package database

import (
	"context"
	"database/sql"
	"fmt"

	"github.com/ddworken/hishtory/shared"
	"github.com/jackc/pgx/v4/stdlib"
	_ "github.com/lib/pq"
	sqltrace "gopkg.in/DataDog/dd-trace-go.v1/contrib/database/sql"
	gormtrace "gopkg.in/DataDog/dd-trace-go.v1/contrib/gorm.io/gorm.v1"
	"gorm.io/driver/postgres"
	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
)

type DB struct {
	*gorm.DB
}

func OpenSQLite(dsn string, config *gorm.Config) (*DB, error) {
	db, err := gorm.Open(sqlite.Open(dsn), config)
	if err != nil {
		return nil, fmt.Errorf("gorm.Open: %w", err)
	}

	return &DB{db}, nil
}

func OpenPostgres(dsn string, config *gorm.Config) (*DB, error) {
	sqltrace.Register("pgx", &stdlib.Driver{}, sqltrace.WithServiceName("hishtory-api"))
	sqlDb, err := sqltrace.Open("pgx", dsn)
	if err != nil {
		return nil, fmt.Errorf("sqltrace.Open: %w", err)
	}
	db, err := gormtrace.Open(postgres.New(postgres.Config{Conn: sqlDb}), config)
	if err != nil {
		return nil, fmt.Errorf("gormtrace.Open: %w", err)
	}

	return &DB{db}, nil
}

func (db *DB) AddDatabaseTables() error {
	models := []any{
		&shared.EncHistoryEntry{},
		&shared.Device{},
		&shared.UsageData{},
		&shared.DumpRequest{},
		&shared.DeletionRequest{},
		&shared.Feedback{},
	}

	for _, model := range models {
		fmt.Printf("Beginning migration of %#v\n", model)
		if err := db.AutoMigrate(model); err != nil {
			return fmt.Errorf("db.AutoMigrate: %w", err)
		}
		fmt.Printf("Done migrating %#v\n", model)
	}

	return nil
}

func (db *DB) Close() error {
	rawDB, err := db.DB.DB()
	if err != nil {
		return fmt.Errorf("db.DB.DB: %w", err)
	}

	if err := rawDB.Close(); err != nil {
		return fmt.Errorf("rawDB.Close: %w", err)
	}

	return nil
}

func (db *DB) Ping() error {
	rawDB, err := db.DB.DB()
	if err != nil {
		return fmt.Errorf("db.DB.DB: %w", err)
	}

	if err := rawDB.Ping(); err != nil {
		return fmt.Errorf("rawDB.Ping: %w", err)
	}

	return nil
}

func (db *DB) SetMaxIdleConns(n int) error {
	rawDB, err := db.DB.DB()
	if err != nil {
		return err
	}

	rawDB.SetMaxIdleConns(n)

	return nil
}

func (db *DB) Stats() (sql.DBStats, error) {
	rawDB, err := db.DB.DB()
	if err != nil {
		return sql.DBStats{}, fmt.Errorf("db.DB.DB: %w", err)
	}

	return rawDB.Stats(), nil
}

func (db *DB) DistinctUsers(ctx context.Context) (int64, error) {
	row := db.WithContext(ctx).Raw("SELECT COUNT(DISTINCT devices.user_id) FROM devices").Row()
	var numDistinctUsers int64
	err := row.Scan(&numDistinctUsers)
	if err != nil {
		return 0, fmt.Errorf("row.Scan: %w", err)
	}

	return numDistinctUsers, nil
}

func (db *DB) DumpRequestCreate(ctx context.Context, req *shared.DumpRequest) error {
	tx := db.WithContext(ctx).Create(req)
	if tx.Error != nil {
		return fmt.Errorf("tx.Error: %w", tx.Error)
	}

	return nil
}

func (db *DB) DumpRequestForUserAndDevice(ctx context.Context, userID, deviceID string) ([]*shared.DumpRequest, error) {
	var dumpRequests []*shared.DumpRequest
	// Filter out ones requested by the hishtory instance that sent this request
	tx := db.WithContext(ctx).Where("user_id = ? AND requesting_device_id != ?", userID, deviceID).Find(&dumpRequests)
	if tx.Error != nil {
		return nil, fmt.Errorf("tx.Error: %w", tx.Error)
	}

	return dumpRequests, nil
}

func (db *DB) DumpRequestDeleteForUserAndDevice(ctx context.Context, userID, deviceID string) error {
	tx := db.WithContext(ctx).Delete(&shared.DumpRequest{}, "user_id = ? AND requesting_device_id = ?", userID, deviceID)
	if tx.Error != nil {
		return fmt.Errorf("tx.Error: %w", tx.Error)
	}

