# -*- coding: utf-8 -*-

"""Functions for generating a project from a project template."""
from __future__ import unicode_literals
from collections import OrderedDict
import fnmatch
import io
import json
import logging
import os
import shutil

from jinja2 import FileSystemLoader
from cookiecutter.environment import StrictEnvironment
from jinja2.exceptions import TemplateSyntaxError, UndefinedError
from binaryornot.check import is_binary

from .exceptions import (
    NonTemplatedInputDirException,
    ContextDecodingException,
    FailedHookException,
    OutputDirExistsException,
    UndefinedVariableInTemplate
)
from .find import find_template
from .utils import make_sure_path_exists, work_in, rmtree
from .hooks import run_hook

logger = logging.getLogger(__name__)


def is_copy_only_path(path, context):
    """Check whether the given `path` should only be copied as opposed to being
    rendered.

    Returns True if `path` matches a pattern in the given `context` dict,
    otherwise False.

    :param path: A file-system path referring to a file or dir that
        should be rendered or just copied.
    :param context: cookiecutter context.
    """
    try:
        for dont_render in context['cookiecutter']['_copy_without_render']:
            if fnmatch.fnmatch(path, dont_render):
                return True
    except KeyError:
        return False

    return False


def apply_overwrites_to_context(context, overwrite_context):
    """Modify the given context in place based on the overwrite_context."""
    for variable, overwrite in overwrite_context.items():
        if variable not in context:
            # Do not include variables which are not used in the template
            continue

        context_value = context[variable]

        if isinstance(context_value, list):
            # We are dealing with a choice variable
            if overwrite in context_value:
                # This overwrite is actually valid for the given context
                # Let's set it as default (by definition first item in list)
                # see ``cookiecutter.prompt.prompt_choice_for_config``
                context_value.remove(overwrite)
                context_value.insert(0, overwrite)
        else:
            # Simply overwrite the value for this variable
            context[variable] = overwrite


def generate_context(context_file='cookiecutter.json', default_context=None,
                     extra_context=None):
    """Generate the context for a Cookiecutter project template.

    Loads the JSON file as a Python object, with key being the JSON filename.

    :param context_file: JSON file containing key/value pairs for populating
        the cookiecutter's variables.
    :param default_context: Dictionary containing config to take into account.
    :param extra_context: Dictionary containing configuration overrides
    """
    context = {}

    try:
        with open(context_file) as file_handle:
            obj = json.load(file_handle, object_pairs_hook=OrderedDict)
    except ValueError as e:
        # JSON decoding error.  Let's throw a new exception that is more
        # friendly for the developer or user.
        full_fpath = os.path.abspath(context_file)
        json_exc_message = str(e)
        our_exc_message = (
            'JSON decoding error while loading "{0}".  Decoding'
            ' error details: "{1}"'.format(full_fpath, json_exc_message))
        raise ContextDecodingException(our_exc_message)

    # Add the Python object to the context dictionary
    file_name = os.path.split(context_file)[1]
    file_stem = file_name.split('.')[0]
    context[file_stem] = obj

    # Overwrite context variable defaults with the default context from the
    # user's global config, if available
    if default_context:
        apply_overwrites_to_context(obj, default_context)
    if extra_context:
        apply_overwrites_to_context(obj, extra_context)

    logger.debug('Context generated is {}'.format(context))
    return context


def generate_file(project_dir, infile, context, env):
    """Render filename of infile as name of outfile, handle infile correctly.

    Dealing with infile appropriately:

        a. If infile is a binary file, copy it over without rendering.
        b. If infile is a text file, render its contents and write the
           rendered infile to outfile.

    Precondition:

        When calling `generate_file()`, the root template dir must be the
        current working directory. Using `utils.work_in()` is the recommended
        way to perform this directory change.

    :param project_dir: Absolute path to the resulting generated project.
    :param infile: Input file to generate the file from. Relative to the root
        template dir.
    :param context: Dict for populating the cookiecutter's variables.
    :param env: Jinja2 template execution environment.
    """
    logger.debug('Processing file {}'.format(infile))

    # Render the path to the output file (not including the root project dir)
    outfile_tmpl = env.from_string(infile)

    outfile = os.path.join(project_dir, outfile_tmpl.render(**context))
    file_name_is_empty = os.path.isdir(outfile)
    if file_name_is_empty:
        logger.debug('The resulting file name is empty: {0}'.format(outfile))
        return

    logger.debug('Created file at {0}'.format(outfile))

    # Just copy over binary files. Don't render.
    logger.debug("Check {} to see if it's a binary".format(infile))
    if is_binary(infile):
        logger.debug(
            'Copying binary {} to {} without rendering'
            ''.format(infile, outfile)
        )
        shutil.copyfile(infile, outfile)
    else:
        # Force fwd slashes on Windows for get_template
        # This is a by-design Jinja issue
        infile_fwd_slashes = infile.replace(os.path.sep, '/')

        # Render the file
        try:
            tmpl = env.get_template(infile_fwd_slashes)
        except TemplateSyntaxError as exception:
            # Disable translated so that printed exception contains verbose
            # information about syntax error location
            exception.translated = False
            raise
        rendered_file = tmpl.render(**context)

        logger.debug('Writing contents to file {}'.format(outfile))

        with io.open(outfile, 'w', encoding='utf-8') as fh:
            fh.write(rendered_file)

