"""
Implementation of the interpreter-level default import logic.
"""

import sys, os, stat

from pypy.interpreter.module import Module
from pypy.interpreter import gateway
from pypy.interpreter.error import OperationError, operationerrfmt
from pypy.interpreter.baseobjspace import W_Root, ObjSpace
from pypy.interpreter.eval import Code
from pypy.rlib import streamio
from pypy.rlib.streamio import StreamErrors
from pypy.rlib.rarithmetic import intmask
from pypy.rlib.objectmodel import we_are_translated

SEARCH_ERROR = 0
PY_SOURCE = 1
PY_COMPILED = 2
C_EXTENSION = 3
# PY_RESOURCE = 4
PKG_DIRECTORY = 5
C_BUILTIN = 6
PY_FROZEN = 7
# PY_CODERESOURCE = 8
IMP_HOOK = 9

def find_modtype(space, filepart):
    """Check which kind of module to import for the given filepart,
    which is a path without extension.  Returns PY_SOURCE, PY_COMPILED or
    SEARCH_ERROR.
    """
    # check the .py file
    pyfile = filepart + ".py"
    if os.path.exists(pyfile) and case_ok(pyfile):
        return PY_SOURCE, ".py", "U"

    # The .py file does not exist.  By default on PyPy, lonepycfiles
    # is False: if a .py file does not exist, we don't even try to
    # look for a lone .pyc file.
    # The "imp" module does not respect this, and is allowed to find
    # lone .pyc files.
    if not space.config.objspace.lonepycfiles:
        return SEARCH_ERROR, None, None

    # check the .pyc file
    if space.config.objspace.usepycfiles:
        pycfile = filepart + ".pyc"
        if os.path.exists(pycfile) and case_ok(pycfile):
            # existing .pyc file
            return PY_COMPILED, ".pyc", "rb"

    return SEARCH_ERROR, None, None

if sys.platform in ['linux2', 'freebsd']:
    def case_ok(filename):
        return True
else:
    # XXX that's slow
    def case_ok(filename):
        index = filename.rfind(os.sep)
        if index < 0:
            directory = os.curdir
        else:
            directory = filename[:index+1]
            filename = filename[index+1:]
        try:
            return filename in os.listdir(directory)
        except OSError:
            return False

def try_getattr(space, w_obj, w_name):
    try:
        return space.getattr(w_obj, w_name)
    except OperationError, e:
        # ugh, but blame CPython :-/ this is supposed to emulate
        # hasattr, which eats all exceptions.
        return None

def check_sys_modules(space, w_modulename):
    return space.finditem(space.sys.get('modules'), w_modulename)

def importhook(space, modulename, w_globals=None,
               w_locals=None, w_fromlist=None, level=-1):
    timername = "importhook " + modulename
    space.timer.start(timername)
    if not modulename and level < 0: 
        raise OperationError(
            space.w_ValueError,
            space.wrap("Empty module name"))
    w = space.wrap

    ctxt_name = None
    if w_globals is not None and not space.is_w(w_globals, space.w_None):
        ctxt_w_name = space.finditem(w_globals, w('__name__'))
        ctxt_w_path = space.finditem(w_globals, w('__path__'))
        if ctxt_w_name is not None:
            try:
                ctxt_name = space.str_w(ctxt_w_name)
            except OperationError, e:
                if not e.match(space, space.w_TypeError):
                    raise
    else:
        ctxt_w_path = None
        
    rel_modulename = None
    if ctxt_name is not None:
        if level == 0:
            baselevel = 0
            rel_modulename = modulename
        else:
            ctxt_name_prefix_parts = ctxt_name.split('.')
            if level > 0:
                n = len(ctxt_name_prefix_parts)-level+1
                assert n>=0
                ctxt_name_prefix_parts = ctxt_name_prefix_parts[:n]
            if ctxt_w_path is None: # plain module
                ctxt_name_prefix_parts.pop()
            if ctxt_name_prefix_parts:
                rel_modulename = '.'.join(ctxt_name_prefix_parts)
                if modulename:
                    rel_modulename += '.' + modulename
            baselevel = len(ctxt_name_prefix_parts)
            
