id3ed/v2/frame.go

package v2

import (
	"fmt"
	"io"

	"github.com/Unbewohnte/id3ed/util"
)

type FrameFlags struct {
	TagAlterPreservation  bool
	FileAlterPreservation bool
	ReadOnly              bool
	Compressed            bool
	Encrypted             bool
	InGroup               bool
}

type Frame struct {
	ID        string
	Size      int64
	Flags     FrameFlags
	GroupByte byte
	Contents  []byte
}

// Reads ID3v2.3.0 or ID3v2.4.0 frame
func ReadFrame(rs io.Reader) (*Frame, error) {
	var frame Frame

	// ID
	identifier, err := util.ReadToString(rs, 4)
	if err != nil {
		return nil, err
	}
	frame.ID = identifier

	// Size
	framesizeBytes, err := util.Read(rs, 4)
	if err != nil {
		return nil, err
	}

	framesize, err := util.BytesToIntIgnoreFirstBit(framesizeBytes)
	if err != nil {
		return nil, err
	}

	frame.Size = framesize

	// Flags

	frameFlagsByte1, err := util.Read(rs, 1)
	if err != nil {
		return nil, err
	}

	frameFlagsByte2, err := util.Read(rs, 1)
	if err != nil {
		return nil, err
	}

	// I don`t have enough knowledge to handle this more elegantly
	// Any pointers ?

	flagsByte1Bits := fmt.Sprintf("%08b", frameFlagsByte1)
	flagsByte2Bits := fmt.Sprintf("%08b", frameFlagsByte2)
	var flags FrameFlags

	if flagsByte1Bits[0] == 1 {
		flags.TagAlterPreservation = true
	} else {
		flags.TagAlterPreservation = false
	}
	if flagsByte1Bits[1] == 1 {
		flags.FileAlterPreservation = true
	} else {
		flags.FileAlterPreservation = false
	}
	if flagsByte1Bits[2] == 1 {
		flags.ReadOnly = true
	} else {
		flags.ReadOnly = false
	}
	if flagsByte2Bits[0] == 1 {
		flags.Compressed = true
	} else {
		flags.Compressed = false
	}
	if flagsByte2Bits[1] == 1 {
		flags.Encrypted = true
	} else {
		flags.Encrypted = false
	}
	if flagsByte2Bits[2] == 1 {
		flags.InGroup = true
	} else {
		flags.InGroup = false
	}

	frame.Flags = flags

	if flags.InGroup {
		groupByte, err := util.Read(rs, 1)
		if err != nil {
			return nil, err
		}
		frame.GroupByte = groupByte[0]
	}

	// Body
	frameContents, err := util.Read(rs, uint64(framesize))
	if err != nil {
		return nil, err
	}

	frame.Contents = frameContents

	return &frame, nil
}

// Reads ID3v2 frames from rs. NOT TESTED !!!!
func GetFrames(rs io.ReadSeeker) ([]*Frame, error) {
	header, err := GetHeader(rs)
	if err != nil {
		return nil, err
	}

	tagsize := header.Size

	fmt.Println("NEED TO READ ", tagsize)

	var frames []*Frame
	var read uint64 = 0
	for {
		if read == uint64(tagsize) {
			break
		}

		frame, err := ReadFrame(rs)
		if err != nil {
			return frames, fmt.Errorf("could not read frame: %s", err)
		}
		frames = append(frames, frame)

		// counting how many bytes has been read
		read += 10 // frame header
		if frame.Flags.InGroup {
			// header has 1 additional byte
			read += 1
		}
		read += uint64(frame.Size) // and the contents itself

		fmt.Println("Read: ", read, "  ", frame.ID)
	}

	return frames, nil
}