#!/usr/bin/env julia

# check_and_reboot_loop.jl
# Usage: julia check_and_reboot_loop.jl
# Requires HTTP.jl (install with `julia -e 'using Pkg; Pkg.add("HTTP")'`)

# ------------------------------------------------------------------------------------------------ #
#                       add the following to root's crontab (sudo crontab -e)                      #
# ------------------------------------------------------------------------------------------------ #
# *** juliar is root's julia (sudo crontab -e) but I symlinked to juliar because I want to seperate it from user's julia
# @reboot /usr/local/bin/juliar /home/ton/docker-programs/check_and_reboot/check_router_reboot.jl >> /var/log/check_reboot.log 2>&1
# @reboot sleep 30 && /root/.juliaup/bin/julia /root/docker-apps/check_and_reboot/check_router_reboot.jl >> /var/log/check_reboot.log 2>&1

using Dates, Printf, JSON

# Configuration
const ROUTER_IP = "192.168.88.1"
const TIMEOUT_SECS = 30                # request timeout
const ATTEMPTS_PER_CHECK = 1          # number of ping attempts per check
const BACKOFF_BETWEEN_ATTEMPTS = 1    # seconds between ping attempts
const FAILS_TO_REBOOT = 3             # consecutive failed checks required to trigger reboot
const COOLDOWN_AFTER_REBOOT_SECS = 600  # do not reboot again within this many seconds
const DRY_RUN = false                  # set false to actually reboot
const CHECK_INTERVAL_SECS = 60      # run a check every CHECK_INTERVAL_SECS seconds

const thisFolderPath = @__DIR__
const LogFilePath = "$thisFolderPath/check_router_reboot_log.txt"  # write logs here and also broadcast
const StateFilePath = "$thisFolderPath/check_and_reboot_state.json"

# Simple broadcast helper
# Simple broadcast helper (safe Cmd construction)
function broadcast_msg(msg::AbstractString)
    try
        if Sys.islinux()
            # Try wall if available by writing to its stdin
            wall_paths = ("/usr/bin/wall", "/bin/wall")
            for p in wall_paths
                if isfile(p)
                    try
                        proc = open(`$p`, "w")
                        try
                            write(proc, msg * "\n")
                        finally
                            close(proc)
                        end
                        return true
                    catch
                        # ignore and try next
                    end
                end
            end
            # Fallback to logger (safe arg passing)
            try
                run(Cmd(["logger", msg]))
                return true
            catch
            end
        elseif Sys.isapple()
            # Use AppleScript notification as a fallback (escape double quotes)
            try
                escaped = replace(msg, "\"" => "\\\"")
                applescript = "display notification \"" * escaped * "\" with title \"check_and_reboot\""
                run(Cmd(["osascript", "-e", applescript]))
                return true
            catch
            end
        elseif Sys.iswindows()
            # Try msg to all sessions (may require privileges); best-effort
            try
                run(Cmd(["msg", "*", msg]))
                return true
            catch
            end
        end
    catch
        # swallow any unexpected errors
    end
    return false
end



# Simple logging (prints, appends to LogFilePath, and broadcasts)
function logmsg(s::AbstractString)
    t = Dates.now()
    out = "[$t] $s"
    # write to LogFilePath (append)
    try
        open(LogFilePath, "a") do io
            println(io, out)
        end
    catch e
        # If LogFilePath write fails, fallback to stdout
        println("[$t] (log write failed: $e) $s")
    end
    # Also print to stdout for immediate console visibility
    println(out)
    # Best-effort system broadcast so operators on console see it
    try
        broadcast_msg(out)
    catch
        # ignore broadcast failures
    end
end



# State handling
mutable struct State
    consecutive_fails::Int
    last_reboot_datetime::Union{DateTime, Nothing}
end

function load_state(StateFilePath)
    try
      if isfile(StateFilePath)
          jsonObj = JSON.parsefile(StateFilePath)
          cf = haskey(jsonObj, "consecutive_fails") ? Int(jsonObj["consecutive_fails"]) : 0
          lr = haskey(jsonObj, "last_reboot_datetime") ? jsonObj["last_reboot_datetime"] : nothing
          return State(cf, DateTime(lr))
      end
    catch e
        logmsg("Warning loading state: $e")
    end
    return State(0, nothing)
end

function save_state(st::State, StateFilePath)
    obj = Dict("consecutive_fails" => st.consecutive_fails,
               "last_reboot_datetime" => st.last_reboot_datetime)
    JSON.json(StateFilePath, obj)
end

# Router ping check
function check_router_once(ip::AbstractString; timeout=TIMEOUT_SECS)
    try
        # Use ping with count=1 and timeout in seconds
        # -W is timeout in seconds on Linux
        if Sys.islinux()
            cmd = `ping -c 1 -W $timeout $ip`
            result = run(cmd)
            return result.exitcode == 0, "exitcode: $(result.exitcode)"
        elseif Sys.isapple()
            cmd = `ping -c 1 -W $timeout $ip`
            result = run(cmd)
            return result.exitcode == 0, "exitcode: $(result.exitcode)"
        elseif Sys.iswindows()
            cmd = `ping -n 1 -w $((timeout * 1000)) $ip`
            result = run(cmd)
            return result.exitcode == 0, "exitcode: $(result.exitcode)"
        else
            return false, "unsupported OS"
        end
    catch e
        return false, string(e)
    end
end

# Check if running as root
function is_root()::Bool
    try
        result = read(`whoami`, String)
        return strip(result) == "root"
    catch
        return false
    end
end

