Fix #67: Support basic XPath functions

Author: sibprogrammer

internal/utils/utils.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"github.com/PuerkitoBio/goquery"
 	"github.com/antchfx/xmlquery"
+	"github.com/antchfx/xpath"
 	"github.com/fatih/color"
 	"golang.org/x/net/html"
 	"golang.org/x/text/encoding/ianaindex"
@@ -214,13 +215,37 @@ func XPathQuery(reader io.Reader, writer io.Writer, query string, singleNode boo
 		if n := xmlquery.FindOne(doc, query); n != nil {
 			return printNodeContent(writer, n, options)
 		}
-	} else {
+	} else if options.WithTags {
 		for _, n := range xmlquery.Find(doc, query) {
 			err := printNodeContent(writer, n, options)
 			if err != nil {
 				return err
 			}
 		}
+	} else {
+		expr, _ := xpath.Compile(query)
+		val := expr.Evaluate(xmlquery.CreateXPathNavigator(doc))
+
+		switch typedVal := val.(type) {
+		case float64:
+			_, err = fmt.Fprintf(writer, "%.0f\n", typedVal)
+		case string:
+			_, err = fmt.Fprintf(writer, "%s\n", strings.TrimSpace(typedVal))
+		case *xpath.NodeIterator:
+			for typedVal.MoveNext() {
+				typedVal.Current()
+				_, err = fmt.Fprintf(writer, "%s\n", strings.TrimSpace(typedVal.Current().Value()))
+				if err != nil {
+					break
+				}
+			}
+		default:
+			return fmt.Errorf("unknown type error: %v", val)
+		}
+
+		if err != nil {
+			return err
+		}
 	}
 
 	return nil

internal/utils/utils_test.go

@@ -102,21 +102,23 @@ func TestXPathQuery(t *testing.T) {
 	type test struct {
 		input  string
 		node   bool
+		single bool
 		query  string
 		result string
 	}
 
 	tests := []test{
-		{input: "formatted.xml", node: false, query: "//first_name", result: "John"},
-		{input: "unformatted8.xml", node: false, query: "//title", result: "Some Title"},
-		{input: "unformatted8.xml", node: true, query: "//title", result: "<title>Some Title</title>"},
+		{input: "formatted.xml", node: false, single: true, query: "//first_name", result: "John"},
+		{input: "unformatted8.xml", node: false, single: true, query: "//title", result: "Some Title"},
+		{input: "unformatted8.xml", node: true, single: true, query: "//title", result: "<title>Some Title</title>"},
+		{input: "unformatted8.xml", node: false, single: false, query: "count(//link)", result: "2"},
 	}
 
 	for _, testCase := range tests {
 		fileReader := getFileReader(path.Join("..", "..", "test", "data", "xml", testCase.input))
 		output := new(strings.Builder)
 		options := QueryOptions{WithTags: testCase.node, Indent: "  "}
-		err := XPathQuery(fileReader, output, testCase.query, true, options)
+		err := XPathQuery(fileReader, output, testCase.query, testCase.single, options)
 		assert.Nil(t, err)
 		assert.Equal(t, testCase.result, strings.Trim(output.String(), "\n"))
 	}