/**
 * @fileoverview Provides a utility class for parsing XML strings.
 * Wraps the `fast-xml-parser` peer dependency (lazy-loaded on first use) and strips
 * optional `<think>...</think>` blocks that LLMs sometimes prepend to structured
 * output before parsing. The underlying `XMLParser` instance is created once with
 * `processEntities: false` and `htmlEntities: false` and reused for all calls.
 *
 * Peer dependency: `fast-xml-parser` — install with `bun add fast-xml-parser`.
 * @module src/utils/parsing/xmlParser
 */
import { configurationError, validationError } from '../../types-global/errors.js';
import { logger } from '../../utils/internal/logger.js';
import { requestContextService } from '../../utils/internal/requestContext.js';
import { thinkBlockRegex } from './thinkBlock.js';
let _fxp;
let _xmlParserInstance;
const FXP_MODULE = 'fast-xml-parser';
async function getFxp() {
    if (_fxp)
        return _fxp;
    _fxp = await import(FXP_MODULE).catch(() => {
        throw configurationError('Install "fast-xml-parser" to use XML parsing: bun add fast-xml-parser');
    });
    return _fxp;
}
/**
 * Utility class for parsing XML strings.
 *
 * Lazily loads `fast-xml-parser` on first use (peer dependency — install with
 * `bun add fast-xml-parser`). The `XMLParser` instance is constructed once at first
 * call with `{ processEntities: false, htmlEntities: false }` and cached for subsequent
 * calls. Handles optional `<think>...</think>` blocks that some LLMs prepend to
 * structured output; the block's content is logged at debug level and stripped before
 * parsing.
 */
export class XmlParser {
    /**
     * Parses an XML string into a typed JavaScript object.
     *
     * This method is async because `fast-xml-parser` is loaded lazily on first call.
     * If the input begins with a `<think>...</think>` block, that block is stripped
     * and its content logged before parsing the remainder. The parser is configured with
     * `processEntities: false` and `htmlEntities: false` — entity references are passed
     * through as-is.
     *
     * @template T - The expected type of the parsed result. Defaults to `unknown`.
     * @param xmlString - The XML string to parse. May be prefixed with a `<think>` block.
     * @param context - Optional request context for correlated logging and error metadata.
     * @returns A promise resolving to the parsed object cast to `T`.
     * @throws {McpError} With code `ConfigurationError` if `fast-xml-parser` is not installed.
     * @throws {McpError} With code `ValidationError` if the string is empty after stripping
     *   the `<think>` block, or if `fast-xml-parser` throws during parsing.
     * @example
     * ```typescript
     * import { xmlParser } from '../../utils/parsing/xmlParser.js';
     *
     * const result = await xmlParser.parse<{ root: { key: string } }>('<root><key>value</key></root>');
     * console.log(result.root.key); // 'value'
     *
     * // LLM output with a <think> preamble
     * const fromLlm = await xmlParser.parse('<think>reasoning</think>\n<root><key>value</key></root>');
     * console.log(fromLlm); // { root: { key: 'value' } }
     * ```
     */
    async parse(xmlString, context) {
        let stringToParse = xmlString;
        const match = xmlString.match(thinkBlockRegex);
        if (match) {
            const thinkContent = match[1]?.trim() ?? '';
            const restOfString = match[2] ?? '';
            const logContext = context ||
                requestContextService.createRequestContext({
                    operation: 'XmlParser.thinkBlock',
                });
            if (thinkContent) {
                logger.debug('LLM <think> block detected and logged.', {
                    ...logContext,
                    thinkContent,
                });
            }
            else {
                logger.debug('Empty LLM <think> block detected.', logContext);
            }
            stringToParse = restOfString;
        }
        stringToParse = stringToParse.trim();
        if (!stringToParse) {
            throw validationError('XML string is empty after removing <think> block and trimming.', context);
        }
        try {
            const fxp = await getFxp();
            _xmlParserInstance ??= new fxp.XMLParser({
                processEntities: false,
                htmlEntities: false,
            });
            return _xmlParserInstance.parse(stringToParse);
        }
        catch (e) {
            const error = e instanceof Error ? e : new Error(String(e));
            const errorLogContext = context ||
                requestContextService.createRequestContext({
                    operation: 'XmlParser.parseError',
                });
            logger.error('Failed to parse XML content.', {
                ...errorLogContext,
                errorDetails: error.message,
                contentAttempted: stringToParse.substring(0, 200),
            });
            throw validationError(`Failed to parse XML: ${error.message}`, {
                ...context,
                originalContentSample: stringToParse.substring(0, 200) + (stringToParse.length > 200 ? '...' : ''),
                rawError: error instanceof Error ? error.stack : String(error),
            });
        }
    }
}
/**
 * Singleton instance of {@link XmlParser}.
 *
 * Prefer this over constructing a new `XmlParser` directly. Lazily loads `fast-xml-parser`
 * on first call and caches the `XMLParser` instance, so there is no startup cost if XML
 * parsing is never used.
 *
 * @example
 * ```typescript
 * import { xmlParser } from '../../utils/parsing/xmlParser.js';
 *
 * // Basic parse
 * const result = await xmlParser.parse<{ root: { id: string } }>('<root><id>42</id></root>');
 * console.log(result.root.id); // '42'
 *
 * // With request context for correlated logging
 * import { requestContextService } from '../../utils/internal/requestContext.js';
 * const ctx = requestContextService.createRequestContext({ operation: 'parseResponse' });
 * const data = await xmlParser.parse<ApiResponse>(rawXml, ctx);
 *
 * // Strips LLM <think> preamble automatically
 * const fromLlm = await xmlParser.parse('<think>let me think</think>\n<root><key>value</key></root>');
 * console.log(fromLlm); // { root: { key: 'value' } }
 * ```
 */
export const xmlParser = new XmlParser();
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