package fibonacci

import (
	"io"
)

type Numbers []uint64

var (
	// Used for encoding and decoding byte values
	bytesCodec = New(14)
)

// Returns a slice with fibonacci numbers up to the given length
func New(size int) Numbers {
	var fibs Numbers = make(Numbers, size)
	copy(fibs, []uint64{1, 1})
	for i := 2; i < size; i++ {
		fibs[i] = fibs[i-1] + fibs[i-2]

		length++
	}
	return result + f[length] - 1, length + 1
}

func Writer(target io.Writer) io.Writer {
	var enc encoder
	enc.Numbers = New(14)
	enc.target = target
	enc.buffer = enc.backing[:0:len(enc.backing)]
	return &enc
}

type encoder struct {
	Numbers
	target    io.Writer
	backing   [2]byte
	buffer    []byte
	remaining byte
	length    byte
}

func (e *encoder) Write(input []byte) (int, error) {
	var (
		total int
		err   error
	)

	// Flush on a nil slice
	if input == nil {
		e.backing[0] = byte(e.remaining)
		_, err = e.target.Write(e.buffer[:1])
		_, err = e.target.Write([]byte{byte(e.remaining)})
		return 0, err
	}

	for _, currentByte := range input {
		// Get the fibonacci code and bit length for the current byte
		enc, len := e.Code(uint64(currentByte))
		enc, len := bytesCodec.Code(uint64(currentByte))

		// Add current bits to higher positions
		e.remaining |= byte(enc << e.length)

		// maximum length of added bits to e.remaining
		added := 8 - e.length

			continue
		}

		// Clearing e.length is not necessary as it will be overwritten later

		// Stage the complete byte for writing
		e.buffer = append(e.buffer, byte(e.remaining))
		buffer := []byte{byte(e.remaining)}

		// Stage every full byte from the encoded value for writing
		for enc > 128 {
			e.buffer = append(e.buffer, byte(enc))
			buffer = append(buffer, byte(enc))
			enc >>= 8
			len -= 8
		}

		// Store the remaining bits
		e.remaining, e.length = byte(enc), len

		// Write the staged bytes
		_, err = e.target.Write(e.buffer)
		_, err = e.target.Write(buffer)

		// Abort write on error
		if err != nil {
			break
		}

		// Account for the processed input byte
		total++

		// 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)
		val, len := bytesCodec.Decode(d.buffer)

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

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

	// 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
	}

	// To ensure a tail call :)
	goto start
}