generator.go

/*
MIT License
Copyright (c) 2020 akhettar

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
package main

import (
	"bytes"
	"errors"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"text/template"
	"time"

	"gopkg.in/yaml.v2"
)

// RepoName is the repo name to be processed
const RepoName = "repo"

// Config the Github action config
type Config struct {
	Description  string         `yaml:"description"`
	Repositories []Repositories `yaml:"repositories"`
}

// Repository type
type Repository = map[string]string

// Repositories type
type Repositories struct {
	Repo Repository `yaml:"repo,omitempty"`
}

// TemplateGenerator type
type TemplateGenerator struct {
	conf   *Config
	client *GitClient
}

// Report holds information about the processing of the repo
type Report struct {
	name string
	err  error
}

// Generartor creates an instance of the Templater
func Generartor() *TemplateGenerator {

	// make sure we are always starting from fresh git repo
	clearUp("repos/")

	// assert the presence of the required environment variable
	validate()

	// read the Github action template. At the moment only one config with all the defined the repositories to be processed
	data, err := ioutil.ReadFile("./config.yml")
	if err != nil {
		log.Fatal(err)
	}
	var config Config

	if err = yaml.NewDecoder(bytes.NewReader(data)).Decode(&config); err != nil {
		log.Fatal(err)
	}

	return &TemplateGenerator{conf: &config, client: NewGitClient()}
}

// generates all github action config for all the repos
func (t *TemplateGenerator) run() []Report {

	var wg sync.WaitGroup
	reportChan := make(chan Report, len(t.conf.Repositories))
	repo := os.Getenv(RepoName)

	for _, r := range t.conf.Repositories {
		repoName := getRepoName(r.Repo["url"])
		repoPath := fmt.Sprintf("repos/%s", repoName)
		branch := fmt.Sprintf("%s-%d", "githubAction", time.Now().UnixNano())

		// escaping the repos if the flag is set to process only one given repository
		if repo != "" && repoName != repo {
			log.Printf("[repo flag] %s", repo)
			log.Printf("[repo] %s", repoName)

			continue
		}

		log.Printf("processing repo: %s", r.Repo["url"])
		wg.Add(1)

		// process all the repositories in parallel
		go func(wg *sync.WaitGroup, result chan Report, r Repository) {
			defer wg.Done()
			//1. Prepare the repo
			url := r["url"]
			if err := t.client.prepareRepo(repoPath, branch, url); err != nil {
				log.Println("failed to prepare the repo")
				result <- Report{url, err}
				clearUp(repoPath)
				return
			}

			// 2. render the template write it the repo path
			if err := renderTemplate(r, repoPath); err != nil {
				result <- Report{url, err}
				clearUp(repoPath)
				return
			}

			// 3. push and commit
			if err := t.client.push(branch, url); err != nil {
				result <- Report{url, err}
				clearUp(repoPath)
				return
			}

			// clean up
			if dryRun, _ := strconv.ParseBool(os.Getenv(DryRun)); !dryRun {
				clearUp(repoPath)
			}

			// everything went well publish report in the chanel
			result <- Report{url, nil}

		}(&wg, reportChan, r.Repo)
	}

	// wait for all the reports to come through
	wg.Wait()
	close(reportChan)

	// print out the report
	reports := make([]Report, len(t.conf.Repositories), len(t.conf.Repositories))
	for r := range reportChan {
		if r.err != nil {
			log.Printf("failed to process the repo: %v with error: %v %v", r.name, r.err, "❌")
			reports = append(reports, r)
		} else {
			log.Printf("repo: %s was successfully processed: %v", r.name, "✅")
		}
	}
	log.Println("successfully completed processing of all the repositories")
	return reports
}

func renderTemplate(repo Repository, repoLocation string) error {

	gitHubDir := fmt.Sprintf("%s/%s", repoLocation, ".github")
	workflowDir := fmt.Sprintf("%s/%s", repoLocation, ".github/workflows")
	os.Mkdir(gitHubDir, os.ModePerm)
	os.Mkdir(workflowDir, os.ModePerm)

	err := filepath.Walk("templates/", func(path string, info os.FileInfo, err error) error {
		if filepath.Ext(path) == ".yml" {
			templateBytes, err := ioutil.ReadFile(path)
			t := template.Must(template.New("githubAction").Funcs(templateFunc()).Delims("{[", "]}").Parse(string(templateBytes)))

			//overwrite the config file with the template
			filePath := fmt.Sprintf("%s/.github/workflows/%s", repoLocation, filepath.Base(path))
			log.Printf("processing template: %s", filePath)

			banner, err := ioutil.ReadFile("banner")

			fileToWrite, err := os.OpenFile(filePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
			fileToWrite.Write(banner)

			if err != nil {
				log.Fatalf("failed to render the template, error: %v", err.Error())
				return err
			}
			defer fileToWrite.Close()

			if err = t.Execute(fileToWrite, repo); err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		log.Println("failed to load the templates")
		return err
	}
	return nil
}

// Template function to be called from the template
// exp: {[template "DEPLOYMENT" map "Env" "dev" "Name" .Name  "AWSAccountNumber" "326458601802" ]}
func templateFunc() template.FuncMap {
	return template.FuncMap{
		"ToUpper": strings.ToUpper,
		"map": func(values ...interface{}) (map[string]interface{}, error) {
			if len(values)%2 != 0 {
				return nil, errors.New("invalid map call")
			}
			dict := make(map[string]interface{}, len(values)/2)
			for i := 0; i < len(values); i += 2 {
				key, ok := values[i].(string)
				if !ok {
					return nil, errors.New("map keys must be strings")
				}
				dict[key] = values[i+1]
			}
			return dict, nil
		},
	}
}

// Asserts the presence of all the required environment variables
func validate() {

	// overriding the environement variables if new ones set as flags
	token := flag.String(GithubAuthToken, os.Getenv(GithubAuthToken), "Github token")
	if *token == "" {
		log.Fatalf("%s is required", GithubAuthToken)
	}

	email := flag.String(GithubEmail, os.Getenv(GithubEmail), "Github email")
	if *email == "" {
		log.Fatalf("%s is required", GithubEmail)
	}

	pwd := flag.String(GPGPassword, os.Getenv(GPGPassword), "GPG password")
	repo := flag.String(RepoName, "", "repo name to be processed")
	dryrun := flag.String(DryRun, "false", "flag to disable pushing the changes to the branch and creating pull request")

	flag.Parse()

	os.Setenv(GPGPassword, *pwd)
	os.Setenv(RepoName, *repo)
	os.Setenv(GithubAuthToken, *token)
	os.Setenv(GithubEmail, *email)
	os.Setenv(DryRun, *dryrun)
}

func clearUp(path string) {
	if err := os.RemoveAll(path); err != nil {
		log.Printf("failed to delete the generated local repository: %s", path)
	}
}