import { BaseType } from "../Type/BaseType";
import { UndefinedType } from "../Type/UndefinedType";
import { UnionType } from "../Type/UnionType";
import { derefAnnotatedType } from "./derefType";
import { preserveAnnotation } from "./preserveAnnotation";

/**
 * Remove undefined types from union type. Returns the number of non-undefined properties.
 */
export function removeUndefined(propertyType: UnionType): { numRemoved: number; newType: BaseType } {
    const types: BaseType[] = [];
    let numRemoved = 0;

    for (const type of propertyType.getTypes()) {
        const newType = derefAnnotatedType(type);
        if (newType instanceof UndefinedType) {
            numRemoved += 1;
        } else if (newType instanceof UnionType) {
            const result = removeUndefined(newType);
            numRemoved += result.numRemoved;
            types.push(preserveAnnotation(type, result.newType));
        } else {
            types.push(type);
        }
    }

    const newType = types.length == 0 ? new UndefinedType() : types.length == 1 ? types[0] : new UnionType(types);

    return {
        numRemoved,
        newType,
    };
}