use ::CumulativeDistributionFrequency;

use opus::imported_decode;

use std;

pub struct Reader<R> where R: std::io::Read {
    state: imported_decode::ec_dec<R>,
}

impl<R> Reader<R> where R: std::io::Read {
/*
    pub fn from_boxed_slice(mut source: Box<[u8]>) -> Self {
        let state = unsafe {
            let mut state : imported_decode::ec_dec = std::mem::uninitialized();
            imported_decode::ec_dec_init(&mut state, source.as_mut_ptr(), source.len() as u32);
            state
        };
        Reader {
            source,
            state
        }
    }
*/
    pub fn new(input: R) -> Result<Self, std::io::Error> {
        let mut state = imported_decode::ec_dec {
            inp: input,
            // The rest will be initialized by `ec_dec_init`.
            end_window: 0,
            nend_bits: 0,
            nbits_total: 0,
            rng: 0,
            rem: 0,
            val: 0,
            ext: 0,
        };
        unsafe { imported_decode::ec_dec_init(&mut state)?; }
        Ok(Reader {
            state
        })
    }

    /// Decode the next symbol in line.
    pub fn symbol(&mut self, icdf: &CumulativeDistributionFrequency) -> Result<u32, std::io::Error> {
        let index = unsafe {
            let frequency = imported_decode::ec_decode(&mut self.state, icdf.width());
            let indexed= icdf.find(frequency)
                .ok_or_else(|| std::io::Error::new(std::io::ErrorKind::InvalidInput, "Invalid probability"))?;
            imported_decode::ec_dec_update(&mut self.state, indexed.segment.low, indexed.segment.next, icdf.width())?;
            indexed.index
        };
        Ok(index as u32)
    }

/*
// FIXME: I actually don't understand `bits()` well enough
// to publish it.    /// Encode a sequence of raw bits, without any frequency information.
    pub fn bits(&mut self, size: usize) -> Result<u16, std::io::Error> {
        let result = unsafe {
            let result = imported_decode::ec_dec_bits(&mut self.state,
                size as u32);
            self.check_status()?;
            result as u16
        };
        Ok(result)
    }
*/

    pub fn done(self) {
        // FIXME: Nothing to do?
    }
}