#!/usr/bin/env python3

# Copyright 2024 Bryan Gardiner <bog@khumba.net>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.


# Imports issues from an exported Gitlab project into a Sourcehut tracker.
#
# Reads *.ndjson files from an exported Gitlab project, and recreates tickets
# and their histories in a new, empty Sourcehut tracker.  Preserves notes
# attached to each issue; generally this includes comments, status changes,
# labels, milestones, and anything else that is included in as a plain text
# note, but definitely doesn't include all available metadata.
#
# Tickets are created in sr.ht via SMTP, so a working mail setup is required.
# Surely using Sourcehut's API would be better.
#
# There are a few caveats:
#
# 1. If all issue IDs from 1 to the max ID are available in your export, and the
# tracker you import into is a new tracker, then your Gitlab and Sourcehut issue
# IDs will match up one-to-one, and mentions of one ticket from another will
# work.  If not, you need to decide how you want to handle this.  You can choose
# to create empty Sourcehut tickets for the missing Gitlab issues so that IDs
# still match, by passing --create-missing-issues.  Blank issues will be created
# then closed.  Alternatively, you can pass --skip-missing-issues to not create
# any extra Sourcehut tickets, but IDs will not line up.  If one of these issues
# is needed, this program will tell you.
#
# 2. Because emails are used to create tickets, we also assume that emails are
# processed in the order that they are sent, so that tickets don't get created
# out of order.  This program has no way of knowing if that happens, however,
# there is a configurable delay between sending each email, for this reason.
#
# 3. Gitlab project exports are missing some crucial information, in particular
# they don't include ticket author names or label IDs.  For best results,
# appropriate mappings for your project can be filled in manually in the LABELS
# and USERS dicts below, if desired, or these features can be disabled.  See the
# documentation for these variables.
#
# 4. If your project has confidential issues or comments in it, then you will
# need to decide to exclude them with --skip-confidential, or include them all
# with --include-confidential.  If there are confidential items and you don't
# pass either of these options, then an exception will be thrown.  If you need
# more fine-grained control over confidential items, edit issues.ndjson by hand.
#
# 5. The projects I have tested this on are small, and don't make use of many of
# Gitlab's features.  This may bork on more complex projects.


# Still here?  Here's how to use this:
#
# First take an export of your Gitlab project from its settings area, then
# extract the archive.  The important files are tree/project/*.ndjson.
#
# Let's generate a report of all the emails that would be sent.  Preview the
# output to make sure things look right, and ensure that the command completes
# without error:
#
# ./import_issues.py \
#     --srht-owner=MY_SRHT_USER \
#     --srht-tracker=MY_SRHT_TRACKER \
#     --gitlab-project-url=https://gitlab.com/ME/PROJECT/ \
#     --from='Moi <me@email.com>' \
#     .../gitlab-export/tree/project \
#     >issue-emails.txt
#
# You may get errors if you are missing label or user mappings, and you haven't
# disabled these; see the LABELS and USERS variables below.
#
# If this file looks correct, then you can proceed with sending emails.
# Double-check that your tracket is empty to start with, then rerun the command
# with "--mode=send" and with your SMTP parameters.  SMTP options can be
# specified either via parameters --smtp-{host,port,user,password} or the
# equivalent SMTP_{HOST,PORT,USER,PASSWORD} environment variables.  Pass
# --smtp-ssl to enable SSL.  Also by default there is a five-second delay
# between sending emails, that you may wish to change with --smtp-delay.
#
# ./import_issues.py \
#     --srht-owner=MY_SRHT_USER \
#     --srht-tracker=MY_SRHT_TRACKER \
#     --gitlab-project-url=https://gitlab.com/ME/PROJECT/ \
#     --from='Moi <me@email.com>' \
#     --smtp-host=SMTP_HOSTNAME \
#     --smtp-ssl \
#     --smtp-user=SMTP_USERNAME \
#     --smtp-password=SMTP_PASSWORD \
#     .../gitlab-export/tree/project


import argparse
import json
import os
import re
import smtplib
import time
from email.message import EmailMessage
from email.utils import format_datetime, make_msgid
from datetime import datetime
from pathlib import Path
from typing import Dict, List, Optional


# Mapping from label IDs to names for the project.  This info is unfortunately
# not included in the Gitlab project export, and it's needed to transform raw
# label IDs into label names in issue notes.
#
# Any missing labels that are referenced from issues will cause an exception to
# be thrown.  Run with --mode=print first to make sure no labels are missing,
# before using --mode=send.
#
# Alternatively, set this to None to disable translation of label IDs to names.
LABELS: Optional[Dict[int, str]] = {
    # 123456: "Bug",
    # 232323: "Feature",
    # ...
}


# Mapping from user IDs to strings to use for their names when recording who
# created each ticket.  Gitlab exports user full names (but not necessarily
# IDs) names (but not necessarily IDs) for each note on an issue, but for the
# creator of an issue, only exports the user ID, no name.
#
# Any missing users that created issues will cause an exception to be thrown.
# Run with --mode=print first to make sure no users are missing, before using
# --mode=send.
#
# Alternatively, set this to None to disable recording issue creators.
#
# TODO Might be able to automatically map note.events.author_id to note.author.name.
USERS: Optional[Dict[int, str]] = {
    # 1234000: "John Joe (@jdoe)",
    # ...
}


email_count = 0
issue_count = 0


def do_mail(
        *,
        smtp,
        smtp_delay: float,
        mode: str,
        frm: str,
        to: str,
        body: str,
        subject: Optional[str] = None,
):
    global email_count
    email_count += 1
    print(f"---- #{email_count}")

    date = format_datetime(datetime.utcnow())
    msg_id = make_msgid()

    if mode == "print":
        print(f"From: {frm}")
        print(f"To: {to}")
        print(f"Date: {date}")
        if subject:
            print(f"Subject: {subject}")
        print(f"Message-ID: {msg_id}")
        print()
        print(body)

    elif mode == "send":
        msg = EmailMessage()
        msg.set_content(body)
        msg["From"] = frm
        msg["To"] = to
        msg["Date"] = date
        if subject:
            msg["Subject"] = subject

