//! Fast and easy bitfield proc macro
//!
//! Provides a proc macro for compressing a data structure with data which can be expressed with bit
//! lengths that are not a power of Two.
//!
//! # Derive Bitfields
//! - Implements the [`Bitfields`](https://docs.rs/bondrewd/latest/bondrewd/trait.Bitfields.html) trait
//! which offers from\into bytes functions that are non-failable and convert the struct from/into sized
//! u8 arrays ([u8; {total_bit_length * 8}]).
//! - `read` and `write` functions that allow the field to be accessed or overwritten within a sized u8 array.
//! - More information about how each field is handled (bit length, endianness, ..), as well as structure
//! wide effects (bit position, default field endianness, ..), can be found on the
//! [`Bitfields Derive`](Bitfields) page.
//!
//! For example we can define a data structure with 7 total bytes as:
//! - A boolean field named one will be the first bit.
//! - A floating point field named two will be the next 32 bits. floats must be full sized
//! currently.
//! - A signed integer field named three will be the next 14 bits.
//! - An unsigned integer field named four will be the next 6 bits.
//!
//! ```
//! // Users code
//! use bondrewd::*;
//! #[derive(Bitfields)]
//! #[bondrewd(default_endianness = "be")]
//! struct SimpleExample {
//!     // fields that are as expected do not require attributes.
//!     one: bool,
//!     two: f32,
//!     #[bondrewd(bit_length = 14)]
//!     three: i16,
//!     #[bondrewd(bit_length = 6)]
//!     four: u8,
//! }
//! ```
//! Generated Code with function logic omitted. [Full Generated Code](#full-example-generated-code)
//! ```compile_fail
//! impl Bitfields<7usize> for SimpleExample {
//!     const BIT_SIZE: usize = 53usize;
//!     fn into_bytes(self) -> [u8; 7usize] { .. }
//!     fn from_bytes(mut input_byte_buffer: [u8; 7usize]) -> Self { .. }
//! }
//! impl SimpleExample {
//!     pub fn read_one(input_byte_buffer: &[u8; 7usize]) -> bool { .. }
//!     pub fn read_two(input_byte_buffer: &[u8; 7usize]) -> f32 { .. }
//!     pub fn read_three(input_byte_buffer: &[u8; 7usize]) -> i16 { .. }
//!     pub fn read_four(input_byte_buffer: &[u8; 7usize]) -> u8 { .. }
//!     pub fn write_one(output_byte_buffer: &mut [u8; 7usize], mut one: bool) { .. }
//!     pub fn write_two(output_byte_buffer: &mut [u8; 7usize], mut two: f32) { .. }
//!     pub fn write_three(output_byte_buffer: &mut [u8; 7usize], mut three: i16) { .. }
//!     pub fn write_four(output_byte_buffer: &mut [u8; 7usize], mut four: u8) { .. }
//! }
//! ```
//! # Derive BitfieldEnum
//! - Implements the [`BitfieldEnum`](https://docs.rs/bondrewd/latest/bondrewd/trait.BitfieldEnum.html)
//! trait which offers from\into primitive functions that are non-failable and convert the enum from/into
//! a primitive type (u8 is the only currently testing primitive).
//! - More information about controlling the end result (define variant values, define a catch/invalid
//! variant) can be found on the [`BitfieldEnum Derive`](BitfieldEnum) page.
//!
//! ```
//! // Users code
//! use bondrewd::BitfieldEnum;
//! #[derive(BitfieldEnum)]
//! enum SimpleEnum {
//!     Zero,
//!     One,
//!     Six = 6,
//!     Two,
//! }
//! ```
//! Full Generated Struct Code
//! ```
//! # use bondrewd::BitfieldEnum;
//! # enum SimpleEnum {
//! #     Zero,
//! #     One,
//! #     Six = 6,
//! #     Two,
//! # }
//! // use statement and SimpleEnum definition are hidden.
//! impl bondrewd::BitfieldEnum for SimpleEnum {
//!     type Primitive = u8;
//!     fn into_primitive(self) -> u8 {
//!         match self {
//!             Self::Zero => 0,
//!             Self::One => 1,
//!             Self::Six => 6,
//!             Self::Two => 2,
//!         }
//!     }
//!     fn from_primitive(input: u8) -> Self {
//!         match input {
//!             0 => Self::Zero,
//!             1 => Self::One,
//!             6 => Self::Six,
//!             _ => Self::Two,
//!         }
//!     }
//! }
//! ```
//!
//! # Crate Features
//! Slice functions are convenience functions for reading/wring single or multiple fields without reading
//! the entire structure. Bondrewd will provided 2 ways to access the field:
//! * Single field access. These are functions that are added along side the standard read/write field
//! functions in the impl for the input structure. read/write slice functions will check the length of
//! the slice to insure the amount to bytes needed for the field (NOT the entire structure) are present and
//! return BitfieldSliceError if not enough bytes are present.
//!     * `fn read_slice_{field}(&[u8]) -> Result<{field_type}, bondrewd::BondrewdSliceError> { .. }`
//!     * `fn write_slice_{field}(&mut [u8], {field_type}) -> Result<(), bondrewd::BondrewdSliceError> { .. }`
//! * Multiple field access.
//!     * `fn check_slice(&[u8]) -> Result<{struct_name}Checked, bondrewd::BondrewdSliceError> { .. }`
//!       This function will check the size of the slice, if the slice is big enough it will return
//!       a checked structure. the structure will be the same name as the input structure with
//!       "Checked" tacked onto the end. the Checked Structure will have getters for each of the input
//!       structures fields, the naming is the same as the standard `read_{field}` functions.
//!         * `fn read_{field}(&self) -> {field_type} { .. }`
//!     * `fn check_slice_mut(&mut [u8]) -> Result<{struct_name}CheckedMut, bondrewd::BondrewdSliceError> { .. }`
//!       This function will check the size of the slice, if the slice is big enough it will return
//!       a checked structure. the structure will be the same name as the input structure with
//!       "CheckedMut" tacked onto the end. the Checked Structure will have getters and setters for each
//!       of the input structures fields, the naming is the same as the standard `read_{field}` and
//!       `write_{field}` functions.
//!         * `fn read_{field}(&self) -> {field_type} { .. }`
//!         * `fn write_{field}(&mut self) -> {field_type} { .. }`
//!   
//! Example Cargo.toml Bondrewd dependency  
//! `bondrewd = { version = "^0.1", features = ["derive", "slice_fns"] }`  
//! Example Generated Slice Api:
//! ```compile_fail
//! impl Simple {
//!     pub fn check_slice(buffer: &[u8]) -> Result<SimpleChecked, BitfieldSliceError> { .. }
//!     pub fn check_slice_mut(buffer: &mut [u8]) -> Result<SimpleCheckedMut, BitfieldSliceError> { .. }
//!     #[inline]
//!     pub fn read_slice_one(input_byte_buffer: &[u8]) -> Result<u8, BitfieldSliceError> { .. }
//!     #[inline]
//!     pub fn read_slice_two(input_byte_buffer: &[u8]) -> Result<bool, BitfieldSliceError> { .. }
//!     #[inline]
//!     pub fn read_slice_three(input_byte_buffer: &[u8]) -> Result<u8, BitfieldSliceError> { .. }
//!     #[inline]
//!     pub fn write_slice_one(output_byte_buffer: &mut [u8],one: u8) -> Result<(), BitfieldSliceError> { .. }
//!     #[inline]
//!     pub fn write_slice_two(output_byte_buffer: &mut [u8],two: bool) -> Result<(), BitfieldSliceError> { .. }
