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parser.go
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parser.go
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// Package domainexp parses expressions containing domains.
package domainexp
import (
"strings"
"github.com/favonia/cloudflare-ddns/internal/domain"
"github.com/favonia/cloudflare-ddns/internal/pp"
)
func scanList(ppfmt pp.PP, key string, input string, tokens []string) ([]string, []string) {
var list []string
readyForNext := true
for len(tokens) > 0 {
switch tokens[0] {
case ",":
readyForNext = true
case ")":
return list, tokens
case "(", "&&", "||", "!":
ppfmt.Noticef(pp.EmojiUserError, `%s (%q) has unexpected token %q`, key, input, tokens[0])
return nil, nil
default:
if !readyForNext {
ppfmt.Noticef(pp.EmojiUserError, `%s (%q) is missing a comma "," before %q`, key, input, tokens[0])
}
list = append(list, tokens[0])
readyForNext = false
}
tokens = tokens[1:]
}
return list, tokens
}
func scanASCIIDomainList(ppfmt pp.PP, key string, input string, tokens []string) ([]string, []string) {
list, tokens := scanList(ppfmt, key, input, tokens)
domains := make([]string, 0, len(list))
for _, raw := range list {
domains = append(domains, domain.StringToASCII(raw))
}
return domains, tokens
}
func scanDomainList(ppfmt pp.PP, key string, input string, tokens []string) ([]domain.Domain, []string) {
list, tokens := scanList(ppfmt, key, input, tokens)
domains := make([]domain.Domain, 0, len(list))
for _, raw := range list {
domain, err := domain.New(raw)
if err != nil {
ppfmt.Noticef(pp.EmojiUserError,
"%s (%q) contains an ill-formed domain %q: %v",
key, input, domain.Describe(), err)
return nil, nil
}
domains = append(domains, domain)
}
return domains, tokens
}
func scanConstants(_ppfmt pp.PP, _key string, _input string, tokens []string, expected []string) (string, []string) {
if len(tokens) == 0 {
return "", nil
}
for _, expected := range expected {
if expected == tokens[0] {
return tokens[0], tokens[1:]
}
}
return "", nil
}
func scanMustConstant(ppfmt pp.PP, key string, input string, tokens []string, expected string) []string {
if len(tokens) == 0 {
ppfmt.Noticef(pp.EmojiUserError, `%s (%q) is missing %q at the end`, key, input, expected)
return nil
}
if expected == tokens[0] {
return tokens[1:]
}
ppfmt.Noticef(pp.EmojiUserError,
`%s (%q) has unexpected token %q when %q is expected`, key, input, tokens[0], expected)
return nil
}
type predicate = func(domain.Domain) bool
func hasStrictSuffix(s, suffix string) bool {
return strings.HasSuffix(s, suffix) && (len(s) > len(suffix) && s[len(s)-len(suffix)-1] == '.')
}
// scanFactor mimics ParseBool, call scanFunction, and then check parenthesized expressions.
//
// <factor> --> true | false | <fun> | ! <factor> | ( <expression> )
func scanFactor(ppfmt pp.PP, key string, input string, tokens []string) (predicate, []string) {
// fmt.Printf("scanFactor(tokens = %#v)\n", tokens)
if _, newTokens := scanConstants(ppfmt, key, input, tokens,
[]string{"1", "t", "T", "TRUE", "true", "True"}); newTokens != nil {
return func(_ domain.Domain) bool { return true }, newTokens
}
if _, newTokens := scanConstants(ppfmt, key, input, tokens,
[]string{"0", "f", "F", "FALSE", "false", "False"}); newTokens != nil {
return func(_ domain.Domain) bool { return false }, newTokens
}
{
if funName, newTokens := scanConstants(ppfmt, key, input, tokens, []string{"is", "sub"}); newTokens != nil {
newTokens = scanMustConstant(ppfmt, key, input, newTokens, "(")
if newTokens == nil {
return nil, nil
}
ASCIIDomains, newTokens := scanASCIIDomainList(ppfmt, key, input, newTokens)
if newTokens == nil {
return nil, nil
}
newTokens = scanMustConstant(ppfmt, key, input, newTokens, ")")
if newTokens == nil {
return nil, nil
}
return map[string]predicate{
"is": func(d domain.Domain) bool {
asciiD := d.DNSNameASCII()
for _, pat := range ASCIIDomains {
if pat == asciiD {
return true
}
}
return false
},
"sub": func(d domain.Domain) bool {
asciiD := d.DNSNameASCII()
for _, pat := range ASCIIDomains {
if hasStrictSuffix(asciiD, pat) {
return true
}
}
return false
},
