/**
 * NamespaceEngine  (G35)
 * ──────────────────────
 * Centralised namespace resolution engine for xml-xsd-engine v1.4.
 *
 * Responsibilities
 * ────────────────
 *  • Maintains a scoped prefix→URI mapping stack (push/pop per element)
 *  • Resolves QNames to { namespaceURI, localName, prefix }
 *  • Enforces XML Namespaces 1.0 constraints:
 *      - "xml"   prefix must map to http://www.w3.org/XML/1998/namespace
 *      - "xmlns" prefix is reserved and must not be declared
 *      - Empty prefix maps to the default namespace (or "" if undeclared)
 *  • Validates prefix declarations as they are pushed
 *  • Exposes helpers used by the parser, validator, XPath engine, and
 *    schema compiler
 *
 * The engine is intentionally stateful — one instance lives for the
 * duration of a single document parse or validation run.
 */
export declare const NS_XML = "http://www.w3.org/XML/1998/namespace";
export declare const NS_XMLNS = "http://www.w3.org/2000/xmlns/";
export declare const NS_XSD = "http://www.w3.org/2001/XMLSchema";
export declare const NS_XSI = "http://www.w3.org/2001/XMLSchema-instance";
export interface ResolvedName {
    /** Resolved namespace URI, or '' for no-namespace */
    namespaceURI: string;
    /** Local part (after colon, or full name if no prefix) */
    localName: string;
    /** Prefix used in the source, or '' */
    prefix: string;
    /** Original QName as it appeared in the source */
    qname: string;
}
export interface NamespaceDeclaration {
    /** '' = default namespace */
    prefix: string;
    /** The namespace URI being declared */
    uri: string;
}
export declare class NamespaceEngine {
    private stack;
    private current;
    /** Set of all namespace URIs seen during processing — useful for diagnostics */
    readonly seenURIs: Set<string>;
    constructor();
    /**
     * Enter a new namespace scope, declaring the given prefix→URI pairs.
     * Call once per element open tag, before resolving the element name.
     */
    pushScope(declarations: NamespaceDeclaration[]): void;
    /**
     * Leave the current element's namespace scope.
     * Must be called once per pushScope.
     */
    popScope(): void;
    /**
     * Current nesting depth (number of pushScope calls minus popScope calls).
     */
    get depth(): number;
    /**
     * Resolve a QName (e.g. "xs:element", "book", ":bad") in the current scope.
     *
     * Throws NS_UNDECLARED_PREFIX if the prefix cannot be found.
     * Throws NS_INVALID_QNAME   if the QName is structurally invalid.
     */
    resolveQName(qname: string, isAttribute?: boolean): ResolvedName;
    /**
     * Attempt to resolve a QName; returns null instead of throwing if the
     * prefix is not declared.  Useful for optional namespace-aware matching.
     */
    tryResolveQName(qname: string, isAttribute?: boolean): ResolvedName | null;
    /**
     * Resolve a prefix to its currently-in-scope URI.
     * Returns undefined if not declared.
     */
    resolvePrefix(prefix: string): string | undefined;
    /**
     * Return the currently active default namespace URI, or '' if none.
     */
    get defaultNamespace(): string;
    /**
     * Build a namespace-qualified lookup key of the form `{uri}localName`.
     * Used for consistent schema/element lookups throughout the engine.
     */
    static buildKey(namespaceURI: string, localName: string): string;
    /**
     * Parse a key of the form `{uri}local` or `local` back into parts.
     */
    static parseKey(key: string): {
        namespaceURI: string;
        localName: string;
    };
    /**
     * Given a namespace URI and a preferred prefix, return the prefix that
     * should be used in the current scope (may be the preferred one, or one
     * already in scope).  Registers a new declaration if needed.
     *
     * Used by the serializer to control namespace prefix output (G20).
     */
    getOrAllocatePrefix(uri: string, preferredPrefix: string): {
        prefix: string;
        newDeclaration: NamespaceDeclaration | null;
    };
    private _validateDeclaration;
    private _nsError;
}
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