"""For parsing code snippets and locating relevant dependencies/imports so that they could be installed to the containers' images"""

from contextlib import contextmanager
import os
import sys
import re
import logging
import ast
from docopt import docopt
import requests
from pathlib import Path
from yarg import json2package
from yarg.exceptions import HTTPError

REGEXP = [
    re.compile(r'^import (.+)$'),
    re.compile(r'^from ((?!\.+).*?) import (?:.*)$')
]

logging.disable(sys.maxsize)
PIPS_FOLDER_PATH = os.path.join(os.path.dirname(Path(os.path.realpath(__file__)).parent), "pips")
DOCKER_REQUIREMENTS_PATH = os.path.join(os.path.dirname(Path(os.path.realpath(__file__)).parent.parent), "docker/docker/requirements.txt")

@contextmanager
def _open(filename=None, mode='r'):
    """Open a file or ``sys.stdout`` depending on the provided filename.

    Args:
        filename (str): The path to the file that should be opened. If
            ``None`` or ``'-'``, ``sys.stdout`` or ``sys.stdin`` is
            returned depending on the desired mode. Defaults to ``None``.
        mode (str): The mode that should be used to open the file.

    Yields:
        A file handle.

    """
    if not filename or filename == '-':
        if not mode or 'r' in mode:
            file = sys.stdin
        elif 'w' in mode:
            file = sys.stdout
        else:
            raise ValueError('Invalid mode for file: {}'.format(mode))
    else:
        file = open(filename, mode)

    try:
        yield file
    finally:
        if file not in (sys.stdin, sys.stdout):
            file.close()


def get_all_imports(
        contents):
    imports = set()
    raw_imports = set()
    candidates = []
    ignore_errors = False

    tree = ast.parse(contents)
    for node in ast.walk(tree):
        if isinstance(node, ast.Import):
            for subnode in node.names:
                raw_imports.add(subnode.name)
        elif isinstance(node, ast.ImportFrom):
            raw_imports.add(node.module)

    # Clean up imports
    for name in [n for n in raw_imports if n]:
        # Sanity check: Name could have been None if the import
        # statement was as ``from . import X``
        # Cleanup: We only want to first part of the import.
        # Ex: from django.conf --> django.conf. But we only want django
        # as an import.
        cleaned_name, _, _ = name.partition('.')
        imports.add(cleaned_name)

    packages = imports - (set(candidates) & imports)
    logging.debug('Found packages: {0}'.format(packages))

    with open(os.path.join(PIPS_FOLDER_PATH, "stdlib.txt"), "r") as f:
        data = {x.strip() for x in f}

    return list(packages - data)


def generate_requirements_file(path, imports, symbol):
    with _open(path, "w") as out_file:
        logging.debug('Writing {num} requirements: {imports} to {file}'.format(
            num=len(imports),
            file=path,
            imports=", ".join([x['name'] for x in imports])
        ))
        fmt = '{name}' + symbol + '{version}'
        out_file.write('\n'.join(
            fmt.format(**item) if item['version'] else '{name}'.format(**item)
            for item in imports) + '\n')


def get_imports_info(
        imports, pypi_server="https://pypi.python.org/pypi/", proxy=None):
    result = []

    # transformers most times require torch and sentencepiece
    if ('transformers' in imports):
        imports.extend(['torch', 'sentencepiece'])

    for item in imports:
        try:
            logging.warning(
                'Import named "%s" not found locally. '
                'Trying to resolve it at the PyPI server.',
                item
            )
            response = requests.get(
                "{0}{1}/json".format(pypi_server, item), proxies=proxy)
            if response.status_code == 200:
                if hasattr(response.content, 'decode'):
                    data = json2package(response.content.decode())
                else:
                    data = json2package(response.content)
            elif response.status_code >= 300:
                raise HTTPError(status_code=response.status_code,
                                reason=response.reason)
        except HTTPError:
            logging.warning(
                'Package "%s" does not exist or network problems', item)
            continue
        logging.warning(
            'Import named "%s" was resolved to "%s:%s" package (%s).\n'
            'Please, verify manually the final list of requirements.txt '
            'to avoid possible dependency confusions.',
            item,
            data.name,
            data.latest_release_id,
            data.pypi_url
        )
        result.append({'name': item, 'version': data.latest_release_id})
    return result


