"""The base class for xonsh shell"""
import io
import os
import sys
import time

from xonsh.ansi_colors import ansi_partial_color_format
from xonsh.built_ins import XSH
from xonsh.codecache import (
    code_cache_check,
    code_cache_name,
    get_cache_filename,
    run_compiled_code,
    should_use_cache,
    update_cache,
)
from xonsh.completer import Completer
from xonsh.events import events
from xonsh.lazyimps import pyghooks, pygments
from xonsh.platform import HAS_PYGMENTS, ON_WINDOWS
from xonsh.prompt.base import PromptFormatter, multiline_prompt
from xonsh.shell import transform_command
from xonsh.tools import (
    DefaultNotGiven,
    XonshError,
    check_for_partial_string,
    format_std_prepost,
    get_line_continuation,
    print_exception,
)

if ON_WINDOWS:
    import ctypes

    kernel32 = ctypes.windll.kernel32  # type:ignore
    kernel32.SetConsoleTitleW.argtypes = [ctypes.c_wchar_p]


class _TeeStdBuf(io.RawIOBase):
    """A dispatcher for bytes to two buffers, as std stream buffer and an
    in memory buffer.
    """

    def __init__(
        self, stdbuf, membuf, encoding=None, errors=None, prestd=b"", poststd=b""
    ):
        """
        Parameters
        ----------
        stdbuf : BytesIO-like or StringIO-like
            The std stream buffer.
        membuf : BytesIO-like
            The in memory stream buffer.
        encoding : str or None, optional
            The encoding of the stream. Only used if stdbuf is a text stream,
            rather than a binary one. Defaults to $XONSH_ENCODING if None.
        errors : str or None, optional
            The error form for the encoding of the stream. Only used if stdbuf
            is a text stream, rather than a binary one. Deafults to
            $XONSH_ENCODING_ERRORS if None.
        prestd : bytes, optional
            The prefix to prepend to the standard buffer.
        poststd : bytes, optional
            The postfix to append to the standard buffer.
        """
        self.stdbuf = stdbuf
        self.membuf = membuf
        env = XSH.env
        self.encoding = env.get("XONSH_ENCODING") if encoding is None else encoding
        self.errors = env.get("XONSH_ENCODING_ERRORS") if errors is None else errors
        self.prestd = prestd
        self.poststd = poststd
        self._std_is_binary = (not hasattr(stdbuf, "encoding")) or hasattr(
            stdbuf, "_redirect_to"
        )  # VS Code terminal window - has encoding attr but won't accept str

    def fileno(self):
        """Returns the file descriptor of the std buffer."""
        return self.stdbuf.fileno()

    def seek(self, offset, whence=io.SEEK_SET):
        """Sets the location in both the stdbuf and the membuf."""
        self.stdbuf.seek(offset, whence)
        self.membuf.seek(offset, whence)

    def truncate(self, size=None):
        """Truncate both buffers."""
        self.stdbuf.truncate(size)
        self.membuf.truncate(size)

    def readinto(self, b):
        """Read bytes into buffer from both streams."""
        if self._std_is_binary:
            self.stdbuf.readinto(b)
        return self.membuf.readinto(b)

    def write(self, b):
        """Write bytes into both buffers."""
        std_b = b
        if self.prestd:
            std_b = self.prestd + b
        if self.poststd:
            std_b += self.poststd
        # write to stdbuf
        if self._std_is_binary:
            self.stdbuf.write(std_b)
        else:
            self.stdbuf.write(std_b.decode(encoding=self.encoding, errors=self.errors))
        return self.membuf.write(b)


class _TeeStd(io.TextIOBase):
    """Tees a std stream into an in-memory container and the original stream."""

