--[[
    client2server - Lua WebSocket Event Forwarder for OpenWrt
    
    Features:
    - WebSocket connection to central server
    - Auto-reconnect on disconnect
    - Local buffer (store-and-forward while offline)
    - DHCP/WiFi/Interface event tracking
    
    Copyright (c) 2026 Luis Rosales - MIT License
]]

-- ============================================================================
-- REQUIREMENTS
-- ============================================================================

-- Try to load websocket library, fallback to simple HTTP
local ws_client = nil
local has_websocket, websocket = pcall(require, "websocket")

if has_websocket then
    ws_client = websocket.client.sync()
end

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

local cfg = {
    url = os.getenv("SERVER_URL") or "wss://your-server.com/ws",
    token = os.getenv("SERVER_TOKEN") or "secret-token",
    router_id = os.getenv("ROUTER_ID") or "unknown",
    reconnect_delay = 5,
    ping_interval = 30,
    buffer_file = "/tmp/event_buffer",
    max_buffer = 100,
}

-- Load from UCI if available
pcall(function()
    local uci = require("luci.model.uci").cursor()
    cfg.url = uci:get("event-forwarder", "server", "url") or cfg.url
    cfg.token = uci:get("event-forwarder", "server", "token") or cfg.token
    cfg.router_id = uci:get("event-forwarder", "router", "id") or cfg.router_id
end)

-- ============================================================================
-- UTILITIES
-- ============================================================================

local function log(level, msg)
    os.execute(string.format('logger -t "client2server" -p user.%s "%s" 2>/dev/null', level, msg))
end

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

cfg.router_id = cfg.router_id == "unknown" and get_hostname() or cfg.router_id

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)))
        end
    end
    return "{" .. table.concat(parts, ",") .. "}"
end

-- ============================================================================
-- BUFFER (OFFLINE SUPPORT)
-- ============================================================================

local buffer = {
    events = {},
    dirty = false,
}

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 not buffer.dirty then 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()
    buffer.dirty = false
end

function buffer.add(json_event)
    table.insert(buffer.events, json_event)
    
    -- Trim if too big
    while #buffer.events > cfg.max_buffer do
        table.remove(buffer.events, 1)
    end
    
    buffer.dirty = true
    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)
            buffer.dirty = true
        else
            i = i + 1
        end
    end
    
    buffer.save()
end

function buffer.clear()
    buffer.events = {}
    os.execute("rm -f " .. cfg.buffer_file)
    buffer.dirty = false
end

-- ============================================================================
-- WEBSOCKET CLIENT
-- ============================================================================

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

function ws.connect(url)
    if not ws_client then
        log("err", "websocket library not installed")
        return nil
    end
    
    local ok, sock = pcall(ws_client.connect, ws_client, url)
    if ok then
        ws.sock = sock
        ws.connected = true
    end
    
    return ws.sock
end

function ws.send(sock, data)
    if not sock or not ws.connected then
        buffer.add(data)
        return false, "not connected"
    end
    
    local ok, err = pcall(sock.send, sock, data)
    if not ok then
        ws.connected = false
        buffer.add(data)
        return false, err
    end
    
    return true
end

function ws.close(sock)
    if sock then
        pcall(sock.close, sock)
    end
    ws.sock = nil
    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 = get_hostname(),
        event_type = event_type,
        payload = payload,
    })
end

-- ============================================================================
-- EVENT LISTENERS
-- ============================================================================

local function listen_dhcp()
    local lease_file = "/var/lib/dnsmasq/dnsmasq.leases"
    local old_leases = {}
    
    while true do
        local f = io.open(lease_file, "r")
        if f then
            local leases = {}
            
            for line in f:lines() do
                local ts, mac, ip, name = line:match("(%d+)%s+(%S+)%s+(%S+)%s+(%S+)")
                if mac then
                    leases[mac] = { ip = ip, hostname = name, time = tonumber(ts) }
                    
                    -- New lease?
                    if not old_leases[mac] then
                        local ev = build_event("dhcp_lease", {
                            mac = mac,
                            ip = ip,
                            hostname = name,
                            action = "new"
                        })
                        log("info", "DHCP: " .. mac .. " -> " .. ip)
                        buffer.add(ev)
                    end
                end
            end
            
            old_leases = leases
            f:close()
        end
        
        os.execute("sleep 5")
    end
end

local function poll_network()
    -- Poll network status
    local f = io.popen("ubus call network getStatus 2>/dev/null")
    if f then f:close() end
end

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

local function main()
    log("info", "client2server starting...")
    log("info", "Router: " .. cfg.router_id)
    log("info", "Server: " .. cfg.url)
    
    -- Load buffered events
    buffer.load()
    
    -- Save PID
    local pf = io.open("/var/run/client2server.pid", "w")
    if pf then
        pf:write(tostring(os.getpid()))
        pf:close()
    end
    
    local sock = nil
    local retries = 0
    
    -- Event listening coroutines
    -- In practice, would fork these or use procd/inotify
    
    while true do
        -- Attempt connection
        log("info", "Connecting to server...")
        
        if ws_client then
            sock = ws.connect(cfg.url)
        end
        
        if sock then
            log("info", "Connected!")
            retries = 0
            
            -- Flush buffer
            buffer.flush(function(data)
                return ws.send(sock, data)
            end)
            
            -- Keep alive loop
            local loop_count = 0
            while ws.connected and loop_count < (cfg.ping_interval / 5) do
                os.execute("sleep 5")
                loop_count = loop_count + 1
                
                -- Periodic flush
                buffer.flush(function(data)
                    return ws.send(sock, data)
                end)
            end
        else
            log("err", "Connection failed")
            retries = retries + 1
        end
        
        -- Cleanup and reconnect
        ws.close(sock)
        sock = nil
        
        log("info", "Reconnecting in " .. cfg.reconnect_delay .. "s...")
        os.execute("sleep " .. cfg.reconnect_delay)
    end
end

-- Run
main()