//! Sound representation.

use crate::durandal::err::*;
use std::io;

/// Writes a WAVE file from a sound.
///
/// # Errors
///
/// Errors if `out` cannot be written to.
pub fn write_wav(out: &mut impl io::Write, snd: &impl Sound) -> ResultS<()>
{
   let smp_rate = u32::from(snd.rate());
   let smp_size = smp_rate * 2;
   let dat_size = snd.len() as u32 * 2;

   out.write_all(b"RIFF")?;
   out.write_all(&u32::to_le_bytes(36 + dat_size))?;
   out.write_all(b"WAVE")?;

   out.write_all(b"fmt ")?;
   out.write_all(&u32::to_le_bytes(16))?;
   // PCM
   out.write_all(&u16::to_le_bytes(1))?;
   // mono
   out.write_all(&u16::to_le_bytes(1))?;
   out.write_all(&u32::to_le_bytes(smp_rate))?;
   out.write_all(&u32::to_le_bytes(smp_size))?;
   // block alignment
   out.write_all(&u16::to_le_bytes(2))?;
   // bits per sample
   out.write_all(&u16::to_le_bytes(16))?;

   out.write_all(b"data")?;
   out.write_all(&u32::to_le_bytes(dat_size))?;

   for p in 0..snd.len() {
      let sample = snd.index(p);
      out.write_all(&sample.to_le_bytes())?;
   }

   Ok(())
}

/// Any PCM stream which may be represented as a 16-bit PCM stream.
pub trait Sound
{
   /// Returns the sample rate.
   fn rate(&self) -> u16;

   /// Returns the number of samples.
   fn len(&self) -> usize;

   /// Returns the `n`th sample.
   ///
   /// May panic if `n` exceeds the length of this sound.
   fn index(&self, n: usize) -> i16;

   /// Returns the number of the first sample of the loop, or `0`.
   fn lp_beg(&self) -> usize;

   /// Returns the number of the last sample of the loop, or `0`.
   fn lp_end(&self) -> usize;

   /// Returns `true` if there are no samples in this sound.
   fn is_empty(&self) -> bool {self.len() == 0}

   /// The same as `index`, but will not panic if out of bounds.
   fn get(&self, n: usize) -> Option<i16>
   {
      if n < self.len() {
         Some(self.index(n))
      } else {
         None
      }
   }
}

impl Sound16
{
   /// Creates a new `Sound16`.
   pub fn new(rate: u16, lp_beg: usize, lp_end: usize, len: usize) -> Self
   {
      Self{rate, lp_beg, lp_end, data: Vec::with_capacity(len)}
   }

   /// Creates a new `Sound16` from an unsigned 8-bit stream.
   pub fn new_from_8(rate: u16, lp_beg: usize, lp_end: usize, b: &[u8])
      -> Self
   {
      let mut snd = Self::new(rate, lp_beg, lp_end, b.len());

      for &sample in b {
         snd.data.push(Self::sample_from_8(sample));
      }

      snd
   }

   /// Creates a new `Sound16` from a signed 16-bit stream.
   pub fn new_from_16(rate: u16, lp_beg: usize, lp_end: usize, b: &[u8])
      -> Self
   {
      let mut snd = Self::new(rate, lp_beg, lp_end, b.len() / 2);

      for i in (0..b.len()).step_by(2) {
         snd.data.push(i16::from_le_bytes([b[i], b[i + 1]]));
      }

      snd
   }

   /// Creates a signed 16-bit sample from an unsigned 8-bit sample.
   pub fn sample_from_8(sample: u8) -> i16 {(i16::from(sample) - 0x80) << 8}
}

impl Sound for Sound16
{
   fn rate(&self) -> u16 {self.rate}
   fn len(&self) -> usize {self.data.len()}
   fn index(&self, p: usize) -> i16 {self.data[p]}
   fn lp_beg(&self) -> usize {self.lp_beg}
   fn lp_end(&self) -> usize {self.lp_end}
}

/// A 16-bit PCM stream.
pub struct Sound16
{
   rate:   u16,
   lp_beg: usize,
   lp_end: usize,

   /// The raw signed PCM data of this sound.
   pub data: Vec<i16>,
}

// EOF