# Copyright 2021 Mattia Giambirtone & All Contributors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import parseopt
import strformat
import posix
import net
import os

# NimD's own stuff
import util/[logging, constants, misc, config, cffi]
import core/[mainloop, fs, shutdown, services]


proc addStuff = 
    ## Adds stuff to test NimD. This is
    ## a temporary procedure
    
    ## Note: Commented because the config file now does this work!
    # Adds symlinks
    # addSymlink(newSymlink(dest="/dev/fd", source="/proc/self/fd"))
    # addSymlink(newSymlink(dest="/dev/fd/0", source="/proc/self/fd/0"))
    # addSymlink(newSymlink(dest="/dev/fd/1", source="/proc/self/fd/1"))
    # addSymlink(newSymlink(dest="/dev/fd/2", source="/proc/self/fd/2"))
    # addSymlink(newSymlink(dest="/dev/std/in", source="/proc/self/fd/0"))
    # addSymlink(newSymlink(dest="/dev/std/out", source="/proc/self/fd/1"))
    # addSymlink(newSymlink(dest="/dev/std/err", source="/proc/self/fd/2"))
    # # Tests here. Check logging output (debug) to see if
    # # they work as intended
    # addSymlink(newSymlink(dest="/dev/std/err", source="/"))                # Should say link already exists and points to /proc/self/fd/2
    # addSymlink(newSymlink(dest="/dev/std/in", source="/does/not/exist"))   # Should say destination does not exist
    # addSymlink(newSymlink(dest="/dev/std/in", source="/proc/self/fd/0"))   # Should say link already exists
    # addDirectory(newDirectory("test", 764))           # Should create a directory
    # addDirectory(newDirectory("/dev/disk", 123))      # Should say directory already exists

    # Adds test services
    var echoer = newService(name="echoer", description="prints owo", exec="/bin/echo owoooooooooo",
                            runlevel=Boot, kind=Oneshot, workDir=getCurrentDir(),
                            supervised=false, restart=Never, restartDelay=0,
                            depends=(@[]), provides=(@[]), stdin="/dev/null", stderr="", stdout="")
    var errorer = newService(name="errorer", description="la mamma di gavd", 
                         exec="/bin/false", supervised=true, restart=OnFailure,
                         restartDelay=5, runlevel=Boot, workDir="/", kind=Simple,
                         depends=(@[newDependency(Other, echoer)]), provides=(@[]),
                         stdin="/dev/null", stderr="", stdout="")
    var exiter = newService(name="exiter", description="la mamma di licenziat", 
                          exec="/bin/true", supervised=true, restart=Always,
                          restartDelay=5, runlevel=Boot, workDir="/", kind=Simple,
                          depends=(@[newDependency(Other, errorer)]), provides=(@[]),
                          stdin="/dev/null", stderr="", stdout="")
    var shell = newService(name="login", description="A simple login shell", kind=Simple,
                           workDir=getCurrentDir(), runlevel=Default, exec="/bin/login -f root",
                           supervised=true, restart=Always, restartDelay=0, depends=(@[]), provides=(@[]),
                           useParentStreams=true, stdin="/dev/null", stderr="/proc/self/fd/2", stdout="/proc/self/fd/1"
                           )
    addService(errorer)
    addService(echoer)
    addService(exiter)
    addService(shell)


proc checkControlSocket(logger: Logger, config: NimDConfig): bool =
    ## Performs some startup checks on nim's control
    ## socket
    result = true
    var stat_result: Stat
    if posix.stat(cstring(config.sock), stat_result) == -1 and posix.errno != 2:
        logger.warning(&"Could not stat() {config.sock}, assuming NimD instance isn't running")
    elif posix.errno == 2:
        logger.debug(&"Control socket path is clear, starting up")
        posix.errno = 0
        # 2 is ENOENT, which means the file does not exist
    # I stole this from /usr/lib/python3.10/stat.py
    elif (int(stat_result.st_mode) and 0o170000) != 0o140000:
        logger.fatal(&"{config.sock} exists and is not a socket")
        result = false
    elif dirExists(config.sock):
        logger.info("Control socket path is a directory, appending nimd.sock to it")
        config.sock = config.sock.joinPath("nimd.sock")
    else:
        logger.debug("Trying to reach current NimD instance")
        var sock = newSocket(Domain.AF_UNIX, SockType.SOCK_STREAM, Protocol.IPPROTO_IP)
        try:
            sock.connectUnix(config.sock)
            logger.info("Control socket already exists, trying to reach current NimD instance")
        except OSError:
            logger.warning(&"Could not connect to control socket at {config.sock} ({getCurrentExceptionMsg()}), assuming NimD instance isn't running")
            try:
                removeFile(config.sock)
            except OSError:
                logger.warning(&"Could not delete dangling control socket at {config.sock} ({getCurrentExceptionMsg()})")
        if sock.trySend("c"):
            try:
                if sock.recv(1, timeout=5) == "1":
                    logger.error("Another NimD instance is running! Exiting")
                    result = false
            except OSError:
                logger.warning(&"Could not read from control socket at {config.sock} ({getCurrentExceptionMsg()}), assuming NimD instance isn't running")
            except TimeoutError:
                logger.warning(&"Could not read from control socket at {config.sock} ({getCurrentExceptionMsg()}), assuming NimD instance isn't running")
        else:
            logger.fatal(&"Could not write on control socket at {config.sock}")
            result = false


