gotosocial/vendor/github.com/grpc-ecosystem/grpc-gateway/v2/internal/httprule/parse.go
2023-05-09 18:19:48 +01:00

369 lines
8.2 KiB
Go

package httprule
import (
"fmt"
"strings"
)
// InvalidTemplateError indicates that the path template is not valid.
type InvalidTemplateError struct {
tmpl string
msg string
}
func (e InvalidTemplateError) Error() string {
return fmt.Sprintf("%s: %s", e.msg, e.tmpl)
}
// Parse parses the string representation of path template
func Parse(tmpl string) (Compiler, error) {
if !strings.HasPrefix(tmpl, "/") {
return template{}, InvalidTemplateError{tmpl: tmpl, msg: "no leading /"}
}
tokens, verb := tokenize(tmpl[1:])
p := parser{tokens: tokens}
segs, err := p.topLevelSegments()
if err != nil {
return template{}, InvalidTemplateError{tmpl: tmpl, msg: err.Error()}
}
return template{
segments: segs,
verb: verb,
template: tmpl,
}, nil
}
func tokenize(path string) (tokens []string, verb string) {
if path == "" {
return []string{eof}, ""
}
const (
init = iota
field
nested
)
st := init
for path != "" {
var idx int
switch st {
case init:
idx = strings.IndexAny(path, "/{")
case field:
idx = strings.IndexAny(path, ".=}")
case nested:
idx = strings.IndexAny(path, "/}")
}
if idx < 0 {
tokens = append(tokens, path)
break
}
switch r := path[idx]; r {
case '/', '.':
case '{':
st = field
case '=':
st = nested
case '}':
st = init
}
if idx == 0 {
tokens = append(tokens, path[idx:idx+1])
} else {
tokens = append(tokens, path[:idx], path[idx:idx+1])
}
path = path[idx+1:]
}
l := len(tokens)
// See
// https://github.com/grpc-ecosystem/grpc-gateway/pull/1947#issuecomment-774523693 ;
// although normal and backwards-compat logic here is to use the last index
// of a colon, if the final segment is a variable followed by a colon, the
// part following the colon must be a verb. Hence if the previous token is
// an end var marker, we switch the index we're looking for to Index instead
// of LastIndex, so that we correctly grab the remaining part of the path as
// the verb.
var penultimateTokenIsEndVar bool
switch l {
case 0, 1:
// Not enough to be variable so skip this logic and don't result in an
// invalid index
default:
penultimateTokenIsEndVar = tokens[l-2] == "}"
}
t := tokens[l-1]
var idx int
if penultimateTokenIsEndVar {
idx = strings.Index(t, ":")
} else {
idx = strings.LastIndex(t, ":")
}
if idx == 0 {
tokens, verb = tokens[:l-1], t[1:]
} else if idx > 0 {
tokens[l-1], verb = t[:idx], t[idx+1:]
}
tokens = append(tokens, eof)
return tokens, verb
}
// parser is a parser of the template syntax defined in github.com/googleapis/googleapis/google/api/http.proto.
type parser struct {
tokens []string
accepted []string
}
// topLevelSegments is the target of this parser.
func (p *parser) topLevelSegments() ([]segment, error) {
if _, err := p.accept(typeEOF); err == nil {
p.tokens = p.tokens[:0]
return []segment{literal(eof)}, nil
}
segs, err := p.segments()
if err != nil {
return nil, err
}
if _, err := p.accept(typeEOF); err != nil {
return nil, fmt.Errorf("unexpected token %q after segments %q", p.tokens[0], strings.Join(p.accepted, ""))
}
return segs, nil
}
func (p *parser) segments() ([]segment, error) {
s, err := p.segment()
if err != nil {
return nil, err
}
segs := []segment{s}
for {
if _, err := p.accept("/"); err != nil {
return segs, nil
}
s, err := p.segment()
if err != nil {
return segs, err
}
segs = append(segs, s)
}
}
func (p *parser) segment() (segment, error) {
if _, err := p.accept("*"); err == nil {
return wildcard{}, nil
}
if _, err := p.accept("**"); err == nil {
return deepWildcard{}, nil
}
if l, err := p.literal(); err == nil {
return l, nil
}
v, err := p.variable()
if err != nil {
return nil, fmt.Errorf("segment neither wildcards, literal or variable: %v", err)
}
return v, err
}
func (p *parser) literal() (segment, error) {
lit, err := p.accept(typeLiteral)
if err != nil {
return nil, err
}
return literal(lit), nil
}
func (p *parser) variable() (segment, error) {
if _, err := p.accept("{"); err != nil {
return nil, err
}
path, err := p.fieldPath()
if err != nil {
return nil, err
}
var segs []segment
if _, err := p.accept("="); err == nil {
segs, err = p.segments()
if err != nil {
return nil, fmt.Errorf("invalid segment in variable %q: %v", path, err)
}
} else {
segs = []segment{wildcard{}}
}
if _, err := p.accept("}"); err != nil {
return nil, fmt.Errorf("unterminated variable segment: %s", path)
}
return variable{
path: path,
segments: segs,
}, nil
}
func (p *parser) fieldPath() (string, error) {
c, err := p.accept(typeIdent)
if err != nil {
return "", err
}
components := []string{c}
for {
if _, err = p.accept("."); err != nil {
return strings.Join(components, "."), nil
}
c, err := p.accept(typeIdent)
if err != nil {
return "", fmt.Errorf("invalid field path component: %v", err)
}
components = append(components, c)
}
}
// A termType is a type of terminal symbols.
