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 * Copyright (C) 2026, Leo Galambos
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 *    This product includes software developed by the Egothor project.
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package zeroecho.pki.server;

import java.util.Objects;
import java.util.Set;

import zeroecho.pki.api.PkiId;

/**
 * Immutable process policy controlling which logical authorities one realm
 * context may expose.
 *
 * @param mode exposure mode
 * @param authorityIds exact exposed authorities for explicit mode
 * @param authorityCreationPermitted whether realm-scoped authority creation is permitted
 */
public record AuthorityExposurePolicy(Mode mode, Set<PkiId> authorityIds,
        boolean authorityCreationPermitted) {
    /** Closed authority-exposure modes. */
    public enum Mode {
        /** Every authority in the realm session is eligible for scoped exposure. */
        ALL_REALM_AUTHORITIES(1),
        /** Only the exact configured authority identities are eligible. */
        EXPLICIT_AUTHORITIES(2);

        private final int code;

        Mode(int code) {
            this.code = code;
        }

        /** @return stable persistence code */
        public int code() {
            return code;
        }

        /** Resolves one stable persistence code. */
        public static Mode fromCode(int code) {
            return switch (code) {
                case 1 -> ALL_REALM_AUTHORITIES;
                case 2 -> EXPLICIT_AUTHORITIES;
                default -> throw new IllegalArgumentException("Unknown authority exposure code");
            };
        }
    }

    /** Validates and defensively snapshots the exposure policy. */
    public AuthorityExposurePolicy {
        Objects.requireNonNull(mode, "mode");
        authorityIds = Set.copyOf(Objects.requireNonNull(authorityIds, "authorityIds"));
        if (mode == Mode.ALL_REALM_AUTHORITIES && !authorityIds.isEmpty()) {
            throw new IllegalArgumentException("All-authority mode cannot carry an explicit set");
        }
        if (mode == Mode.EXPLICIT_AUTHORITIES && authorityIds.isEmpty()) {
            throw new IllegalArgumentException("Explicit authority mode requires at least one authority");
        }
    }

    /**
     * Tests process exposure for one canonical authority.
     *
     * @param authorityId authority to test
     * @return whether the process may expose it
     */
    public boolean allows(PkiId authorityId) {
        Objects.requireNonNull(authorityId, "authorityId");
        return mode == Mode.ALL_REALM_AUTHORITIES || authorityIds.contains(authorityId);
    }
}
