jsonpath.go

/*
Copyright 2015 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package jsonpath

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"reflect"
	"strings"

	"k8s.io/client-go/third_party/forked/golang/template"
)

type JSONPath struct {
	name       string
	parser     *Parser
	beginRange int
	inRange    int
	endRange   int

	lastEndNode *Node

	allowMissingKeys bool
	outputJSON       bool
}

// New creates a new JSONPath with the given name.
func New(name string) *JSONPath {
	return &JSONPath{
		name:       name,
		beginRange: 0,
		inRange:    0,
		endRange:   0,
	}
}

// AllowMissingKeys allows a caller to specify whether they want an error if a field or map key
// cannot be located, or simply an empty result. The receiver is returned for chaining.
func (j *JSONPath) AllowMissingKeys(allow bool) *JSONPath {
	j.allowMissingKeys = allow
	return j
}

// Parse parses the given template and returns an error.
func (j *JSONPath) Parse(text string) error {
	var err error
	j.parser, err = Parse(j.name, text)
	return err
}

// Execute bounds data into template and writes the result.
func (j *JSONPath) Execute(wr io.Writer, data interface{}) error {
	fullResults, err := j.FindResults(data)
	if err != nil {
		return err
	}
	for ix := range fullResults {
		if err := j.PrintResults(wr, fullResults[ix]); err != nil {
			return err
		}
	}
	return nil
}

func (j *JSONPath) FindResults(data interface{}) ([][]reflect.Value, error) {
	if j.parser == nil {
		return nil, fmt.Errorf("%s is an incomplete jsonpath template", j.name)
	}

	cur := []reflect.Value{reflect.ValueOf(data)}
	nodes := j.parser.Root.Nodes
	fullResult := [][]reflect.Value{}
	for i := 0; i < len(nodes); i++ {
		node := nodes[i]
		results, err := j.walk(cur, node)
		if err != nil {
			return nil, err
		}

		// encounter an end node, break the current block
		if j.endRange > 0 && j.endRange <= j.inRange {
			j.endRange--
			j.lastEndNode = &nodes[i]
			break
		}
		// encounter a range node, start a range loop
		if j.beginRange > 0 {
			j.beginRange--
			j.inRange++
			if len(results) > 0 {
				for _, value := range results {
					j.parser.Root.Nodes = nodes[i+1:]
					nextResults, err := j.FindResults(value.Interface())
					if err != nil {
						return nil, err
					}
					fullResult = append(fullResult, nextResults...)
				}
			} else {
				// If the range has no results, we still need to process the nodes within the range
				// so the position will advance to the end node
				j.parser.Root.Nodes = nodes[i+1:]
				_, err := j.FindResults(nil)
				if err != nil {
					return nil, err
				}
			}
			j.inRange--

			// Fast forward to resume processing after the most recent end node that was encountered
			for k := i + 1; k < len(nodes); k++ {
				if &nodes[k] == j.lastEndNode {
					i = k
					break
				}
			}
			continue
		}
		fullResult = append(fullResult, results)
	}
	return fullResult, nil
}

// EnableJSONOutput changes the PrintResults behavior to return a JSON array of results
func (j *JSONPath) EnableJSONOutput(v bool) {
	j.outputJSON = v
}

// PrintResults writes the results into writer
func (j *JSONPath) PrintResults(wr io.Writer, results []reflect.Value) error {
	if j.outputJSON {
		// convert the []reflect.Value to something that json
		// will be able to marshal
		r := make([]interface{}, 0, len(results))
		for i := range results {
			r = append(r, results[i].Interface())
		}
		results = []reflect.Value{reflect.ValueOf(r)}
	}
	for i, r := range results {
		var text []byte
		var err error
		outputJSON := true
		kind := r.Kind()
		if kind == reflect.Interface {
			kind = r.Elem().Kind()
		}
		switch kind {
		case reflect.Map:
		case reflect.Array:
		case reflect.Slice:
		case reflect.Struct:
		default:
			outputJSON = false
		}
		switch {
		case outputJSON || j.outputJSON:
			if j.outputJSON {
				text, err = json.MarshalIndent(r.Interface(), "", "    ")
				text = append(text, '\n')
			} else {
				text, err = json.Marshal(r.Interface())
			}
		default:
			text, err = j.evalToText(r)
		}
		if err != nil {
			return err
		}
		if i != len(results)-1 {
			text = append(text, ' ')
		}
		if _, err = wr.Write(text); err != nil {
			return err
		}
	}

