const TYPE_STRING: i32 = -6;
pub const TYPE_INT64: i32 = -7;
pub const TYPE_UINT64: i32 = -8;

/// Represents a single field in a [Def](struct.Def.html).
#[derive(Debug, PartialEq)]
pub struct Field {
    /// The name of this field from the textual Kiwi schema.
    pub name: String,

    /// For user-defined types, this is the index of the [Def](struct.Def.html)
    /// in the `defs` array of the [Schema](struct.Schema.html).
    /// Built-in types use special constants:
    ///
    /// * [TYPE_BOOL](constant.TYPE_BOOL.html)
    /// * [TYPE_BYTE](constant.TYPE_BYTE.html)
    /// * [TYPE_INT](constant.TYPE_INT.html)
    /// * [TYPE_UINT](constant.TYPE_UINT.html)
    /// * [TYPE_FLOAT](constant.TYPE_FLOAT.html)
    /// * [TYPE_STRING](constant.TYPE_STRING.html)
    /// * [TYPE_INT64](constant.TYPE_INT64.html)
    /// * [TYPE_UINT64](constant.TYPE_UINT64.html)
    pub type_id: i32,

    /// True if this field was declared as an array (e.g. `int[]` instead of
    /// `int` in the textual Kiwi schema). Arrays are encoded using a length
    /// prefix followed by that many items.
    pub is_array: bool,

    /// The identifier corresponding to this field. This is the enum value for
    /// enum definitions and the field id for message definitions. This value has
    /// no meaning for struct definitions.
    pub value: u32,
}

#[derive(Debug, PartialEq, Eq)]
pub enum DefKind {
    /// Enums are encoded as variable-length unsigned integers under the hood.
    /// Declaring one in the textual Kiwi format looks like this:
    ///
    /// ```text
    /// enum Example {
    ///   A = 100;
    ///   B = 200;
    /// }
    /// ```
    Enum,

    /// Structs are tuples of fields and are encoded by encoding each field in
    /// order. All fields are guaranteed to be present. Declaring one in the
    /// textual Kiwi format looks like this:
    ///
    /// ```text
    /// struct Example {
    ///   int a;
    ///   int b;
    /// }
    /// ```
    Struct,

    /// Messages are objects filled with optional fields and are encoded as a
    /// sequence of (id, value) pairs followed by a zero byte. All fields are
    /// optional and may not be present. Declaring one in the textual Kiwi format
    /// looks like this:
    ///
    /// ```text
    /// message Example {
    ///   int a = 1;
    ///   int b = 2;
    /// }
    /// ```
    Message,
}

pub const DEF_ENUM: u8 = 0;
pub const DEF_STRUCT: u8 = 1;
pub const DEF_MESSAGE: u8 = 2;

/// Represents a single definition in a [Schema](struct.Schema.html).
/// Kiwi enums, structs, and messages are all represented using this object.
#[derive(Debug, PartialEq)]
pub struct Def {
    /// The name of this field from the textual Kiwi schema.
    pub name: String,

    /// The index of this Def in the `defs` field of the parent
    /// [Schema](struct.Schema.html). This is used as the type
    /// identifier for any fields with this type.
    pub index: i32,

    /// Either [Enum](enum.DefKind.html#variant.Enum),
    /// [Struct](enum.DefKind.html#variant.Struct), or
    /// [Message](enum.DefKind.html#variant.Message).
    pub kind: DefKind,

    /// All fields in this definition. The order matters for struct definitions.
    pub fields: Vec<Field>,

    /// Maps the `value` and `name` members of each [Field](struct.Field.html) in
    /// the `fields` array to its index in that array. This is helpful when
    /// decoding and encoding a field to be able to quickly get to the field
    /// metadata.
    pub field_value_to_index: HashMap<u32, usize>,
    pub field_name_to_index: HashMap<String, usize>,
}

impl Def {
    pub fn new(name: String, kind: DefKind, fields: Vec<Field>) -> Def {
        let mut field_value_to_index = HashMap::new();
        let mut field_name_to_index = HashMap::new();
        for (i, field) in fields.iter().enumerate() {
            field_value_to_index.insert(field.value, i);
            field_name_to_index.insert(field.name.clone(), i);
        }
        Def {
            name,
            index: 0,
            kind,
            fields,
            field_value_to_index,
            field_name_to_index,
        }
    }

    /// Returns the [Field](struct.Field.html) with the provided name if one exists.
    pub fn field(&self, name: &str) -> Option<&Field> {
        self.field_name_to_index.get(name).map(|i| &self.fields[*i])
    }
}

#[derive(Debug, PartialEq)]
pub struct SchemaOptions {
    // The Rust implementation is the only one that validates enums while skipping fields.
    // Ideally all implementations should end up validating enums, but to maintain
    // compatibility with other clients this can be used to allow enums to be decoded
    // even if they aren't valid.
    pub validate_enums: bool,
}

