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encoder.go
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/
encoder.go
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// Copyright 2021 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 jsonpb
import (
"strconv"
"github.com/wylswz/cue-se/cue"
"github.com/wylswz/cue-se/cue/ast"
"github.com/wylswz/cue-se/cue/errors"
"github.com/wylswz/cue-se/cue/literal"
"github.com/wylswz/cue-se/cue/token"
"github.com/wylswz/cue-se/encoding/protobuf/pbinternal"
)
// TODO: Options:
// - Convert integer strings.
// - URL encoder
// - URL decoder
// An Encoder rewrites CUE values according to the Protobuf to JSON mappings,
// based on a given CUE schema.
//
// It bases the mapping on the underlying CUE type, without consulting Protobuf
// attributes.
//
// Mappings per CUE type:
//
// for any CUE type:
// int: if the expression value is an integer and the schema value is
// an int64, it is converted to a string.
// {}: JSON objects representing any values will be left as is.
// If the CUE type corresponding to the URL can be determined within
// the module context it will be unified.
// _: Adds a `@type` URL (TODO).
type Encoder struct {
schema cue.Value
}
// NewEncoder creates an Encoder for the given schema.
func NewEncoder(schema cue.Value, options ...Option) *Encoder {
return &Encoder{schema: schema}
}
// RewriteFile modifies file, modifying it to conform to the Protocol buffer
// to JSON mapping it in terms of the given schema.
//
// RewriteFile is idempotent, calling it multiples times on an expression gives
// the same result.
func (e *Encoder) RewriteFile(file *ast.File) error {
var enc encoder
enc.rewriteDecls(e.schema, file.Decls)
return enc.errs
}
// RewriteExpr modifies file, modifying it to conform to the Protocol buffer
// to JSON mapping it in terms of the given schema.
//
// RewriteExpr is idempotent, calling it multiples times on an expression gives
// the same result.
func (e *Encoder) RewriteExpr(expr ast.Expr) (ast.Expr, error) {
var enc encoder
x := enc.rewrite(e.schema, expr)
return x, enc.errs
}
type encoder struct {
errs errors.Error
}
func (e *encoder) rewriteDecls(schema cue.Value, decls []ast.Decl) {
for _, f := range decls {
field, ok := f.(*ast.Field)
if !ok {
continue
}
sel := cue.Label(field.Label)
if !sel.IsString() {
continue
}
v := schema.LookupPath(cue.MakePath(sel.Optional()))
if !v.Exists() {
continue
}
field.Value = e.rewrite(v, field.Value)
}
}
func (e *encoder) rewrite(schema cue.Value, expr ast.Expr) (x ast.Expr) {
switch x := expr.(type) {
case *ast.ListLit:
for i, elem := range x.Elts {
v := schema.LookupPath(cue.MakePath(cue.Index(i).Optional()))
if !v.Exists() {
break
}
x.Elts[i] = e.rewrite(v, elem)
}
return expr
case *ast.StructLit:
e.rewriteDecls(schema, x.Elts)
return expr
case *ast.BasicLit:
if x.Kind != token.INT {
break
}
info, err := pbinternal.FromValue("", schema)
if err != nil {
break
}
switch info.Type {
case "int64", "fixed64", "sfixed64", "uint64":
b, ok := expr.(*ast.BasicLit)
if schema.IncompleteKind() == cue.IntKind && ok && b.Kind == token.INT {
b.Kind = token.STRING
b.Value = literal.String.Quote(b.Value)
}
case "int32", "fixed32", "sfixed32", "uint32", "float", "double":
case "varint":
default:
if !info.IsEnum {
break
}
i, err := strconv.ParseInt(x.Value, 10, 32)
if err != nil {
break
}
if s := pbinternal.MatchByInt(schema, i); s != "" {
x.Kind = token.STRING
x.Value = literal.String.Quote(s)
}
}
}
return expr
}