package main

import (
	"bytes"
	"context"
	"flag"
	"fmt"
	"os"
	"runtime"
	"strings"
	"time"
	"vctp/db"
	"vctp/internal/report"
	"vctp/internal/secrets"
	"vctp/internal/settings"
	"vctp/internal/tasks"
	utils "vctp/internal/utils"
	"vctp/internal/vcenter"
	"vctp/log"
	"vctp/server"
	"vctp/server/router"

	"crypto/sha256"
	"log/slog"

	"github.com/go-co-op/gocron/v2"
)

var (
	bindDisableTls         bool
	sha1ver                string // sha1 revision used to build the program
	buildTime              string // when the executable was built
	cronSnapshotFrequency  time.Duration
	cronAggregateFrequency time.Duration
)

const (
	encryptedVcenterPasswordPrefix = "enc:v1:"
	legacyFallbackEncryptionKey    = "5L1l3B5KvwOCzUHMAlCgsgUTRAYMfSpa"
)

func main() {
	settingsPath := flag.String("settings", "/etc/dtms/vctp.yml", "Path to settings YAML")
	runInventory := flag.Bool("run-inventory", false, "Run a single inventory snapshot across all configured vCenters and exit")
	dbCleanup := flag.Bool("db-cleanup", false, "Run a one-time cleanup to drop low-value hourly snapshot indexes and exit")
	backfillVcenterCache := flag.Bool("backfill-vcenter-cache", false, "Run a one-time backfill for vcenter latest+aggregate cache tables and exit")
	importSQLite := flag.String("import-sqlite", "", "Import a SQLite database file/DSN into the configured Postgres database and exit")
	flag.Parse()

	bootstrapLogger := log.New(log.LevelInfo, log.OutputText)

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

	// Load settings from yaml
	s := settings.New(bootstrapLogger, *settingsPath)
	err := s.ReadYMLSettings()
	if err != nil {
		bootstrapLogger.Error("failed to open yaml settings file", "error", err, "filename", *settingsPath)
		os.Exit(1)
	}

	logger := log.New(
		log.ToLevel(strings.ToLower(strings.TrimSpace(s.Values.Settings.LogLevel))),
		log.ToOutput(strings.ToLower(strings.TrimSpace(s.Values.Settings.LogOutput))),
	)
	s.Logger = logger

	logger.Info("vCTP starting", "build_time", buildTime, "sha1_version", sha1ver, "go_version", runtime.Version(), "settings_file", *settingsPath)
	warnDeprecatedPollingSettings(logger, s.Values)

	// Configure database
	dbURL := strings.TrimSpace(s.Values.Settings.DatabaseURL)
	normalizedDriver, inferredFromDSN, err := db.ResolveDriver(s.Values.Settings.DatabaseDriver, dbURL)
	if err != nil {
		logger.Error("Invalid database configuration", "error", err)
		os.Exit(1)
	}
	if inferredFromDSN {
		logger.Warn("database_driver is unset; inferred postgres from database_url")
	}
	if dbURL == "" && normalizedDriver == "sqlite" {
		dbURL = utils.GetFilePath("db.sqlite3")
	}
	logger.Info("Effective database driver resolved", "driver", normalizedDriver)

	database, err := db.New(logger, db.Config{
		Driver:                     normalizedDriver,
		DSN:                        dbURL,
		EnableExperimentalPostgres: s.Values.Settings.EnableExperimentalPostgres,
	})
	if err != nil {
		logger.Error("Failed to create database", "error", err)
		os.Exit(1)
	}
	defer database.Close()
	//defer database.DB().Close()

