package db

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"net/netip"
	"strings"
	"sync"
	"time"

	"github.com/glebarez/sqlite"
	"github.com/go-gormigrate/gormigrate/v2"
	"github.com/juanfont/headscale/hscontrol/notifier"
	"github.com/juanfont/headscale/hscontrol/types"
	"github.com/juanfont/headscale/hscontrol/util"
	"github.com/rs/zerolog/log"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

const (
	Postgres = "postgres"
	Sqlite   = "sqlite3"
)

var errDatabaseNotSupported = errors.New("database type not supported")

// KV is a key-value store in a psql table. For future use...
// TODO(kradalby): Is this used for anything?
type KV struct {
	Key   string
	Value string
}

type HSDatabase struct {
	db       *gorm.DB
	notifier *notifier.Notifier

	mu sync.RWMutex

	ipAllocationMutex sync.Mutex

	ipPrefixes []netip.Prefix
	baseDomain string
}

// TODO(kradalby): assemble this struct from toptions or something typed
// rather than arguments.
func NewHeadscaleDatabase(
	dbType, connectionAddr string,
	debug bool,
	notifier *notifier.Notifier,
	ipPrefixes []netip.Prefix,
	baseDomain string,
) (*HSDatabase, error) {
	dbConn, err := openDB(dbType, connectionAddr, debug)
	if err != nil {
		return nil, err
	}

	migrations := gormigrate.New(dbConn, gormigrate.DefaultOptions, []*gormigrate.Migration{
		// New migrations should be added as transactions at the end of this list.
		// The initial commit here is quite messy, completely out of order and
		// has no versioning and is the tech debt of not having versioned migrations
		// prior to this point. This first migration is all DB changes to bring a DB
		// up to 0.23.0.
		{
			ID: "202312101416",
			Migrate: func(tx *gorm.DB) error {
				if dbType == Postgres {
					tx.Exec(`create extension if not exists "uuid-ossp";`)
				}

				_ = tx.Migrator().RenameTable("namespaces", "users")

				// the big rename from Machine to Node
				_ = tx.Migrator().RenameTable("machines", "nodes")
				_ = tx.Migrator().RenameColumn(&types.Route{}, "machine_id", "node_id")

				err = tx.AutoMigrate(types.User{})
				if err != nil {
					return err
				}

				_ = tx.Migrator().RenameColumn(&types.Node{}, "namespace_id", "user_id")
				_ = tx.Migrator().RenameColumn(&types.PreAuthKey{}, "namespace_id", "user_id")

				_ = tx.Migrator().RenameColumn(&types.Node{}, "ip_address", "ip_addresses")
				_ = tx.Migrator().RenameColumn(&types.Node{}, "name", "hostname")

				// GivenName is used as the primary source of DNS names, make sure
				// the field is populated and normalized if it was not when the
				// node was registered.
				_ = tx.Migrator().RenameColumn(&types.Node{}, "nickname", "given_name")

				// If the Node table has a column for registered,
				// find all occourences of "false" and drop them. Then
				// remove the column.
				if tx.Migrator().HasColumn(&types.Node{}, "registered") {
					log.Info().
						Msg(`Database has legacy "registered" column in node, removing...`)

					nodes := types.Nodes{}
					if err := tx.Not("registered").Find(&nodes).Error; err != nil {
						log.Error().Err(err).Msg("Error accessing db")
					}

					for _, node := range nodes {
						log.Info().
							Str("node", node.Hostname).
							Str("machine_key", node.MachineKey.ShortString()).
							Msg("Deleting unregistered node")
						if err := tx.Delete(&types.Node{}, node.ID).Error; err != nil {
							log.Error().
								Err(err).
								Str("node", node.Hostname).
								Str("machine_key", node.MachineKey.ShortString()).
								Msg("Error deleting unregistered node")
						}
					}

					err := tx.Migrator().DropColumn(&types.Node{}, "registered")
					if err != nil {
						log.Error().Err(err).Msg("Error dropping registered column")
					}
				}

				err = tx.AutoMigrate(&types.Route{})
				if err != nil {
					return err
				}

				err = tx.AutoMigrate(&types.Node{})
				if err != nil {
					return err
				}

				// Ensure all keys have correct prefixes
				// https://github.com/tailscale/tailscale/blob/main/types/key/node.go#L35
				type result struct {
					ID         uint64
					MachineKey string
					NodeKey    string
					DiscoKey   string
				}
				var results []result
				err = tx.Raw("SELECT id, node_key, machine_key, disco_key FROM nodes").Find(&results).Error
				if err != nil {
					return err
				}

				for _, node := range results {
					mKey := node.MachineKey
					if !strings.HasPrefix(node.MachineKey, "mkey:") {
						mKey = "mkey:" + node.MachineKey
					}
					nKey := node.NodeKey
					if !strings.HasPrefix(node.NodeKey, "nodekey:") {
						nKey = "nodekey:" + node.NodeKey
					}

					dKey := node.DiscoKey
					if !strings.HasPrefix(node.DiscoKey, "discokey:") {
						dKey = "discokey:" + node.DiscoKey
					}

					err := tx.Exec(
						"UPDATE nodes SET machine_key = @mKey, node_key = @nKey, disco_key = @dKey WHERE ID = @id",
						sql.Named("mKey", mKey),
						sql.Named("nKey", nKey),
						sql.Named("dKey", dKey),
						sql.Named("id", node.ID),
					).Error
					if err != nil {
						return err
					}
				}

				if tx.Migrator().HasColumn(&types.Node{}, "enabled_routes") {
					log.Info().Msgf("Database has legacy enabled_routes column in node, migrating...")

