# Copyright (c) 2003-2013 LOGILAB S.A. (Paris, FRANCE).
# http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation; either version 2 of the License, or (at your option) any later
# version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
"""imports checkers for Python code"""

import sys
from collections import defaultdict

import six
from six.moves import map # pylint: disable=redefined-builtin

from logilab.common.graph import get_cycles, DotBackend
from logilab.common.ureports import VerbatimText, Paragraph

import astroid
from astroid import are_exclusive
from astroid.modutils import get_module_part, is_standard_module

from pylint.interfaces import IAstroidChecker
from pylint.utils import EmptyReport
from pylint.checkers import BaseChecker
from pylint.checkers.utils import check_messages, is_import_error

def _except_import_error(node):
    """
    Check if the try-except node has an ImportError handler.
    Return True if an ImportError handler was infered, False otherwise.
    """
    if not isinstance(node, astroid.TryExcept):
        return
    return any(map(is_import_error, node.handlers))

def get_first_import(node, context, name, base, level):
    """return the node where [base.]<name> is imported or None if not found
    """
    fullname = '%s.%s' % (base, name) if base else name

    first = None
    found = False
    for first in context.body:
        if first is node:
            continue
        if first.scope() is node.scope() and first.fromlineno > node.fromlineno:
            continue
        if isinstance(first, astroid.Import):
            if any(fullname == iname[0] for iname in first.names):
                found = True
                break
        elif isinstance(first, astroid.From):
            if level == first.level and any(
                    fullname == '%s.%s' % (first.modname, iname[0])
                    for iname in first.names):
                found = True
                break
    if found and not are_exclusive(first, node):
        return first

# utilities to represents import dependencies as tree and dot graph ###########

def make_tree_defs(mod_files_list):
    """get a list of 2-uple (module, list_of_files_which_import_this_module),
    it will return a dictionary to represent this as a tree
    """
    tree_defs = {}
    for mod, files in mod_files_list:
        node = (tree_defs, ())
        for prefix in mod.split('.'):
            node = node[0].setdefault(prefix, [{}, []])
        node[1] += files
    return tree_defs

def repr_tree_defs(data, indent_str=None):
    """return a string which represents imports as a tree"""
    lines = []
    nodes = data.items()
    for i, (mod, (sub, files)) in enumerate(sorted(nodes, key=lambda x: x[0])):
        if not files:
            files = ''
        else:
            files = '(%s)' % ','.join(files)
        if indent_str is None:
            lines.append('%s %s' % (mod, files))
            sub_indent_str = '  '
        else:
            lines.append(r'%s\-%s %s' % (indent_str, mod, files))
            if i == len(nodes)-1:
                sub_indent_str = '%s  ' % indent_str
            else:
                sub_indent_str = '%s| ' % indent_str
        if sub:
            lines.append(repr_tree_defs(sub, sub_indent_str))
    return '\n'.join(lines)


def dependencies_graph(filename, dep_info):
    """write dependencies as a dot (graphviz) file
    """
    done = {}
    printer = DotBackend(filename[:-4], rankdir='LR')
    printer.emit('URL="." node[shape="box"]')
    for modname, dependencies in sorted(six.iteritems(dep_info)):
        done[modname] = 1
        printer.emit_node(modname)
        for modname in dependencies:
            if modname not in done:
                done[modname] = 1
                printer.emit_node(modname)
    for depmodname, dependencies in sorted(six.iteritems(dep_info)):
        for modname in dependencies:
            printer.emit_edge(modname, depmodname)
    printer.generate(filename)


def make_graph(filename, dep_info, sect, gtype):
    """generate a dependencies graph and add some information about it in the
    report's section
    """
    dependencies_graph(filename, dep_info)
    sect.append(Paragraph('%simports graph has been written to %s'
                          % (gtype, filename)))


# the import checker itself ###################################################

MSGS = {
    'F0401': ('Unable to import %s',
              'import-error',
              'Used when pylint has been unable to import a module.'),
    'R0401': ('Cyclic import (%s)',
              'cyclic-import',
              'Used when a cyclic import between two or more modules is \
              detected.'),

    'W0401': ('Wildcard import %s',
              'wildcard-import',
              'Used when `from module import *` is detected.'),
    'W0402': ('Uses of a deprecated module %r',
              'deprecated-module',
              'Used a module marked as deprecated is imported.'),
    'W0403': ('Relative import %r, should be %r',
              'relative-import',
              'Used when an import relative to the package directory is '
              'detected.',
              {'maxversion': (3, 0)}),
    'W0404': ('Reimport %r (imported line %s)',
              'reimported',
              'Used when a module is reimported multiple times.'),
    'W0406': ('Module import itself',
              'import-self',
              'Used when a module is importing itself.'),

