package main

import (
	"context"
	"flag"
	"log"
	"net/http"
	"os/user"
	"path/filepath"
	"strings"
	"time"

	"go.skia.org/infra/go/auth"
	"go.skia.org/infra/go/common"
	"go.skia.org/infra/go/fileutil"
	"go.skia.org/infra/go/git"
	"go.skia.org/infra/go/gitauth"
	"go.skia.org/infra/go/gitstore"
	"go.skia.org/infra/go/httputils"
	"go.skia.org/infra/go/sklog"
)

// This server watches a list of git repos for changes and syncs the meta data of all commits
// to a BigTable backed datastore.

func main() {
	// Define the flags and parse them.
	var (
		btInstanceID    = flag.String("bt_instance", "production", "Big Table instance")
		btTableID       = flag.String("bt_table", "git-repos", "BigTable table ID")
		httpPort        = flag.String("http_port", ":9091", "The http port where ready-ness endpoints are served.")
		local           = flag.Bool("local", false, "Running locally if true. As opposed to in production.")
		projectID       = flag.String("project", "skia-public", "ID of the GCP project")
		repoURLs        = common.NewMultiStringFlag("repo_url", []string{}, "Repo url")
		runInit         = flag.Bool("init", false, "Initialize the BigTable instance and quit. This should be run with a different different user who has admin rights.")
		refreshInterval = flag.Duration("refresh", 10*time.Minute, "Interval in which to poll git and refresh the GitStore.")
		workDir         = flag.String("workdir", "", "Working directory where repos are cached. Use the same directory between calls to speed up checkout time.")
	)
	common.Init()

	// Make sure we have a data directory and it exists or can be created.
	if *workDir == "" {
		sklog.Fatal("No workdir specified.")
	}
	useWorkDir := fileutil.Must(fileutil.EnsureDirExists(*workDir))

	// Make sure we have at least one repo configured.
	if len(*repoURLs) == 0 {
		sklog.Fatalf("At least one repository URL must be configured.")
	}

	// TODO(stephana): Pass the token source explicitly to the BigTable related functions below.

	// Create token source.
	ts, err := auth.NewDefaultTokenSource(false, auth.SCOPE_USERINFO_EMAIL, auth.SCOPE_GERRIT)
	if err != nil {
		sklog.Fatalf("Problem setting up default token source: %s", err)
	}

	// Set up Git authentication if a service account email was set.
	if !*local {
		user, err := user.Current()
		if err != nil {
			sklog.Fatal(err)
		}

		// Use the gitcookie created by gitauth package if .gitcookies does not already exist.
		gitcookiesPath := filepath.Join(user.HomeDir, ".gitcookies")
		if _, err := gitauth.New(ts, gitcookiesPath, true, ""); err != nil {
			sklog.Fatalf("Failed to create git cookie updater: %s", err)
		}
		sklog.Infof("Git authentication set up successfully.")
	}

	// Configure the bigtable instance.
	config := &gitstore.BTConfig{
		ProjectID:  *projectID,
		InstanceID: *btInstanceID,
		TableID:    *btTableID,
	}

	// Initialize bigtable if invoked with --init and quit.
	// This should be invoked with a user that has admin privileges, so that the production user that
	// wants to write to the instance does not need admin privileges.
	if *runInit {
		if err := gitstore.InitBT(config); err != nil {
			sklog.Fatalf("Error initializing BT: %s", err)
		}
		sklog.Infof("BigTable instance %s and table %s in project %s initialized.", *btInstanceID, *btTableID, *projectID)
		return
	}

	// Start all repo watchers in the background.
	ctx := context.Background()
	for _, repoURL := range *repoURLs {
		go func(repoURL string) {
			repoDir, err := git.NormalizeURL(repoURL)
			if err != nil {
				sklog.Fatalf("Error getting normalized URL for %q:  %s", repoURL, err)
			}
			repoDir = strings.Replace(repoDir, "/", "_", -1)
			repoDir = filepath.Join(useWorkDir, repoDir)
			sklog.Infof("Checking out %s into %s", repoURL, repoDir)

			watcher, err := NewRepoWatcher(ctx, config, repoURL, repoDir)
			if err != nil {
				sklog.Fatalf("Error initializing repo watcher: %s", err)
			}
			watcher.Start(ctx, *refreshInterval)
		}(repoURL)
	}

	// Set up the http handler to indicate ready-ness and start serving.
	http.HandleFunc("/healthz", httputils.ReadyHandleFunc)
	log.Fatal(http.ListenAndServe(*httpPort, nil))
}