package main

import (
	"context"
	"flag"
	"fmt"
	"log"

	"github.com/aws/aws-sdk-go/aws"
	awscreds "github.com/aws/aws-sdk-go/aws/credentials"
	awssession "github.com/aws/aws-sdk-go/aws/session"
	"github.com/go-stomp/stomp/v3"
	pgx "github.com/jackc/pgx/v4"
	"github.com/jlaffaye/ftp"
	"gocloud.dev/blob"
	"gocloud.dev/blob/s3blob"
	"hg.lukegb.com/lukegb/depot/go/trains/darwin"
	"hg.lukegb.com/lukegb/depot/go/trains/darwin/darwindb"
	"hg.lukegb.com/lukegb/depot/go/trains/darwin/darwingest"
	"hg.lukegb.com/lukegb/depot/go/trains/darwin/darwingest/darwingeststomp"
)

var (
	cleanStart = flag.Bool("clean_start", false, "Start by downloading all timetabling and reference data and restart from snapshot")

	awsAccessKey    = requiredString("s3_access_key", "Darwin XML timetable S3 access key")
	awsAccessSecret = requiredString("s3_access_secret", "Darwin XML timetable S3 access secret")
	awsBucket       = flag.String("s3_bucket", "darwin.xmltimetable", "Darwin XML timetable S3 bucket")
	awsPrefix       = flag.String("s3_prefix", "PPTimetable/", "Darwin XML timetable S3 bucket key prefix")

	postgresString = flag.String("pg_string", "host=/var/run/postgresql database=trains search_path=darwindb", "String to connect to PG")

	stompHostport = requiredString("stomp_address", "Darwin STOMP address (host:port)")
	stompUsername = requiredString("stomp_username", "Darwin STOMP username")
	stompPassword = requiredString("stomp_password", "Darwin STOMP password")
	stompClientID = requiredString("stomp_client_id", "Darwin STOMP client ID")
	stompTopic    = flag.String("stomp_topic", "/topic/darwin.pushport-v16", "Darwin STOMP topic")

	ftpHostport = requiredString("ftp_address", "Darwin FTP address (host:port)")
	ftpUsername = requiredString("ftp_username", "Darwin FTP username")
	ftpPassword = requiredString("ftp_password", "Darwin FTP password")

	requiredFlags []string
)

func requiredString(name, descr string) *string {
	requireFlag(name)
	return flag.String(name, "", descr)
}

func requireFlag(names ...string) {
	requiredFlags = append(requiredFlags, names...)
}

func checkRequiredFlags() {
	for _, fname := range requiredFlags {
		f := flag.CommandLine.Lookup(fname)
		if f == nil {
			log.Fatalf("required flag %q doesn't actually exist", fname)
		}
		v := f.Value.(flag.Getter).Get()
		if v == nil {
			log.Fatalf("required flag %q not set", fname)
		}
		if v, ok := v.(string); ok && v == "" {
			log.Fatalf("required flag %q not set or empty", fname)
		}
	}
}

func main() {
	flag.Parse()
	checkRequiredFlags()

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	awsSess, err := awssession.NewSession(&aws.Config{
		Region:      aws.String("eu-west-1"),
		Credentials: awscreds.NewStaticCredentials(*awsAccessKey, *awsAccessSecret, ""),
	})
	if err != nil {
		log.Fatalf("awssession.NewSession: %w", err)
	}
	s3Bucket, err := s3blob.OpenBucket(ctx, awsSess, *awsBucket, nil)
	if err != nil {
		log.Fatalf("s3blob.OpenBucket: %w", err)
	}
	defer s3Bucket.Close()

	bucket := blob.PrefixedBucket(s3Bucket, *awsPrefix)
	defer bucket.Close()

	pc, err := pgx.Connect(ctx, *postgresString)
	if err != nil {
		log.Fatalf("pgx.Connect: %v", err)
	}
	defer pc.Close(context.Background())

	catchupTx, err := pc.Begin(ctx)
	if err != nil {
		log.Fatalf("beginning catchup transaction: %v", err)
	}
	catchupAffected := darwindb.NewAffected()

	gimmeTransaction := func(ctx context.Context, cb func(ctx context.Context, tx pgx.Tx) error) error {
		if catchupTx != nil {
			return cb(ctx, catchupTx)
		}

		tx, err := pc.Begin(ctx)
		if err != nil {
			return fmt.Errorf("starting transaction: %w", err)
		}
		defer tx.Rollback(ctx)

