func compilePrefixNumDate()

in match/compile.go [85:135]

• 40 lines of code
• 7 McCabe index (conditional complexity)

func compilePrefixNumDate(r *syntax.Regexp) (stringMatcher, error) {
	m := &prefixNumDate{}

	i := 1
	if r.Sub[i].Op == syntax.OpLiteral {
		m.prefix = []byte(string(r.Sub[i].Rune))
		i++
	}

	digitLen := func(r *syntax.Regexp) int {
		if r.Op == syntax.OpConcat {
			return len(r.Sub)
		}
		return 1
	}

	var digits []int
	var seps [][]byte

	digits = append(digits, digitLen(r.Sub[i]))
	i++

	for i < len(r.Sub) {
		lit := []byte(string(r.Sub[i].Rune))
		i++

		// capture literal suffix
		if i == len(r.Sub) {
			m.suffix = lit
			break
		}

		seps = append(seps, lit)
		digits = append(digits, digitLen(r.Sub[i]))
		i++
	}

	minLen := len(m.prefix) + len(m.suffix)
	for _, d := range digits {
		minLen += d
	}
	for _, sep := range seps {
		minLen += len(sep)
	}

	m.digits = digits
	m.seps = seps
	m.minLen = minLen

	return m, nil
}