import type {
    BitPackerSchema,
    PackingContext,
    PackingStrategy,
} from "@suaveplan/bitpacker";
import { isOptionalSchema } from "@suaveplan/bitpacker";

export class OptionalPackingStrategy implements PackingStrategy {
    canHandle(schema: BitPackerSchema): boolean {
        return isOptionalSchema(schema);
    }

    pack(
        data: unknown,
        schema: BitPackerSchema,
        context: PackingContext
    ): void {
        const { _optional: inner } = schema as { _optional: BitPackerSchema };

        const present = data !== undefined && data !== null;
        context.writer.writeBool(present);

        if (present) {
            context.packValue(data, inner);
        }
    }

    unpack(schema: BitPackerSchema, context: PackingContext): unknown {
        const { _optional: inner } = schema as { _optional: BitPackerSchema };

        const present = context.reader.readBool();
        if (!present) {
            return undefined;
        }
        return context.unpackValue(inner);
    }
}