def get_locally_installed_packages(encoding=None):
    packages = []
    ignore = ["tests", "_tests", "egg", "EGG", "info"]
    for path in sys.path:
        for root, dirs, files in os.walk(path):
            for item in files:
                if "top_level" in item:
                    item = os.path.join(root, item)
                    with open(item, "r", encoding=encoding) as f:
                        package = root.split(os.sep)[-1].split("-")
                        try:
                            top_level_modules = f.read().strip().split("\n")
                        except:  # NOQA
                            # TODO: What errors do we intend to suppress here?
                            continue

                        # filter off explicitly ignored top-level modules
                        # such as test, egg, etc.
                        filtered_top_level_modules = list()

                        for module in top_level_modules:
                            if (
                                (module not in ignore) and
                                (package[0] not in ignore)
                            ):
                                # append exported top level modules to the list
                                filtered_top_level_modules.append(module)

                        version = None
                        if len(package) > 1:
                            version = package[1].replace(
                                ".dist", "").replace(".egg", "")

                        # append package: top_level_modules pairs
                        # instead of top_level_module: package pairs
                        packages.append({
                            'name': package[0],
                            'version': version,
                            'exports': filtered_top_level_modules
                        })
    return packages


def get_import_local(imports, encoding=None):
    local = get_locally_installed_packages()
    result = []
    if ('transformers' in imports):
        imports.extend(['torch', 'sentencepiece'])
    for item in imports:
        # search through local packages
        for package in local:
            # if candidate import name matches export name
            # or candidate import name equals to the package name
            # append it to the result
            if item in package['exports'] or item == package['name']:
                result.append(package)

    # removing duplicates of package/version
    # had to use second method instead of the previous one,
    # because we have a list in the 'exports' field
    # https://stackoverflow.com/questions/9427163/remove-duplicate-dict-in-list-in-python
    name_set = set()
    result_unique = []
    for n, i in enumerate(result):
        if i['name'] not in name_set:
            result_unique.append(i)
            name_set.add(i['name'])

    #result_unique = [i for n, i in enumerate(result) if i not in result[n+1:]]

    return result_unique


def get_pkg_names(pkgs):
    """Get PyPI package names from a list of imports.

    Args:
        pkgs (List[str]): List of import names.

    Returns:
        List[str]: The corresponding PyPI package names.

    """
    result = set()
    with open(os.path.join(PIPS_FOLDER_PATH, "mapping.txt"), "r") as f:
        data = dict(x.strip().split(":") for x in f)
    for pkg in pkgs:
        # Look up the mapped requirement. If a mapping isn't found,
        # simply use the package name.
        result.add(data.get(pkg, pkg))
    # Return a sorted list for backward compatibility.
    return sorted(result, key=lambda s: s.lower())


def get_name_without_alias(name):
    if "import " in name:
        match = REGEXP[0].match(name.strip())
        if match:
            name = match.groups(0)[0]
    return name.partition(' as ')[0].partition('.')[0].strip()


def join(f):
    return os.path.join(os.path.dirname(__file__), f)


def parse_requirements(file_):
    """Parse a requirements formatted file.

    Traverse a string until a delimiter is detected, then split at said
    delimiter, get module name by element index, create a dict consisting of
    module:version, and add dict to list of parsed modules.

    Args:
        file_: File to parse.

    Raises:
        OSerror: If there's any issues accessing the file.

