"""selector - WSGI delegation based on URL path and method.

(See the docstring of selector.Selector.)

Copyright (C) 2006 Luke Arno - http://lukearno.com/

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to 
the Free Software Foundation, Inc., 51 Franklin Street, 
Fifth Floor, Boston, MA  02110-1301  USA

Luke Arno can be found at http://lukearno.com/

"""

import re
from itertools import starmap
from wsgiref.util import shift_path_info


try:
    from resolver import resolve
except ImportError:
    # resolver not essential for basic featurs
    # FIXME: this library is overkill, simplify
    pass


class MappingFileError(Exception):
    pass


class PathExpressionParserError(Exception):
    pass


def method_not_allowed(environ, start_response):
    """Respond with a 405 and appropriate Allow header."""
    start_response(
        "405 Method Not Allowed",
        [
            ("Allow", ", ".join(environ["selector.methods"])),
            ("Content-Type", "text/plain"),
        ],
    )
    return [
        "405 Method Not Allowed\n\n"
        "The method specified in the Request-Line is not allowed "
        "for the resource identified by the Request-URI."
    ]


def not_found(environ, start_response):
    """Respond with a 404."""
    start_response("404 Not Found", [("Content-Type", "text/plain")])
    return [
        "404 Not Found\n\n"
        "The server has not found anything matching the Request-URI."
    ]


class Selector:
    """WSGI middleware for URL paths and HTTP method based delegation.

    See http://lukearno.com/projects/selector/

    Mappings are given are an iterable that returns tuples like this::

        (path_expression, http_methods_dict, optional_prefix)
    """

    status405 = staticmethod(method_not_allowed)
    status404 = staticmethod(not_found)

    def __init__(
        self,
        mappings=None,
        prefix="",
        parser=None,
        wrap=None,
        mapfile=None,
        consume_path=True,
    ):
        """Initialize selector."""
        self.mappings = []
        self.prefix = prefix
        if parser is None:
            self.parser = SimpleParser()
        else:
            self.parser = parser
        self.wrap = wrap
        if mapfile is not None:
            self.slurp_file(mapfile)
        if mappings is not None:
            self.slurp(mappings)
        self.consume_path = consume_path

    def slurp(self, mappings, prefix=None, parser=None, wrap=None):
        """Slurp in a whole list (or iterable) of mappings.

        Prefix and parser args will override self.parser and self.args
        for the given mappings.
        """
        if prefix is not None:
            oldprefix = self.prefix
            self.prefix = prefix
        if parser is not None:
            oldparser = self.parser
            self.parser = parser
        if wrap is not None:
            oldwrap = self.wrap
            self.wrap = wrap
        list(starmap(self.add, mappings))
        if wrap is not None:
            self.wrap = oldwrap
        if parser is not None:
            self.parser = oldparser
        if prefix is not None:
            self.prefix = oldprefix

    def add(self, path, method_dict=None, prefix=None, **http_methods):
        """Add a mapping.

        HTTP methods can be specified in a dict or using kwargs,
        but kwargs will override if both are given.

        Prefix will override self.prefix for this mapping.
        """
        # Thanks to Sébastien Pierre
        # for suggesting that this accept keyword args.
        if method_dict is None:
            method_dict = {}
        if prefix is None:
            prefix = self.prefix
        method_dict = dict(method_dict)
        method_dict.update(http_methods)
        if self.wrap is not None:
            for meth, cbl in method_dict.items():
                method_dict[meth] = self.wrap(cbl)
        regex = self.parser(self.prefix + path)
        compiled_regex = re.compile(regex, re.DOTALL | re.MULTILINE)
        self.mappings.append((compiled_regex, method_dict))

    def __call__(self, environ, start_response):
        """Delegate request to the appropriate WSGI app."""
        app, svars, methods, matched = self.select(
            environ["PATH_INFO"], environ["REQUEST_METHOD"]
        )
        unnamed, named = [], {}
        for k, v in svars.items():
            if k.startswith("__pos"):
                k = k[5:]
            named[k] = v
        environ["selector.vars"] = dict(named)
        for k in named.keys():
            if k.isdigit():
                unnamed.append((k, named.pop(k)))
        unnamed.sort()
        unnamed = [v for k, v in unnamed]
        cur_unnamed, cur_named = environ.get("wsgiorg.routing_args", ([], {}))
        unnamed = cur_unnamed + unnamed
        named.update(cur_named)
        environ["wsgiorg.routing_args"] = unnamed, named
        environ["selector.methods"] = methods
        environ.setdefault("selector.matches", []).append(matched)
        if self.consume_path:
            environ["SCRIPT_NAME"] = environ.get("SCRIPT_NAME", "") + matched
            environ["PATH_INFO"] = environ["PATH_INFO"][len(matched) :]
        return app(environ, start_response)

    def select(self, path, method):
        """Figure out which app to delegate to or send 404 or 405."""
        for regex, method_dict in self.mappings:
            match = regex.search(path)
            if match:
                methods = method_dict.keys()
                if method in method_dict:
                    return (
                        method_dict[method],
                        match.groupdict(),
                        methods,
                        match.group(0),
                    )
                elif "_ANY_" in method_dict:
                    return (
                        method_dict["_ANY_"],
                        match.groupdict(),
                        methods,
                        match.group(0),
                    )
                else:
                    return self.status405, {}, methods, ""
        return self.status404, {}, [], ""

    def slurp_file(self, the_file, prefix=None, parser=None, wrap=None):
        """Read mappings from a simple text file.

