/**
 * Myext injecting policy to page using webRequest
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Copyright (C) 2021 jahoti
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * IMPORTS_START
 * IMPORT TYPE_PREFIX
 * IMPORT get_storage
 * IMPORT browser
 * IMPORT is_chrome
 * IMPORT gen_unique
 * IMPORT gen_nonce
 * IMPORT url_item
 * IMPORT url_extract_policy
 * IMPORT get_query_best
 * IMPORT csp_rule
 * IMPORTS_END
 */

var storage;
var query_best;

const csp_header_names = {
    "content-security-policy" : true,
    "x-webkit-csp" : true,
    "x-content-security-policy" : true
};

const header_name = "content-security-policy";

function is_csp_header(header)
{
    return !!csp_header_names[header.name.toLowerCase()];
}

function is_our_header(header, rule)
{
    return header.value === rule
}

function url_inject(details)
{
    const targets = url_extract_policy(details.url);
    if (targets.policy) {
	return;
    } else if (targets.signed) {
	/* Redirect; update policy */
	targets.target = targets.target2;
	delete targets.target2
    }

    let redirect_url = targets.base_url + targets.sig;
    let [pattern, settings] = query_best(targets.base_url);
    if (!pattern)
	/* Defaults */
	settings = {};
    
    const policy = {allow: settings.allow, nonce: gen_nonce()};
    
    redirect_url += encodeURIComponent(JSON.stringify(policy));
    if (targets.target)
	redirect_url += targets.target;
    if (targets.target2)
	redirect_url += targets.target2;

    return {redirectUrl: redirect_url};
}

function inject(details)
{
    const targets = url_extract_policy(details.url);
    if (!targets.policy)
	/* Block unsigned requests */
	return {cancel: true};

    const rule = csp_rule(targets.policy.nonce);

    var headers;

    if (targets.policy.allow) {
	/*
	 * Chrome doesn't have the buggy behavior of repeatedly injecting a
	 * header we injected once. Firefox does and we have to remove it there.
	 */
	if (is_chrome)
	    return {cancel: false};

	headers = details.responseHeaders.filter(h => !is_our_header(h, rule));
    } else {
	headers = details.responseHeaders.filter(h => !is_csp_header(h));

	headers.push({
	    name : header_name,
	    value : rule
	});
    }

    return {responseHeaders: headers};
}

async function start_policy_injector()
{
    storage = await get_storage();
    query_best = await get_query_best();

    let extra_opts = ["blocking", "responseHeaders"];
    if (is_chrome)
	extra_opts.push("extraHeaders");

    browser.webRequest.onBeforeRequest.addListener(
	url_inject,
	{
	    urls: ["<all_urls>"],
	    types: ["main_frame", "sub_frame"]
	},
	["blocking"]
    );

    browser.webRequest.onHeadersReceived.addListener(
	inject,
	{
	    urls: ["<all_urls>"],
	    types: ["main_frame", "sub_frame"]
	},
	extra_opts
    );
}

/*
 * EXPORTS_START
 * EXPORT start_policy_injector
 * EXPORTS_END
 */