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

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

/* Generate a random base64-encoded 128-bit sequence */
function gen_nonce()
{
    let randomData = new Uint8Array(16);
    crypto.getRandomValues(randomData);
    return btoa(String.fromCharCode.apply(null, randomData));
}

/*
 * 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];
}

/*
 * Assume a url like: https://example.com/green?illuminati=confirmed#tinky#winky
 * This function will make it into an object like:
 * {
 *     "base_url" : "https://example.com/green?illuminati=confirmed",
 *     "target" : "#tinky",
 *     "target2" : "#winky"
 * }
 * In case url doesn't have 2 #'s, target2 and target can be set to undefined.
 */
function url_extract_target(url)
{
    let url_re = /^([^#]*)((#[^#]*)(#.*)?)?$/;
    let match = url_re.exec(url);
    return {
	base_url : match[1],
	target : match[3],
	target2 : match[4]
    };
}

/* 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;
}

/*
 * Print item together with type, e.g.
 * nice_name("s", "hello") → "hello (script)"
 */
function nice_name(prefix, name)
{
    return `${name} (${TYPE_NAME[prefix]})`;
}

/* Open settings tab with given item's editing already on. */
function open_in_settings(prefix, name)
{
    name = encodeURIComponent(name);
    const url = browser.runtime.getURL("html/options.html#" + prefix + name);
    window.open(url, "_blank");
}

/* Check if url corresponds to a browser's special page */
function is_privileged_url(url)
{
    return !!/^(chrome(-extension)?|moz-extension):\/\/|^about:/i.exec(url);
}

/* Extract any policy present in the URL */
function url_extract_policy(url)
{
    var policy_string;
    const targets = url_extract_target(url);
    
    try {
	policy_string = targets.target.substring(65);
	targets.policy = JSON.parse(decodeURIComponent(policy_string));
    } catch (e) {
	/* TODO what should happen here? */
    }
    
    if (targets.policy) {
	const sig = gen_unique(policy_string + targets.base_url);
	targets.valid_sig = targets.target.substring(1, 65) === sig;
    }

    return targets;
}

/*
 * EXPORTS_START
 * EXPORT gen_nonce
 * EXPORT gen_unique
 * EXPORT url_item
 * EXPORT url_extract_target
 * EXPORT url_extract_policy
 * EXPORT csp_rule
 * EXPORT nice_name
 * EXPORT open_in_settings
 * EXPORT is_privileged_url
 * EXPORTS_END
 */