	return nil

}

// walk visits tree rooted at the given node in DFS order
func (j *JSONPath) walk(value []reflect.Value, node Node) ([]reflect.Value, error) {
	switch node := node.(type) {
	case *ListNode:
		return j.evalList(value, node)
	case *TextNode:
		return []reflect.Value{reflect.ValueOf(node.Text)}, nil
	case *FieldNode:
		return j.evalField(value, node)
	case *ArrayNode:
		return j.evalArray(value, node)
	case *FilterNode:
		return j.evalFilter(value, node)
	case *IntNode:
		return j.evalInt(value, node)
	case *BoolNode:
		return j.evalBool(value, node)
	case *FloatNode:
		return j.evalFloat(value, node)
	case *WildcardNode:
		return j.evalWildcard(value, node)
	case *RecursiveNode:
		return j.evalRecursive(value, node)
	case *UnionNode:
		return j.evalUnion(value, node)
	case *IdentifierNode:
		return j.evalIdentifier(value, node)
	default:
		return value, fmt.Errorf("unexpected Node %v", node)
	}
}

// evalInt evaluates IntNode
func (j *JSONPath) evalInt(input []reflect.Value, node *IntNode) ([]reflect.Value, error) {
	result := make([]reflect.Value, len(input))
	for i := range input {
		result[i] = reflect.ValueOf(node.Value)
	}
	return result, nil
}

// evalFloat evaluates FloatNode
func (j *JSONPath) evalFloat(input []reflect.Value, node *FloatNode) ([]reflect.Value, error) {
	result := make([]reflect.Value, len(input))
	for i := range input {
		result[i] = reflect.ValueOf(node.Value)
	}
	return result, nil
}

// evalBool evaluates BoolNode
func (j *JSONPath) evalBool(input []reflect.Value, node *BoolNode) ([]reflect.Value, error) {
	result := make([]reflect.Value, len(input))
	for i := range input {
		result[i] = reflect.ValueOf(node.Value)
	}
	return result, nil
}

// evalList evaluates ListNode
func (j *JSONPath) evalList(value []reflect.Value, node *ListNode) ([]reflect.Value, error) {
	var err error
	curValue := value
	for _, node := range node.Nodes {
		curValue, err = j.walk(curValue, node)
		if err != nil {
			return curValue, err
		}
	}
	return curValue, nil
}

// evalIdentifier evaluates IdentifierNode
func (j *JSONPath) evalIdentifier(input []reflect.Value, node *IdentifierNode) ([]reflect.Value, error) {
	results := []reflect.Value{}
	switch node.Name {
	case "range":
		j.beginRange++
		results = input
	case "end":
		if j.inRange > 0 {
			j.endRange++
		} else {
			return results, fmt.Errorf("not in range, nothing to end")
		}
	default:
		return input, fmt.Errorf("unrecognized identifier %v", node.Name)
	}
	return results, nil
}

// evalArray evaluates ArrayNode
func (j *JSONPath) evalArray(input []reflect.Value, node *ArrayNode) ([]reflect.Value, error) {
	result := []reflect.Value{}
	for _, value := range input {

		value, isNil := template.Indirect(value)
		if isNil {
			continue
		}
		if value.Kind() != reflect.Array && value.Kind() != reflect.Slice {
			return input, fmt.Errorf("%v is not array or slice", value.Type())
		}
		params := node.Params
		if !params[0].Known {
			params[0].Value = 0
		}
		if params[0].Value < 0 {
			params[0].Value += value.Len()
		}
		if !params[1].Known {
			params[1].Value = value.Len()
		}

