package database

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"time"

	"github.com/matrix-org/go-neb/api"
	"github.com/matrix-org/go-neb/types"
	"maunium.net/go/mautrix/id"
)

// A ServiceDB stores the configuration for the services
type ServiceDB struct {
	db      *sql.DB
	dialect string
}

// A single global instance of the service DB.
var globalServiceDB Storer

// SetServiceDB sets the global service DB instance.
func SetServiceDB(db Storer) {
	globalServiceDB = db
}

// GetServiceDB gets the global service DB instance.
func GetServiceDB() Storer {
	return globalServiceDB
}

// Open a SQL database to use as a ServiceDB. This will automatically create
// the necessary database tables if they aren't already present.
func Open(databaseType, databaseURL string) (serviceDB *ServiceDB, err error) {
	db, err := sql.Open(databaseType, databaseURL)
	if err != nil {
		return
	}
	if _, err = db.Exec(schemaSQL); err != nil {
		return
	}
	if databaseType == "sqlite3" {
		// Fix for "database is locked" errors
		// https://github.com/mattn/go-sqlite3/issues/274
		db.SetMaxOpenConns(1)
	}
	serviceDB = &ServiceDB{db: db, dialect: databaseType}
	return
}

// StoreMatrixClientConfig stores the Matrix client config for a bot service.
// If a config already exists then it will be updated, otherwise a new config
// will be inserted. The previous config is returned.
func (d *ServiceDB) StoreMatrixClientConfig(config api.ClientConfig) (oldConfig api.ClientConfig, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		oldConfig, err = selectMatrixClientConfigTxn(txn, config.UserID)
		now := time.Now()
		if err == nil {
			return updateMatrixClientConfigTxn(txn, now, config)
		} else if err == sql.ErrNoRows {
			return insertMatrixClientConfigTxn(txn, now, config)
		} else {
			return err
		}
	})
	return
}

// LoadMatrixClientConfigs loads all Matrix client configs from the database.
func (d *ServiceDB) LoadMatrixClientConfigs() (configs []api.ClientConfig, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		configs, err = selectMatrixClientConfigsTxn(txn)
		return err
	})
	return
}

// LoadMatrixClientConfig loads a Matrix client config from the database.
// Returns sql.ErrNoRows if the client isn't in the database.
func (d *ServiceDB) LoadMatrixClientConfig(userID id.UserID) (config api.ClientConfig, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		config, err = selectMatrixClientConfigTxn(txn, userID)
		return err
	})
	return
}

// UpdateNextBatch updates the next_batch token for the given user.
func (d *ServiceDB) UpdateNextBatch(userID id.UserID, nextBatch string) (err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		return updateNextBatchTxn(txn, userID, nextBatch)
	})
	return
}

// LoadNextBatch loads the next_batch token for the given user.
func (d *ServiceDB) LoadNextBatch(userID id.UserID) (nextBatch string, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		nextBatch, err = selectNextBatchTxn(txn, userID)
		return err
	})
	return
}

// LoadService loads a service from the database.
// Returns sql.ErrNoRows if the service isn't in the database.
func (d *ServiceDB) LoadService(serviceID string) (service types.Service, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		service, err = selectServiceTxn(txn, serviceID)
		return err
	})
	return
}

// DeleteService deletes the given service from the database.
func (d *ServiceDB) DeleteService(serviceID string) (err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		return deleteServiceTxn(txn, serviceID)
	})
	return
}

// LoadServicesForUser loads all the bot services configured for a given user.
// Returns an empty list if there aren't any services configured.
func (d *ServiceDB) LoadServicesForUser(serviceUserID id.UserID) (services []types.Service, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		services, err = selectServicesForUserTxn(txn, serviceUserID)
		if err != nil {
			return err
		}
		return nil
	})
	return
}

// LoadServicesByType loads all the bot services configured for a given type.
// Returns an empty list if there aren't any services configured.
func (d *ServiceDB) LoadServicesByType(serviceType string) (services []types.Service, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		services, err = selectServicesByTypeTxn(txn, serviceType)
		if err != nil {
			return err
		}
		return nil
	})
	return
}

// StoreService stores a service into the database either by inserting a new
// service or updating an existing service. Returns the old service if there
// was one.
func (d *ServiceDB) StoreService(service types.Service) (oldService types.Service, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		oldService, err = selectServiceTxn(txn, service.ServiceID())
		if err == sql.ErrNoRows {
			return insertServiceTxn(txn, time.Now(), service)
		} else if err != nil {
			return err
		} else {
			return updateServiceTxn(txn, time.Now(), service)
		}
	})
	return
}

// LoadAuthRealm loads an AuthRealm from the database.
// Returns sql.ErrNoRows if the realm isn't in the database.
func (d *ServiceDB) LoadAuthRealm(realmID string) (realm types.AuthRealm, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		realm, err = selectRealmTxn(txn, realmID)
		return err
	})
	return
}

// LoadAuthRealmsByType loads all auth realms with the given type from the database.
// The realms are ordered based on their realm ID.
// Returns an empty list if there are no realms with that type.
func (d *ServiceDB) LoadAuthRealmsByType(realmType string) (realms []types.AuthRealm, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		realms, err = selectRealmsByTypeTxn(txn, realmType)
		return err
	})
	return
}

