"""Base prompt, provides PROMPT_FIELDS and prompt related functions"""

import itertools
import os
import re
import socket
import sys
import typing as tp

import xonsh.platform as xp
import xonsh.tools as xt
from xonsh.built_ins import XSH

if tp.TYPE_CHECKING:
    from xonsh.built_ins import XonshSession

    FieldType = tp.TypeVar("FieldType", bound="BasePromptField")


def _current_username():
    """Get the current username from the OS, not from environment variables.

    On POSIX, ``$USER`` may be stale after ``su`` (su does not update it
    for the root user).  Use ``pwd.getpwuid`` which always reflects the
    real effective user.
    """
    if xp.ON_WINDOWS:
        return xp.os_environ.get("USERNAME", "<user>")
    import pwd

    return pwd.getpwuid(os.getuid()).pw_name


@xt.lazyobject
def DEFAULT_PROMPT():
    return default_prompt()


class _ParsedToken(tp.NamedTuple):
    """It can either be a literal value alone or a field and its resultant value"""

    value: str
    field: str | None = None


class ParsedTokens(tp.NamedTuple):
    tokens: list[_ParsedToken]
    template: str | tp.Callable

    def process(self) -> str:
        """Wrapper that gets formatter-function from environment and returns final prompt."""
        processor = XSH.env.get(  # type: ignore
            "PROMPT_TOKENS_FORMATTER", prompt_tokens_formatter_default
        )
        return processor(self)

    def update(
        self,
        idx: int,
        val: str | None,
        spec: str | None,
        conv: str | None,
    ) -> None:
        """Update tokens list in-place"""
        if idx < len(self.tokens):
            tok = self.tokens[idx]
            self.tokens[idx] = _ParsedToken(_format_value(val, spec, conv), tok.field)


def prompt_tokens_formatter_default(container: ParsedTokens) -> str:
    """
        Join the tokens

    Parameters
    ----------
    container: ParsedTokens
        parsed tokens holder

    Returns
    -------
    str
        process the tokens and finally return the prompt string
    """
    return "".join([tok.value for tok in container.tokens])


class PromptFormatter:
    """Class that holds all the related prompt formatting methods,
    uses the ``PROMPT_FIELDS`` envvar (no color formatting).
    """

    def __call__(self, template=DEFAULT_PROMPT, fields=None, **kwargs) -> str:
        """Formats a xonsh prompt template string."""

        if fields is None:
            self.fields = XSH.env["PROMPT_FIELDS"]  # type: ignore
        else:
            self.fields = fields

        # some quick tests
        if isinstance(fields, dict):
            pflds: PromptFields[PromptField] = PromptFields(XSH, init=False)
            pflds.update(fields)
            self.fields = pflds

        try:
            toks = self._format_prompt(template=template, **kwargs)
            prompt = toks.process()
        except Exception as ex:
            # make it obvious why it has failed
            import logging

            logging.error(str(ex), exc_info=True)
            xt.print_exception(
                f"Failed to format prompt `{template}`-> {type(ex)}:{ex}"
            )
            return _failover_template_format(template)
        return prompt

    def _format_prompt(self, template=DEFAULT_PROMPT, **kwargs) -> ParsedTokens:
        tmpl = template() if callable(template) else template
        toks = []
        for literal, field, spec, conv in xt.FORMATTER.parse(tmpl):
            if literal:
                toks.append(_ParsedToken(literal))
            entry = self._format_field(field, spec, conv, idx=len(toks), **kwargs)
            if entry is not None:
                toks.append(_ParsedToken(entry, field))

        return ParsedTokens(toks, template)

    def _format_field(self, field, spec="", conv=None, **kwargs):
        if field is None:
            return
        elif field.startswith("$"):
            val = XSH.env[field[1:]]
            return _format_value(val, spec, conv)
        elif field in self.fields:
            val = self._get_field_value(field, spec=spec, conv=conv, **kwargs)
            return _format_value(val, spec, conv)
        else:
            # color or unknown field, return as is
            return "{" + field + "}"

