import re
from contextlib import contextmanager
from tempfile import NamedTemporaryFile

from plumbum.commands import CommandNotFound, ConcreteCommand, shquote
from plumbum.lib import ProcInfo
from plumbum.machines.base import BaseMachine
from plumbum.machines.env import BaseEnv
from plumbum.machines.local import LocalPath
from plumbum.path.remote import RemotePath, RemoteWorkdir, StatRes


class RemoteEnv(BaseEnv):
    """The remote machine's environment; exposes a dict-like interface"""

    __slots__ = ["_orig", "remote"]

    def __init__(self, remote):
        session = remote._session
        # GNU env has a -0 argument; use it if present. Otherwise,
        # fall back to calling printenv on each (possible) variable
        # from plain env.
        env0 = session.run("env -0; echo")
        if env0[0] == 0 and not env0[2].rstrip():
            _curr = dict(
                line.split("=", 1) for line in env0[1].split("\x00") if "=" in line
            )
        else:
            lines = session.run("env; echo")[1].splitlines()
            split = (line.split("=", 1) for line in lines)
            keys = (line[0] for line in split if len(line) > 1)
            runs = ((key, session.run(f'printenv "{key}"; echo')) for key in keys)
            _curr = {
                key: run[1].rstrip("\n")
                for (key, run) in runs
                if run[0] == 0 and run[1].rstrip("\n") and not run[2]
            }

        super().__init__(remote.path, ":", _curr=_curr)
        self.remote = remote
        self._orig = self._curr.copy()

    def __delitem__(self, name):
        BaseEnv.__delitem__(self, name)
        self.remote._session.run(f"unset {name}")

    def __setitem__(self, name, value):
        BaseEnv.__setitem__(self, name, value)
        self.remote._session.run(f"export {name}={shquote(value)}")

    def pop(self, name, *default):
        BaseEnv.pop(self, name, *default)
        self.remote._session.run(f"unset {name}")

    def update(self, *args, **kwargs):
        BaseEnv.update(self, *args, **kwargs)
        self.remote._session.run(
            "export " + " ".join(f"{k}={shquote(v)}" for k, v in self.getdict().items())
        )

    def expand(self, expr):
        """Expands any environment variables and home shortcuts found in ``expr``
        (like ``os.path.expanduser`` combined with ``os.path.expandvars``)

        :param expr: An expression containing environment variables (as ``$FOO``) or
                     home shortcuts (as ``~/.bashrc``)

        :returns: The expanded string"""
        return self.remote.expand(expr)

    def expanduser(self, expr):
        """Expand home shortcuts (e.g., ``~/foo/bar`` or ``~john/foo/bar``)

        :param expr: An expression containing home shortcuts

        :returns: The expanded string"""
        return self.remote.expanduser(expr)

    # def clear(self):
    #    BaseEnv.clear(self, *args, **kwargs)
    #    self.remote._session.run("export %s" % " ".join("%s=%s" % (k, v) for k, v in self.getdict()))

    def getdelta(self):
        """Returns the difference between the this environment and the original environment of
        the remote machine"""
        self._curr["PATH"] = self.path.join()

        delta = {}
        for k, v in self._curr.items():
            if k not in self._orig:
                delta[k] = str(v)
        for k, v in self._orig.items():
            if k not in self._curr:
                delta[k] = ""
            else:
                if v != self._curr[k]:
                    delta[k] = self._curr[k]

        return delta


class RemoteCommand(ConcreteCommand):
    __slots__ = ["remote", "executable"]
    QUOTE_LEVEL = 1

    def __init__(self, remote, executable, encoding="auto"):
        self.remote = remote
        ConcreteCommand.__init__(
            self, executable, remote.custom_encoding if encoding == "auto" else encoding
        )

    @property
    def machine(self):
        return self.remote

    def __repr__(self):
        return f"RemoteCommand({self.remote!r}, {self.executable!r})"

    def popen(self, args=(), **kwargs):
        return self.remote.popen(self[args], **kwargs)

    def nohup(self, cwd=".", stdout="nohup.out", stderr=None, append=True):
        """Runs a command detached."""
        return self.machine.daemonic_popen(self, cwd, stdout, stderr, append)


class ClosedRemoteMachine(Exception):
    pass


class ClosedRemote:
    __slots__ = ["_obj", "__weakref__"]

    def __init__(self, obj):
        self._obj = obj

    def close(self):
        pass

    def __getattr__(self, name):
        raise ClosedRemoteMachine(f"{self._obj!r} has been closed")


class BaseRemoteMachine(BaseMachine):
    """Represents a *remote machine*; serves as an entry point to everything related to that
    remote machine, such as working directory and environment manipulation, command creation,
    etc.

