package probe

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

// probePsd 读取 PSD/PSB 格式的宽高（两者共享相同的 8BPS 文件头）
func probePsd(filePath string) (*ProbeResult, error) {
	f, err := os.Open(filePath)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var header [26]byte
	if _, err := io.ReadFull(f, header[:]); err != nil {
		return nil, err
	}
	if string(header[0:4]) != "8BPS" {
		return nil, fmt.Errorf("not a valid PSD/PSB file")
	}
	version := binary.BigEndian.Uint16(header[4:6])
	if version != 1 && version != 2 {
		return nil, fmt.Errorf("unsupported PSD/PSB version: %d", version)
	}
	height := int(binary.BigEndian.Uint32(header[14:18]))
	width := int(binary.BigEndian.Uint32(header[18:22]))
	return &ProbeResult{Width: width, Height: height}, nil
}