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// Copyright 2020 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package internal
import (
"fmt"
"strconv"
"strings"
"unicode"
"cuelang.org/go/cue/errors"
"cuelang.org/go/cue/literal"
"cuelang.org/go/cue/token"
)
// AttrKind indicates the location of an attribute within CUE source.
type AttrKind uint8
const (
// FieldAttr indicates an attribute is a field attribute.
// foo: bar @attr()
FieldAttr AttrKind = 1 << iota
// DeclAttr indicates an attribute was specified at a declaration position.
// foo: {
// @attr()
// }
DeclAttr
// TODO: Possible future attr kinds
// ElemAttr
// FileAttr
// ValueAttr = FieldAttr|DeclAttr|ElemAttr
)
// Attr holds positional information for a single Attr.
type Attr struct {
Name string // e.g. "json" or "protobuf"
Body string
Kind AttrKind
Fields []KeyValue
Err error
}
// NewNonExisting creates a non-existing attribute.
func NewNonExisting(key string) Attr {
const msgNotExist = "attribute %q does not exist"
return Attr{Err: errors.Newf(token.NoPos, msgNotExist, key)}
}
type KeyValue struct {
data string
equal int // index of equal sign or 0 if non-existing
}
func (kv *KeyValue) Text() string { return kv.data }
func (kv *KeyValue) Key() string {
if kv.equal == 0 {
return kv.data
}
s := kv.data[:kv.equal]
s = strings.TrimSpace(s)
return s
}
func (kv *KeyValue) Value() string {
if kv.equal == 0 {
return ""
}
return strings.TrimSpace(kv.data[kv.equal+1:])
}
func (a *Attr) hasPos(p int) error {
if a.Err != nil {
return a.Err
}
if p >= len(a.Fields) {
return fmt.Errorf("field does not exist")
}
return nil
}
// String reports the possibly empty string value at the given position or
// an error the attribute is invalid or if the position does not exist.
func (a *Attr) String(pos int) (string, error) {
if err := a.hasPos(pos); err != nil {
return "", err
}
return a.Fields[pos].Text(), nil
}
// Int reports the integer at the given position or an error if the attribute is
// invalid, the position does not exist, or the value at the given position is
// not an integer.
func (a *Attr) Int(pos int) (int64, error) {
if err := a.hasPos(pos); err != nil {
return 0, err
}
// TODO: use CUE's literal parser once it exists, allowing any of CUE's
// number types.
return strconv.ParseInt(a.Fields[pos].Text(), 10, 64)
}
// Flag reports whether an entry with the given name exists at position pos or
// onwards or an error if the attribute is invalid or if the first pos-1 entries
// are not defined.
func (a *Attr) Flag(pos int, key string) (bool, error) {
if err := a.hasPos(pos - 1); err != nil {
return false, err
}
for _, kv := range a.Fields[pos:] {
if kv.Text() == key {
return true, nil
}
}
return false, nil
}
// Lookup searches for an entry of the form key=value from position pos onwards
// and reports the value if found. It reports an error if the attribute is
// invalid or if the first pos-1 entries are not defined.
func (a *Attr) Lookup(pos int, key string) (val string, found bool, err error) {
if err := a.hasPos(pos - 1); err != nil {
return "", false, err
}
for _, kv := range a.Fields[pos:] {
if kv.Key() == key {
return kv.Value(), true, nil
}
}
return "", false, nil
}
func ParseAttrBody(pos token.Pos, s string) (a Attr) {
a.Body = s
i := 0
for {
i += skipSpace(s[i:])
// always scan at least one, possibly empty element.
n, err := scanAttributeElem(pos, s[i:], &a)
if err != nil {
return Attr{Err: err}
}
if i += n; i >= len(s) {
break
}
i += skipSpace(s[i:])
if s[i] != ',' {
return Attr{Err: errors.Newf(pos, "invalid attribute: expected comma")}
}
i++
}
return a
}
func skipSpace(s string) int {
for n, r := range s {
if !unicode.IsSpace(r) {
return n
}
}
return 0
}
func scanAttributeElem(pos token.Pos, s string, a *Attr) (n int, err errors.Error) {
// try CUE string
kv := KeyValue{}
if n, kv.data, err = scanAttributeString(pos, s); n == 0 {
// try key-value pair
p := strings.IndexAny(s, ",=") // ) is assumed to be stripped.
switch {
case p < 0:
kv.data = strings.TrimSpace(s)
n = len(s)
default: // ','
n = p
kv.data = strings.TrimSpace(s[:n])
case s[p] == '=':
kv.equal = p
offset := p + 1
offset += skipSpace(s[offset:])
var str string
if p, str, err = scanAttributeString(pos, s[offset:]); p > 0 {
n = offset + p
kv.data = s[:offset] + str
} else {
n = len(s)
if p = strings.IndexByte(s[offset:], ','); p >= 0 {
n = offset + p
}
kv.data = strings.TrimSpace(s[:n])
}
}
}
if a != nil {
a.Fields = append(a.Fields, kv)
}
return n, err
}
func scanAttributeString(pos token.Pos, s string) (n int, str string, err errors.Error) {
if s == "" || (s[0] != '#' && s[0] != '"' && s[0] != '\'') {
return 0, "", nil
}
nHash := 0
for {
if nHash < len(s) {
if s[nHash] == '#' {
nHash++
continue
}
if s[nHash] == '\'' || s[nHash] == '"' {
break
}
}
return nHash, s[:nHash], errors.Newf(pos, "invalid attribute string")
}
// Determine closing quote.
nQuote := 1
if c := s[nHash]; nHash+6 < len(s) && s[nHash+1] == c && s[nHash+2] == c {
nQuote = 3
}
close := s[nHash:nHash+nQuote] + s[:nHash]
// Search for closing quote.
index := strings.Index(s[len(close):], close)
if index == -1 {
return len(s), "", errors.Newf(pos, "attribute string not terminated")
}
index += 2 * len(close)
s, err2 := literal.Unquote(s[:index])
if err2 != nil {
return index, "", errors.Newf(pos, "invalid attribute string: %v", err2)
}
return index, s, nil
}