import collections
import contextlib
import os
import re
import signal
import subprocess
import sys
from pathlib import Path
from shutil import get_terminal_size

from pipenv.utils.shell import temp_environ
from pipenv.vendor import shellingham

ShellDetectionFailure = shellingham.ShellDetectionFailure


def _build_info(value):
    path = Path(value)
    return (path.stem, value)


def detect_info(project):
    if project.s.PIPENV_SHELL_EXPLICIT:
        return _build_info(project.s.PIPENV_SHELL_EXPLICIT)
    try:
        return shellingham.detect_shell()
    except (shellingham.ShellDetectionFailure, TypeError):
        if project.s.PIPENV_SHELL:
            return _build_info(project.s.PIPENV_SHELL)
    raise ShellDetectionFailure


def _get_activate_script(cmd, venv):
    """Returns the string to activate a virtualenv.

    This is POSIX-only at the moment since the compat (pexpect-based) shell
    does not work elsewhere anyway.
    """
    # Suffix and source command for various shells.
    command = "source"

    if cmd.endswith("fish"):
        suffix = ".fish"
    elif cmd.endswith("csh"):
        suffix = ".csh"
    elif cmd.endswith("xonsh"):
        suffix = ".xsh"
    elif cmd.endswith("nu"):
        suffix = ".nu"
        command = "overlay use"
    elif cmd.endswith(("pwsh", "powershell")):
        suffix = ".ps1"
        command = "."
    elif cmd.endswith(("sh", "bash", "zsh")):
        suffix = ""
    else:
        sys.exit(f"unknown shell {cmd}")

    # Escape any special characters located within the virtualenv path to allow
    # for proper activation.
    venv_location = re.sub(r"([ &$()\[\]])", r"\\\1", str(venv))

    if suffix == "nu":
        return f"overlay use {venv_location}"
    elif suffix == ".ps1" and os.name == "nt":
        return f". {venv_location}\\Scripts\\Activate{suffix}"

    # The leading space can make history cleaner in some shells.
    return f" {command} {venv_location}/bin/activate{suffix}"


def _get_deactivate_wrapper_script(cmd):
    """Returns a script to wrap the deactivate function to also unset PIPENV_ACTIVE.

    This ensures that when a user runs 'deactivate' in a pipenv shell, the
    PIPENV_ACTIVE environment variable is also cleared, allowing subsequent
    'pipenv shell' commands to work without the 'already activated' error.
    """
    if cmd.endswith("fish"):
        # Fish shell uses 'functions' and 'set -e' to unset variables
        return (
            "functions -c deactivate _pipenv_old_deactivate; "
            "function deactivate; _pipenv_old_deactivate; set -e PIPENV_ACTIVE; end"
        )
    elif cmd.endswith("csh"):
        # C shell uses 'unsetenv'
        return (
            "alias _pipenv_old_deactivate deactivate; "
            "alias deactivate '_pipenv_old_deactivate; unsetenv PIPENV_ACTIVE'"
        )
    elif cmd.endswith("xonsh"):
        # Xonsh uses Python-like syntax
        return (
            "_pipenv_old_deactivate = deactivate; "
            "def deactivate(): _pipenv_old_deactivate(); del $PIPENV_ACTIVE"
        )
    elif cmd.endswith("nu"):
        # Nushell - deactivate is typically handled differently
        # For now, return empty as nu has different paradigm
        return ""
    elif cmd.endswith(("pwsh", "powershell")):
        # PowerShell
        return (
            "$_pipenv_old_deactivate = $function:deactivate; "
            "function deactivate { & $_pipenv_old_deactivate; "
            "Remove-Item Env:PIPENV_ACTIVE -ErrorAction SilentlyContinue }"
        )
    elif cmd.endswith("zsh"):
        # Zsh uses 'functions -c' to copy function definitions
        return (
            "functions -c deactivate _pipenv_old_deactivate; "
            "deactivate() { _pipenv_old_deactivate; unset PIPENV_ACTIVE; }"
        )
    elif cmd.endswith("bash"):
        # Bash uses 'declare -f' to copy function definitions
        return (
            'eval "_pipenv_old_deactivate() { $(declare -f deactivate | tail -n +2) }"; '
            "deactivate() { _pipenv_old_deactivate; unset PIPENV_ACTIVE; }"
        )
    elif cmd.endswith("sh"):
        # Plain POSIX sh doesn't have 'declare -f', use a simpler approach
        # Just redefine deactivate to call the original via sourcing and add unset
        return "deactivate() { command deactivate 2>/dev/null; unset PIPENV_ACTIVE; }"
    else:
        # Unknown shell - return empty string
        return ""


