//! Binary data conversion utilities.

use crate::durandal::err::*;
use serde::Serialize;
use std::{fmt, num::NonZeroU16};

#[doc(hidden)]
macro_rules! rd_1 {
   // big endian
   (BE $b:ident $nam:ident u16 $n:expr) => {
      rd_1!($b u16::from_be_bytes, $nam 2 $n);
   };
   (BE $b:ident $nam:ident i16 $n:expr) => {
      rd_1!($b i16::from_be_bytes, $nam 2 $n);
   };
   (BE $b:ident $nam:ident u32 $n:expr) => {
      rd_1!($b u32::from_be_bytes, $nam 4 $n);
   };
   (BE $b:ident $nam:ident i32 $n:expr) => {
      rd_1!($b i32::from_be_bytes, $nam 4 $n);
   };
   (BE $b:ident $nam:ident as usize u16 $n:expr) => {
      rd_1!($b u16::from_be_bytes, $nam 2 $n);
      let $nam = $nam as usize;
   };
   (BE $b:ident $nam:ident as usize u32 $n:expr) => {
      rd_1!($b u32::from_be_bytes, $nam 4 $n);
      let $nam = $nam as usize;
   };
   (BE $b:ident $nam:ident Angle $n:expr) => {
      rd_1!($b u16::from_be_bytes, $nam 2 $n);
      let $nam = Angle::from_bits($nam);
   };
   (BE $b:ident $nam:ident Fixed $n:expr) => {
      rd_1!($b u32::from_be_bytes, $nam 4 $n);
      let $nam = Fixed::from_bits($nam);
   };
   (BE $b:ident $nam:ident Unit $n:expr) => {
      rd_1!($b u16::from_be_bytes, $nam 2 $n);
      let $nam = Unit::from_bits($nam);
   };
   (BE $b:ident $nam:ident OptU16 $n:expr) => {
      rd_1!($b u16::from_be_bytes, $nam 2 $n);
      let $nam = OptU16::from_repr($nam);
   };

   // little endian
   (LE $b:ident $nam:ident u16 $n:expr) => {
      rd_1!($b u16::from_le_bytes $nam 2 $n);
   };
   (LE $b:ident $nam:ident i16 $n:expr) => {
      rd_1!($b i16::from_le_bytes $nam 2 $n);
   };
   (LE $b:ident $nam:ident u32 $n:expr) => {
      rd_1!($b u32::from_le_bytes $nam 4 $n);
   };
   (LE $b:ident $nam:ident i32 $n:expr) => {
      rd_1!($b i32::from_le_bytes $nam 4 $n);
   };
   (LE $b:ident $nam:ident as usize u16 $n:expr) => {
      rd_1!($b u16::from_le_bytes $nam 2 $n);
      let $nam = $nam as usize;
   };
   (LE $b:ident $nam:ident as usize u32 $n:expr) => {
      rd_1!($b u32::from_le_bytes $nam 4 $n);
      let $nam = $nam as usize;
   };

   // generic endianness
   ($_:ident $b:ident $nam:ident u8 $n:expr) => {
      let $nam = $b[$n];
   };
   ($_:ident $b:ident $nam:ident array u8 $n:expr) => {
      let $nam = &$b[$n];
   };
   ($_:ident $b:ident $nam:ident i8 $n:expr) => {
      let $nam = $b[$n] as i8;
   };
   ($_:ident $b:ident $nam:ident iden $n:expr) => {
      let $nam = [$b[$n], $b[$n + 1], $b[$n + 2], $b[$n + 3]];
   };
   ($_:ident $b:ident $nam:ident $f:ident $n:expr) => {
      let $nam = $f(&$b[$n])?;
   };
   ($_:ident $b:ident $nam:ident nt $f:ident $n:expr) => {
      let $nam = $f(&$b[$n]);
   };

   // worker - creates let statement
   ($b:ident $pth:path , $nam:ident 2 $n:expr) => {
      let $nam = $pth([$b[$n], $b[$n + 1]]);
   };
   ($b:ident $pth:path , $nam:ident 4 $n:expr) => {
      let $nam = $pth([$b[$n], $b[$n + 1], $b[$n + 2], $b[$n + 3]]);
   };
}

macro_rules! read_data {
   (
      $sz:expr , $ty:ident in $b:ident =>
      $( $nam:ident = $t:ident [ $n:expr ] $( $ex:ident )* ; )*
   ) => {
      if $b.len() < $sz {
         bail!("not enough data");
      }

      $(rd_1!($ty $b $nam $($ex)* $t $n);)*
   };
}

pub fn ident(b: &[u8]) -> Ident {[b[0], b[1], b[2], b[3]]}
pub fn u32b(b: &[u8]) -> u32 {u32::from_be_bytes([b[0], b[1], b[2], b[3]])}
pub fn u16b(b: &[u8]) -> u16 {u16::from_be_bytes([b[0], b[1]])}
pub fn i32b(b: &[u8]) -> i32 {i32::from_be_bytes([b[0], b[1], b[2], b[3]])}
pub fn i16b(b: &[u8]) -> i16 {i16::from_be_bytes([b[0], b[1]])}

pub fn rd_array<T, F>(b: &[u8], read: F) -> ResultS<Vec<T>>
   where T: Sized,
         F: Fn(&[u8]) -> ResultS<(T, usize)>
{
   let mut v = Vec::new();
   let mut p = 0;

   while p < b.len() {
      let (r, s) = read(&b[p..])?;
      v.push(r);
      p += s;
   }

   Ok(v)
}

pub fn rd_ofstable<T, F>(b: &[u8],
                         mut p: usize,
                         num: usize,
                         read: F)
                         -> ResultS<Vec<T>>
   where T: Sized,
         F: Fn(&[u8]) -> ResultS<T>
{
   let mut v = Vec::with_capacity(num);

   for _ in 0..num {
      let ofs = u32b(&b[p..]) as usize;

      if ofs >= b.len() {
         bail!("not enough data");
      }

      v.push(read(&b[ofs..])?);
      p += 4;
   }

   Ok(v)
}

impl OptU16
{
   /// Creates an `OptU16` from a `u16`.
   pub fn from_repr(n: u16) -> Self
   {
      if n == u16::max_value() {
         Self(None)
      } else {
         Self(NonZeroU16::new(n + 1))
      }
   }

   /// Returns the `u16` representation of an `OptU16`.
   pub fn get_repr(&self) -> u16
   {
      match self.0 {
         None => u16::max_value(),
         Some(n) => n.get() - 1,
      }
   }

   /// Returns the `Option` representation of an `OptU16`.
   pub fn get(&self) -> Option<u16>
   {
      match self.0 {
         None => None,
         Some(n) => Some(n.get() - 1),
      }
   }
}

impl fmt::Debug for OptU16
{
   fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
   {
      match self.get() {
         None => write!(f, "None"),
         Some(n) => write!(f, "Some({})", n),
      }
   }
}

/// A four-character-code identifier.
pub type Ident = [u8; 4];

/// An object identified by a `u16` which may be `u16::max_value()` to
/// represent None.
#[derive(Serialize)]
pub struct OptU16(Option<NonZeroU16>);

// EOF