/**
 * XMLHttpRequest Instrumentation and Wrapper
 *
 * Provides comprehensive XMLHttpRequest monitoring and instrumentation:
 * - Request/response interception
 * - Method and URL tracking
 * - Header manipulation monitoring
 * - Request body capture
 * - Response status tracking
 */

const XHR_DATA_KEY = "__sentry_xhr_v3__";

/**
 * Instrument XMLHttpRequest for monitoring
 * Creates a wrapper around XHR methods to capture request/response data
 */
function instrumentXHR() {
  const globalObj = getGlobalObject();

  if (!globalObj.XMLHttpRequest) {
    return;
  }

  const xhrPrototype = XMLHttpRequest.prototype;

  // Instrument the open method
  fillPrototype(xhrPrototype, "open", function (originalOpen) {
    return function instrumentedOpen(...args) {
      const startTime = Date.now();
      const method = isString(args[0]) ? args[0].toUpperCase() : undefined;
      const url = parseUrl(args[1]);

      if (!method || !url) {
        return originalOpen.apply(this, args);
      }

      // Store request metadata
      this[XHR_DATA_KEY] = {
        method,
        url,
        request_headers: {},
      };

      // Skip instrumentation for Sentry's own requests
      if (method === "POST" && url.match(/sentry_key/)) {
        this.__sentry_own_request__ = true;
      }

      const onReadyStateChange = () => {
        const xhrData = this[XHR_DATA_KEY];
        if (!xhrData) return;

        if (this.readyState === 4) {
          try {
            xhrData.status_code = this.status;
          } catch (error) {
            // Status might not be available
          }

          const eventData = {
            args: [method, url],
            endTimestamp: Date.now(),
            startTimestamp: startTime,
            xhr: this,
          };

          triggerXhrHandlers("xhr", eventData);
        }
      };

      // Handle readystatechange event
      if (
        "onreadystatechange" in this &&
        typeof this.onreadystatechange === "function"
      ) {
        fillPrototype(this, "onreadystatechange", function (originalHandler) {
          return function wrappedHandler(...handlerArgs) {
            onReadyStateChange();
            return originalHandler.apply(this, handlerArgs);
          };
        });
      } else {
        this.addEventListener("readystatechange", onReadyStateChange);
      }

      // Instrument setRequestHeader
      fillPrototype(this, "setRequestHeader", function (originalSetHeader) {
        return function instrumentedSetHeader(...headerArgs) {
          const [headerName, headerValue] = headerArgs;
          const xhrData = this[XHR_DATA_KEY];

          if (xhrData && isString(headerName) && isString(headerValue)) {
            xhrData.request_headers[headerName.toLowerCase()] = headerValue;
          }

          return originalSetHeader.apply(this, headerArgs);
        };
      });

      return originalOpen.apply(this, args);
    };
  });

  // Instrument the send method
  fillPrototype(xhrPrototype, "send", function (originalSend) {
    return function instrumentedSend(...args) {
      const xhrData = this[XHR_DATA_KEY];

      if (!xhrData) {
        return originalSend.apply(this, args);
      }

      // Capture request body
      if (args[0] !== undefined) {
        xhrData.body = args[0];
      }

      const eventData = {
        args: [xhrData.method, xhrData.url],
        startTimestamp: Date.now(),
        xhr: this,
      };

      triggerXhrHandlers("xhr", eventData);

      return originalSend.apply(this, args);
    };
  });
}

/**
 * Parse URL from various input types
 * @param {any} url - URL to parse
 * @returns {string|undefined} Parsed URL string
 */
function parseUrl(url) {
  if (isString(url)) {
    return url;
  }

  try {
    return url.toString();
  } catch (error) {
    return undefined;
  }
}

/**
 * Add XHR instrumentation handler
 * @param {Function} handler - Handler function to call on XHR events
 */
function addXhrInstrumentationHandler(handler) {
  addHandler("xhr", handler);
  maybeInstrument("xhr", instrumentXHR);
}

