#!/usr/bin/env python
# coding: utf-8

# # Importing IPython Notebooks as Modules

# It is a common problem that people want to import code from IPython Notebooks.
# This is made difficult by the fact that Notebooks are not plain Python files,
# and thus cannot be imported by the regular Python machinery.
# 
# Fortunately, Python provides some fairly sophisticated [hooks](http://www.python.org/dev/peps/pep-0302/) into the import machinery,
# so we can actually make IPython notebooks importable without much difficulty,
# and only using public APIs.

# In[ ]:


import io, os, sys, types


# In[ ]:


from IPython import get_ipython
from IPython.nbformat import current
from IPython.core.interactiveshell import InteractiveShell


# Import hooks typically take the form of two objects:
# 
# 1. a Module **Loader**, which takes a module name (e.g. `'IPython.display'`), and returns a Module
# 2. a Module **Finder**, which figures out whether a module might exist, and tells Python what **Loader** to use

# In[ ]:


def find_notebook(fullname, path=None):
    """find a notebook, given its fully qualified name and an optional path
    
    This turns "foo.bar" into "foo/bar.ipynb"
    and tries turning "Foo_Bar" into "Foo Bar" if Foo_Bar
    does not exist.
    """
    name = fullname.rsplit('.', 1)[-1]
    if not path:
        path = ['']
    for d in path:
        nb_path = os.path.join(d, name + ".ipynb")
        if os.path.isfile(nb_path):
            return nb_path
        # let import Notebook_Name find "Notebook Name.ipynb"
        nb_path = nb_path.replace("_", " ")
        if os.path.isfile(nb_path):
            return nb_path
            


# ## Notebook Loader

# Here we have our Notebook Loader.
# It's actually quite simple - once we figure out the filename of the module,
# all it does is:
# 
# 1. load the notebook document into memory
# 2. create an empty Module
# 3. execute every cell in the Module namespace
# 
# Since IPython cells can have extended syntax,
# the IPython transform is applied to turn each of these cells into their pure-Python counterparts before executing them.
# If all of your notebook cells are pure-Python,
# this step is unnecessary.

# In[ ]:


class NotebookLoader(object):
    """Module Loader for IPython Notebooks"""
    def __init__(self, path=None):
        self.shell = InteractiveShell.instance()
        self.path = path
    
    def load_module(self, fullname):
        """import a notebook as a module"""
        path = find_notebook(fullname, self.path)
        
        print ("importing IPython notebook from %s" % path)
                                       
        # load the notebook object
        with io.open(path, 'r', encoding='utf-8') as f:
            nb = current.read(f, 'json')
        
        
        # create the module and add it to sys.modules
        # if name in sys.modules:
        #    return sys.modules[name]
        mod = types.ModuleType(fullname)
        mod.__file__ = path
        mod.__loader__ = self
        mod.__dict__['get_ipython'] = get_ipython
        sys.modules[fullname] = mod
        
        # extra work to ensure that magics that would affect the user_ns
        # actually affect the notebook module's ns
        save_user_ns = self.shell.user_ns
        self.shell.user_ns = mod.__dict__
        
        try:
          for cell in nb.worksheets[0].cells:
            if cell.cell_type == 'code' and cell.language == 'python':
                # transform the input to executable Python
                code = self.shell.input_transformer_manager.transform_cell(cell.input)
                # run the code in themodule
                exec(code, mod.__dict__)
        finally:
            self.shell.user_ns = save_user_ns
        return mod


# ## The Module Finder

# The finder is a simple object that tells you whether a name can be imported,
# and returns the appropriate loader.
# All this one does is check, when you do:
# 
# ```python
# import mynotebook
# ```
# 
# it checks whether `mynotebook.ipynb` exists.
# If a notebook is found, then it returns a NotebookLoader.
# 
# Any extra logic is just for resolving paths within packages.

# In[ ]:


class NotebookFinder(object):
    """Module finder that locates IPython Notebooks"""
    def __init__(self):
        self.loaders = {}
    
    def find_module(self, fullname, path=None):
        nb_path = find_notebook(fullname, path)
        if not nb_path:
            return
        
        key = path
        if path:
            # lists aren't hashable
            key = os.path.sep.join(path)
        
        if key not in self.loaders:
            self.loaders[key] = NotebookLoader(path)
        return self.loaders[key]


# ## Register the hook

# Now we register the `NotebookFinder` with `sys.meta_path`

# In[ ]:


sys.meta_path.append(NotebookFinder())


# After this point, my notebooks should be importable.
# 
# Let's look at what we have in the CWD:

# In[ ]:


ls nbpackage


# So I should be able to `import nbimp.mynotebook`.
# 

# ### Aside: displaying notebooks

# Here is some simple code to display the contents of a notebook
# with syntax highlighting, etc.

# In[ ]:


from pygments import highlight
from pygments.lexers import PythonLexer
from pygments.formatters import HtmlFormatter

from IPython.display import display, HTML

formatter = HtmlFormatter()
lexer = PythonLexer()

# publish the CSS for pygments highlighting
display(HTML("""
<style type='text/css'>
%s
</style>
""" % formatter.get_style_defs()
))


# In[ ]:


def show_notebook(fname):
    """display a short summary of the cells of a notebook"""
    with io.open(fname, 'r', encoding='utf-8') as f:
        nb = current.read(f, 'json')
    html = []
    for cell in nb.worksheets[0].cells:
        html.append("<h4>%s cell</h4>" % cell.cell_type)
        if cell.cell_type == 'code':
            html.append(highlight(cell.input, lexer, formatter))
        else:
            html.append("<pre>%s</pre>" % cell.source)
    display(HTML('\n'.join(html)))

show_notebook(os.path.join("nbpackage", "mynotebook.ipynb"))


# So my notebook has a heading cell and some code cells,
# one of which contains some IPython syntax.
# 
# Let's see what happens when we import it

# In[ ]:


from nbpackage import mynotebook


# Hooray, it imported!  Does it work?

# In[ ]:


mynotebook.foo()


# Hooray again!
# 
# Even the function that contains IPython syntax works:

# In[ ]:


mynotebook.has_ip_syntax()


# ## Notebooks in packages

# We also have a notebook inside the `nb` package,
# so let's make sure that works as well.

# In[ ]:


ls nbpackage/nbs


# Note that the `__init__.py` is necessary for `nb` to be considered a package,
# just like usual.

# In[ ]:


show_notebook(os.path.join("nbpackage", "nbs", "other.ipynb"))


# In[ ]:


from nbpackage.nbs import other
other.bar(5)


# So now we have importable notebooks, from both the local directory and inside packages.
# 
# I can even put a notebook inside IPython, to further demonstrate that this is working properly:

# In[ ]:


import shutil
from IPython.utils.path import get_ipython_package_dir

utils = os.path.join(get_ipython_package_dir(), 'utils')
shutil.copy(os.path.join("nbpackage", "mynotebook.ipynb"),
            os.path.join(utils, "inside_ipython.ipynb")
)


# and import the notebook from `IPython.utils`

# In[ ]:


from IPython.utils import inside_ipython
inside_ipython.whatsmyname()


# This approach can even import functions and classes that are defined in a notebook using the `%%cython` magic.