// Copyright 2023 wanderer <a_mirre at utb dot cz>
// SPDX-License-Identifier: AGPL-3.0-only

package main

import (
	"context"
	"flag"
	"fmt"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"sync"
	"syscall"
	"time"

	"golang.org/x/exp/slog"
	// pure go postgres driver.
	_ "github.com/lib/pq"
	// ent pure go sqlite3 driver instead of "github.com/mattn/go-sqlite3".
	_ "github.com/xiaoqidun/entps"

	"git.dotya.ml/mirre-mt/pcmt/app"
	"git.dotya.ml/mirre-mt/pcmt/app/settings"
	"git.dotya.ml/mirre-mt/pcmt/config"
	"git.dotya.ml/mirre-mt/pcmt/ent"
	moddb "git.dotya.ml/mirre-mt/pcmt/modules/db"
	"git.dotya.ml/mirre-mt/pcmt/modules/hibp"
	"git.dotya.ml/mirre-mt/pcmt/modules/localbreach"
	"git.dotya.ml/mirre-mt/pcmt/slogging"
)

const (
	banner = `
██████╗  ██████╗███╗   ███╗████████╗
██╔══██╗██╔════╝████╗ ████║╚══██╔══╝
██████╔╝██║     ██╔████╔██║   ██║
██╔═══╝ ██║     ██║╚██╔╝██║   ██║
██║     ╚██████╗██║ ╚═╝ ██║   ██║
╚═╝      ╚═════╝╚═╝     ╚═╝   ╚═╝
`
	slug = `Password Compromise Monitoring Tool
version: '%s'
https://git.dotya.ml/mirre-mt/pcmt
____________________________________`

	licenseHeader = `pcmt - Password Compromise Monitoring Tool
Copyright (C) git.dotya.ml/wanderer

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.`
)

var (
	version = "dev"
	// the global logger.
	slogger *slogging.Slogger
	// local logger instance.
	log slogging.Slogger
)

func run() error { //nolint:gocognit
	flag.Parse()

	if *licenseFlag {
		fmt.Fprintln(os.Stderr, licenseHeader)
		return nil
	}

	if *versionFlag {
		fmt.Fprintf(os.Stderr, "pcmt version %s\n", version)
		return nil
	}

	// skip printing program header and some other stuff.
	shortCircuit := false

	var doingImport bool

	if importFlag != nil && *importFlag != "" {
		doingImport = true
		shortCircuit = true

		config.BeQuiet()
	}

	if *printMigrationFlag {
		shortCircuit = true

		config.BeQuiet()
	}

	if !shortCircuit {
		printHeader()
	}

	slogger = slogging.Logger()
	if slogger == nil {
		slogger = slogging.Init(true)
	}

	log = *slogger // local copy.
	log.Logger = log.Logger.With(
		// local attrs.
		slog.Group("pcmt extra", slog.String("module", "run")),
	)

	// TODO: allow different configuration formats (toml, ini)
	// TODO: rename main.go to pcmt.go
	// TODO: add flake.nix
	// TODO: SBOM: https://actuated.dev/blog/sbom-in-github-actions
	// TODO: SBOM: https://www.docker.com/blog/generate-sboms-with-buildkit/
	// TODO: integrate with Graylog (https://github.com/samber/slog-graylog).
	// TODO: add mailer (https://github.com/wneessen/go-mail).
	// TODO: deploy containers with podman using Ansible (https://www.redhat.com/sysadmin/automate-podman-ansible)
	// TODO: add health checks for pod's containers (db, app)

	// load the config if possible, an error could mean multiple things:
	// * just couldn't read the config
	// * parsed the config but:
	//   * the schema provided is too new for the app - keep the older schema or update the app
	//   * the schema provided is too old for the app - upgrade the config schema or downgrade the app
	conf, err := config.Load(*configFlag, *configIsPathFlag)
	if err != nil {
		return fmt.Errorf("couldn't load the configuration (isPath: '%t') '%s', full err: %w",
			*configIsPathFlag, *configFlag, err,
		)
	}

	setting := settings.New()

	if !shortCircuit {
		setting.Consolidate(
			conf, hostFlag, portFlag, develFlag, version,
		)
	}

	// expected connstring form for "github.com/xiaoqidun/entps":
	// "file:ent?mode=memory&cache=shared&_fk=1"
	// and for the postgres driver "github.com/lib/pq":
	// "host=127.0.0.1 sslmode=disable port=5432 user=postgres dbname=postgres password=postgres".

	connstr := os.Getenv("PCMT_CONNSTRING")
	dbtype := os.Getenv("PCMT_DBTYPE")

