package mcpex
import (
"encoding/json"
"fmt"
"github.com/google/jsonschema-go/jsonschema"
)
// applySchema validates whether data is valid JSON according to the provided
// schema, after applying schema defaults.
//
// Returns the JSON value augmented with defaults.
func applySchema(data json.RawMessage, resolved *jsonschema.Resolved) (json.RawMessage, error) {
// TODO: use reflection to create the struct type to unmarshal into.
// Separate validation from assignment.
// Use default JSON marshalling for validation.
//
// This avoids inconsistent representation due to custom marshallers, such as
// time.Time (issue #449).
//
// Additionally, unmarshalling into a map ensures that the resulting JSON is
// at least {}, even if data is empty. For example, arguments is technically
// an optional property of callToolParams, and we still want to apply the
// defaults in this case.
//
// TODO(rfindley): in which cases can resolved be nil?
if resolved != nil {
v := make(map[string]any)
if len(data) > 0 {
if err := json.Unmarshal(data, &v); err != nil {
return nil, fmt.Errorf("unmarshaling arguments: %w", err)
}
}
if err := resolved.ApplyDefaults(&v); err != nil {
return nil, fmt.Errorf("applying schema defaults:\n%w", err)
}
if err := resolved.Validate(&v); err != nil {
return nil, err
}
// We must re-marshal with the default values applied.
var err error
data, err = json.Marshal(v)
if err != nil {
return nil, fmt.Errorf("marshalling with defaults: %v", err)
}
}
return data, nil
}