/// Holds the contents of a Kiwi schema.
///
/// Each schema consists of a list of definitions, each of which has a list of
/// fields. It can either be constructed in memory or decoded from a file in
/// the binary Kiwi schema format.
///
/// Example usage:
///
/// ```
/// // This is the encoding of the Kiwi schema "message ABC { int[] xyz = 1; }"
/// let schema_bytes = [1, 65, 66, 67, 0, 2, 1, 120, 121, 122, 0, 5, 1, 1];
/// let schema = kiwi_schema::Schema::decode(&schema_bytes).unwrap();
///
/// let def = schema.def("ABC").unwrap();
/// assert_eq!(def.kind, kiwi_schema::DefKind::Message);
///
/// let field = def.field("xyz").unwrap();
/// assert_eq!(field.type_id, kiwi_schema::TYPE_INT);
/// assert_eq!(field.is_array, true);
/// assert_eq!(field.value, 1);
/// ```
#[derive(Debug, PartialEq)]
pub struct Schema {
    pub defs: Vec<Def>,

    /// Maps the `name` member of each [Def](struct.Def.html) in the `defs` array
    /// to its index in that array. This is helpful when decoding and encoding a
    /// field to be able to quickly get to the field metadata.
    pub def_name_to_index: HashMap<String, usize>,
}

impl Schema {
    pub fn new(mut defs: Vec<Def>) -> Schema {
        let mut def_name_to_index = HashMap::new();
        for (i, def) in defs.iter_mut().enumerate() {
            def.index = i as i32;
            def_name_to_index.insert(def.name.clone(), i);
        }
        Schema {
            defs,
            def_name_to_index,
        }
    }

    /// Parses a Kiwi schema encoded in the binary format and returns the parsed
    /// schema if successful. A textual schema can be compiled into a binary
    /// schema using the command-line tools:
    ///
    /// ```text
    /// kiwic --schema example.kiwi --binary example.bkiwi
    /// ```
    pub fn decode(bytes: &[u8]) -> Result<Schema, ()> {
        let mut defs = Vec::new();
        let mut bb = ByteBuffer::new(bytes);
        let definition_count = bb.read_var_uint()?;

        for _ in 0..definition_count {
            let name = bb.read_string()?.into_owned();
            let kind = match bb.read_byte()? {
                DEF_ENUM => DefKind::Enum,
                DEF_STRUCT => DefKind::Struct,
                DEF_MESSAGE => DefKind::Message,
                _ => return Err(()),
            };
            let field_count = bb.read_var_uint()?;
            let mut fields = Vec::new();

            for _ in 0..field_count {
                let name = bb.read_string()?.into_owned();
                let type_id = bb.read_var_int()?;
                let is_array = bb.read_bool()?;
                let value = bb.read_var_uint()?;
                if type_id < TYPE_UINT64 || type_id >= definition_count as i32 {
                    return Err(());
                }
                fields.push(Field {
                    name,
                    type_id,
                    is_array,
                    value,
                });
            }

            defs.push(Def::new(name, kind, fields));
        }

        Ok(Schema::new(defs))
    }

    /// The opposite of [decode](#method.decode). Turns this schema back into a
    /// binary file.
    pub fn encode(&self) -> Vec<u8> {
        let mut bb = ByteBufferMut::new();
        bb.write_var_uint(self.defs.len() as u32);

        for def in &self.defs {
            bb.write_string(def.name.as_str());
            bb.write_byte(match def.kind {
                DefKind::Enum => DEF_ENUM,
                DefKind::Struct => DEF_STRUCT,
                DefKind::Message => DEF_MESSAGE,
            });
            bb.write_var_uint(def.fields.len() as u32);

            for field in &def.fields {
                bb.write_string(field.name.as_str());
                bb.write_var_int(field.type_id);
                bb.write_bool(field.is_array);
                bb.write_var_uint(field.value);
            }
        }

        bb.data()
    }

    /// Returns the [Def](struct.Def.html) with the provided name if one exists.
    pub fn def(&self, name: &str) -> Option<&Def> {
        self.def_name_to_index.get(name).map(|i| &self.defs[*i])
    }

    /// Advances the current index of the provided [ByteBuffer](struct.ByteBuffer.html)
    /// by the size of a field with the provided type information. The Kiwi format
    /// doesn't support seeking around to arbitrary points (it must be read from
    /// start to end) so this method is helpful when you need to to skip past
    /// unimportant fields.
    pub fn skip_with_options(
        &self,
        bb: &mut ByteBuffer,
        type_id: i32,
        options: &SchemaOptions,
    ) -> Result<(), ()> {
        match type_id {
            TYPE_BOOL => {
                bb.read_bool()?;
            }
            TYPE_BYTE => {
                bb.read_byte()?;
            }
            TYPE_INT => {
                bb.read_var_int()?;
            }
            TYPE_UINT => {
                bb.read_var_uint()?;
            }
            TYPE_FLOAT => {
                bb.read_var_float()?;
            }
            TYPE_STRING => {
                bb.read_string()?;
            }
            TYPE_INT64 => {
                bb.read_var_int64()?;
            }
            TYPE_UINT64 => {
                bb.read_var_uint64()?;
            }