        Format looks like this::

            {{{

            # Comments if first non-whitespace char on line is '#'
            # Blank lines are ignored

            /foo/{id}[/]
                GET somemodule:some_wsgi_app
                POST pak.subpak.mod:other_wsgi_app

            @prefix /myapp
            /path[/]
                GET module:app
                POST package.module:get_app('foo')
                PUT package.module:FooApp('hello', resolve('module.setting'))

            @parser :lambda x: x
            @prefix
            ^/spam/eggs[/]$
                GET mod:regex_mapped_app

            }}}

        ``@prefix`` and ``@parser`` directives take effect
        until the end of the file or until changed.
        """
        if isinstance(the_file, str):
            the_file = open(the_file)
        oldprefix = self.prefix
        if prefix is not None:
            self.prefix = prefix
        oldparser = self.parser
        if parser is not None:
            self.parser = parser
        oldwrap = self.wrap
        if parser is not None:
            self.wrap = wrap
        path = methods = None
        lineno = 0
        try:
            # try:
            # accumulate methods (notice add in 2 places)
            for line in the_file:
                lineno += 1
                path, methods = self._parse_line(line, path, methods)
            if path and methods:
                self.add(path, methods)
        # except Exception, e:
        #    raise MappingFileError("Mapping line %s: %s" % (lineno, e))
        finally:
            the_file.close()
            self.wrap = oldwrap
            self.parser = oldparser
            self.prefix = oldprefix

    def _parse_line(self, line, path, methods):
        """Parse one line of a mapping file.

        This method is for the use of selector.slurp_file.
        """
        if not line.strip() or line.strip()[0] == "#":
            pass
        elif not line.strip() or line.strip()[0] == "@":
            #
            if path and methods:
                self.add(path, methods)
            path = line.strip()
            methods = {}
            #
            parts = line.strip()[1:].split(" ", 1)
            if len(parts) == 2:
                directive, rest = parts
            else:
                directive = parts[0]
                rest = ""
            if directive == "prefix":
                self.prefix = rest.strip()
            if directive == "parser":
                self.parser = resolve(rest.strip())
            if directive == "wrap":
                self.wrap = resolve(rest.strip())
        elif line and line[0] not in " \t":
            if path and methods:
                self.add(path, methods)
            path = line.strip()
            methods = {}
        else:
            meth, app = line.strip().split(" ", 1)
            methods[meth.strip()] = resolve(app)
        return path, methods


class SimpleParser:
    r"""Callable to turn path expressions into regexes with named groups.

    For instance ``"/hello/{name}"`` becomes ``r"^\/hello\/(?P<name>[^\^.]+)$"``

    For ``/hello/{name:pattern}``
    you get whatever is in ``self.patterns['pattern']`` instead of ``"[^\^.]+"``

    Optional portions of path expression can be expressed ``[like this]``

    ``/hello/{name}[/]`` (can have trailing slash or not)

    Example::

        /blog/archive/{year:digits}/{month:digits}[/[{article}[/]]]

    This would catch any of these::

        /blog/archive/2005/09
        /blog/archive/2005/09/
        /blog/archive/2005/09/1
        /blog/archive/2005/09/1/

    (I am not suggesting that this example is a best practice.
    I would probably have a separate mapping for listing the month
    and retrieving an individual entry. It depends, though.)
    """

    start, end = "{}"
    ostart, oend = "[]"
    _patterns = {
        "word": r"\w+",
        "alpha": r"[a-zA-Z]+",
        "digits": r"\d+",
        "number": r"\d*.?\d+",
        "chunk": r"[^/^.]+",
        "segment": r"[^/]+",
        "any": r".+",
    }
    default_pattern = "chunk"

    def __init__(self, patterns=None):
        """Initialize with character class mappings."""
        self.patterns = dict(self._patterns)
        if patterns is not None:
            self.patterns.update(patterns)

    def lookup(self, name):
        """Return the replacement for the name found."""
        if ":" in name:
            name, pattern = name.split(":")
            pattern = self.patterns[pattern]
        else:
            pattern = self.patterns[self.default_pattern]
        if name == "":
            name = "__pos%s" % self._pos
            self._pos += 1
        return f"(?P<{name}>{pattern})"

    def lastly(self, regex):
        """Process the result of __call__ right before it returns.

        Adds the ^ and the $ to the beginning and the end, respectively.
        """
        return "^%s$" % regex

    def openended(self, regex):
        """Process the result of ``__call__`` right before it returns.