//!     #[inline]
//!     pub fn write_slice_three(output_byte_buffer: &mut [u8],three: u8) -> Result<(), BitfieldSliceError> { .. }
//! }
//! struct SimpleChecked<'a> {
//!     buffer: &'a [u8],
//! }
//! impl<'a> SimpleChecked<'a> {
//!     #[inline]
//!     pub fn read_one(&self) -> u8 { .. }
//!     #[inline]
//!     pub fn read_two(&self) -> bool { .. }
//!     #[inline]
//!     pub fn read_three(&self) -> u8 { .. }
//! }
//! struct SimpleCheckedMut<'a> {
//!     buffer: &'a mut [u8],
//! }
//! impl<'a> SimpleCheckedMut<'a> {
//!     #[inline]
//!     pub fn read_one(&self) -> u8 { .. }
//!     #[inline]
//!     pub fn read_two(&self) -> bool { .. }
//!     #[inline]
//!     pub fn read_three(&self) -> u8 { .. }
//!     #[inline]
//!     pub fn write_one(&mut self, one: u8) { .. }
//!     #[inline]
//!     pub fn write_two(&mut self, two: bool) { .. }
//!     #[inline]
//!     pub fn write_three(&mut self, three: u8) { .. }
//! }
//! ```
//! 
//! `hex_fns` provided from/into hex functions like from/into bytes. The hex inputs/outputs are \[u8;N\]
//! where N is double the calculated bondrewd STRUCT_SIZE. Hex encoding and decoding is based off the
//! [hex](https://crates.io/crates/hex) crate's from/into slice functions but with statically sized
//! arrays so we could eliminate sizing errors.
//!
//! ### Full Example Generated Code
//! ```
//! use bondrewd::*;
//! struct SimpleExample {
//!     one: bool,
//!     two: f32,
//!     three: i16,
//!     four: u8,
//! }
//! impl Bitfields<7usize> for SimpleExample {
//!     const BIT_SIZE: usize = 53usize;
//!     fn into_bytes(self) -> [u8; 7usize] {
//!         let mut output_byte_buffer: [u8; 7usize] = [0u8; 7usize];
//!         let one = self.one;
//!         output_byte_buffer[0usize] |= ((one as u8) << 7usize) & 128u8;
//!         let two = self.two;
//!         let two_bytes = (two.to_bits().rotate_right(1u32)).to_be_bytes();
//!         output_byte_buffer[0usize] |= two_bytes[0usize] & 127u8;
//!         output_byte_buffer[1usize] |= two_bytes[1usize];
//!         output_byte_buffer[2usize] |= two_bytes[2usize];
//!         output_byte_buffer[3usize] |= two_bytes[3usize];
//!         output_byte_buffer[4usize] |= two_bytes[0] & 128u8;
//!         let three = self.three;
//!         let three_bytes = (three.rotate_right(7u32)).to_be_bytes();
//!         output_byte_buffer[4usize] |= three_bytes[1usize] & 127u8;
//!         output_byte_buffer[5usize] |= three_bytes[0] & 254u8;
//!         let four = self.four;
//!         let four_bytes = (four.rotate_right(5u32)).to_be_bytes();
//!         output_byte_buffer[5usize] |= four_bytes[0usize] & 1u8;
//!         output_byte_buffer[6usize] |= four_bytes[0] & 248u8;
//!         output_byte_buffer
//!     }
//!     fn from_bytes(mut input_byte_buffer: [u8; 7usize]) -> Self {
//!         let one = Self::read_one(&input_byte_buffer);
//!         let two = Self::read_two(&input_byte_buffer);
//!         let three = Self::read_three(&input_byte_buffer);
//!         let four = Self::read_four(&input_byte_buffer);
//!         Self {
//!             one,
//!             two,
//!             three,
//!             four,
//!         }
//!     }
//! }
//! impl SimpleExample {
//!     #[inline]
//!     pub fn read_one(input_byte_buffer: &[u8; 7usize]) -> bool {
//!         ((input_byte_buffer[0usize] & 128u8) != 0)
//!     }
//!     #[inline]
//!     pub fn read_two(input_byte_buffer: &[u8; 7usize]) -> f32 {
//!         f32::from_bits(
//!             u32::from_be_bytes({
//!                 let mut two_bytes: [u8; 4usize] = [0u8; 4usize];
//!                 two_bytes[0usize] |= input_byte_buffer[0usize] & 127u8;
//!                 two_bytes[1usize] |= input_byte_buffer[1usize];
//!                 two_bytes[2usize] |= input_byte_buffer[2usize];
//!                 two_bytes[3usize] |= input_byte_buffer[3usize];
//!                 two_bytes[0] |= input_byte_buffer[4usize] & 128u8;
//!                 two_bytes
//!             })
//!             .rotate_left(1u32),
//!         )
//!     }
//!     #[inline]
//!     pub fn read_three(input_byte_buffer: &[u8; 7usize]) -> i16 {
//!         i16::from_be_bytes({
//!             let mut three_bytes: [u8; 2usize] = if (input_byte_buffer[4usize] & 64u8) == 64u8 {
//!                 [1u8, 128u8]
//!             } else {
//!                 [0u8; 2usize]
//!             };
//!             three_bytes[1usize] |= input_byte_buffer[4usize] & 127u8;
//!             three_bytes[0] |= input_byte_buffer[5usize] & 254u8;
//!             three_bytes
//!         })
//!         .rotate_left(7u32)
//!     }
//!     #[inline]
//!     pub fn read_four(input_byte_buffer: &[u8; 7usize]) -> u8 {
//!         u8::from_be_bytes({
//!             let mut four_bytes: [u8; 1usize] = [0u8; 1usize];
//!             four_bytes[0usize] |= input_byte_buffer[5usize] & 1u8;
//!             four_bytes[0] |= input_byte_buffer[6usize] & 248u8;
//!             four_bytes
//!         })
//!         .rotate_left(5u32)
//!     }
//!     #[inline]
//!     pub fn write_one(output_byte_buffer: &mut [u8; 7usize], mut one: bool) {
//!         output_byte_buffer[0usize] &= 127u8;
//!         output_byte_buffer[0usize] |= ((one as u8) << 7usize) & 128u8;
//!     }
//!     #[inline]
//!     pub fn write_two(output_byte_buffer: &mut [u8; 7usize], mut two: f32) {
//!         output_byte_buffer[0usize] &= 128u8;
//!         output_byte_buffer[1usize] = 0u8;
//!         output_byte_buffer[2usize] = 0u8;
//!         output_byte_buffer[3usize] = 0u8;
//!         output_byte_buffer[4usize] &= 127u8;
//!         let two_bytes = (two.to_bits().rotate_right(1u32)).to_be_bytes();
//!         output_byte_buffer[0usize] |= two_bytes[0usize] & 127u8;
//!         output_byte_buffer[1usize] |= two_bytes[1usize];
//!         output_byte_buffer[2usize] |= two_bytes[2usize];
//!         output_byte_buffer[3usize] |= two_bytes[3usize];
//!         output_byte_buffer[4usize] |= two_bytes[0] & 128u8;
//!     }
//!     #[inline]
//!     pub fn write_three(output_byte_buffer: &mut [u8; 7usize], mut three: i16) {
//!         output_byte_buffer[4usize] &= 128u8;
//!         output_byte_buffer[5usize] &= 1u8;
//!         let three_bytes = (three.rotate_right(7u32)).to_be_bytes();
//!         output_byte_buffer[4usize] |= three_bytes[1usize] & 127u8;
//!         output_byte_buffer[5usize] |= three_bytes[0] & 254u8;
//!     }
//!     #[inline]
//!     pub fn write_four(output_byte_buffer: &mut [u8; 7usize], mut four: u8) {
//!         output_byte_buffer[5usize] &= 254u8;
//!         output_byte_buffer[6usize] &= 7u8;
//!         let four_bytes = (four.rotate_right(5u32)).to_be_bytes();
//!         output_byte_buffer[5usize] |= four_bytes[0usize] & 1u8;
//!         output_byte_buffer[6usize] |= four_bytes[0] & 248u8;
//!     }
//! }
//! ```
extern crate proc_macro;
mod enums;
use enums::parse::EnumInfo;
mod structs;
use structs::common::StructInfo;
use structs::from_bytes::create_from_bytes_field_quotes;
use structs::into_bytes::create_into_bytes_field_quotes;