# Reboot command selection
# Return program and separate args as plain strings
function reboot_command()
    if Sys.iswindows()
        return ("/usr/bin/cmd", "/C", "shutdown /r /t 0")
    elseif Sys.isapple()
        if is_root()
            return ("/sbin/reboot")
        else
            return ("/usr/bin/sudo", "shutdown", "-r", "now")
        end
    elseif Sys.islinux()
        if is_root()
            if isfile("/bin/systemctl")
                return ("/bin/systemctl", "reboot")
            else
                return ("/usr/sbin/reboot")
            end
        else
            if isfile("/bin/systemctl") || isfile("/usr/bin/systemctl")
                return ("/usr/bin/sudo", "systemctl", "reboot")
            else
                return ("/usr/bin/sudo", "reboot")
            end
        end
    else
        return nothing
    end
end

function do_reboot()
    cmd = reboot_command()
    if cmd === nothing
        logmsg("Reboot not supported on this OS")
        return false
    end

    # Build a readable command string for logs (escape each arg safely)
    cmd_str = join(map(x -> replace(x, '"' => "\\\""), cmd), " ")

    if DRY_RUN
        logmsg("DRY RUN: would run reboot command: $cmd_str")
        return true
    end

    logmsg("Executing reboot command: $cmd_str")
    try
        # Construct a Cmd from an array so arguments are passed directly (no shell)
        cmd_array = collect(cmd)           # Tuple{String,...} -> Vector{String}
        run(Cmd(cmd_array))
        return true
    catch e
        logmsg("Failed to execute reboot command: $e")
        return false
    end
end


# Single check iteration
function perform_check!(st::State)

  success = false
  last_result = nothing
  for i in 1:ATTEMPTS_PER_CHECK
      ok, result = check_router_once(ROUTER_IP) 
      # ok, result = values(JSON.parsefile("test_ping_result.json"))  # for testing without actual ping
      if ok
          success = true
          break
      end
      sleep(BACKOFF_BETWEEN_ATTEMPTS)
  end
  routerresult = isnothing(last_result) ? "no response" : last_result

  # Check if we're in cooldown period
  in_cooldown = false
  if st.last_reboot_datetime !== nothing
    timepass = ((Dates.now() - st.last_reboot_datetime).value / 1000) |> floor |> Int

    if timepass < COOLDOWN_AFTER_REBOOT_SECS
        in_cooldown = true
    end
  end

  if in_cooldown
    # During cooldown, track failures but don't trigger reboot yet
    if success
      logmsg("$ROUTER_IP is reachable during cooldown. Router is back online! Resetting state.")
      st.consecutive_fails = 0
      save_state(st, StateFilePath)
    else
      st.consecutive_fails += 1
      
      logmsg("$ROUTER_IP is unreachable during cooldown. Consecutive fails: $(st.consecutive_fails)/$FAILS_TO_REBOOT.")
      save_state(st, StateFilePath)
      
      # Check if we've reached threshold by now
      if st.consecutive_fails >= FAILS_TO_REBOOT
        logmsg("Cooldown has expired and router is still unreachable. Triggering reboot.")
        ok = do_reboot()
        if ok
            thisFilePath = @__FILE__
            broadcast_msg("Broadcasting from file: $thisFilePath")
            logmsg("Reboot executed (or simulated). Resetting failure counter.")
            st.consecutive_fails = 0
            st.last_reboot_datetime = Dates.now()
            save_state(st, StateFilePath)
        else
            logmsg("Reboot attempt failed; will retry after next interval.")
        end
      end
    end
    return
  end

  # Outside cooldown - full check with potential reboot
  if success
      if st.consecutive_fails > 0
          logmsg("$ROUTER_IP is reachable; resetting consecutive failure counter.")
      else
          # logmsg("$ROUTER_IP is reachable.")
      end
      st.consecutive_fails = 0
      save_state(st, StateFilePath)
      return
  else
      st.consecutive_fails += 1
      logmsg("$ROUTER_IP is unreachable (last result: $routerresult). Consecutive fails: $(st.consecutive_fails)/$FAILS_TO_REBOOT.")
      save_state(st, StateFilePath)
  end
  if st.consecutive_fails >= FAILS_TO_REBOOT
      save_state(st, StateFilePath)
      ok = do_reboot()
      if ok
          thisFilePath = @__FILE__
          broadcast_msg("Broadcasting from file: $thisFilePath")
          logmsg("Reboot executed (or simulated). Resetting failure counter.")
          st.consecutive_fails = 0
          st.last_reboot_datetime = Dates.now()
          save_state(st, StateFilePath)
      else
          logmsg("Reboot attempt failed; will retry after next interval.")
      end
  end
end


function limitTextFileLines(LogFilePath::String; maxlines::Integer=100)
  log = readlines(LogFilePath)
  if length(log) < (maxlines - 1)
    return nothing
  end
  reducedLog = ""
  for i in log[end-(maxlines-1):end]
    reducedLog = reducedLog * i * "\n"
  end
  write(LogFilePath, reducedLog)
end

# Main loop: runs indefinitely every CHECK_INTERVAL_SECS
function main_loop()
    # Ensure log file exists
    if !isfile(LogFilePath)
        open(LogFilePath, "a") do io
            # create empty file
        end
    end
    # limit  log file to latest 100 events
    limitTextFileLines(LogFilePath; maxlines=100)
    thisFilePath = @__FILE__ 
    broadcast_msg("Broadcasting from file: $thisFilePath")
    logmsg("Starting check loop. Checking router $ROUTER_IP every $(CHECK_INTERVAL_SECS) seconds.")
    st = load_state(StateFilePath)
    while true
        try
            perform_check!(st)
        catch e
            logmsg("Error during check: $e")
        end
        sleep(CHECK_INTERVAL_SECS)
    end
end

# Run
main_loop()