/**
 * Create comprehensive XHR monitoring wrapper
 * @param {Object} options - Configuration options
 * @returns {Object} XHR monitoring interface
 */
function createXhrMonitor(options = {}) {
  const {
    onRequest = null,
    onResponse = null,
    onError = null,
    captureBody = true,
    captureHeaders = true,
  } = options;

  const handlers = [];

  const monitor = {
    /**
     * Start monitoring XHR requests
     */
    start() {
      const handler = (data) => {
        try {
          if (data.startTimestamp && !data.endTimestamp) {
            // Request started
            if (onRequest) {
              onRequest({
                method: data.args[0],
                url: data.args[1],
                timestamp: data.startTimestamp,
                xhr: data.xhr,
              });
            }
          } else if (data.endTimestamp) {
            // Request completed
            const xhr = data.xhr;
            const xhrData = xhr[XHR_DATA_KEY];

            const responseData = {
              method: data.args[0],
              url: data.args[1],
              startTime: data.startTimestamp,
              endTime: data.endTimestamp,
              duration: data.endTimestamp - data.startTimestamp,
              status: xhrData ? xhrData.status_code : xhr.status,
              headers: captureHeaders && xhrData ? xhrData.request_headers : {},
              body: captureBody && xhrData ? xhrData.body : undefined,
              response: {
                status: xhr.status,
                statusText: xhr.statusText,
                headers: getResponseHeaders(xhr),
              },
            };

            if (xhr.status >= 200 && xhr.status < 300) {
              if (onResponse) onResponse(responseData);
            } else {
              if (onError)
                onError({
                  ...responseData,
                  error: new Error(`HTTP ${xhr.status}`),
                });
            }
          }
        } catch (error) {
          if (onError) {
            onError({ error, data });
          }
        }
      };

      handlers.push(handler);
      addXhrInstrumentationHandler(handler);
    },

    /**
     * Stop monitoring XHR requests
     */
    stop() {
      // Note: Cannot easily remove handlers in current implementation
      // Would need to modify the handler system to support removal
      handlers.length = 0;
    },

    /**
     * Get current configuration
     */
    getConfig() {
      return {
        captureBody,
        captureHeaders,
        handlersCount: handlers.length,
      };
    },
  };

  return monitor;
}

/**
 * Extract response headers from XHR object
 * @param {XMLHttpRequest} xhr - XHR object
 * @returns {Object} Response headers object
 */
function getResponseHeaders(xhr) {
  try {
    const headerString = xhr.getAllResponseHeaders();
    if (!headerString) return {};

    const headers = {};
    const headerLines = headerString.split("\r\n");

    for (const line of headerLines) {
      const colonIndex = line.indexOf(":");
      if (colonIndex > 0) {
        const name = line.slice(0, colonIndex).trim().toLowerCase();
        const value = line.slice(colonIndex + 1).trim();
        headers[name] = value;
      }
    }

    return headers;
  } catch (error) {
    return {};
  }
}

// Helper functions (would normally be imported)
function getGlobalObject() {
  return (
    (typeof globalThis === "object" && globalThis) ||
    (typeof window === "object" && window) ||
    (typeof self === "object" && self) ||
    (typeof global === "object" && global) ||
    {}
  );
}

function isString(value) {
  return typeof value === "string";
}

function fillPrototype(source, property, replacer) {
  if (!(property in source)) return;

  const original = source[property];
  const replacement = replacer(original);

  if (typeof replacement === "function") {
    try {
      replacement.prototype = original.prototype;
    } catch (error) {
      // Ignore prototype setting errors
    }

    source[property] = replacement;
  }
}

// Mock handler system (would normally be imported)
let handlers = {};
let instrumented = {};

function addHandler(type, handler) {
  if (!handlers[type]) {
    handlers[type] = [];
  }
  handlers[type].push(handler);
}

function maybeInstrument(type, instrumentFunction) {
  if (!instrumented[type]) {
    instrumentFunction();
    instrumented[type] = true;
  }
}

function triggerXhrHandlers(type, data) {
  const typeHandlers = handlers[type];
  if (!typeHandlers) return;

  for (const handler of typeHandlers) {
    try {
      handler(data);
    } catch (error) {
      console.error("Error in XHR handler:", error);
    }
  }
}

module.exports = {
  instrumentXHR,
  addXhrInstrumentationHandler,
  createXhrMonitor,
  parseUrl,
  getResponseHeaders,
  XHR_DATA_KEY,
};