--[[
    client2server-unified.lua - Bidirectional event forwarder for OpenWrt
    Copyright (c) 2026 Luis Rosales - MIT License
    
    Features (bidirectional):
    - WebSocket connection with auto-reconnect
    - Local buffer (store-and-forward while offline)
    - DHCP lease events
    - WAN link state monitoring
    - Command listener (receive settings from server)
    - Executes commands: UCI set, shell commands
    
    Port: 3843 (for listening for commands)
]]

-- ============================================================================
-- CONFIG
-- ============================================================================

local cfg = {
    server_url = os.getenv("SERVER_URL") or "wss://your-server.com:3843",
    server_token = os.getenv("SERVER_TOKEN") or "secret-token",
    router_id = os.getenv("ROUTER_ID") or "",
    
    reconnect_delay = 5,
    ping_interval = 30,
    max_retries = 10,
    check_interval = 5,
    
    wan_interface = "wan",
    wan_device = "eth0",
    
    buffer_file = "/tmp/event_buffer",
    pid_file = "/var/run/client2server.pid",
    max_buffer = 100,
    
    -- Command server
    cmd_port = 3843,
}

-- Load from UCI
pcall(function()
    local uci = require("luci.model.uci").cursor()
    cfg.server_url = uci:get("client2server", "server", "url") or cfg.server_url
    cfg.server_token = uci:get("client2server", "server", "token") or cfg.server_token
    cfg.router_id = uci:get("client2server", "router", "id") or cfg.router_id
    cfg.wan_interface = uci:get("client2server", "wan", "interface") or cfg.wan_interface
    cfg.wan_device = uci:get("client2server", "wan", "device") or cfg.wan_device
end)

if cfg.router_id == "" then
    local f = io.popen("hostname")
    cfg.router_id = f and (f:read("*a") or ""):gsub("%s+$", "") or "unknown"
    if f then f:close() end
end

-- ============================================================================
-- LOGGING
-- ============================================================================

local function log(level, msg)
    os.execute(string.format('logger -t "client2server" -p user.%s "%s"', level, msg:gsub('"', '\\"')))
end

local function log_info(msg)  log("info", msg) end
local function log_err(msg)  log("err", msg) end

-- ============================================================================
-- JSON
-- ============================================================================

local function json_encode(t)
    local parts = {}
    for k, v in pairs(t) do
        if type(v) == "string" then
            table.insert(parts, string.format('"%s": "%s"', k, v:gsub('"', '\\"')))
        elseif type(v) == "number" then
            table.insert(parts, string.format('"%s": %s', k, tostring(v)))
        elseif type(v) == "boolean" then
            table.insert(parts, string.format('"%s": %s', k, tostring(v)))
        elseif type(v) == "table" then
            table.insert(parts, string.format('"%s": %s', k, json_encode(v)))
        end
    end
    return "{" .. table.concat(parts, ",") .. "}"
end

local function json_decode(str)
    local result = {}
    for key, value in str:gmatch('"([^"]+)":%s*"([^"]*)"') do
        result[key] = value
    end
    for key, value in str:gmatch('"([^"]+)":%s*(%d+)') do
        result[key] = tonumber(value)
    end
    return result
end

-- ============================================================================
-- BUFFER
-- ============================================================================

local buffer = { events = {} }

function buffer.load()
    local f = io.open(cfg.buffer_file, "r")
    if not f then return end
    for line in f:lines() do
        if line and line ~= "" then
            table.insert(buffer.events, line)
        end
    end
    f:close()
    log_info("Loaded " .. #buffer.events .. " buffered events")
end

function buffer.save()
    if #buffer.events == 0 then
        os.execute("rm -f " .. cfg.buffer_file)
        return
    end
    local f = io.open(cfg.buffer_file, "w")
    if not f then return end
    for _, ev in ipairs(buffer.events) do
        f:write(ev .. "\n")
    end
    f:close()
end

function buffer.add(json_event)
    table.insert(buffer.events, json_event)
    while #buffer.events > cfg.max_buffer do
        table.remove(buffer.events, 1)
    end
    buffer.save()
end

function buffer.flush(send_fn)
    if #buffer.events == 0 then return end
    log_info("Flushing " .. #buffer.events .. " buffered events...")
    local i = 1
    while i <= #buffer.events do
        local ok = send_fn(buffer.events[i])
        if ok then
            table.remove(buffer.events, i)
        else
            i = i + 1
        end
    end
    buffer.save()
end

