"""
Inline functions (nested form).

This parser accepts nested inlinefunctions on the form

```
$funcname(arg, arg, ...)
```

embedded in any text where any arg can be another $funcname{} call.
This functionality is turned off by default - to activate,
`settings.INLINEFUNC_ENABLED` must be set to `True`.

Each token starts with "$funcname(" where there must be no space
between the $funcname and (. It ends with a matched ending parentesis.
")".

Inside the inlinefunc definition, one can use `\` to escape. This is
mainly needed for escaping commas in flowing text (which would
otherwise be interpreted as an argument separator), or to escape `}`
when not intended to close the function block. Enclosing text in
matched `\"\"\"` (triple quotes) or `'''` (triple single-quotes) will
also escape *everything* within without needing to escape individual
characters.

The available inlinefuncs are defined as global-level functions in
modules defined by `settings.INLINEFUNC_MODULES`. They are identified
by their function name (and ignored if this name starts with `_`). They
should be on the following form:

```python
def funcname (*args, **kwargs):
    # ...
```

Here, the arguments given to `$funcname(arg1,arg2)` will appear as the
`*args` tuple. This will be populated by the arguments given to the
inlinefunc in-game - the only part that will be available from
in-game. `**kwargs` are not supported from in-game but are only used
internally by Evennia to make details about the caller available to
the function. The kwarg passed to all functions is `session`, the
Sessionobject for the object seeing the string. This may be `None` if
the string is sent to a non-puppetable object. The inlinefunc should
never raise an exception.

There are two reserved function names:
- "nomatch": This is called if the user uses a functionname that is
    not registered. The nomatch function will get the name of the
    not-found function as its first argument followed by the normal
    arguments to the given function. If not defined the default effect is
    to print `<UNKNOWN>` to replace the unknown function.
- "stackfull": This is called when the maximum nested function stack is reached.
  When this happens, the original parsed string is returned and the result of
  the `stackfull` inlinefunc is appended to the end. By default this is an
  error message.

Error handling:
   Syntax errors, notably not completely closing all inlinefunc
   blocks, will lead to the entire string remaining unparsed.

"""

import re
import fnmatch
from django.conf import settings

from evennia.utils import utils, logger


# example/testing inline functions

def pad(*args, **kwargs):
    """
    Inlinefunc. Pads text to given width.

    Args:
        text (str, optional): Text to pad.
        width (str, optional): Will be converted to integer. Width
            of padding.
        align (str, optional): Alignment of padding; one of 'c', 'l' or 'r'.
        fillchar (str, optional): Character used for padding. Defaults to a space.

    Kwargs:
        session (Session): Session performing the pad.

    Example:
        `$pad(text, width, align, fillchar)`

    """
    text, width, align, fillchar = "", 78, 'c', ' '
    nargs = len(args)
    if nargs > 0:
        text = args[0]
    if nargs > 1:
        width = int(args[1]) if args[1].strip().isdigit() else 78
    if nargs > 2:
        align = args[2] if args[2] in ('c', 'l', 'r') else 'c'
    if nargs > 3:
        fillchar = args[3]
    return utils.pad(text, width=width, align=align, fillchar=fillchar)


def crop(*args, **kwargs):
    """
    Inlinefunc. Crops ingoing text to given widths.

    Args:
        text (str, optional): Text to crop.
        width (str, optional): Will be converted to an integer. Width of
            crop in characters.
        suffix (str, optional): End string to mark the fact that a part
            of the string was cropped. Defaults to `[...]`.
    Kwargs:
        session (Session): Session performing the crop.

    Example:
        `$crop(text, width=78, suffix='[...]')`

    """
    text, width, suffix = "", 78, "[...]"
    nargs = len(args)
    if nargs > 0:
        text = args[0]
    if nargs > 1:
        width = int(args[1]) if args[1].strip().isdigit() else 78
    if nargs > 2:
        suffix = args[2]
    return utils.crop(text, width=width, suffix=suffix)


def clr(*args, **kwargs):
    """
    Inlinefunc. Colorizes nested text.

