// Package provides a shifted fibonacci encoding of unsigned integers.
//
// http://en.wikipedia.org/wiki/Fibonacci_coding maps positive integers as
// 1 - 11, 2 - 011, 3 - 0011, 4 - 1011, 5 - 00011
//
// Incrementing input by one to allow for zero gives
// 0 - 11, 1 - 011, 2 - 0011, 3 - 1011, 4 - 00011
//
// The codes are then reversed so that they are easily stored in uints
// The codes are reversed so that they are easily stored in uints,
// effectively avoiding the need to store the number of leading zeroes
// 0 - 11, 1 - 110, 2 - 1100, 3 - 1101, 4 - 11000
// (so that they are always comparable with each other as there is no need to
//  store the leading number of zeroes which are otherwise required)
package fibonacci

import (
	_ "fmt"
	"io"
)

type Numbers []uint64

// Returns a slice with fibonacci numbers up to the given length
func New(size int) Numbers {

		// Clear the buffer
		e.buffer = e.buffer[:0]
	}
	return total, err
}

// func Reader(source io.Reader) io.Reader {
// 	var dec decoder
// 	dec.Numbers = New(16)
// 	dec.source = source
// 	return &dec
func Reader(source io.Reader) io.Reader {
	var dec decoder
	dec.Numbers = New(16)
	dec.source = source
	return &dec
// }

// type decoder struct {
// 	Numbers
// 	source io.Reader
// 	buffer uint64
// 	at     byte
}

type decoder struct {
	Numbers
	source io.Reader
	buffer uint64
	at     byte
// }

// func (d *decoder) Read(output []byte) (int, error) {
// 	var (
// 		total int
// 		err   error
}

func (d *decoder) Read(output []byte) (int, error) {
	var (
		total int
		err   error
// 	)

// 	// While we have suitable buffered data and enough output space
// 	for (len(output) > 0) && ((d.buffer & (d.buffer >> 1)) > 0) {
// 		val, len := d.Decode(d.buffer)
	)

start:
	// While we have suitable buffered data and enough output space
	for (len(output) > 0) && ((d.buffer & (d.buffer >> 1)) > 0) {
		val, len := d.Decode(d.buffer)

// 		// Store the decoded byte
// 		output[0] = byte(val)
		// Store the decoded byte
		output[0] = byte(val)

// 		// Advance the internal and output buffers
// 		output = output[1:]
// 		d.buffer >>= len

		// Advance the internal and output buffers
		output = output[1:]
		d.buffer >>= len
		d.at -= len
// 		// TODO - decrease d.at as well ?

// 		total++
		total++
// 	}

// 	// Termination condition
// 	if len(output) == 0 {
// 		return total, nil
// 	}

// 	// count, err := d.source.Read(output)

// 	return total, err
// }
	}

	// Termination condition
	if len(output) == 0 || err != nil {
		return total, err
	}

	// We need to limit the output's size else we could end up with a lot of small values
	// that fit neither in the output slice nor in the internal buffer
	free := int((63 ^ d.at) >> 3)
	if free > len(output) {
		free = len(output)
	}

	// Read data and transfer to the internal buffer
	count, err := d.source.Read(output[:free])
	for _, v := range output[:count] {
		d.buffer |= uint64(v) << d.at
		d.at += 8
	}

	goto start
}