		if err := cb(ctx, tx); err != nil {
			return err
		}

		return tx.Commit(ctx)
	}
	notify := func(ctx context.Context, tx pgx.Tx, s string) error {
		if _, err := tx.Exec(ctx, fmt.Sprintf("NOTIFY %q", s)); err != nil {
			return fmt.Errorf("notifying channel for %q: %w", s, err)
		}
		if _, err := tx.Exec(ctx, fmt.Sprintf("NOTIFY \"firehose\", '%s'", s)); err != nil {
			return fmt.Errorf("notifying firehose for %q: %w", s, err)
		}
		return nil
	}
	sendAffectedNotifications := func(ctx context.Context, tx pgx.Tx, affected *darwindb.Affected) error {
		for tsid := range affected.TSIDs {
			if err := notify(ctx, tx, fmt.Sprintf("tsid-%d", tsid)); err != nil {
				return fmt.Errorf("notifying channel for tsid %d: %w", tsid, err)
			}
		}
		for tiploc := range affected.TIPLOCs {
			if err := notify(ctx, tx, fmt.Sprintf("tiploc-%s", tiploc)); err != nil {
				return fmt.Errorf("notifying channel for tiploc %s: %w", tiploc, err)
			}
		}
		return nil
	}
	processMessage := func(ctx context.Context, pp *darwin.PushPort) error {
		return gimmeTransaction(ctx, func(ctx context.Context, tx pgx.Tx) error {
			affected := catchupAffected
			sendAffected := false
			if affected == nil {
				affected = darwindb.NewAffected()
				sendAffected = true
			}
			if err := darwindb.Process(ctx, tx, pp, affected); err != nil {
				return fmt.Errorf("darwindb.Process: %w", err)
			}
			if sendAffected {
				return sendAffectedNotifications(ctx, tx, affected)
			}
			return nil
		})
	}

	cfg := darwingest.Config{
		Verbose: true,
		DialStomp: func(ctx context.Context) (*stomp.Conn, error) {
			return darwingeststomp.Dial(ctx, darwingeststomp.Config{
				Hostname: *stompHostport,
				Username: *stompUsername,
				Password: *stompPassword,
				ClientID: *stompClientID,
			})
		},
		StompSubscribe: func(ctx context.Context, c *stomp.Conn) (*stomp.Subscription, error) {
			return c.Subscribe(*stompTopic, stomp.AckClientIndividual)
		},
		DialFTP: func(ctx context.Context) (*ftp.ServerConn, error) {
			sc, err := ftp.Dial(*ftpHostport, ftp.DialWithContext(ctx))
			if err != nil {
				return nil, fmt.Errorf("ftp.Dial: %w", err)
			}

			if err := sc.Login(*ftpUsername, *ftpPassword); err != nil {
				sc.Quit()
				return nil, fmt.Errorf("ftp.ServerConn.Login: %w", err)
			}
			return sc, nil
		},

		Timetable: func(ppt *darwin.PushPortTimetable) error {
			return gimmeTransaction(ctx, func(ctx context.Context, tx pgx.Tx) error {
				if err := darwindb.ProcessTimetable(ctx, tx, ppt, catchupAffected); err != nil {
					return fmt.Errorf("processing timetable data: %w", err)
				}
				return nil
			})
		},
		ReferenceData: func(pprd *darwin.PushPortReferenceData) error {
			return gimmeTransaction(ctx, func(ctx context.Context, tx pgx.Tx) error {
				if err := darwindb.ProcessReferenceData(ctx, tx, pprd, catchupAffected); err != nil {
					return fmt.Errorf("processing reference data: %w", err)
				}
				return nil
			})
		},
		MessageCatchUp: func(pp *darwin.PushPort) error {
			return processMessage(ctx, pp)
		},
		CatchUpComplete: func(ctx context.Context) error {
			log.Printf("catchup affected: %v", catchupAffected.Summary())
			if err := sendAffectedNotifications(ctx, catchupTx, catchupAffected); err != nil {
				return fmt.Errorf("sending affected notifications: %v", err)
			}
			if err := catchupTx.Commit(ctx); err != nil {
				return fmt.Errorf("committing catchup transaction: %v", err)
			}
			catchupAffected = nil
			catchupTx = nil
			return nil
		},
		Message: func(pp *darwin.PushPort) error {
			return processMessage(ctx, pp)
		},
	}
	if *cleanStart {
		if err := darwingest.CatchUpAndStart(ctx, bucket, cfg); err != nil {
			log.Printf("CatchUpAndStart: %v", err)
		}
	} else {
		if err := darwingest.Start(ctx, bucket, cfg); err != nil {
			log.Printf("Start: %v", err)
		}
	}

	log.Println("terminating...")
}