package core

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

// BMPFileHeader represents the bitmap file header structure.
type BMPFileHeader struct {
	FileType   [2]byte
	FileSize   uint32
	Reserved1  uint16
	Reserved2  uint16
	DataOffset uint32
}

// BMPInfoHeader represents the bitmap info header structure.
type BMPInfoHeader struct {
	Size            uint32
	Width           int32
	Height          int32
	Planes          uint16
	BitsPerPixel    uint16
	Compression     uint32
	SizeImage       uint32
	XPelsPerMeter   int32
	YPelsPerMeter   int32
	ColorsUsed      uint32
	ColorsImportant uint32
}

func ReadBmpImage(filePath string) (error, int32, int32) {
	file, err := os.Open(filePath)
	if err != nil {
		fmt.Printf("=== Failed to open file: %v\n", err)
		return err, 0, 0
	}
	defer file.Close()

	// Read the file header.
	var fileHeader BMPFileHeader
	if err := binary.Read(file, binary.LittleEndian, &fileHeader); err != nil {
		fmt.Printf("=== Failed to Read file: %v\n", err)
		return err, 0, 0
	}

	// Check if it's a valid BMP file by verifying the file type.
	if string(fileHeader.FileType[:]) != "BM" {
		return fmt.Errorf("not a valid BMP file: file type is %q, expected \"BM\"", string(fileHeader.FileType[:])), 0, 0
	}

	// Read the info header.
	var infoHeader BMPInfoHeader
	if err := binary.Read(file, binary.LittleEndian, &infoHeader); err != nil {
		fmt.Printf("=== Failed to Read file: %v\n", err)
		return err, 0, 0
	}
	// 自顶向下 BMP 的高度为负值，取绝对值避免影响后续解析
	return err, absInt32(infoHeader.Width), absInt32(infoHeader.Height)
	//fmt.Printf("=== File size: %d bytes\n", fileHeader.FileSize)
	//fmt.Printf("=== Image dimensions: %dx%d\n", )
	//fmt.Printf("=== Bits per pixel: %d\n", infoHeader.BitsPerPixel)

	// At this point, you would typically read the pixel data into a slice,
	// taking into account any padding required for alignment and the specific
	// pixel format (e.g., RGB, RGBA, indexed color). This part is omitted here.

	// You may also need to skip over a possible color palette if present.
	// The size of the palette can be inferred from the number of colors used and
	// the bits per pixel value.

	// For simplicity, we'll just read the rest of the file as raw bytes.
	//data, err := ioutil.ReadAll(file)
	//if err != nil {
	//	panic(err)
	//}
	//fmt.Printf("=== Read %d bytes of pixel data.\n", len(data))
}

// absInt32 返回 int32 的绝对值
func absInt32(v int32) int32 {
	if v < 0 {
		return -v
	}
	return v
}

// ReadPsdImage 读取PSD/PSB格式的图片信息（两者共享相同的8BPS文件头）
func ReadPsdImage(filePath string) (err error, width int, height int) {
	file, err := os.Open(filePath)
	if err != nil {
		fmt.Printf("=== Failed to open file: %v\n", err)
		return err, 0, 0
	}
	defer file.Close()

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