def _handover(cmd, args):
    args = [cmd] + args
    if os.name != "nt":
        os.execvp(cmd, args)
    else:
        sys.exit(subprocess.call(args, universal_newlines=True))


class Shell:
    def __init__(self, cmd):
        self.cmd = cmd
        self.args = []

    def __repr__(self):
        return f"{type(self).__name__}(cmd={repr(self.cmd)}, args={repr(self.args)})"

    @contextlib.contextmanager
    def inject_path(self, venv):
        venv_path = Path(venv)
        with temp_environ():
            os.environ["PATH"] = (
                f"{os.pathsep.join(str(p.parent) for p in _iter_python(venv_path))}{os.pathsep}{os.environ['PATH']}"
            )
            yield

    def fork(self, venv, cwd, args):
        # FIXME: This isn't necessarily the correct prompt. We should read the
        # actual prompt by peeking into the activation script.
        venv_path = Path(venv)
        name = venv_path.name
        os.environ["VIRTUAL_ENV"] = str(venv_path)
        if "PROMPT" in os.environ:
            os.environ["PROMPT"] = f"({name}) {os.environ['PROMPT']}"
        if "PS1" in os.environ:
            os.environ["PS1"] = f"({name}) {os.environ['PS1']}"
        with self.inject_path(venv):
            os.chdir(str(cwd) if isinstance(cwd, Path) else cwd)
            _handover(self.cmd, self.args + list(args))

    def fork_compat(self, venv, cwd, args, quiet=False):
        from .vendor import pexpect

        # Grab current terminal dimensions to replace the hardcoded default
        # dimensions of pexpect.
        dims = get_terminal_size()
        with temp_environ():
            # Unset COLUMNS and LINES so the spawned shell can manage them.
            # When these are exported, Bash treats them as read-only inherited
            # values and doesn't update them on terminal resize, even with
            # checkwinsize enabled. See: https://github.com/pypa/pipenv/issues/6169
            os.environ.pop("COLUMNS", None)
            os.environ.pop("LINES", None)
            c = pexpect.spawn(self.cmd, ["-i"], dimensions=(dims.lines, dims.columns))

        # In quiet mode, disable echo to suppress activation command output
        # See: https://github.com/pypa/pipenv/issues/5954
        if quiet:
            try:
                c.setecho(False)
            except Exception:
                pass  # setecho may not be supported on all platforms

        c.sendline(_get_activate_script(self.cmd, venv))

        # Wrap the deactivate function to also unset PIPENV_ACTIVE
        deactivate_wrapper = _get_deactivate_wrapper_script(self.cmd)
        if deactivate_wrapper:
            c.sendline(deactivate_wrapper)

        if args:
            c.sendline(" ".join(args))

        # Re-enable echo after sending activation commands
        if quiet:
            try:
                c.setecho(True)
            except Exception:
                pass

        # Handler for terminal resizing events
        # Must be defined here to have the shell process in its context, since
        # we can't pass it as an argument
        def sigwinch_passthrough(sig, data):
            dims = get_terminal_size()
            c.setwinsize(dims.lines, dims.columns)

        signal.signal(signal.SIGWINCH, sigwinch_passthrough)