    def __init__(self, name, mem, prestd="", poststd=""):
        """
        Parameters
        ----------
        name : str
            The name of the buffer in the sys module, e.g. 'stdout'.
        mem : io.TextIOBase-like
            The in-memory text-based representation.
        prestd : str, optional
            The prefix to prepend to the standard stream.
        poststd : str, optional
            The postfix to append to the standard stream.
        """
        self._name = name
        self.std = std = getattr(sys, name)
        self.mem = mem
        self.prestd = prestd
        self.poststd = poststd
        preb = prestd.encode(encoding=mem.encoding, errors=mem.errors)
        postb = poststd.encode(encoding=mem.encoding, errors=mem.errors)
        if hasattr(std, "buffer"):
            buffer = _TeeStdBuf(std.buffer, mem.buffer, prestd=preb, poststd=postb)
        else:
            # TextIO does not have buffer as part of the API, so std streams
            # may not either.
            buffer = _TeeStdBuf(
                std,
                mem.buffer,
                encoding=mem.encoding,
                errors=mem.errors,
                prestd=preb,
                poststd=postb,
            )
        self.buffer = buffer
        setattr(sys, name, self)

    @property
    def encoding(self):
        """The encoding of the in-memory buffer."""
        return self.mem.encoding

    @property
    def errors(self):
        """The errors of the in-memory buffer."""
        return self.mem.errors

    @property
    def newlines(self):
        """The newlines of the in-memory buffer."""
        return self.mem.newlines

    def _replace_std(self):
        std = self.std
        if std is None:
            return
        setattr(sys, self._name, std)
        self.std = self._name = None

    def __del__(self):
        self._replace_std()

    def close(self):
        """Restores the original std stream."""
        self._replace_std()

    def write(self, s):
        """Writes data to the original std stream and the in-memory object."""
        self.mem.write(s)
        if self.std is None:
            return
        std_s = s
        if self.prestd:
            std_s = self.prestd + std_s
        if self.poststd:
            std_s += self.poststd
        self.std.write(std_s)

    def flush(self):
        """Flushes both the original stdout and the buffer."""
        # In certain cases, `std` or `mem` may already be `None` when we're
        # cleaning up in which case we don't care whether `flush` does anything
        getattr(getattr(self, "std", lambda: None), "flush", lambda: None)()
        getattr(getattr(self, "mem", lambda: None), "flush", lambda: None)()

    def fileno(self):
        """Tunnel fileno() calls to the std stream."""
        return self.std.fileno()

    def seek(self, offset, whence=io.SEEK_SET):
        """Seek to a location in both streams."""
        self.std.seek(offset, whence)
        self.mem.seek(offset, whence)

    def truncate(self, size=None):
        """Seek to a location in both streams."""
        self.std.truncate(size)
        self.mem.truncate(size)

    def detach(self):
        """This operation is not supported."""
        raise io.UnsupportedOperation

    def read(self, size=None):
        """Read from the in-memory stream and seek to a new location in the
        std stream.
        """
        s = self.mem.read(size)
        loc = self.std.tell()
        self.std.seek(loc + len(s))
        return s

    def readline(self, size=-1):
        """Read a line from the in-memory stream and seek to a new location
        in the std stream.
        """
        s = self.mem.readline(size)
        loc = self.std.tell()
        self.std.seek(loc + len(s))
        return s

    def isatty(self) -> bool:
        """delegate the method to the underlying io-wrapper"""
        if self.std:  # it happens to be reset sometimes
            return self.std.isatty()
        return super().isatty()


class Tee:
    """Class that merges tee'd stdout and stderr into a single stream.