	return nil
}

func (db *DB) ApplyDeletionRequestsToBackend(ctx context.Context, request *shared.DeletionRequest) (int64, error) {
	tx := db.WithContext(ctx).Where("false")
	for _, message := range request.Messages.Ids {
		// Note that this won't do server-side deletion of pre-saved history entries. This is an inherent
		// limitation of our current DB schema. This is sub-par, since it means that even after deletion, clients
		// may still receive deleted history entries. But, a well-behaved client will immediately delete
		// these (never writing them to disk) and mark them as received, so this won't happen again.
		//
		// TODO: This could be improved upon if we added a HistoryEntry.EntryId field, backfilled it, added
		// it to EncHistoryEntry, and then used that as a key for deletion.
		tx = tx.Or(db.WithContext(ctx).Where("user_id = ? AND device_id = ? AND date = ?", request.UserId, message.DeviceId, message.EndTime))
	}
	result := tx.Delete(&shared.EncHistoryEntry{})
	if tx.Error != nil {
		return 0, fmt.Errorf("tx.Error: %w", tx.Error)
	}
	return result.RowsAffected, nil
}

func (db *DB) DeletionRequestInc(ctx context.Context, userID, deviceID string) error {
	tx := db.WithContext(ctx).Exec("UPDATE deletion_requests SET read_count = read_count + 1 WHERE user_id = ? AND destination_device_id = ?", userID, deviceID)
	if tx.Error != nil {
		return fmt.Errorf("tx.Error: %w", tx.Error)
	}

	return nil
}

func (db *DB) DeletionRequestsForUserAndDevice(ctx context.Context, userID, deviceID string) ([]*shared.DeletionRequest, error) {
	var deletionRequests []*shared.DeletionRequest
	tx := db.WithContext(ctx).Where("user_id = ? AND destination_device_id = ?", userID, deviceID).Find(&deletionRequests)
	if tx.Error != nil {
		return nil, fmt.Errorf("tx.Error: %w", tx.Error)
	}

	return deletionRequests, nil
}

func (db *DB) DeletionRequestCreate(ctx context.Context, request *shared.DeletionRequest) error {
	userID := request.UserId

	devices, err := db.DevicesForUser(ctx, userID)
	if err != nil {
		return fmt.Errorf("db.DevicesForUser: %w", err)
	}

	if len(devices) == 0 {
		return fmt.Errorf("found no devices associated with user_id=%s, can't save history entry", userID)
	}

	fmt.Printf("db.DeletionRequestCreate: Found %d devices\n", len(devices))

	// TODO: maybe this should be a transaction?
	for _, device := range devices {
		request.DestinationDeviceId = device.DeviceId
		tx := db.WithContext(ctx).Create(&request)
		if tx.Error != nil {
			return fmt.Errorf("tx.Error: %w", tx.Error)
		}
	}

	numDeleted, err := db.ApplyDeletionRequestsToBackend(ctx, request)
	if err != nil {
		return fmt.Errorf("db.ApplyDeletionRequestsToBackend: %w", err)
	}
	fmt.Printf("addDeletionRequestHandler: Deleted %d rows in the backend\n", numDeleted)

	return nil
}

func (db *DB) FeedbackCreate(ctx context.Context, feedback *shared.Feedback) error {
	tx := db.WithContext(ctx).Create(feedback)
	if tx.Error != nil {
		return fmt.Errorf("tx.Error: %w", tx.Error)
	}

	return nil
}

func (db *DB) Clean(ctx context.Context) error {
	r := db.WithContext(ctx).Exec("DELETE FROM enc_history_entries WHERE read_count > 10")
	if r.Error != nil {
		return r.Error
	}
	r = db.WithContext(ctx).Exec("DELETE FROM deletion_requests WHERE read_count > 1000")
	if r.Error != nil {
		return r.Error
	}

	return nil
}

func (db *DB) DeepClean(ctx context.Context) error {
	return db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		r := tx.Exec(`
		CREATE TEMP TABLE temp_users_with_one_device AS (
			SELECT user_id
			FROM devices
			GROUP BY user_id
			HAVING COUNT(DISTINCT device_id) > 1
		)	
		`)
		if r.Error != nil {
			return r.Error
		}
		r = tx.Exec(`
		CREATE TEMP TABLE temp_inactive_users AS (
			SELECT user_id
			FROM usage_data
			WHERE last_used <= (now() - INTERVAL '90 days')
		)	
		`)
		if r.Error != nil {
			return r.Error
		}
		r = tx.Exec(`
		SELECT COUNT(*) FROM enc_history_entries WHERE
			date <= (now() - INTERVAL '90 days')
			AND user_id IN (SELECT * FROM temp_users_with_one_device)
			AND user_id IN (SELECT * FROM temp_inactive_users)
		`)
		if r.Error != nil {
			return r.Error
		}
		fmt.Printf("Ran deep clean and deleted %d rows\n", r.RowsAffected)
		return nil
	})
}