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migrate.go
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migrate.go
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package litemigrate
import (
"context"
"database/sql"
"fmt"
"log"
"sort"
"golang.org/x/exp/slices"
_ "github.com/mattn/go-sqlite3"
)
// Migration represents a database migration with a version, description, up and down functions.
type Migration struct {
Version uint
Description string
Up func(tx *sql.Tx) error
Down func(tx *sql.Tx) error
}
// Migrations is a slice of Migration.
type Migrations []Migration
// Sorted returns a sorted slice of migrations based on their versions.
func (ms *Migrations) sorted() []Migration {
sortedMigrations := make([]Migration, len(*ms))
copy(sortedMigrations, *ms)
sort.Slice(sortedMigrations, func(i, j int) bool {
return sortedMigrations[i].Version < sortedMigrations[j].Version
})
return sortedMigrations
}
// Database represents a database connection and migration data.
type Database struct {
conn *sql.DB
migrationTable string
migrations *Migrations
}
// New creates a new database instance with a DSN string and migrations.
func New(dsn string, migrations *Migrations) (*Database, error) {
conn, err := sql.Open("sqlite3", dsn)
if err != nil {
return nil, err
}
return NewWithConn(conn, migrations), nil
}
// NewWithConn creates a new database instance with a database connection and migrations.
func NewWithConn(conn *sql.DB, migrations *Migrations) *Database {
return &Database{
conn: conn,
migrationTable: "_migrations",
migrations: migrations,
}
}
// Close closes the database connection.
func (db *Database) Close() error {
return db.conn.Close()
}
// SetMigrationTable sets the name of the migration table.
func (db *Database) SetMigrationTable(table string) *Database {
db.migrationTable = table
return db
}
// MigrateUp migrates the database up to the current version (highest version).
func (db *Database) MigrateUp(ctx context.Context) error {
tx, err := db.conn.BeginTx(ctx, nil)
if err != nil {
return err
}
defer tx.Rollback()
err = db.createMigrationTable(ctx, tx)
if err != nil {
return err
}
index, err := db.getMigrationIndex(ctx, tx)
if err != nil {
return err
}
migrationExists := map[uint]bool{}
for _, migration := range db.migrations.sorted() {
if migration.Version == 0 || migration.Description == "" {
return fmt.Errorf("invalid migration: version and description must be set")
}
if migration.Up == nil || migration.Down == nil {
return fmt.Errorf("invalid migration: up and down must be set")
}
if migrationExists[migration.Version] {
return fmt.Errorf("duplicate migration: (version=%v, description=%s) already exists", migration.Version, migration.Description)
}
migrationExists[migration.Version] = true
if slices.Contains(index, migration.Version) {
log.Printf("skipping migration: (version=%v, description=%s) already exists", migration.Version, migration.Description)
continue
}
if err := migration.Up(tx); err != nil {
return err
}
if err := db.insertMigration(ctx, tx, migration.Version, migration.Description); err != nil {
return err
}
log.Printf("migrated database up (version=%v, description=%s)", migration.Version, migration.Description)
}
return tx.Commit()
}
// MigrateDown migrates the database down by the specified amount.
func (db *Database) MigrateDown(ctx context.Context, amount int) error {
tx, err := db.conn.BeginTx(ctx, nil)
if err != nil {
return err
}
defer tx.Rollback()
err = db.createMigrationTable(ctx, tx)
if err != nil {
return err
}
index, err := db.getMigrationIndex(ctx, tx)
if err != nil {
return err
}
if len(index) == 0 {
return fmt.Errorf("no migrations to rollback")
}
if amount > len(index) {
amount = len(index)
}
for i := len(index) - 1; i >= len(index)-amount; i-- {
migration := db.migrations.sorted()[index[i]-1]
if migration.Version == 0 || migration.Description == "" {
return fmt.Errorf("invalid migration: version and description must be set")
}
if migration.Up == nil || migration.Down == nil {
return fmt.Errorf("invalid migration: up and down must be set")
}
if !slices.Contains(index, migration.Version) {
return fmt.Errorf("migration (version=%v, description=%s) doesn't exists", migration.Version, migration.Description)
}
if err := migration.Down(tx); err != nil {
return err
}
if err := db.deleteMigration(ctx, tx, migration.Version); err != nil {
return err
}
log.Printf("migrated database down (version=%v, description=%s)", migration.Version, migration.Description)
}
return tx.Commit()
}
// CurrentVersion returns the current version of the database.
func (db *Database) CurrentVersion(ctx context.Context) (uint, error) {
query := fmt.Sprintf("SELECT version FROM %s ORDER BY version DESC LIMIT 1;", db.migrationTable)
rows, err := db.conn.QueryContext(ctx, query)
if err != nil {
return 0, err
}
if !rows.Next() {
return 0, nil
}
version := uint(0)
if err := rows.Scan(&version); err != nil {
return 0, err
}
return version, nil
}
func (db *Database) createMigrationTable(ctx context.Context, tx *sql.Tx) error {
_, err := tx.ExecContext(ctx, fmt.Sprintf(`
CREATE TABLE IF NOT EXISTS %s (
id INTEGER PRIMARY KEY AUTOINCREMENT,
version INTEGER UNIQUE NOT NULL,
description VARCHAR(255) UNIQUE NOT NULL
);
`, db.migrationTable))
if err != nil {
return fmt.Errorf("failed to create migration table: %w", err)
}
return nil
}
func (db *Database) getMigrationIndex(ctx context.Context, tx *sql.Tx) ([]uint, error) {
query := fmt.Sprintf("SELECT version FROM %s ORDER BY version ASC;", db.migrationTable)
rows, err := tx.QueryContext(ctx, query)
if err != nil {
return nil, err
}
defer rows.Close()
index := make([]uint, 0)
for rows.Next() {
var version uint
if err := rows.Scan(&version); err != nil {
return nil, err
}
index = append(index, version)
}
if err := rows.Err(); err != nil {
return nil, fmt.Errorf("failed to scan rows: %w", err)
}
return index, nil
}
func (db *Database) insertMigration(ctx context.Context, tx *sql.Tx, version uint, description string) error {
query := fmt.Sprintf("INSERT INTO %s (version, description) VALUES (?, ?);", db.migrationTable)
_, err := tx.ExecContext(ctx, query, version, description)
if err != nil {
return fmt.Errorf("failed to insert migration (version=%v, description=%s): %w", version, description, err)
}
return nil
}
func (db *Database) deleteMigration(ctx context.Context, tx *sql.Tx, version uint) error {
query := fmt.Sprintf("DELETE FROM %s WHERE version = ?;", db.migrationTable)
_, err := tx.ExecContext(ctx, query, version)
if err != nil {
return fmt.Errorf("failed to delete migration (version=%v): %w", version, err)
}
return nil
}