    This represents what a user would actually see on the command line.
    This class has the same interface as io.TextIOWrapper, except that
    the buffer is optional.
    """

    # pylint is a stupid about counting public methods when using inheritance.
    # pylint: disable=too-few-public-methods

    def __init__(
        self,
        buffer=None,
        encoding=None,
        errors=None,
        newline=None,
        line_buffering=False,
        write_through=False,
    ):
        self.buffer = io.BytesIO() if buffer is None else buffer
        self.memory = io.TextIOWrapper(
            self.buffer,
            encoding=encoding,
            errors=errors,
            newline=newline,
            line_buffering=line_buffering,
            write_through=write_through,
        )
        self.stdout = _TeeStd("stdout", self.memory)
        env = XSH.env
        prestderr = format_std_prepost(env.get("XONSH_STDERR_PREFIX"))
        poststderr = format_std_prepost(env.get("XONSH_STDERR_POSTFIX"))
        self.stderr = _TeeStd(
            "stderr", self.memory, prestd=prestderr, poststd=poststderr
        )

    @property
    def line_buffering(self):
        return self.memory.line_buffering

    def __del__(self):
        del self.stdout, self.stderr
        self.stdout = self.stderr = None

    def close(self):
        """Closes the buffer as well as the stdout and stderr tees."""
        self.stdout.close()
        self.stderr.close()
        self.memory.close()

    def getvalue(self):
        """Gets the current contents of the in-memory buffer."""
        m = self.memory
        loc = m.tell()
        m.seek(0)
        s = m.read()
        m.seek(loc)
        return s


class BaseShell:
    """The xonsh shell."""

    def __init__(self, execer, ctx, **kwargs):
        """

        Notes
        -----
        classes inheriting multiple base classes should call them explicitly
        as done for ``ReadlineShell``
        """

        self.execer = execer
        self.ctx = ctx
        self.completer = Completer() if kwargs.get("completer", True) else None
        self.buffer = []
        self.need_more_lines = False
        self.src_starts_with_space = False
        self.mlprompt = None
        self._styler = DefaultNotGiven
        self.prompt_formatter = PromptFormatter()
        self.accumulated_inputs = ""
        self.precwd = (
            None  # The current working directory just before execution of the line
        )

    @property
    def styler(self):
        if self._styler is DefaultNotGiven:
            if HAS_PYGMENTS:
                from xonsh.pyghooks import XonshStyle

                env = XSH.env
                self._styler = XonshStyle(env.get("XONSH_COLOR_STYLE"))
            else:
                self._styler = None
        return self._styler

    @styler.setter
    def styler(self, value):
        self._styler = value

    @styler.deleter
    def styler(self):
        self._styler = DefaultNotGiven

    def emptyline(self):
        """Called when an empty line has been entered."""
        self.need_more_lines = False
        self.default("")

    def singleline(self, **kwargs):
        """Reads a single line of input from the shell."""
        msg = "{0} has not implemented singleline()."
        raise RuntimeError(msg.format(self.__class__.__name__))

    def precmd(self, line):
        """Called just before execution of line."""
        try:
            self.precwd = os.getcwd()
        except FileNotFoundError:
            self.precwd = os.path.expanduser("~")
        return line if self.need_more_lines else line.lstrip()

    def default(self, line, raw_line=None):
        """Implements code execution."""
        line = line if line.endswith("\n") else line + "\n"
        if not self.need_more_lines:  # this is the first line
            if not raw_line:
                self.src_starts_with_space = False
            else:
                self.src_starts_with_space = raw_line[0].isspace()
        src, code = self.push(line)
        if code is None:
            return

        events.on_precommand.fire(cmd=src)

