package sqlite

import (
	"context"
	"database/sql"

	"github.com/pkg/errors"

	// Note: modernc.org/sqlite driver is imported in functions.go where
	// RegisterScalarFunction is used. No blank import needed here.

	"github.com/usememos/memos/internal/profile"
	"github.com/usememos/memos/store"
)

type DB struct {
	db      *sql.DB
	profile *profile.Profile
}

// NewDB opens a database specified by its database driver name and a
// driver-specific data source name, usually consisting of at least a
// database name and connection information.
func NewDB(profile *profile.Profile) (store.Driver, error) {
	// Ensure a DSN is set before attempting to open the database.
	if profile.DSN == "" {
		return nil, errors.New("dsn required")
	}

	if err := ensureUnicodeLowerRegistered(); err != nil {
		return nil, errors.Wrap(err, "failed to register sqlite unicode lower function")
	}

	// Connect to the database with some sane settings:
	// - No shared-cache: it's obsolete; WAL journal mode is a better solution.
	// - No foreign key constraints: it's currently disabled by default, but it's a
	// good practice to be explicit and prevent future surprises on SQLite upgrades.
	// - Journal mode set to WAL: it's the recommended journal mode for most applications
	// as it prevents locking issues.
	// - mmap size set to 0: it disables memory mapping, which can cause OOM errors on some systems.
	//
	// Notes:
	// - When using the `modernc.org/sqlite` driver, each pragma must be prefixed with `_pragma=`.
	//
	// References:
	// - https://pkg.go.dev/modernc.org/sqlite#Driver.Open
	// - https://www.sqlite.org/sharedcache.html
	// - https://www.sqlite.org/pragma.html
	sqliteDB, err := sql.Open("sqlite", profile.DSN+"?_pragma=foreign_keys(0)&_pragma=busy_timeout(10000)&_pragma=journal_mode(WAL)&_pragma=mmap_size(0)")
	if err != nil {
		return nil, errors.Wrapf(err, "failed to open db with dsn: %s", profile.DSN)
	}

	driver := DB{db: sqliteDB, profile: profile}

	return &driver, nil
}

func (d *DB) GetDB() *sql.DB {
	return d.db
}

func (d *DB) Close() error {
	return d.db.Close()
}

func (d *DB) IsInitialized(ctx context.Context) (bool, error) {
	// Check if the database is initialized by checking if the memo table exists.
	var exists bool
	err := d.db.QueryRowContext(ctx, "SELECT EXISTS(SELECT 1 FROM sqlite_master WHERE type='table' AND name='memo')").Scan(&exists)
	if err != nil {
		return false, errors.Wrap(err, "failed to check if database is initialized")
	}
	return exists, nil
}

// GetDatabaseSize returns the database size in bytes, or -1 if unavailable.
func (d *DB) GetDatabaseSize(ctx context.Context) (int64, error) {
	var pageCount, pageSize int64
	if err := d.db.QueryRowContext(ctx, "PRAGMA page_count").Scan(&pageCount); err != nil {
		return -1, errors.Wrap(err, "failed to read page_count")
	}
	if err := d.db.QueryRowContext(ctx, "PRAGMA page_size").Scan(&pageSize); err != nil {
		return -1, errors.Wrap(err, "failed to read page_size")
	}
	return pageCount * pageSize, nil
}
