package policy

import "regexp"

// InboundRule captures one account's read-side filtering.
type InboundRule struct {
	WhitelistInEnabled bool
	WhitelistIn        []string
	SubjectRegex       *regexp.Regexp // nil = no subject filter
}

// CompileSubject compiles a subject filter; empty pattern => (nil, nil).
func CompileSubject(pattern string) (*regexp.Regexp, error) {
	if pattern == "" {
		return nil, nil
	}
	return regexp.Compile(pattern)
}

// Allows reports whether a message with the given sender and subject is visible.
func (r InboundRule) Allows(from, subject string) bool {
	if r.WhitelistInEnabled && !MatchAddress(r.WhitelistIn, from) {
		return false
	}
	if r.SubjectRegex != nil && !r.SubjectRegex.MatchString(subject) {
		return false
	}
	return true
}