        env = XSH.env
        hist = XSH.history  # pylint: disable=no-member
        ts1 = None
        enc = env.get("XONSH_ENCODING")
        err = env.get("XONSH_ENCODING_ERRORS")
        tee = Tee(encoding=enc, errors=err)
        ts0 = time.time()
        try:
            exc_info = run_compiled_code(code, self.ctx, None, "single")
            if exc_info != (None, None, None):
                raise exc_info[1]
            ts1 = time.time()
            if hist is not None and hist.last_cmd_rtn is None:
                hist.last_cmd_rtn = 0  # returncode for success
        except XonshError as e:
            print(e.args[0], file=sys.stderr)
            if hist is not None and hist.last_cmd_rtn is None:
                hist.last_cmd_rtn = 1  # return code for failure
        except (SystemExit, KeyboardInterrupt) as err:
            raise err
        except BaseException:
            print_exception(exc_info=exc_info)
            if hist is not None and hist.last_cmd_rtn is None:
                hist.last_cmd_rtn = 1  # return code for failure
        finally:
            ts1 = ts1 or time.time()
            tee_out = tee.getvalue()
            self._append_history(
                inp=src,
                ts=[ts0, ts1],
                spc=self.src_starts_with_space,
                tee_out=tee_out,
                cwd=self.precwd,
            )
            self.accumulated_inputs += src
            if (
                tee_out
                and env.get("XONSH_APPEND_NEWLINE")
                and not tee_out.endswith(os.linesep)
            ):
                print(os.linesep, end="")
            tee.close()
            self._fix_cwd()
        if XSH.exit:  # pylint: disable=no-member
            return True

    def _append_history(self, tee_out=None, **info):
        """Append information about the command to the history.

        This also handles on_postcommand because this is the place where all the
        information is available.
        """
        hist = XSH.history  # pylint: disable=no-member
        info["rtn"] = hist.last_cmd_rtn if hist is not None else None
        XSH.env["LAST_RETURN_CODE"] = info["rtn"] or 0
        tee_out = tee_out or None
        last_out = hist.last_cmd_out if hist is not None else None
        if last_out is None and tee_out is None:
            pass
        elif last_out is None and tee_out is not None:
            info["out"] = tee_out
        elif last_out is not None and tee_out is None:
            info["out"] = last_out
        else:
            info["out"] = tee_out + "\n" + last_out
        events.on_postcommand.fire(
            cmd=info["inp"], rtn=info["rtn"], out=info.get("out", None), ts=info["ts"]
        )
        if hist is not None:
            hist.append(info)
            hist.last_cmd_rtn = hist.last_cmd_out = None

    def _fix_cwd(self):
        """Check if the cwd changed out from under us."""
        env = XSH.env
        try:
            cwd = os.getcwd()
        except OSError:
            cwd = None
        if cwd is None:
            # directory has been deleted out from under us, most likely
            pwd = env.get("PWD", None)
            if pwd is None:
                # we have no idea where we are
                env["PWD"] = "<invalid directory>"
            elif os.path.isdir(pwd):
                # unclear why os.getcwd() failed. do nothing.
                pass
            else:
                # OK PWD is really gone.
                msg = "{UNDERLINE_INTENSE_WHITE}{BACKGROUND_INTENSE_BLACK}"
                msg += "xonsh: working directory does not exist: " + pwd
                msg += "{RESET}"
                self.print_color(msg, file=sys.stderr)
        elif "PWD" not in env:
            # $PWD is missing from env, recreate it
            env["PWD"] = cwd
        elif os.path.realpath(cwd) != os.path.realpath(env["PWD"]):
            # The working directory has changed without updating $PWD, fix this
            old = env["PWD"]
            env["PWD"] = cwd
            env["OLDPWD"] = old
            events.on_chdir.fire(olddir=old, newdir=cwd)

    def push(self, line):
        """Pushes a line onto the buffer and compiles the code in a way that
        enables multiline input.
        """
        self.buffer.append(line)
        if self.need_more_lines:
            return None, None
        src = "".join(self.buffer)
        src = transform_command(src)
        return self.compile(src)