	if err = db.Migrate(database, normalizedDriver); err != nil {
		logger.Error("failed to migrate database", "error", err)
		os.Exit(1)
	}
	if strings.TrimSpace(*importSQLite) != "" {
		if normalizedDriver != "postgres" {
			logger.Error("sqlite import requires settings.database_driver=postgres")
			os.Exit(1)
		}
		logger.Info("starting one-time sqlite import into postgres", "sqlite_source", strings.TrimSpace(*importSQLite))
		stats, err := db.ImportSQLiteIntoPostgres(ctx, logger, database.DB(), strings.TrimSpace(*importSQLite))
		if err != nil {
			logger.Error("failed to import sqlite database into postgres", "error", err)
			os.Exit(1)
		}
		logger.Info("completed sqlite import into postgres",
			"sqlite_source", stats.SourceDSN,
			"tables_imported", stats.TablesImported,
			"tables_skipped", stats.TablesSkipped,
			"rows_imported", stats.RowsImported,
		)
		return
	}
	if *dbCleanup {
		dropped, err := db.CleanupHourlySnapshotIndexes(ctx, database.DB())
		if err != nil {
			logger.Error("failed to cleanup hourly snapshot indexes", "error", err)
			os.Exit(1)
		}
		logger.Info("completed hourly snapshot index cleanup", "indexes_dropped", dropped)
		return
	}
	if *backfillVcenterCache {
		logger.Info("starting one-time vcenter cache backfill")
		if err := report.EnsureSnapshotRegistry(ctx, database); err != nil {
			logger.Error("failed to ensure snapshot registry", "error", err)
			os.Exit(1)
		}
		hourlyRecords, err := report.ListSnapshots(ctx, database, "hourly")
		if err != nil {
			logger.Error("failed to list hourly snapshots from registry", "error", err)
			os.Exit(1)
		}
		if len(hourlyRecords) == 0 {
			logger.Warn("snapshot registry has no hourly entries; attempting registry migration before cache backfill")
			stats, err := report.MigrateSnapshotRegistry(ctx, database)
			if err != nil {
				logger.Error("failed to migrate snapshot registry before cache backfill", "error", err)
				os.Exit(1)
			}
			logger.Info("snapshot registry migration complete",
				"hourly_renamed", stats.HourlyRenamed,
				"hourly_registered", stats.HourlyRegistered,
				"daily_registered", stats.DailyRegistered,
				"monthly_registered", stats.MonthlyRegistered,
			)
		}

		if err := db.SyncVcenterTotalsFromSnapshots(ctx, database.DB()); err != nil {
			logger.Error("failed to backfill hourly vcenter totals cache", "error", err)
			os.Exit(1)
		}
		latestSynced, err := db.SyncVcenterLatestTotalsFromHistory(ctx, database.DB())
		if err != nil {
			logger.Error("failed to backfill latest vcenter totals cache", "error", err)
			os.Exit(1)
		}

		dailySnapshots, dailyRows, dailyErr := db.SyncVcenterAggregateTotalsFromRegistry(ctx, database.DB(), "daily")
		if dailyErr != nil {
			logger.Warn("daily vcenter aggregate cache backfill completed with warnings", "error", dailyErr)
		}
		monthlySnapshots, monthlyRows, monthlyErr := db.SyncVcenterAggregateTotalsFromRegistry(ctx, database.DB(), "monthly")
		if monthlyErr != nil {
			logger.Warn("monthly vcenter aggregate cache backfill completed with warnings", "error", monthlyErr)
		}

		logger.Info("completed one-time vcenter cache backfill",
			"latest_rows_synced", latestSynced,
			"daily_snapshots_refreshed", dailySnapshots,
			"daily_rows_upserted", dailyRows,
			"monthly_snapshots_refreshed", monthlySnapshots,
			"monthly_rows_upserted", monthlyRows,
		)
		return
	}

	// Determine bind IP
	bindIP := strings.TrimSpace(s.Values.Settings.BindIP)
	if bindIP == "" {
		bindIP = utils.GetOutboundIP().String()
	}
	// Determine bind port
	bindPort := s.Values.Settings.BindPort
	if bindPort == 0 {
		bindPort = 9443
	}
	bindAddress := fmt.Sprint(bindIP, ":", bindPort)
	//logger.Info("Will listen on address", "ip", bindIP, "port", bindPort)