    def _get_field_value(self, field, **_):
        try:
            return self.fields.pick(field)
        except Exception:  # noqa
            print(f"prompt: error: on field {field!r}", file=sys.stderr)
            xt.print_exception()
            value = f"{{BACKGROUND_RED}}{{ERROR:{field}}}{{RESET}}"
        return value


def default_prompt():
    """Creates a new instance of the default prompt."""
    if xp.ON_CYGWIN or xp.ON_MSYS:
        dp = (
            "{YELLOW}{env_name}{RESET}"
            "{BOLD_GREEN}{user}@{hostname}"
            "{BOLD_BLUE} {cwd} {prompt_end}{RESET} "
        )
    elif xp.ON_WINDOWS and not xp.win_ansi_support():
        dp = (
            "{YELLOW}{env_name}{RESET}"
            "{BOLD_INTENSE_GREEN}{user}@{hostname}{BOLD_INTENSE_CYAN} "
            "{cwd}{branch_color}{curr_branch: {}}{RESET} "
            "{BOLD_INTENSE_CYAN}{prompt_end}{RESET} "
        )
    else:
        dp = (
            "{YELLOW}{env_name}{RESET}"
            "{BOLD_GREEN}{user}@{hostname}{BOLD_BLUE} "
            "{cwd}{branch_color}{curr_branch: {}}{RESET} "
            "{RED}{last_return_code_if_nonzero:[{BOLD_INTENSE_RED}{}{RED}] }{RESET}"
            "{BOLD_BLUE}{prompt_end}{RESET} "
        )
    return dp


def _failover_template_format(template):
    if callable(template):
        try:
            # Exceptions raises from function of producing $PROMPT
            # in user's xonshrc should not crash xonsh
            return template()
        except Exception:
            xt.print_exception()
            return "$ "
    return template


@xt.lazyobject
def RE_HIDDEN():
    return re.compile("\001.*?\002")


def multiline_prompt(curr=""):
    """Returns the filler text for the prompt in multiline scenarios."""
    line = curr.rsplit("\n", 1)[1] if "\n" in curr else curr
    line = RE_HIDDEN.sub("", line)  # gets rid of colors
    # most prompts end in whitespace, head is the part before that.
    head = line.rstrip()
    headlen = len(head)
    # tail is the trailing whitespace
    tail = line if headlen == 0 else line.rsplit(head[-1], 1)[1]
    # now to construct the actual string
    dots = XSH.env.get("MULTILINE_PROMPT")
    dots = dots() if callable(dots) else dots
    if dots is None or len(dots) == 0:
        return ""
    tokstr = xt.format_color(dots, hide=True)
    baselen = 0
    basetoks = []
    for x in tokstr.split("\001"):
        pre, sep, post = x.partition("\002")
        if len(sep) == 0:
            basetoks.append(("", pre))
            baselen += len(pre)
        else:
            basetoks.append(("\001" + pre + "\002", post))
            baselen += len(post)
    if baselen == 0:
        return xt.format_color("{RESET}" + tail, hide=True)
    toks = basetoks * (headlen // baselen)
    n = headlen % baselen
    count = 0
    for tok in basetoks:
        slen = len(tok[1])
        newcount = slen + count
        if slen == 0:
            continue
        elif newcount <= n:
            toks.append(tok)
        else:
            toks.append((tok[0], tok[1][: n - count]))
        count = newcount
        if n <= count:
            break
    toks.append((xt.format_color("{RESET}", hide=True), tail))
    rtn = "".join(itertools.chain.from_iterable(toks))
    return rtn


def is_template_string(template, PROMPT_FIELDS=None):
    """Returns whether or not the string is a valid template."""
    template = template() if callable(template) else template
    try:
        included_names = {i[1] for i in xt.FORMATTER.parse(template)}
    except ValueError:
        return False
    included_names.discard(None)
    if PROMPT_FIELDS is None:
        fmtter = XSH.env.get("PROMPT_FIELDS", PROMPT_FIELDS)
    else:
        fmtter = PROMPT_FIELDS
    known_names = set(fmtter.keys())
    return included_names <= known_names


