// 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 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


package fibonacci

import (

	"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

}

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

}

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

	)

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)

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


		total++

	}

	// 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
}

package fibonacci

import (
	diff "0dev.org/diff"
	"bytes"
	"io"
	"strings"
	"testing"
)

func TestNumbers(t *testing.T) {

		}
		if encLen != decLen {
			t.Errorf("Unexpected difference between encoded and decoded lengths.", encLen, decLen)
		}
	}
}

func TestWriterReader(t *testing.T) {
	var (
		buf   bytes.Buffer
		w     io.Writer = Writer(&buf)
		input []byte    = make([]byte, 256)
		fib   Numbers   = New(16)
	)

	for i := uint64(0); i < 256; i++ {
		input[i] = byte(i)
	}

	// Write the input
	count, err := w.Write(input)

		c, l := fib.Code(uint64(v))
		vs := u2s(c, l)
		if loc := strings.Index(output, vs); loc != 0 {
			t.Fatal("Unexpected location for", i, "value", vs)
		}
		output = output[len(vs):]
	}

	var (
		in  *bytes.Reader = bytes.NewReader(buf.Bytes())
		r   io.Reader     = Reader(in)
		out bytes.Buffer
	)
	io.Copy(&out, r)
	decoded := out.Bytes()

	delta := diff.Diff(diff.D{Len1: len(decoded), Len2: len(input), EqualFunc: func(i, j int) bool {
		return decoded[i] == input[j]
	}})

	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
		t.Error("Differences detected ", delta)
	}
}

func u2s(b uint64, l byte) (result string) {
	for i := byte(0); i < l; i++ {
		if (b & 1) > 0 {
			result += "1"
		} else {
			result += "0"
		}
		b >>= 1
	}
	return
}