package v2

import (
	"fmt"
	"io"
)

// Reads the whole ID3v2 tag from rs
func ReadV2Tag(rs io.ReadSeeker) (*ID3v2Tag, error) {
	header, err := readHeader(rs)
	if err == ErrDoesNotUseID3v2 {
		return nil, err
	} else if err != nil {
		return nil, fmt.Errorf("could not get header: %s", err)

	}

	var read uint64 = 0
	var frames []Frame
	var padding uint32 = 0
	for {
		if read == uint64(header.Size()) {
			break
		}

		frame, err := readNextFrame(rs, header.Version())
		switch err {
		case nil:
		case ErrGotPadding:
			// take a note how many padding bytes are left and
			// return collected frames
			padding += header.Size() - uint32(read)
			return &ID3v2Tag{
				Header:  header,
				Frames:  frames,
				Padding: padding,
			}, nil

		case ErrInvalidID:
			// return what has been collected
			return &ID3v2Tag{
				Header: header,
				Frames: frames,
			}, nil

		default:
			return nil, err
		}

		frames = append(frames, frame)

		// counting how many bytes read
		if header.Version() == V2_2 {
			read += uint64(V2_2FrameHeaderSize) + uint64(frame.Header.Size())
		} else {
			read += uint64(V2_3FrameHeaderSize) + uint64(frame.Header.Size())
		}
	}

	return &ID3v2Tag{
		Header:  header,
		Frames:  frames,
		Padding: padding,
	}, nil
}