def _format_value(val, spec, conv) -> str:
    """Formats a value from a template string {val!conv:spec}. The spec is
    applied as a format string itself, but if the value is None, the result
    will be empty. The purpose of this is to allow optional parts in a
    prompt string. For example, if the prompt contains '{current_job:{} | }',
    and 'current_job' returns 'sleep', the result is 'sleep | ', and if
    'current_job' returns None, the result is ''.
    """
    if val is None or (isinstance(val, BasePromptField) and val.value is None):
        return ""
    val = xt.FORMATTER.convert_field(val, conv)

    if spec:
        val = xt.FORMATTER.format(spec, val)
    if not isinstance(val, str):
        val = format(val)
    return val


class PromptFields(tp.MutableMapping[str, "FieldType"]):
    """Mapping of functions available for prompt-display."""

    def __init__(self, xsh: "XonshSession", init=True):
        self._items: dict[str, str | tp.Callable[..., str]] = {}

        self._cache: dict[str, str | FieldType] = {}
        """for callbacks this will catch the value and should be cleared between prompts"""

        self.xsh = xsh
        if init:
            self.load_initial()

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

    def _repr_pretty_(self, p, cycle):
        name = f"{self.__class__.__module__}.{self.__class__.__name__}"
        with p.group(1, name + "(", ")"):
            if cycle:
                p.text("...")
            elif len(self):
                p.break_()
                p.pretty(dict(self))

    def __getitem__(self, item: "str|BasePromptField"):
        # todo: load on-demand from modules
        if isinstance(item, BasePromptField):
            item = item.name
        return self._items[item]

    def __delitem__(self, key):
        del self._items[key]

    def __iter__(self):
        yield from self._items

    def __len__(self):
        return len(self._items)

    def __setitem__(self, key, value):
        self._items[key] = value

    def get_fields(self, module):
        """Find and load all instances of PromptField from the given module.

        Each module is expected to have a single prompt-field with the same name as the module
        """
        mod_name = module.__name__.replace(module.__package__, "", 1).replace(
            ".", "", 1
        )
        for attr, val in vars(module).items():
            if isinstance(val, BasePromptField):
                if attr == mod_name:
                    name = attr
                else:
                    name = f"{mod_name}.{attr}"
                val.name = name
                yield val

    def load_initial(self):
        from xonsh.prompt import gitstatus
        from xonsh.prompt.cwd import (
            _collapsed_pwd,
            _dynamically_collapsed_pwd,
            _replace_home_cwd,
        )
        from xonsh.prompt.env import env_name, vte_new_tab_cwd
        from xonsh.prompt.job import CurrentJobField
        from xonsh.prompt.times import _localtime
        from xonsh.prompt.vc import branch_bg_color, branch_color, current_branch

        self.update(
            dict(
                user=_current_username(),
                prompt_end="@#" if xt.is_superuser() else "@",
                hostname=socket.gethostname().split(".", 1)[0],
                cwd=_dynamically_collapsed_pwd,
                cwd_dir=lambda: os.path.join(os.path.dirname(_replace_home_cwd()), ""),
                cwd_base=lambda: os.path.basename(_replace_home_cwd()),
                short_cwd=_collapsed_pwd,
                curr_branch=current_branch,
                branch_color=branch_color,
                branch_bg_color=branch_bg_color,
                current_job=CurrentJobField(name="current_job"),
                env_name=env_name,
                env_prefix="(",
                env_postfix=") ",
                vte_new_tab_cwd=vte_new_tab_cwd,
                time_format="%H:%M:%S",
                localtime=_localtime,
                last_return_code=lambda: XSH.env.get("LAST_RETURN_CODE", 0),
                last_return_code_if_nonzero=lambda: (
                    XSH.env.get("LAST_RETURN_CODE", 0) or None
                ),
            )
        )
        for val in self.get_fields(gitstatus):
            self[val.name] = val

    def pick(self, key: "str|FieldType") -> "str | FieldType | None":
        """Get the value of the prompt-field

