typeinfo.go

// Copyright (c) 2022 Blockwatch Data Inc.
// Author: alex@blockwatch.cc

package micheline

import (
	"encoding"
	"fmt"
	"reflect"
	"strconv"
	"strings"
	"sync"
)

const tagName = "prim"

// typeInfo holds details for the representation of a type.
type typeInfo struct {
	fields []fieldInfo
}

// fieldInfo holds details for the representation of a single field.
type fieldInfo struct {
	idx    []int  // Go struct index
	name   string // field name (= Go struct name)
	typ    OpCode
	path   []int
	nofail bool
}

func (f fieldInfo) String() string {
	return fmt.Sprintf("FieldInfo: name=%s typ=%s goloc=%v primloc=%v", f.name, f.typ, f.idx, f.path)
}

var tinfoMap = make(map[reflect.Type]*typeInfo)
var tinfoLock sync.RWMutex

var (
	binaryUnmarshalerType = reflect.TypeOf((*encoding.BinaryUnmarshaler)(nil)).Elem()
	// binaryMarshalerType   = reflect.TypeOf((*encoding.BinaryMarshaler)(nil)).Elem()
	textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
	// textMarshalerType     = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
	primUnmarshalerType = reflect.TypeOf((*PrimUnmarshaler)(nil)).Elem()
	// primMarshalerType     = reflect.TypeOf((*PrimMarshaler)(nil)).Elem()
	// stringerType  = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
	byteSliceType = reflect.TypeOf([]byte(nil))
	szPrim        = int(reflect.TypeOf(Prim{}).Size())
)

func canTypUnmarshalBinary(typ reflect.Type) bool {
	return reflect.PointerTo(typ).Implements(binaryUnmarshalerType) ||
		typ.Implements(binaryUnmarshalerType)
}

func canTypUnmarshalText(typ reflect.Type) bool {
	return reflect.PointerTo(typ).Implements(textUnmarshalerType) ||
		typ.Implements(textUnmarshalerType)
}

// getTypeInfo returns the typeInfo structure with details necessary
// for marshaling and unmarshaling of typ.
func getTypeInfo(typ reflect.Type) (*typeInfo, error) {
	tinfoLock.RLock()
	tinfo, ok := tinfoMap[typ]
	tinfoLock.RUnlock()
	if ok {
		return tinfo, nil
	}
	tinfo = &typeInfo{}
	if typ.Kind() != reflect.Struct {
		primType, err := mapGoTypeToPrimType(typ)
		if err != nil {
			return nil, fmt.Errorf("micheline: %v", err)
		}
		tinfo.fields = []fieldInfo{{typ: primType}}
		return tinfo, nil
	}
	n := typ.NumField()
	for i := 0; i < n; i++ {
		f := typ.Field(i)
		if (f.PkgPath != "" && !f.Anonymous) || f.Tag.Get(tagName) == "-" {
			continue // Private field
		}

		// For embedded structs, embed their fields.
		if f.Anonymous {
			t := f.Type
			if t.Kind() == reflect.Ptr {
				t = t.Elem()
			}
			if t.Kind() == reflect.Struct {
				inner, err := getTypeInfo(t)
				if err != nil {
					return nil, err
				}
				for _, finfo := range inner.fields {
					finfo.idx = append([]int{i}, finfo.idx...)
					if err := addFieldInfo(typ, tinfo, &finfo); err != nil {
						return nil, err
					}
				}
				continue
			}
		}

		finfo, err := structFieldInfo(&f)
		if err != nil {
			return nil, err
		}

		// Add the field if it doesn't conflict with other fields.
		if err := addFieldInfo(typ, tinfo, finfo); err != nil {
			return nil, err
		}
	}
	tinfoLock.Lock()
	tinfoMap[typ] = tinfo
	tinfoLock.Unlock()
	return tinfo, nil
}

// structFieldInfo builds and returns a fieldInfo for f.
func structFieldInfo(f *reflect.StructField) (*fieldInfo, error) {
	finfo := &fieldInfo{
		idx:  f.Index,
		name: f.Name,
	}
	tag := f.Tag.Get(tagName)