    'W0410': ('__future__ import is not the first non docstring statement',
              'misplaced-future',
              'Python 2.5 and greater require __future__ import to be the \
              first non docstring statement in the module.',
              {'maxversion': (3, 0)}),
    }

class ImportsChecker(BaseChecker):
    """checks for
    * external modules dependencies
    * relative / wildcard imports
    * cyclic imports
    * uses of deprecated modules
    """

    __implements__ = IAstroidChecker

    name = 'imports'
    msgs = MSGS
    priority = -2

    if sys.version_info < (3,):
        deprecated_modules = ('regsub', 'TERMIOS', 'Bastion', 'rexec')
    else:
        deprecated_modules = ('stringprep', 'optparse')
    options = (('deprecated-modules',
                {'default' : deprecated_modules,
                 'type' : 'csv',
                 'metavar' : '<modules>',
                 'help' : 'Deprecated modules which should not be used, \
separated by a comma'}
               ),
               ('import-graph',
                {'default' : '',
                 'type' : 'string',
                 'metavar' : '<file.dot>',
                 'help' : 'Create a graph of every (i.e. internal and \
external) dependencies in the given file (report RP0402 must not be disabled)'}
               ),
               ('ext-import-graph',
                {'default' : '',
                 'type' : 'string',
                 'metavar' : '<file.dot>',
                 'help' : 'Create a graph of external dependencies in the \
given file (report RP0402 must not be disabled)'}
               ),
               ('int-import-graph',
                {'default' : '',
                 'type' : 'string',
                 'metavar' : '<file.dot>',
                 'help' : 'Create a graph of internal dependencies in the \
given file (report RP0402 must not be disabled)'}
               ),
              )

    def __init__(self, linter=None):
        BaseChecker.__init__(self, linter)
        self.stats = None
        self.import_graph = None
        self.__int_dep_info = self.__ext_dep_info = None
        self.reports = (('RP0401', 'External dependencies',
                         self.report_external_dependencies),
                        ('RP0402', 'Modules dependencies graph',
                         self.report_dependencies_graph),
                       )

    def open(self):
        """called before visiting project (i.e set of modules)"""
        self.linter.add_stats(dependencies={})
        self.linter.add_stats(cycles=[])
        self.stats = self.linter.stats
        self.import_graph = defaultdict(set)

    def close(self):
        """called before visiting project (i.e set of modules)"""
        # don't try to compute cycles if the associated message is disabled
        if self.linter.is_message_enabled('cyclic-import'):
            vertices = list(self.import_graph)
            for cycle in get_cycles(self.import_graph, vertices=vertices):
                self.add_message('cyclic-import', args=' -> '.join(cycle))

    def visit_import(self, node):
        """triggered when an import statement is seen"""
        modnode = node.root()
        for name, _ in node.names:
            importedmodnode = self.get_imported_module(node, name)
            if importedmodnode is None:
                continue
            self._check_relative_import(modnode, node, importedmodnode, name)
            self._add_imported_module(node, importedmodnode.name)
            self._check_deprecated_module(node, name)
            self._check_reimport(node, name)

    # TODO This appears to be the list of all messages of the checker...
    # @check_messages('W0410', 'W0401', 'W0403', 'W0402', 'W0404', 'W0406', 'F0401')
    @check_messages(*(MSGS.keys()))
    def visit_from(self, node):
        """triggered when a from statement is seen"""
        basename = node.modname
        if basename == '__future__':
            # check if this is the first non-docstring statement in the module
            prev = node.previous_sibling()
            if prev:
                # consecutive future statements are possible
                if not (isinstance(prev, astroid.From)
                        and prev.modname == '__future__'):
                    self.add_message('misplaced-future', node=node)
            return
        for name, _ in node.names:
            if name == '*':
                self.add_message('wildcard-import', args=basename, node=node)
        modnode = node.root()
        importedmodnode = self.get_imported_module(node, basename)
        if importedmodnode is None:
            return
        self._check_relative_import(modnode, node, importedmodnode, basename)
        self._check_deprecated_module(node, basename)
        for name, _ in node.names:
            if name != '*':
                self._add_imported_module(node, '%s.%s' % (importedmodnode.name, name))
                self._check_reimport(node, name, basename, node.level)

