'use strict';

let uci = require('uci');
let fs = require('fs');

const SWITCH_SCRIPT  = '/usr/sbin/zt-gateway-switch';
const DRAIN_PIDFILE  = '/var/run/zt-gateway-drain.pid';
const DRAIN_NEWFILE  = '/var/run/zt-gateway-drain.new';
const DRAIN_OLDFILE  = '/var/run/zt-gateway-drain.old';

function load_gateways() {
	const cursor = uci.cursor();
	const result = [];
	cursor.foreach('zt-gateway', 'gateway', function(s) {
		push(result, {
			region: s.region ?? '',
			label:  s.label ?? s.region ?? '',
			ip:     s.ip ?? '',
			default: s.default === '1',
			health_check: s.health_check ?? 'ping'
		});
	});
	return result;
}
function gateway_by_region(region) {
	const gws = load_gateways();
	for (let i = 0; i < length(gws); i++) {
		if (gws[i].region === region) {
			return gws[i];
		}
	}
	return null;
}

function read_active_region() {
	const cursor = uci.cursor();
	return cursor.get('zt-gateway', 'global', 'active_gateway') ?? '';
}

function read_global_option(option, default_value) {
	const cursor = uci.cursor();
	return cursor.get('zt-gateway', 'global', option) ?? default_value;
}

function drain_active() {
	const st = fs.stat(DRAIN_PIDFILE);
	return st?.type === 'file';
}

function read_drain_pid() {
	const data = fs.readfile(DRAIN_PIDFILE);
	if (!data) {
		return null;
	}
	const s = trim(data);
	return length(s) > 0 ? +s : null;
}

function read_drain_state() {
	let new_ip = '';
	let old_ip = '';
	const n = fs.readfile(DRAIN_NEWFILE);
	if (n) {
		new_ip = trim(n);
	}
	const o = fs.readfile(DRAIN_OLDFILE);
	if (o) {
		old_ip = trim(o);
	}
	return { new_ip, old_ip };
}


function shell_quote(s) {
	if (!s) {
		return "''";
	}
	if (match(s, /^[A-Za-z0-9_./:@=-]+$/) != null) {
		return s;
	}
	return `'${replace(s, "'", "'\\''")}'`;
}

function run_switch_script_capture(ip, mode) {
	const mode_lc = mode ?? 'force';
	let cmd = `${SWITCH_SCRIPT} ${shell_quote(ip)} ${shell_quote(mode_lc)}`;
	if (mode_lc === 'graceful') {
		const to = +read_global_option('drain_timeout', '600');
		cmd += ` ${to > 0 ? to : 600}`;
	}
	const stderr_pipe = '/tmp/zt-gw-stderr';
	const code = system(`${cmd} 2>${stderr_pipe}`);
	const err = fs.readfile(stderr_pipe) ?? '';
	fs.unlink(stderr_pipe);
	return { code: code ?? 0, stderr: trim(err) };
}

function run_switch_script_force_capture(ip) {
	const stderr_pipe = '/tmp/zt-gw-stderr';
	const code = system(`${SWITCH_SCRIPT} ${shell_quote(ip)} force 2>${stderr_pipe}`);
	const err = fs.readfile(stderr_pipe) ?? '';
	fs.unlink(stderr_pipe);
	return { code: code ?? 0, stderr: trim(err) };
}

function system_output(cmd) {
	const tmp = `/tmp/zt-gw-out-${time()}`;
	system(`${cmd} >${tmp} 2>/dev/null`);
	const out = fs.readfile(tmp) ?? '';
	fs.unlink(tmp);
	return out;
}

return {
	'zt-gateway': {
		status: {
			call: function(req) {
				const gws = load_gateways();
				const active_region = read_active_region();

				let active_ip = '';
				const active_gw = gateway_by_region(active_region);
				if (active_gw) {
					active_ip = active_gw.ip;
				}

				const drain_state = read_drain_state();
				let remaining = 0;
				if (drain_active()) {
					const out = system_output(`conntrack -L -m 0x100 2>/dev/null | wc -l`);
					remaining = +trim(out) || 0;
				}

				const cursor = uci.cursor();
				const settings = {
					switch_mode: cursor.get('zt-gateway', 'global', 'switch_mode') ?? 'force',
					drain_timeout: +(cursor.get('zt-gateway', 'global', 'drain_timeout') ?? 600),
					health_interval: +(cursor.get('zt-gateway', 'global', 'health_interval') ?? 60),
					auto_failback: cursor.get('zt-gateway', 'global', 'auto_failback') === '1'
				};

				return {
					active_gateway: active_region,
					active_ip: active_ip,
					settings: settings,
					gateways: gws,
					drain: {
						active: drain_active(),
						new_ip: drain_state.new_ip,
						old_ip: drain_state.old_ip,
						remaining_connections: remaining
					}
				};
			}
		},