proc main(logger: Logger, config: NimDConfig) =
    ## NimD's entry point and setup
    ## function
    if not checkControlSocket(logger, config):
        return
    logger.debug(&"Setting log file to '{config.logFile}'")
    setLogFile(file=config.logFile)
    # Black Lives Matter. This is sarcasm btw. Fuck the left
    logger.critical("WOOO BLACK LIVES MATTER YOUR MOM BLACK I BANG HER WITH MY BBC BLACK LIVES MATTER LETS FUCKING GOOOOO")
    logger.info("Starting NimD: A minimal, self-contained, dependency-based Linux init system written in Nim")
    logger.info(&"NimD version {NimdVersion.major}.{NimdVersion.minor}.{NimdVersion.patch} is starting up!")
    logger.trace("Calling getCurrentProcessId()")
    let pid = getCurrentProcessId()
    logger.trace(&"getCurrentProcessId() returned {pid}")
    if pid != 1:
        logger.warning(&"Expecting to run as PID 1, but current process ID is {pid}")
    logger.trace("Calling getuid()")
    let uid = posix.getuid()
    logger.trace(&"getuid() returned {uid}")
    if uid != 0:
        logger.fatal(&"NimD must run as root, but current user id is {uid}")
        nimDExit(logger, EPERM, emerg=false)   # EPERM - Operation not permitted
    logger.trace("Setting up signal handlers")
    onSignal(SIGABRT, SIGALRM, SIGHUP, SIGILL, SIGKILL, SIGQUIT, SIGSTOP, SIGSEGV, SIGTSTP,
             SIGTRAP, SIGPIPE, SIGUSR1, SIGUSR2, 6, SIGFPE, SIGBUS, SIGURG, SIGTERM, SIGINT):  # 6 is SIGIOT
        # Can't capture local variables because this implicitly generates
        # a noconv procedure, so we use getDefaultLogger() instead
        getDefaultLogger().warning(&"Ignoring signal {sig} ({strsignal(sig)})")  # Nim injects the variable "sig" into the scope. Gotta love those macros
    onSignal(SIGCHLD):
        # One of the key features of an init system is reaping child
        # processes!
        reapProcess(getDefaultLogger())
    if config.autoUnmount:
        logger.debug("Setting up shutdown handler for automatic disk unmounting")
        # Shutdown handler to unmount disks
        addShutdownHandler(newShutdownHandler(unmountAllDisks))
    addStuff()
    try:
        if config.autoMount:
            logger.info("Mounting filesystem")
            mountDisks(logger, config.fstab)
        else:
            logger.info("Skipping disk mounting, assuming this has already been done")
        logger.info("Creating symlinks")
        createSymlinks(logger)
        logger.info("Creating directories")
        createDirectories(logger)
        logger.info("Filesystem preparation complete")
        logger.debug("Calling sync() just in case")
        doSync(logger)
    except:
        logger.fatal(&"A fatal error has occurred while preparing filesystem, booting cannot continue. Error -> {getCurrentExceptionMsg()}")
        nimDExit(logger, 131, emerg=false)
    if config.setHostname:
        logger.info("Setting hostname")
        logger.debug(&"Hostname was set to '{misc.setHostname(logger)}'")
    else:
        logger.info("Skipping setting hostname")
    logger.debug("Entering critical fork() section: blocking signals")
    blockSignals(logger)   # They are later unblocked in mainLoop
    logger.info("Processing boot runlevel")
    startServices(logger, workers=config.workers, level=Boot)
    logger.debug("Starting main loop")
    mainLoop(logger, config)


when isMainModule:
    var logger = getDefaultLogger()
    var optParser = initOptParser(commandLineParams())
    for kind, key, value in optParser.getopt():
        case kind:
            of cmdArgument:
                echo "Error: unexpected argument"
                quit(EINVAL)
            of cmdLongOption:
                case key:
                    of "help":
                        echo helpMessage
                        quit(0)
                    of "version":
                        echo NimDVersionString
                        quit(0)
                    of "verbose":
                        logger.setLevel(LogLevel.Debug)
                    of "extra":
                        logger.setLevel(LogLevel.Trace)
                    else:
                        echo &"Unkown command-line long option '{key}'"
                        quit(EINVAL)  # EINVAL - Invalid argument
            of cmdShortOption:
                case key:
                    of "h":
                        echo helpMessage
                        quit(0)
                    of "v":
                        echo NimDVersionString
                        quit(0)
                    of "V":
                        logger.setLevel(LogLevel.Debug)
                    of "X":
                        logger.setLevel(LogLevel.Trace)
                    else:
                        echo &"Unkown command-line short option '{key}'"
                        echo "Usage: nimd [options]"
                        echo "Try nimd --help for more info"
                        quit(EINVAL) # EINVAL - Invalid argument
            else:
                echo "Usage: nimd [options]"
                quit(EINVAL) # EINVAL - Invalid argument        
    setStdIoUnbuffered()   # Colors don't work otherwise!
    try:
        main(logger, parseConfig(logger, "/etc/nimd/nimd.conf"))
    except:
        logger.fatal(&"A fatal unrecoverable error has occurred during startup and NimD cannot continue: {getCurrentExceptionMsg()}")
        nimDExit(logger, 131)  # ENOTRECOVERABLE - State not recoverable
        # This will almost certainly cause the kernel to crash with an error the likes of "Kernel not syncing, attempted to kill init!",
        # but, after all, there isn't much we can do if we can't even initialize *ourselves* is there?