        if rel_modulename is not None:
            w_mod = check_sys_modules(space, w(rel_modulename))
            if (w_mod is None or
                not space.is_w(w_mod, space.w_None)):
                
                w_mod = absolute_import(space, rel_modulename,
                                        baselevel,
                                        w_fromlist, tentative=1)
                if w_mod is not None:
                    space.timer.stop(timername)
                    return w_mod
            else:
                rel_modulename = None
    if level > 0:
        msg = "Attempted relative import in non-package"
        raise OperationError(space.w_ValueError, w(msg))
    w_mod = absolute_import(space, modulename, 0, w_fromlist, tentative=0)
    if rel_modulename is not None:
        space.setitem(space.sys.get('modules'), w(rel_modulename),space.w_None)
    space.timer.stop(timername)
    return w_mod
#
importhook.unwrap_spec = [ObjSpace, str, W_Root, W_Root, W_Root, int]

def absolute_import(space, modulename, baselevel, w_fromlist, tentative):
    lock = getimportlock(space)
    lock.acquire_lock()
    try:
        return _absolute_import(space, modulename, baselevel,
                                w_fromlist, tentative)
    finally:
        lock.release_lock()

def _absolute_import(space, modulename, baselevel, w_fromlist, tentative):
    w = space.wrap

    w_mod = None
    parts = modulename.split('.')
    prefix = []
    w_path = None

    first = None
    level = 0

    for part in parts:
        w_mod = load_part(space, w_path, prefix, part, w_mod,
                          tentative=tentative)
        if w_mod is None:
            return None

        if baselevel == level:
            first = w_mod
            tentative = 0
        prefix.append(part)
        w_path = try_getattr(space, w_mod, w('__path__'))
        level += 1

    if w_fromlist is not None and space.is_true(w_fromlist):
        if w_path is not None:
            fromlist_w = space.unpackiterable(w_fromlist)
            if len(fromlist_w) == 1 and space.eq_w(fromlist_w[0],w('*')):
                w_all = try_getattr(space, w_mod, w('__all__'))
                if w_all is not None:
                    fromlist_w = space.unpackiterable(w_all)
            for w_name in fromlist_w:
                if try_getattr(space, w_mod, w_name) is None:
                    load_part(space, w_path, prefix, space.str_w(w_name), w_mod,
                              tentative=1)
        return w_mod
    else:
        return first

def find_in_meta_path(space, w_modulename, w_path):
    assert w_modulename is not None
    if w_path is None:
        w_path = space.w_None
    for w_hook in space.unpackiterable(space.sys.get("meta_path")):
        w_loader = space.call_method(w_hook, "find_module",
                                     w_modulename, w_path)
        if space.is_true(w_loader):
            return w_loader

def find_in_path_hooks(space, w_modulename, w_pathitem):
    w_path_importer_cache = space.sys.get("path_importer_cache")
    w_importer = space.finditem(w_path_importer_cache, w_pathitem)
    if w_importer is None:
        w_importer = space.w_None
        space.setitem(w_path_importer_cache, w_pathitem, w_importer)
        for w_hook in space.unpackiterable(space.sys.get("path_hooks")):
            try:
                w_importer = space.call_function(w_hook, w_pathitem)
            except OperationError, e:
                if not e.match(space, space.w_ImportError):
                    raise
            else:
                break
        if space.is_true(w_importer):
            space.setitem(w_path_importer_cache, w_pathitem, w_importer)
    if space.is_true(w_importer):
        w_loader = space.call_method(w_importer, "find_module", w_modulename)
        if space.is_true(w_loader):
            return w_loader

class FindInfo:
    def __init__(self, modtype, filename, stream,
                 suffix="", filemode="", w_loader=None):
        self.modtype = modtype
        self.filename = filename
        self.stream = stream
        self.suffix = suffix
        self.filemode = filemode
        self.w_loader = w_loader

