package loader

import (
	"encoding/binary"
	"fmt"
	"io"
)

// HeaderSize is the byte size of the MAK v2 header
const HeaderSize = 32

// ReadHeader reads a MAK v2 header from a reader
func ReadHeader(r io.Reader) (*Header, error) {
	var h Header
	
	if _, err := io.ReadFull(r, h.Magic[:]); err != nil {
		return nil, fmt.Errorf("reading magic: %w", err)
	}
	
	// Check magic
	if string(h.Magic[:]) != Magic {
		return nil, fmt.Errorf("invalid magic: %s", string(h.Magic[:]))
	}
	
	if err := binary.Read(r, binary.LittleEndian, &h.Version); err != nil {
		return nil, fmt.Errorf("reading version: %w", err)
	}
	if err := binary.Read(r, binary.LittleEndian, &h.Flags); err != nil {
		return nil, fmt.Errorf("reading flags: %w", err)
	}
	if err := binary.Read(r, binary.LittleEndian, &h.SectionCount); err != nil {
		return nil, fmt.Errorf("reading section count: %w", err)
	}
	if err := binary.Read(r, binary.LittleEndian, &h.Alignment); err != nil {
		return nil, fmt.Errorf("reading alignment: %w", err)
	}
	if _, err := io.ReadFull(r, h.Reserved[:]); err != nil {
		return nil, fmt.Errorf("reading reserved: %w", err)
	}
	
	return &h, nil
}

// WriteHeader writes a MAK v2 header to a writer
func WriteHeader(w io.Writer, h *Header) error {
	if _, err := w.Write(h.Magic[:]); err != nil {
		return err
	}
	if err := binary.Write(w, binary.LittleEndian, h.Version); err != nil {
		return err
	}
	if err := binary.Write(w, binary.LittleEndian, h.Flags); err != nil {
		return err
	}
	if err := binary.Write(w, binary.LittleEndian, h.SectionCount); err != nil {
		return err
	}
	if err := binary.Write(w, binary.LittleEndian, h.Alignment); err != nil {
		return err
	}
	if _, err := w.Write(h.Reserved[:]); err != nil {
		return err
	}
	return nil
}