#!/usr/bin/env python3

import argparse
import datetime
import os
import re
from typing import NamedTuple

import debian.changelog


def parse_arguments():
    parser = argparse.ArgumentParser(description="automatic changelog writer for snapd")
    parser.add_argument("version", type=str, help="new snapd version")
    parser.add_argument(
        "changelog",
        type=argparse.FileType("r"),
        help="path to new changelog entry as generated by snappy-dch",
    )
    return parser.parse_args()


class Distro(NamedTuple):
    name: str  # name of the distro in the packaging directory
    debian_name: str  # debian distribution name
    version_suffix: str  # suffix to add to the version number in changelogs


debianish_distros = [
    Distro("ubuntu-14.04", "trusty", "~14.04"),
    Distro("ubuntu-16.04", "xenial", ""),
    Distro("debian-sid", "unstable", "-1"),
]


other_distros = [
    "opensuse",
    "fedora",
    "arch",
]


def rewrite_version_number_file(file_name, pattern, version, write):
    """rewrite_version_number_file reads a packaging file with a version number
    in it and updates the version number to the new one specified using the
    regex pattern.
    It returns the new file contents and optionally writes out the new contents
    back to the file as well.
    """

    with open(file_name, "r") as fh:
        file_contents = fh.read()

    # replace the pattern (which should have one capturing group in it for the
    # version specifier pattern) with the captured group + the new version such
    # that we can keep any whitespace, etc in between the version specified and
    # the version number
    new_contents, n = re.subn(
        pattern, r"\g<1>" + version, file_contents, flags=re.MULTILINE
    )

    # check that we only did one replacement in the file
    if n > 1:
        raise RuntimeError(
            f"too many version patterns ({n}) matched in packaging file {file_name}"
        )
    elif n < 1:
        raise RuntimeError(f"version pattern not matched in packaging file {file_name}")

    if write is True:
        with open(file_name, "w") as fh:
            fh.write(new_contents)

    return new_contents


def update_fedora_changelog(opts, snapd_packaging_dir, new_changelog_entry, maintainer):
    spec_file = os.path.join(snapd_packaging_dir, "fedora", "snapd.spec")

    # rewrite the snapd.spec file with the right version
    spec_file_content = rewrite_version_number_file(
        spec_file,
        r"^(Version:\s+).*$",
        opts.version,
        False,
    )

    # now we also need to add the changelog entry to the snapd.spec file
    # this is a bit tricky, since we want a different format for the
    # changelog in snapd.spec than we have for debian, but luckily it's
    # just trimming whitespace off the front of each line in the
    # changelog

    dedented_changelog_lines = []
    for line in new_changelog_entry.splitlines():
        # strip the first 3 characters which are space characters so
        # that we only have one single whitespace
        dedented_changelog_lines.append(line[3:] + "\n")

    date = datetime.datetime.now().strftime("%a %d %b %Y")

    date_and_maintainer_header = f"* {date} {maintainer[0]} <{maintainer[1]}>\n"
    changelog_header = f"- New upstream release {opts.version}\n"
    fedora_changelog_lines = [
        date_and_maintainer_header,
        changelog_header,
    ] + dedented_changelog_lines

    # find the start of the changelog section in the rewritten spec file bytes
    changelog_section = "\n%changelog\n"
    idx = spec_file_content.find(changelog_section)
    if idx < 0:
        raise RuntimeError(
            "'%changelog' line in fedora spec file not found (was a comment or whitespace added to that line?)"
        )
    # rewrite the spec file using the replaced bits up to the changelog section,
    # then insert our new changelog entry lines, then add the rest of the
    # replaced bits of the spec file
    with open(spec_file, "w") as fh:
        # write the spec file up to and including the changelog section
        fh.write(spec_file_content[: idx + len(changelog_section)])
        # insert our new changelog entry
        for ch_line in fedora_changelog_lines:
            fh.write(ch_line)
        fh.write("\n")
        # write the rest of the original spec file
        fh.write(spec_file_content[idx + len(changelog_section) :])


def update_opensuse_changlog(
    opts, snapd_packaging_dir, new_changelog_entry, maintainer
):
    spec_file = os.path.join(snapd_packaging_dir, "opensuse", "snapd.spec")
    changes_file = os.path.join(snapd_packaging_dir, "opensuse", "snapd.changes")

    rewrite_version_number_file(
        spec_file,
        r"^(Version:\s+).*$",
        opts.version,
        True,
    )

    # add a template changelog to the changes file
    date = datetime.datetime.now().strftime("%a, %d %b %Y %H:%M:%S %z")

    email = maintainer[1]
    templ = f"""-------------------------------------------------------------------
{date} - {email}

- Update to upstream release {opts.version}

"""

    # read the existing changes file and then write the new changelog entry at
    # the top and then write the rest of the file
    with open(changes_file, "r") as fh:
        current = fh.read()
    with open(changes_file, "w") as fh:
        fh.write(templ)
        fh.write(current)


def main(opts):
    this_script = os.path.realpath(__file__)
    snapd_root_git_dir = os.path.dirname(os.path.dirname(this_script))
    snapd_packaging_dir = os.path.join(snapd_root_git_dir, "packaging")

    # read all the changelog entries, expected to be formatted by snappy-dch
    new_changelog_entry = opts.changelog.read()

    # verify that the changelog entry lines are all in the right format
    for line_number, line in enumerate(new_changelog_entry.splitlines(), start=1):
        # each line should start with either 4 spaces, a - and then another
        # space, or 6 spaces
        if not line.startswith("    - ") and not line.startswith("      "):
            raise RuntimeError(
                f"unexpected changelog line format in line {line_number}"
            )
        if len(line) >= 72:
            raise RuntimeError(
                f"line {line_number} too long, should wrap properly to next line"
            )

    # read the name and email of the person running the script using i.e. dch
    # conventions
    maintainer = debian.changelog.get_maintainer()

    # first handle all of the debian packaging files
    for distro in debianish_distros:
        debian_packaging_changelog = os.path.join(
            snapd_packaging_dir, distro.name, "changelog"
        )
        with open(debian_packaging_changelog) as fh:
            ch = debian.changelog.Changelog(fh)

        # setup a new block
        ch.new_block(
            package="snapd",
            version=opts.version + distro.version_suffix,
            distributions=distro.debian_name,
            urgency="medium",
            author=f"{maintainer[0]} <{maintainer[1]}>",
            date=debian.changelog.format_date(),
        )

        # add the new changelog entry with our standard header
        # the spacing here is manually adjusted, the top of the comment is always
        # the same
        templ = "\n  * New upstream release, LP: #1926005\n" + new_changelog_entry
        ch.add_change(templ)

        # write it out back to the changelog file
        with open(debian_packaging_changelog, "w") as fh:
            ch.write_to_open_file(fh)

    # now handle all of the non-debian packaging files
    for distro in other_distros:
        if distro == "arch":
            # for arch all we need to do is change the PKGBUILD "pkgver" key
            rewrite_version_number_file(
                os.path.join(snapd_packaging_dir, "arch", "PKGBUILD"),
                r"^(pkgver=).*$",
                opts.version,
                True,
            )
        elif distro == "fedora":
            update_fedora_changelog(
                opts, snapd_packaging_dir, new_changelog_entry, maintainer
            )

        elif distro == "opensuse":
            update_opensuse_changlog(
                opts, snapd_packaging_dir, new_changelog_entry, maintainer
            )


if __name__ == "__main__":
    opts = parse_arguments()
    main(opts)