    @staticmethod
    def fromLoader(w_loader):
        return FindInfo(IMP_HOOK, '', None, w_loader=w_loader)

def find_module(space, modulename, w_modulename, partname, w_path,
                use_loader=True):
    # Examin importhooks (PEP302) before doing the import
    if use_loader:
        w_loader  = find_in_meta_path(space, w_modulename, w_path)
        if w_loader:
            return FindInfo.fromLoader(w_loader)

    # XXX Check for frozen modules?
    #     when w_path is a string

    if w_path is None:
        # check the builtin modules
        if modulename in space.builtin_modules:
            return FindInfo(C_BUILTIN, modulename, None)
        w_path = space.sys.get('path')

    # XXX check frozen modules?
    #     when w_path is null

    if w_path is not None:
        for w_pathitem in space.unpackiterable(w_path):
            # sys.path_hooks import hook
            if use_loader:
                w_loader = find_in_path_hooks(space, w_modulename, w_pathitem)
                if w_loader:
                    return FindInfo.fromLoader(w_loader)

            path = space.str_w(w_pathitem)
            filepart = os.path.join(path, partname)
            if os.path.isdir(filepart) and case_ok(filepart):
                initfile = os.path.join(filepart, '__init__')
                modtype, _, _ = find_modtype(space, initfile)
                if modtype in (PY_SOURCE, PY_COMPILED):
                    return FindInfo(PKG_DIRECTORY, filepart, None)
                else:
                    msg = "Not importing directory " +\
                            "'%s' missing __init__.py" % (filepart,)
                    space.warn(msg, space.w_ImportWarning)
            modtype, suffix, filemode = find_modtype(space, filepart)
            try:
                if modtype in (PY_SOURCE, PY_COMPILED):
                    filename = filepart + suffix
                    stream = streamio.open_file_as_stream(filename, filemode)
                    try:
                        return FindInfo(modtype, filename, stream, suffix, filemode)
                    except:
                        stream.close()
                        raise
            except StreamErrors:
                pass

    # not found
    return None

def _prepare_module(space, w_mod, filename, pkgdir):
    w = space.wrap
    space.sys.setmodule(w_mod)
    space.setattr(w_mod, w('__file__'), space.wrap(filename))
    space.setattr(w_mod, w('__doc__'), space.w_None)
    if pkgdir is not None:
        space.setattr(w_mod, w('__path__'), space.newlist([w(pkgdir)]))

def load_module(space, w_modulename, find_info, reuse=False):
    if find_info is None:
        return
    if find_info.w_loader:
        return space.call_method(find_info.w_loader, "load_module", w_modulename)

    if find_info.modtype == C_BUILTIN:
        return space.getbuiltinmodule(find_info.filename, force_init=True)

    if find_info.modtype in (PY_SOURCE, PY_COMPILED, PKG_DIRECTORY):
        if reuse:
            w_mod = space.getitem(space.sys.get('modules'), w_modulename)
        else:
            w_mod = space.wrap(Module(space, w_modulename))
        if find_info.modtype == PKG_DIRECTORY:
            pkgdir = find_info.filename
        else:
            pkgdir = None
        _prepare_module(space, w_mod, find_info.filename, pkgdir)

        try:
            if find_info.modtype == PY_SOURCE:
                load_source_module(space, w_modulename, w_mod, find_info.filename,
                                   find_info.stream.readall())
                return w_mod
            elif find_info.modtype == PY_COMPILED:
                magic = _r_long(find_info.stream)
                timestamp = _r_long(find_info.stream)
                load_compiled_module(space, w_modulename, w_mod, find_info.filename,
                                     magic, timestamp, find_info.stream.readall())
                return w_mod
            elif find_info.modtype == PKG_DIRECTORY:
                w_path = space.newlist([space.wrap(find_info.filename)])
                space.setattr(w_mod, space.wrap('__path__'), w_path)
                find_info = find_module(space, "__init__", None, "__init__",
                                        w_path, use_loader=False)
                if find_info is None:
                    return w_mod
                try:
                    load_module(space, w_modulename, find_info, reuse=True)
                finally:
                    find_info.stream.close()
                # fetch the module again, in case of "substitution"
                w_mod = check_sys_modules(space, w_modulename)
                return w_mod
        except OperationError:
            w_mods = space.sys.get('modules')
            space.call_method(w_mods, 'pop', w_modulename, space.w_None)
            raise

