package jmespath
import (
"errors"
"reflect"
"unicode"
"unicode/utf8"
)
/* This is a tree based interpreter. It walks the AST and directly
interprets the AST to search through a JSON document.
*/
type treeInterpreter struct {
fCall *functionCaller
}
func newInterpreter() *treeInterpreter {
interpreter := treeInterpreter{}
interpreter.fCall = newFunctionCaller()
return &interpreter
}
type expRef struct {
ref ASTNode
}
// Execute takes an ASTNode and input data and interprets the AST directly.
// It will produce the result of applying the JMESPath expression associated
// with the ASTNode to the input data "value".
func (intr *treeInterpreter) Execute(node ASTNode, value interface{}) (interface{}, error) {
switch node.nodeType {
case ASTComparator:
left, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, err
}
right, err := intr.Execute(node.children[1], value)
if err != nil {
return nil, err
}
switch node.value {
case tEQ:
return objsEqual(left, right), nil
case tNE:
return !objsEqual(left, right), nil
}
leftNum, ok := left.(float64)
if !ok {
return nil, nil
}
rightNum, ok := right.(float64)
if !ok {
return nil, nil
}
switch node.value {
case tGT:
return leftNum > rightNum, nil
case tGTE:
return leftNum >= rightNum, nil
case tLT:
return leftNum < rightNum, nil
case tLTE:
return leftNum <= rightNum, nil
}
case ASTExpRef:
return expRef{ref: node.children[0]}, nil
case ASTFunctionExpression:
resolvedArgs := []interface{}{}
for _, arg := range node.children {
current, err := intr.Execute(arg, value)
if err != nil {
return nil, err
}
resolvedArgs = append(resolvedArgs, current)
}
return intr.fCall.CallFunction(node.value.(string), resolvedArgs, intr)
case ASTField:
if m, ok := value.(map[string]interface{}); ok {
key := node.value.(string)
return m[key], nil
}
return intr.fieldFromStruct(node.value.(string), value)
case ASTFilterProjection:
left, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, nil
}
sliceType, ok := left.([]interface{})
if !ok {
if isSliceType(left) {
return intr.filterProjectionWithReflection(node, left)
}
return nil, nil
}
compareNode := node.children[2]
collected := []interface{}{}
for _, element := range sliceType {
result, err := intr.Execute(compareNode, element)
if err != nil {
return nil, err
}
if !isFalse(result) {
current, err := intr.Execute(node.children[1], element)
if err != nil {
return nil, err
}
if current != nil {
collected = append(collected, current)
}
}
}
return collected, nil
case ASTFlatten:
left, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, nil
}
sliceType, ok := left.([]interface{})
if !ok {
// If we can't type convert to []interface{}, there's
// a chance this could still work via reflection if we're
// dealing with user provided types.
if isSliceType(left) {
return intr.flattenWithReflection(left)
}
return nil, nil
}
flattened := []interface{}{}
for _, element := range sliceType {
if elementSlice, ok := element.([]interface{}); ok {
flattened = append(flattened, elementSlice...)
} else if isSliceType(element) {
reflectFlat := []interface{}{}
v := reflect.ValueOf(element)
for i := 0; i < v.Len(); i++ {
reflectFlat = append(reflectFlat, v.Index(i).Interface())
}
flattened = append(flattened, reflectFlat...)
} else {
flattened = append(flattened, element)
}
}
return flattened, nil
case ASTIdentity, ASTCurrentNode:
return value, nil
case ASTIndex:
if sliceType, ok := value.([]interface{}); ok {
index := node.value.(int)
if index < 0 {
index += len(sliceType)
}
if index < len(sliceType) && index >= 0 {
return sliceType[index], nil
}
return nil, nil
}
// Otherwise try via reflection.