    # Apply file permissions to output file
    shutil.copymode(infile, outfile)


def render_and_create_dir(dirname, context, output_dir, environment,
                          overwrite_if_exists=False):
    """Render name of a directory, create the directory, return its path."""
    name_tmpl = environment.from_string(dirname)
    rendered_dirname = name_tmpl.render(**context)

    dir_to_create = os.path.normpath(
        os.path.join(output_dir, rendered_dirname)
    )

    logger.debug('Rendered dir {} must exist in output_dir {}'.format(
        dir_to_create,
        output_dir
    ))

    output_dir_exists = os.path.exists(dir_to_create)

    if overwrite_if_exists:
        if output_dir_exists:
            logger.debug(
                'Output directory {} already exists,'
                'overwriting it'.format(dir_to_create)
            )
    else:
        if output_dir_exists:
            msg = 'Error: "{}" directory already exists'.format(dir_to_create)
            raise OutputDirExistsException(msg)

    make_sure_path_exists(dir_to_create)
    return dir_to_create


def ensure_dir_is_templated(dirname):
    """Ensure that dirname is a templated directory name."""
    if '{{' in dirname and '}}' in dirname:
        return True
    else:
        raise NonTemplatedInputDirException


def _run_hook_from_repo_dir(repo_dir, hook_name, project_dir, context):
    """Run hook from repo directory, clean project directory if hook fails.

    :param repo_dir: Project template input directory.
    :param hook_name: The hook to execute.
    :param project_dir: The directory to execute the script from.
    :param context: Cookiecutter project context.
    """
    with work_in(repo_dir):
        try:
            run_hook(hook_name, project_dir, context)
        except FailedHookException:
            rmtree(project_dir)
            logger.error(
                "Stopping generation because {} hook "
                "script didn't exit successfully".format(hook_name)
            )
            raise


def generate_files(repo_dir, context=None, output_dir='.',
                   overwrite_if_exists=False):
    """Render the templates and saves them to files.

    :param repo_dir: Project template input directory.
    :param context: Dict for populating the template's variables.
    :param output_dir: Where to output the generated project dir into.
    :param overwrite_if_exists: Overwrite the contents of the output directory
        if it exists.
    """
    template_dir = find_template(repo_dir)
    logger.debug('Generating project from {}...'.format(template_dir))
    context = context or {}

    unrendered_dir = os.path.split(template_dir)[1]
    ensure_dir_is_templated(unrendered_dir)
    env = StrictEnvironment(
        context=context,
        keep_trailing_newline=True,
    )
    try:
        project_dir = render_and_create_dir(
            unrendered_dir,
            context,
            output_dir,
            env,
            overwrite_if_exists
        )
    except UndefinedError as err:
        msg = "Unable to create project directory '{}'".format(unrendered_dir)
        raise UndefinedVariableInTemplate(msg, err, context)

    # We want the Jinja path and the OS paths to match. Consequently, we'll:
    #   + CD to the template folder
    #   + Set Jinja's path to '.'
    #
    #  In order to build our files to the correct folder(s), we'll use an
    # absolute path for the target folder (project_dir)

    project_dir = os.path.abspath(project_dir)
    logger.debug('Project directory is {}'.format(project_dir))

    _run_hook_from_repo_dir(repo_dir, 'pre_gen_project', project_dir, context)

    with work_in(template_dir):
        env.loader = FileSystemLoader('.')

        for root, dirs, files in os.walk('.'):
            # We must separate the two types of dirs into different lists.
            # The reason is that we don't want ``os.walk`` to go through the
            # unrendered directories, since they will just be copied.
            copy_dirs = []
            render_dirs = []

            for d in dirs:
                d_ = os.path.normpath(os.path.join(root, d))
                # We check the full path, because that's how it can be
                # specified in the ``_copy_without_render`` setting, but
                # we store just the dir name
                if is_copy_only_path(d_, context):
                    copy_dirs.append(d)
                else:
                    render_dirs.append(d)

            for copy_dir in copy_dirs:
                indir = os.path.normpath(os.path.join(root, copy_dir))
                outdir = os.path.normpath(os.path.join(project_dir, indir))
                logger.debug(
                    'Copying dir {} to {} without rendering'
                    ''.format(indir, outdir)
                )
                shutil.copytree(indir, outdir)

            # We mutate ``dirs``, because we only want to go through these dirs
            # recursively
            dirs[:] = render_dirs
            for d in dirs:
                unrendered_dir = os.path.join(project_dir, root, d)
                try:
                    render_and_create_dir(
                        unrendered_dir,
                        context,
                        output_dir,
                        env,
                        overwrite_if_exists
                    )
                except UndefinedError as err:
                    rmtree(project_dir)
                    _dir = os.path.relpath(unrendered_dir, output_dir)
                    msg = "Unable to create directory '{}'".format(_dir)
                    raise UndefinedVariableInTemplate(msg, err, context)

            for f in files:
                infile = os.path.normpath(os.path.join(root, f))
                if is_copy_only_path(infile, context):
                    outfile_tmpl = env.from_string(infile)
                    outfile_rendered = outfile_tmpl.render(**context)
                    outfile = os.path.join(project_dir, outfile_rendered)
                    logger.debug(
                        'Copying file {} to {} without rendering'
                        ''.format(infile, outfile)
                    )
                    shutil.copyfile(infile, outfile)
                    shutil.copymode(infile, outfile)
                    continue
                try:
                    generate_file(project_dir, infile, context, env)
                except UndefinedError as err:
                    rmtree(project_dir)
                    msg = "Unable to create file '{}'".format(infile)
                    raise UndefinedVariableInTemplate(msg, err, context)

    _run_hook_from_repo_dir(repo_dir, 'post_gen_project', project_dir, context)

    return project_dir