def load_part(space, w_path, prefix, partname, w_parent, tentative):
    w = space.wrap
    modulename = '.'.join(prefix + [partname])
    w_modulename = w(modulename)
    w_mod = check_sys_modules(space, w_modulename)

    if w_mod is not None:
        if not space.is_w(w_mod, space.w_None):
            return w_mod
    elif not prefix or w_path is not None:
        find_info = find_module(
            space, modulename, w_modulename, partname, w_path)

        try:
            if find_info:
                w_mod = load_module(space, w_modulename, find_info)
                w_mod = space.getitem(space.sys.get("modules"), w_modulename)
                if w_parent is not None:
                    space.setattr(w_parent, space.wrap(partname), w_mod)
                return w_mod
        finally:
            if find_info:
                stream = find_info.stream
                if stream:
                    stream.close()

    if tentative:
        return None
    else:
        # ImportError
        msg = "No module named %s"
        raise operationerrfmt(space.w_ImportError, msg, modulename)

def reload(space, w_module):
    """Reload the module.
    The module must have been successfully imported before."""
    if not space.is_w(space.type(w_module), space.type(space.sys)):
        raise OperationError(
            space.w_TypeError,
            space.wrap("reload() argument must be module"))

    w_modulename = space.getattr(w_module, space.wrap("__name__"))
    modulename = space.str_w(w_modulename)
    if not space.is_w(check_sys_modules(space, w_modulename), w_module):
        raise operationerrfmt(
            space.w_ImportError,
            "reload(): module %s not in sys.modules", modulename)

    try:
        w_mod = space.reloading_modules[modulename]
        # Due to a recursive reload, this module is already being reloaded.
        return w_mod
    except KeyError:
        pass

    space.reloading_modules[modulename] = w_module
    try:
        namepath = modulename.split('.')
        subname = namepath[-1]
        parent_name = '.'.join(namepath[:-1])
        parent = None
        if parent_name:
            w_parent = check_sys_modules(space, space.wrap(parent_name))
            if w_parent is None:
                raise operationerrfmt(
                    space.w_ImportError,
                    "reload(): parent %s not in sys.modules",
                    parent_name)
            w_path = space.getattr(w_parent, space.wrap("__path__"))
        else:
            w_path = None

        find_info = find_module(
            space, modulename, w_modulename, subname, w_path)

        if not find_info:
            # ImportError
            msg = "No module named %s"
            raise operationerrfmt(space.w_ImportError, msg, modulename)

        try:
            try:
                return load_module(space, w_modulename, find_info, reuse=True)
            finally:
                if find_info.stream:
                    find_info.stream.close()
        except:
            # load_module probably removed name from modules because of
            # the error.  Put back the original module object.
            space.sys.setmodule(w_module)
            raise
    finally:
        space.reloading_modules.clear()


# __________________________________________________________________
#
# import lock, to prevent two threads from running module-level code in
# parallel.  This behavior is more or less part of the language specs,
# as an attempt to avoid failure of 'from x import y' if module x is
# still being executed in another thread.

# This logic is tested in pypy.module.thread.test.test_import_lock.

class ImportRLock:

    def __init__(self, space):
        self.space = space
        self.lock = None
        self.lockowner = None
        self.lockcounter = 0

    def lock_held(self):
        me = self.space.getexecutioncontext()   # used as thread ident
        return self.lockowner is me

    def _can_have_lock(self):
        # hack: we can't have self.lock != None during translation,
        # because prebuilt lock objects are not allowed.  In this
        # special situation we just don't lock at all (translation is
        # not multithreaded anyway).
        if we_are_translated():
            return True     # we need a lock at run-time
        elif self.space.config.translating:
            assert self.lock is None
            return False
        else:
            return True     # in py.py

