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abad.go
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abad.go
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package abad
import (
"fmt"
"github.com/NeowayLabs/abad/ast"
"github.com/NeowayLabs/abad/builtins"
"github.com/NeowayLabs/abad/internal/utf16"
"github.com/NeowayLabs/abad/parser"
"github.com/NeowayLabs/abad/token"
"github.com/NeowayLabs/abad/types"
)
type (
// Abad interpreter, a very bad one.
Abad struct {
global *types.DataObject
}
)
var (
consoleAttr = utf16.S("console")
)
// NewAbad creates a new ecma script evaluator.
func NewAbad() (*Abad, error) {
a := &Abad{}
return a, a.setup()
}
// Eval the code when no filename is involved (interactive/repl mode).
func (a *Abad) Eval(code string) (types.Value, error) {
return a.EvalFile("<interactive>", code)
}
// EvalFile the code that was obtained from filename.
func (a *Abad) EvalFile(filename string, code string) (types.Value, error) {
program, err := parser.Parse(filename, code)
if err != nil {
return nil, fmt.Errorf("parser error: %s", err)
}
return a.eval(program)
}
func (a *Abad) eval(n ast.Node) (types.Value, error) {
if ast.IsExpr(n) {
return a.evalExpr(n)
}
var ret types.Value
var err error
switch n.Type() {
case ast.NodeProgram:
ret, err = a.evalProgram(n.(*ast.Program))
default:
panic(fmt.Sprintf("AST(%s) not implemented", n))
}
return ret, err
}
func (a *Abad) setup() error {
console, err := builtins.NewConsole()
if err != nil {
return err
}
global := types.NewBaseDataObject()
err = global.Put(consoleAttr, console, true)
if err != nil {
return err
}
a.global = global
return nil
}
func (a *Abad) evalProgram(stmts *ast.Program) (types.Value, error) {
var (
result types.Value
err error
)
for _, node := range stmts.Nodes {
result, err = a.eval(node)
if err != nil {
return nil, err
}
}
return result, nil
}
func (a *Abad) evalUnaryExpr(expr *ast.UnaryExpr) (types.Value, error) {
op := expr.Operator
obj, err := a.eval(expr.Operand)
if err != nil {
return nil, err
}
// TODO(i4k): UnaryExpr could work in any expression in js
// examples below are valid:
// -[]
// +[]
// -{}
// +{}
// -eval("0")
// -new Object()
num, ok := obj.(types.Number)
if !ok {
return nil, fmt.Errorf("not a number: %s", obj)
}
switch op {
case token.Minus:
num = -num
case token.Plus:
num = +num
default:
return nil, fmt.Errorf("unsupported unary operator: %s", op)
}
return num, nil
}
func (a *Abad) evalExpr(n ast.Node) (types.Value, error) {
if !ast.IsExpr(n) {
return nil, fmt.Errorf("internal error: node[%s] is not an expression", n)
}
switch n.Type() {
case ast.NodeUndefined:
return types.Undefined, nil
case ast.NodeNull:
return types.Null, nil
case ast.NodeBool:
val := n.(ast.Bool)
return types.Bool(val.Value()), nil
case ast.NodeNumber:
val := n.(ast.Number)
return types.Number(val.Value()), nil
case ast.NodeString:
val := n.(ast.String)
return types.String(val), nil
case ast.NodeIdent:
val := n.(ast.Ident)
return a.evalIdentExpr(val)
case ast.NodeMemberExpr:
val := n.(*ast.MemberExpr)
return a.evalMemberExpr(val)
case ast.NodeCallExpr:
val := n.(*ast.CallExpr)
return a.evalCallExpr(val)
case ast.NodeUnaryExpr:
expr := n.(*ast.UnaryExpr)
return a.evalUnaryExpr(expr)
default:
return nil, fmt.Errorf("unknown node type: %v", n)
}
}
func (a *Abad) evalIdentExpr(ident ast.Ident) (types.Value, error) {
val, err := a.global.Get(utf16.Str(ident))
if err != nil {
return nil, err
}
if types.StrictEqual(val, types.Undefined) {
return nil, fmt.Errorf("[%s] is not defined",
ident.String())
}
return val, nil
}
func (a *Abad) evalMemberExpr(member *ast.MemberExpr) (types.Value, error) {
objval, err := a.evalExpr(member.Object)
if err != nil {
return nil, err
}
if objval.Kind() != types.KindObject {
panic("wrapping primitive values not implemented yet")
}
obj, err := objval.ToObject()
if err != nil {
return nil, err
}
return obj.Get(utf16.Str(member.Property))
}
func (a *Abad) evalCallExpr(call *ast.CallExpr) (types.Value, error) {
// TODO(i4k): safe to assume the AST is ok?
objval, err := a.evalExpr(call.Callee)
if err != nil {
return nil, err
}
obj, err := objval.ToObject() // wraps primitives (if needed)
if err != nil {
return nil, err
}
fun, ok := obj.(types.Function)
if !ok {
return nil, fmt.Errorf("%s is not a function", objval.Kind())
}
args, err := a.evalArgs(call.Args)
if err != nil {
return nil, err
}
return fun.Call(obj, args), nil
}
func (a *Abad) evalArgs(args []ast.Node) ([]types.Value, error) {
var vargs []types.Value
for _, arg := range args {
v, err := a.evalExpr(arg)
if err != nil {
return nil, err
}
vargs = append(vargs, v)
}
return vargs, nil
}