mesg-foundation/core

package process

import (
    "fmt"

    "github.com/mesg-foundation/engine/protobuf/types"
)

// Resolve returns the value specified in the reference.
func (path *Process_Node_Reference_Path) Resolve(data *types.Struct) (*types.Value, error) {
    if path == nil {
        return &types.Value{Kind: &types.Value_StructValue{StructValue: data}}, nil
    }

    var v *types.Value
    key, ok := path.Selector.(*Process_Node_Reference_Path_Key)
    if !ok {
        return nil, fmt.Errorf("first selector in the path must be a key")
    }

    v, ok = data.Fields[key.Key]
    if !ok {
        return nil, fmt.Errorf("key %s not found", key.Key)
    }

    for p := path.Path; p != nil; p = p.Path {
        switch s := p.Selector.(type) {
        case *Process_Node_Reference_Path_Key:
            str, ok := v.GetKind().(*types.Value_StructValue)
            if !ok {
                return nil, fmt.Errorf("can't get key from non-struct value")
            }
            if str.StructValue.GetFields() == nil {
                return nil, fmt.Errorf("can't get key from nil-struct")
            }
            v, ok = str.StructValue.Fields[s.Key]
            if !ok {
                return nil, fmt.Errorf("key %s not found", s.Key)
            }
        case *Process_Node_Reference_Path_Index:
            list, ok := v.GetKind().(*types.Value_ListValue)
            if !ok {
                return nil, fmt.Errorf("can't get index from non-list value")
            }

            if len(list.ListValue.GetValues()) <= int(s.Index) {
                return nil, fmt.Errorf("index %d out of range", s.Index)
            }
            v = list.ListValue.Values[s.Index]
        default:
            return nil, fmt.Errorf("unknown selector type %T", v)
        }
    }

    return v, nil
}