    def acquire_lock(self):
        # this function runs with the GIL acquired so there is no race
        # condition in the creation of the lock
        if self.lock is None:
            if not self._can_have_lock():
                return
            self.lock = self.space.allocate_lock()
        me = self.space.getexecutioncontext()   # used as thread ident
        if self.lockowner is me:
            pass    # already acquired by the current thread
        else:
            self.lock.acquire(True)
            assert self.lockowner is None
            assert self.lockcounter == 0
            self.lockowner = me
        self.lockcounter += 1

    def release_lock(self):
        me = self.space.getexecutioncontext()   # used as thread ident
        if self.lockowner is not me:
            if not self._can_have_lock():
                return
            space = self.space
            raise OperationError(space.w_RuntimeError,
                                 space.wrap("not holding the import lock"))
        assert self.lockcounter > 0
        self.lockcounter -= 1
        if self.lockcounter == 0:
            self.lockowner = None
            self.lock.release()

def getimportlock(space):
    return space.fromcache(ImportRLock)

# __________________________________________________________________
#
# .pyc file support

"""
   Magic word to reject .pyc files generated by other Python versions.
   It should change for each incompatible change to the bytecode.

   The value of CR and LF is incorporated so if you ever read or write
   a .pyc file in text mode the magic number will be wrong; also, the
   Apple MPW compiler swaps their values, botching string constants.

   CPython uses values between 20121 - 62xxx

"""

# XXX picking a magic number is a mess.  So far it works because we
# have only two extra opcodes, which bump the magic number by +1 and
# +2 respectively, and CPython leaves a gap of 10 when it increases
# its own magic number.  To avoid assigning exactly the same numbers
# as CPython we always add a +2.  We'll have to think again when we
# get at the fourth new opcode :-(
#
#  * CALL_LIKELY_BUILTIN    +1
#  * CALL_METHOD            +2
#
# In other words:
#
#     default_magic        -- used by CPython without the -U option
#     default_magic + 1    -- used by CPython with the -U option
#     default_magic + 2    -- used by PyPy without any extra opcode
#     ...
#     default_magic + 5    -- used by PyPy with both extra opcodes
#
from pypy.interpreter.pycode import default_magic
MARSHAL_VERSION_FOR_PYC = 2

def get_pyc_magic(space):
    # XXX CPython testing hack: delegate to the real imp.get_magic
    if not we_are_translated():
        if '__pypy__' not in space.builtin_modules:
            import struct
            magic = __import__('imp').get_magic()
            return struct.unpack('<i', magic)[0]

    result = default_magic
    if space.config.objspace.opcodes.CALL_LIKELY_BUILTIN:
        result += 1
    if space.config.objspace.opcodes.CALL_METHOD:
        result += 2
    return result


def parse_source_module(space, pathname, source):
    """ Parse a source file and return the corresponding code object """
    ec = space.getexecutioncontext()
    pycode = ec.compiler.compile(source, pathname, 'exec', 0)
    return pycode

def exec_code_module(space, w_mod, code_w):
    w_dict = space.getattr(w_mod, space.wrap('__dict__'))
    space.call_method(w_dict, 'setdefault',
                      space.wrap('__builtins__'),
                      space.wrap(space.builtin))
    code_w.exec_code(space, w_dict, w_dict)


def load_source_module(space, w_modulename, w_mod, pathname, source,
                       write_pyc=True):
    """
    Load a source module from a given file and return its module
    object.
    """
    w = space.wrap

    if space.config.objspace.usepycfiles:
        cpathname = pathname + 'c'
        mtime = int(os.stat(pathname)[stat.ST_MTIME])
        stream = check_compiled_module(space, cpathname, mtime)
    else:
        cpathname = None
        mtime = 0
        stream = None

    if stream:
        # existing and up-to-date .pyc file
        try:
            code_w = read_compiled_module(space, cpathname, stream.readall())
        finally:
            stream.close()
        space.setattr(w_mod, w('__file__'), w(cpathname))
    else:
        code_w = parse_source_module(space, pathname, source)