	// Determine bind disable TLS
	bindDisableTls = s.Values.Settings.BindDisableTLS

	// Get file names for TLS cert/key
	tlsCertFilename := strings.TrimSpace(s.Values.Settings.TLSCertFilename)
	if tlsCertFilename != "" {
		tlsCertFilename = utils.GetFilePath(tlsCertFilename)
	} else {
		tlsCertFilename = "./cert.pem"
	}

	tlsKeyFilename := strings.TrimSpace(s.Values.Settings.TLSKeyFilename)
	if tlsKeyFilename != "" {
		tlsKeyFilename = utils.GetFilePath(tlsKeyFilename)
	} else {
		tlsKeyFilename = "./privkey.pem"
	}

	// Generate certificate if required
	if !(utils.FileExists(tlsCertFilename) && utils.FileExists(tlsKeyFilename)) {
		logger.Warn("Specified TLS certificate or private key do not exist", "certificate", tlsCertFilename, "tls-key", tlsKeyFilename)
		if err := utils.GenerateCerts(tlsCertFilename, tlsKeyFilename); err != nil {
			logger.Error("failed to generate TLS cert/key", "error", err)
			os.Exit(1)
		}
	}

	// Load vcenter credentials from settings, decrypt if required.
	encKey := deriveEncryptionKey(logger, *settingsPath, s.Values.Settings.EncryptionKey)
	a := secrets.New(logger, encKey)
	legacyDecryptKeys := deriveLegacyDecryptionKeys(*settingsPath, encKey)
	vcEp := strings.TrimSpace(s.Values.Settings.VcenterPassword)
	if len(vcEp) == 0 {
		logger.Error("No vcenter password configured")
		os.Exit(1)
	}
	vcPass, rewrittenCredential, err := resolveVcenterPassword(logger, a, legacyDecryptKeys, vcEp)
	if err != nil {
		logger.Error("failed to resolve vcenter credentials", "error", err)
		os.Exit(1)
	}
	if rewrittenCredential != "" && rewrittenCredential != vcEp {
		s.Values.Settings.VcenterPassword = rewrittenCredential
		if err := s.WriteYMLSettings(); err != nil {
			logger.Warn("failed to update settings with encrypted vcenter password", "error", err)
		} else {
			if strings.HasPrefix(vcEp, encryptedVcenterPasswordPrefix) {
				logger.Info("rewrote vcenter password with refreshed encryption format")
			} else {
				logger.Info("encrypted vcenter password stored in settings file")
			}
		}
	}

	creds := vcenter.VcenterLogin{
		Username: strings.TrimSpace(s.Values.Settings.VcenterUsername),
		Password: string(vcPass),
		Insecure: s.Values.Settings.VcenterInsecure,
	}
	if creds.Username == "" {
		logger.Error("No vcenter username configured")
		os.Exit(1)
	}

	// Set a recognizable User-Agent for vCenter sessions.
	ua := "vCTP"
	if sha1ver != "" {
		ua = fmt.Sprintf("vCTP/%s", sha1ver)
	}
	vcenter.SetUserAgent(ua)

	// Prepare the task scheduler
	c, err := gocron.NewScheduler()
	if err != nil {
		logger.Error("failed to create scheduler", "error", err)
		os.Exit(1)
	}

	// Pass useful information to the cron jobs
	ct := &tasks.CronTask{
		Logger:                   logger,
		Database:                 database,
		Settings:                 s,
		VcCreds:                  &creds,
		FirstHourlySnapshotCheck: true,
	}

	// One-shot mode: run a single inventory snapshot across all configured vCenters and exit.
	if *runInventory {
		logger.Info("Running one-shot inventory snapshot across all vCenters")
		if err := ct.RunVcenterSnapshotHourly(ctx, logger, true); err != nil {
			logger.Error("One-shot inventory snapshot failed", "error", err)
			os.Exit(1)
		}
		logger.Info("One-shot inventory snapshot complete; exiting")
		return
	}

	cronSnapshotFrequency = durationFromSeconds(s.Values.Settings.VcenterInventorySnapshotSeconds, 3600)
	logger.Debug("Setting VM inventory snapshot cronjob frequency to", "frequency", cronSnapshotFrequency)