    Args:
        startclr (str, optional): An ANSI color abbreviation without the
            prefix `|`, such as `r` (red foreground) or `[r` (red background).
        text (str, optional): Text
        endclr (str, optional): The color to use at the end of the string. Defaults
            to `|n` (reset-color).
    Kwargs:
        session (Session): Session object triggering inlinefunc.

    Example:
        `$clr(startclr, text, endclr)`

    """
    text = ""
    nargs = len(args)
    if nargs > 0:
        color = args[0].strip()
    if nargs > 1:
        text = args[1]
        text = "|" + color + text
    if nargs > 2:
        text += "|" + args[2].strip()
    else:
        text += "|n"
    return text


def null(*args, **kwargs):
    return args[0] if args else ''


def nomatch(name, *args, **kwargs):
    """
    Default implementation of nomatch returns the function as-is as a string.

    """
    kwargs.pop("inlinefunc_stack_depth", None)
    kwargs.pop("session")

    return "${name}({args}{kwargs})".format(
        name=name,
        args=",".join(args),
        kwargs=",".join("{}={}".format(key, val) for key, val in kwargs.items()))

_INLINE_FUNCS = {}

# we specify a default nomatch function to use if no matching func was
# found. This will be overloaded by any nomatch function defined in
# the imported modules.
_DEFAULT_FUNCS = {"nomatch": lambda *args, **kwargs: "<UNKNOWN>",
                  "stackfull": lambda *args, **kwargs: "\n (not parsed: "}

_INLINE_FUNCS.update(_DEFAULT_FUNCS)

# load custom inline func modules.
for module in utils.make_iter(settings.INLINEFUNC_MODULES):
    try:
        _INLINE_FUNCS.update(utils.callables_from_module(module))
    except ImportError as err:
        if module == "server.conf.inlinefuncs":
            # a temporary warning since the default module changed name
            raise ImportError("Error: %s\nPossible reason: mygame/server/conf/inlinefunc.py should "
                              "be renamed to mygame/server/conf/inlinefuncs.py (note "
                              "the S at the end)." % err)
        else:
            raise


# The stack size is a security measure. Set to <=0 to disable.
try:
    _STACK_MAXSIZE = settings.INLINEFUNC_STACK_MAXSIZE
except AttributeError:
    _STACK_MAXSIZE = 20

# regex definitions

_RE_STARTTOKEN = re.compile(r"(?<!\\)\$(\w+)\(")  # unescaped $funcname( (start of function call)

# note: this regex can be experimented with at https://regex101.com/r/kGR3vE/2
_RE_TOKEN = re.compile(r"""
      (?<!\\)\'\'\'(?P<singlequote>.*?)(?<!\\)\'\'\'|  # single-triplets escape all inside
      (?<!\\)\"\"\"(?P<doublequote>.*?)(?<!\\)\"\"\"|  # double-triplets escape all inside
      (?P<comma>(?<!\\)\,)|                            # , (argument sep)
      (?P<end>(?<!\\)\))|                              # ) (possible end of func call)
      (?P<leftparens>(?<!\\)\()|                       # ( (lone left-parens)
      (?P<start>(?<!\\)\$\w+\()|                       # $funcname (start of func call)
      (?P<escaped>                                     # escaped tokens to re-insert sans backslash
            \\\'|\\\"|\\\)|\\\$\w+\(|\\\()|
      (?P<rest>                                        # everything else to re-insert verbatim
            \$(?!\w+\()|\'|\"|\\|[^),$\'\"\\\(]+)""",
                       re.UNICODE | re.IGNORECASE | re.VERBOSE | re.DOTALL)

# Cache for function lookups.
_PARSING_CACHE = utils.LimitedSizeOrderedDict(size_limit=1000)


class ParseStack(list):
    """
    Custom stack that always concatenates strings together when the
    strings are added next to one another. Tuples are stored
    separately and None is used to mark that a string should be broken
    up into a new chunk. Below is the resulting stack after separately
    appending 3 strings, None, 2 strings, a tuple and finally 2
    strings:

    [string + string + string,
    None
    string + string,
    tuple,
    string + string]