            _ => {
                let def = &self.defs[type_id as usize];

                match def.kind {
                    DefKind::Enum => {
                        if !def.field_value_to_index.contains_key(&bb.read_var_uint()?)
                            && options.validate_enums
                        {
                            return Err(());
                        }
                    }

                    DefKind::Struct => {
                        for field in &def.fields {
                            self.skip_field_with_options(bb, field, options)?;
                        }
                    }

                    DefKind::Message => loop {
                        let value = bb.read_var_uint()?;
                        if value == 0 {
                            break;
                        }
                        if let Some(index) = def.field_value_to_index.get(&value) {
                            self.skip_field_with_options(bb, &def.fields[*index], options)?;
                        } else {
                            return Err(());
                        }
                    },
                }
            }
        }

        Ok(())
    }

    pub fn skip(&self, bb: &mut ByteBuffer, type_id: i32) -> Result<(), ()> {
        self.skip_with_options(
            bb,
            type_id,
            &SchemaOptions {
                validate_enums: true,
            },
        )
    }

    /// Advances the current index of the provided [ByteBuffer](struct.ByteBuffer.html)
    /// by the size of the provided field. This is used by [skip](#method.skip)
    /// but may also be useful by itself.
    pub fn skip_field_with_options(
        &self,
        bb: &mut ByteBuffer,
        field: &Field,
        options: &SchemaOptions,
    ) -> Result<(), ()> {
        if field.is_array {
            let len = bb.read_var_uint()? as usize;
            for _ in 0..len {
                self.skip_with_options(bb, field.type_id, options)?;
            }
        } else {
            self.skip_with_options(bb, field.type_id, options)?;
        }
        Ok(())
    }

    pub fn skip_field(&self, bb: &mut ByteBuffer, field: &Field) -> Result<(), ()> {
        self.skip_field_with_options(
            bb,
            field,
            &SchemaOptions {
                validate_enums: true,
            },
        )
    }
}

#[test]
fn schema_decode_and_encode() {
    // This is the encoding of the Kiwi schema "message ABC { int[] xyz = 1; }"
    let schema_bytes = [1, 65, 66, 67, 0, 2, 1, 120, 121, 122, 0, 5, 1, 1];
    let schema = Schema::decode(&schema_bytes).unwrap();
    assert_eq!(
        schema,
        Schema::new(vec![Def::new(
            "ABC".to_owned(),
            DefKind::Message,
            vec![Field {
                name: "xyz".to_owned(),
                type_id: TYPE_INT,
                is_array: true,
                value: 1
            },]
        ),])
    );
    assert_eq!(schema.encode(), schema_bytes);
}

/// This type holds dynamic Kiwi data.
///
/// Values can represent anything in a Kiwi schema and can be converted to and
/// from byte arrays using the corresponding [Schema](struct.Schema.html).
/// Enums and field names are stored using string slices from their Schema
/// for efficiency. This means that a Value can outlive the buffer it was parsed
/// from but can't outlive the schema.
#[derive(Clone, PartialEq)]
pub enum Value<'a> {
    Bool(bool),
    Byte(u8),
    Int(i32),
    UInt(u32),
    Float(f32),
    String(String),
    Int64(i64),
    UInt64(u64),
    Array(Vec<Value<'a>>),
    Enum(&'a str, &'a str),
    Object(&'a str, HashMap<&'a str, Value<'a>>),
}

impl<'a> Value<'a> {
    /// A convenience method to extract the value out of a [Bool](#variant.Bool).
    /// Returns `false` for other value kinds.
    pub fn as_bool(&self) -> bool {
        match *self {
            Value::Bool(value) => value,
            _ => false,
        }
    }

    /// A convenience method to extract the value out of a [Byte](#variant.Byte).
    /// Returns `0` for other value kinds.
    pub fn as_byte(&self) -> u8 {
        match *self {
            Value::Byte(value) => value,
            _ => 0,
        }
    }

    /// A convenience method to extract the value out of an [Int](#variant.Int).
    /// Returns `0` for other value kinds.
    pub fn as_int(&self) -> i32 {
        match *self {
            Value::Int(value) => value,
            _ => 0,
        }
    }

    /// A convenience method to extract the value out of a [UInt](#variant.UInt).
    /// Returns `0` for other value kinds.
    pub fn as_uint(&self) -> u32 {
        match *self {
            Value::UInt(value) => value,
            _ => 0,
        }
    }

