feat(args): create a specialized type to manage invocation Arguments

pkg/args/args.go

@@ -0,0 +1,206 @@
+// Package args provides the type that represents the Arguments passed to
+// a command within an invocation.Token as well as a convenient Add method
+// to incrementally build the underlying map.
+package args
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+
+	"github.com/ipfs/go-cid"
+	"github.com/ipld/go-ipld-prime"
+	"github.com/ipld/go-ipld-prime/node/bindnode"
+	"github.com/ipld/go-ipld-prime/schema"
+	"github.com/ucan-wg/go-ucan/pkg/policy/literal"
+)
+
+const (
+	argsSchema = "type Args { String : Any }"
+	argsName   = "Args"
+)
+
+var (
+	once sync.Once
+	ts   *schema.TypeSystem
+	err  error
+)
+
+func argsType() schema.Type {
+	once.Do(func() {
+		ts, err = ipld.LoadSchemaBytes([]byte(argsSchema))
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	return ts.TypeByName(argsName)
+}
+
+var ErrUnsupported = fmt.Errorf("failure adding unsupported type to meta")
+
+// Args are the Command's argumennts when an invocation Token is processed
+// by the executor.
+//
+// This type must be compatible with the IPLD type represented by the IPLD
+// schema { String : Any }.
+type Args struct {
+	Keys   []string
+	Values map[string]ipld.Node
+}
+
+// New returns a pointer to an initialized Args value.
+func New() *Args {
+	return &Args{
+		Values: map[string]ipld.Node{},
+	}
+}
+
+// FromIPLD unwraps an Args instance from an ipld.Node.
+func FromIPLD(node ipld.Node) (*Args, error) {
+	var err error
+
+	defer func() {
+		err = handlePanic(recover())
+	}()
+
+	obj := bindnode.Unwrap(node)
+
+	args, ok := obj.(*Args)
+	if !ok {
+		err = fmt.Errorf("failed to convert to Args")
+	}
+
+	return args, err
+}
+
+// Add inserts a key/value pair in the Args set.
+//
+// Accepted types for val are: bool, string, int, int8, int16,
+// int32, int64, uint, uint8, uint16, uint32, float32, float64, []byte,
+// []any, map[string]any, ipld.Node and nil.
+func (m *Args) Add(key string, val any) error {
+	if _, ok := m.Values[key]; ok {
+		return fmt.Errorf("duplicate key %q", key)
+	}
+
+	node, err := anyNode(val)
+	if err != nil {
+		return err
+	}
+
+	m.Values[key] = node
+	m.Keys = append(m.Keys, key)
+
+	return nil
+}
+
+// Include merges the provided arguments into the existing arguments.
+//
+// If duplicate keys are encountered, the new value is silently dropped
+// without causing an error.
+func (m *Args) Include(other *Args) {
+	for _, key := range other.Keys {
+		if _, ok := m.Values[key]; ok {
+			// don't overwrite
+			continue
+		}
+		m.Values[key] = other.Values[key]
+		m.Keys = append(m.Keys, key)
+	}
+}
+
+// ToIPLD wraps an instance of an Args with an ipld.Node.
+func (m *Args) ToIPLD() (ipld.Node, error) {
+	var err error
+
+	defer func() {
+		err = handlePanic(recover())
+	}()
+
+	return bindnode.Wrap(m, argsType()), err
+}
+
+func anyNode(val any) (ipld.Node, error) {
+	var err error
+
+	defer func() {
+		err = handlePanic(recover())
+	}()
+
+	if val == nil {
+		return literal.Null(), nil
+	}
+
+	if cast, ok := val.(ipld.Node); ok {
+		return cast, nil
+	}
+
+	if cast, ok := val.(cid.Cid); ok {
+		return literal.LinkCid(cast), err
+	}
+
+	var rv reflect.Value
+
+	rv.Kind()
+
+	if cast, ok := val.(reflect.Value); ok {
+		rv = cast
+	} else {
+		rv = reflect.ValueOf(val)
+	}
+
+	for rv.Kind() == reflect.Ptr || rv.Kind() == reflect.Interface {
+		rv = rv.Elem()
+	}
+
+	switch rv.Kind() {
+	case reflect.Slice:
+		if rv.Type().Elem().Kind() == reflect.Uint8 {
+			return literal.Bytes(val.([]byte)), nil
+		}
+
+		l := make([]reflect.Value, rv.Len())
+
+		for i := 0; i < rv.Len(); i++ {
+			l[i] = rv.Index(i)
+		}
+
+		return literal.List(l)
+	case reflect.Map:
+		if rv.Type().Key().Kind() != reflect.String {
+			return nil, fmt.Errorf("unsupported map key type: %s", rv.Type().Key().Name())
+		}
+
+		m := make(map[string]reflect.Value, rv.Len())
+		it := rv.MapRange()
+
+		for it.Next() {
+			m[it.Key().String()] = it.Value()
+		}
+
+		return literal.Map(m)
+	case reflect.String:
+		return literal.String(rv.String()), nil
+	case reflect.Bool:
+		return literal.Bool(rv.Bool()), nil
+		// reflect.Int64 may exceed the safe 53-bit limit of JavaScript
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return literal.Int(rv.Int()), nil
+	// reflect.Uint64 can't be safely converted to int64
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32:
+		return literal.Int(int64(rv.Uint())), nil
+	case reflect.Float32, reflect.Float64:
+		return literal.Float(rv.Float()), nil
+	default:
+		return nil, fmt.Errorf("unsupported Args type: %s", rv.Type().Name())
+	}
+}
+
+func handlePanic(rec any) error {
+	if err, ok := rec.(error); ok {
+		return err
+	}
+
+	return fmt.Errorf("%v", rec)
+}