--[[
    event-forwarder.lua - WebSocket-based event forwarder for OpenWrt
    Copyright (c) 2026 Luis Rosales - MIT License
    Size: ~30KB with dependencies
]]

local socket = require("socket")
local http = require("socket.http")
local ltn12 = require("ltn12")
local json = require("json")

-- ============================================================================
-- CONFIGURATION
-- ============================================================================

local config = {
    server_url = "wss://your-server.com/ws",
    server_token = "CHANGE_ME",
    router_id = "",
    reconnect_delay = 5,
    max_retries = 10,
    ping_interval = 30,
    
    -- File paths
    buffer_file = "/tmp/event_buffer",
    pid_file = "/var/run/event-forwarder.pid",
    
    -- Event sources
    events = {
        wifi_connect = true,
        wifi_disconnect = true,
        dhcp_lease = true,
        interface_up = true,
        interface_down = true,
    }
}

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

local LOG_TAG = "event-forwarder"

local function log(level, msg)
    io.popen(string.format('logger -t "%s" -p user.%s "%s"', LOG_TAG, level, msg:gsub('"', '\\"'))):close()
end

local function log_info(msg)  log("info", msg) end
local function log_err(msg)  log("err", msg) end
local function log_debug(msg) 
    if os.getenv("DEBUG") then log("debug", msg) end 
end

-- ============================================================================
-- BUFFER (STORE-AND-FORWARD)
-- ============================================================================

local buffer = {}

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

function buffer.save()
    local f = io.open(config.buffer_file, "w")
    if not f then return end
    
    for _, line in ipairs(buffer) do
        f:write(line .. "\n")
    end
    f:close()
end

function buffer.add(event_json)
    table.insert(buffer, event_json)
    
    -- Prevent unbounded growth
    while #buffer > 500 do
        table.remove(buffer, 1)
    end
    
    buffer.save()
    log_debug("Buffered event, total: " .. #buffer)
end

function buffer.flush(ws)
    if #buffer == 0 then return end
    
    log_info("Flushing " .. #buffer .. " buffered events...")
    
    local i = 1
    while i <= #buffer do
        local event = buffer[i]
        local sent = ws:send(event)
        
        if sent then
            table.remove(buffer, i)
            log_debug("Sent buffered event")
        else
            i = i + 1
        end
    end
    
    buffer.save()
end

function buffer.clear()
    buffer = {}
    os.execute("rm -f " .. config.buffer_file)
end

-- ============================================================================
-- WEBSOCKET CLIENT (Simple implementation)
-- ============================================================================

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

function ws.connect(url)
    local sock = require("socket").tcp()
    sock:settimeout(10)
    
    -- Parse URL
    local protocol, host, path = url:match("^(wss?)://([^/]+)(.*)")
    if not host then
        log_err("Invalid URL: " .. url)
        return nil
    end
    
    -- Connect
    local ok, err = sock:connect(host, 443)
    if not ok then
        return nil, "Connection failed: " .. tostring(err)
    end
    
    -- TLS handshake (simplified - use stunnel or openssl for real TLS)
    -- For now using raw socket - works with stunnel/Proxy
    ws.sock = sock
    ws.connected = true
    
    return ws
end

function ws.send(data)
    if not ws.connected then
        buffer.add(data)  -- Buffer instead of dropping
        return false
    end
    
    local frame = string.format(
        "\x81%s%02x%s",
        string.char(0x80 + #data),
        #data,
        data
    )
    
    local ok, err = ws.sock:send(frame)
    if not ok then
        ws.connected = false
        buffer.add(data)  -- Save to buffer on failure
        return false
    end
    
    return true
end

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

-- ============================================================================
-- EVENT GENERATORS
-- ============================================================================

local function build_event(event_type, payload)
    return string.format([[{
        "router_id": "%s",
        "hostname": "%s",
        "event_type": "%s",
        "timestamp": "%s",
        "payload": %s
    }]],
        config.router_id,
        get_hostname() or "unknown",
        event_type,
        os.date("!%Y-%m-%dT%H:%M:%SZ"),
        json.encode(payload or {})
    )
end

local function get_hostname()
    local f = io.popen("hostname")
    if not f then return "unknown" end
    local name = f:read("*a"):gsub("%s+$", "")
    f:close()
    return name
end

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

-- DHCP Lease Events
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 timestamp, mac, ip, hostname = line:match("(%d+) (%S+) (%S+) (%S+)")
                if mac then
                    leases[mac] = { ip = ip, hostname = hostname, time = tonumber(timestamp) }
                    
                    -- New lease?
                    if not old_leases[mac] then
                        local event = build_event("dhcp_lease", {
                            mac = mac,
                            ip = ip,
                            hostname = hostname,
                            action = "new"
                        })
                        log_info("New DHCP: " .. mac .. " -> " .. ip)
                        buffer.add(event)
                    end
                end
            end
            old_leases = leases
            f:close()
        end
        socket.sleep(5)
    end
end

-- Interface Events (via ubus)
function listen_interfaces()
    local proc = io.popen("ubus -m listen network.interface 2>/dev/null")
    if not proc then return end
    
    for line in proc:lines() do
        if line then
            local event_type = line:match('"action":"([^"]+)')
            local device = line:match('"interface":"([^"]+)')
            
            if event_type and device then
                local event = build_event("interface_" .. event_type, {
                    device = device,
                    action = event_type
                })
                log_info("Interface " .. event_type .. ": " .. device)
                buffer.add(event)
            end
        end
    end
    
    proc:close()
end

-- ============================================================================
-- MAIN LOOP WITH RECONNECT
-- ============================================================================

local function main()
    -- Load config
    local uci_cursor = require("luci.model.uci").cursor()
    config.server_url = uci_cursor:get("event-forwarder", "server", "url") or config.server_url
    config.server_token = uci_cursor:get("event-forwarder", "server", "token") or config.server_token
    config.router_id = uci_cursor:get("event-forwarder", "router", "id") or get_hostname()
    
    log_info("Starting event forwarder...")
    log_info("Router ID: " .. config.router_id)
    log_info("Server: " .. config.server_url)
    
    -- Load buffered events
    buffer.load()
    
    -- Write PID
    local pidf = io.open(config.pid_file, "w")
    if pidf then
        pidf:write(tostring(os.getpid()))
        pidf:close()
    end
    
    -- Initial connect
    local retries = 0
    
    while true do
        -- Try to connect
        log_info("Connecting to server...")
        local ws, err = ws.connect(config.server_url)
        
        if ws and ws.connected then
            log_info("Connected!")
            retries = 0
            
            -- Flush buffer on connect
            buffer.flush(ws)
            
            -- Main event loop - in real impl, would use select() for both sockets
            -- For simplicity, just send buffered events periodically
            while ws.connected do
                socket.sleep(config.ping_interval)
                
                -- Send ping / keepalive
                if ws.connected then
                    buffer.flush(ws)
                end
            end
        else
            log_err("Connection failed: " .. tostring(err))
            retries = retries + 1
            
            if retries >= config.max_retries then
                log_err("Max retries reached, resetting")
                retries = 0
            end
        end
        
        -- Wait before reconnect
        ws.close()
        log_info("Reconnecting in " .. config.reconnect_delay .. "s...")
        socket.sleep(config.reconnect_delay)
    end
end

-- Run
main()