#!/usr/bin/env python


__license__ = 'GPL v3'
__copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'

import errno
import os
import signal
import socket
import ssl
import subprocess
import sys
import time
from queue import Empty, Queue
from threading import Lock, Thread

from calibre.constants import islinux, ismacos, iswindows
from calibre.srv.http_response import create_http_handler
from calibre.srv.loop import ServerLoop
from calibre.srv.opts import Options
from calibre.srv.standalone import create_option_parser
from calibre.srv.utils import create_sock_pair
from calibre.srv.web_socket import DummyHandler
from calibre.utils.monotonic import monotonic
from polyglot.builtins import error_message

MAX_RETRIES = 10


class NoAutoReload(EnvironmentError):
    pass


# Filesystem watcher {{{

class WatcherBase:

    EXTENSIONS_TO_WATCH = frozenset('py pyj svg js css'.split())
    BOUNCE_INTERVAL = 2  # seconds

    def __init__(self, worker, log):
        self.worker, self.log = worker, log
        fpath = os.path.abspath(__file__)
        d = os.path.dirname
        self.base = d(d(d(d(fpath))))
        self.last_restart_time = monotonic()

    def handle_modified(self, modified):
        if modified:
            if monotonic() - self.last_restart_time > self.BOUNCE_INTERVAL:
                modified = {os.path.relpath(x, self.base) if x.startswith(self.base) else x for x in modified if x}
                changed = os.pathsep.join(sorted(modified))
                self.log('')
                self.log.warn('Restarting server because of changed files:', changed)
                self.log('')
                self.worker.restart()
                self.last_restart_time = monotonic()

    def force_restart(self):
        self.worker.restart(forced=True)
        self.last_restart_time = monotonic()

    def file_is_watched(self, fname):
        return fname and fname.rpartition('.')[-1] in self.EXTENSIONS_TO_WATCH


if islinux:
    import select

    from calibre.utils.inotify import INotifyTreeWatcher

    class Watcher(WatcherBase):

        def __init__(self, root_dirs, worker, log):
            WatcherBase.__init__(self, worker, log)
            self.client_sock, self.srv_sock = create_sock_pair()
            self.fd_map = {}
            for d in frozenset(root_dirs):
                w = INotifyTreeWatcher(d, self.ignore_event)
                self.fd_map[w._inotify_fd] = w

        def loop(self):
            while True:
                r = select.select([self.srv_sock] + list(self.fd_map), [], [])[0]
                modified = set()
                for fd in r:
                    if fd is self.srv_sock:
                        self.srv_sock.recv(1000)
                        self.force_restart()
                        continue
                    w = self.fd_map[fd]
                    modified |= w()
                self.handle_modified(modified)

        def ignore_event(self, path, name):
            return not self.file_is_watched(name)

        def wakeup(self):
            self.client_sock.sendall(b'w')

elif iswindows:
    from calibre.srv.utils import HandleInterrupt
    from calibre_extensions import winutil

    class TreeWatcher(Thread):

        def __init__(self, path_to_watch, modified_queue):
            Thread.__init__(self, name='TreeWatcher', daemon=True)
            self.modified_queue = modified_queue
            self.path_to_watch = path_to_watch

        def run(self):
            dir_handle = winutil.create_file(
                self.path_to_watch,
                winutil.FILE_LIST_DIRECTORY,
                winutil.FILE_SHARE_READ,
                winutil.OPEN_EXISTING,
                winutil.FILE_FLAG_BACKUP_SEMANTICS,
            )

            try:
                buffer = b'0' * 8192
                while True:
                    try:
                        results = winutil.read_directory_changes(
                            dir_handle, buffer,
                            True,  # Watch sub-directories as well
                            winutil.FILE_NOTIFY_CHANGE_FILE_NAME |
                            winutil.FILE_NOTIFY_CHANGE_DIR_NAME |
                            winutil.FILE_NOTIFY_CHANGE_ATTRIBUTES |
                            winutil.FILE_NOTIFY_CHANGE_SIZE |
                            winutil.FILE_NOTIFY_CHANGE_LAST_WRITE |
                            winutil.FILE_NOTIFY_CHANGE_SECURITY,
                        )
                        for action, filename in results:
                            if self.file_is_watched(filename):
                                self.modified_queue.put(os.path.join(self.path_to_watch, filename))
                    except OverflowError:
                        pass  # the buffer overflowed, there are unknown changes
            except Exception:
                import traceback
                traceback.print_exc()