use proc_macro::TokenStream;
use quote::{format_ident, quote};
use syn::{parse_macro_input, DeriveInput};

/// Generates an implementation of the bondrewd::Bitfield trait, as well as peek and set functions for direct
/// sized u8 arrays access. This crate is designed so that attributes are only required for fields that
/// are not what you would expect without the attribute. For example if you provide a u8 fields with no 
/// attributes, the field would be assumed to be the next 8 bits after the field before it. If a field 
/// of bool type without attributes is defined, the field would be assumed to be the next bit after
/// the field before it.
///
/// # Supported Field Types
/// - All primitives other than usize and isize (i believe ambiguous sizing is bad for this type of work).
///     - Floats currently must be full sized.
///     - Its important to know that there is a small runtime cost for signed numbers.
/// - Enums which implement the BitfieldEnum trait in Bondrewd.
/// - Structs which implement the Bitfield trait in Bondrewd.
///
/// # Struct Attributes
/// - `default_endianness = {"le" or "be"}` Describes a default endianness for primitive fields. 
/// [example](#endianness-examples)
/// - `read_from = {"msb0" or "lsb0"}` Defines bit positioning. which end of the byte array to start at.
/// [example](#bit-positioning-examples)
/// - `enforce_bytes = {BYTES}` Adds a check that requires total bytes defined by fields to equal provided
/// BYTES. [example](#enforce-bits-examples)
/// - `enforce_bits = {BITS}` Adds a check that requires total bits defined by fields to equal provided
/// BITS. [example](#enforce-bits-examples)
/// - `enforce_full_bytes` Adds a check that requires total bits defined by fields to equal a multiple of 8.
/// [example](#enforce-full-bytes-example)
/// - `fill_bytes = {BYTES}` Will force the output/input byte array size to be the provided SIZE amount of
/// bytes. [example](#fill-bytes-examples)
/// - `reverse` Defines that the entire byte array should be read backward (first byte index becomes last
/// byte index). This has no runtime cost. [example](#reverse-example)
///
/// # Field Attributes
/// - `bit_length = {BITS}` Define the total amount of bits to use when condensed. [example](#simple-example)
/// - `byte_length = {BYTES}` Define the total amount of bytes to use when condensed. [example](#simple-example)
/// - `endianness = {"le" or "be"}` Define per field endianess. [example](#endianness-examples)
/// - `block_bit_length = {BITS}` Describes a bit length for the entire array dropping lower indexes first.
/// [example](#bitfield-array-examples)
/// - `block_byte_length = {BYTES}` Describes a byte length for the entire array dropping lower indexes
/// first. [example](#bitfield-array-examples)
/// - `element_bit_length = {BITS}` Describes a bit length for each element of an array. (default array
/// type). [example](#bitfield-array-examples)
/// - `element_byte_length = {BYTES}` Describes a byte length for each element of an array. (default array
/// type). [example](#bitfield-array-examples)
/// - `enum_primitive = "u8"` Defines the size of the enum. the BitfieldEnum currently only supports u8.
/// [example](#enum-examples)
/// - `struct_size = {SIZE}` Defines the field as a struct which implements the Bitfield trait and the
/// BYTE_SIZE const defined in said trait. [example](#bitfield-struct-as-field-examples)
/// - `reserve` Defines that this field should be ignored in from and into bytes functions.
/// [example](#reserve-examples)
///     - reserve attribute is only supported for primitive types currently.
/// - /!Untested!\ `bits = "RANGE"` - define the bit indexes yourself rather than let the proc macro figure
/// it out. using a rust range in quotes.
/// 
/// # Simple Example
/// This example is on the front page for bondrewd-derive. Here i will be adding some asserts to show what
/// to expect.
/// I will be defining a data structure with 7 total bytes as:
/// - A boolean field named one will be the first bit.
/// - A floating point field named two will be the next 32 bits. floats must be full sized
/// currently.
/// - A signed integer field named three will be the next 14 bits.
/// - An unsigned integer field named four will be the next 6 bits.
/// - Because these fields do not add up to a power of 2 the last 3 bits will be unused.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleExample {
///     // fields that are as expected do not require attributes.
///     one: bool,
///     two: f32,
///     #[bondrewd(bit_length = 14)]
///     three: i16,
///     #[bondrewd(bit_length = 6)]
///     four: u8,
/// }
/// 
/// fn main(){
///     assert_eq!(7, SimpleExample::BYTE_SIZE);
///     assert_eq!(53, SimpleExample::BIT_SIZE);
///     let mut bytes = SimpleExample {
///         one: false,
///         two: -4.25,
///         three: -1034,
///         four: 63,
///     }.into_bytes();
///     // check the output binary is correct. (i did math by hand
///     // to get the binary). each field is separated by a underscore
///     // in the binary assert to make it easy to see.
///     assert_eq!([
///         0b0_1100000, // one_two,
///         0b01000100,  // two,
///         0b00000000,  // two,
///         0b00000000,  // two,
///         0b0_1110111, // two_three,
///         0b1110110_1, // three_four,
///         0b11111_000, // four_unused
///     ], bytes);
///     // use read functions to get the fields value without
///     // doing a from_bytes call.
///     assert_eq!(false, SimpleExample::read_one(&bytes));
///     assert_eq!(-4.25, SimpleExample::read_two(&bytes));
///     assert_eq!(-1034, SimpleExample::read_three(&bytes));
///     assert_eq!(63, SimpleExample::read_four(&bytes));
///     // overwrite the values with new ones in the byte array.
///     SimpleExample::write_one(&mut bytes, true);
///     SimpleExample::write_two(&mut bytes, 5.5);
///     SimpleExample::write_three(&mut bytes, 511);
///     SimpleExample::write_four(&mut bytes, 0);
///     // from bytes uses the read function so there is no need to
///     // assert the read functions again.
///     let reconstructed = SimpleExample::from_bytes(bytes);
///     // check the values read by from bytes and check if they are
///     // what we wrote to the bytes NOT the origanal values.
///     assert_eq!(true,reconstructed.one);
///     assert_eq!(5.5,reconstructed.two);
///     assert_eq!(511,reconstructed.three);
///     assert_eq!(0,reconstructed.four);
/// }
/// ```
/// # Reverse Example
/// Reverse simply makes Bondrewd index the bytes in the output/input buffers in the opposite order. 
/// First index becomes last index and last index becomes the first.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// struct Example {
///     one: u8,
///     two: u8,
///     three: u8,
///     four: u8,
/// }
/// 
/// #[derive(Bitfields)]
/// #[bondrewd(reverse)]
/// struct ExampleReversed {
///     one: u8,
///     two: u8,
///     three: u8,
///     four: u8,
/// }
/// 
/// fn main() {
///     let test = Example {
///         one: 0,
///         two: u8::MAX,
///         three: 0,
///         four: 0b01010101,
///     };
///     let test_reverse = ExampleReversed {
///         one: 0,
///         two: u8::MAX,
///         three: 0,
///         four: 0b01010101,
///     };
///     assert_eq!(test.into_bytes(), [0b00000000, 0b11111111, 0b000000, 0b01010101]);
///     assert_eq!(test_reverse.into_bytes(), [0b01010101, 0b000000, 0b11111111, 0b00000000]);
/// }
/// ```
/// # Bit Positioning Examples
/// Here Bit positioning will control where bit 0 is. for example if you have a field with 2 bits then
/// 2 fields with 3 bits each, bit positioning will define the direction in which it traverses bit indices,
/// so in our example if 0 is the least significant bit the first field would be the least significant bit
/// in the last index in the byte array. `msb0` is the default.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(read_from = "msb0")]
/// struct ExampleMSB {
///     #[bondrewd(bit_length = 2)]
///     one: u8,
///     #[bondrewd(bit_length = 3)]
///     two: u8,
///     #[bondrewd(bit_length = 3)]
///     three: u8,
/// }
/// 
/// #[derive(Bitfields)]
/// #[bondrewd(read_from = "lsb0")]
/// struct ExampleLSB {
///     #[bondrewd(bit_length = 2)]
///     one: u8,
///     #[bondrewd(bit_length = 3)]
///     two: u8,
///     #[bondrewd(bit_length = 3)]
///     three: u8,
/// }
/// 
/// fn main() {
///     let test_msb = ExampleMSB {
///         one: 0,
///         two: 5,
///         three: 0,
///     };
///     let test_lsb = ExampleLSB {
///         one: 0,
///         two: 5,
///         three: 0,
///     };
///     // in msb0 field one is the first 2 bits followed by field two
///     // then field three is the last 3 bits.
///     assert_eq!(test_msb.into_bytes(), [0b00_101_000]);
///     // in msb0 field three is the first 3 bits followed by field 
///     // 2 then field one being the last 2 bits
///     assert_eq!(test_lsb.into_bytes(), [0b000_101_00]);
/// }
/// ```
/// When using `reverse` and `read_from` in the same structure:
/// - `lsb0` would begin at the least significant bit in the first byte.
/// - 'msb0` would begin at the most significant bit in the last byte.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(read_from = "msb0", reverse)]
/// struct ExampleMSB {
///     #[bondrewd(bit_length = 5)]
///     one: u8,
///     #[bondrewd(bit_length = 4)]
///     two: u8,
///     #[bondrewd(bit_length = 7)]
///     three: u8,
/// }
/// 
/// #[derive(Bitfields)]
/// #[bondrewd(read_from = "lsb0", reverse)]
/// struct ExampleLSB {
///     #[bondrewd(bit_length = 5)]
///     one: u8,
///     #[bondrewd(bit_length = 4)]
