Let task agents read and type into the task's terminal

internal/terminal/text.go

@@ -0,0 +1,87 @@
+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
+}