    class Watcher(WatcherBase):

        def __init__(self, root_dirs, worker, log):
            WatcherBase.__init__(self, worker, log)
            self.watchers = []
            self.modified_queue = Queue()
            for d in frozenset(root_dirs):
                self.watchers.append(TreeWatcher(d, self.modified_queue))

        def wakeup(self):
            self.modified_queue.put(True)

        def loop(self):
            for w in self.watchers:
                w.start()
            with HandleInterrupt(lambda: self.modified_queue.put(None)):
                while True:
                    path = self.modified_queue.get()
                    if path is None:
                        break
                    if path is True:
                        self.force_restart()
                    else:
                        self.handle_modified({path})

elif ismacos:
    from fsevents import Observer, Stream

    class Watcher(WatcherBase):

        def __init__(self, root_dirs, worker, log):
            WatcherBase.__init__(self, worker, log)
            self.stream = Stream(self.notify, *(x.encode('utf-8') for x in root_dirs), file_events=True)
            self.wait_queue = Queue()

        def wakeup(self):
            self.wait_queue.put(True)

        def loop(self):
            observer = Observer()
            observer.schedule(self.stream)
            observer.daemon = True
            observer.start()
            try:
                while True:
                    try:
                        # Cannot use blocking get() as it is not interrupted by
                        # Ctrl-C
                        if self.wait_queue.get(10000) is True:
                            self.force_restart()
                    except Empty:
                        pass
            finally:
                observer.unschedule(self.stream)
                observer.stop()

        def notify(self, ev):
            name = ev.name
            if isinstance(name, bytes):
                name = name.decode('utf-8')
            if self.file_is_watched(name):
                self.handle_modified({name})

else:
    Watcher = None


def find_dirs_to_watch(fpath, dirs, add_default_dirs):
    dirs = {os.path.abspath(x) for x in dirs}

    def add(x):
        if os.path.isdir(x):
            dirs.add(x)
    if add_default_dirs:
        d = os.path.dirname
        srv = d(fpath)
        add(srv)
        base = d(d(d(srv)))
        add(os.path.join(base, 'resources', 'content-server'))
        add(os.path.join(base, 'src', 'calibre', 'db'))
        add(os.path.join(base, 'src', 'pyj'))
        add(os.path.join(base, 'imgsrc', 'srv'))
    return dirs
# }}}


def join_process(p, timeout=5):
    t = Thread(target=p.wait, name='JoinProcess')
    t.daemon = True
    t.start()
    t.join(timeout)
    return p.poll()


class Worker:

    def __init__(self, cmd, log, server, timeout=5):
        self.cmd = cmd
        self.log = log
        self.server = server
        self.p = None
        self.wakeup = None
        self.timeout = timeout
        cmd = self.cmd
        if 'calibre-debug' in cmd[0].lower():
            try:
                idx = cmd.index('--')
            except ValueError:
                cmd = ['srv']
            else:
                cmd = ['srv'] + cmd[idx+1:]

        opts = create_option_parser().parse_args(cmd)[0]
        self.port = opts.port
        self.uses_ssl = bool(opts.ssl_certfile and opts.ssl_keyfile)
        self.connection_timeout = opts.timeout
        self.retry_count = 0
        t = Thread(name='PingThread', target=self.ping_thread)
        t.daemon = True
        t.start()

    def ping_thread(self):
        while True:
            self.server.ping()
            time.sleep(30)

    def __enter__(self):
        self.restart()
        return self

    def __exit__(self, *args):
        if self.p and self.p.poll() is None:
            # SIGINT will already have been sent to the child process
            self.clean_kill(send_signal=False)

    def clean_kill(self, send_signal=True):
        if self.p is not None:
            if send_signal:
                self.p.send_signal(getattr(signal, 'CTRL_BREAK_EVENT', signal.SIGINT))
            if join_process(self.p) is None:
                self.p.kill()
                self.p.wait()
            self.log(f'Killed server process {self.p.pid} with return code: {self.p.returncode}')
            self.p = None

