445 lines
9.1 KiB
Go
445 lines
9.1 KiB
Go
package jsonpath
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import (
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"encoding/json"
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"sort"
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"strconv"
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"strings"
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)
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type (
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// pathTokenType represents single JSONPath token.
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pathTokenType byte
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// pathParser combines JSONPath and a position to start parsing from.
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pathParser struct {
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s string
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i int
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depth int
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}
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)
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const (
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pathInvalid pathTokenType = iota
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pathRoot
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pathDot
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pathLeftBracket
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pathRightBracket
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pathAsterisk
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pathComma
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pathColon
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pathIdentifier
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pathString
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pathNumber
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)
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const maxNestingDepth = 6
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// Get returns substructures of value selected by path.
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// The result is always non-nil unless path is invalid.
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func Get(path string, value interface{}) ([]interface{}, bool) {
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p := pathParser{
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depth: maxNestingDepth,
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s: path,
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}
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typ, _ := p.nextToken()
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if typ != pathRoot {
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return nil, false
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}
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objs := []interface{}{value}
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for p.i < len(p.s) {
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var ok bool
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switch typ, _ := p.nextToken(); typ {
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case pathDot:
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objs, ok = p.processDot(objs)
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case pathLeftBracket:
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objs, ok = p.processLeftBracket(objs)
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}
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if !ok {
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return nil, false
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}
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}
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if objs == nil {
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objs = []interface{}{}
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}
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return objs, true
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}
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func (p *pathParser) nextToken() (pathTokenType, string) {
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var (
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typ pathTokenType
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value string
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ok = true
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numRead = 1
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)
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if p.i >= len(p.s) {
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return pathInvalid, ""
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}
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switch c := p.s[p.i]; c {
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case '$':
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typ = pathRoot
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case '.':
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typ = pathDot
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case '[':
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typ = pathLeftBracket
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case ']':
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typ = pathRightBracket
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case '*':
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typ = pathAsterisk
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case ',':
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typ = pathComma
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case ':':
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typ = pathColon
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case '\'':
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typ = pathString
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value, numRead, ok = p.parseString()
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default:
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switch {
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case c == '_' || ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'):
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typ = pathIdentifier
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value, numRead, ok = p.parseIdent()
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case c == '-' || ('0' <= c && c <= '9'):
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typ = pathNumber
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value, numRead, ok = p.parseNumber()
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default:
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return pathInvalid, ""
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}
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}
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if !ok {
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return pathInvalid, ""
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}
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p.i += numRead
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return typ, value
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}
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// parseString parses JSON string surrounded by single quotes.
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// It returns number of characters were consumed and true on success.
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func (p *pathParser) parseString() (string, int, bool) {
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var end int
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for end = p.i + 1; end < len(p.s); end++ {
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if p.s[end] == '\'' {
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return p.s[p.i : end+1], end + 1 - p.i, true
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}
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}
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return "", 0, false
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}
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// parseIdent parses alphanumeric identifier.
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// It returns number of characters were consumed and true on success.
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func (p *pathParser) parseIdent() (string, int, bool) {
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var end int
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for end = p.i + 1; end < len(p.s); end++ {
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c := p.s[end]
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if c != '_' && !('a' <= c && c <= 'z') &&
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!('A' <= c && c <= 'Z') && !('0' <= c && c <= '9') {
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break
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}
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}
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return p.s[p.i:end], end - p.i, true
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}
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// parseNumber parses integer number.
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// Only string representation is returned, size-checking is done on the first use.
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// It also returns number of characters were consumed and true on success.
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func (p *pathParser) parseNumber() (string, int, bool) {
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var end int
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for end = p.i + 1; end < len(p.s); end++ {
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c := p.s[end]
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if c < '0' || '9' < c {
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break
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}
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}
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return p.s[p.i:end], end - p.i, true
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}
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// processDot handles `.` operator.
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// It either descends 1 level down or performs recursive descent.
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func (p *pathParser) processDot(objs []interface{}) ([]interface{}, bool) {
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typ, value := p.nextToken()
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switch typ {
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case pathAsterisk:
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return p.descend(objs)
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case pathDot:
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return p.descendRecursive(objs)
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case pathIdentifier:
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return p.descendByIdent(objs, value)
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default:
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return nil, false
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}
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}
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// descend descends 1 level down.
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// It flattens arrays and returns map values for maps.
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func (p *pathParser) descend(objs []interface{}) ([]interface{}, bool) {
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if p.depth <= 0 {
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return nil, false
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}
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p.depth--
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var values []interface{}
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for i := range objs {
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switch obj := objs[i].(type) {
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case []interface{}:
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values = append(values, obj...)
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case map[string]interface{}:
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keys := make([]string, 0, len(obj))
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for k := range obj {
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keys = append(keys, k)
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}
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sort.Strings(keys)
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for _, k := range keys {
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values = append(values, obj[k])
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}
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}
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}
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return values, true
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}
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// descendRecursive performs recursive descent.
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func (p *pathParser) descendRecursive(objs []interface{}) ([]interface{}, bool) {
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typ, val := p.nextToken()
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if typ != pathIdentifier {
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return nil, false
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}
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var values []interface{}
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for len(objs) > 0 {
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newObjs, _ := p.descendByIdentAux(objs, false, val)
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values = append(values, newObjs...)
