mirror of https://github.com/mikefarah/yq.git
110 lines
3.8 KiB
Go
110 lines
3.8 KiB
Go
package yqlib
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import (
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"errors"
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logging "gopkg.in/op/go-logging.v1"
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)
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type expressionPostFixer interface {
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ConvertToPostfix([]*token) ([]*Operation, error)
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}
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type expressionPostFixerImpl struct {
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}
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func newExpressionPostFixer() expressionPostFixer {
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return &expressionPostFixerImpl{}
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}
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func popOpToResult(opStack []*token, result []*Operation) ([]*token, []*Operation) {
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var newOp *token
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opStack, newOp = opStack[0:len(opStack)-1], opStack[len(opStack)-1]
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log.Debugf("popped %v from opstack to results", newOp.toString(true))
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return opStack, append(result, newOp.Operation)
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}
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func (p *expressionPostFixerImpl) ConvertToPostfix(infixTokens []*token) ([]*Operation, error) {
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var result []*Operation
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// surround the whole thing with brackets
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var opStack = []*token{{TokenType: openBracket}}
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var tokens = append(infixTokens, &token{TokenType: closeBracket})
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for _, currentToken := range tokens {
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log.Debugf("postfix processing currentToken %v", currentToken.toString(true))
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switch currentToken.TokenType {
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case openBracket, openCollect, openCollectObject:
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opStack = append(opStack, currentToken)
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log.Debugf("put %v onto the opstack", currentToken.toString(true))
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case closeCollect, closeCollectObject:
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var opener tokenType = openCollect
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var collectOperator *operationType = collectOpType
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if currentToken.TokenType == closeCollectObject {
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opener = openCollectObject
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collectOperator = collectObjectOpType
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}
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for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != opener {
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opStack, result = popOpToResult(opStack, result)
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}
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if len(opStack) == 0 {
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return nil, errors.New("Bad path expression, got close collect brackets without matching opening bracket")
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}
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// now we should have [ as the last element on the opStack, get rid of it
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opStack = opStack[0 : len(opStack)-1]
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log.Debugf("deleteing open bracket from opstack")
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//and append a collect to the result
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// hack - see if there's the optional traverse flag
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// on the close op - move it to the collect op.
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// allows for .["cat"]?
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prefs := traversePreferences{}
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closeTokenMatch := string(currentToken.Match.Bytes)
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if closeTokenMatch[len(closeTokenMatch)-1:] == "?" {
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prefs.OptionalTraverse = true
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}
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result = append(result, &Operation{OperationType: collectOperator, Preferences: prefs})
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log.Debugf("put collect onto the result")
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result = append(result, &Operation{OperationType: shortPipeOpType})
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log.Debugf("put shortpipe onto the result")
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//traverseArrayCollect is a sneaky op that needs to be included too
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//when closing a []
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if len(opStack) > 0 && opStack[len(opStack)-1].Operation != nil && opStack[len(opStack)-1].Operation.OperationType == traverseArrayOpType {
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opStack, result = popOpToResult(opStack, result)
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}
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case closeBracket:
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for len(opStack) > 0 && opStack[len(opStack)-1].TokenType != openBracket {
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opStack, result = popOpToResult(opStack, result)
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}
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if len(opStack) == 0 {
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return nil, errors.New("Bad path expression, got close brackets without matching opening bracket")
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}
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// now we should have ( as the last element on the opStack, get rid of it
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opStack = opStack[0 : len(opStack)-1]
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default:
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var currentPrecedence = currentToken.Operation.OperationType.Precedence
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// pop off higher precedent operators onto the result
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for len(opStack) > 0 &&
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opStack[len(opStack)-1].TokenType == operationToken &&
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opStack[len(opStack)-1].Operation.OperationType.Precedence > currentPrecedence {
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opStack, result = popOpToResult(opStack, result)
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}
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// add this operator to the opStack
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opStack = append(opStack, currentToken)
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log.Debugf("put %v onto the opstack", currentToken.toString(true))
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}
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}
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if log.IsEnabledFor(logging.DEBUG) {
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log.Debugf("PostFix Result:")
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for _, currentToken := range result {
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log.Debugf("> %v", currentToken.toString())
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}
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}
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return result, nil
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}
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