/*
 This file is part of GNU Taler
 (C) 2022 Taler Systems S.A.

 GNU Taler is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

import { CoreApiResponse, TalerError, TalerErrorCode } from "@gnu-taler/taler-util";

/**
 * This will modify all the pages that the user load when navigating with Web Extension enabled
 *
 * Can't do useful integration since it run in ISOLATED (or equivalent) mode.
 *
 * If taler support is expected, it will inject a script which will complete the integration.
 */

// https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Chrome_incompatibilities#content_script_environment

// ISOLATED mode in chromium browsers
// https://chromium.googlesource.com/chromium/src/+/master/third_party/blink/renderer/bindings/core/v8/V8BindingDesign.md#world
// X-Ray vision in Firefox
// https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Sharing_objects_with_page_scripts#xray_vision_in_firefox

// *** IMPORTANT ***

// Content script lifecycle during navigation
// In Firefox: Content scripts remain injected in a web page after the user has navigated away,
// however, window object properties are destroyed.
// In Chrome: Content scripts are destroyed when the user navigates away from a web page.

const documentDocTypeIsHTML =
  window.document.doctype && window.document.doctype.name === "html";
const suffixIsNotXMLorPDF =
  !window.location.pathname.endsWith(".xml") &&
  !window.location.pathname.endsWith(".pdf");
const rootElementIsHTML =
  document.documentElement.nodeName &&
  document.documentElement.nodeName.toLowerCase() === "html";



function validateTalerUri(uri: string): boolean {
  return (
    !!uri && (uri.startsWith("taler://") || uri.startsWith("taler+http://"))
  );
}

function convertURIToWebExtensionPath(uri: string) {
  const url = new URL(
    chrome.runtime.getURL(`static/wallet.html#/taler-uri/${encodeURIComponent(uri)}`),
  );
  return url.href;
}

// safe check, if one of this is true then taler handler is not useful
// or not expected
const shouldNotInject =
  !documentDocTypeIsHTML ||
  !suffixIsNotXMLorPDF ||
  !rootElementIsHTML;

const logger = {
  debug: (...msg: any[]) => { },
  info: (...msg: any[]) =>
    console.log(`${new Date().toISOString()} TALER`, ...msg),
  error: (...msg: any[]) =>
    console.error(`${new Date().toISOString()} TALER`, ...msg),
};

// logger.debug = logger.info

/**
 */
function redirectToTalerActionHandler(element: HTMLMetaElement) {
  const name = element.getAttribute("name")
  if (!name) return;
  if (name !== "taler-uri") return;
  const uri = element.getAttribute("content");
  if (!uri) return;

  if (!validateTalerUri(uri)) {
    logger.error(`taler:// URI is invalid: ${uri}`);
    return;
  }

  location.href = convertURIToWebExtensionPath(uri)
}

function injectTalerSupportScript(head: HTMLHeadElement) {
  const meta = head.querySelector("meta[name=taler-support]")

  const debugEnabled = meta?.getAttribute("debug") === "true";

  const scriptTag = document.createElement("script");

  scriptTag.setAttribute("async", "false");
  const url = new URL(
    chrome.runtime.getURL("/dist/taler-wallet-interaction-support.js"),
  );
  url.searchParams.set("id", chrome.runtime.id);
  if (debugEnabled) {
    url.searchParams.set("debug", "true");
  }
  scriptTag.src = url.href;

  try {
    head.insertBefore(scriptTag, head.children.length ? head.children[0] : null);
  } catch (e) {
    logger.info("inserting link handler failed!");
    logger.error(e);
  }
}


export interface ExtensionOperations {
  isInjectionEnabled: {
    request: void;
    response: boolean;
  };
  isAutoOpenEnabled: {
    request: void;
    response: boolean;
  };
}

export type MessageFromExtension<Op extends keyof ExtensionOperations> = {
  channel: "extension";
  operation: Op;
  payload: ExtensionOperations[Op]["request"];
};

export type MessageResponse = CoreApiResponse;

async function callBackground<Op extends keyof ExtensionOperations>(
  operation: Op,
  payload: ExtensionOperations[Op]["request"],
): Promise<ExtensionOperations[Op]["response"]> {
  const message: MessageFromExtension<Op> = {
    channel: "extension",
    operation,
    payload,
  };