	// Parse struct tag
	tokens := strings.Split(tag, ",")
	if len(tokens) > 1 {
		finfo.name = tokens[0]
		for _, flag := range tokens[1:] {
			ff := strings.Split(flag, "=")
			switch ff[0] {
			case "path":
				for _, v := range strings.Split(strings.TrimSuffix(strings.TrimPrefix(ff[1], "/"), "/"), "/") {
					i, err := strconv.Atoi(v)
					if err != nil {
						return nil, fmt.Errorf("micheline: invalid path %q in field %s: %v", ff[1], f.Name, err)
					}
					finfo.path = append(finfo.path, i)
				}
			case "nofail":
				finfo.nofail = true
			}
		}
	}
	if typ, err := mapGoTypeToPrimType(f.Type); err != nil {
		return nil, fmt.Errorf("micheline: field %s: %v", finfo.name, err)
	} else {
		finfo.typ = typ
	}

	return finfo, nil
}

func mapGoTypeToPrimType(typ reflect.Type) (oc OpCode, err error) {
	switch typ.Kind() {
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		oc = T_NAT
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		oc = T_INT
	case reflect.Slice:
		switch {
		case canTypUnmarshalBinary(typ):
			oc = T_BYTES
		case canTypUnmarshalText(typ):
			oc = T_STRING
		case typ == byteSliceType:
			oc = T_BYTES
		default:
			oc = T_LIST
		}
	case reflect.Map:
		oc = T_MAP
	case reflect.String:
		oc = T_STRING
	case reflect.Bool:
		oc = T_BOOL
	case reflect.Array:
		switch typ.String() {
		case "tezos.Address":
			oc = T_ADDRESS
		case "tezos.ChainIdHash":
			oc = T_CHAIN_ID
		default:
			if canTypUnmarshalBinary(typ) {
				oc = T_BYTES
			} else {
				err = fmt.Errorf("unsupported embedded array type %s", typ.String())
			}
		}
	case reflect.Struct:
		switch typ.String() {
		case "time.Time":
			oc = T_TIMESTAMP
		case "tezos.Z":
			oc = T_NAT
		case "tezos.N":
			oc = T_NAT
		case "tezos.Key":
			oc = T_KEY
		case "tezos.Signature":
			oc = T_SIGNATURE
		default:
			if canTypUnmarshalBinary(typ) {
				oc = T_BYTES
			} else {
				err = fmt.Errorf("unsupported embedded struct type %s", typ.String())
			}
		}
	default:
		err = fmt.Errorf("unsupported type %s (%v)", typ.String(), typ.Kind())
	}
	return
}

func addFieldInfo(typ reflect.Type, tinfo *typeInfo, newf *fieldInfo) error {
	var conflicts []int
	// Find all conflicts.
	for i := range tinfo.fields {
		oldf := &tinfo.fields[i]
		if newf.name == oldf.name {
			conflicts = append(conflicts, i)
		}
	}

	// Return the first error.
	for _, i := range conflicts {
		oldf := &tinfo.fields[i]
		f1 := typ.FieldByIndex(oldf.idx)
		f2 := typ.FieldByIndex(newf.idx)
		return fmt.Errorf("micheline: %s field %q with tag %q conflicts with field %q with tag %q", typ, f1.Name, f1.Tag.Get(tagName), f2.Name, f2.Tag.Get(tagName))
	}

	// Without conflicts, add the new field and return.
	tinfo.fields = append(tinfo.fields, *newf)
	return nil
}

// value returns v's field value corresponding to finfo.
// It's equivalent to v.FieldByIndex(finfo.idx), but initializes
// and dereferences pointers as necessary.
func (finfo *fieldInfo) value(v reflect.Value) reflect.Value {
	for i, x := range finfo.idx {
		if i > 0 {
			t := v.Type()
			if t.Kind() == reflect.Ptr && t.Elem().Kind() == reflect.Struct {
				if v.IsNil() {
					v.Set(reflect.New(v.Type().Elem()))
				}
				v = v.Elem()
			}
		}
		v = v.Field(x)
	}

	return v
}

func derefValue(val reflect.Value) reflect.Value {
	if val.Kind() == reflect.Interface && !val.IsNil() {
		e := val.Elem()
		if e.Kind() == reflect.Ptr && !e.IsNil() {
			val = e
		}
	}

	if val.Kind() == reflect.Ptr {
		if val.IsNil() {
			val.Set(reflect.New(val.Type().Elem()))
		}
		val = val.Elem()
	}
	return val
}

func indirectType(typ reflect.Type) reflect.Type {
	if typ.Kind() == reflect.Ptr {
		val := reflect.New(typ.Elem())
		return val.Elem().Type()
	}
	return typ
}