package meowlib

import (
	"errors"
	"strconv"
)

func min(a, b int) int {
	if a <= b {
		return a
	}
	return b
}

func BufferSplit(buffer []byte, parts uint8) (packets [][]byte, err error) {
	if int(parts) > len(buffer) {
		return nil, errors.New("too many parts(" + strconv.Itoa(int(parts)) + ") for buffer len(" + strconv.Itoa(len(buffer)) + ")")
	}
	chunksize := int(len(buffer)/int(parts)) + 1
	packets = make([][]byte, parts)
	for c := 0; c < int(parts); c++ {
		if c == 0 {
			packets[c] = []byte{byte(c), byte(parts)}
		} else {
			packets[c] = []byte{byte(c)}
		}
	}
	chunk := 0
	for i := 0; i < len(buffer); i += chunksize {
		batch := buffer[i:min(i+chunksize, len(buffer))]
		packets[chunk] = append(packets[chunk], batch...)
		chunk++
	}
	return packets, nil
}

func BufferMerge(packets [][]byte) (buffer []byte, err error) {
	var parts int
	found := false
	buffer = []byte{}
	for _, b := range packets {
		if b[0] == 0 {
			parts = int(b[1])
			buffer = append(buffer, b[2:]...)
			found = true
			break
		}
	}
	if !found {
		return nil, errors.New("start packet not found")
	}
	for i := 1; i < parts; i++ {
		found = false
		for _, b := range packets {
			if b[0] == byte(i) {
				buffer = append(buffer, b[1:]...)
				found = true
				break
			}
		}
		if !found {
			return nil, errors.New("packet #" + strconv.Itoa(i) + " not found")
		}
	}
	return buffer, nil
}