	cronAggregateFrequency = durationFromSeconds(s.Values.Settings.VcenterInventoryAggregateSeconds, 86400)
	logger.Debug("Setting VM inventory daily aggregation cronjob frequency to", "frequency", cronAggregateFrequency)

	startsAt3 := alignStart(time.Now(), cronSnapshotFrequency)
	job3, err := c.NewJob(
		gocron.DurationJob(cronSnapshotFrequency),
		gocron.NewTask(func() {
			ct.RunVcenterSnapshotHourly(ctx, logger, false)
		}), gocron.WithSingletonMode(gocron.LimitModeReschedule),
		gocron.WithStartAt(gocron.WithStartDateTime(startsAt3)),
	)
	if err != nil {
		logger.Error("failed to start vcenter inventory snapshot cron job", "error", err)
		os.Exit(1)
	}
	logger.Debug("Created vcenter inventory snapshot cron job", "job", job3.ID(), "starting_at", startsAt3)

	startsAt4 := time.Now().Add(cronAggregateFrequency)
	if cronAggregateFrequency == time.Hour*24 {
		now := time.Now()
		startsAt4 = time.Date(now.Year(), now.Month(), now.Day()+1, 0, 10, 0, 0, now.Location())
	}
	job4, err := c.NewJob(
		gocron.DurationJob(cronAggregateFrequency),
		gocron.NewTask(func() {
			ct.RunVcenterDailyAggregate(ctx, logger)
		}), gocron.WithSingletonMode(gocron.LimitModeReschedule),
		gocron.WithStartAt(gocron.WithStartDateTime(startsAt4)),
	)
	if err != nil {
		logger.Error("failed to start vcenter inventory aggregation cron job", "error", err)
		os.Exit(1)
	}
	logger.Debug("Created vcenter inventory aggregation cron job", "job", job4.ID(), "starting_at", startsAt4)

	monthlyCron := strings.TrimSpace(s.Values.Settings.MonthlyAggregationCron)
	if monthlyCron == "" {
		monthlyCron = "10 3 1 * *"
	}
	logger.Debug("Setting monthly aggregation cron schedule", "cron", monthlyCron)
	job5, err := c.NewJob(
		gocron.CronJob(monthlyCron, false),
		gocron.NewTask(func() {
			ct.RunVcenterMonthlyAggregate(ctx, logger)
		}), gocron.WithSingletonMode(gocron.LimitModeReschedule),
	)
	if err != nil {
		logger.Error("failed to start vcenter monthly aggregation cron job", "error", err)
		os.Exit(1)
	}
	logger.Debug("Created vcenter monthly aggregation cron job", "job", job5.ID())

	snapshotCleanupCron := strings.TrimSpace(s.Values.Settings.SnapshotCleanupCron)
	if snapshotCleanupCron == "" {
		snapshotCleanupCron = "30 2 * * *"
	}
	job6, err := c.NewJob(
		gocron.CronJob(snapshotCleanupCron, false),
		gocron.NewTask(func() {
			ct.RunSnapshotCleanup(ctx, logger)
			if normalizedDriver == "sqlite" {
				logger.Info("Performing sqlite VACUUM after snapshot cleanup")
				if _, err := ct.Database.DB().ExecContext(ctx, "VACUUM"); err != nil {
					logger.Warn("VACUUM failed after snapshot cleanup", "error", err)
				} else {
					logger.Debug("VACUUM completed after snapshot cleanup")
				}
			}
		}), gocron.WithSingletonMode(gocron.LimitModeReschedule),
	)
	if err != nil {
		logger.Error("failed to start snapshot cleanup cron job", "error", err)
		os.Exit(1)
	}
	logger.Debug("Created snapshot cleanup cron job", "job", job6.ID())