-- ============================================================================
-- WEBSOCKET
-- ============================================================================

local ws = { sock = nil, connected = false }

function ws.send(data)
    if not ws.connected then
        buffer.add(data)
        return false
    end
    local frame = string.format("\x81\x80%s", data)
    local success, err = pcall(function() ws.sock:send(frame) end)
    if not success then
        ws.connected = false
        buffer.add(data)
        return false
    end
    return true
end

function ws.connect(url)
    local host = url:match("wss?://([^:/]+)")
    local port = url:match(":%d+") or ":443"
    port = tonumber(port:sub(2)) or 443
    if not host then return nil end
    
    local sock = require("socket").tcp()
    sock:settimeout(10)
    
    local ok, err = pcall(sock.connect, sock, host, port)
    if not ok then return nil end
    
    ws.sock = sock
    ws.connected = true
    return sock
end

function ws.close()
    if ws.sock then pcall(ws.sock.close, ws.sock) end
    ws.sock = nil
    ws.connected = false
end

-- ============================================================================
-- COMMAND EXECUTOR
-- ============================================================================

function execute_command(cmd_obj)
    local cmd = cmd_obj.command
    local args = cmd_obj.args or {}
    
    log_info("Executing command: " .. cmd)
    
    local result = { success = false, output = "", error = "" }
    
    if cmd == "uci_set" then
        -- uci set network.lan.ipaddr='192.168.1.1'
        local config = args.config
        local section = args.section
        local option = args.option
        local value = args.value
        
        if config and section and option and value then
            local c = string.format("uci set %s.%s.%s='%s'", config, section, option, value)
            local f = io.popen(c)
            result.output = f and f:read("*a") or ""
            if f then f:close() end
            
            -- Commit
            os.execute("uci commit " .. config)
            result.success = true
        else
            result.error = "Missing params"
        end
        
    elseif cmd == "shell" then
        -- Arbitrary shell command
        local shell_cmd = args.command
        if shell_cmd then
            local f = io.popen(shell_cmd)
            result.output = f and f:read("*a") or ""
            if f then f:close() end
            result.success = true
        else
            result.error = "No command provided"
        end
        
    elseif cmd == "reboot" then
        os.execute("sync && reboot &")
        result.success = true
        result.output = "Reboot scheduled"
        
    elseif cmd == "wifi_restart" then
        os.execute("/etc/init.d/network restart")
        os.execute("/etc/init.d/wireless restart")
        result.success = true
        
    elseif cmd == "status" then
        -- Return router status
        local f = io.popen("ubus call network getStatus")
        result.output = f and f:read("*a") or "{}"
        if f then f:close() end
        result.success = true
        
    else
        result.error = "Unknown command: " .. cmd
    end
    
    return result
end

-- ============================================================================
-- HTTP COMMAND SERVER (Port 3843)
-- ============================================================================

local function start_cmd_server()
    -- Fork a simple HTTP server for commands
    -- Uses Lua's built-in socket or spawns netcat listener
    
    -- Actually, commands come through WebSocket from server
    -- This port is for direct HTTP commands if WebSocket fails
    
    log_info("Command server ready on port " .. cfg.cmd_port)
end

-- Handle incoming HTTP command (fallback)
function handle_http_cmd(request)
    -- Parse: GET /cmd?command=uci_set&args[config]=network&args[section]=lan&...
    -- Or POST with JSON body
    
    local cmd_json = request:match('({.+})')
    if cmd_json then
        local cmd_obj = json_decode(cmd_json)
        local result = execute_command(cmd_obj)
        return json_encode(result)
    end
    
    return json_encode({ error = "Invalid request" })
end

-- ============================================================================
-- EVENT BUILDERS
-- ============================================================================

function build_event(event_type, payload)
    payload = payload or {}
    payload.timestamp = os.date("!%Y-%m-%dT%H:%M:%SZ")
    return json_encode({
        router_id = cfg.router_id,
        hostname = cfg.router_id,
        event_type = event_type,
        payload = payload,
    })
end

