#
# This file is part of pysmi software.
#
# Copyright (c) 2015-2018, Ilya Etingof <etingof@gmail.com>
# License: http://snmplabs.com/pysmi/license.html
#
import os
import sys
import time
import imp
import struct
from pysmi.searcher.base import AbstractSearcher
from pysmi.compat import decode
from pysmi import debug
from pysmi import error


class PyFileSearcher(AbstractSearcher):
    """Figures out if given Python file (source or bytecode) exists at given
       location.
    """
    suffixes = {}
    for sfx, mode, typ in imp.get_suffixes():
        if typ not in suffixes:
            suffixes[typ] = []
        suffixes[typ].append((sfx, mode))

    def __init__(self, path):
        """Create an instance of *PyFileSearcher* bound to specific directory.

           Args:
             path (str): path to local directory
        """
        self._path = os.path.normpath(decode(path))

    def __str__(self):
        return '%s{"%s"}' % (self.__class__.__name__, self._path)

    def fileExists(self, mibname, mtime, rebuild=False):
        if rebuild:
            debug.logger & debug.flagSearcher and debug.logger('pretend %s is very old' % mibname)
            return

        mibname = decode(mibname)
        pyfile = os.path.join(self._path, mibname)

        for fmt in imp.PY_COMPILED, imp.PY_SOURCE:
            for pySfx, pyMode in self.suffixes[fmt]:
                f = pyfile + pySfx

                if not os.path.exists(f) or not os.path.isfile(f):
                    debug.logger & debug.flagSearcher and debug.logger('%s not present or not a file' % f)
                    continue

                if fmt == imp.PY_COMPILED:
                    try:
                        fp = open(f, pyMode)
                        pyData = fp.read(8)
                        fp.close()

                    except IOError:
                        raise error.PySmiSearcherError('failure opening compiled file %s: %s' % (f, sys.exc_info()[1]),
                                                       searcher=self)
                    if pyData[:4] == imp.get_magic():
                        pyData = pyData[4:]
                        pyTime = struct.unpack('<L', pyData[:4])[0]
                        debug.logger & debug.flagSearcher and debug.logger(
                            'found %s, mtime %s' % (f, time.strftime("%a, %d %b %Y %H:%M:%S GMT", time.gmtime(pyTime))))
                        if pyTime >= mtime:
                            raise error.PySmiFileNotModifiedError()

                        else:
                            raise error.PySmiFileNotFoundError('older file %s exists' % mibname, searcher=self)

                    else:
                        debug.logger & debug.flagSearcher and debug.logger('bad magic in %s' % f)
                        continue
                else:
                    try:
                        pyTime = os.stat(f)[8]

                    except OSError:
                        raise error.PySmiSearcherError('failure opening compiled file %s: %s' % (f, sys.exc_info()[1]),
                                                       searcher=self)

                    debug.logger & debug.flagSearcher and debug.logger(
                        'found %s, mtime %s' % (f, time.strftime("%a, %d %b %Y %H:%M:%S GMT", time.gmtime(pyTime))))

                    if pyTime >= mtime:
                        raise error.PySmiFileNotModifiedError()

        raise error.PySmiFileNotFoundError('no compiled file %s found' % mibname, searcher=self)