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objs, _ = p.descend(objs)
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}
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return values, true
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}
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// descendByIdent performs map's field access by name.
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func (p *pathParser) descendByIdent(objs []interface{}, names ...string) ([]interface{}, bool) {
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return p.descendByIdentAux(objs, true, names...)
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}
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func (p *pathParser) descendByIdentAux(objs []interface{}, checkDepth bool, names ...string) ([]interface{}, bool) {
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if checkDepth {
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if p.depth <= 0 {
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return nil, false
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}
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p.depth--
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}
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var values []interface{}
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for i := range objs {
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obj, ok := objs[i].(map[string]interface{})
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if !ok {
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continue
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}
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for j := range names {
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if v, ok := obj[names[j]]; ok {
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values = append(values, v)
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}
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}
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}
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return values, true
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}
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// descendByIndex performs array access by index.
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func (p *pathParser) descendByIndex(objs []interface{}, indices ...int) ([]interface{}, bool) {
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if p.depth <= 0 {
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return nil, false
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}
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p.depth--
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var values []interface{}
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for i := range objs {
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obj, ok := objs[i].([]interface{})
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if !ok {
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continue
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}
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for _, j := range indices {
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if j < 0 {
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j += len(obj)
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}
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if 0 <= j && j < len(obj) {
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values = append(values, obj[j])
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}
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}
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}
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return values, true
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}
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// processLeftBracket processes index expressions which can be either
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// array/map access, array sub-slice or union of indices.
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func (p *pathParser) processLeftBracket(objs []interface{}) ([]interface{}, bool) {
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typ, value := p.nextToken()
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switch typ {
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case pathAsterisk:
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typ, _ := p.nextToken()
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if typ != pathRightBracket {
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return nil, false
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}
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return p.descend(objs)
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case pathColon:
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return p.processSlice(objs, 0)
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case pathNumber:
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subTyp, _ := p.nextToken()
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switch subTyp {
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case pathColon:
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index, err := strconv.ParseInt(value, 10, 32)
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if err != nil {
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return nil, false
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}
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return p.processSlice(objs, int(index))
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case pathComma:
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return p.processUnion(objs, pathNumber, value)
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case pathRightBracket:
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index, err := strconv.ParseInt(value, 10, 32)
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if err != nil {
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return nil, false
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}
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return p.descendByIndex(objs, int(index))
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default:
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return nil, false
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}
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case pathString:
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subTyp, _ := p.nextToken()
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switch subTyp {
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case pathComma:
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return p.processUnion(objs, pathString, value)
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case pathRightBracket:
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s := strings.Trim(value, "'")
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err := json.Unmarshal([]byte(`"`+s+`"`), &s)
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if err != nil {
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return nil, false
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}
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return p.descendByIdent(objs, s)
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default:
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return nil, false
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}
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default:
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return nil, false
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}
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}
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// processUnion processes union of multiple indices.
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// firstTyp is assumed to be either pathNumber or pathString.
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func (p *pathParser) processUnion(objs []interface{}, firstTyp pathTokenType, firstVal string) ([]interface{}, bool) {
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items := []string{firstVal}
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for {
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typ, val := p.nextToken()
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if typ != firstTyp {
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return nil, false
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}
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items = append(items, val)
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typ, val = p.nextToken()
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if typ == pathRightBracket {
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break
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} else if typ != pathComma {
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return nil, false
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}
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}
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switch firstTyp {
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case pathNumber:
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values := make([]int, len(items))
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for i := range items {
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index, err := strconv.ParseInt(items[i], 10, 32)
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if err != nil {
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return nil, false
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}
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values[i] = int(index)
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}
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return p.descendByIndex(objs, values...)
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case pathString:
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for i := range items {
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s := strings.Trim(items[i], "'")
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err := json.Unmarshal([]byte(`"`+s+`"`), &items[i])
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if err != nil {
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return nil, false
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}
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}
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return p.descendByIdent(objs, items...)
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default:
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panic("token in union must be either number or string")
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}
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}
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// processSlice processes slice with the specified start index.
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func (p *pathParser) processSlice(objs []interface{}, start int) ([]interface{}, bool) {
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typ, val := p.nextToken()
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switch typ {
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case pathNumber:
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typ, _ := p.nextToken()
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if typ != pathRightBracket {
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return nil, false
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}
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index, err := strconv.ParseInt(val, 10, 32)
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if err != nil {
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return nil, false
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}
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return p.descendByRange(objs, start, int(index))
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case pathRightBracket:
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return p.descendByRange(objs, start, 0)
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default:
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return nil, false
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}
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}
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// descendByRange is similar to descend but skips maps and returns sub-slices for arrays.
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func (p *pathParser) descendByRange(objs []interface{}, start, end int) ([]interface{}, bool) {
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if p.depth <= 0 {
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return nil, false
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}
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p.depth--
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var values []interface{}
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for i := range objs {
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arr, ok := objs[i].([]interface{})
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if !ok {
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continue
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}
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subStart := start
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if subStart < 0 {
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subStart += len(arr)
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}
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subEnd := end
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if subEnd <= 0 {
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subEnd += len(arr)
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}
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if subEnd > len(arr) {
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subEnd = len(arr)
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}
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if subEnd <= subStart {
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continue
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}
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values = append(values, arr[subStart:subEnd]...)
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}
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return values, true
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}
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