--[[
    client2server-unified.lua - All-in-one event forwarder for OpenWrt
    Copyright (c) 2026 Luis Rosales - MIT License
    
    Combines:
    - client2server: DHCP/WiFi events → WebSocket
    - wan-watcher: WAN link + DHCP monitoring
    
    Features:
    - WebSocket connection with auto-reconnect
    - Local buffer (store-and-forward while offline)
    - DHCP lease events
    - WAN link state monitoring
    - DHCP lease changes (new ISP detection)
    
    Size: ~15KB (shared codebase, no duplication)
]]

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

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

-- Load from UCI if available
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)

-- Set router_id from hostname if not set
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 (Minimal implementation)
-- ============================================================================

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
            -- Nested object
            table.insert(parts, string.format('"%s": %s', k, json_encode(v)))
        end
    end
    return "{" .. table.concat(parts, ",") .. "}"
end

-- ============================================================================
-- BUFFER (Offline Support)
-- ============================================================================

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()
    log_info("Flush complete, " .. #buffer.events .. " remaining")
end

-- ============================================================================
-- WEBSOCKET (Simplified)
-- ============================================================================

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

function ws.send(data)
    if not ws.connected then
        buffer.add(data)
        return false
    end
    
    -- Simple frame construction
    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)
    -- Extract host from wss://... URL
    local host = url:match("wss?://([^/]+)")
    if not host then return nil end
    
    local sock = require("socket").tcp()
    sock:settimeout(10)
    
    local ok, err = pcall(sock.connect, sock, host, 443)
    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)
        ws.sock = nil
    end
    ws.connected = false
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
-- ============================================================================

-- DHCP Leases
local dhcp_leases = {}

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
                -- NEW lease
                log_info("DHCP new: " .. mac .. " -> " .. ip)
                return {
                    event = "dhcp_lease_new",
                    mac = mac,
                    ip = ip,
                    hostname = name,
                }
            end
        end
    end
    f:close()
    
    -- Check for expired leases
    for mac in pairs(dhcp_leases) do
        if not current[mac] then
            local expired = dhcp_leases[mac]
            log_info("DHCP expire: " .. mac)
            dhcp_leases[mac] = nil
            return {
                event = "dhcp_lease_expire",
                mac = mac,
                old_ip = expired.ip,
            }
        end
    end
    
    dhcp_leases = current
    return nil
end

-- WAN Link State
local link_last = nil
local ip_last = nil

function check_wan()
    -- Physical link
    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
    
    -- Link change
    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,
            message = link_now and "Physical link detected" or "Physical link lost",
        }
    end
    
    -- Check DHCP IP via ubus
    local info = nil
    f = io.popen("ubus call network.interface." .. cfg.wan_interface .. " status 2>/dev/null")
    if f then
        local status = f:read("*a")
        f:close()
        if status then
            local ip = status:match('"address"%s*:%s*"([^"]+)"')
            if ip then info = { ip = ip } end
        end
    end
    
    -- IP change (connected to new network)
    if info and info.ip and info.ip ~= ip_last then
        local old_ip = ip_last
        ip_last = info.ip
        
        return {
            event = old_ip and "wan_dhcp_changed" or "wan_dhcp_new",
            device = cfg.wan_interface,
            old_ip = old_ip,
            new_ip = info.ip,
            message = old_ip and ("IP changed: " .. old_ip .. " -> " .. info.ip) or ("New IP: " .. info.ip),
        }
    end
    
    return nil
end

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

local function main()
    log_info("Starting client2server-unified...")
    log_info("Router: " .. cfg.router_id)
    log_info("Server: " .. cfg.server_url)
    log_info("WAN: " .. cfg.wan_interface .. " (" .. cfg.wan_device .. ")")
    
    -- Load buffer
    buffer.load()
    
    -- Save PID
    local pf = io.open(cfg.pid_file, "w")
    if pf then
        pf:write(tostring(os.getpid()))
        pf:close()
    end
    
    -- Initial WAN state
    local 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
    
    -- Main loop with periodic checks
    local sock = nil
    local retries = 0
    local check_counter = 0
    
    while true do
        -- Attempt connection if not connected
        if not sock or not ws.connected then
            log_info("Connecting...")
            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
                if retries >= cfg.max_retries then
                    log_err("Max retries, resetting")
                    retries = 0
                end
            end
        end
        
        socket.sleep(cfg.check_interval)
        check_counter = check_counter + 1
        
        -- Check every cycle
        local events = {}
        
        -- 1. DHCP
        local ev = check_dhcp()
        if ev then table.insert(events, build_event(ev.event, {
            device = "dhcp",
            mac = ev.mac,
            ip = ev.ip,
            hostname = ev.hostname,
            old_ip = ev.old_ip,
        }) end
        
        -- 2. WAN (every cycle)
        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
        
        -- Send buffered + current events
        for _, event_json in ipairs(events) do
            log_info("Event: " .. event_json)
            ws.send(event_json)
        end
        
        -- Also flush any pending buffered
        if ws.connected then
            buffer.flush(function(d) return ws.send(d) end)
        end
    end
end

main()