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

from contextlib import closing
from io import BytesIO


class Manifest:
    """Implements the basics of the jar manifest specification.

    See: http://docs.oracle.com/javase/1.5.0/docs/guide/jar/jar.html#Manifest Specification
    """

    @staticmethod
    def _wrap(text):
        text = text.encode("ascii")
        with closing(BytesIO(text)) as fp:
            yield fp.read(70)
            while True:
                chunk = fp.read(69)
                if not chunk:
                    return
                yield b" " + chunk

    PATH = "META-INF/MANIFEST.MF"

    MANIFEST_VERSION = "Manifest-Version"
    CREATED_BY = "Created-By"
    MAIN_CLASS = "Main-Class"
    CLASS_PATH = "Class-Path"

    def __init__(self, contents=""):
        self._contents = contents.strip().encode("ascii")

    def addentry(self, header, value):
        if len(header) > 68:
            raise ValueError("Header name must be 68 characters or less, given {}".format(header))
        if self._contents:
            self._contents += b"\n"
        self._contents += b"\n".join(
            self._wrap("{header}: {value}".format(header=header, value=value))
        )

    def contents(self):
        return self._contents + b"\n"

    def is_empty(self):
        if self._contents.strip():
            return False
        return True