type termType string
// These constants define some of valid values of termType.
// They improve readability of parse functions.
//
// You can also use "/", "*", "**", "." or "=" as valid values.
const (
typeIdent = termType("ident")
typeLiteral = termType("literal")
typeEOF = termType("$")
)
const (
// eof is the terminal symbol which always appears at the end of token sequence.
eof = "\u0000"
)
// accept tries to accept a token in "p".
// This function consumes a token and returns it if it matches to the specified "term".
// If it doesn't match, the function does not consume any tokens and return an error.
func (p *parser) accept(term termType) (string, error) {
t := p.tokens[0]
switch term {
case "/", "*", "**", ".", "=", "{", "}":
if t != string(term) && t != "/" {
return "", fmt.Errorf("expected %q but got %q", term, t)
}
case typeEOF:
if t != eof {
return "", fmt.Errorf("expected EOF but got %q", t)
}
case typeIdent:
if err := expectIdent(t); err != nil {
return "", err
}
case typeLiteral:
if err := expectPChars(t); err != nil {
return "", err
}
default:
return "", fmt.Errorf("unknown termType %q", term)
}
p.tokens = p.tokens[1:]
p.accepted = append(p.accepted, t)
return t, nil
}
// expectPChars determines if "t" consists of only pchars defined in RFC3986.
//
// https://www.ietf.org/rfc/rfc3986.txt, P.49
// pchar = unreserved / pct-encoded / sub-delims / ":" / "@"
// unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
// sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
// / "*" / "+" / "," / ";" / "="
// pct-encoded = "%" HEXDIG HEXDIG
func expectPChars(t string) error {
const (
init = iota
pct1
pct2
)
st := init
for _, r := range t {
if st != init {
if !isHexDigit(r) {
return fmt.Errorf("invalid hexdigit: %c(%U)", r, r)
}
switch st {
case pct1:
st = pct2
case pct2:
st = init
}
continue
}
// unreserved
switch {
case 'A' <= r && r <= 'Z':
continue
case 'a' <= r && r <= 'z':
continue
case '0' <= r && r <= '9':
continue
}
switch r {
case '-', '.', '_', '~':
// unreserved
case '!', '$', '&', '\'', '(', ')', '*', '+', ',', ';', '=':
// sub-delims
case ':', '@':
// rest of pchar
case '%':
// pct-encoded
st = pct1
default:
return fmt.Errorf("invalid character in path segment: %q(%U)", r, r)
}
}
if st != init {
return fmt.Errorf("invalid percent-encoding in %q", t)
}
return nil
}
// expectIdent determines if "ident" is a valid identifier in .proto schema ([[:alpha:]_][[:alphanum:]_]*).
func expectIdent(ident string) error {
if ident == "" {
return fmt.Errorf("empty identifier")
}
for pos, r := range ident {
switch {
case '0' <= r && r <= '9':
if pos == 0 {
return fmt.Errorf("identifier starting with digit: %s", ident)
}
continue
case 'A' <= r && r <= 'Z':
continue
case 'a' <= r && r <= 'z':
continue
case r == '_':
continue
default:
return fmt.Errorf("invalid character %q(%U) in identifier: %s", r, r, ident)
}
}
return nil
}
func isHexDigit(r rune) bool {
switch {
case '0' <= r && r <= '9':
return true
case 'A' <= r && r <= 'F':
return true
case 'a' <= r && r <= 'f':
return true
}
return false
}