		if params[1].Value < 0 || (params[1].Value == 0 && params[1].Derived) {
			params[1].Value += value.Len()
		}
		sliceLength := value.Len()
		if params[1].Value != params[0].Value { // if you're requesting zero elements, allow it through.
			if params[0].Value >= sliceLength || params[0].Value < 0 {
				return input, fmt.Errorf("array index out of bounds: index %d, length %d", params[0].Value, sliceLength)
			}
			if params[1].Value > sliceLength || params[1].Value < 0 {
				return input, fmt.Errorf("array index out of bounds: index %d, length %d", params[1].Value-1, sliceLength)
			}
			if params[0].Value > params[1].Value {
				return input, fmt.Errorf("starting index %d is greater than ending index %d", params[0].Value, params[1].Value)
			}
		} else {
			return result, nil
		}

		value = value.Slice(params[0].Value, params[1].Value)

		step := 1
		if params[2].Known {
			if params[2].Value <= 0 {
				return input, fmt.Errorf("step must be > 0")
			}
			step = params[2].Value
		}
		for i := 0; i < value.Len(); i += step {
			result = append(result, value.Index(i))
		}
	}
	return result, nil
}

// evalUnion evaluates UnionNode
func (j *JSONPath) evalUnion(input []reflect.Value, node *UnionNode) ([]reflect.Value, error) {
	result := []reflect.Value{}
	for _, listNode := range node.Nodes {
		temp, err := j.evalList(input, listNode)
		if err != nil {
			return input, err
		}
		result = append(result, temp...)
	}
	return result, nil
}

func (j *JSONPath) findFieldInValue(value *reflect.Value, node *FieldNode) (reflect.Value, error) {
	t := value.Type()
	var inlineValue *reflect.Value
	for ix := 0; ix < t.NumField(); ix++ {
		f := t.Field(ix)
		jsonTag := f.Tag.Get("json")
		parts := strings.Split(jsonTag, ",")
		if len(parts) == 0 {
			continue
		}
		if parts[0] == node.Value {
			return value.Field(ix), nil
		}
		if len(parts[0]) == 0 {
			val := value.Field(ix)
			inlineValue = &val
		}
	}
	if inlineValue != nil {
		if inlineValue.Kind() == reflect.Struct {
			// handle 'inline'
			match, err := j.findFieldInValue(inlineValue, node)
			if err != nil {
				return reflect.Value{}, err
			}
			if match.IsValid() {
				return match, nil
			}
		}
	}
	return value.FieldByName(node.Value), nil
}

// evalField evaluates field of struct or key of map.
func (j *JSONPath) evalField(input []reflect.Value, node *FieldNode) ([]reflect.Value, error) {
	results := []reflect.Value{}
	// If there's no input, there's no output
	if len(input) == 0 {
		return results, nil
	}
	for _, value := range input {
		var result reflect.Value
		value, isNil := template.Indirect(value)
		if isNil {
			continue
		}

		if value.Kind() == reflect.Struct {
			var err error
			if result, err = j.findFieldInValue(&value, node); err != nil {
				return nil, err
			}
		} else if value.Kind() == reflect.Map {
			mapKeyType := value.Type().Key()
			nodeValue := reflect.ValueOf(node.Value)
			// node value type must be convertible to map key type
			if !nodeValue.Type().ConvertibleTo(mapKeyType) {
				return results, fmt.Errorf("%s is not convertible to %s", nodeValue, mapKeyType)
			}
			result = value.MapIndex(nodeValue.Convert(mapKeyType))
		}
		if result.IsValid() {
			results = append(results, result)
		}
	}
	if len(results) == 0 {
		if j.allowMissingKeys {
			return results, nil
		}
		return results, fmt.Errorf("%s is not found", node.Value)
	}
	return results, nil
}