// StoreAuthRealm stores the given AuthRealm, clobbering based on the realm ID.
// This function updates the time added/updated values. The previous realm, if any, is
// returned.
func (d *ServiceDB) StoreAuthRealm(realm types.AuthRealm) (old types.AuthRealm, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		old, err = selectRealmTxn(txn, realm.ID())
		if err == sql.ErrNoRows {
			return insertRealmTxn(txn, time.Now(), realm)
		} else if err != nil {
			return err
		} else {
			return updateRealmTxn(txn, time.Now(), realm)
		}
	})
	return
}

// StoreAuthSession stores the given AuthSession, clobbering based on the tuple of
// user ID and realm ID. This function updates the time added/updated values.
// The previous session, if any, is returned.
func (d *ServiceDB) StoreAuthSession(session types.AuthSession) (old types.AuthSession, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		old, err = selectAuthSessionByUserTxn(txn, session.RealmID(), session.UserID())
		if err == sql.ErrNoRows {
			return insertAuthSessionTxn(txn, time.Now(), session)
		} else if err != nil {
			return err
		} else {
			return updateAuthSessionTxn(txn, time.Now(), session)
		}
	})
	return
}

// RemoveAuthSession removes the auth session for the given user on the given realm.
// No error is returned if the session did not exist in the first place.
func (d *ServiceDB) RemoveAuthSession(realmID string, userID id.UserID) error {
	return runTransaction(d.db, func(txn *sql.Tx) error {
		return deleteAuthSessionTxn(txn, realmID, userID)
	})
}

// LoadAuthSessionByUser loads an AuthSession from the database based on the given
// realm and user ID.
// Returns sql.ErrNoRows if the session isn't in the database.
func (d *ServiceDB) LoadAuthSessionByUser(realmID string, userID id.UserID) (session types.AuthSession, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		session, err = selectAuthSessionByUserTxn(txn, realmID, userID)
		return err
	})
	return
}

// LoadAuthSessionByID loads an AuthSession from the database based on the given
// realm and session ID.
// Returns sql.ErrNoRows if the session isn't in the database.
func (d *ServiceDB) LoadAuthSessionByID(realmID, sessionID string) (session types.AuthSession, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		session, err = selectAuthSessionByIDTxn(txn, realmID, sessionID)
		return err
	})
	return
}

// LoadBotOptions loads bot options from the database.
// Returns sql.ErrNoRows if the bot options isn't in the database.
func (d *ServiceDB) LoadBotOptions(userID id.UserID, roomID id.RoomID) (opts types.BotOptions, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		opts, err = selectBotOptionsTxn(txn, userID, roomID)
		return err
	})
	return
}

// StoreBotOptions stores a BotOptions into the database either by inserting a new
// bot options or updating an existing bot options. Returns the old bot options if there
// was one.
func (d *ServiceDB) StoreBotOptions(opts types.BotOptions) (oldOpts types.BotOptions, err error) {
	err = runTransaction(d.db, func(txn *sql.Tx) error {
		oldOpts, err = selectBotOptionsTxn(txn, opts.UserID, opts.RoomID)
		if err == sql.ErrNoRows {
			return insertBotOptionsTxn(txn, time.Now(), opts)
		} else if err != nil {
			return err
		} else {
			return updateBotOptionsTxn(txn, time.Now(), opts)
		}
	})
	return
}

// InsertFromConfig inserts entries from the config file into the database. This only really
// makes sense for in-memory databases.
func (d *ServiceDB) InsertFromConfig(cfg *api.ConfigFile) error {
	// Insert clients
	for _, cli := range cfg.Clients {
		if _, err := d.StoreMatrixClientConfig(cli); err != nil {
			return err
		}
	}

	// Keep a map of realms for inserting sessions
	realms := map[string]types.AuthRealm{} // by realm ID

	// Insert realms
	for _, r := range cfg.Realms {
		if err := r.Check(); err != nil {
			return err
		}
		realm, err := types.CreateAuthRealm(r.ID, r.Type, r.Config)
		if err != nil {
			return err
		}
		if _, err := d.StoreAuthRealm(realm); err != nil {
			return err
		}
		realms[realm.ID()] = realm
	}

	// Insert sessions
	for _, s := range cfg.Sessions {
		if err := s.Check(); err != nil {
			return err
		}
		r := realms[s.RealmID]
		if r == nil {
			return fmt.Errorf("Session %s specifies an unknown realm ID %s", s.SessionID, s.RealmID)
		}
		session := r.AuthSession(s.SessionID, s.UserID, s.RealmID)
		// dump the raw JSON config directly into the session. This is what
		// selectAuthSessionByUserTxn does.
		if err := json.Unmarshal(s.Config, session); err != nil {
			return err
		}
		if _, err := d.StoreAuthSession(session); err != nil {
			return err
		}
	}

	// Do not insert services yet, they require more work to set up.
	return nil
}

// GetSQLDb retrieves the SQL database instance of a ServiceDB and the dialect it uses (sqlite3 or postgres).
func (d *ServiceDB) GetSQLDb() (*sql.DB, string) {
	return d.db, d.dialect
}

func runTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
	txn, err := db.Begin()
	if err != nil {
		return
	}
	defer func() {
		if r := recover(); r != nil {
			txn.Rollback()
			panic(r)
		} else if err != nil {
			txn.Rollback()
		} else {
			err = txn.Commit()
		}
	}()
	err = fn(txn)
	return
}