''' Stack Command implementation. '''
import inspect
import sys, os
from typing import Dict
from bluesky.stack.argparser import Parameter, getnextarg, ArgumentError


class Command:
    ''' Stack command object. '''

    # Dictionary with all command objects
    cmddict: Dict[str, 'Command'] = dict()

    @classmethod
    def addcommand(cls, func, parent=None, name='', **kwargs):
        ''' Add 'func' as a stack command. '''
        # Get function object if it's decorated as static or classmethod
        func = func.__func__ if isinstance(func, (staticmethod, classmethod)) \
            else func
        # Stack command name
        name = (name or func.__name__).upper()

        # When a parent is passed this function is a subcommand
        target = parent.subcmds if isinstance(
            parent, CommandGroup) else Command.cmddict

        # Check if this command already exists
        cmdobj = target.get(name)
        if not cmdobj:
            cmdobj = cls(func, parent, name, **kwargs)
            target[name] = cmdobj
            for alias in cmdobj.aliases:
                target[alias] = cmdobj
        else:
            # for subclasses reimplementing stack functions we keep only one
            # Command object
            print(f'Attempt to reimplement {name} from {cmdobj.callback} to {func}')
            if not isinstance(cmdobj, cls):
                raise TypeError(f'Error reimplementing {name}: '
                                f'A {type(cmdobj).__name__} cannot be '
                                f'reimplemented as a {cls.__name__}')
        # Store reference to command object for function
        if not inspect.ismethod(func):
            func.__stack_cmd__ = cmdobj

    def __init__(self, func, parent=None, name='', **kwargs):
        self.name = name
        self.help = inspect.cleandoc(kwargs.get('help', ''))
        self.brief = kwargs.get('brief', '')
        self.aliases = kwargs.get('aliases', tuple())
        self.impl = ''
        self.valid = True
        self.annotations = get_annot(kwargs.get('annotations', ''))
        self.params = list()
        self.parent = parent
        self.callback = func

    def __call__(self, argstring):
        args = []
        param = None
        # Use callback-specified parameter parsers to generate param list from strings
        for param in self.params:
            result = param(argstring)
            argstring = result[-1]
            args.extend(result[:-1])

        # Parse repeating final args
        while argstring:
            if param is None or not param.gobble:
                msg = f'{self.name} takes {len(self.params)} argument'
                if len(self.params) > 1:
                    msg += 's'
                count = len(self.params)
                while argstring:
                    _, argstring = getnextarg(argstring)
                    count += 1
                msg += f', but {count} were given'
                raise ArgumentError(msg)
            result = param(argstring)
            argstring = result[-1]
            args.extend(result[:-1])

        # Call callback function with parsed parameters
        ret = self.callback(*args)
        # Always return a tuple with a success value and a message string
        if ret is None:
            return True, ''
        if isinstance(ret, (tuple, list)) and ret:
            if len(ret) > 1:
                # Assume that (success, echotext) is returned
                return ret[:2]
            ret = ret[0]
        return ret, ''

    def __repr__(self):
        if self.valid:
            return f'<Stack Command {self.name}, callback={self.callback}>'
        return f'<Stack Command {self.name} (invalid), callback=unbound method {self.callback}'

    def notimplemented(self, *args, **kwargs):
        ''' Stub for stack functions based on Entity methods, when a currently
            selected Entity implementation doesn't provide the stack function of
            this command.
        '''
        impl = self.impl or inspect.getmodule(self.callback).__name__
        return False, f'The current {self.name} implementation doesn\'t' +\
            f'provide this function (function was originally declared in {impl})'

    @property
    def callback(self):
        ''' Callback pointing to the actual function that implements this
            stack command.
        '''
        return self._callback

    @callback.setter
    def callback(self, function):
        self._callback = function
        spec = inspect.signature(function)
        # Check if this is an unbound class/instance method
        self.valid = spec.parameters.get('self') is None and \
            spec.parameters.get('cls') is None

        if self.valid:
            # Store implementation origin
            if not self.impl:
                # Check if this is a bound (class or object) method
                if inspect.ismethod(function):
                    if inspect.isclass(function.__self__):
                        self.impl = function.__self__.__name__
                    else:
                        self.impl = function.__self__.__class__.__name__

            self.brief = self.brief or (
                self.name + ' ' + ','.join(spec.parameters))
            self.help = self.help or inspect.cleandoc(
                inspect.getdoc(function) or '')
            paramspecs = list(filter(Parameter.canwrap, spec.parameters.values()))
            if self.annotations:
                self.params = list()
                pos = 0
                for annot, isopt in self.annotations:
                    if annot == '...':
                        if paramspecs[-1].kind != paramspecs[-1].VAR_POSITIONAL:
                            raise IndexError('Repeating arguments (...) given for function'
                                             ' not ending in starred (variable-length) argument')
                        self.params[-1].gobble = True
                        break