    Attributes:

    * ``cwd`` - the remote working directory
    * ``env`` - the remote environment
    * ``custom_encoding`` - the remote machine's default encoding (assumed to be UTF8)
    * ``connect_timeout`` - the connection timeout


    There also is a _cwd attribute that exists if the cwd is not current (del if cwd is changed).
    """

    # allow inheritors to override the RemoteCommand class
    RemoteCommand = RemoteCommand

    @property
    def cwd(self):
        if not hasattr(self, "_cwd"):
            self._cwd = RemoteWorkdir(self)
        return self._cwd

    def __init__(self, encoding="utf8", connect_timeout=10, new_session=False):
        self.custom_encoding = encoding
        self.connect_timeout = connect_timeout
        self._session = self.session(new_session=new_session)
        self.uname = self._get_uname()
        self.env = RemoteEnv(self)
        self._python = None
        self._program_cache = {}

    def _get_uname(self):
        rc, out, _ = self._session.run("uname", retcode=None)
        if rc == 0:
            return out.strip()

        rc, out, _ = self._session.run(
            "python3 -c 'import platform;print(platform.uname()[0])'", retcode=None
        )
        if rc == 0:
            return out.strip()

        # all POSIX systems should have uname. make an educated guess it's Windows
        return "Windows"

    def __repr__(self):
        return f"<{self.__class__.__name__} {self}>"

    def __enter__(self):
        return self

    def __exit__(self, t, v, tb):
        self.close()

    def close(self):
        """closes the connection to the remote machine; all paths and programs will
        become defunct"""
        self._session.close()
        self._session = ClosedRemote(self)

    def path(self, *parts):
        """A factory for :class:`RemotePaths <plumbum.path.remote.RemotePath>`.
        Usage: ``p = rem.path("/usr", "lib", "python2.7")``
        """
        parts2 = [str(self.cwd)]
        for p in parts:
            if isinstance(p, LocalPath):
                raise TypeError(f"Cannot construct RemotePath from {p!r}")
            parts2.append(self.expanduser(str(p)))
        return RemotePath(self, *parts2)

    def which(self, progname):
        """Looks up a program in the ``PATH``. If the program is not found, raises
        :class:`CommandNotFound <plumbum.commands.CommandNotFound>`

        :param progname: The program's name. Note that if underscores (``_``) are present
                         in the name, and the exact name is not found, they will be replaced
                         in turn by hyphens (``-``) then periods (``.``), and the name will
                         be looked up again for each alternative

        :returns: A :class:`RemotePath <plumbum.path.local.RemotePath>`
        """
        key = (progname, self.env.get("PATH", ""))

        try:
            return self._program_cache[key]
        except KeyError:
            pass

        alternatives = [progname]
        if "_" in progname:
            alternatives.append(progname.replace("_", "-"))
            alternatives.append(progname.replace("_", "."))
        for name in alternatives:
            for p in self.env.path:
                fn = p / name
                if fn.access("x") and not fn.is_dir():
                    self._program_cache[key] = fn
                    return fn

        raise CommandNotFound(progname, self.env.path)

    def __getitem__(self, cmd):
        """Returns a `Command` object representing the given program. ``cmd`` can be a string or
        a :class:`RemotePath <plumbum.path.remote.RemotePath>`; if it is a path, a command
        representing this path will be returned; otherwise, the program name will be looked up in
        the system's ``PATH`` (using ``which``). Usage::

            r_ls = rem["ls"]
        """
        if isinstance(cmd, RemotePath):
            if cmd.remote is self:
                return self.RemoteCommand(self, cmd)

            raise TypeError(
                f"Given path does not belong to this remote machine: {cmd!r}"
            )

        if not isinstance(cmd, LocalPath):
            return self.RemoteCommand(
                self, self.path(cmd) if "/" in cmd or "\\" in cmd else self.which(cmd)
            )

        raise TypeError(f"cmd must not be a LocalPath: {cmd!r}")

    @property
    def python(self):
        """A command that represents the default remote python interpreter"""
        if not self._python:
            self._python = self["python3"]
        return self._python

    def session(self, isatty=False, new_session=False):
        """Creates a new :class:`ShellSession <plumbum.session.ShellSession>` object; this invokes the user's
        shell on the remote machine and executes commands on it over stdin/stdout/stderr"""
        raise NotImplementedError()

    def download(self, src, dst):
        """Downloads a remote file/directory (``src``) to a local destination (``dst``).
        ``src`` must be a string or a :class:`RemotePath <plumbum.path.remote.RemotePath>`
        pointing to this remote machine, and ``dst`` must be a string or a
        :class:`LocalPath <plumbum.machines.local.LocalPath>`"""
        raise NotImplementedError()

    def upload(self, src, dst):
        """Uploads a local file/directory (``src``) to a remote destination (``dst``).
        ``src`` must be a string or a :class:`LocalPath <plumbum.machines.local.LocalPath>`,
        and ``dst`` must be a string or a :class:`RemotePath <plumbum.path.remote.RemotePath>`
        pointing to this remote machine"""
        raise NotImplementedError()

    def popen(self, args, **kwargs):
        """Spawns the given command on the remote machine, returning a ``Popen``-like object;
        do not use this method directly, unless you need "low-level" control on the remote
        process"""
        raise NotImplementedError()

    def list_processes(self):
        """
        Returns information about all running processes (on POSIX systems: using ``ps``)

