package tokenize

// ByteMode provides byte-driven input/output functionality for the tokenize API.
type ByteMode struct {
	api *API
}

// Peek returns the byte at the provided byte offset.
//
// When an error occurs during reading the input, an error will be returned.
// When an offset is requested that is beyond the length of the available input
// data, then the error will be io.EOF.
func (byteMode ByteMode) Peek(offset int) (byte, error) {
	a := byteMode.api
	return a.reader.ByteAt(a.stackFrame.offset + offset)
}

// Skip is used to skip over one or more bytes that were read from the input.
// This tells the tokenizer: "I've seen these bytes. They are of no interest.
// I will now continue reading after these bytes."
//
// This will merely update the position of the cursor (which keeps track of what
// line and column we are on in the input data). The bytes are not added to
// the output.
//
// After the call, byte offset 0 for PeekByte() and PeekRune() will point at
// the first byte after the skipped bytes.
func (byteMode ByteMode) Skip(b byte) {
	f := byteMode.api.stackFrame
	f.moveCursorByByte(b)
	f.offset++
}

func (byteMode ByteMode) SkipMulti(bytes ...byte) {
	f := byteMode.api.stackFrame
	for _, b := range bytes {
		f.moveCursorByByte(b)
		f.offset++
	}
}

func (byteMode ByteMode) Accept(b byte) {
	byteMode.Append(b)
	byteMode.Skip(b)
}

func (byteMode ByteMode) Append(b byte) {
	a := byteMode.api
	f := a.stackFrame
	a.growOutputData(f.bytesEnd + 1)
	a.outputData[f.bytesEnd] = b
	f.bytesEnd++
}

// AcceptMulti is used to accept one or more bytes that were read from the input.
// This tells the tokenizer: "I've seen these bytes. I want to make use of them
// for the final output, so please remember them for me. I will now continue
// reading after these bytes."
//
// This will update the position of the cursor (which keeps track of what line
// and column we are on in the input data) and add the bytes to the tokenizer
// output.
//
// After the call, byte offset 0 for PeekByte() and PeekRune() will point at
// the first byte after the accepted bytes.
func (byteMode ByteMode) AcceptMulti(bytes ...byte) {
	byteMode.AppendMulti(bytes...)
	byteMode.SkipMulti(bytes...)
}

func (byteMode ByteMode) AppendMulti(bytes ...byte) {
	a := byteMode.api
	f := a.stackFrame
	curBytesEnd := f.bytesEnd
	newBytesEnd := curBytesEnd + len(bytes)

	a.growOutputData(newBytesEnd)
	copy(a.outputData[curBytesEnd:], bytes)
	f.bytesEnd = newBytesEnd
}

func (api *API) dataAddByte(b byte) {
	curBytesEnd := api.stackFrame.bytesEnd
	api.growOutputData(curBytesEnd + 1)
	api.outputData[curBytesEnd] = b
	api.stackFrame.bytesEnd++
}

func (api *API) dataSetBytes(bytes ...byte) {
	api.Output.ClearData()
	api.Byte.AppendMulti(bytes...)
}