    /// A convenience method to extract the value out of a [Float](#variant.Float).
    /// Returns `0.0` for other value kinds.
    pub fn as_float(&self) -> f32 {
        match *self {
            Value::Float(value) => value,
            _ => 0.0,
        }
    }

    /// A convenience method to extract the value out of a [String](#variant.String).
    /// Returns `""` for other value kinds.
    pub fn as_string(&self) -> &str {
        match *self {
            Value::String(ref value) => value.as_str(),
            _ => "",
        }
    }

    /// A convenience method to extract the length out of an [Array](#variant.Array).
    /// Returns `0` for other value kinds.
    pub fn len(&self) -> usize {
        match *self {
            Value::Array(ref values) => values.len(),
            _ => 0,
        }
    }

    /// A convenience method to append to an [Array](#variant.Array). Does
    /// nothing for other value kinds.
    pub fn push(&mut self, value: Value<'a>) {
        if let Value::Array(ref mut values) = *self {
            values.push(value);
        }
    }

    /// A convenience method to extract a field out of an [Object](#variant.Object).
    /// Returns `None` for other value kinds or if the field isn't present.
    pub fn get(&self, name: &str) -> Option<&Value<'a>> {
        match *self {
            Value::Object(_, ref fields) => fields.get(name),
            _ => None,
        }
    }

    /// A convenience method to update a field on an [Object](#variant.Object).
    /// Does nothing for other value kinds.
    pub fn set(&mut self, name: &'a str, value: Value<'a>) {
        if let Value::Object(_, ref mut fields) = *self {
            fields.insert(name, value);
        }
    }

    /// A convenience method to remove a field on an [Object](#variant.Object).
    /// Does nothing for other value kinds.
    pub fn remove(&mut self, name: &'a str) {
        if let Value::Object(_, ref mut fields) = *self {
            fields.remove(name);
        }
    }

    /// Decodes the type specified by `type_id` and `schema` from `bytes`.
    pub fn decode(schema: &'a Schema, type_id: i32, bytes: &[u8]) -> Result<Value<'a>, ()> {
        Value::decode_bb(schema, type_id, &mut ByteBuffer::new(bytes))
    }

    /// Encodes this value into an array of bytes using the provided `schema`.
    pub fn encode(&self, schema: &Schema) -> Vec<u8> {
        let mut bb = ByteBufferMut::new();
        self.encode_bb(schema, &mut bb);
        bb.data()
    }

    /// Decodes the type specified by `type_id` and `schema` from `bb` starting
    /// at the current index. After this function returns, the current index will
    /// be advanced by the amount of data that was successfully parsed. This is
    /// mainly useful as a helper routine for [decode](#method.decode), which you
    /// probably want to use instead.
    pub fn decode_bb(
        schema: &'a Schema,
        type_id: i32,
        bb: &mut ByteBuffer,
    ) -> Result<Value<'a>, ()> {
        match type_id {
            TYPE_BOOL => Ok(Value::Bool(bb.read_bool()?)),
            TYPE_BYTE => Ok(Value::Byte(bb.read_byte()?)),
            TYPE_INT => Ok(Value::Int(bb.read_var_int()?)),
            TYPE_UINT => Ok(Value::UInt(bb.read_var_uint()?)),
            TYPE_FLOAT => Ok(Value::Float(bb.read_var_float()?)),
            TYPE_STRING => Ok(Value::String(bb.read_string()?.into_owned())),
            TYPE_INT64 => Ok(Value::Int64(bb.read_var_int64()?)),
            TYPE_UINT64 => Ok(Value::UInt64(bb.read_var_uint64()?)),

            _ => {
                let def = &schema.defs[type_id as usize];

                match def.kind {
                    DefKind::Enum => {
                        if let Some(index) = def.field_value_to_index.get(&bb.read_var_uint()?) {
                            Ok(Value::Enum(
                                def.name.as_str(),
                                def.fields[*index].name.as_str(),
                            ))
                        } else {
                            Err(())
                        }
                    }

                    DefKind::Struct => {
                        let mut fields = HashMap::new();
                        for field in &def.fields {
                            fields.insert(
                                field.name.as_str(),
                                Value::decode_field_bb(schema, field, bb)?,
                            );
                        }
                        Ok(Value::Object(def.name.as_str(), fields))
                    }

                    DefKind::Message => {
                        let mut fields = HashMap::new();
                        loop {
                            let value = bb.read_var_uint()?;
                            if value == 0 {
                                return Ok(Value::Object(def.name.as_str(), fields));
                            }
                            if let Some(index) = def.field_value_to_index.get(&value) {
                                let field = &def.fields[*index];
                                fields.insert(
                                    field.name.as_str(),
                                    Value::decode_field_bb(schema, field, bb)?,
                                );
                            } else {
                                return Err(());
                            }
                        }
                    }
                }
            }
        }
    }