// evalWildcard extracts all contents of the given value
func (j *JSONPath) evalWildcard(input []reflect.Value, node *WildcardNode) ([]reflect.Value, error) {
	results := []reflect.Value{}
	for _, value := range input {
		value, isNil := template.Indirect(value)
		if isNil {
			continue
		}

		kind := value.Kind()
		if kind == reflect.Struct {
			for i := 0; i < value.NumField(); i++ {
				results = append(results, value.Field(i))
			}
		} else if kind == reflect.Map {
			for _, key := range value.MapKeys() {
				results = append(results, value.MapIndex(key))
			}
		} else if kind == reflect.Array || kind == reflect.Slice || kind == reflect.String {
			for i := 0; i < value.Len(); i++ {
				results = append(results, value.Index(i))
			}
		}
	}
	return results, nil
}

// evalRecursive visits the given value recursively and pushes all of them to result
func (j *JSONPath) evalRecursive(input []reflect.Value, node *RecursiveNode) ([]reflect.Value, error) {
	result := []reflect.Value{}
	for _, value := range input {
		results := []reflect.Value{}
		value, isNil := template.Indirect(value)
		if isNil {
			continue
		}

		kind := value.Kind()
		if kind == reflect.Struct {
			for i := 0; i < value.NumField(); i++ {
				results = append(results, value.Field(i))
			}
		} else if kind == reflect.Map {
			for _, key := range value.MapKeys() {
				results = append(results, value.MapIndex(key))
			}
		} else if kind == reflect.Array || kind == reflect.Slice || kind == reflect.String {
			for i := 0; i < value.Len(); i++ {
				results = append(results, value.Index(i))
			}
		}
		if len(results) != 0 {
			result = append(result, value)
			output, err := j.evalRecursive(results, node)
			if err != nil {
				return result, err
			}
			result = append(result, output...)
		}
	}
	return result, nil
}

// evalFilter filters array according to FilterNode
func (j *JSONPath) evalFilter(input []reflect.Value, node *FilterNode) ([]reflect.Value, error) {
	results := []reflect.Value{}
	for _, value := range input {
		value, _ = template.Indirect(value)

		if value.Kind() != reflect.Array && value.Kind() != reflect.Slice {
			return input, fmt.Errorf("%v is not array or slice and cannot be filtered", value)
		}
		for i := 0; i < value.Len(); i++ {
			temp := []reflect.Value{value.Index(i)}
			lefts, err := j.evalList(temp, node.Left)

			//case exists
			if node.Operator == "exists" {
				if len(lefts) > 0 {
					results = append(results, value.Index(i))
				}
				continue
			}

			if err != nil {
				return input, err
			}

			var left, right interface{}
			switch {
			case len(lefts) == 0:
				continue
			case len(lefts) > 1:
				return input, fmt.Errorf("can only compare one element at a time")
			}
			left = lefts[0].Interface()

			rights, err := j.evalList(temp, node.Right)
			if err != nil {
				return input, err
			}
			switch {
			case len(rights) == 0:
				continue
			case len(rights) > 1:
				return input, fmt.Errorf("can only compare one element at a time")
			}
			right = rights[0].Interface()

			pass := false
			switch node.Operator {
			case "<":
				pass, err = template.Less(left, right)
			case ">":
				pass, err = template.Greater(left, right)
			case "==":
				pass, err = template.Equal(left, right)
			case "!=":
				pass, err = template.NotEqual(left, right)
			case "<=":
				pass, err = template.LessEqual(left, right)
			case ">=":
				pass, err = template.GreaterEqual(left, right)
			default:
				return results, fmt.Errorf("unrecognized filter operator %s", node.Operator)
			}
			if err != nil {
				return results, err
			}
			if pass {
				results = append(results, value.Index(i))
			}
		}
	}
	return results, nil
}

// evalToText translates reflect value to corresponding text
func (j *JSONPath) evalToText(v reflect.Value) ([]byte, error) {
	iface, ok := template.PrintableValue(v)
	if !ok {
		return nil, fmt.Errorf("can't print type %s", v.Type())
	}
	if iface == nil {
		return []byte("null"), nil
	}
	var buffer bytes.Buffer
	fmt.Fprint(&buffer, iface)
	return buffer.Bytes(), nil
}