360 lines
9.5 KiB
Go
360 lines
9.5 KiB
Go
package xpath
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import (
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"errors"
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"fmt"
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)
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type flag int
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const (
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noneFlag flag = iota
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filterFlag
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)
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// builder provides building an XPath expressions.
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type builder struct {
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depth int
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flag flag
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firstInput query
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}
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// axisPredicate creates a predicate to predicating for this axis node.
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func axisPredicate(root *axisNode) func(NodeNavigator) bool {
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// get current axix node type.
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typ := ElementNode
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if root.AxeType == "attribute" {
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typ = AttributeNode
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} else {
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switch root.Prop {
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case "comment":
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typ = CommentNode
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case "text":
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typ = TextNode
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// case "processing-instruction":
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// typ = ProcessingInstructionNode
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case "node":
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typ = ElementNode
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}
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}
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predicate := func(n NodeNavigator) bool {
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if typ == n.NodeType() || typ == TextNode {
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if root.LocalName == "" || (root.LocalName == n.LocalName() && root.Prefix == n.Prefix()) {
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return true
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}
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}
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return false
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}
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return predicate
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}
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// processAxisNode processes a query for the XPath axis node.
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func (b *builder) processAxisNode(root *axisNode) (query, error) {
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var (
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err error
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qyInput query
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qyOutput query
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predicate = axisPredicate(root)
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)
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if root.Input == nil {
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qyInput = &contextQuery{}
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} else {
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if b.flag&filterFlag == 0 {
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if root.AxeType == "child" && (root.Input.Type() == nodeAxis) {
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if input := root.Input.(*axisNode); input.AxeType == "descendant-or-self" {
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var qyGrandInput query
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if input.Input != nil {
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qyGrandInput, _ = b.processNode(input.Input)
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} else {
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qyGrandInput = &contextQuery{}
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}
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qyOutput = &descendantQuery{Input: qyGrandInput, Predicate: predicate, Self: true}
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return qyOutput, nil
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}
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}
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}
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qyInput, err = b.processNode(root.Input)
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if err != nil {
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return nil, err
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}
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}
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switch root.AxeType {
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case "ancestor":
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qyOutput = &ancestorQuery{Input: qyInput, Predicate: predicate}
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case "ancestor-or-self":
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qyOutput = &ancestorQuery{Input: qyInput, Predicate: predicate, Self: true}
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case "attribute":
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qyOutput = &attributeQuery{Input: qyInput, Predicate: predicate}
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case "child":
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filter := func(n NodeNavigator) bool {
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v := predicate(n)
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switch root.Prop {
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case "text":
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v = v && n.NodeType() == TextNode
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case "node":
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v = v && (n.NodeType() == ElementNode || n.NodeType() == TextNode)
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case "comment":
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v = v && n.NodeType() == CommentNode
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}
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return v
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}
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qyOutput = &childQuery{Input: qyInput, Predicate: filter}
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case "descendant":
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qyOutput = &descendantQuery{Input: qyInput, Predicate: predicate}
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case "descendant-or-self":
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qyOutput = &descendantQuery{Input: qyInput, Predicate: predicate, Self: true}
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case "following":
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qyOutput = &followingQuery{Input: qyInput, Predicate: predicate}
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case "following-sibling":
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qyOutput = &followingQuery{Input: qyInput, Predicate: predicate, Sibling: true}
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case "parent":
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qyOutput = &parentQuery{Input: qyInput, Predicate: predicate}
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case "preceding":
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qyOutput = &precedingQuery{Input: qyInput, Predicate: predicate}
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case "preceding-sibling":
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qyOutput = &precedingQuery{Input: qyInput, Predicate: predicate, Sibling: true}
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case "self":
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qyOutput = &selfQuery{Input: qyInput, Predicate: predicate}
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case "namespace":
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// haha,what will you do someting??
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default:
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err = fmt.Errorf("unknown axe type: %s", root.AxeType)
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return nil, err
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}
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return qyOutput, nil
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}
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// processFilterNode builds query for the XPath filter predicate.
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func (b *builder) processFilterNode(root *filterNode) (query, error) {
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b.flag |= filterFlag
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qyInput, err := b.processNode(root.Input)
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if err != nil {
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return nil, err
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}
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qyCond, err := b.processNode(root.Condition)
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if err != nil {
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return nil, err
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}
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qyOutput := &filterQuery{Input: qyInput, Predicate: qyCond}
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return qyOutput, nil
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}
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// processFunctionNode processes query for the XPath function node.