	// Retry failed hourly snapshots
	retrySeconds := s.Values.Settings.HourlySnapshotRetrySeconds
	if retrySeconds <= 0 {
		retrySeconds = 300
	}
	job7, err := c.NewJob(
		gocron.DurationJob(time.Duration(retrySeconds)*time.Second),
		gocron.NewTask(func() {
			ct.RunHourlySnapshotRetry(ctx, logger)
		}), gocron.WithSingletonMode(gocron.LimitModeReschedule),
	)
	if err != nil {
		logger.Error("failed to start hourly snapshot retry cron job", "error", err)
		os.Exit(1)
	}
	logger.Debug("Created hourly snapshot retry cron job", "job", job7.ID(), "interval_seconds", retrySeconds)

	// start cron scheduler
	c.Start()

	// Start server
	r := router.New(logger, database, buildTime, sha1ver, runtime.Version(), &creds, a, s)
	svr := server.New(
		logger,
		c,
		cancel,
		bindAddress,
		server.WithRouter(r),
		server.SetTls(bindDisableTls),
		server.SetCertificate(tlsCertFilename),
		server.SetPrivateKey(tlsKeyFilename),
	)
	//logger.Debug("Server configured", "object", svr)

	if err := svr.StartAndWait(); err != nil {
		logger.Error("server terminated with error", "error", err)
		os.Exit(1)
	}

	os.Exit(0)
}

// alignStart snaps the first run to a sensible boundary (hour or 15-minute block) when possible.
func alignStart(now time.Time, freq time.Duration) time.Time {
	if freq == time.Hour {
		return now.Truncate(time.Hour).Add(time.Hour)
	}
	quarter := 15 * time.Minute
	if freq%quarter == 0 {
		return now.Truncate(quarter).Add(quarter)
	}
	return now.Add(freq)
}

func warnDeprecatedPollingSettings(logger *slog.Logger, cfg *settings.SettingsYML) {
	if cfg == nil {
		return
	}
	if cfg.Settings.VcenterEventPollingSeconds > 0 {
		logger.Warn("vcenter_event_polling_seconds is deprecated and ignored; snapshot lifecycle processing is used instead",
			"value", cfg.Settings.VcenterEventPollingSeconds,
		)
	}
	if cfg.Settings.VcenterInventoryPollingSeconds > 0 {
		logger.Warn("vcenter_inventory_polling_seconds is deprecated and ignored; hourly snapshot jobs are used instead",
			"value", cfg.Settings.VcenterInventoryPollingSeconds,
		)
	}
}

func durationFromSeconds(value int, fallback int) time.Duration {
	if value <= 0 {
		return time.Second * time.Duration(fallback)
	}
	return time.Second * time.Duration(value)
}

func resolveVcenterPassword(logger *slog.Logger, cipher *secrets.Secrets, legacyDecryptKeys [][]byte, raw string) ([]byte, string, error) {
	if strings.TrimSpace(raw) == "" {
		return nil, "", fmt.Errorf("vcenter password is empty")
	}

	// New format: explicit prefix so we can distinguish ciphertext from plaintext safely.
	if after, ok := strings.CutPrefix(raw, encryptedVcenterPasswordPrefix); ok {
		enc := after
		pass, usedLegacyKey, err := decryptVcenterPasswordWithFallback(logger, cipher, legacyDecryptKeys, enc)
		if err != nil {
			return nil, "", fmt.Errorf("prefixed password decrypt failed: %w", err)
		}
		if usedLegacyKey {
			rewrite, rewriteErr := encryptWithPrefix(cipher, pass)
			if rewriteErr != nil {
				logger.Warn("failed to refresh prefixed vcenter password after fallback decrypt", "error", rewriteErr)
				return pass, "", nil
			}
			logger.Info("rewrote prefixed vcenter password using active encryption key")
			return pass, rewrite, nil
		}
		return pass, "", nil
	}

