// Package sqlite provides a pure-Go SQLite client with lifecycle management,
// health checks, and unit-of-work transaction support for Einherjar applications.
//
// # Overview
//
// [New] returns a [Component] that manages a [database/sql] connection pool,
// satisfies the [lifecycle.Component] lifecycle hooks (OnInit, OnStart, OnStop),
// and implements [observability.Checkable] with critical priority.
//
// [NewUnitOfWork] wraps multiple repository operations in a single serialized
// transaction via context injection — no transaction object is passed between
// functions. Write transactions are serialized through an internal mutex to
// prevent SQLITE_BUSY errors under concurrent goroutines.
//
// # Lifecycle Registration
//
//	db := sqlite.New(logger, cfg)
//	launcher.Register(db)
//	health.Register(db)
//
// # Querying
//
// Repository code receives a [Provider] or [Executor] and calls [Provider.GetExecutor]
// to obtain the active transaction (if inside a [UnitOfWork]) or the connection pool:
//
//	exec := db.GetExecutor(ctx)
//	row := exec.QueryRowContext(ctx, "SELECT id FROM users WHERE email = ?", email)
//	if err := row.Scan(&id); err != nil {
//	    return db.HandleError(err)  // maps sql.ErrNoRows → ErrNotFound, etc.
//	}
//
// # Unit of Work
//
// [NewUnitOfWork] wraps operations in a single serialized write transaction.
// The transaction is injected into the context; [Provider.GetExecutor] returns
// it automatically.
//
//	uow := sqlite.NewUnitOfWork(logger, db)
//	err := uow.Do(ctx, func(ctx context.Context) error {
//	    exec := db.GetExecutor(ctx) // returns active Tx
//	    _, err := exec.ExecContext(ctx, "INSERT INTO orders ...")
//	    return err
//	})
//
// # Error Handling
//
// [HandleError] translates database/sql and SQLite error codes into typed
// [xerrors] values. Call it at every point where a database error is first observed:
//
//	if err := row.Scan(&out); err != nil {
//	    return db.HandleError(err)
//	}
//
// Mapped codes:
//   - sql.ErrNoRows                   → ErrNotFound
//   - SQLITE_CONSTRAINT_UNIQUE (2067) → ErrAlreadyExists
//   - SQLITE_CONSTRAINT_PRIMARYKEY (1555) → ErrAlreadyExists
//   - SQLITE_CONSTRAINT_FOREIGNKEY (787)  → ErrInvalidInput
//   - all others                      → ErrInternal
//
// # Configuration
//
// All fields are read from environment variables with the EINHERJAR_SQLITE_* prefix:
//
//   - EINHERJAR_SQLITE_PATH          (required) — file path or ":memory:"
//   - EINHERJAR_SQLITE_MAX_OPEN_CONNS           — default: 1
//   - EINHERJAR_SQLITE_MAX_IDLE_CONNS           — default: 1
//   - EINHERJAR_SQLITE_PRAGMAS                  — default: "?_journal=WAL&_timeout=5000&_fk=true"
package sqlite