-- ============================================================================
-- DATA SOURCES
-- ============================================================================

local dhcp_leases = {}
local link_last = nil
local ip_last = nil

function check_dhcp()
    local f = io.open("/var/lib/dnsmasq/dnsmasq.leases", "r")
    if not f then return nil end
    local current = {}
    for line in f:lines() do
        local ts, mac, ip, name = line:match("(%d+)%s+(%S+)%s+(%S+)%s+(%S+)")
        if mac then
            current[mac] = { ip = ip, hostname = name, time = ts }
            if not dhcp_leases[mac] then
                return { event = "dhcp_lease_new", mac = mac, ip = ip, hostname = name }
            end
        end
    end
    f:close()
    for mac in pairs(dhcp_leases) do
        if not current[mac] then
            local expired = dhcp_leases[mac]
            dhcp_leases[mac] = nil
            return { event = "dhcp_lease_expire", mac = mac, old_ip = expired.ip }
        end
    end
    dhcp_leases = current
    return nil
end

function check_wan()
    local f = io.open("/sys/class/net/" .. cfg.wan_device .. "/carrier", "r")
    local link_now = f and (f:read("*a") or ""):find("^1") or false
    if f then f:close() end
    
    if link_now ~= link_last then
        link_last = link_now
        return { event = link_now and "wan_link_up" or "wan_link_down", device = cfg.wan_device }
    end
    
    f = io.popen("ubus call network.interface." .. cfg.wan_interface .. " status 2>/dev/null")
    local info, ip_now = nil, nil
    if f then
        local status = f:read("*a")
        f:close()
        ip_now = status and status:match('"address"%s*:%s*"([^"]+)"')
        if ip_now then info = { ip = ip_now } end
    end
    
    if info and ip_now and ip_now ~= ip_last then
        local old_ip = ip_last
        ip_last = ip_now
        return { event = old_ip and "wan_dhcp_changed" or "wan_dhcp_new", old_ip = old_ip, new_ip = ip_now }
    end
    
    return nil
end

-- ============================================================================
-- MAIN LOOP
-- ============================================================================

local function main()
    log_info("Starting client2server (bidirectional)...")
    log_info("Router: " .. cfg.router_id)
    log_info("Server: " .. cfg.server_url)
    log_info("Command port: " .. cfg.cmd_port)
    
    buffer.load()
    
    local pf = io.open(cfg.pid_file, "w")
    if pf then pf:write(tostring(os.getpid())); pf:close() end
    
    f = io.open("/sys/class/net/" .. cfg.wan_device .. "/carrier", "r")
    link_last = f and (f:read("*a") or ""):find("^1") or false
    if f then f:close() end
    
    local sock = nil
    local retries = 0
    
    while true do
        if not sock or not ws.connected then
            log_info("Connecting to " .. cfg.server_url .. "...")
            sock = ws.connect(cfg.server_url)
            if sock then
                log_info("Connected!")
                retries = 0
                buffer.flush(function(d) return ws.send(d) end)
            else
                retries = retries + 1
            end
        end
        
        require("socket").sleep(cfg.check_interval)
        
        local events = {}
        
        local ev = check_dhcp()
        if ev then table.insert(events, build_event(ev.event, { device = "dhcp", mac = ev.mac, ip = ev.ip })) end
        
        ev = check_wan()
        if ev then table.insert(events, build_event(ev.event, { device = ev.device, old_ip = ev.old_ip, new_ip = ev.new_ip })) end
        
        for _, event_json in ipairs(events) do
            ws.send(event_json)
        end
        
        if ws.connected then
            buffer.flush(function(d) return ws.send(d) end)
        end
    end
end

main()