    /// Decodes the field specified by `field` and `schema` from `bb` starting
    /// at the current index. This is used by [decode_bb](#method.decode_bb) but
    /// may also be useful by itself.
    pub fn decode_field_bb(
        schema: &'a Schema,
        field: &Field,
        bb: &mut ByteBuffer,
    ) -> Result<Value<'a>, ()> {
        if field.is_array {
            let len = bb.read_var_uint()? as usize;
            let mut array = Vec::with_capacity(len);
            for _ in 0..len {
                array.push(Value::decode_bb(schema, field.type_id, bb)?);
            }
            Ok(Value::Array(array))
        } else {
            Value::decode_bb(schema, field.type_id, bb)
        }
    }

    /// Encodes the current value to the end of `bb` using the provided `schema`.
    /// This is mainly useful as a helper routine for [encode](#method.encode),
    /// which you probably want to use instead.
    pub fn encode_bb(&self, schema: &Schema, bb: &mut ByteBufferMut) {
        match *self {
            Value::Bool(value) => bb.write_byte(if value { 1 } else { 0 }),
            Value::Byte(value) => bb.write_byte(value),
            Value::Int(value) => bb.write_var_int(value),
            Value::UInt(value) => bb.write_var_uint(value),
            Value::Float(value) => bb.write_var_float(value),
            Value::String(ref value) => bb.write_string(value.as_str()),
            Value::Int64(value) => bb.write_var_int64(value),
            Value::UInt64(value) => bb.write_var_uint64(value),

            Value::Array(ref values) => {
                bb.write_var_uint(values.len() as u32);
                for value in values {
                    value.encode_bb(schema, bb);
                }
                return;
            }

            Value::Enum(name, value) => {
                let def = &schema.defs[*schema.def_name_to_index.get(name).unwrap()];
                let index = *def.field_name_to_index.get(value).unwrap();
                bb.write_var_uint(def.fields[index].value);
            }

            Value::Object(name, ref fields) => {
                let def = &schema.defs[*schema.def_name_to_index.get(name).unwrap()];
                match def.kind {
                    DefKind::Enum => panic!(),
                    DefKind::Struct => {
                        for field in &def.fields {
                            fields
                                .get(field.name.as_str())
                                .unwrap()
                                .encode_bb(schema, bb);
                        }
                    }
                    DefKind::Message => {
                        // Loop over all fields to ensure consistent encoding order
                        for field in &def.fields {
                            if let Some(value) = fields.get(field.name.as_str()) {
                                bb.write_var_uint(field.value);
                                value.encode_bb(schema, bb);
                            }
                        }
                        bb.write_byte(0);
                    }
                }
            }
        }
    }
}

impl<'a> Index<usize> for Value<'a> {
    type Output = Value<'a>;

    /// A convenience method that adds support for `self[index]` expressions.
    /// It will panic if this value isn't an [Array](#variant.Array) or if the
    /// provided index is out of bounds.
    fn index(&self, index: usize) -> &Value<'a> {
        match *self {
            Value::Array(ref values) => &values[index],
            _ => panic!(),
        }
    }
}

impl<'a> fmt::Debug for Value<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        match *self {
            Value::Bool(value) => value.fmt(f),
            Value::Byte(value) => value.fmt(f),
            Value::Int(value) => value.fmt(f),
            Value::UInt(value) => value.fmt(f),
            Value::Float(value) => value.fmt(f),
            Value::String(ref value) => value.fmt(f),
            Value::Int64(value) => value.fmt(f),
            Value::UInt64(value) => value.fmt(f),
            Value::Array(ref values) => values.fmt(f),
            Value::Enum(name, ref value) => write!(f, "{}::{}", name, value),

            Value::Object(name, ref fields) => {
                let mut keys: Vec<_> = fields.keys().collect();
                let mut first = true;
                keys.sort();
                write!(f, "{} {{", name)?;

                for key in keys {
                    if first {
                        first = false;
                    } else {
                        write!(f, ", ")?;
                    }
                    write!(f, "{}: {:?}", key, fields[key])?;
                }

                write!(f, "}}")
            }
        }
    }
}

#[test]
fn value_basic() {
    let value = Value::Array(vec![
        Value::Bool(true),
        Value::Byte(255),
        Value::Int(-1),
        Value::UInt(1),
        Value::Float(0.5),
        Value::String("abc".to_owned()),
        Value::Enum("Foo", "FOO"),
        Value::Object("Obj", {
            let mut map = HashMap::new();
            map.insert("key1", Value::String("value1".to_owned()));
            map.insert("key2", Value::String("value2".to_owned()));
            map
        }),
    ]);

    assert_eq!(value.len(), 8);

    assert_eq!(value[0], Value::Bool(true));
    assert_eq!(value[1], Value::Byte(255));
    assert_eq!(value[2], Value::Int(-1));
    assert_eq!(value[3], Value::UInt(1));
    assert_eq!(value[4], Value::Float(0.5));
    assert_eq!(value[5], Value::String("abc".to_owned()));
    assert_eq!(value[6], Value::Enum("Foo", "FOO"));
    assert_eq!(
        value[7],
        Value::Object("Obj", {
            let mut map = HashMap::new();
            map.insert("key1", Value::String("value1".to_owned()));
            map.insert("key2", Value::String("value2".to_owned()));
            map
        })
    );