        Adds the ^ to the beginning but no $ to the end.
        Called as a special alternative to lastly.
        """
        return "^%s" % regex

    def outermost_optionals_split(self, text):
        """Split out optional portions by outermost matching delims."""
        parts = []
        buffer = ""
        starts = ends = 0
        for c in text:
            if c == self.ostart:
                if starts == 0:
                    parts.append(buffer)
                    buffer = ""
                else:
                    buffer += c
                starts += 1
            elif c == self.oend:
                ends += 1
                if starts == ends:
                    parts.append(buffer)
                    buffer = ""
                    starts = ends = 0
                else:
                    buffer += c
            else:
                buffer += c
        if not starts == ends == 0:
            raise PathExpressionParserError("Mismatch of optional portion delimiters.")
        parts.append(buffer)
        return parts

    def parse(self, text):
        """Turn a path expression into regex."""
        if self.ostart in text:
            parts = self.outermost_optionals_split(text)
            parts = map(self.parse, parts)
            parts[1::2] = ["(%s)?" % p for p in parts[1::2]]
        else:
            parts = [part.split(self.end) for part in text.split(self.start)]
            parts = [y for x in parts for y in x]
            parts[::2] = map(re.escape, parts[::2])
            parts[1::2] = map(self.lookup, parts[1::2])
        return "".join(parts)

    def __call__(self, url_pattern):
        """Turn a path expression into regex via parse and lastly."""
        self._pos = 0
        if url_pattern.endswith("|"):
            return self.openended(self.parse(url_pattern[:-1]))
        else:
            return self.lastly(self.parse(url_pattern))


class EnvironDispatcher:
    """Dispatch based on list of rules."""

    def __init__(self, rules):
        """Instantiate with a list of (predicate, wsgiapp) rules."""
        self.rules = rules

    def __call__(self, environ, start_response):
        """Call the first app whose predicate is true.

        Each predicate is passes the environ to evaluate.
        """
        for predicate, app in self.rules:
            if predicate(environ):
                return app(environ, start_response)


class MiddlewareComposer:
    """Compose middleware based on list of rules."""

    def __init__(self, app, rules):
        """Instantiate with an app and a list of rules."""
        self.app = app
        self.rules = rules

    def __call__(self, environ, start_response):
        """Apply each middleware whose predicate is true.

        Each predicate is passes the environ to evaluate.

        Given this set of rules::

            t = lambda x: True; f = lambda x: False
            [(t, a), (f, b), (t, c), (f, d), (t, e)]

        The app composed would be equivalent to this::

            a(c(e(app)))

        """
        app = self.app
        for predicate, middleware in reversed(self.rules):
            if predicate(environ):
                app = middleware(app)
        return app(environ, start_response)


def expose(obj):
    """Set obj._exposed = True and return obj."""
    obj._exposed = True
    return obj


class Naked:
    """Naked object style dispatch base class."""

    _not_found = staticmethod(not_found)
    _expose_all = True
    _exposed = True

    def _is_exposed(self, obj):
        """Determine if obj should be exposed.

        If ``self._expose_all`` is True, always return True.
        Otherwise, look at obj._exposed.
        """
        return self._expose_all or getattr(obj, "_exposed", False)

    def __call__(self, environ, start_response):
        """Dispatch to the method named by the next bit of PATH_INFO."""
        name = shift_path_info(
            dict(SCRIPT_NAME=environ["SCRIPT_NAME"], PATH_INFO=environ["PATH_INFO"])
        )
        callable = getattr(self, name or "index", None)
        if callable is not None and self._is_exposed(callable):
            shift_path_info(environ)
            return callable(environ, start_response)
        else:
            return self._not_found(environ, start_response)


class ByMethod:
    """Base class for dispatching to method named by ``REQUEST_METHOD``."""

    _method_not_allowed = staticmethod(method_not_allowed)

    def __call__(self, environ, start_response):
        """Dispatch based on REQUEST_METHOD."""
        environ["selector.methods"] = [m for m in dir(self) if not m.startswith("_")]
        return getattr(self, environ["REQUEST_METHOD"], self._method_not_allowed)(
            environ, start_response
        )


def pliant(func):
    """Decorate an unbound wsgi callable taking args from
    ``wsgiorg.routing_args``
    ::

        @pliant
        def app(environ, start_response, arg1, arg2, foo='bar'):
            ...
    """

    def wsgi_func(environ, start_response):
        args, kwargs = environ.get("wsgiorg.routing_args", ([], {}))
        args = list(args)
        args.insert(0, start_response)
        args.insert(0, environ)
        return func(*args, **dict(kwargs))

    return wsgi_func


def opliant(meth):
    """Decorate a bound wsgi callable taking args from
    ``wsgiorg.routing_args``
    ::

        class App:
            @opliant
            def __call__(self, environ, start_response, arg1, arg2, foo='bar'):
                ...
    """

    def wsgi_meth(self, environ, start_response):
        args, kwargs = environ.get("wsgiorg.routing_args", ([], {}))
        args = list(args)
        args.insert(0, start_response)
        args.insert(0, environ)
        args.insert(0, self)
        return meth(*args, **dict(kwargs))

    return wsgi_meth
