/*******************************************************************************
 * Copyright (C) 2026, Leo Galambos
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 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
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 * 1. Redistributions of source code must retain the above copyright notice, this
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 * 3. All advertising materials mentioning features or use of this software must
 *    display the following acknowledgement:
 *    This product includes software developed by the Egothor project.
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package zeroecho.pki.spi;

import java.util.Collections;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;

/**
 * Backend configuration for {@link ConfigurableProvider} instances.
 *
 * <p>
 * Values are stringly-typed by design to keep the SPI generic and stable across
 * different backends (filesystem, JDBC, remote services). Providers interpret
 * keys relevant to their backend and must ignore unknown keys for forward
 * compatibility.
 * </p>
 *
 * <p>
 * The {@code backendId} is the selected provider identifier
 * ({@link ConfigurableProvider#id()}), used for diagnostics and selection
 * correlation. It is not a URL, driver name, nor any secret.
 * </p>
 *
 * <p>
 * This record is immutable and safe to share. Configuration values may be
 * sensitive and must not be logged. If diagnostics are needed, log keys only.
 * </p>
 *
 * @param backendId  selected backend id (never blank)
 * @param properties backend properties (never {@code null})
 */
public record ProviderConfig(String backendId, Map<String, String> properties) {

    /**
     * Canonical constructor with validation and defensive wrapping.
     *
     * @param backendId  backend id (never blank)
     * @param properties properties (never {@code null})
     */
    public ProviderConfig {
        Objects.requireNonNull(backendId, "backendId");
        Objects.requireNonNull(properties, "properties");
        if (backendId.isBlank()) {
            throw new IllegalArgumentException("backendId must not be blank");
        }
        properties = Collections.unmodifiableMap(properties);
    }

    /**
     * Returns an optional value for the given key.
     *
     * @param key key (never {@code null})
     * @return optional value (never {@code null})
     */
    public Optional<String> get(String key) {
        Objects.requireNonNull(key, "key");
        return Optional.ofNullable(properties.get(key));
    }

    /**
     * Returns a required non-blank value for the given key.
     *
     * @param key key (never {@code null})
     * @return value (never {@code null}, never blank)
     * @throws IllegalArgumentException if missing or blank
     */
    public String require(String key) {
        Objects.requireNonNull(key, "key");
        String v = properties.get(key);
        if (v == null || v.isBlank()) {
            throw new IllegalArgumentException("Missing required config key: " + key);
        }
        return v;
    }
}