                    param = Parameter(paramspecs[pos], annot, isopt)
                    if param:
                        pos = min(pos + param.size(), len(paramspecs) - 1)
                        self.params.append(param)
                if len(self.params) > len(paramspecs) and \
                    paramspecs[-1].kind != paramspecs[-1].VAR_POSITIONAL:
                    raise IndexError(f'More annotations given than function '
                                     f'{self.callback.__name__} has arguments.')
            else:
                self.params = [p for p in map(Parameter, paramspecs) if p]

    def helptext(self, subcmd=''):
        ''' Return complete help text. '''
        msg = f'<div style="white-space: pre;">{self.help}</div>\nUsage:\n{self.brief}'
        if self.aliases:
            msg += ('\nCommand aliases: ' + ','.join(self.aliases))
        if self._callback.__name__ == '<lambda>':
            msg += '\nAnonymous (lambda) function, implemented in '
        else:
            msg += f'\nFunction {self._callback.__name__}(), implemented in '
        if hasattr(self._callback, '__code__'):
            fname = self._callback.__code__.co_filename
            fname_stripped = fname.replace(os.getcwd(), '').lstrip('/')
            firstline = self._callback.__code__.co_firstlineno
            msg += f'<a href="file://{fname}">{fname_stripped} on line {firstline}</a>'
        else:
            msg += f'module {self._callback.__module__}'

        return msg

    def brieftext(self):
        ''' Return the brief usage text. '''
        return self.brief


class CommandGroup(Command):
    ''' Stack command group object.
        Command groups can have subcommands.
    '''
    def __init__(self, func, parent=None, name='', **kwargs):
        super().__init__(func, parent, name, **kwargs)
        self.subcmds = dict()

        # Give the function a method to add subcommands
        func.subcommand = lambda fun=None, **kwargs: command(
            fun, parent=self, **kwargs)

    def __call__(self, strargs):
        # First check subcommand
        if strargs:
            subcmd, subargs = getnextarg(strargs)
            subcmdobj = self.subcmds.get(subcmd.upper())
            if subcmdobj:
                return subcmdobj(subargs)
        return super().__call__(strargs)

    def helptext(self, subcmd=''):
        ''' Return complete help text. '''
        if subcmd:
            obj = self.subcmds.get(subcmd)
            return obj.helptext() if obj else f'{subcmd} is not a subcommand of {self.name}'

        msg = f'{self.help}\nUsage:\n{self.brief}'
        for subcmd in self.subcmds.values():
            msg += f'\n{self.name} {subcmd.brief}'
        if self.aliases:
            msg += ('\nCommand aliases: ' + ','.join(self.aliases))
        return msg

    def brieftext(self):
        ''' Return the brief usage text. '''
        msg = self.brief
        for subcmd in self.subcmds.values():
            msg += f'\n{self.name} {subcmd.brief}'
        return msg

def commandgroup(fun=None, parent=None, **kwargs):
    ''' BlueSky stack command decorator for command groups.

        Functions decorated with this decorator become available as stack
        functions, and have the ability to have subcommands.
    '''
    return command(fun, CommandGroup, parent, **kwargs)


def command(fun=None, cls=Command, parent=None, **kwargs):
    ''' BlueSky stack command decorator.

        Functions decorated with this decorator become available as stack
        functions.
    '''
    def deco(fun):
        # Construct the stack command object, but return the original function
        cls.addcommand(fun, parent, **kwargs)
        return fun
    # Allow both @command and @command(args)
    return deco if fun is None else deco(fun)


def append_commands(newcommands, syndict=None):
    """ Append additional functions to the stack command dictionary """
    for name, (brief, annotations, fun, hlp) in newcommands.items():
        if syndict:
            aliases = tuple(k for k,v in syndict.items() if v == name)
        else:
            aliases = tuple()
        # Use the command decorator function to register each new command
        command(fun, name=name, annotations=annotations, brief=brief, help=hlp, aliases=aliases)


def remove_commands(commands):
    """ Remove functions from the stack """
    for cmd in commands:
        Command.cmddict.pop(cmd)


def get_commands():
    """ Return the stack dictionary of commands. """
    return Command.cmddict


def get_annot(annotations):
    ''' Get annotations from string, or tuple/list. '''
    if isinstance(annotations, (tuple, list)):
        return tuple(annotations)
    # Assume it is a comma-separated string
    argtypes = []

    # Process and reduce annotation string from left to right
    # First cut at square brackets, then take separate argument types
    while annotations:
        opt = annotations[0] == "["
        cut = (annotations.find("]") if opt else annotations.find(
            "[") if "[" in annotations else len(annotations))

        types = annotations[:cut].strip("[,]").split(",")
        # Returned argtypes are tuples of type and optional status
        argtypes += zip(types, [opt or t == "..." for t in types])
        annotations = annotations[cut:].lstrip(",]")

    return tuple(argtypes)