	// Backward compatibility: existing deployments may have unprefixed ciphertext.
	if pass, _, err := decryptVcenterPasswordWithFallback(logger, cipher, legacyDecryptKeys, raw); err == nil {
		rewrite, rewriteErr := encryptWithPrefix(cipher, pass)
		if rewriteErr != nil {
			logger.Warn("failed to re-encrypt legacy vcenter password with prefix", "error", rewriteErr)
			return pass, "", nil
		}
		return pass, rewrite, nil
	} else {
		// If decrypt fails and the input is non-trivial, treat it as plaintext and auto-encrypt.
		if len(raw) <= 2 {
			return nil, "", fmt.Errorf("vcenter password too short to auto-encrypt")
		}
		logger.Warn("unable to decrypt unprefixed vcenter password; treating value as plaintext", "error", err)
		rewrite, rewriteErr := encryptWithPrefix(cipher, []byte(raw))
		if rewriteErr != nil {
			return nil, "", fmt.Errorf("failed to encrypt plaintext vcenter password: %w", rewriteErr)
		}
		return []byte(raw), rewrite, nil
	}
}

func decryptVcenterPasswordWithFallback(logger *slog.Logger, cipher *secrets.Secrets, legacyDecryptKeys [][]byte, encrypted string) ([]byte, bool, error) {
	pass, err := cipher.Decrypt(encrypted)
	if err == nil {
		return pass, false, nil
	}
	primaryErr := err
	for _, key := range legacyDecryptKeys {
		candidate := secrets.New(logger, key)
		pass, decErr := candidate.Decrypt(encrypted)
		if decErr == nil {
			return pass, true, nil
		}
	}
	return nil, false, primaryErr
}

func encryptWithPrefix(cipher *secrets.Secrets, plain []byte) (string, error) {
	enc, encErr := cipher.Encrypt(plain)
	if encErr != nil {
		return "", encErr
	}
	return encryptedVcenterPasswordPrefix + enc, nil
}

func deriveLegacyDecryptionKeys(settingsPath string, activeKey []byte) [][]byte {
	legacyKeys := make([][]byte, 0, 2)
	addCandidate := func(candidate []byte) {
		if len(candidate) == 0 || bytes.Equal(candidate, activeKey) {
			return
		}
		for _, existing := range legacyKeys {
			if bytes.Equal(existing, candidate) {
				return
			}
		}
		keyCopy := make([]byte, len(candidate))
		copy(keyCopy, candidate)
		legacyKeys = append(legacyKeys, keyCopy)
	}

	platformKey, _ := deriveHostKeyCandidate(settingsPath)
	addCandidate(platformKey)
	addCandidate([]byte(legacyFallbackEncryptionKey))

	return legacyKeys
}

func deriveEncryptionKey(logger *slog.Logger, settingsPath string, configuredKey string) []byte {
	if provided := strings.TrimSpace(configuredKey); provided != "" {
		sum := sha256.Sum256([]byte(provided))
		logger.Debug("derived encryption key from settings", "setting", "settings.encryption_key")
		return sum[:]
	}

	key, source := deriveHostKeyCandidate(settingsPath)
	switch source {
	case "bios-uuid":
		logger.Debug("derived encryption key from BIOS UUID")
	case "machine-id":
		logger.Debug("derived encryption key from machine-id")
	default:
		logger.Warn("using host-derived encryption key fallback; set settings.encryption_key for an explicit key")
	}
	return key
}

func deriveHostKeyCandidate(settingsPath string) ([]byte, string) {
	if runtime.GOOS == "linux" {
		if data, err := os.ReadFile("/sys/class/dmi/id/product_uuid"); err == nil {
			src := strings.TrimSpace(string(data))
			if src != "" {
				sum := sha256.Sum256([]byte(src))
				return sum[:], "bios-uuid"
			}
		}
		if data, err := os.ReadFile("/etc/machine-id"); err == nil {
			src := strings.TrimSpace(string(data))
			if src != "" {
				sum := sha256.Sum256([]byte(src))
				return sum[:], "machine-id"
			}
		}
	}

	hostname, err := os.Hostname()
	if err != nil {
		hostname = "unknown-host"
	}
	src := strings.Join([]string{"vctp", runtime.GOOS, strings.TrimSpace(hostname), strings.TrimSpace(settingsPath)}, "|")
	sum := sha256.Sum256([]byte(src))
	return sum[:], "host-derived"
}