Implement the converting logic

Author: hunts

.gitignore

@@ -1,15 +1,2 @@
-# Binaries for programs and plugins
-*.exe
-*.exe~
-*.dll
-*.so
-*.dylib
-
-# Test binary, built with `go test -c`
-*.test
-
-# Output of the go coverage tool, specifically when used with LiteIDE
-*.out
-
-# Dependency directories (remove the comment below to include it)
-# vendor/
+# Dependency directories
+vendor/

README.md

@@ -1,2 +1,15 @@
 # yamllint-to-checkstyle
-This is a CLI program that takes yamlint parsable output and converts it to checkstyle format.
+
+A commandline program that takes [yamlint](https://github.com/adrienverge/yamllint) parsable output and converts it to [checkstyle](https://checkstyle.sourceforge.io/) format.
+
+## Installation
+
+```shell
+go install github.com/hunts/yamllint-to-checkstyle@latest
+```
+
+## Usage
+
+```shell
+yamllint --format=parsable file.yaml | yamllint-to-checkstyle
+```

go.mod

@@ -0,0 +1,3 @@
+module github.com/hunts/yamllint-to-checkstyle
+
+go 1.12

main.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"bufio"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var (
+	input    = os.Stdin
+	output   = os.Stdout
+	parsable = regexp.MustCompile(`^(?P<file>.+?):(?P<line>\d+):(?P<column>\d+):\s+\[(?P<level>[a-z]+)\]\s+(?P<desc>.+?)(?P<rule>\s+\([a-z-]+\))?\n$`)
+)
+
+type Checkstyle struct {
+	XMLName xml.Name `xml:"checkstyle"`
+	Version string   `xml:"version,attr"`
+	Files   []*File
+}
+
+type File struct {
+	XMLName  xml.Name `xml:"file"`
+	Name     string   `xml:"name,attr"`
+	Problems []Problem
+}
+
+type Problem struct {
+	XMLName  xml.Name `xml:"error"`
+	Line     int      `xml:"line,attr"`
+	Column   int      `xml:"column,attr"`
+	Severity string   `xml:"severity,attr"`
+	Source   string   `xml:"source,attr,omitempty"`
+	Message  string   `xml:"message,attr"`
+}
+
+func main() {
+	reader := bufio.NewReader(input)
+	err := process(reader, output)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func process(r *bufio.Reader, w io.Writer) error {
+	fileMap := map[string]*File{}
+	var fileOrder []string
+
+	for {
+		line, err := r.ReadString('\n')
+		if err != nil {
+			break
+		}
+
+		match := parsable.FindStringSubmatch(line)
+		if len(match) < 7 {
+			return fmt.Errorf("unparsable line: %s", line)
+		}
+
+		filename, line_str, column_str, level, desc, rule := match[1], match[2], match[3], match[4], match[5], match[6]
+		line_no, _ := strconv.Atoi(line_str)
+		column_no, _ := strconv.Atoi(column_str)
+		problem := Problem{Line: line_no, Column: column_no, Severity: level, Source: strings.Trim(rule, " ()"), Message: desc}
+
+		file, ok := fileMap[filename]
+		if !ok {
+			fileOrder = append(fileOrder, filename)
+			fileMap[filename] = &File{Name: filename, Problems: []Problem{problem}}
+		} else {
+			file.Problems = append(file.Problems, problem)
+		}
+	}
+
+	var files []*File
+	for _, filename := range fileOrder {
+		files = append(files, fileMap[filename])
+	}
+
+	data, err := xml.MarshalIndent(Checkstyle{Version: "5.0", Files: files}, "", "    ")
+	if err != nil {
+		return err
+	}
+
+	fmt.Fprint(w, xml.Header)
+	w.Write(data)
+	w.Write([]byte("\n"))
+	return nil
+}