/*
Copyright 2013 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// Package checkstyle provides helper methods for invoking checkstyle
// against GWT's source code.
package checkstyle

import (
	"encoding/xml"
	"flag"
	"io"
	"log"
	"os"
	"os/exec"
	"strings"
)

var checkstylejar = flag.String("checkstylejar", "../tools/antlib/checkstyle-5.7-all.jar", "path to checkstyle jar")

// Error represents a specific instance of an error reported by checkstyle.
type Error struct {
	Line     int    `xml:"line,attr"`
	Severity string `xml:"severity,attr"`
	Message  string `xml:"message,attr"`
}

// File represents a collection of checkstyle errors for a single file.
type File struct {
	Name   string  `xml:"name,attr"`
	Errors []Error `xml:"error"`
}

// ReadXML reads a checkstyle XML report from reader.
func ReadXML(reader io.Reader, pathPrefix string) ([]File, error) {
	var res struct {
		Files []File `xml:"file"`
	}
	if err := xml.NewDecoder(reader).Decode(&res); err != nil {
		return nil, err
	}

	if !strings.HasSuffix(pathPrefix, "/") {
		pathPrefix += "/"
	}

	for i := range res.Files {
		// Make sure the filenames are relative.
		res.Files[i].Name = strings.TrimPrefix(res.Files[i].Name, pathPrefix)
	}
	return res.Files, nil
}

// Run runs checkstyle using the specified config against the specified
// list of files and returns the style errors found.
func Run(config string, files []string) (outfiles []File, err error) {
	if len(files) == 0 {
		return []File{}, nil
	}

	workingDir, err := os.Getwd()
	if err != nil {
		return nil, err
	}

	cmd := exec.Command("java", append([]string{"-cp", *checkstylejar,
		"-Dcheckstyle.header.file=eclipse/settings/code-style/google.header",
		"com.puppycrawl.tools.checkstyle.Main", "-f", "xml", "-c", config},
		files...)...)
	reader, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	defer reader.Close()
	cmd.Stderr = os.Stderr
	log.Println("running checkstyle:", cmd.Args)
	if err = cmd.Start(); err != nil {
		return nil, err
	}
	// TODO(mdempsky): Check cmd.Wait() exit code?
	defer cmd.Wait()
	return ReadXML(reader, workingDir)
}