///     two: u8,
///     #[bondrewd(bit_length = 7)]
///     three: u8,
/// }
/// 
/// fn main() {
///     let test_msb = ExampleMSB {
///         one: 0,
///         two: u8::MAX,
///         three: 0,
///     };
///     let test_lsb = ExampleLSB {
///         one: 0,
///         two: u8::MAX,
///         three: 0,
///     };
///     // here the 1's belong to feild two. i hope this is understandable.
///     assert_eq!(test_msb.into_bytes(), [0b10000000, 0b00000111]);
///     assert_eq!(test_lsb.into_bytes(), [0b11100000, 0b00000001]);
/// }
/// ```
/// # Endianness Examples
/// There are 2 ways to define endianess of fields that require endianness (multi-byte numbers, char, ...)
/// - Default endianness which will give provided endianness to all fields that require endianness but
/// do not have it defined.
/// - Per field endianess which defines the endianness of a particular field.
/// 
/// Default endianness and per fields endianness can also be used in the same struct
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// // tell bondrewd to default to Big Endian
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleExample {
///     // this field will be given the default endianness
///     one: u16,
///     // here we give the field endianness which means it will not use default endianness.
///     #[bondrewd(endianness = "le")]
///     two: u16,
/// }
/// 
/// fn main() {
///     let test = SimpleExample {
///         one: 5,
///         two: 5,
///     };
///     // check that each field are in the correct endianness
///     assert_eq!(test.into_bytes(),[0b00000000, 0b00000101, 0b00000101, 0b00000000]);
/// }
/// ```
/// If you define the endianness of all values that require it default_endianness is not required.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// struct SimpleExample {
///     #[bondrewd(endianness = "be")]
///     one: u16,
///     #[bondrewd(endianness = "le")]
///     two: u16,
///     // because this field does not use more than 1 byte, endianness is not required.
///     three: bool,
/// }
/// 
/// fn main() {
///     let test = SimpleExample {
///         one: 5,
///         two: 5,
///         three: true,
///     };
///     // check that each field are in the correct endianness
///     assert_eq!(test.into_bytes(),[0b00000000, 0b00000101, 0b00000101, 0b00000000, 0b10000000]);
/// }
/// ```
/// # Bitfield Struct as Field Examples
/// Inner structs must implement the 
/// [`Bitfields`](https://docs.rs/bondrewd/latest/bondrewd/trait.Bitfields.html) trait and be given the
/// `struct_size = {BYTE_SIZE}, the BYTE_SIZE being the number of bytes in the outputs byte array or 
/// value in the traits const BYTE_SIZE.
/// ```
/// // this struct uses 52 total bits which means the total BYTE_SIZE is 7.
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct Simple {
///     #[bondrewd(bit_length = 3)]
///     one: u8,
///     #[bondrewd(bit_length = 27)]
///     two: char,
///     #[bondrewd(bit_length = 14)]
///     three: u16,
///     four: i8,
/// }
///
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleWithStruct {
///     #[bondrewd(struct_size = 7)]
///     one: Simple,
///     // structs can also be used in arrays.
///     #[bondrewd(struct_size = 7)]
///     two: [Simple; 2],
/// }
/// ```
/// We can also trim the struct to a bit length, this can be very useful for struct that do not use the
/// full amount of bits available in the byte array. For example if we have a struct that uses 4 bits
/// leaving the remaining 4 bits as unused data, we can make a structure with 2 of the bits structure
/// that still only uses 1 byte.
/// ```
/// // this struct uses 4 total bits which means the total BYTE_SIZE is 1.
/// use bondrewd::*;
/// #[derive(Bitfields, Clone)]
/// #[bondrewd(default_endianness = "be")]
/// struct Simple {
///     #[bondrewd(bit_length = 2)]
///     one: u8,
///     #[bondrewd(bit_length = 2)]
///     two: u8,
/// }
///
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleWithStruct {
///     #[bondrewd(struct_size = 1, bit_length = 4)]
///     one: Simple,
///     #[bondrewd(struct_size = 1, bit_length = 4)]
///     two: Simple,
/// }
/// 
/// fn main() {
///     // SimpleWithStruct uses the amount of bits that 2
///     // Simple structures would use.
///     assert_eq!(SimpleWithStruct::BIT_SIZE, Simple::BIT_SIZE * 2);
///     // But both structures use 1 byte.
///     assert_eq!(SimpleWithStruct::BYTE_SIZE, 1);
///     assert_eq!(SimpleWithStruct::BYTE_SIZE, Simple::BYTE_SIZE);
/// }
/// ```
/// # Bitfield Array Examples
/// There are 2 types of arrays in Bondrewd:
/// - Block Arrays are "bit chucks" that define a total-used-bits amount and will drop bits starting
/// at the lowest index.
/// - Element Arrays treat each element of the array as its own field and requires a per element
/// bit-length.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleWithArray {
///     // each u8 in the array contains 4 bits of useful information.
///     #[bondrewd(element_bit_length = 4)]
///     one: [u8; 4],
///     // due to no attributes being present for field `two`, 
///     // no bits are missing and the type of array shouldn't
///     // matter, Bondrewd will use element array logic. also boolean
///     // values are assumed to be 1 bit so this will produce
///     // 5 bits in an output.
///     #[bondrewd(element_bit_length = 1)]
///     two: [bool; 5],
///     // the total amount bits in the array should be 20.
///     // [{4 bits},{8 bits},{8 bits}]
///     #[bondrewd(block_bit_length = 20)]
///     three: [u8; 3],
/// }
/// 
/// fn main() {
///     let test = SimpleWithArray {
///         // the first 4 bits in index 0 and 2 are 1's to show
///         // that they will not be in the final result due to
///         // each element being set to 4 bits, meaning the values
///         // in those indices will become 0 after into_bytes is called.
///         one: [0b11110000, 0b00001111, 0b11110000, 0b00001001],
///         two: [false, true, false, true, false],
///         // its also worth noting that index 0 here will lose the 4
///         // most significant bits.
///         three: [u8::MAX, 0, 0b10101010],
///     };
///     assert_eq!(test.into_bytes(), 
///         [0b0000_1111,  // one[0 and 1]
///          0b0000_1001,  // one[2 and 3]
///          0b01010_111,  // two and three[0]
///          0b1_0000000,  // remaining three[0] and three[1]
///          0b0_1010101,  // remaining three[1] and three[2]
///          0b0_0000000]);// remaining three[2] and 7 unused bits.
/// }
/// ```
/// Structures and Enums can also be used in arrays but there are some extra things to consider.
/// - If bit_length of the structs or enums needs to be smaller than the output of either into_bytes or 
/// into_primitive then it is recommended to use element arrays.
/// - Block Arrays, in my opinion, shouldn't be used for Structs or Enums. because in the below example
/// if the compressed_structures field was to use `block_bit_length = 104` the array would use
/// 48 bits for index 0 and 56 bits for index 1. 
/// ```
/// // this struct uses 52 total bits which means the total
/// // BYTE_SIZE is 7.
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleStruct {
///     #[bondrewd(bit_length = 3)]
///     one: u8,
///     #[bondrewd(bit_length = 27)]
///     two: char,
///     #[bondrewd(bit_length = 14)]
///     three: u16,
///     four: i8,
/// }
/// 
/// // this enum has 4 variants therefore only uses 2 bits
/// // out of 8 in the primitive type.
/// #[derive(BitfieldEnum)]
/// enum SimpleEnum {
///     Zero,
///     One,
///     Two,
///     Three,
/// }
///
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct ArraysWithStructsAndEnums {
///     // if the bit size should be the full size of the primitive, only 
///     // the enum attribute is needed.
///     #[bondrewd(enum_primitive = "u8")]
///     four_byte_four_values: [SimpleEnum; 4],
///     // if we use the element_bit_length we can say to only use 2
///     // bits per SimpleEnum, and due to SimpleEnum only needing 2
///     // bits, this could be desirable. means instead of using 4
///     // bytes to store 4 SimpleEnums, we can use 1 byte.
///     #[bondrewd(enum_primitive = "u8", element_bit_length = 2)]
///     one_byte_four_values: [SimpleEnum; 4],
///     // again if the size doesn't need to change not array attribute
///     // is needed.
///     #[bondrewd(struct_size = 7)]
///     waste_a_byte: [SimpleStruct; 2],
///     // if we want to compress the 2 struct in the array we can
///     // take advantage of the fact our struct is only using 52 out
///     // of 56 bits in the compressed/byte form by adding 
///     // element bit length = 52. this will make the total size of
///     // the 2 structs in compressed/byte form 104 bits instead of
///     // 112.
///     #[bondrewd(struct_size = 7, element_bit_length = 52)]
///     compressed_structures: [SimpleStruct; 2],
/// }
/// ```
/// # Reserve Examples
/// Reserve fields tell Bondrewd to not include logic for reading or writing the field in the from and
/// into bytes functions. Currently only primitive types are supported.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct ReserveExample {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
///     #[bondrewd(bit_length = 10, reserve)]
///     reserve: u16
/// }
/// fn main() {
///     assert_eq!(3, ReserveExample::BYTE_SIZE);
///     assert_eq!(24, ReserveExample::BIT_SIZE);
///     let mut bytes = ReserveExample {
///         one: 127,
///         two: 127,
///         reserve: 1023,
///     }.into_bytes();
///     assert_eq!([0b11111111, 0b11111100, 0b00000000], bytes);
///     assert_eq!(127,ReserveExample::read_one(&bytes));