        # Interact with the new shell.
        c.interact(escape_character=None)
        c.close()
        sys.exit(c.exitstatus)


POSSIBLE_ENV_PYTHON = [Path("bin", "python"), Path("Scripts", "python.exe")]


def _iter_python(venv):
    for path in POSSIBLE_ENV_PYTHON:
        full_path = Path(venv, path)
        if full_path.is_file():
            yield full_path


class Bash(Shell):
    def _format_path(self, python):
        return python.parent.as_posix()

    # The usual PATH injection technique does not work with Bash.
    # https://github.com/berdario/pew/issues/58#issuecomment-102182346
    @contextlib.contextmanager
    def inject_path(self, venv):
        from tempfile import NamedTemporaryFile

        bashrc_path = Path.home().joinpath(".bashrc")
        with NamedTemporaryFile("w+") as rcfile:
            if bashrc_path.is_file():
                base_rc_src = f'source "{bashrc_path.as_posix()}"\n'
                rcfile.write(base_rc_src)

            export_path = 'export PATH="{}:$PATH"\n'.format(
                ":".join(self._format_path(python) for python in _iter_python(venv))
            )
            rcfile.write(export_path)
            rcfile.flush()
            self.args.extend(["--rcfile", rcfile.name])
            yield


class MsysBash(Bash):
    def _format_path(self, python):
        s = super()._format_path(python)
        if not python.drive:
            return s
        # Convert "C:/something" to "/c/something".
        return f"/{s[0].lower()}{s[2:]}"


class CmderEmulatedShell(Shell):
    def fork(self, venv, cwd, args):
        if cwd:
            os.environ["CMDER_START"] = cwd
        super().fork(venv, cwd, args)


class CmderCommandPrompt(CmderEmulatedShell):
    def fork(self, venv, cwd, args):
        rc_path = Path(os.path.expandvars("%CMDER_ROOT%\\vendor\\init.bat"))
        if rc_path.exists():
            self.args.extend(["/k", str(rc_path)])
        super().fork(venv, cwd, args)


class CmderPowershell(Shell):
    def fork(self, venv, cwd, args):
        rc_path = Path(os.path.expandvars("%CMDER_ROOT%\\vendor\\profile.ps1"))
        if rc_path.exists():
            self.args.extend(
                [
                    "-ExecutionPolicy",
                    "Bypass",
                    "-NoLogo",
                    "-NoProfile",
                    "-NoExit",
                    "-Command",
                    f"Invoke-Expression '. ''{rc_path}'''",
                ]
            )
        super().fork(venv, cwd, args)


# Two dimensional dict. First is the shell type, second is the emulator type.
# Example: SHELL_LOOKUP['powershell']['cmder'] => CmderPowershell.
SHELL_LOOKUP = collections.defaultdict(
    lambda: collections.defaultdict(lambda: Shell),
    {
        "bash": collections.defaultdict(
            lambda: Bash,
            {"msys": MsysBash},
        ),
        "cmd": collections.defaultdict(
            lambda: Shell,
            {"cmder": CmderCommandPrompt},
        ),
        "powershell": collections.defaultdict(
            lambda: Shell,
            {"cmder": CmderPowershell},
        ),
        "pwsh": collections.defaultdict(
            lambda: Shell,
            {"cmder": CmderPowershell},
        ),
    },
)


def _detect_emulator():
    keys = []
    if os.environ.get("CMDER_ROOT"):
        keys.append("cmder")
    if os.environ.get("MSYSTEM"):
        keys.append("msys")
    return ",".join(keys)


def choose_shell(project):
    emulator = project.s.PIPENV_EMULATOR.lower() or _detect_emulator()
    type_, command = detect_info(project)
    shell_types = SHELL_LOOKUP[type_]
    for key in emulator.split(","):
        key = key.strip().lower()
        if key in shell_types:
            return shell_types[key](command)
    return shell_types[""](command)