    assert_eq!(value[0].as_bool(), true);
    assert_eq!(value[1].as_byte(), 255);
    assert_eq!(value[2].as_int(), -1);
    assert_eq!(value[3].as_uint(), 1);
    assert_eq!(value[4].as_float(), 0.5);
    assert_eq!(value[5].as_string(), "abc");
    assert_eq!(value.get("key1"), None);
    assert_eq!(
        value[7].get("key1"),
        Some(&Value::String("value1".to_owned()))
    );

    assert_eq!(
        format!("{:?}", value),
        "[true, 255, -1, 1, 0.5, \"abc\", Foo::FOO, Obj {key1: \"value1\", key2: \"value2\"}]"
    );
}

#[test]
fn value_push() {
    let mut value = Value::Array(vec![]);
    assert_eq!(value.len(), 0);

    value.push(Value::Int(123));
    assert_eq!(value.len(), 1);
    assert_eq!(value[0], Value::Int(123));

    value.push(Value::Int(456));
    assert_eq!(value.len(), 2);
    assert_eq!(value[0], Value::Int(123));
    assert_eq!(value[1], Value::Int(456));
}

#[test]
fn value_set() {
    let mut value = Value::Object("Foo", HashMap::new());
    assert_eq!(value.get("x"), None);

    value.set("x", Value::Int(123));
    assert_eq!(value.get("x"), Some(&Value::Int(123)));

    value.set("y", Value::Int(456));
    assert_eq!(value.get("x"), Some(&Value::Int(123)));
    assert_eq!(value.get("y"), Some(&Value::Int(456)));

    value.set("x", Value::Int(789));
    assert_eq!(value.get("x"), Some(&Value::Int(789)));
    assert_eq!(value.get("y"), Some(&Value::Int(456)));
}

#[test]
fn value_remove() {
    let mut value = Value::Object("Foo", HashMap::new());
    assert_eq!(value.get("x"), None);

    value.set("x", Value::Int(123));
    assert_eq!(value.get("x"), Some(&Value::Int(123)));

    value.set("y", Value::Int(456));
    assert_eq!(value.get("x"), Some(&Value::Int(123)));
    assert_eq!(value.get("y"), Some(&Value::Int(456)));

    value.remove("x");
    assert_eq!(value.get("x"), None);
    assert_eq!(value.get("y"), Some(&Value::Int(456)));

    value.remove("y");
    assert_eq!(value.get("x"), None);
    assert_eq!(value.get("y"), None);
}

#[test]
fn value_encode_and_decode() {
    let schema = Schema::new(vec![
        Def::new(
            "Enum".to_owned(),
            DefKind::Enum,
            vec![
                Field {
                    name: "FOO".to_owned(),
                    type_id: 0,
                    is_array: false,
                    value: 100,
                },
                Field {
                    name: "BAR".to_owned(),
                    type_id: 0,
                    is_array: false,
                    value: 200,
                },
            ],
        ),
        Def::new(
            "Struct".to_owned(),
            DefKind::Struct,
            vec![
                Field {
                    name: "v_enum".to_owned(),
                    type_id: 0,
                    is_array: true,
                    value: 0,
                },
                Field {
                    name: "v_message".to_owned(),
                    type_id: 2,
                    is_array: false,
                    value: 0,
                },
            ],
        ),
        Def::new(
            "Message".to_owned(),
            DefKind::Message,
            vec![
                Field {
                    name: "v_bool".to_owned(),
                    type_id: TYPE_BOOL,
                    is_array: false,
                    value: 1,
                },
                Field {
                    name: "v_byte".to_owned(),
                    type_id: TYPE_BYTE,
                    is_array: false,
                    value: 2,
                },
                Field {
                    name: "v_int".to_owned(),
                    type_id: TYPE_INT,
                    is_array: false,
                    value: 3,
                },
                Field {
                    name: "v_uint".to_owned(),
                    type_id: TYPE_UINT,
                    is_array: false,
                    value: 4,
                },
                Field {
                    name: "v_float".to_owned(),
                    type_id: TYPE_FLOAT,
                    is_array: false,
                    value: 5,
                },
                Field {
                    name: "v_string".to_owned(),
                    type_id: TYPE_STRING,
                    is_array: false,
                    value: 6,
                },
                Field {
                    name: "v_int64".to_owned(),
                    type_id: TYPE_INT64,
                    is_array: false,
                    value: 7,
                },
                Field {
                    name: "v_uint64".to_owned(),
                    type_id: TYPE_UINT64,
                    is_array: false,
                    value: 8,
                },
                Field {
                    name: "v_enum".to_owned(),
                    type_id: 0,
                    is_array: false,
                    value: 9,
                },
                Field {
                    name: "v_struct".to_owned(),
                    type_id: 1,
                    is_array: false,
                    value: 10,
                },
                Field {
                    name: "v_message".to_owned(),
                    type_id: 2,
                    is_array: false,
                    value: 11,
                },
                Field {
                    name: "a_bool".to_owned(),
                    type_id: TYPE_BOOL,
                    is_array: true,
                    value: 12,
                },
                Field {
                    name: "a_byte".to_owned(),
                    type_id: TYPE_BYTE,
                    is_array: true,
                    value: 13,
                },
                Field {
                    name: "a_int".to_owned(),
                    type_id: TYPE_INT,
                    is_array: true,
                    value: 14,
                },
                Field {
                    name: "a_uint".to_owned(),
                    type_id: TYPE_UINT,
                    is_array: true,
                    value: 15,
                },
                Field {
                    name: "a_float".to_owned(),
                    type_id: TYPE_FLOAT,
                    is_array: true,
                    value: 16,
                },
                Field {
                    name: "a_string".to_owned(),
                    type_id: TYPE_STRING,
                    is_array: true,
                    value: 17,
                },
                Field {
                    name: "a_int64".to_owned(),
                    type_id: TYPE_INT64,
                    is_array: true,
                    value: 18,
                },
                Field {
                    name: "a_uint64".to_owned(),
                    type_id: TYPE_UINT64,
                    is_array: true,
                    value: 19,
                },
                Field {
                    name: "a_enum".to_owned(),
                    type_id: 0,
                    is_array: true,
                    value: 20,
                },
                Field {
                    name: "a_struct".to_owned(),
                    type_id: 1,
                    is_array: true,
                    value: 21,
                },
                Field {
                    name: "a_message".to_owned(),
                    type_id: 2,
                    is_array: true,
                    value: 22,
                },
            ],
        ),
    ]);