///     assert_eq!(127,ReserveExample::read_two(&bytes));
///     assert_eq!(0,ReserveExample::read_reserve(&bytes));
///     // quick note write_reserve will actually change the bytes in the byte array.
///     ReserveExample::write_reserve(&mut bytes, 42);
///     assert_eq!(42,ReserveExample::read_reserve(&bytes));
///     // but again from/into bytes doesn't care.
///     let reconstructed = ReserveExample::from_bytes(bytes);
///     assert_eq!(127,reconstructed.one);
///     assert_eq!(127,reconstructed.two);
///     assert_eq!(0,reconstructed.reserve);
/// }
/// ```
/// Reserves do not need to be at the end.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", fill_bytes = 3)]
/// struct ReserveExample {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 10, reserve)]
///     reserve: u16,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
/// }
/// fn main() {
///     assert_eq!(3, ReserveExample::BYTE_SIZE);
///     assert_eq!(24, ReserveExample::BIT_SIZE);
///     let mut bytes = ReserveExample {
///         one: 127,
///         two: 127,
///         reserve: 1023,
///     }.into_bytes();
///     assert_eq!(127, ReserveExample::read_one(&bytes));
///     assert_eq!(127, ReserveExample::read_two(&bytes));
///     assert_eq!(0, ReserveExample::read_reserve(&bytes));
///     ReserveExample::write_reserve(&mut bytes, 42);
///     assert_eq!(42, ReserveExample::read_reserve(&bytes));
///     let reconstructed = ReserveExample::from_bytes(bytes);
///     assert_eq!(127,reconstructed.one);
///     assert_eq!(127,reconstructed.two);
///     assert_eq!(0,reconstructed.reserve);
/// }
/// ```
/// # Fill Bytes Examples
/// Fill bytes is used here to make the total output byte size 3 bytes. If fill bytes attribute was not
/// present the total output byte size would be 2.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", fill_bytes = 3)]
/// struct FilledBytes {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
/// }
/// fn main() {
///     assert_eq!(3, FilledBytes::BYTE_SIZE);
///     assert_eq!(24, FilledBytes::BIT_SIZE);
/// }
/// ```
/// Here im going to compare the example above to the closest alternative using a reserve field:
/// - FilledBytes only has 2 field, so only 2 fields are required for instantiation, where as ReservedBytes
/// still needs a value for the reserve field despite from/into bytes not using the value anyway.
/// - ReservedBytes has 2 extra functions that FilledBytes does not, `write_reserve` and `read_reserve`.
/// - One more thing to consider is reserve fields are currently confined to primitives, if more than 128
/// reserve bits are required at the end, fill_bytes is the only supported way of doing this.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct ReservedBytes {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
///     #[bondrewd(bit_length = 10, reserve)]
///     reserve: u16
/// }
/// fn main() {
///     assert_eq!(3, ReservedBytes::BYTE_SIZE);
///     assert_eq!(24, ReservedBytes::BIT_SIZE);
/// }
/// ```
/// # Enforce Bits Examples
/// Enforce Bits/Bytes Main purpose is to act as a compile time check to ensure how many bit you think
/// are being use is the actual amount of bits being used.  
/// Here i have 2 fields with a total defined bit-length of 6, and then an undecorated boolean field. I
/// also have trust issues so i want to verify that the bool is only using 1 bit making the total bit
/// length of the struct 7 bits. Adding `enforce_bits = 7` will force a compiler error if the calculated
/// total bit length is not 7.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", enforce_bits = 7)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 4)]
///     one: u8,
///     #[bondrewd(bit_length = 2)]
///     two: u8,
///     three: bool
/// }
/// fn main() {
///     assert_eq!(1, FilledBytesEnforced::BYTE_SIZE);
///     assert_eq!(7, FilledBytesEnforced::BIT_SIZE);
/// }
/// ```
/// Here is the same example where but i messed up the bit_length of the first field making the total 8
/// instead of 7. 
/// ```compile_fail
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", enforce_bits = 7)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 5)]
///     one: u8,
///     #[bondrewd(bit_length = 2)]
///     two: u8,
///     three: bool
/// }
/// fn main() {
///     assert_eq!(1, FilledBytesEnforced::BYTE_SIZE);
///     assert_eq!(7, FilledBytesEnforced::BIT_SIZE);
/// }
/// ```
///   
/// These next 3 examples all attempt to have near the same end results. A total output of 3 bytes, but the
/// last 10 of them will be reserved/unused (should be ignored and assumed to be 0).
/// 
/// In this first example i will be showing what a struct might look like without fill bytes, then in the
/// second example i will show the the same end result but without a reserve field. First will be defining
/// all 24 total bits as 3 fields marking the last field of 10 bits with the reserve attribute
/// because we don't want from/into bytes functions to process those bytes.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", enforce_bytes = 3)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
///     #[bondrewd(bit_length = 10, reserve)]
///     reserve: u16
/// }
/// fn main() {
///     assert_eq!(3, FilledBytesEnforced::BYTE_SIZE);
///     assert_eq!(24, FilledBytesEnforced::BIT_SIZE);
/// }
/// ```
/// Also note that [`fill_bytes`](#fill-bytes-examples) does NOT effect how `enforce_bytes` works. 
/// `enforce_bytes` will check the total bit length before the bits are filled.
///   
/// Here i am telling Bondrewd to make the total bit length 3 bytes using `fill_bytes`.
/// This Example fails to build because only 14 bits are being defined by fields and `enforce_bytes` 
/// is telling Bondrewd to expect 24 bits to be used by defined fields.
/// ```compile_fail
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", fill_bytes = 3, enforce_bytes = 3)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
/// }
/// ```
/// To fix this we need to make sure our enforcement value is the amount fo bits defined by the fields NOT
/// the expected FilledBytesEnforced::BYTE_SIZE.
///   
/// Here is the Correct usage of these two attributes working together.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", fill_bytes = 3, enforce_bits = 14)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
/// }
/// fn main() {
///     assert_eq!(3, FilledBytesEnforced::BYTE_SIZE);
///     // we are enforcing 14 bits but fill_bytes is creating
///     // an imaginary reserve field from bit index 14 to
///     // index 23
///     assert_eq!(24, FilledBytesEnforced::BIT_SIZE);
/// }
/// ```
/// # Enforce Full Bytes Example
/// `enforce_full_bytes` adds a check during parsing phase of Bondrewd which will throw an error if the
/// total bits determined from the defined fields is not a multiple of 8. This was included for those
/// like me that get paranoid they entered something in wrong.
/// ```compile_fail
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", enforce_full_bytes)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
/// }
/// ```
/// In this case if we still wanted fields one and two to remain 7 bits we need to add another field
/// to use the remaining 2 bits.
/// ```
/// use bondrewd::*;
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be", enforce_full_bytes)]
/// struct FilledBytesEnforced {
///     #[bondrewd(bit_length = 7)]
///     one: u8,
///     #[bondrewd(bit_length = 7)]
///     two: u8,
///     #[bondrewd(bit_length = 2, reserve)]
///     reserve: u16
/// }
/// fn main() {
///     assert_eq!(2, FilledBytesEnforced::BYTE_SIZE);
///     assert_eq!(16, FilledBytesEnforced::BIT_SIZE);
/// }
/// ```
/// # Enum Examples
/// For enum derive examples goto [BitfieldEnum Derive](BitfieldEnum).
/// ```
/// use bondrewd::*;
/// #[derive(BitfieldEnum)]
/// enum SimpleEnum {
///     Zero,
///     One,
///     Two,
///     Three,
/// }
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "le")]
/// struct StructWithEnumExample {
///     #[bondrewd(bit_length = 3)]
///     one: u8,
///     #[bondrewd(enum_primitive = "u8", bit_length = 2)]
///     two: SimpleEnum,
///     #[bondrewd(bit_length = 3)]
///     three: u8,
/// }
/// ```
/// Enums can also be used in [arrays](#bitfield-array-examples)
/// ```
/// use bondrewd::*;
/// #[derive(BitfieldEnum)]
/// enum Simple {
///     One,
///     Two,
///     Three,
///     Four,
/// }
///
/// #[derive(Bitfields)]
/// #[bondrewd(default_endianness = "be")]
/// struct SimpleWithStruct {
///     // bit length is not required for enums but in this case where only 4 possible variants are in
///     // our enums 2 bits is all that is needed. also note using more bits than possible variants is
///     // not a problem because the catch all system will protect you from bad inputs.
///     #[bondrewd(bit_length = 2, enum_primitive = "u8")]
///     one: Simple,
///     #[bondrewd(element_bit_length = 2, enum_primitive = "u8")]
///     two: [Simple; 3],
/// }
/// ```
#[proc_macro_derive(Bitfields, attributes(bondrewd,))]
pub fn derive_bitfields(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    // parse the input into a StructInfo which contains all the information we
    // along with some helpful structures to generate our Bitfield code.
    let struct_info = match StructInfo::parse(&input) {
        Ok(parsed_struct) => parsed_struct,
        Err(err) => {
            return TokenStream::from(err.to_compile_error());
        }
    };
    // println!("{:?}", struct_info);
    // get the struct size and name so we can use them in a quote.
    let struct_size = struct_info.total_bytes();
    let struct_name = format_ident!("{}", struct_info.name);