}[funName], newTokens
}
}
{
_, newTokens := scanConstants(ppfmt, key, input, tokens, []string{"!"})
if newTokens != nil {
if pred, newTokens := scanFactor(ppfmt, key, input, newTokens); newTokens != nil {
return func(d domain.Domain) bool { return !(pred(d)) }, newTokens
}
return nil, nil
}
}
{
_, newTokens := scanConstants(ppfmt, key, input, tokens, []string{"("})
if newTokens != nil {
pred, newTokens := scanExpression(ppfmt, key, input, newTokens)
if newTokens == nil {
return nil, nil
}
newTokens = scanMustConstant(ppfmt, key, input, newTokens, ")")
if newTokens == nil {
return nil, nil
}
return pred, newTokens
}
}
if len(tokens) == 0 {
ppfmt.Noticef(pp.EmojiUserError, "%s (%q) is not a boolean expression", key, input)
} else {
ppfmt.Noticef(pp.EmojiUserError,
"%s (%q) is not a boolean expression: got unexpected token %q", key, input, tokens[0])
}
return nil, nil
}
// scanTerm scans a term with this grammar:
//
// <term> --> <factor> "&&" <term> | <factor>
func scanTerm(ppfmt pp.PP, key string, input string, tokens []string) (predicate, []string) {
// fmt.Printf("scanTerm(tokens = %#v)\n", tokens)
pred1, tokens := scanFactor(ppfmt, key, input, tokens)
if tokens == nil {
return nil, nil
}
_, newTokens := scanConstants(ppfmt, key, input, tokens, []string{"&&"})
if newTokens == nil {
return pred1, tokens
}
pred2, newTokens := scanTerm(ppfmt, key, input, newTokens)
if newTokens != nil {
return func(d domain.Domain) bool { return pred1(d) && pred2(d) }, newTokens
}
return nil, nil
}
// scanExpression scans an expression with this grammar:
//
// <expression> --> <term> "||" <expression> | <term>
func scanExpression(ppfmt pp.PP, key string, input string, tokens []string) (predicate, []string) {
pred1, tokens := scanTerm(ppfmt, key, input, tokens)
if tokens == nil {
return nil, nil
}
_, newTokens := scanConstants(ppfmt, key, input, tokens, []string{"||"})
if newTokens == nil {
return pred1, tokens
}
pred2, newTokens := scanExpression(ppfmt, key, input, newTokens)
if newTokens != nil {
return func(d domain.Domain) bool { return pred1(d) || pred2(d) }, newTokens
}
return nil, nil
}
// ParseList parses a list of comma-separated domains. Internationalized domain names are fully supported.
func ParseList(ppfmt pp.PP, key string, input string) ([]domain.Domain, bool) {
tokens, ok := tokenize(ppfmt, key, input)
if !ok {
return nil, false
}
list, tokens := scanDomainList(ppfmt, key, input, tokens)
if tokens == nil {
return nil, false
} else if len(tokens) > 0 {
ppfmt.Noticef(pp.EmojiUserError, `%s (%q) has unexpected token %q`, key, input, tokens[0])
return nil, false
}
return list, true
}
// ParseExpression parses a boolean expression containing domains. Internationalized domain names are fully supported.
// A boolean expression must have one of the following forms:
//
// - A boolean value accepted by [strconv.ParseBool], such as t as true or FALSE as false.
// - is(example.org), which matches the domain example.org. Note that is(*.example.org)
// only matches the wildcard domain *.example.org; use sub(example.org) to match
// all subdomains of example.org (including *.example.org).
// - sub(example.org), which matches subdomains of example.org, such as www.example.org and *.example.org.
// It does not match the domain example.org itself.
// - ! exp, where exp is a boolean expression, representing logical negation of exp.
// - exp1 || exp2, where exp1 and exp2 are boolean expressions, representing logical disjunction of exp1 and exp2.
// - exp1 && exp2, where exp1 and exp2 are boolean expressions, representing logical conjunction of exp1 and exp2.
//
// One can use parentheses to group expressions, such as !(is(hello.org) && (is(hello.io) || is(hello.me))).
func ParseExpression(ppfmt pp.PP, key string, input string) (predicate, bool) {
tokens, ok := tokenize(ppfmt, key, input)
if !ok {
return nil, false
}
pred, tokens := scanExpression(ppfmt, key, input, tokens)
if tokens == nil {
return nil, false
} else if len(tokens) > 0 {
ppfmt.Noticef(pp.EmojiUserError, "%s (%q) has unexpected token %q", key, input, tokens[0])
return nil, false
}
return pred, true
}