    def get_imported_module(self, importnode, modname):
        try:
            return importnode.do_import_module(modname)
        except astroid.InferenceError as ex:
            if str(ex) != modname:
                args = '%r (%s)' % (modname, ex)
            else:
                args = repr(modname)
            if not _except_import_error(importnode.parent):
                self.add_message("import-error", args=args, node=importnode)

    def _check_relative_import(self, modnode, importnode, importedmodnode,
                               importedasname):
        """check relative import. node is either an Import or From node, modname
        the imported module name.
        """
        if not self.linter.is_message_enabled('relative-import'):
            return
        if importedmodnode.file is None:
            return False # built-in module
        if modnode is importedmodnode:
            return False # module importing itself
        if modnode.absolute_import_activated() or getattr(importnode, 'level', None):
            return False
        if importedmodnode.name != importedasname:
            # this must be a relative import...
            self.add_message('relative-import',
                             args=(importedasname, importedmodnode.name),
                             node=importnode)

    def _add_imported_module(self, node, importedmodname):
        """notify an imported module, used to analyze dependencies"""
        try:
            importedmodname = get_module_part(importedmodname)
        except ImportError:
            pass
        context_name = node.root().name
        if context_name == importedmodname:
            # module importing itself !
            self.add_message('import-self', node=node)
        elif not is_standard_module(importedmodname):
            # handle dependencies
            importedmodnames = self.stats['dependencies'].setdefault(
                importedmodname, set())
            if not context_name in importedmodnames:
                importedmodnames.add(context_name)
            # update import graph
            mgraph = self.import_graph[context_name]
            if importedmodname not in mgraph:
                mgraph.add(importedmodname)

    def _check_deprecated_module(self, node, mod_path):
        """check if the module is deprecated"""
        for mod_name in self.config.deprecated_modules:
            if mod_path == mod_name or mod_path.startswith(mod_name + '.'):
                self.add_message('deprecated-module', node=node, args=mod_path)

    def _check_reimport(self, node, name, basename=None, level=None):
        """check if the import is necessary (i.e. not already done)"""
        if not self.linter.is_message_enabled('reimported'):
            return
        frame = node.frame()
        root = node.root()
        contexts = [(frame, level)]
        if root is not frame:
            contexts.append((root, None))
        for context, level in contexts:
            first = get_first_import(node, context, name, basename, level)
            if first is not None:
                self.add_message('reimported', node=node,
                                 args=(name, first.fromlineno))


    def report_external_dependencies(self, sect, _, dummy):
        """return a verbatim layout for displaying dependencies"""
        dep_info = make_tree_defs(six.iteritems(self._external_dependencies_info()))
        if not dep_info:
            raise EmptyReport()
        tree_str = repr_tree_defs(dep_info)
        sect.append(VerbatimText(tree_str))

    def report_dependencies_graph(self, sect, _, dummy):
        """write dependencies as a dot (graphviz) file"""
        dep_info = self.stats['dependencies']
        if not dep_info or not (self.config.import_graph
                                or self.config.ext_import_graph
                                or self.config.int_import_graph):
            raise EmptyReport()
        filename = self.config.import_graph
        if filename:
            make_graph(filename, dep_info, sect, '')
        filename = self.config.ext_import_graph
        if filename:
            make_graph(filename, self._external_dependencies_info(),
                       sect, 'external ')
        filename = self.config.int_import_graph
        if filename:
            make_graph(filename, self._internal_dependencies_info(),
                       sect, 'internal ')

    def _external_dependencies_info(self):
        """return cached external dependencies information or build and
        cache them
        """
        if self.__ext_dep_info is None:
            package = self.linter.current_name
            self.__ext_dep_info = result = {}
            for importee, importers in six.iteritems(self.stats['dependencies']):
                if not importee.startswith(package):
                    result[importee] = importers
        return self.__ext_dep_info

    def _internal_dependencies_info(self):
        """return cached internal dependencies information or build and
        cache them
        """
        if self.__int_dep_info is None:
            package = self.linter.current_name
            self.__int_dep_info = result = {}
            for importee, importers in six.iteritems(self.stats['dependencies']):
                if importee.startswith(package):
                    result[importee] = importers
        return self.__int_dep_info


def register(linter):
    """required method to auto register this checker """
    linter.register_checker(ImportsChecker(linter))