/*
 * SPDX-License-Identifier: GPL-2.0-only
 *
 *     generator/common.uc: shared helpers used by every generator module.
 *
 * Every "select a tag from a UCI-style reference" function lives in this
 * file because the same selector logic (a routing_node name, an
 * array-of-names, a direct/block/default marker, a ruleset id list) is
 * reached by the DNS section, the route section, the outbound/endpoint
 * builder and the ruleset section. Duplicating them per-module would
 * drift; consolidating them here keeps the convention "one place to
 * change a tag shape".
 *
 * The Loader owns UCI; nothing in here reads UCI directly. The orchestrator
 * passes `dm` for the routing_node lookups that need to resolve a name into
 * the underlying node id.
 */

'use strict';

import { isEmpty, HP_DIR } from '../homeproxy-pro.uc';

import { ConfigQuery } from '../config/model.uc';

/* parse_port() lives in homeproxy-pro.uc. The Adapter layer needs it
 * too (EndpointFactory builds the WireGuard endpoint) and an adapter must
 * not import from generator/, so the util moved to the module both layers
 * already share. Callers import it from '../homeproxy-pro.uc' now. */

/* Resolve a UCI outbound-style reference (string or array of strings)
 * into the sing-box tag the generator should emit. The arrays carry
 * either 'block-out' / 'direct-out' sentinels or routing_node section
 * names; a single string is the same thing with one entry.
 *
 * `dm` is needed for the routing_node -> node id lookup; we deliberately
 * do not read `dm.routing.nodes` until we know we need it (the common
 * case is the sentinel). */
export function get_outbound(cfg, dm) {
	if (isEmpty(cfg))
		return null;

	if (type(cfg) === 'array') {
		let outbounds = [];
		for (let i in cfg)
			push(outbounds, get_outbound(i, dm));
		return outbounds;
	}

	switch (cfg) {
	case 'block-out':
	case 'direct-out':
		return cfg;
	default:
		const rn = ConfigQuery.find_by_name(dm.routing.nodes, cfg);
		if (!rn || isEmpty(rn.node))
			die(sprintf("%s's node is missing, please check your configuration.", cfg));
		else if (rn.node === 'urltest')
			return 'cfg-' + cfg + '-out';
		else
			return 'cfg-' + rn.node + '-out';
	}
};

/* Find a loaded section by name, treating `enabled` as a gate. The Loader
 * normalises `enabled` on every list section; a section with the field unset
 * is enabled (boolean sections default to 0 in UCI, but a dns_server/ruleset
 * without the option is a valid, enabled row).
 *
 * Declared before its callers on purpose: ucode resolves function references
 * at call time from what has already been evaluated, so a `function` statement
 * placed after get_resolver() fails with "access to undeclared variable". */
function find_enabled(items, name) {
	const item = ConfigQuery.find_by_name(items || [], name);
	if (!item)
		return null;
	if (item.enabled === false || item.enabled === '0')
		return null;
	return item;
};

/* Resolve a UCI resolver reference (a dns_server section name or one of
 * the sentinels) into a sing-box resolver tag.
 *
 * `dm` is required for the same reason get_outbound() needs it: a reference to
 * a section that was deleted or disabled produces `cfg-<name>-dns`, which
 * nothing defines - sing-box then rejects the whole configuration with
 * "dns server not found", the reload silently keeps the previous one, and the
 * user only sees that their change did not take. Fail with the name instead. */
export function get_resolver(cfg, dm) {
	if (isEmpty(cfg))
		return null;

	switch (cfg) {
	case 'default-dns':
	case 'system-dns':
		return cfg;
	default:
		if (dm && !find_enabled((dm.dns || {}).servers, cfg))
			die(sprintf("the DNS server '%s' does not exist or is disabled; check the rule that refers to it.", cfg));
		return 'cfg-' + cfg + '-dns';
	}
};

/* Resolve a UCI ruleset reference list (array of ruleset section names)
 * into the corresponding sing-box rule_set tag list. Same existence gate as
 * get_resolver(): ruleset.uc skips disabled entries, so a reference to one
 * would leave a dangling `cfg-<name>-rule` tag behind. */
export function get_ruleset(cfg, dm) {
	if (isEmpty(cfg))
		return null;

	let rules = [];
	for (let i in cfg) {
		if (isEmpty(i))
			continue;
		if (dm && !find_enabled((dm.routing || {}).rulesets, i))
			die(sprintf("the rule-set '%s' does not exist or is disabled; check the rule that refers to it.", i));
		push(rules, 'cfg-' + i + '-rule');
	}
	return rules;
};

/* rule_set_tags(cfg) - the rule_set tags ONE `dm.routing.rulesets` section
 * produces: `cfg-<name>-rule`, plus one per entry in extra_tags.
 *
 * The generator needs it to build the tag; the CLI's environment resolution
 * needs it too, because a `{tag}` placeholder in a source path has to be
 * expanded to the real per-tag files before their existence can be checked.
 * Two copies of this list would be free to drift, and the failure mode is
 * quiet: the pre-check would stat files the running configuration never
 * names, and a genuinely missing one would go unreported.
 *
 * Declared after get_ruleset() but before its callers for the same reason that
 * function carries its own note: ucode resolves references at call time from
 * what has already been evaluated. */
export function rule_set_tags(cfg) {
	const tags = [ 'cfg-' + cfg.name + '-rule' ];

	for (let t in (cfg.extra_tags || []))
		push(tags, 'cfg-' + t + '-rule');

	return tags;
};

