# Copyright 2014 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

import os


class PythonRequirements:
    """Translates a pip requirements file into an equivalent set of python_requirements.

    If the ``requirements.txt`` file has lines ``foo>=3.14`` and ``bar>=2.7``,
    then this is roughly like::

      python_requirement_library(name="foo", requirements=[
        python_requirement("foo>=3.14"),
      ])
      python_requirement_library(name="bar", requirements=[
        python_requirement("bar>=2.7"),
      ])

    NB some requirements files can't be unambiguously translated; ie: multiple
    find links.  For these files a ValueError will be raised that points out the issue.

    See the requirements file spec here:
    https://pip.pypa.io/en/latest/reference/pip_install.html#requirements-file-format
    """

    def __init__(self, parse_context):
        self._parse_context = parse_context

    def __call__(self, requirements_relpath="requirements.txt"):
        """
        :param string requirements_relpath: The relpath from this BUILD file to the requirements file.
        Defaults to a `requirements.txt` file sibling to the BUILD file.
        """

        requirements = []
        repository = None

        requirements_path = os.path.join(self._parse_context.rel_path, requirements_relpath)
        with open(requirements_path, "r") as fp:
            for line in fp:
                line = line.strip()
                if line and not line.startswith("#"):
                    if not line.startswith("-"):
                        requirements.append(line)
                    else:
                        # handle flags we know about
                        flag_value = line.split(" ", 1)
                        if len(flag_value) == 2:
                            flag = flag_value[0].strip()
                            value = flag_value[1].strip()
                            if flag in ("-f", "--find-links"):
                                if repository is not None:
                                    raise ValueError(
                                        "Only 1 --find-links url is supported per requirements file"
                                    )
                                repository = value

        requirements_file_target_name = requirements_relpath
        self._parse_context.create_object(
            "files", name=requirements_file_target_name, sources=[requirements_relpath]
        )
        requirements_dep = ":{}".format(requirements_file_target_name)

        for requirement in requirements:
            req = self._parse_context.create_object(
                "python_requirement", requirement, repository=repository
            )
            self._parse_context.create_object(
                "python_requirement_library",
                name=req.project_name,
                requirements=[req],
                dependencies=[requirements_dep],
            )