        .. versionadded:: 1.3
        """
        ps = self["ps"]
        lines = ps("-e", "-o", "pid,uid,stat,args").splitlines()
        lines.pop(0)  # header
        for line in lines:
            parts = line.strip().split()
            yield ProcInfo(int(parts[0]), int(parts[1]), parts[2], " ".join(parts[3:]))

    def pgrep(self, pattern):
        """
        Process grep: return information about all processes whose command-line args match the given regex pattern
        """
        pat = re.compile(pattern)
        for procinfo in self.list_processes():
            if pat.search(procinfo.args):
                yield procinfo

    @contextmanager
    def tempdir(self):
        """A context manager that creates a remote temporary directory, which is removed when
        the context exits"""
        _, out, _ = self._session.run(
            "mktemp -d 2>/dev/null || mktemp -d tmp.XXXXXXXXXX"
        )
        local_dir = self.path(out.strip())
        try:
            yield local_dir
        finally:
            local_dir.delete()

    #
    # Path implementation
    #
    def _path_listdir(self, fn):
        files = self._session.run(f"ls -a {shquote(fn)}")[1].splitlines()
        files.remove(".")
        files.remove("..")
        return files

    def _path_glob(self, fn, pattern):
        # shquote does not work here due to the way bash loops use space as a separator
        pattern = pattern.replace(" ", r"\ ")
        fn = fn.replace(" ", r"\ ")
        matches = self._session.run(rf"for fn in {fn}/{pattern}; do echo $fn; done")[
            1
        ].splitlines()
        if len(matches) == 1 and not self._path_stat(matches[0]):
            return []  # pattern expansion failed
        return matches

    def _path_getuid(self, fn):
        stat_cmd = (
            "stat -c '%u,%U' "
            if self.uname not in ("Darwin", "FreeBSD")
            else "stat -f '%u,%Su' "
        )
        return self._session.run(stat_cmd + shquote(fn))[1].strip().split(",")

    def _path_getgid(self, fn):
        stat_cmd = (
            "stat -c '%g,%G' "
            if self.uname not in ("Darwin", "FreeBSD")
            else "stat -f '%g,%Sg' "
        )
        return self._session.run(stat_cmd + shquote(fn))[1].strip().split(",")

    def _path_stat(self, fn):
        if self.uname not in ("Darwin", "FreeBSD"):
            stat_cmd = "stat -c '%F,%f,%i,%d,%h,%u,%g,%s,%X,%Y,%Z' "
        else:
            stat_cmd = "stat -f '%HT,%Xp,%i,%d,%l,%u,%g,%z,%a,%m,%c' "
        rc, out, _ = self._session.run(stat_cmd + shquote(fn), retcode=None)
        if rc != 0:
            return None
        statres = out.strip().split(",")
        text_mode = statres.pop(0).lower()
        res = StatRes((int(statres[0], 16),) + tuple(int(sr) for sr in statres[1:]))
        res.text_mode = text_mode
        return res

    def _path_delete(self, fn):
        self._session.run(f"rm -rf {shquote(fn)}")

    def _path_move(self, src, dst):
        self._session.run(f"mv {shquote(src)} {shquote(dst)}")

    def _path_copy(self, src, dst):
        self._session.run(f"cp -r {shquote(src)} {shquote(dst)}")

    def _path_mkdir(
        self,
        fn,
        mode=None,  # pylint: disable=unused-argument
        minus_p=True,
    ):
        p_str = "-p " if minus_p else ""
        cmd = f"mkdir {p_str}{shquote(fn)}"
        self._session.run(cmd)

    def _path_chmod(self, mode, fn):
        self._session.run(f"chmod {mode:o} {shquote(fn)}")

    def _path_touch(self, path):
        self._session.run(f"touch {path}")

    def _path_chown(self, fn, owner, group, recursive):
        args = ["chown"]
        if recursive:
            args.append("-R")
        if owner is not None and group is not None:
            args.append(f"{owner}:{group}")
        elif owner is not None:
            args.append(str(owner))
        elif group is not None:
            args.append(f":{group}")
        args.append(shquote(fn))
        self._session.run(" ".join(args))

    def _path_read(self, fn):
        data = self["cat"](fn)
        if self.custom_encoding and isinstance(data, str):
            data = data.encode(self.custom_encoding)
        return data

    def _path_write(self, fn, data):
        if self.custom_encoding and isinstance(data, str):
            data = data.encode(self.custom_encoding)
        with NamedTemporaryFile() as f:
            f.write(data)
            f.flush()
            f.seek(0)
            self.upload(f.name, fn)

    def _path_link(self, src, dst, symlink):
        symlink_str = "-s " if symlink else ""
        self._session.run(f"ln {symlink_str}{shquote(src)} {shquote(dst)}")

    def expand(self, expr):
        return self._session.run(f"echo {expr}")[1].strip()

    def expanduser(self, expr):
        if not any(part.startswith("~") for part in expr.split("/")):
            return expr
        # we escape all $ signs to avoid expanding env-vars
        expr_repl = expr.replace("$", "\\$")
        return self._session.run(f"echo {expr_repl}")[1].strip()