rv := reflect.ValueOf(value)
if rv.Kind() == reflect.Slice {
index := node.value.(int)
if index < 0 {
index += rv.Len()
}
if index < rv.Len() && index >= 0 {
v := rv.Index(index)
return v.Interface(), nil
}
}
return nil, nil
case ASTKeyValPair:
return intr.Execute(node.children[0], value)
case ASTLiteral:
return node.value, nil
case ASTMultiSelectHash:
if value == nil {
return nil, nil
}
collected := make(map[string]interface{})
for _, child := range node.children {
current, err := intr.Execute(child, value)
if err != nil {
return nil, err
}
key := child.value.(string)
collected[key] = current
}
return collected, nil
case ASTMultiSelectList:
if value == nil {
return nil, nil
}
collected := []interface{}{}
for _, child := range node.children {
current, err := intr.Execute(child, value)
if err != nil {
return nil, err
}
collected = append(collected, current)
}
return collected, nil
case ASTOrExpression:
matched, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, err
}
if isFalse(matched) {
matched, err = intr.Execute(node.children[1], value)
if err != nil {
return nil, err
}
}
return matched, nil
case ASTAndExpression:
matched, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, err
}
if isFalse(matched) {
return matched, nil
}
return intr.Execute(node.children[1], value)
case ASTNotExpression:
matched, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, err
}
if isFalse(matched) {
return true, nil
}
return false, nil
case ASTPipe:
result := value
var err error
for _, child := range node.children {
result, err = intr.Execute(child, result)
if err != nil {
return nil, err
}
}
return result, nil
case ASTProjection:
left, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, err
}
sliceType, ok := left.([]interface{})
if !ok {
if isSliceType(left) {
return intr.projectWithReflection(node, left)
}
return nil, nil
}
collected := []interface{}{}
var current interface{}
for _, element := range sliceType {
current, err = intr.Execute(node.children[1], element)
if err != nil {
return nil, err
}
if current != nil {
collected = append(collected, current)
}
}
return collected, nil
case ASTSubexpression, ASTIndexExpression:
left, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, err
}
return intr.Execute(node.children[1], left)
case ASTSlice:
sliceType, ok := value.([]interface{})
if !ok {
if isSliceType(value) {
return intr.sliceWithReflection(node, value)
}
return nil, nil
}
parts := node.value.([]*int)
sliceParams := make([]sliceParam, 3)
for i, part := range parts {
if part != nil {
sliceParams[i].Specified = true
sliceParams[i].N = *part
}
}
return slice(sliceType, sliceParams)
case ASTValueProjection:
left, err := intr.Execute(node.children[0], value)
if err != nil {
return nil, nil
}
mapType, ok := left.(map[string]interface{})
if !ok {
return nil, nil
}
values := make([]interface{}, len(mapType))
for _, value := range mapType {
values = append(values, value)
}
collected := []interface{}{}
for _, element := range values {
current, err := intr.Execute(node.children[1], element)
if err != nil {
return nil, err
}
if current != nil {
collected = append(collected, current)
}
}
return collected, nil
}
return nil, errors.New("Unknown AST node: " + node.nodeType.String())
}
func (intr *treeInterpreter) fieldFromStruct(key string, value interface{}) (interface{}, error) {
rv := reflect.ValueOf(value)
first, n := utf8.DecodeRuneInString(key)
fieldName := string(unicode.ToUpper(first)) + key[n:]
if rv.Kind() == reflect.Struct {
v := rv.FieldByName(fieldName)
if !v.IsValid() {
return nil, nil
}
return v.Interface(), nil
} else if rv.Kind() == reflect.Ptr {
// Handle multiple levels of indirection?
if rv.IsNil() {
return nil, nil
}
rv = rv.Elem()
v := rv.FieldByName(fieldName)
if !v.IsValid() {
return nil, nil
}
return v.Interface(), nil
}
return nil, nil
}
func (intr *treeInterpreter) flattenWithReflection(value interface{}) (interface{}, error) {
v := reflect.ValueOf(value)
flattened := []interface{}{}
for i := 0; i < v.Len(); i++ {
element := v.Index(i).Interface()
if reflect.TypeOf(element).Kind() == reflect.Slice {
// Then insert the contents of the element
// slice into the flattened slice,
// i.e flattened = append(flattened, mySlice...)
elementV := reflect.ValueOf(element)
for j := 0; j < elementV.Len(); j++ {
flattened = append(
flattened, elementV.Index(j).Interface())
}
} else {
flattened = append(flattened, element)
}
}
return flattened, nil
}
func (intr *treeInterpreter) sliceWithReflection(node ASTNode, value interface{}) (interface{}, error) {
v := reflect.ValueOf(value)
parts := node.value.([]*int)
sliceParams := make([]sliceParam, 3)
for i, part := range parts {
if part != nil {
sliceParams[i].Specified = true
sliceParams[i].N = *part
}
}
final := []interface{}{}
for i := 0; i < v.Len(); i++ {
element := v.Index(i).Interface()
final = append(final, element)
}
return slice(final, sliceParams)
}
func (intr *treeInterpreter) filterProjectionWithReflection(node ASTNode, value interface{}) (interface{}, error) {
compareNode := node.children[2]
collected := []interface{}{}
v := reflect.ValueOf(value)
for i := 0; i < v.Len(); i++ {
element := v.Index(i).Interface()
result, err := intr.Execute(compareNode, element)
if err != nil {
return nil, err
}
if !isFalse(result) {
current, err := intr.Execute(node.children[1], element)
if err != nil {
return nil, err
}
if current != nil {
collected = append(collected, current)
}
}
}
return collected, nil
}
func (intr *treeInterpreter) projectWithReflection(node ASTNode, value interface{}) (interface{}, error) {
collected := []interface{}{}
v := reflect.ValueOf(value)
for i := 0; i < v.Len(); i++ {
element := v.Index(i).Interface()
result, err := intr.Execute(node.children[1], element)
if err != nil {
return nil, err
}
if result != nil {
collected = append(collected, result)
}
}
return collected, nil
}
