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package internal
import (
"bytes"
"encoding/json"
"fmt"
"io"
"github.com/containers/image/v5/internal/set"
)
// JSONFormatError is returned when JSON does not match expected format.
type JSONFormatError string
func (err JSONFormatError) Error() string {
return string(err)
}
// ParanoidUnmarshalJSONObject unmarshals data as a JSON object, but failing on the slightest unexpected aspect
// (including duplicated keys, unrecognized keys, and non-matching types). Uses fieldResolver to
// determine the destination for a field value, which should return a pointer to the destination if valid, or nil if the key is rejected.
//
// The fieldResolver approach is useful for decoding the Policy.Transports map; using it for structs is a bit lazy,
// we could use reflection to automate this. Later?
func ParanoidUnmarshalJSONObject(data []byte, fieldResolver func(string) any) error {
seenKeys := set.New[string]()
dec := json.NewDecoder(bytes.NewReader(data))
t, err := dec.Token()
if err != nil {
return JSONFormatError(err.Error())
}
if t != json.Delim('{') {
return JSONFormatError(fmt.Sprintf("JSON object expected, got \"%s\"", t))
}
for {
t, err := dec.Token()
if err != nil {
return JSONFormatError(err.Error())
}
if t == json.Delim('}') {
break
}
key, ok := t.(string)
if !ok {
// Coverage: This should never happen, dec.Token() rejects non-string-literals in this state.
return JSONFormatError(fmt.Sprintf("Key string literal expected, got \"%s\"", t))
}
if seenKeys.Contains(key) {
return JSONFormatError(fmt.Sprintf("Duplicate key \"%s\"", key))
}
seenKeys.Add(key)
valuePtr := fieldResolver(key)
if valuePtr == nil {
return JSONFormatError(fmt.Sprintf("Unknown key \"%s\"", key))
}
// This works like json.Unmarshal, in particular it allows us to implement UnmarshalJSON to implement strict parsing of the field value.
if err := dec.Decode(valuePtr); err != nil {
return JSONFormatError(err.Error())
}
}
if _, err := dec.Token(); err != io.EOF {
return JSONFormatError("Unexpected data after JSON object")
}
return nil
}
// ParanoidUnmarshalJSONObjectExactFields unmarshals data as a JSON object, but failing on the slightest unexpected aspect
// (including duplicated keys, unrecognized keys, and non-matching types). Each of the fields in exactFields
// must be present exactly once, and none other fields are accepted.
func ParanoidUnmarshalJSONObjectExactFields(data []byte, exactFields map[string]any) error {
seenKeys := set.New[string]()
if err := ParanoidUnmarshalJSONObject(data, func(key string) any {
if valuePtr, ok := exactFields[key]; ok {
seenKeys.Add(key)
return valuePtr
}
return nil
}); err != nil {
return err
}
for key := range exactFields {
if !seenKeys.Contains(key) {
return JSONFormatError(fmt.Sprintf(`Key "%s" missing in a JSON object`, key))
}
}
return nil
}
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