    Returns:
        tuple: The contents of the file, excluding comments.
    """
    modules = []
    # For the dependency identifier specification, see
    # https://www.python.org/dev/peps/pep-0508/#complete-grammar
    delim = ["<", ">", "=", "!", "~"]

    try:
        f = open(file_, "r")
    except OSError:
        logging.error("Failed on file: {}".format(file_))
        raise
    else:
        try:
            data = [x.strip() for x in f.readlines() if x != "\n"]
        finally:
            f.close()

    data = [x for x in data if x[0].isalpha()]

    for x in data:
        # Check for modules w/o a specifier.
        if not any([y in x for y in delim]):
            modules.append({"name": x, "version": None})
        for y in x:
            if y in delim:
                module = x.split(y)
                module_name = module[0]
                module_version = module[-1].replace("=", "")
                module = {"name": module_name, "version": module_version}

                if module not in modules:
                    modules.append(module)

                break

    return modules


def compare_modules(file_, imports):
    """Compare modules in a file to imported modules in a project.

    Args:
        file_ (str): File to parse for modules to be compared.
        imports (tuple): Modules being imported in the project.

    Returns:
        tuple: The modules not imported in the project, but do exist in the
               specified file.
    """
    modules = parse_requirements(file_)

    imports = [imports[i]["name"] for i in range(len(imports))]
    modules = [modules[i]["name"] for i in range(len(modules))]
    modules_not_imported = set(modules) - set(imports)

    return modules_not_imported


def diff(file_, imports):
    """Display the difference between modules in a file and imported modules."""  # NOQA
    modules_not_imported = compare_modules(file_, imports)

    logging.info(
        "The following modules are in {} but do not seem to be imported: "
        "{}".format(file_, ", ".join(x for x in modules_not_imported)))


def clean(file_, imports):
    """Remove modules that aren't imported in project from file."""
    modules_not_imported = compare_modules(file_, imports)

    if len(modules_not_imported) == 0:
        logging.info("Nothing to clean in " + file_)
        return

    re_remove = re.compile("|".join(modules_not_imported))
    to_write = []

    try:
        f = open(file_, "r+")
    except OSError:
        logging.error("Failed on file: {}".format(file_))
        raise
    else:
        try:
            for i in f.readlines():
                if re_remove.match(i) is None:
                    to_write.append(i)
            f.seek(0)
            f.truncate()

            for i in to_write:
                f.write(i)
        finally:
            f.close()

    logging.info("Successfully cleaned up requirements in " + file_)


def dynamic_versioning(scheme, imports):
    """Enables dynamic versioning with <compat>, <gt> or <non-pin> schemes."""
    if scheme == "no-pin":
        imports = [{"name": item["name"], "version": ""} for item in imports]
        symbol = ""
    elif scheme == "gt":
        symbol = ">="
    elif scheme == "compat":
        symbol = "~="
    return imports, symbol


def extract_dependencies(contents, args = {}, path = DOCKER_REQUIREMENTS_PATH):
    candidates = get_all_imports(contents)
    candidates = get_pkg_names(candidates)
    logging.debug("Found imports: " + ", ".join(candidates))
    pypi_server = "https://pypi.python.org/pypi/"
    proxy = None
    logging.debug("Getting packages information from Local/PyPI")
    local = get_import_local(candidates, encoding=None)

    #commonly used enough to be worth adding
    candidates.append('pickle')
    # check if candidate name is found in
    # the list of exported modules, installed locally
    # and the package name is not in the list of local module names
    # it add to difference
    difference = [x for x in candidates if
                    # aggregate all export lists into one
                    # flatten the list
                    # check if candidate is in exports
                    x.lower() not in [y for x in local for y in x['exports']]
                    and
                    # check if candidate is package names
                    x.lower() not in [x['name'] for x in local]]
    imports = local + get_imports_info(difference,
                                        proxy=proxy,
                                        pypi_server=pypi_server)
    # sort imports based on lowercase name of package, similar to `pip freeze`.
    imports = sorted(imports, key=lambda x: x['name'].lower())
    generate_requirements_file(path, imports, "==")
    logging.info("Successfully saved requirements file in " + path)
    return imports