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func (b *builder) processFunctionNode(root *functionNode) (query, error) {
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var qyOutput query
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switch root.FuncName {
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case "starts-with":
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arg1, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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arg2, err := b.processNode(root.Args[1])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: b.firstInput, Func: startwithFunc(arg1, arg2)}
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case "contains":
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arg1, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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arg2, err := b.processNode(root.Args[1])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: b.firstInput, Func: containsFunc(arg1, arg2)}
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case "substring":
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//substring( string , start [, length] )
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if len(root.Args) < 2 {
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return nil, errors.New("xpath: substring function must have at least two parameter")
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}
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var (
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arg1, arg2, arg3 query
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err error
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)
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if arg1, err = b.processNode(root.Args[0]); err != nil {
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return nil, err
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}
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if arg2, err = b.processNode(root.Args[1]); err != nil {
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return nil, err
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}
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if len(root.Args) == 3 {
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if arg3, err = b.processNode(root.Args[2]); err != nil {
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return nil, err
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}
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}
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qyOutput = &functionQuery{Input: b.firstInput, Func: substringFunc(arg1, arg2, arg3)}
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case "string-length":
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// string-length( [string] )
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if len(root.Args) < 1 {
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return nil, errors.New("xpath: string-length function must have at least one parameter")
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}
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arg1, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: b.firstInput, Func: stringLengthFunc(arg1)}
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case "normalize-space":
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if len(root.Args) == 0 {
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return nil, errors.New("xpath: normalize-space function must have at least one parameter")
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}
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argQuery, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: argQuery, Func: normalizespaceFunc}
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case "not":
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if len(root.Args) == 0 {
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return nil, errors.New("xpath: not function must have at least one parameter")
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}
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argQuery, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: argQuery, Func: notFunc}
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case "name":
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qyOutput = &functionQuery{Input: b.firstInput, Func: nameFunc}
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case "last":
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qyOutput = &functionQuery{Input: b.firstInput, Func: lastFunc}
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case "position":
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qyOutput = &functionQuery{Input: b.firstInput, Func: positionFunc}
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case "count":
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//if b.firstInput == nil {
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// return nil, errors.New("xpath: expression must evaluate to node-set")
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//}
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if len(root.Args) == 0 {
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return nil, fmt.Errorf("xpath: count(node-sets) function must with have parameters node-sets")
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}
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argQuery, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: argQuery, Func: countFunc}
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case "sum":
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if len(root.Args) == 0 {
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return nil, fmt.Errorf("xpath: sum(node-sets) function must with have parameters node-sets")
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}
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argQuery, err := b.processNode(root.Args[0])
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if err != nil {
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return nil, err
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}
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qyOutput = &functionQuery{Input: argQuery, Func: sumFunc}
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case "concat":
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if len(root.Args) < 2 {
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return nil, fmt.Errorf("xpath: concat() must have at least two arguments")
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}
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var args []query
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for _, v := range root.Args {
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q, err := b.processNode(v)
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if err != nil {
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return nil, err
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}
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args = append(args, q)
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}
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qyOutput = &functionQuery{Input: b.firstInput, Func: concatFunc(args...)}
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default:
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return nil, fmt.Errorf("not yet support this function %s()", root.FuncName)
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}
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return qyOutput, nil
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}
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func (b *builder) processOperatorNode(root *operatorNode) (query, error) {
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left, err := b.processNode(root.Left)
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if err != nil {
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return nil, err
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}
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right, err := b.processNode(root.Right)
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if err != nil {
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return nil, err
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}
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var qyOutput query
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switch root.Op {
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case "+", "-", "div", "mod": // Numeric operator
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var exprFunc func(interface{}, interface{}) interface{}
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switch root.Op {
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case "+":
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exprFunc = plusFunc
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case "-":
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exprFunc = minusFunc
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case "div":
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exprFunc = divFunc
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case "mod":
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exprFunc = modFunc
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}
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qyOutput = &numericQuery{Left: left, Right: right, Do: exprFunc}
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case "=", ">", ">=", "<", "<=", "!=":
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var exprFunc func(iterator, interface{}, interface{}) interface{}
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switch root.Op {
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case "=":
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exprFunc = eqFunc
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case ">":
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exprFunc = gtFunc
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case ">=":
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exprFunc = geFunc
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case "<":
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exprFunc = ltFunc
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case "<=":
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exprFunc = leFunc
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case "!=":
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exprFunc = neFunc
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}
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qyOutput = &logicalQuery{Left: left, Right: right, Do: exprFunc}
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case "or", "and", "|":
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isOr := false
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if root.Op == "or" || root.Op == "|" {
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isOr = true
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}
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qyOutput = &booleanQuery{Left: left, Right: right, IsOr: isOr}
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}
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return qyOutput, nil
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}
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func (b *builder) processNode(root node) (q query, err error) {
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if b.depth = b.depth + 1; b.depth > 1024 {
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err = errors.New("the xpath expressions is too complex")
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return
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}
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switch root.Type() {
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case nodeConstantOperand:
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n := root.(*operandNode)
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q = &constantQuery{Val: n.Val}
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case nodeRoot:
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q = &contextQuery{Root: true}
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case nodeAxis:
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q, err = b.processAxisNode(root.(*axisNode))
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b.firstInput = q
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case nodeFilter:
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q, err = b.processFilterNode(root.(*filterNode))
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case nodeFunction:
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q, err = b.processFunctionNode(root.(*functionNode))
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case nodeOperator:
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q, err = b.processOperatorNode(root.(*operatorNode))
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}
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return
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}
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// build builds a specified XPath expressions expr.
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func build(expr string) (q query, err error) {
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defer func() {
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if e := recover(); e != nil {
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switch x := e.(type) {
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case string:
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err = errors.New(x)
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case error:
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err = x
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default:
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err = errors.New("unknown panic")
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}
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}
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}()
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root := parse(expr)
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b := &builder{}
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return b.processNode(root)
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}
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