def plus_or_dot(pieces):
    """Return a + if we don't already have one, else return a ."""
    if "+" in pieces.get("closest-tag", ""):
        return "."
    return "+"


def render_pep440(pieces):
    """Build up version string, with post-release "local version identifier".

    Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
    get a tagged build and then dirty it, you'll get TAG+0.gHEX.dirty

    Exceptions:
    1: no tags. git_describe was just HEX. 0+untagged.DISTANCE.gHEX[.dirty]
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        if pieces["distance"] or pieces["dirty"]:
            rendered += plus_or_dot(pieces)
            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
            if pieces["dirty"]:
                rendered += ".dirty"
    else:
        # exception #1
        rendered = "0+untagged.%d.g%s" % (pieces["distance"],
                                          pieces["short"])
        if pieces["dirty"]:
            rendered += ".dirty"
    return rendered


def render_pep440_branch(pieces):
    """TAG[[.dev0]+DISTANCE.gHEX[.dirty]] .

    The ".dev0" means not master branch. Note that .dev0 sorts backwards
    (a feature branch will appear "older" than the master branch).

    Exceptions:
    1: no tags. 0[.dev0]+untagged.DISTANCE.gHEX[.dirty]
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        if pieces["distance"] or pieces["dirty"]:
            if pieces["branch"] != "master":
                rendered += ".dev0"
            rendered += plus_or_dot(pieces)
            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
            if pieces["dirty"]:
                rendered += ".dirty"
    else:
        # exception #1
        rendered = "0"
        if pieces["branch"] != "master":
            rendered += ".dev0"
        rendered += "+untagged.%d.g%s" % (pieces["distance"],
                                          pieces["short"])
        if pieces["dirty"]:
            rendered += ".dirty"
    return rendered


def pep440_split_post(ver):
    """Split pep440 version string at the post-release segment.

    Returns the release segments before the post-release and the
    post-release version number (or -1 if no post-release segment is present).
    """
    vc = str.split(ver, ".post")
    return vc[0], int(vc[1] or 0) if len(vc) == 2 else None


def render_pep440_pre(pieces):
    """TAG[.postN.devDISTANCE] -- No -dirty.

    Exceptions:
    1: no tags. 0.post0.devDISTANCE
    """
    if pieces["closest-tag"]:
        if pieces["distance"]:
            # update the post release segment
            tag_version, post_version = pep440_split_post(pieces["closest-tag"])
            rendered = tag_version
            if post_version is not None:
                rendered += ".post%d.dev%d" % (post_version + 1, pieces["distance"])
            else:
                rendered += ".post0.dev%d" % (pieces["distance"])
        else:
            # no commits, use the tag as the version
            rendered = pieces["closest-tag"]
    else:
        # exception #1
        rendered = "0.post0.dev%d" % pieces["distance"]
    return rendered


def render_pep440_post(pieces):
    """TAG[.postDISTANCE[.dev0]+gHEX] .

    The ".dev0" means dirty. Note that .dev0 sorts backwards
    (a dirty tree will appear "older" than the corresponding clean one),
    but you shouldn't be releasing software with -dirty anyways.

    Exceptions:
    1: no tags. 0.postDISTANCE[.dev0]
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        if pieces["distance"] or pieces["dirty"]:
            rendered += ".post%d" % pieces["distance"]
            if pieces["dirty"]:
                rendered += ".dev0"
            rendered += plus_or_dot(pieces)
            rendered += "g%s" % pieces["short"]
    else:
        # exception #1
        rendered = "0.post%d" % pieces["distance"]
        if pieces["dirty"]:
            rendered += ".dev0"
        rendered += "+g%s" % pieces["short"]
    return rendered


def render_pep440_post_branch(pieces):
    """TAG[.postDISTANCE[.dev0]+gHEX[.dirty]] .

    The ".dev0" means not master branch.

    Exceptions:
    1: no tags. 0.postDISTANCE[.dev0]+gHEX[.dirty]
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        if pieces["distance"] or pieces["dirty"]:
            rendered += ".post%d" % pieces["distance"]
            if pieces["branch"] != "master":
                rendered += ".dev0"
            rendered += plus_or_dot(pieces)
            rendered += "g%s" % pieces["short"]
            if pieces["dirty"]:
                rendered += ".dirty"
    else:
        # exception #1
        rendered = "0.post%d" % pieces["distance"]
        if pieces["branch"] != "master":
            rendered += ".dev0"
        rendered += "+g%s" % pieces["short"]
        if pieces["dirty"]:
            rendered += ".dirty"
    return rendered


def render_pep440_old(pieces):
    """TAG[.postDISTANCE[.dev0]] .

    The ".dev0" means dirty.

    Exceptions:
    1: no tags. 0.postDISTANCE[.dev0]
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        if pieces["distance"] or pieces["dirty"]:
            rendered += ".post%d" % pieces["distance"]
            if pieces["dirty"]:
                rendered += ".dev0"
    else:
        # exception #1
        rendered = "0.post%d" % pieces["distance"]
        if pieces["dirty"]:
            rendered += ".dev0"
    return rendered


def render_git_describe(pieces):
    """TAG[-DISTANCE-gHEX][-dirty].

    Like 'git describe --tags --dirty --always'.

    Exceptions:
    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        if pieces["distance"]:
            rendered += "-%d-g%s" % (pieces["distance"], pieces["short"])
    else:
        # exception #1
        rendered = pieces["short"]
    if pieces["dirty"]:
        rendered += "-dirty"
    return rendered


def render_git_describe_long(pieces):
    """TAG-DISTANCE-gHEX[-dirty].

    Like 'git describe --tags --dirty --always -long'.
    The distance/hash is unconditional.

    Exceptions:
    1: no tags. HEX[-dirty]  (note: no 'g' prefix)
    """
    if pieces["closest-tag"]:
        rendered = pieces["closest-tag"]
        rendered += "-%d-g%s" % (pieces["distance"], pieces["short"])
    else:
        # exception #1
        rendered = pieces["short"]
    if pieces["dirty"]:
        rendered += "-dirty"
    return rendered


def render(pieces, style):
    """Render the given version pieces into the requested style."""
    if pieces["error"]:
        return {"version": "unknown",
                "full-revisionid": pieces.get("long"),
                "dirty": None,
                "error": pieces["error"],
                "date": None}

    if not style or style == "default":
        style = "pep440"  # the default

    if style == "pep440":
        rendered = render_pep440(pieces)
    elif style == "pep440-branch":
        rendered = render_pep440_branch(pieces)
    elif style == "pep440-pre":
        rendered = render_pep440_pre(pieces)
    elif style == "pep440-post":
        rendered = render_pep440_post(pieces)
    elif style == "pep440-post-branch":
        rendered = render_pep440_post_branch(pieces)
    elif style == "pep440-old":
        rendered = render_pep440_old(pieces)
    elif style == "git-describe":
        rendered = render_git_describe(pieces)
    elif style == "git-describe-long":
        rendered = render_git_describe_long(pieces)
    else:
        raise ValueError("unknown style '%s'" % style)

    return {"version": rendered, "full-revisionid": pieces["long"],
            "dirty": pieces["dirty"], "error": None,
            "date": pieces.get("date")}