Begin to implement jsonpath
This commit is contained in:
182
processor/jsonpath/jsonpath.go
Normal file
182
processor/jsonpath/jsonpath.go
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@@ -0,0 +1,182 @@
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package main
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import (
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"fmt"
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"strconv"
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)
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// JSONStep represents a single step in a JSONPath query
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type JSONStep struct {
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Type StepType
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Key string // For Child/RecursiveDescent
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Index int // For Index (use -1 for wildcard "*")
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}
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type StepType int
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const (
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RootStep StepType = iota
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ChildStep
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RecursiveDescentStep
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WildcardStep
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IndexStep
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)
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func ParseJSONPath(path string) ([]JSONStep, error) {
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if len(path) == 0 || path[0] != '$' {
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return nil, fmt.Errorf("path must start with $")
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}
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path = path[1:]
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steps := []JSONStep{}
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i := 0
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for i < len(path) {
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switch path[i] {
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case '.':
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i++
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if i < len(path) && path[i] == '.' {
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// Recursive descent
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i++
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key, nextPos := readKey(path, i)
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steps = append(steps, JSONStep{Type: RecursiveDescentStep, Key: key})
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i = nextPos
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} else {
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// Child step or wildcard
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key, nextPos := readKey(path, i)
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if key == "*" {
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steps = append(steps, JSONStep{Type: WildcardStep})
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} else {
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steps = append(steps, JSONStep{Type: ChildStep, Key: key})
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}
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i = nextPos
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}
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case '[':
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// Index step
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i++
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indexStr, nextPos := readIndex(path, i)
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if indexStr == "*" {
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steps = append(steps, JSONStep{Type: IndexStep, Index: -1})
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} else {
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index, err := strconv.Atoi(indexStr)
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if err != nil {
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return nil, fmt.Errorf("invalid index: %s", indexStr)
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}
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steps = append(steps, JSONStep{Type: IndexStep, Index: index})
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}
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i = nextPos + 1 // Skip closing ]
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default:
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return nil, fmt.Errorf("unexpected character: %c", path[i])
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}
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}
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return steps, nil
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}
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func readKey(path string, start int) (string, int) {
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i := start
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for ; i < len(path); i++ {
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if path[i] == '.' || path[i] == '[' {
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break
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}
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}
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return path[start:i], i
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}
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func readIndex(path string, start int) (string, int) {
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i := start
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for ; i < len(path); i++ {
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if path[i] == ']' {
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break
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}
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}
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return path[start:i], i
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}
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func EvaluateJSONPath(data interface{}, steps []JSONStep) []interface{} {
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current := []interface{}{data}
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for _, step := range steps {
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var next []interface{}
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for _, node := range current {
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next = append(next, evalStep(node, step)...)
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}
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current = next
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}
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return current
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}
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func evalStep(node interface{}, step JSONStep) []interface{} {
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switch step.Type {
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case ChildStep:
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return evalChild(node, step.Key)
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case RecursiveDescentStep:
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return evalRecursiveDescent(node, step.Key)
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case WildcardStep:
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return evalWildcard(node)
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case IndexStep:
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return evalIndex(node, step.Index)
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default:
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return nil
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}
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}
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func evalChild(node interface{}, key string) []interface{} {
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if m, ok := node.(map[string]interface{}); ok {
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if val, exists := m[key]; exists {
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return []interface{}{val}
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}
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}
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return nil
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}
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func evalRecursiveDescent(node interface{}, targetKey string) []interface{} {
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results := []interface{}{}
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queue := []interface{}{node}
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for len(queue) > 0 {
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current := queue[0]
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queue = queue[1:]
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if m, ok := current.(map[string]interface{}); ok {
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// Check if current level has target key
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if val, exists := m[targetKey]; exists {
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results = append(results, val)
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}
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// Add all children to queue
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for _, v := range m {
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queue = append(queue, v)
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}
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} else if arr, ok := current.([]interface{}); ok {
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queue = append(queue, arr...)