    // get a list of all fields from_bytes logic which gets there bytes from an array called
    // input_byte_buffer.
    let slice_fns: bool;
    #[cfg(not(feature = "slice_fns"))]
    {
        slice_fns = false;
    }
    #[cfg(feature = "slice_fns")]
    {
        slice_fns = true;
    }
    // get a list of all fields into_bytes logic which puts there bytes into an array called
    // output_byte_buffer.
    let fields_into_bytes = match create_into_bytes_field_quotes(&struct_info, slice_fns) {
        Ok(ftb) => ftb,
        Err(err) => return TokenStream::from(err.to_compile_error()),
    };
    let fields_from_bytes = match create_from_bytes_field_quotes(&struct_info, slice_fns) {
        Ok(ffb) => ffb,
        Err(err) => return TokenStream::from(err.to_compile_error()),
    };
    // combine all of the into_bytes quotes separated by newlines
    let into_bytes_quote = fields_into_bytes.into_bytes_fn;
    let mut set_quotes = fields_into_bytes.set_field_fns;

    if let Some(set_slice_quote) = fields_into_bytes.set_slice_field_fns {
        set_quotes = quote! {
            #set_quotes
            #set_slice_quote
        }
    }

    let from_bytes_quote = fields_from_bytes.from_bytes_fn;
    let mut peek_quotes = fields_from_bytes.peek_field_fns;

    if let Some(peek_slice_quote) = fields_from_bytes.peek_slice_field_fns {
        peek_quotes = quote! {
            #peek_quotes
            #peek_slice_quote
        }
    }

    let setters: bool;
    #[cfg(not(feature = "setters"))]
    {
        setters = false;
    }
    #[cfg(feature = "setters")]
    {
        setters = true;
    }
    let setters_quote = if setters {
        match structs::struct_fns::create_into_bytes_field_quotes(&struct_info) {
            Ok(parsed_struct) => parsed_struct,
            Err(err) => {
                return TokenStream::from(err.to_compile_error());
            }
        }
    } else {
        quote! {}
    };

