/**
 * This file is part of Haketilo.
 *
 * Function: Injecting policy to page by modifying HTTP headers.
 *
 * Copyright (C) 2021 Wojtek Kosior
 * Copyright (C) 2021 jahoti
 * Redistribution terms are gathered in the `copyright' file.
 */

/*
 * IMPORTS_START
 * IMPORT sign_data
 * IMPORT extract_signed
 * IMPORT make_csp_rule
 * IMPORT csp_header_regex
 * IMPORTS_END
 */

function inject_csp_headers(headers, policy)
{
    let csp_headers;
    let old_signature;
    let haketilo_header;

    for (const header of headers.filter(h => h.name === "x-haketilo")) {
	/* x-haketilo header has format: <signature>_0_<data> */
	const match = /^([^_]+)_(0_.*)$/.exec(header.value);
	if (!match)
	    continue;

	const result = extract_signed(...match.slice(1, 3));
	if (result.fail)
	    continue;

	/* This should succeed - it's our self-produced valid JSON. */
	const old_data = JSON.parse(decodeURIComponent(result.data));

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

	haketilo_header = header;
	break;
    }

    if (policy.has_payload) {
	csp_headers = [];
	const non_csp_headers = [];
	const header_list =
	      h => csp_header_regex.test(h) ? csp_headers : non_csp_headers;
	headers.forEach(h => header_list(h.name).push(h));
	headers = non_csp_headers;
    } else {
	headers.push(...csp_headers || []);
    }

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

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

    const policy_str = encodeURIComponent(JSON.stringify(policy));
    const signed_policy = sign_data(policy_str, new Date().getTime());
    const later_30sec = new Date(new Date().getTime() + 30000).toGMTString();
    headers.push({
	name: "Set-Cookie",
	value: `haketilo-${signed_policy.join("=")}; Expires=${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 haketilo_data = {csp_headers, policy_sig: signed_policy[0]};
    haketilo_data = encodeURIComponent(JSON.stringify(haketilo_data));
    haketilo_header.value = sign_data(haketilo_data, 0).join("_");

    if (!policy.allow) {
	headers.push({
	    name: "content-security-policy",
	    value: make_csp_rule(policy)
	});
    }

    return headers;
}

/*
 * EXPORTS_START
 * EXPORT inject_csp_headers
 * EXPORTS_END
 */