    assert!(Schema::decode(&schema.encode()).is_ok());

    assert_eq!(
        Value::decode(&schema, TYPE_BOOL, &[0]),
        Ok(Value::Bool(false))
    );
    assert_eq!(
        Value::decode(&schema, TYPE_BOOL, &[1]),
        Ok(Value::Bool(true))
    );
    assert_eq!(Value::decode(&schema, TYPE_BOOL, &[2]), Err(()));
    assert_eq!(
        Value::decode(&schema, TYPE_BYTE, &[255]),
        Ok(Value::Byte(255))
    );
    assert_eq!(Value::decode(&schema, TYPE_INT, &[1]), Ok(Value::Int(-1)));
    assert_eq!(Value::decode(&schema, TYPE_UINT, &[1]), Ok(Value::UInt(1)));
    assert_eq!(
        Value::decode(&schema, TYPE_FLOAT, &[126, 0, 0, 0]),
        Ok(Value::Float(0.5))
    );
    assert_eq!(
        Value::decode(&schema, TYPE_STRING, &[240, 159, 141, 149, 0]),
        Ok(Value::String("🍕".to_owned()))
    );
    assert_eq!(
        Value::decode(&schema, TYPE_INT64, &[1]),
        Ok(Value::Int64(-1))
    );
    assert_eq!(
        Value::decode(&schema, TYPE_UINT64, &[1]),
        Ok(Value::UInt64(1))
    );
    assert_eq!(Value::decode(&schema, 0, &[0]), Err(()));
    assert_eq!(
        Value::decode(&schema, 0, &[100]),
        Ok(Value::Enum("Enum", "FOO"))
    );
    assert_eq!(
        Value::decode(&schema, 0, &[200, 1]),
        Ok(Value::Enum("Enum", "BAR"))
    );

    assert_eq!(Value::Bool(false).encode(&schema), [0]);
    assert_eq!(Value::Bool(true).encode(&schema), [1]);
    assert_eq!(Value::Byte(255).encode(&schema), [255]);
    assert_eq!(Value::Int(-1).encode(&schema), [1]);
    assert_eq!(Value::UInt(1).encode(&schema), [1]);
    assert_eq!(Value::Float(0.5).encode(&schema), [126, 0, 0, 0]);
    assert_eq!(
        Value::String("🍕".to_owned()).encode(&schema),
        [240, 159, 141, 149, 0]
    );
    assert_eq!(Value::Int64(-1).encode(&schema), [1]);
    assert_eq!(Value::UInt64(1).encode(&schema), [1]);
    assert_eq!(Value::Enum("Enum", "FOO").encode(&schema), [100]);
    assert_eq!(Value::Enum("Enum", "BAR").encode(&schema), [200, 1]);

    fn insert<'a>(
        mut map: HashMap<&'a str, Value<'a>>,
        key: &'a str,
        value: Value<'a>,
    ) -> HashMap<&'a str, Value<'a>> {
        map.insert(key, value);
        map
    }

