/**
 * Hachette main content script run in all frames
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Copyright (C) 2021 jahoti
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * IMPORTS_START
 * IMPORT handle_page_actions
 * IMPORT extract_signed
 * IMPORT sign_data
 * IMPORT gen_nonce
 * IMPORT is_privileged_url
 * IMPORT mozilla_suppress_scripts
 * IMPORT is_chrome
 * IMPORT is_mozilla
 * IMPORT start_activity_info_server
 * IMPORT modify_on_the_fly
 * IMPORTS_END
 */

function accept_node(node, parent)
{
    const clone = document.importNode(node, false);
    node.hachette_corresponding = clone;
    /*
     * TODO: Stop page's own issues like "Error parsing a meta element's
     * content:" from appearing as extension's errors.
     */
    parent.hachette_corresponding.appendChild(clone);
}

function extract_cookie_policy(cookie, min_time)
{
    let best_result = {time: -1};
    let policy = null;
    const extracted_signatures = [];

    for (const match of cookie.matchAll(/hachette-(\w*)=([^;]*)/g)) {
	const new_result = extract_signed(...match.slice(1, 3));
	if (new_result.fail)
	    continue;

	extracted_signatures.push(match[1]);

	if (new_result.time < Math.max(min_time, best_result.time))
	    continue;

	/* This should succeed - it's our self-produced valid JSON. */
	const new_policy = JSON.parse(decodeURIComponent(new_result.data));
	if (new_policy.url !== document.URL)
	    continue;

	best_result = new_result;
	policy = new_policy;
    }

    return [policy, extracted_signatures];
}

function extract_url_policy(url, min_time)
{
    const [base_url, payload, anchor] =
	  /^([^#]*)#?([^#]*)(#?.*)$/.exec(url).splice(1, 4);

    const match = /^hachette_([^_]+)_(.*)$/.exec(payload);
    if (!match)
	return [null, url];

    const result = extract_signed(...match.slice(1, 3));
    if (result.fail)
	return [null, url];

    const original_url = base_url + anchor;
    const policy = result.time < min_time ? null :
	  JSON.parse(decodeURIComponent(result.data));

    return [policy.url === original_url ? policy : null, original_url];
}

function employ_nonhttp_policy(policy)
{
    if (!policy.allow)
	return;

    policy.nonce = gen_nonce();
    const [base_url, target] = /^([^#]*)(#?.*)$/.exec(policy.url).slice(1, 3);
    const encoded_policy = encodeURIComponent(JSON.stringify(policy));
    const payload = "hachette_" +
	  sign_data(encoded_policy, new Date().getTime()).join("_");
    const resulting_url = `${base_url}#${payload}${target}`;
    location.href = resulting_url;
    location.reload();
}

if (!is_privileged_url(document.URL)) {
    let policy_received_callback = () => undefined;
    let policy;

    /* Signature valid for half an hour. */
    const min_time = new Date().getTime() - 1800 * 1000;

    if (/^https?:/.test(document.URL)) {
	let signatures;
	[policy, signatures] = extract_cookie_policy(document.cookie, min_time);
	for (const signature of signatures)
	    document.cookie = `hachette-${signature}=; Max-Age=-1;`;
    } else {
	const scheme = /^([^:]*)/.exec(document.URL)[1];
	const known_scheme = ["file", "ftp"].includes(scheme);

	if (!known_scheme)
	    console.warn(`Unknown url scheme: \`${scheme}'!`);

	let original_url;
	[policy, original_url] = extract_url_policy(document.URL, min_time);
	history.replaceState(null, "", original_url);

	if (known_scheme && !policy)
	    policy_received_callback = employ_nonhttp_policy;
    }

    if (!policy) {
	console.warn("Using fallback policy!");
	policy = {allow: false, nonce: gen_nonce()};
    }

    handle_page_actions(policy.nonce, policy_received_callback);

    if (!policy.allow) {
	if (is_mozilla) {
	    const script = document.querySelector("script");
	    if (script)
		script.textContent = "throw 'blocked';\n" + script.textContent;
	}
	const old_html = document.documentElement;
	const new_html = document.createElement("html");
	old_html.replaceWith(new_html);
	old_html.hachette_corresponding = new_html;

	const modify_end =
	      modify_on_the_fly(old_html, policy, {node_eater: accept_node});
	document.addEventListener("DOMContentLoaded", modify_end);
    }

    start_activity_info_server();
}