		switch: {
			args: {
				region: 'string',
				mode: 'string'
			},
			call: function(req) {
				const region = req.args?.region;
				const mode = req.args?.mode ?? read_global_option('switch_mode', 'force');
				if (!region || (mode !== 'force' && mode !== 'graceful')) {
					return {
						success: false,
						message: 'Missing or invalid argument: region required, mode must be force|graceful'
					};
				}

				if (drain_active() && mode === 'graceful') {
					return {
						success: false,
						message: 'A graceful drain is already in progress. Cancel it first.'
					};
				}

				const gw = gateway_by_region(region);
				if (!gw) {
					return { success: false, message: `Unknown gateway region: ${region}` };
				}


				const result = run_switch_script_capture(gw.ip, mode);
				if (result.code !== 0) {
					return {
						success: false,
						message: result.stderr || `Switch script failed with exit code ${result.code}`
					};
				}

				const cursor = uci.cursor();
				cursor.set('zt-gateway', 'global', 'active_gateway', region);
				cursor.commit('zt-gateway');

				return {
					success: true,
					message: `Switched to ${region} (${gw.ip}) via ${mode}`,
					active_gateway: region,
					mode: mode,
					drain_active: (mode === 'graceful')
				};
			}
		},

		health: {
			args: {
				region: 'string'
			},
			call: function(req) {
				const region = req.args?.region;
				if (!region) {
					return { reachable: false, message: 'Missing region' };
				}

				const gw = gateway_by_region(region);
				if (!gw) {
					return { reachable: false, message: `Unknown region ${region}` };
				}

				const out = system_output(
					`ping -c 2 -W 3 -I br-zt ${shell_quote(gw.ip)} 2>/dev/null; echo "EXIT:$?"`
				);
				const exit_match = match(out, /EXIT:(\d+)/);
				const exit_code = exit_match ? +exit_match[1] : 1;

				let latency_ms = null;
				if (exit_code === 0) {
					const stats = match(out, /rtt min\/avg\/max[^=]*=\s*[\d.]+\/([\d.]+)\//);
					if (stats) {
						latency_ms = +stats[1];
					}
				}

				return {
					region: region,
					ip: gw.ip,
					reachable: exit_code === 0,
					latency_ms: latency_ms
				};
			}
		},

		drain_status: {
			call: function(req) {
				const active = drain_active();
				const state = read_drain_state();
				let remaining = 0;
				if (active) {
					const out = system_output(`conntrack -L -m 0x100 2>/dev/null | wc -l`);
					remaining = +trim(out) || 0;
				}
				return {
					active: active,
					new_ip: state.new_ip,
					old_ip: state.old_ip,
					remaining_connections: remaining
				};
			}
		},

		cancel_drain: {
			call: function(req) {
				if (!drain_active()) {
					return { success: false, message: 'No drain in progress' };
				}

				const state = read_drain_state();
				const pid = read_drain_pid();
				if (pid) {
					system(`kill -TERM ${pid} 2>/dev/null`);
				}

				if (!state.new_ip) {
					fs.unlink(DRAIN_PIDFILE);
					return {
						success: true,
						message: 'Drain cancelled (new gateway unknown; route left as-is).'
					};
				}

				const result = run_switch_script_force_capture(state.new_ip);

				fs.unlink(DRAIN_PIDFILE);
				fs.unlink(DRAIN_NEWFILE);
				fs.unlink(DRAIN_OLDFILE);

				return {
					success: result.code === 0,
					message: result.code === 0
						? `Drain cancelled; force-switched to ${state.new_ip}.`
						: (result.stderr || `Cancel failed with code ${result.code}`)
				};
			}
		},

		setup: {
			args: {
				command: 'string'
			},
			call: function(req) {
				const command = req.args?.command;
				if (!command || !match(command, /^(status|setup-bridge|setup-routing|setup-dhcp|setup-wifi-ap|setup-hotplug|setup-persistence|setup-all)$/)) {
					return {
						success: false,
						message: 'Invalid command. Valid: status, setup-bridge, setup-routing, setup-dhcp, setup-wifi-ap, setup-hotplug, setup-persistence, setup-all'
					};
				}

				const stderr_pipe = '/tmp/zt-gw-setup-stderr';
				const code = system(`/usr/sbin/zt-gateway-setup ${shell_quote(command)} 2>${stderr_pipe}`);
				const err = fs.readfile(stderr_pipe) ?? '';
				fs.unlink(stderr_pipe);

				if (code !== 0) {
					return {
						success: false,
						message: trim(err) || `Setup failed with exit code ${code}`
					};
				}

				return {
					success: true,
					message: trim(err) || `${command} completed successfully`,
					command: command
				};
			}
		}
	}
};