/**
 * Hachette 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 get_storage
 * IMPORT browser
 * IMPORT is_chrome
 * IMPORT gen_nonce
 * IMPORT is_privileged_url
 * IMPORT sign_data
 * IMPORT extract_signed
 * IMPORT query_best
 * IMPORT sanitize_csp_header
 * IMPORT csp_rule
 * IMPORT is_csp_header_name
 * IMPORTS_END
 */

var storage;

function headers_inject(details)
{
    const url = details.url;
    if (is_privileged_url(url))
	return;

    const [pattern, settings] = query_best(storage, url);
    const allow = !!(settings && settings.allow);
    const nonce = gen_nonce();

    let orig_csp_headers;
    let old_signature;
    let hachette_header;
    let headers = details.responseHeaders;

    for (const header of headers.filter(h => h.name === "x-hachette")) {
	const match = /^([^%])(%.*)$/.exec(header.value);
	if (!match)
	    continue;

	const old_data = extract_signed(...match.splice(1, 2), [[0]]);
	if (!old_data || old_data.url !== url)
	    continue;

	/* Confirmed- it's the originals, smuggled in! */
	orig_csp_headers = old_data.csp_headers;
	old_signature = old_data.policy_signature;

	hachette_header = header;
	break;
    }

    if (!hachette_header) {
	hachette_header = {name: "x-hachette"};
	headers.push(hachette_header);
    }

    orig_csp_headers = orig_csp_headers ||
	headers.filter(h => is_csp_header_name(h.name));

    /* When blocking remove report-only CSP headers that snitch on us. */
    headers = headers.filter(h => !is_csp_header_name(h.name, !allow));

    if (old_signature)
	headers = headers.filter(h => h.name.search(old_signature) === -1);

    const policy_object = {allow, nonce, url};
    const sanitizer = h => sanitize_csp_header(h, policy_object);
    headers.push(...orig_csp_headers.map(sanitizer));

    const policy = encodeURIComponent(JSON.stringify(policy_object));
    const policy_signature = sign_data(policy, new Date());
    const later_30sec = new Date(new Date().getTime() + 30000).toGMTString();
    headers.push({
	name: "Set-Cookie",
	value: `hachette-${policy_signature}=${policy}; Expires=${later_30sec};`
    });

    /*
     * Smuggle in the signature and the original CSP headers for future use.
     * These are signed with a time of 0, as it's not clear there is a limit on
     * how long Firefox might retain headers in the cache.
     */
    let hachette_data = {csp_headers: orig_csp_headers, policy_signature, url};
    hachette_data = encodeURIComponent(JSON.stringify(hachette_data));
    hachette_header.value = sign_data(hachette_data, 0) + hachette_data;

    /* To ensure there is a CSP header if required */
    if (!allow)
	headers.push({name: "content-security-policy", value: csp_rule(nonce)});

    return {responseHeaders: headers};
}

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

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

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

/*
 * EXPORTS_START
 * EXPORT start_policy_injector
 * EXPORTS_END
 */