        if space.config.objspace.usepycfiles and write_pyc:
            write_compiled_module(space, code_w, cpathname, mtime)

    exec_code_module(space, w_mod, code_w)

    return w_mod

def _get_long(s):
    a = ord(s[0])
    b = ord(s[1])
    c = ord(s[2])
    d = ord(s[3])
    if d >= 0x80:
        d -= 0x100
    return a | (b<<8) | (c<<16) | (d<<24)

def _read_n(stream, n):
    buf = ''
    while len(buf) < n:
        data = stream.read(n - len(buf))
        if not data:
            raise streamio.StreamError("end of file")
        buf += data
    return buf

def _r_long(stream):
    s = _read_n(stream, 4)
    return _get_long(s)

def _w_long(stream, x):
    a = x & 0xff
    x >>= 8
    b = x & 0xff
    x >>= 8
    c = x & 0xff
    x >>= 8
    d = x & 0xff
    stream.write(chr(a) + chr(b) + chr(c) + chr(d))

def check_compiled_module(space, pycfilename, expected_mtime):
    """
    Check if a pyc file's magic number and mtime match.
    """
    stream = None
    try:
        stream = streamio.open_file_as_stream(pycfilename, "rb")
        magic = _r_long(stream)
        if magic != get_pyc_magic(space):
            stream.close()
            return None
        pyc_mtime = _r_long(stream)
        if pyc_mtime != expected_mtime:
            stream.close()
            return None
        return stream
    except StreamErrors:
        if stream:
            stream.close()
        return None

def read_compiled_module(space, cpathname, strbuf):
    """ Read a code object from a file and check it for validity """
    
    w_marshal = space.getbuiltinmodule('marshal')
    w_code = space.call_method(w_marshal, 'loads', space.wrap(strbuf))
    pycode = space.interpclass_w(w_code)
    if pycode is None or not isinstance(pycode, Code):
        raise operationerrfmt(space.w_ImportError,
                              "Non-code object in %s", cpathname)
    return pycode

def load_compiled_module(space, w_modulename, w_mod, cpathname, magic,
                         timestamp, source):
    """
    Load a module from a compiled file, execute it, and return its
    module object.
    """
    w = space.wrap
    if magic != get_pyc_magic(space):
        raise operationerrfmt(space.w_ImportError,
                              "Bad magic number in %s", cpathname)
    #print "loading pyc file:", cpathname
    code_w = read_compiled_module(space, cpathname, source)
    exec_code_module(space, w_mod, code_w)

    return w_mod


def write_compiled_module(space, co, cpathname, mtime):
    """
    Write a compiled module to a file, placing the time of last
    modification of its source into the header.
    Errors are ignored, if a write error occurs an attempt is made to
    remove the file.
    """
    w_marshal = space.getbuiltinmodule('marshal')
    try:
        w_str = space.call_method(w_marshal, 'dumps', space.wrap(co),
                                  space.wrap(MARSHAL_VERSION_FOR_PYC))
        strbuf = space.str_w(w_str)
    except OperationError, e:
        if e.async(space):
            raise
        #print "Problem while marshalling %s, skipping" % cpathname
        return
    #
    # Careful here: we must not crash nor leave behind something that looks
    # too much like a valid pyc file but really isn't one.
    #
    try:
        stream = streamio.open_file_as_stream(cpathname, "wb")
    except StreamErrors:
        return    # cannot create file
    try:
        try:
            # will patch the header later; write zeroes until we are sure that
            # the rest of the file is valid
            _w_long(stream, 0)   # pyc_magic
            _w_long(stream, 0)   # mtime
            stream.write(strbuf)

            # should be ok (XXX or should call os.fsync() to be sure?)
            stream.seek(0, 0)
            _w_long(stream, get_pyc_magic(space))
            _w_long(stream, mtime)
        finally:
            stream.close()
    except StreamErrors:
        try:
            os.unlink(cpathname)
        except OSError:
            pass