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}
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}
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return results
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}
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func evalWildcard(node interface{}) []interface{} {
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if m, ok := node.(map[string]interface{}); ok {
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results := make([]interface{}, 0, len(m))
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for _, v := range m {
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results = append(results, v)
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}
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return results
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}
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return nil
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}
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func evalIndex(node interface{}, index int) []interface{} {
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if arr, ok := node.([]interface{}); ok {
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if index == -1 { // Wildcard [*]
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return arr
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}
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if index >= 0 && index < len(arr) {
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return []interface{}{arr[index]}
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}
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}
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return nil
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}
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209
processor/jsonpath/jsonpath_test.go
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209
processor/jsonpath/jsonpath_test.go
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@@ -0,0 +1,209 @@
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package jsonpath
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import (
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"reflect"
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"testing"
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)
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var testData = map[string]interface{}{
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"store": map[string]interface{}{
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"book": []interface{}{
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map[string]interface{}{
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"title": "The Fellowship of the Ring",
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"price": 22.99,
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},
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map[string]interface{}{
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"title": "The Two Towers",
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"price": 23.45,
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},
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},
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"bicycle": map[string]interface{}{
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"color": "red",
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"price": 199.95,
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},
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},
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}
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func TestParser(t *testing.T) {
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tests := []struct {
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path string
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steps []JSONStep
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wantErr bool
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}{
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{
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path: "$.store.bicycle.color",
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steps: []JSONStep{
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{Type: RootStep},
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{Type: ChildStep, Key: "store"},
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{Type: ChildStep, Key: "bicycle"},
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{Type: ChildStep, Key: "color"},
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},
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},
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{
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path: "$..price",
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steps: []JSONStep{
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{Type: RootStep},
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{Type: RecursiveDescentStep, Key: "price"},
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},
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},
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{
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path: "$.store.book[*].title",
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steps: []JSONStep{
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{Type: RootStep},
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{Type: ChildStep, Key: "store"},
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{Type: ChildStep, Key: "book"},
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{Type: IndexStep, Index: -1}, // Wildcard
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{Type: ChildStep, Key: "title"},
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},
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},
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{
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path: "$.store.book[0]",
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steps: []JSONStep{
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{Type: RootStep},
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{Type: ChildStep, Key: "store"},
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{Type: ChildStep, Key: "book"},
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{Type: IndexStep, Index: 0},
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},
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},
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{
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path: "invalid.path",
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wantErr: true,
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},
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{
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path: "$.store.book[abc]",
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wantErr: true,
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},
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}
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for _, tt := range tests {
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t.Run(tt.path, func(t *testing.T) {
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steps, err := ParseJSONPath(tt.path)
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if (err != nil) != tt.wantErr {
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t.Fatalf("ParseJSONPath() error = %v, wantErr %v", err, tt.wantErr)
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}
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if !tt.wantErr && !reflect.DeepEqual(steps, tt.steps) {
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t.Errorf("ParseJSONPath() steps = %+v, want %+v", steps, tt.steps)
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}
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})
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}
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}
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func TestEvaluator(t *testing.T) {
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tests := []struct {
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name string
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path string
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expected []interface{}
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}{
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{
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name: "simple_property_access",
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path: "$.store.bicycle.color",
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expected: []interface{}{"red"},
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},
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{
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name: "array_index_access",
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path: "$.store.book[0].title",
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expected: []interface{}{"The Fellowship of the Ring"},
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},
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{
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name: "wildcard_array_access",
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path: "$.store.book[*].title",
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expected: []interface{}{
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"The Fellowship of the Ring",
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"The Two Towers",
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},
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},
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{
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name: "recursive_price_search",
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path: "$..price",
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expected: []interface{}{
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22.99,
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23.45,
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199.95,
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},
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},
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{
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name: "wildcard_recursive",
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path: "$..*",
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expected: []interface{}{
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testData["store"], // Root element
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// Store children
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testData["store"].(map[string]interface{})["book"],
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testData["store"].(map[string]interface{})["bicycle"],
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// Books
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testData["store"].(map[string]interface{})["book"].([]interface{})[0],
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testData["store"].(map[string]interface{})["book"].([]interface{})[1],
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// Book contents
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"The Fellowship of the Ring",
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22.99,
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"The Two Towers",
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23.45,
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// Bicycle
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testData["store"].(map[string]interface{})["bicycle"].(map[string]interface{})["color"],
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testData["store"].(map[string]interface{})["bicycle"].(map[string]interface{})["price"],
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"red",
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199.95,
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},
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},
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{
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name: "invalid_index",
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path: "$.store.book[5]",
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expected: []interface{}{},
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},
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{
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name: "nonexistent_property",
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path: "$.store.nonexistent",
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expected: []interface{}{},
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},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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steps, err := ParseJSONPath(tt.path)
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if err != nil {
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t.Fatalf("Parse error: %v", err)
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}
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result := EvaluateJSONPath(testData, steps)
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// Special handling for wildcard recursive test
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if tt.name == "wildcard_recursive" {
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if len(result) != len(tt.expected) {
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t.Errorf("Expected %d items, got %d", len(tt.expected), len(result))
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}
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return
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}
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if !reflect.DeepEqual(result, tt.expected) {
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t.Errorf("EvaluateJSONPath() = %v, want %v", result, tt.expected)
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}
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})
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}
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}
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func TestEdgeCases(t *testing.T) {
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t.Run("empty_data", func(t *testing.T) {
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steps, _ := ParseJSONPath("$.a.b")
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result := EvaluateJSONPath(nil, steps)
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if len(result) > 0 {
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t.Errorf("Expected empty result, got %v", result)
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}
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})
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t.Run("empty_path", func(t *testing.T) {
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_, err := ParseJSONPath("")
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if err == nil {
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t.Error("Expected error for empty path")
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}
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})
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t.Run("numeric_keys", func(t *testing.T) {
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data := map[string]interface{}{
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"42": "answer",
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}
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steps, _ := ParseJSONPath("$.42")
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result := EvaluateJSONPath(data, steps)
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if result[0] != "answer" {
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t.Errorf("Expected 'answer', got %v", result)
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}
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})
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}
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