    """

    def __init__(self, *args, **kwargs):
        super(ParseStack, self).__init__(*args, **kwargs)
        # always start stack with the empty string
        list.append(self, "")
        # indicates if the top of the stack is a string or not
        self._string_last = True

    def __eq__(self, other):
        return (super(ParseStack).__eq__(other) and
                hasattr(other, "_string_last") and self._string_last == other._string_last)

    def __ne__(self, other):
        return not self.__eq__(other)

    def append(self, item):
        """
        The stack will merge strings, add other things as normal
        """
        if isinstance(item, basestring):
            if self._string_last:
                self[-1] += item
            else:
                list.append(self, item)
                self._string_last = True
        else:
            # everything else is added as normal
            list.append(self, item)
            self._string_last = False


class InlinefuncError(RuntimeError):
    pass


def parse_inlinefunc(string, strip=False, available_funcs=None, stacktrace=False, **kwargs):
    """
    Parse the incoming string.

    Args:
        string (str): The incoming string to parse.
        strip (bool, optional): Whether to strip function calls rather than
            execute them.
        available_funcs (dict, optional): Define an alternative source of functions to parse for.
            If unset, use the functions found through `settings.INLINEFUNC_MODULES`.
        stacktrace (bool, optional): If set, print the stacktrace to log.
    Kwargs:
        session (Session): This is sent to this function by Evennia when triggering
            it. It is passed to the inlinefunc.
        kwargs (any): All other kwargs are also passed on to the inlinefunc.


    """
    global _PARSING_CACHE
    usecache = False
    if not available_funcs:
        available_funcs = _INLINE_FUNCS
        usecache = True
    else:
        # make sure the default keys are available, but also allow overriding
        tmp = _DEFAULT_FUNCS.copy()
        tmp.update(available_funcs)
        available_funcs = tmp

    if usecache and string in _PARSING_CACHE:
        # stack is already cached
        stack = _PARSING_CACHE[string]
    elif not _RE_STARTTOKEN.search(string):
        # if there are no unescaped start tokens at all, return immediately.
        return string
    else:
        # no cached stack; build a new stack and continue
        stack = ParseStack()

        # process string on stack
        ncallable = 0
        nlparens = 0
        nvalid = 0

        if stacktrace:
            out = "STRING: {} =>".format(string)
            print(out)
            logger.log_info(out)

        for match in _RE_TOKEN.finditer(string):
            gdict = match.groupdict()

            if stacktrace:
                out = " MATCH: {}".format({key: val for key, val in gdict.items() if val})
                print(out)
                logger.log_info(out)

            if gdict["singlequote"]:
                stack.append(gdict["singlequote"])
            elif gdict["doublequote"]:
                stack.append(gdict["doublequote"])
            elif gdict["leftparens"]:
                # we have a left-parens inside a callable
                if ncallable:
                    nlparens += 1
                stack.append("(")
            elif gdict["end"]:
                if nlparens > 0:
                    nlparens -= 1
                    stack.append(")")
                    continue
                if ncallable <= 0:
                    stack.append(")")
                    continue
                args = []
                while stack:
                    operation = stack.pop()
                    if callable(operation):
                        if not strip:
                            stack.append((operation, [arg for arg in reversed(args)]))
                        ncallable -= 1
                        break
                    else:
                        args.append(operation)
            elif gdict["start"]:
                funcname = _RE_STARTTOKEN.match(gdict["start"]).group(1)
                try:
                    # try to fetch the matching inlinefunc from storage
                    stack.append(available_funcs[funcname])
                    nvalid += 1
                except KeyError:
                    stack.append(available_funcs["nomatch"])
                    stack.append(funcname)
                    stack.append(None)
                ncallable += 1
            elif gdict["escaped"]:
                # escaped tokens
                token = gdict["escaped"].lstrip("\\")
                stack.append(token)
            elif gdict["comma"]:
                if ncallable > 0:
                    # commas outside strings and inside a callable are
                    # used to mark argument separation - we use None
                    # in the stack to indicate such a separation.
                    stack.append(None)
                else:
                    # no callable active - just a string
                    stack.append(",")
            else:
                # the rest
                stack.append(gdict["rest"])

        if ncallable > 0:
            # this means not all inlinefuncs were complete
            return string

        if _STACK_MAXSIZE > 0 and _STACK_MAXSIZE < nvalid:
            # if stack is larger than limit, throw away parsing
            return string + available_funcs["stackfull"](*args, **kwargs)
        elif usecache:
            # cache the stack - we do this also if we don't check the cache above
            _PARSING_CACHE[string] = stack

