Renaming pathtree to expression

pkg/yqlib/expression_parser.go

@@ -0,0 +1,76 @@
+package yqlib
+
+import (
+	"fmt"
+	"strings"
+)
+
+var myPathTokeniser = newExpressionTokeniser()
+var myPathPostfixer = newExpressionPostFixer()
+
+type ExpressionNode struct {
+	Operation *Operation
+	Lhs       *ExpressionNode
+	Rhs       *ExpressionNode
+}
+
+type ExpressionParser interface {
+	ParseExpression(expression string) (*ExpressionNode, error)
+}
+
+type expressionParserImpl struct {
+}
+
+func NewExpressionParser() ExpressionParser {
+	return &expressionParserImpl{}
+}
+
+func (p *expressionParserImpl) ParseExpression(expression string) (*ExpressionNode, error) {
+	tokens, err := myPathTokeniser.Tokenise(expression)
+	if err != nil {
+		return nil, err
+	}
+	var Operations []*Operation
+	Operations, err = myPathPostfixer.ConvertToPostfix(tokens)
+	if err != nil {
+		return nil, err
+	}
+	return p.createExpressionTree(Operations)
+}
+
+func (p *expressionParserImpl) createExpressionTree(postFixPath []*Operation) (*ExpressionNode, error) {
+	var stack = make([]*ExpressionNode, 0)
+
+	if len(postFixPath) == 0 {
+		return nil, nil
+	}
+
+	for _, Operation := range postFixPath {
+		var newNode = ExpressionNode{Operation: Operation}
+		log.Debugf("pathTree %v ", Operation.toString())
+		if Operation.OperationType.NumArgs > 0 {
+			numArgs := Operation.OperationType.NumArgs
+			if numArgs == 1 {
+				if len(stack) < 1 {
+					return nil, fmt.Errorf("'%v' expects 1 arg but received none", strings.TrimSpace(Operation.StringValue))
+				}
+				remaining, rhs := stack[:len(stack)-1], stack[len(stack)-1]
+				newNode.Rhs = rhs
+				stack = remaining
+			} else if numArgs == 2 {
+				if len(stack) < 2 {
+					return nil, fmt.Errorf("'%v' expects 2 args but there is %v", strings.TrimSpace(Operation.StringValue), len(stack))
+				}
+				remaining, lhs, rhs := stack[:len(stack)-2], stack[len(stack)-2], stack[len(stack)-1]
+				newNode.Lhs = lhs
+				newNode.Rhs = rhs
+				stack = remaining
+			}
+		}
+		stack = append(stack, &newNode)
+	}
+	if len(stack) != 1 {
+		return nil, fmt.Errorf("expected end of expression but found '%v', please check expression syntax", strings.TrimSpace(stack[1].Operation.StringValue))
+	}
+	return stack[0], nil
+}