	// check and bail early.
	switch {
	case connstr == "" || dbtype == "":
		log.Errorf("PCMT_CONNSTRING or PCMT_DBTYPE or *both* were UNSET, bailing...")
		return errDBNotConfigured

	case dbtype != "postgres" && dbtype != "sqlite3":
		log.Errorf("unsupported DB type specified, bailing...")
		return errUnsupportedDBType

	default:
		setting.SetDbConnstring(connstr)
		// type can be one of "postgres" or "sqlite3".
		setting.SetDbType(dbtype)
	}

	log.Infof("connecting to db at '%s'", connstr)

	db, err := ent.Open(setting.DbType(), setting.DbConnstring())
	if err != nil {
		if doingImport {
			log.Error("Import was not possible", "error", err)
			fmt.Fprintf(os.Stdout, "\033[31m✗\033[0m Import was not possible due to an error: %q\n", err)

			return errImportFailed
		}

		log.Errorf("Error while connecting to DB: %q", err)

		return errDBConnFailed
	}
	defer db.Close()

	ctx := context.WithValue(context.Background(), moddb.CtxKey{}, slogger)

	if *printMigrationFlag {
		log.Debug("printing the following migration to stdout")
		return moddb.PrintMigration(ctx, db)
	}

	log.Info("ensuring the db is set up and attempting to automatically migrate db schema")

	// make sure the database is set up and optionally creates an administrator
	// user (only when setting up the db).
	if err = moddb.SetUp(ctx, db, setting.InitCreateAdmin(), setting.InitAdminPassword()); err != nil {
		return err
	}

	setting.SetDbIsSetUp(true)

	// don't load the app, return early.
	if doingImport {
		lb, err := localbreach.Load(*importFlag)
		if err != nil {
			return err
		}

		if _, err = localbreach.ImportLocalBreach(
			context.WithValue(
				context.Background(), localbreach.CtxKey{}, slogger),
			db, lb,
		); err != nil {
			return err
		}

		log.Infof("Import succeeded: %+v", lb)
		fmt.Fprint(os.Stdout, "\033[32m✓\033[0m Import succeeded \n")

		return nil
	}

	a := &app.App{}

	if err = a.Init(setting, slogger, db); err != nil {
		return err
	}

	a.PrintConfiguration()
	a.SetEmbeds(templates, assets)

	if err = a.SetupRoutes(); err != nil {
		return err
	}

	a.SetServerSettings()

	if err = setting.EraseENVs(); err != nil {
		log.Error("failed to erase PCMT ENVs")
		return err
	}

	log.Debug("erased PCMT ENVs")

	e := a.E()
	// channel used to check whether the app had troubles starting up.
	started := make(chan error, 1)

	go func() {
		defer close(started)

		p := setting.Port()
		h := setting.Host()

		address := h + ":" + strconv.Itoa(p)

		if err := e.Start(address); err != nil && err != http.ErrServerClosed {
			log.Error("troubles running the server, bailing...", "error", err)

			started <- err

			return
		}

		started <- nil
	}()

	quit := make(chan os.Signal, 1)
	schedQuit := make(chan os.Signal, 1)
	errCh := make(chan error, 1)
	wg := &sync.WaitGroup{}

	handleSigs(schedQuit, quit)

	go func() {
		wg.Add(1)                                     // nolint:staticcheck
		go hibp.RunReqScheduler(schedQuit, errCh, wg) // nolint:wsl
	}()

	// non-blocking channel receive.
	select {
	// monitor the server start-up chan.
	case err := <-started:
		if err != nil {
			return err
		}

	case err := <-errCh:
		defer func() {
			signal.Stop(quit)

			close(quit)
			close(errCh)
		}()

		if err != nil {
			return errHIBPSchedulerFailed
		}

	case <-quit:
		// after the timeout the server forcefully quits.
		shutdownTimeout := 10 * time.Second

		log.Infof("Interrupt received, gracefully shutting down the server (timeout %s)", shutdownTimeout)

		ctx, cancel := context.WithTimeout(context.Background(), shutdownTimeout)
		defer func() {
			cancel()

			signal.Stop(quit)

			close(quit)
			close(errCh)

			log.Info("Bye!")
		}()

		if err = e.Shutdown(ctx); err != nil {
			log.Error("There was an error shutting the server down")
			return err
		}

		select {
		case <-ctx.Done():
			log.Error("Failed to stop the server in time, yolo")
			return ctx.Err()

		default:
			wg.Wait()
		}
	}

	return nil
}

// handleSigs configures given chans to be notified on os signals.
func handleSigs(chans ...chan os.Signal) {
	sigs := []os.Signal{os.Interrupt, syscall.SIGHUP, syscall.SIGTERM}

	for _, ch := range chans {
		signal.Notify(ch, sigs...)
	}
}

func printHeader() {
	slug := fmt.Sprintf(slug, version)

	fmt.Fprintf(os.Stderr,
		"\033[34m%s%s\033[0m\n\n\n",
		banner,
		slug,
	)
}