    def restart(self, forced=False):
        from calibre.utils.rapydscript import CompileFailure, compile_srv
        self.clean_kill()
        if forced:
            self.retry_count += 1
        else:
            self.retry_count = 0
        try:
            compile_srv()
        except OSError as e:
            # Happens if the editor deletes and replaces a file being edited
            if e.errno != errno.ENOENT or not getattr(e, 'filename', False):
                raise
            st = monotonic()
            while not os.path.exists(e.filename) and monotonic() - st < 3:
                time.sleep(0.01)
            compile_srv()
        except CompileFailure as e:
            self.log.error(error_message(e))
            time.sleep(0.1 * self.retry_count)
            if self.retry_count < MAX_RETRIES and self.wakeup is not None:
                self.wakeup()  # Force a restart
            return

        self.retry_count = 0
        self.p = subprocess.Popen(self.cmd, creationflags=getattr(subprocess, 'CREATE_NEW_PROCESS_GROUP', 0))
        self.wait_for_listen()
        self.server.notify_reload()

    def wait_for_listen(self):
        st = monotonic()
        while monotonic() - st < 5:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.settimeout(5)
            try:
                if self.uses_ssl:
                    s = ssl._create_stdlib_context().wrap_socket(s)
                s.connect(('localhost', self.port))
                return
            except OSError:
                time.sleep(0.01)
            finally:
                s.close()
        self.log.error('Restarted server did not start listening on:', self.port)


# WebSocket reload notifier {{{

class ReloadHandler(DummyHandler):

    def __init__(self, *args, **kw):
        DummyHandler.__init__(self, *args, **kw)
        self.connections = {}
        self.conn_lock = Lock()

    def handle_websocket_upgrade(self, connection_id, connection_ref, inheaders):
        with self.conn_lock:
            self.connections[connection_id] = connection_ref

    def handle_websocket_close(self, connection_id):
        with self.conn_lock:
            self.connections.pop(connection_id, None)

    def notify_reload(self):
        with self.conn_lock:
            for connref in self.connections.values():
                conn = connref()
                if conn is not None and conn.ready:
                    conn.send_websocket_message('reload')

    def ping(self):
        with self.conn_lock:
            for connref in self.connections.values():
                conn = connref()
                if conn is not None and conn.ready:
                    conn.send_websocket_message('ping')


class ReloadServer(Thread):

    daemon = True

    def __init__(self, listen_on):
        Thread.__init__(self, name='ReloadServer')
        self.reload_handler = ReloadHandler()
        self.loop = ServerLoop(
            create_http_handler(websocket_handler=self.reload_handler),
            opts=Options(shutdown_timeout=0.1, listen_on=(listen_on or '127.0.0.1'), port=0))
        self.loop.LISTENING_MSG = None
        self.notify_reload = self.reload_handler.notify_reload
        self.ping = self.reload_handler.ping
        self.start()

    def run(self):
        try:
            self.loop.serve_forever()
        except KeyboardInterrupt:
            pass

    def __enter__(self):
        while not self.loop.ready and self.is_alive():
            time.sleep(0.01)
        self.address = self.loop.bound_address[:2]
        os.environ['CALIBRE_AUTORELOAD_PORT'] = str(self.address[1])
        return self

    def __exit__(self, *args):
        self.loop.stop()
        self.join(self.loop.opts.shutdown_timeout)
# }}}


def auto_reload(log, dirs=frozenset(), cmd=None, add_default_dirs=True, listen_on=None):
    if Watcher is None:
        raise NoAutoReload('Auto-reload is not supported on this operating system')
    fpath = os.path.abspath(__file__)
    if not os.access(fpath, os.R_OK):
        raise NoAutoReload('Auto-reload can only be used when running from source')
    if cmd is None:
        cmd = list(sys.argv)
        cmd.remove('--auto-reload')
    if os.path.basename(cmd[0]) == 'run-local':
        cmd.insert(1, 'calibre-server')
    dirs = find_dirs_to_watch(fpath, dirs, add_default_dirs)
    log('Auto-restarting server on changes press Ctrl-C to quit')
    log(f'Watching {len(dirs)} directory trees for changes')
    with ReloadServer(listen_on) as server, Worker(cmd, log, server) as worker:
        w = Watcher(dirs, worker, log)
        worker.wakeup = w.wakeup
        try:
            w.loop()
        except KeyboardInterrupt:
            pass