    let getter_setters_quotes = quote! {
        impl #struct_name {
            #peek_quotes
            #set_quotes
            #setters_quote
        }
    };
    let hex;
    #[cfg(feature = "hex_fns")]
    {
        hex = true;
    }
    #[cfg(not(feature = "hex_fns"))]
    {
        hex = false;
    }
    let hex_size = struct_size * 2;
    let hex_fns_quote = if hex {
        quote! {
            impl BitfieldHex<#hex_size> for #struct_name {
                fn from_hex(hex: [u8;#hex_size]) -> Result<Self, BitfieldHexError> {
                    let bytes: [u8; #struct_size] = [0;#struct_size];
                    let mut bytes: [u8; Self::BYTE_SIZE] = [0;Self::BYTE_SIZE];
                    for i in 0usize..#struct_size {
                        let index = i * 2;
                        let index2 = index + 1;
                        let decode_nibble = |c, c_i| match c {
                            b'A'..=b'F' => Ok(c - b'A' + 10u8),
                            b'a'..=b'f' => Ok(c - b'a' + 10u8),
                            b'0'..=b'9' => Ok(c - b'0'),
                            _ => return Err(BitfieldHexError(
                                c as char,
                                c_i,
                            )),
                        };
                        bytes[i] = ((decode_nibble(hex[index], index)? & 0b00001111) << 4) | decode_nibble(hex[index2], index2)?;
                    }
                    Ok(Self::from_bytes(bytes))

                }

                fn into_hex_upper(self) -> [u8;#hex_size] {
                    let bytes = self.into_bytes();
                    let mut output: [u8;#hex_size] = [0; #hex_size];
                    for (i, byte) in (0..#hex_size).step_by(2).zip(bytes) {
                        output[i] = (Self::UPPERS[((byte & 0b11110000) >> 4) as usize]);
                        output[i + 1] = (Self::UPPERS[(byte & 0b00001111) as usize]);
                    }
                    output
                }

                fn into_hex_lower(self) -> [u8;#hex_size] {
                    let bytes = self.into_bytes();
                    let mut output: [u8;#hex_size] = [0; #hex_size];
                    for (i, byte) in (0..#hex_size).step_by(2).zip(bytes) {
                        output[i] = (Self::LOWERS[((byte & 0b11110000) >> 4) as usize]);
                        output[i + 1] = (Self::LOWERS[(byte & 0b00001111) as usize]);
                    }
                    output
                }
            }
        }
    } else {
        quote! {}
    };

    // get the bit size of the entire set of fields to fill in trait requirement.
    let bit_size = struct_info.total_bits();

    // put it all together.
    // to_bytes_quote will put all of the fields in self into a array called output_byte_buffer.
    // so for into_bytes all we need is the fn declaration, the output_byte_buffer, and to return
    // that buffer.
    // from_bytes is essentially the same minus a variable because input_byte_buffer is the input.
    // slap peek quotes inside a impl block at the end and we good to go
    let to_bytes_quote = quote! {
        impl Bitfields<#struct_size> for #struct_name {
            const BIT_SIZE: usize = #bit_size;
            #into_bytes_quote
            #from_bytes_quote
        }
        #getter_setters_quotes
        #hex_fns_quote
    };

    if slice_fns {
        let vis = struct_info.vis;
        let checked_ident = format_ident!("{}Checked", &struct_name);
        let checked_mut_ident = format_ident!("{}CheckedMut", &struct_name);
        let unchecked_functions = fields_from_bytes.peek_slice_field_unchecked_fns;
        let unchecked_mut_functions = fields_into_bytes.set_slice_field_unchecked_fns;
        let to_bytes_quote = quote!{
            #to_bytes_quote
            #vis struct #checked_ident<'a> {
                buffer: &'a [u8],
            }
            impl<'a> #checked_ident<'a> {
                #unchecked_functions
            }
            #vis struct #checked_mut_ident<'a> {
                buffer: &'a mut [u8],
            }
            impl<'a> #checked_mut_ident<'a> {
                #unchecked_functions
                #unchecked_mut_functions
            }
        };
        TokenStream::from(to_bytes_quote)
    }else{
        TokenStream::from(to_bytes_quote)
    }

