// Copyright 2019 The gVisor Authors.
//
// 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.

// Binary github is the entry point for GitHub utilities.
package main

import (
	"context"
	"flag"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"strings"

	"github.com/google/go-github/github"
	"golang.org/x/oauth2"
	"gvisor.dev/gvisor/tools/github/nogo"
	"gvisor.dev/gvisor/tools/github/reviver"
)

var (
	owner     string
	repo      string
	tokenFile string
	path      string
	commit    string
	dryRun    bool
)

// Keep the options simple for now. Supports only a single path and repo.
func init() {
	flag.StringVar(&owner, "owner", "", "GitHub project org/owner (required, except nogo dry-run)")
	flag.StringVar(&repo, "repo", "", "GitHub repo (required, except nogo dry-run)")
	flag.StringVar(&tokenFile, "oauth-token-file", "", "file containing the GitHub token (or GITHUB_TOKEN is set)")
	flag.StringVar(&path, "path", ".", "path to scan (required for revive and nogo)")
	flag.StringVar(&commit, "commit", "", "commit to associated (required for nogo, except dry-run)")
	flag.BoolVar(&dryRun, "dry-run", false, "just print changes to be made")
}

func main() {
	// Set defaults from the environment.
	repository := os.Getenv("GITHUB_REPOSITORY")
	if parts := strings.SplitN(repository, "/", 2); len(parts) == 2 {
		owner = parts[0]
		repo = parts[1]
	}

	// Parse flags.
	flag.Usage = func() {
		fmt.Fprintf(flag.CommandLine.Output(), "usage: %s [options] <command>\n", os.Args[0])
		fmt.Fprintf(flag.CommandLine.Output(), "commands: revive, nogo\n")
		flag.PrintDefaults()
	}
	flag.Parse()
	args := flag.Args()
	if len(args) != 1 {
		fmt.Fprintf(flag.CommandLine.Output(), "extra arguments: %s\n", strings.Join(args[1:], ", "))
		flag.Usage()
		os.Exit(1)
	}

	// Check for mandatory parameters.
	command := args[0]
	if len(owner) == 0 && (command != "nogo" || !dryRun) {
		fmt.Fprintln(flag.CommandLine.Output(), "missing --owner option.")
		flag.Usage()
		os.Exit(1)
	}
	if len(repo) == 0 && (command != "nogo" || !dryRun) {
		fmt.Fprintln(flag.CommandLine.Output(), "missing --repo option.")
		flag.Usage()
		os.Exit(1)
	}
	if len(path) == 0 {
		fmt.Fprintln(flag.CommandLine.Output(), "missing --path option.")
		flag.Usage()
		os.Exit(1)
	}

	// The access token may be passed as a file so it doesn't show up in
	// command line arguments. It also may be provided through the
	// environment to faciliate use through GitHub's CI system.
	token := os.Getenv("GITHUB_TOKEN")
	if len(tokenFile) != 0 {
		bytes, err := ioutil.ReadFile(tokenFile)
		if err != nil {
			fmt.Println(err.Error())
			os.Exit(1)
		}
		token = string(bytes)
	}
	var client *github.Client
	if len(token) == 0 {
		// Client is unauthenticated.
		client = github.NewClient(nil)
	} else {
		// Using the above token.
		ts := oauth2.StaticTokenSource(
			&oauth2.Token{AccessToken: token},
		)
		tc := oauth2.NewClient(context.Background(), ts)
		client = github.NewClient(tc)
	}

	switch command {
	case "revive":
		// Load existing GitHub bugs.
		bugger, err := reviver.NewGitHubBugger(client, owner, repo, dryRun)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error getting github issues: %v\n", err)
			os.Exit(1)
		}
		// Scan the provided path.
		rev := reviver.New([]string{path}, []reviver.Bugger{bugger})
		if errs := rev.Run(); len(errs) > 0 {
			fmt.Fprintf(os.Stderr, "Encountered %d errors:\n", len(errs))
			for _, err := range errs {
				fmt.Fprintf(os.Stderr, "\t%v\n", err)
			}
			os.Exit(1)
		}
	case "nogo":
		// Did we get a commit? Try to extract one.
		if len(commit) == 0 && !dryRun {
			cmd := exec.Command("git", "rev-parse", "HEAD")
			revBytes, err := cmd.Output()
			if err != nil {
				fmt.Fprintf(flag.CommandLine.Output(), "missing --commit option, unable to infer: %v\n", err)
				flag.Usage()
				os.Exit(1)
			}
			commit = strings.TrimSpace(string(revBytes))
		}
		// Scan all findings.
		poster := nogo.NewFindingsPoster(client, owner, repo, commit, dryRun)
		if err := poster.Walk(path); err != nil {
			fmt.Fprintln(os.Stderr, "Error finding nogo findings:", err)
			os.Exit(1)
		}
		// Post to GitHub.
		if err := poster.Post(); err != nil {
			fmt.Fprintln(os.Stderr, "Error posting nogo findings:", err)
		}
	default:
		// Not a known command.
		fmt.Fprintf(flag.CommandLine.Output(), "unknown command: %s\n", command)
		flag.Usage()
		os.Exit(1)
	}
}