import os

from mocker import MockerTestCase

from cloudinit import helpers as ch
from cloudinit import util

import shutil

# Makes the old path start
# with new base instead of whatever
# it previously had
def rebase_path(old_path, new_base):
    if old_path.startswith(new_base):
        # Already handled...
        return old_path
    # Retarget the base of that path
    # to the new base instead of the
    # old one...
    path = os.path.join(new_base, old_path.lstrip("/"))
    path = os.path.abspath(path)
    return path


# Can work on anything that takes a path as arguments
def retarget_many_wrapper(new_base, am, old_func):
    def wrapper(*args, **kwds):
        n_args = list(args)
        nam = am
        if am == -1:
            nam = len(n_args)
        for i in range(0, nam):
            path = args[i]
            n_args[i] = rebase_path(path, new_base)
        return old_func(*n_args, **kwds)
    return wrapper


class ResourceUsingTestCase(MockerTestCase):
    def __init__(self, methodName="runTest"):
        MockerTestCase.__init__(self, methodName)
        self.resource_path = None

    def resourceLocation(self, subname=None):
        if self.resource_path is None:
            paths = [
                os.path.join('tests', 'data'),
                os.path.join('data'),
                os.path.join(os.pardir, 'tests', 'data'),
                os.path.join(os.pardir, 'data'),
            ]
            for p in paths:
                if os.path.isdir(p):
                    self.resource_path = p
                    break
        self.assertTrue((self.resource_path and
                         os.path.isdir(self.resource_path)),
                        msg="Unable to locate test resource data path!")
        if not subname:
            return self.resource_path
        return os.path.join(self.resource_path, subname)

    def readResource(self, name):
        where = self.resourceLocation(name)
        with open(where, 'r') as fh:
            return fh.read()

    def getCloudPaths(self):
        cp = ch.Paths({
            'cloud_dir': self.makeDir(),
            'templates_dir': self.resourceLocation(),
        })
        return cp


class FilesystemMockingTestCase(ResourceUsingTestCase):
    def __init__(self, methodName="runTest"):
        ResourceUsingTestCase.__init__(self, methodName)
        self.patched_funcs = []

    def replicateTestRoot(self, example_root, target_root):
        real_root = self.resourceLocation()
        real_root = os.path.join(real_root, 'roots', example_root)
        for (dir_path, _dirnames, filenames) in os.walk(real_root):
            real_path = dir_path
            make_path = rebase_path(real_path[len(real_root):], target_root)
            util.ensure_dir(make_path)
            for f in filenames:
                real_path = util.abs_join(real_path, f)
                make_path = util.abs_join(make_path, f)
                shutil.copy(real_path, make_path)

    def tearDown(self):
        self.restore()
        ResourceUsingTestCase.tearDown(self)

    def restore(self):
        for (mod, f, func) in self.patched_funcs:
            setattr(mod, f, func)
        self.patched_funcs = []

    def patchUtils(self, new_root):
        patch_funcs = {
            util: [('write_file', 1),
                   ('load_file', 1),
                   ('ensure_dir', 1),
                   ('chmod', 1),
                   ('delete_dir_contents', 1),
                   ('del_file', 1),
                   ('sym_link', -1)],
        }
        for (mod, funcs) in patch_funcs.items():
            for (f, am) in funcs:
                func = getattr(mod, f)
                trap_func = retarget_many_wrapper(new_root, am, func)
                setattr(mod, f, trap_func)
                self.patched_funcs.append((mod, f, func))

        # Handle subprocess calls
        func = getattr(util, 'subp')

        def nsubp(*_args, **_kwargs):
            return ('', '')

        setattr(util, 'subp', nsubp)
        self.patched_funcs.append((util, 'subp', func))

        def null_func(*_args, **_kwargs):
            return None

        for f in ['chownbyid', 'chownbyname']:
            func = getattr(util, f)
            setattr(util, f, null_func)
            self.patched_funcs.append((util, f, func))

    def patchOS(self, new_root):
        patch_funcs = {
            os.path: ['isfile', 'exists', 'islink', 'isdir'],
        }
        for (mod, funcs) in patch_funcs.items():
            for f in funcs:
                func = getattr(mod, f)
                trap_func = retarget_many_wrapper(new_root, 1, func)
                setattr(mod, f, trap_func)
                self.patched_funcs.append((mod, f, func))