/**
 * Myext miscellaneous operations refactored to a separate file
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * IMPORTS_START
 * IMPORT sha256
 * IMPORT browser
 * IMPORT is_chrome
 * IMPORTS_END
 */

/*
 * generating unique, per-site value that can be computed synchronously
 * and is impossible to guess for a malicious website
 */
function gen_unique(url)
{
    return sha256(get_secure_salt() + url);
}

function get_secure_salt()
{
    if (is_chrome)
	return browser.runtime.getManifest().key.substring(0, 50);
    else
	return browser.runtime.getURL("dummy");
}

/*
 * stripping url from query and target (everything after `#' or `?'
 * gets removed)
 */
function url_item(url)
{
    let url_re = /^([^?#]*).*$/;
    let match = url_re.exec(url);
    return match[1];
}

/* csp rule that blocks all scripts except for those injected by us */
function csp_rule(nonce)
{
    let rule = `script-src 'nonce-${nonce}';`;
    if (is_chrome)
	rule += `script-src-elem 'nonce-${nonce}';`;
    return rule;
}

/*
 * EXPORTS_START
 * EXPORT gen_unique
 * EXPORT url_item
 * EXPORT csp_rule
 * EXPORTS_END
 */