    # run the stack recursively
    def _run_stack(item, depth=0):
        retval = item
        if isinstance(item, tuple):
            if strip:
                return ""
            else:
                func, arglist = item
                args = [""]
                for arg in arglist:
                    if arg is None:
                        # an argument-separating comma - start a new arg
                        args.append("")
                    else:
                        # all other args should merge into one string
                        args[-1] += _run_stack(arg, depth=depth + 1)
                # execute the inlinefunc at this point or strip it.
                kwargs["inlinefunc_stack_depth"] = depth
                retval = "" if strip else func(*args, **kwargs)
        return utils.to_str(retval, force_string=True)
    retval = "".join(_run_stack(item) for item in stack)
    if stacktrace:
        out = "STACK: \n{} => {}\n".format(stack, retval)
        print(out)
        logger.log_info(out)

    # execute the stack
    return retval

#
# Nick templating
#


"""
This supports the use of replacement templates in nicks:

This happens in two steps:

1) The user supplies a template that is converted to a regex according
   to the unix-like templating language.
2) This regex is tested against nicks depending on which nick replacement
   strategy is considered (most commonly inputline).
3) If there is a template match and there are templating markers,
   these are replaced with the arguments actually given.

@desc $1 $2 $3

This will be converted to the following regex:

\@desc (?P<1>\w+) (?P<2>\w+) $(?P<3>\w+)

Supported template markers (through fnmatch)
   *       matches anything (non-greedy)     -> .*?
   ?       matches any single character      ->
   [seq]   matches any entry in sequence
   [!seq]  matches entries not in sequence
Custom arg markers
   $N      argument position (1-99)

"""

_RE_NICK_ARG = re.compile(r"\\(\$)([1-9][0-9]?)")
_RE_NICK_TEMPLATE_ARG = re.compile(r"(\$)([1-9][0-9]?)")
_RE_NICK_SPACE = re.compile(r"\\ ")


class NickTemplateInvalid(ValueError):
    pass


def initialize_nick_templates(in_template, out_template):
    """
    Initialize the nick templates for matching and remapping a string.

    Args:
        in_template (str): The template to be used for nick recognition.
        out_template (str): The template to be used to replace the string
            matched by the in_template.

    Returns:
        regex  (regex): Regex to match against strings
        template (str): Template with markers {arg1}, {arg2}, etc for
            replacement using the standard .format method.

    Raises:
        NickTemplateInvalid: If the in/out template does not have a matching
            number of $args.

    """
    # create the regex for in_template
    regex_string = fnmatch.translate(in_template)
    n_inargs = len(_RE_NICK_ARG.findall(regex_string))
    regex_string = _RE_NICK_SPACE.sub("\s+", regex_string)
    regex_string = _RE_NICK_ARG.sub(lambda m: "(?P<arg%s>.+?)" % m.group(2), regex_string)

    # create the out_template
    template_string = _RE_NICK_TEMPLATE_ARG.sub(lambda m: "{arg%s}" % m.group(2), out_template)

    # validate the tempaltes - they should at least have the same number of args
    n_outargs = len(_RE_NICK_TEMPLATE_ARG.findall(out_template))
    if n_inargs != n_outargs:
        raise NickTemplateInvalid

    return re.compile(regex_string), template_string


def parse_nick_template(string, template_regex, outtemplate):
    """
    Parse a text using a template and map it to another template

    Args:
        string (str): The input string to processj
        template_regex (regex): A template regex created with
            initialize_nick_template.
        outtemplate (str): The template to which to map the matches
            produced by the template_regex. This should have $1, $2,
            etc to match the regex.

    """
    match = template_regex.match(string)
    if match:
        return outtemplate.format(**match.groupdict())
    return string
