package util

import (
	"io"
	"regexp"
)

const ANSI_REGEX string = "\x1b[[0-9;]*m"

// Strip ansi control characters from source
//
// The source reader is automatically closed when stripper reader is
type AnsiFilterReadCloser struct {
	regex      regexp.Regexp
	readCloser io.ReadCloser
}

func NewAnsiFilterReadCloser(readCloser io.ReadCloser) *AnsiFilterReadCloser {
	r := new(AnsiFilterReadCloser)
	r.regex = *regexp.MustCompile(ANSI_REGEX)
	r.readCloser = readCloser

	return r
}

func (rc AnsiFilterReadCloser) Read(p []byte) (int, error) {
	n, err := rc.readCloser.Read(p)
	if err != io.EOF && err != nil {
		return n, err
	}

	filtered := rc.regex.ReplaceAll(p[:n], []byte(""))
	n = copy(p, filtered)

	return n, err
}

func (rc AnsiFilterReadCloser) Close() error {
	return rc.readCloser.Close()
}

type AnsiFilterWriter struct {
	regex  regexp.Regexp
	writer io.Writer
}

func NewAnsiFilterWriter(writer io.Writer) *AnsiFilterWriter {
	w := new(AnsiFilterWriter)
	w.regex = *regexp.MustCompile(ANSI_REGEX)
	w.writer = writer

	return w
}

func (w AnsiFilterWriter) Write(p []byte) (int, error) {
	filtered := w.regex.ReplaceAll(p, []byte(""))

	n, err := w.writer.Write(filtered)

	if n < len(filtered) {
		return n, io.ErrShortWrite
	}

	// NOTE: report the original size not the filtered size to indicate to caller
    //       that input has been consumed
	return len(p), err
}