    let empty_struct = Value::Object(
        "Struct",
        insert(
            insert(HashMap::new(), "v_enum", Value::Array(vec![])),
            "v_message",
            Value::Object("Message", HashMap::new()),
        ),
    );

    assert_eq!(Value::decode(&schema, 1, &[0, 0]), Ok(empty_struct.clone()));
    assert_eq!(empty_struct.encode(&schema), [0, 0]);

    let full_struct = Value::Object(
        "Struct",
        insert(
            insert(
                HashMap::new(),
                "v_enum",
                Value::Array(vec![Value::Enum("Enum", "FOO"), Value::Enum("Enum", "BAR")]),
            ),
            "v_message",
            Value::Object(
                "Message",
                insert(HashMap::new(), "v_string", Value::String("🍕".to_owned())),
            ),
        ),
    );

    assert_eq!(
        Value::decode(&schema, 1, &[2, 100, 200, 1, 6, 240, 159, 141, 149, 0, 0]),
        Ok(full_struct.clone())
    );
    assert_eq!(
        full_struct.encode(&schema),
        [2, 100, 200, 1, 6, 240, 159, 141, 149, 0, 0]
    );

    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_bool", Value::Bool(false))
        )
        .encode(&schema),
        [1, 0, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_bool", Value::Bool(true))
        )
        .encode(&schema),
        [1, 1, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_byte", Value::Byte(255))
        )
        .encode(&schema),
        [2, 255, 0]
    );
    assert_eq!(
        Value::Object("Message", insert(HashMap::new(), "v_int", Value::Int(-1))).encode(&schema),
        [3, 1, 0]
    );
    assert_eq!(
        Value::Object("Message", insert(HashMap::new(), "v_uint", Value::UInt(1))).encode(&schema),
        [4, 1, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_float", Value::Float(0.0))
        )
        .encode(&schema),
        [5, 0, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_string", Value::String("".to_owned()))
        )
        .encode(&schema),
        [6, 0, 0]
    );
    assert_eq!(
        Value::Object("Message", insert(HashMap::new(), "v_int64", Value::Int(-1))).encode(&schema),
        [7, 1, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_uint64", Value::UInt(1))
        )
        .encode(&schema),
        [8, 1, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_enum", Value::Enum("Enum", "FOO"))
        )
        .encode(&schema),
        [9, 100, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(HashMap::new(), "v_struct", empty_struct.clone())
        )
        .encode(&schema),
        [10, 0, 0, 0]
    );
    assert_eq!(
        Value::Object(
            "Message",
            insert(
                HashMap::new(),
                "v_message",
                Value::Object("Message", HashMap::new())
            )
        )
        .encode(&schema),
        [11, 0, 0]
    );

    assert_eq!(
        Value::decode(&schema, 2, &[1, 0, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_bool", Value::Bool(false))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[1, 1, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_bool", Value::Bool(true))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[2, 255, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_byte", Value::Byte(255))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[3, 1, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_int", Value::Int(-1))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[4, 1, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_uint", Value::UInt(1))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[5, 0, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_float", Value::Float(0.0))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[6, 0, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_string", Value::String("".to_owned()))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[7, 1, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_int64", Value::Int64(-1))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[8, 1, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_uint64", Value::UInt64(1))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[9, 100, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_enum", Value::Enum("Enum", "FOO"))
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[10, 0, 0, 0]),
        Ok(Value::Object(
            "Message",
            insert(HashMap::new(), "v_struct", empty_struct.clone())
        ))
    );
    assert_eq!(
        Value::decode(&schema, 2, &[11, 0, 0]),
        Ok(Value::Object(
            "Message",
            insert(
                HashMap::new(),
                "v_message",
                Value::Object("Message", HashMap::new())
            )
        ))
    );
}

// This test case is for a bug where rustc was silently inferring an incorrect
// lifetime. This is the specific error:
//
//   error[E0597]: `value` does not live long enough
//       --> src/lib.rs:1307:40
//        |
//   1307 |     if let Some(Value::Array(items)) = value.get("items") {
//        |                                        ^^^^^ borrowed value does not live long enough
//   ...
//   1312 |   }
//        |   - borrowed value only lives until here
//        |
//        = note: borrowed value must be valid for the static lifetime...
//
// The fix was to change this:
//
//   pub fn get(&self, name: &str) -> Option<&Value> {
//
// Into this:
//
//   pub fn get(&self, name: &str) -> Option<&Value<'a>> {
//
#[test]
fn value_get_bad_lifetime_inference_in_rustc() {
    fn use_item<'a>(_: &'a Value<'static>) {}

    fn use_items(value: Value<'static>) {
        if let Some(Value::Array(items)) = value.get("items") {
            for item in items {
                use_item(item);
            }
        }
    }

    use_items(Value::Array(vec![]));
}