mirror of https://github.com/mikefarah/yq.git
76 lines
2.0 KiB
Go
76 lines
2.0 KiB
Go
package yqlib
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import (
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"fmt"
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"strings"
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)
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type ExpressionNode struct {
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Operation *Operation
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Lhs *ExpressionNode
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Rhs *ExpressionNode
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}
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type ExpressionParser interface {
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ParseExpression(expression string) (*ExpressionNode, error)
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}
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type expressionParserImpl struct {
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pathTokeniser expressionTokeniser
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pathPostFixer expressionPostFixer
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}
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func NewExpressionParser() ExpressionParser {
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return &expressionParserImpl{newExpressionTokeniser(), newExpressionPostFixer()}
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}
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func (p *expressionParserImpl) ParseExpression(expression string) (*ExpressionNode, error) {
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tokens, err := p.pathTokeniser.Tokenise(expression)
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if err != nil {
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return nil, err
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}
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var Operations []*Operation
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Operations, err = p.pathPostFixer.ConvertToPostfix(tokens)
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if err != nil {
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return nil, err
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}
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return p.createExpressionTree(Operations)
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}
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func (p *expressionParserImpl) createExpressionTree(postFixPath []*Operation) (*ExpressionNode, error) {
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var stack = make([]*ExpressionNode, 0)
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if len(postFixPath) == 0 {
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return nil, nil
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}
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for _, Operation := range postFixPath {
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var newNode = ExpressionNode{Operation: Operation}
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log.Debugf("pathTree %v ", Operation.toString())
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if Operation.OperationType.NumArgs > 0 {
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numArgs := Operation.OperationType.NumArgs
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if numArgs == 1 {
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if len(stack) < 1 {
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return nil, fmt.Errorf("'%v' expects 1 arg but received none", strings.TrimSpace(Operation.StringValue))
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}
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remaining, rhs := stack[:len(stack)-1], stack[len(stack)-1]
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newNode.Rhs = rhs
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stack = remaining
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} else if numArgs == 2 {
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if len(stack) < 2 {
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return nil, fmt.Errorf("'%v' expects 2 args but there is %v", strings.TrimSpace(Operation.StringValue), len(stack))
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}
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remaining, lhs, rhs := stack[:len(stack)-2], stack[len(stack)-2], stack[len(stack)-1]
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newNode.Lhs = lhs
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newNode.Rhs = rhs
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stack = remaining
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}
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}
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stack = append(stack, &newNode)
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}
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if len(stack) != 1 {
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return nil, fmt.Errorf("Bad expression, please check expression syntax")
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}
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return stack[0], nil
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}
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