  const response = await sendMessageToBackground(message);
  if (response.type === "error") {
    throw new Error(`Background operation "${operation}" failed`);
  }
  return response.result as any;
}


let nextMessageIndex = 0;
/**
 * 
 * @param message 
 * @returns 
 */
async function sendMessageToBackground<Op extends keyof ExtensionOperations>(
  message: MessageFromExtension<Op>,
): Promise<MessageResponse> {
  const messageWithId = { ...message, id: `id_${nextMessageIndex++ % 1000}` };

  if (!chrome.runtime.id) {
    return Promise.reject(TalerError.fromDetail(TalerErrorCode.WALLET_CORE_NOT_AVAILABLE, {}))
  }
  return new Promise<any>((resolve, reject) => {
    logger.debug("send operation to the wallet background", message, chrome.runtime.id);
    let timedout = false;
    const timerId = setTimeout(() => {
      timedout = true;
      reject(TalerError.fromDetail(TalerErrorCode.GENERIC_TIMEOUT, {}))
    }, 20 * 1000); //five seconds
    try {
      chrome.runtime.sendMessage(messageWithId, (backgroundResponse) => {
        if (timedout) {
          return false; //already rejected
        }
        clearTimeout(timerId);
        if (chrome.runtime.lastError) {
          reject(chrome.runtime.lastError.message);
        } else {
          resolve(backgroundResponse);
        }
        // return true to keep the channel open
        return true;
      });
    } catch (e) {
      console.log(e)
    }
  });
}

function start(
  onTalerMetaTagFound: (listener:(el: HTMLMetaElement)=>void) => void,
  onHeadReady: (listener:(el: HTMLHeadElement)=>void) => void
) {
  // do not run everywhere, this is just expected to run on html
  // sites
  if (shouldNotInject) return;

  const isAutoOpenEnabled_promise = callBackground("isAutoOpenEnabled", undefined)
  const isInjectionEnabled_promise = callBackground("isInjectionEnabled", undefined)

  onTalerMetaTagFound(async (el)=> {
    const enabled = await isAutoOpenEnabled_promise;
    if (!enabled) return;
    redirectToTalerActionHandler(el)
  })

  onHeadReady(async (el) => {
    const enabled = await isInjectionEnabled_promise;
    if (!enabled) return;
    injectTalerSupportScript(el)
  })

}

/**
 * Tries to find taler meta tag ASAP and report
 * @param notify 
 * @returns 
 */
function onTalerMetaTag(notify: (el: HTMLMetaElement) => void) {
  if (document.head) {
    const element = document.head.querySelector("meta[name=taler-uri]")
    if (!element) return;
    if (!(element instanceof HTMLMetaElement)) return;
    const name = element.getAttribute("name")
    if (!name) return;
    if (name !== "taler-uri") return;
    const uri = element.getAttribute("content");
    if (!uri) return;

    notify(element)
    return;
  }
  const obs = new MutationObserver(async function (mutations) {
    try {
      mutations.forEach((mut) => {
        if (mut.type === "childList") {
          mut.addedNodes.forEach((added) => {
            if (added instanceof HTMLMetaElement) {
              const name = added.getAttribute("name")
              if (!name) return;
              if (name !== "taler-uri") return;
              const uri = added.getAttribute("content");
              if (!uri) return;
              notify(added)
              obs.disconnect()
            }
          });
        }
      });
    } catch (e) {
      console.error(e)
    }
  })

  obs.observe(document, {
    childList: true,
    subtree: true,
    attributes: false,
  })

}

/**
 * Tries to find HEAD tag ASAP and report
 * @param notify 
 * @returns 
 */
function onHeaderReady(notify: (el: HTMLHeadElement) => void) {
  if (document.head) {
    notify(document.head)
    return;
  }
  const obs = new MutationObserver(async function (mutations) {
    try {
      mutations.forEach((mut) => {
        if (mut.type === "childList") {
          mut.addedNodes.forEach((added) => {
            if (added instanceof HTMLHeadElement) {

              notify(added)
              obs.disconnect()
            }
          });
        }
      });
    } catch (e) {
      console.error(e)
    }
  })

  obs.observe(document, {
    childList: true,
    subtree: true,
    attributes: false,
  })
}

start(onTalerMetaTag, onHeaderReady);