        Notes
        -----
            If it is callable, then the result of the callable is returned.
            If it is a PromptField then it is updated
        """
        name = key if isinstance(key, str) else key.name
        if name not in self._items:
            return None
        value = self._items[name]
        if name not in self._cache:
            if isinstance(value, BasePromptField):
                value.update(self)
            elif callable(value):
                value = value()

            # store in cache
            self._cache[name] = value
        return self._cache[name]

    def pick_val(self, key):
        """wrap .pick() method to get .value attribute in case of PromptField"""
        val = self.pick(key)
        return val.value if isinstance(val, BasePromptField) else val

    def needs_calling(self, name) -> bool:
        """check if we can offload the work"""
        if name in self._cache or (name not in self._items):
            return False

        value = self[name]
        return isinstance(value, BasePromptField) or callable(value)

    def reset(self):
        """the results are cached and need to be reset between prompts"""
        self._cache.clear()

    def reset_key(self, key):
        """remove a single key from the cache (if it exists)"""
        self._cache.pop(key, None)


class BasePromptField:
    value = ""
    """This field should hold the bare value of the field without any color/format strings"""

    _name: "str|None" = None
    updator: "tp.Callable[[FieldType, PromptFields], None] | None" = None
    """this is a callable that needs to update the value or any of the attribute of the field"""

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

        Parameters
        ----------
        kwargs
            attributes of the class will be set from this
        """

        for attr, val in kwargs.items():
            setattr(self, attr, val)

    def update(self, ctx: PromptFields) -> None:
        """will be called from PromptFields getter for each new prompt"""
        if self.updator:
            self.updator(self, ctx)

    def __format__(self, format_spec: str):
        return format(self.value, format_spec)

    def __bool__(self):
        return bool(self.value)

    def __repr__(self):
        return f"<Prompt: {self._name}>"

    @classmethod
    def wrap(cls, **kwargs) -> "tp.Callable[..., FieldType]":
        """decorator to set the updator"""

        def wrapped(func):
            return cls(updator=func, **kwargs)

        return wrapped

    @property
    def name(self) -> str:
        """will be set during load.

        Notes
        -----
            fields with names such as ``gitstatus.branch`` mean they are defined in a module named ``gitstatus`` and
            are most likely a subfield used by ``gitstatus``
        """

        if self._name is None:
            raise NotImplementedError("PromptField name is not set")
        return self._name

    @name.setter
    def name(self, value: str) -> None:
        self._name = value


class PromptField(BasePromptField):
    """Any new non-private attributes set by the sub-classes are considered a way to configure the format"""

    # these three fields will get updated by the caller
    prefix = ""
    suffix = ""

    def __format__(self, format_spec: str):
        if self.value:
            return self.prefix + format(self.value, format_spec) + self.suffix
        return ""


class MultiPromptField(BasePromptField):
    """Facilitate combining other PromptFields"""

    separator = ""
    """in case this combines values from other prompt fields"""

    fragments: "tuple[str, ...]" = ()
    """name of the fields or the literals to combine.
    If the framgment name startswith ``.`` then they are resolved to include the name of this field."""

    def __init__(self, *fragments: "str", **kwargs):
        super().__init__(**kwargs)
        self.fragments = fragments or self.fragments

    def get_frags(self, env):
        yield from self.fragments

    def _collect(self, ctx):
        for frag in self.get_frags(ctx.xsh.env):
            if frag.startswith("."):
                field_name = f"{self.name}{frag}"
                if field_name in ctx:
                    frag = field_name

            if frag in ctx:
                yield format(ctx.pick(frag))
            elif isinstance(frag, str):
                yield frag

    def update(self, ctx: PromptFields):
        self.value = self.separator.join(self._collect(ctx))
