package terminal

import (
	"strings"
	"unicode/utf8"
)

const textLimit = 64 << 10

func Text(b []byte) string {
	out := strings.Builder{}
	line := []rune{}
	col := 0
	flush := func() {
		out.WriteString(strings.TrimRight(string(line), " "))
		out.WriteByte('\n')
		line = line[:0]
		col = 0
	}
	for i := 0; i < len(b); {
		c := b[i]
		switch {
		case c == 0x1b:
			end, final := skipEscape(b, i)
			if final == 'K' {
				line = line[:min(col, len(line))]
			}
			i = end + 1
			continue
		case c == '\n':
			flush()
		case c == '\r':
			col = 0
		case c == '\b':
			col = max(0, col-1)
		case c == '\t' || c >= 0x20 && c != 0x7f:
			r, n := utf8.DecodeRune(b[i:])
			for len(line) < col {
				line = append(line, ' ')
			}
			if col < len(line) {
				line[col] = r
			} else {
				line = append(line, r)
			}
			col++
			i += n
			continue
		}
		i++
	}
	s := out.String() + strings.TrimRight(string(line), " ")
	if len(s) > textLimit {
		s = s[len(s)-textLimit:]
		s = s[strings.IndexByte(s, '\n')+1:]
	}
	return s
}

func skipEscape(b []byte, i int) (int, byte) {
	if i+1 >= len(b) {
		return i, 0
	}
	i++
	switch b[i] {
	case '[':
		for i++; i < len(b); i++ {
			if b[i] >= 0x40 && b[i] <= 0x7e {
				return i, b[i]
			}
		}
		return len(b) - 1, 0
	case ']', 'P', '_', '^':
		for i++; i < len(b); i++ {
			if b[i] == 0x07 {
				return i, 0
			}
			if b[i] == 0x1b && i+1 < len(b) && b[i+1] == '\\' {
				return i + 1, 0
			}
		}
		return len(b) - 1, 0
	case '(', ')', '*', '+', '#', '%':
		return min(i+1, len(b)-1), 0
	}
	return i, 0
}