					type NodeAux struct {
						ID            uint64
						EnabledRoutes types.IPPrefixes
					}

					nodesAux := []NodeAux{}
					err := tx.Table("nodes").Select("id, enabled_routes").Scan(&nodesAux).Error
					if err != nil {
						log.Fatal().Err(err).Msg("Error accessing db")
					}
					for _, node := range nodesAux {
						for _, prefix := range node.EnabledRoutes {
							if err != nil {
								log.Error().
									Err(err).
									Str("enabled_route", prefix.String()).
									Msg("Error parsing enabled_route")

								continue
							}

							err = tx.Preload("Node").
								Where("node_id = ? AND prefix = ?", node.ID, types.IPPrefix(prefix)).
								First(&types.Route{}).
								Error
							if err == nil {
								log.Info().
									Str("enabled_route", prefix.String()).
									Msg("Route already migrated to new table, skipping")

								continue
							}

							route := types.Route{
								NodeID:     node.ID,
								Advertised: true,
								Enabled:    true,
								Prefix:     types.IPPrefix(prefix),
							}
							if err := tx.Create(&route).Error; err != nil {
								log.Error().Err(err).Msg("Error creating route")
							} else {
								log.Info().
									Uint64("node_id", route.NodeID).
									Str("prefix", prefix.String()).
									Msg("Route migrated")
							}
						}
					}

					err = tx.Migrator().DropColumn(&types.Node{}, "enabled_routes")
					if err != nil {
						log.Error().Err(err).Msg("Error dropping enabled_routes column")
					}
				}

				if tx.Migrator().HasColumn(&types.Node{}, "given_name") {
					nodes := types.Nodes{}
					if err := tx.Find(&nodes).Error; err != nil {
						log.Error().Err(err).Msg("Error accessing db")
					}

					for item, node := range nodes {
						if node.GivenName == "" {
							normalizedHostname, err := util.NormalizeToFQDNRulesConfigFromViper(
								node.Hostname,
							)
							if err != nil {
								log.Error().
									Caller().
									Str("hostname", node.Hostname).
									Err(err).
									Msg("Failed to normalize node hostname in DB migration")
							}

							err = tx.Model(nodes[item]).Updates(types.Node{
								GivenName: normalizedHostname,
							}).Error
							if err != nil {
								log.Error().
									Caller().
									Str("hostname", node.Hostname).
									Err(err).
									Msg("Failed to save normalized node name in DB migration")
							}
						}
					}
				}

				err = tx.AutoMigrate(&KV{})
				if err != nil {
					return err
				}

				err = tx.AutoMigrate(&types.PreAuthKey{})
				if err != nil {
					return err
				}

				err = tx.AutoMigrate(&types.PreAuthKeyACLTag{})
				if err != nil {
					return err
				}

				_ = tx.Migrator().DropTable("shared_machines")

				err = tx.AutoMigrate(&types.APIKey{})
				if err != nil {
					return err
				}

				return nil
			},
			Rollback: func(tx *gorm.DB) error {
				return nil
			},
		},
		{
			// drop key-value table, it is not used, and has not contained
			// useful data for a long time or ever.
			ID: "202312101430",
			Migrate: func(tx *gorm.DB) error {
				return tx.Migrator().DropTable("kvs")
			},
			Rollback: func(tx *gorm.DB) error {
				return nil
			},
		},
	})

	if err = migrations.Migrate(); err != nil {
		log.Fatal().Err(err).Msgf("Migration failed: %v", err)
	}

	db := HSDatabase{
		db:       dbConn,
		notifier: notifier,

		ipPrefixes: ipPrefixes,
		baseDomain: baseDomain,
	}

	return &db, err
}

func openDB(dbType, connectionAddr string, debug bool) (*gorm.DB, error) {
	log.Debug().Str("type", dbType).Str("connection", connectionAddr).Msg("opening database")

	var dbLogger logger.Interface
	if debug {
		dbLogger = logger.Default
	} else {
		dbLogger = logger.Default.LogMode(logger.Silent)
	}

	switch dbType {
	case Sqlite:
		db, err := gorm.Open(
			sqlite.Open(connectionAddr+"?_synchronous=1&_journal_mode=WAL"),
			&gorm.Config{
				DisableForeignKeyConstraintWhenMigrating: true,
				Logger:                                   dbLogger,
			},
		)

		db.Exec("PRAGMA foreign_keys=ON")

		// The pure Go SQLite library does not handle locking in
		// the same way as the C based one and we cant use the gorm
		// connection pool as of 2022/02/23.
		sqlDB, _ := db.DB()
		sqlDB.SetMaxIdleConns(1)
		sqlDB.SetMaxOpenConns(1)
		sqlDB.SetConnMaxIdleTime(time.Hour)

		return db, err

	case Postgres:
		return gorm.Open(postgres.Open(connectionAddr), &gorm.Config{
			DisableForeignKeyConstraintWhenMigrating: true,
			Logger:                                   dbLogger,
		})
	}

	return nil, fmt.Errorf(
		"database of type %s is not supported: %w",
		dbType,
		errDatabaseNotSupported,
	)
}

func (hsdb *HSDatabase) PingDB(ctx context.Context) error {
	ctx, cancel := context.WithTimeout(ctx, time.Second)
	defer cancel()
	sqlDB, err := hsdb.db.DB()
	if err != nil {
		return err
	}

	return sqlDB.PingContext(ctx)
}

func (hsdb *HSDatabase) Close() error {
	db, err := hsdb.db.DB()
	if err != nil {
		return err
	}

	return db.Close()
}