    def compile(self, src):
        """Compiles source code and returns the (possibly modified) source and
        a valid code object.
        """
        _cache = should_use_cache(self.execer, "single")
        if _cache:
            codefname = code_cache_name(src)
            cachefname = get_cache_filename(codefname, code=True)
            usecache, code = code_cache_check(cachefname)
            if usecache:
                self.reset_buffer()
                return src, code
        lincont = get_line_continuation()
        if src.endswith(lincont + "\n"):
            self.need_more_lines = True
            return src, None
        try:
            code = self.execer.compile(
                src,
                mode="single",
                glbs=self.ctx,
                locs=None,
                filename="<stdin>",
                compile_empty_tree=False,
            )
            if _cache:
                update_cache(code, cachefname)
            self.reset_buffer()
        except SyntaxError:
            partial_string_info = check_for_partial_string(src)
            in_partial_string = (
                partial_string_info[0] is not None and partial_string_info[1] is None
            )
            if (src == "\n" or src.endswith("\n\n")) and not in_partial_string:
                self.reset_buffer()
                print_exception()
                return src, None
            self.need_more_lines = True
            code = None
        except Exception:  # pylint: disable=broad-except
            self.reset_buffer()
            print_exception()
            code = None
        return src, code

    def reset_buffer(self):
        """Resets the line buffer."""
        self.buffer.clear()
        self.need_more_lines = False
        self.mlprompt = None

    def settitle(self):
        """Sets terminal title."""
        env = XSH.env  # pylint: disable=no-member
        term = env.get("TERM", None)
        # Shells running in emacs sets TERM to "dumb" or "eterm-color".
        # Do not set title for these to avoid garbled prompt.
        if (term is None and not ON_WINDOWS) or term in [
            "dumb",
            "eterm-color",
            "linux",
        ]:
            return
        t = env.get("TITLE")
        if t is None:
            return
        t = self.prompt_formatter(t)
        if ON_WINDOWS and "ANSICON" not in env:
            kernel32.SetConsoleTitleW(t)
        else:
            with open(1, "wb", closefd=False) as f:
                # prevent xonsh from answering interactive questions
                # on the next command by writing the title
                f.write(f"\x1b]0;{t}\x07".encode())
                f.flush()

    @property
    def prompt(self):
        """Obtains the current prompt string."""

        # clear prompt level cache
        XSH.env["PROMPT_FIELDS"].reset()

        if self.need_more_lines:
            if self.mlprompt is None:
                try:
                    self.mlprompt = multiline_prompt()
                except Exception:  # pylint: disable=broad-except
                    print_exception()
                    self.mlprompt = "<multiline prompt error> "
            return self.mlprompt
        env = XSH.env  # pylint: disable=no-member
        p = env.get("PROMPT")
        try:
            p = self.prompt_formatter(p)
        except Exception:  # pylint: disable=broad-except
            print_exception()
        self.settitle()
        return p

    def format_color(self, string, hide=False, force_string=False, **kwargs):
        """Formats the colors in a string. ``BaseShell``'s default implementation
        of this method uses colors based on ANSI color codes.
        """
        style = XSH.env.get("XONSH_COLOR_STYLE")
        return ansi_partial_color_format(string, hide=hide, style=style)

    def print_color(self, string, hide=False, **kwargs):
        """Prints a string in color. This base implementation's colors are based
        on ANSI color codes if a string was given as input. If a list of token
        pairs is given, it will color based on pygments, if available. If
        pygments is not available, it will print a colorless string.
        """
        if isinstance(string, str):
            s = self.format_color(string, hide=hide)
        elif HAS_PYGMENTS:
            # assume this is a list of (Token, str) tuples and format it
            env = XSH.env
            self.styler.style_name = env.get("XONSH_COLOR_STYLE")
            style_proxy = pyghooks.xonsh_style_proxy(self.styler)
            formatter = pyghooks.XonshTerminal256Formatter(style=style_proxy)
            s = pygments.format(string, formatter).rstrip()
        else:
            # assume this is a list of (Token, str) tuples and remove color
            s = "".join([x for _, x in string])
        print(s, **kwargs)

    def color_style_names(self):
        """Returns an iterable of all available style names."""
        return ()

    def color_style(self):
        """Returns the current color map."""
        return {}

    def restore_tty_sanity(self):
        """An interface for resetting the TTY stdin mode. This is highly
        dependent on the shell backend. Also it is mostly optional since
        it only affects ^Z backgrounding behaviour.
        """
        pass
