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