    
}

/// Generates an implementation of bondrewd::BitfieldEnum trait.
///   
/// Important Note: u8 is the only primitive type i have tested. My newest code should be able to handle
/// all primitive types but, to reiterate, i have NOT tested any primitive type other than u8.
///
/// # Features
/// - Generates code for the BitfieldEnum trait which allows an enum to be used by Bitfield structs.
/// - Literal values. [example](#literal-example)
/// - Automatic Value Assignment for non-literal variants. Variants are assigned values starting from 0
/// incrementing by 1 skipping values taken by literal definitions (That means you can mix and match
/// inferred values a code defined literal values). [example](#typical-example)
/// - Catch Variants
///     - Catch All variant is used to insure that Results are not needed. Catch all will generate a
///     `_ => {..}` match arm so that enums don't need to have as many variants as there are values in
///     the defined primitive. Catch all can be defined with a `#[bondrewd_enum(invalid)]` attribute or last variant will
///     Automatically become a catch all if no Catch is defined. [example](#custom-catch-all-example)
///     - Catch Value is a variant that will store values that don't match the reset of the variants.
///     using a Catch Value is as simple as making a variant with a primitive value (if the bondrewd_enum
///     attribute is present the primitive types must match). [example](#catch-value-example)
///
/// # Other Features
/// - Support for implementation of [`std::cmp::PartialEq`] for the given primitive (currently only u8)
///
/// # Typical Example
/// Here i am letting the Derive do all of the work. The primitive type will be assumed to be u8 because
/// there are less than 256 variants. Variants that do not define a value will be assigned a value
/// starting with the lowest available value. Also due to the catch all system we can ignore the fact
/// i have not covered all 255 values of a u8 because the last Variant, SimpleEnum::Three is this example,
/// will be used a a default to insure not errors can occur.
/// ```
/// use bondrewd::BitfieldEnum;
/// #[derive(BitfieldEnum, PartialEq, Debug)]
/// enum SimpleEnum {
///     Zero, // assigned value 0
///     One,  // assigned value 1
///     Two,  // assigned value 2
///     Three,// assigned value 3
/// }
/// 
/// fn main(){
///     assert_eq!(SimpleEnum::Zero.into_primitive(), 0);
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(0));
///     assert_eq!(SimpleEnum::One.into_primitive(), 1);
///     assert_eq!(SimpleEnum::One, SimpleEnum::from_primitive(1));
///     assert_eq!(SimpleEnum::Two.into_primitive(), 2);
///     assert_eq!(SimpleEnum::Two, SimpleEnum::from_primitive(2));
///     assert_eq!(SimpleEnum::Three.into_primitive(), 3);
///     for i in 3..=u8::MAX {
///         assert_eq!(SimpleEnum::Three, SimpleEnum::from_primitive(i));
///     }
/// }
/// 
/// ```
/// If you do not want the last variant to be a
/// catch all you must either:
/// - Cover all possible values in the primitive type with a variant each.
/// - Mark the variant you would like to be the catch all [example](#custom-catch-all-example).
/// - Add a catch primitive variant [example](#catch-value-example)
/// # Literal Example
/// ```
/// use bondrewd::BitfieldEnum;
/// #[derive(BitfieldEnum, PartialEq, Debug)]
/// enum SimpleEnum {
///     Life = 42,
///     Min = 0,
///     U8Max = 255,
///     Unlucky = 13,
/// }
/// 
/// fn main(){
///     assert_eq!(SimpleEnum::Life.into_primitive(), 42);
///     assert_eq!(SimpleEnum::Life, SimpleEnum::from_primitive(42));
///     assert_eq!(SimpleEnum::Min.into_primitive(), 0);
///     assert_eq!(SimpleEnum::Min, SimpleEnum::from_primitive(0));
///     assert_eq!(SimpleEnum::U8Max.into_primitive(), 255);
///     assert_eq!(SimpleEnum::U8Max, SimpleEnum::from_primitive(255));
///     assert_eq!(SimpleEnum::Unlucky.into_primitive(), 13);
///     // check all values not defined and 13 get detected as Unlucky
///     for i in 1..42 {
///         assert_eq!(SimpleEnum::Unlucky, SimpleEnum::from_primitive(i));
///     }
///     for i in 43..u8::MAX {
///         assert_eq!(SimpleEnum::Unlucky, SimpleEnum::from_primitive(i));
///     }
/// }
/// ```
/// # Custom Catch All Example
/// If you don't decorate the Enum at all the last variant will be assumed to be an Invalid variant. This
/// means if the input value doesn't match any defined value we can use the Invalid variant as a default.
/// ```
/// use bondrewd::BitfieldEnum;
/// #[derive(BitfieldEnum, PartialEq, Debug)]
/// enum SimpleEnum {
///     Zero, // assigned 0
///     One, // assigned 1
///     Two, // assigned 2
///     Three, // assigned 3 and catches invalid values
/// }
/// 
/// fn main(){
///     assert_eq!(SimpleEnum::Zero.into_primitive(), 0);
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(0));
///     assert_eq!(SimpleEnum::One.into_primitive(), 1);
///     assert_eq!(SimpleEnum::One, SimpleEnum::from_primitive(1));
///     assert_eq!(SimpleEnum::Two.into_primitive(), 2);
///     assert_eq!(SimpleEnum::Two, SimpleEnum::from_primitive(2));
///     assert_eq!(SimpleEnum::Three.into_primitive(), 3);
///     assert_eq!(SimpleEnum::Three, SimpleEnum::from_primitive(3));
///     // remaining possible values are caught as One.
///     for i in 4..=u8::MAX {
///         assert_eq!(SimpleEnum::Three, SimpleEnum::from_primitive(i));
///     }
/// }
/// ```
/// This example shows that we can mark any variant as the catch all variant. In this case Bondrewd will
/// give SimpleEnum::One the value of 1 and make One catch all values not defined because
/// of the invalid attribute.
/// ```
/// use bondrewd::BitfieldEnum;
/// #[derive(BitfieldEnum, PartialEq, Debug)]
/// enum SimpleEnum {
///     Zero, // assigned 0
///     #[bondrewd_enum(invalid)]
///     One, // assigned 1 and catches invalid values
///     Two, // assigned 2
///     Three, // assigned 3
/// }
/// 
/// fn main(){
///     assert_eq!(SimpleEnum::Zero.into_primitive(), 0);
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(0));
///     assert_eq!(SimpleEnum::One.into_primitive(), 1);
///     assert_eq!(SimpleEnum::One, SimpleEnum::from_primitive(1));
///     assert_eq!(SimpleEnum::Two.into_primitive(), 2);
///     assert_eq!(SimpleEnum::Two, SimpleEnum::from_primitive(2));
///     assert_eq!(SimpleEnum::Three.into_primitive(), 3);
///     assert_eq!(SimpleEnum::Three, SimpleEnum::from_primitive(3));
///     // remaining possible values are caught as One.
///     for i in 4..=u8::MAX {
///         assert_eq!(SimpleEnum::One, SimpleEnum::from_primitive(i));
///     }
/// }
/// ```
/// # Catch Value Example
/// In some cases we might need to know what the invalid value passed into from_primitive actually was. In
/// my own code there is an enum field that gets encrypted and can become pretty much any value and cause
/// panics in the library i used before writing Bondrewd. To fix this Bondrewd offers the ability to make 1
/// variant a tuple or struct variant with exactly one field which must be the primitive type the enum
/// gets converted into/from, than the variant values not covered will be stored in the variants field.
/// ```
/// use bondrewd::BitfieldEnum;
/// #[derive(BitfieldEnum, PartialEq, Debug)]
/// enum SimpleEnum {
///     Zero,
///     One,
///     Two,
///     Three(u8),
/// }
/// 
/// fn main(){
///     assert_eq!(SimpleEnum::Zero.into_primitive(), 0);
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(0));
///     assert_eq!(SimpleEnum::One.into_primitive(), 1);
///     assert_eq!(SimpleEnum::One, SimpleEnum::from_primitive(1));
///     assert_eq!(SimpleEnum::Two.into_primitive(), 2);
///     assert_eq!(SimpleEnum::Two, SimpleEnum::from_primitive(2));
///     for i in 3..=u8::MAX {
///         assert_eq!(SimpleEnum::Three(i), SimpleEnum::from_primitive(i));
///     }
/// }
/// ```
/// # Complex Example
/// Here i just want to show that Literals, Auto Value Assignment, and Invalid catch all can all be used
/// together. As you might expect Catch Primitive can not have a Literal value because it stores a value.
/// Here we expect:
/// - SimpleEnum::Nine = 9,
/// - SimpleEnum::One  = 1,
/// - SimpleEnum::Zero = 0 and accept 3, 4, 6, 7, 8, and 10..u8::MAX in from_primitive(),
/// - SimpleEnum::Five = 5,
/// - SimpleEnum::Two  = 2,
/// ```
/// use bondrewd::BitfieldEnum;
/// #[derive(BitfieldEnum, PartialEq, Debug)]
/// enum SimpleEnum {
///     Nine = 9,
///     // because variant `One` is the first non-literal variant it will be
///     // given the first available value
///     One,
///     // Literals can still be a catch all.
///     #[bondrewd_enum(invalid)]
///     Zero = 0,
///     Five = 5,
///     // because variant `One` is the second non-literal variant it will be
///     // given the second available value
///     Two,
/// }
///
/// fn main(){
///     assert_eq!(SimpleEnum::Nine.into_primitive(), 9);
///     assert_eq!(SimpleEnum::Nine, SimpleEnum::from_primitive(9));
///     assert_eq!(SimpleEnum::One.into_primitive(), 1);
///     assert_eq!(SimpleEnum::One, SimpleEnum::from_primitive(1));
///     assert_eq!(SimpleEnum::Zero.into_primitive(), 0);
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(0));
///     assert_eq!(SimpleEnum::Five.into_primitive(), 5);
///     assert_eq!(SimpleEnum::Five, SimpleEnum::from_primitive(5));
///     assert_eq!(SimpleEnum::Two.into_primitive(), 2);
///     assert_eq!(SimpleEnum::Two, SimpleEnum::from_primitive(2));
///     // Invalid tests
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(3));
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(4));
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(6));
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(7));
///     assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(8));
///     for i in 10..=u8::MAX {
///         assert_eq!(SimpleEnum::Zero, SimpleEnum::from_primitive(i));
///     }
/// }
/// ```
#[proc_macro_derive(BitfieldEnum, attributes(bondrewd_enum))]
pub fn derive_bondrewd_enum(input: TokenStream) -> TokenStream {
    // TODO added the ability to give a Catch Value Variant a Literal value.
    let input = parse_macro_input!(input as DeriveInput);
    let enum_info = match EnumInfo::parse(&input) {
        Ok(parsed_enum) => parsed_enum,
        Err(err) => {
            return TokenStream::from(err.to_compile_error());
        }
    };
    let into = match enums::into_bytes::generate_into_bytes(&enum_info) {
        Ok(i) => i,
        Err(err) => return TokenStream::from(err.to_compile_error()),
    };
    let from = match enums::from_bytes::generate_from_bytes(&enum_info) {
        Ok(f) => f,
        Err(err) => return TokenStream::from(err.to_compile_error()),
    };
    let partial_eq = enums::partial_eq::generate_partial_eq(&enum_info);
    let enum_name = enum_info.name;
    let primitive = enum_info.primitive;
    TokenStream::from(quote! {
        impl bondrewd::BitfieldEnum for #enum_name {
            type Primitive = #primitive;
            #into
            #from
        }

        #partial_eq
    })
}