/* The routing modes that split on mainland China, and the rule-sets they
 * declare.
 *
 * The three of them - china-ip, china-ip6, china-domain - are local files the
 * resource updater generates, one per list, and each is declared only when
 * something references it and its file is on disk.  route.uc owns that
 * decision because the conditions are per-tag (the address list in both
 * mainland modes, the v6 half only with IPv6 on, the domain list only in
 * bypass mode), so there is nothing here for a shared list to keep in step
 * with.
 *
 * They were `type: remote` entries pointing at SagerNet's sing-geoip and
 * sing-geosite repositories, and two things followed from that which the local
 * arrangement does not have:
 *
 *   - a cold start had to download them before the inbounds bind, over the
 *     node (download_detour), so a first start - or a start after the cache
 *     was cleared - depended on GitHub being reachable through the proxy it
 *     was trying to bring up;
 *   - the two halves of the same split read two different files.  The kernel's
 *     came from china_ip4.txt and the resolver's from a .srs, and the route.uc
 *     comment about them disagreeing is the scar of patching that instead of
 *     fixing it.
 *
 * Now the nft set and the sing-box rule-set are both generated from the same
 * list, on the same schedule, with nothing to download.
 *
 * Source JSON, not a compiled .srs: the updater writes the canonical form and
 * sing-box watches the file, so a new list is picked up in place.  Compiling
 * first was measured rather than assumed - 111k domain suffixes cost 3.7 MB of
 * RSS in source form (44.9 MB baseline vs 48.7 MB loaded), which is not worth
 * a second artifact and a second failure mode. */
/* The routing modes that split on mainland China.  The China domain list is
 * only meaningful where the split is by domain: proxy_mainland_china decides
 * by address on the route side and leaves the resolver to the mode default. */
export function declaresBuiltinRuleSets(routing_mode) {
	return routing_mode === 'bypass_mainland_china' || routing_mode === 'proxy_mainland_china';
};

/* Resolve the direct-node destination override that the route builder
 * needs for a `direct` routing_node target. The override is recorded
 * earlier by generate_outbound() (see outbound.uc) when a direct node
 * carries override_address / override_port; this helper just looks it
 * up. Returns null when the target is not a direct node or no override
 * is configured. */
export function get_direct_override(outbound_selector, dm, direct_overrides) {
	if (type(outbound_selector) === 'array' || isEmpty(outbound_selector))
		return null;

	switch (outbound_selector) {
	case 'direct-out':
	case 'block-out':
		return null;
	default:
		const rn = ConfigQuery.find_by_name(dm.routing.nodes, outbound_selector);
		const node = rn && rn.node;
		return (!isEmpty(node) && node !== 'urltest') ? (direct_overrides[node] || null) : null;
	}
};

/* True when `tag` (the sing-box outbound tag) belongs to a direct outbound.
 * Used by the http_clients builder to drop the detour field on a pure-TUN
 * setup: sing-box 1.14 rejects detouring to a direct outbound that has
 * nothing to detour through. */
export function isDirectOutboundTag(tag, dm) {
	if (isEmpty(tag) || tag === 'block-out')
		return false;
	if (tag === 'direct-out')
		return true;

	/* The caller passes the tag the generator emits - get_outbound() builds
	 * `cfg-<node>-out` - not the routing_node section name, so that wrapper has
	 * to be undone before the lookup.  Without this the two queries below were
	 * given a name that matches neither table, and the function returned false
	 * for every routing_node: build_http_clients() then kept a `detour` on a
	 * rule-set download in pure TUN mode, where sing-box refuses it ("detour to
	 * an empty direct outbound makes no sense") and rejects the whole
	 * configuration. */
	const unwrapped = match(tag, /^cfg-(.+)-out$/);
	const name = unwrapped ? unwrapped[1] : tag;

	const rn = ConfigQuery.find_by_name(dm.routing.nodes, name);
	const node_name = (rn && rn.node) || name;
	const node = ConfigQuery.node_by_id(dm, node_name);
	return !!(node && node.type === 'direct');
};

/* Append the sing-box JSON $schema field. Kept here because the value is
 * fixed and the two generators used to spell it the same way; if it ever
 * changes, both should pick up the new URL automatically. */
export function attachSchema(config) {
	config['$schema'] = 'https://sing-box.sagernet.org/schema.json';
	return config;
};

/* Attach the experimental cache_file block. Every routing mode benefits
 * from it: bypass_mainland_china and custom match a lot of DNS, and the
 * other modes still resolve the proxy node hostname and resolve any
 * domain the user clicks through. cache_file is a no-op on a fresh
 * install (no cache to read) and the file is the only piece of state the
 * generator writes outside /etc/config/homeproxy-pro.  Routing-mode gating
 * used to limit it to bypass_mainland_china + custom, which left
 * gfwlist / proxy_mainland_china / global with cold-start DNS on every
 * reload and made the difference between modes hard to explain.
 *
 * Note: the reference configuration this was compared against asked for an
 * explicit `reverse_mapping: true` here (so a future sing-box change to
 * the default would not silently move us off the mapping table). The
 * sing-box 1.14.0-r1 we test against rejects that field as
 * "json: unknown field" - the field is recognised by newer builds but
 * not the floor pinned by arch-guard 31. sing-box's default is already
 * `true`, so leaving it implicit matches runtime behaviour and keeps the
 * generated config compatible with the test target. Revisit if the
 * floor moves past the release where the field was introduced. */
export function attachExperimental(config, routing_mode, dns_store_dns) {
	config.experimental = {
		cache_file: {
			enabled: true,
			path: '/etc/homeproxy-pro/cache.db',
			store_dns: (dns_store_dns === '1') ? true : null
		}
	};
	return config;
};