        # Message-ID is required, unless you want this error message from the
        # sr.ht mail server:
        #
        # 500 Error: (AttributeError) 'NoneType' object has no attribute
        # 'removeprefix' (in reply to end of DATA command)
        msg["Message-ID"] = msg_id

        smtp.send_message(msg)

        time.sleep(smtp_delay)

    else:
        raise RuntimeError(f"Unknown mode: {mode!r}")


def open_ticket(
        *,
        smtp,
        smtp_delay: float,
        mode: str,
        srht_owner: str,
        srht_tracker: str,
        frm: str,
        title: str,
        body: str,
        created_by: Optional[str],
        created_at: str,
        closed_at: Optional[str],
        is_closed: bool,
        is_confidential: bool,
        label_names: List[str],
        milestone_name: Optional[str],
        gitlab_ticket_url: str,
) -> int:
    global issue_count

    lines = []
    pheaders = []

    pheaders.append(f"Migrated from: {gitlab_ticket_url}")

    if created_by:
        pheaders.append(f"Created by: {created_by}")
    pheaders.append(f"Created at: {created_at}")

    if closed_at is not None:
        pheaders.append(f"Closed at: {closed_at}")
    elif is_closed:
        pheaders.append("State: closed")

    if milestone_name:
        pheaders.append(f"Milestone: {milestone_name}")

    if label_names:
        pheaders.append("Labels: " + ", ".join(sorted(label_names)))

    if is_confidential:
        pheaders.append("Confidential: true")

    lines.append(" \\\n".join(pheaders))
    lines.append("")
    lines.append(body)

    do_mail(
        smtp=smtp,
        smtp_delay=smtp_delay,
        mode=mode,
        frm=frm,
        to=f"~{srht_owner}/{srht_tracker}@todo.sr.ht",
        subject=title,
        body="\n".join(lines),
    )

    issue_count += 1
    return issue_count


def file_missing_ticket(
        *,
        smtp,
        smtp_delay: float,
        mode: str,
        srht_owner: str,
        srht_tracker: str,
        frm: str,
        issue_id: int,
):
    global issue_count

    do_mail(
        smtp=smtp,
        smtp_delay=smtp_delay,
        mode=mode,
        frm=frm,
        to=f"~{srht_owner}/{srht_tracker}@todo.sr.ht",
        subject="Missing issue",
        body=f"Issue {issue_id} is not known.",
    )

    issue_count += 1

    # TODO Send these emails at the end, so that there isn't such a need for the
    # previous issue to be processed promptly.
    close_ticket(
        smtp=smtp,
        smtp_delay=smtp_delay,
        mode=mode,
        srht_owner=srht_owner,
        srht_tracker=srht_tracker,
        frm=frm,
        issue_id=issue_count,
        closed_at=None,
        is_closed=False,  # Save one line of text.
    )


def send_comment(
        *,
        smtp,
        smtp_delay: float,
        mode: str,
        srht_owner: str,
        srht_tracker: str,
        frm: str,
        issue_id: int,
        body: str,
        author_name: str,
        created_at: str,
        last_edited_at: str,
        is_system: bool,
        is_confidential: bool,
):
    lines = []
    pheaders = []

    # Pseudo-headers, if any.
    if is_confidential:
        pheaders.append("Confidential: true")

    if pheaders:
        lines.append(" \\\n".join(pheaders))
        lines.append("")

    # Authorship note for a regular comment.
    if is_system:
        lines.append(f"Changed on {created_at} by {author_name}:")
    else:
        lines.append(f"On {created_at}, {author_name} wrote:")

    lines.append("")
    lines.append(body)

    if last_edited_at and last_edited_at != created_at:
        lines.append("")
        lines.append(f"(Last edited at {last_edited_at}.)")

    do_mail(
        smtp=smtp,
        smtp_delay=smtp_delay,
        mode=mode,
        frm=frm,
        to=f"~{srht_owner}/{srht_tracker}/{issue_id}@todo.sr.ht",
        body="\n".join(lines),
    )


def close_ticket(
        *,
        smtp,
        smtp_delay: float,
        mode: str,
        srht_owner: str,
        srht_tracker: str,
        frm: str,
        issue_id: int,
        closed_at: Optional[str],
        is_closed: bool,
):
    lines = []

    if closed_at is not None:
        # (Skipping pseudoheaders array here, only have one.)
        lines.append(f"Closed at: {closed_at}")
    elif is_closed:
        lines.append("Ticket closed.")

    lines.append("")
    lines.append("!resolve fixed")

    do_mail(
        smtp=smtp,
        smtp_delay=smtp_delay,
        mode=mode,
        frm=frm,
        to=f"~{srht_owner}/{srht_tracker}/{issue_id}@todo.sr.ht",
        body="\n".join(lines),
    )


def run(
        *,
        smtp,
        smtp_delay: float,
        mode: str,
        srht_owner: str,
        srht_tracker: str,
        frm: str,
        export_dir_path: Path,
        gitlab_project_url: str,
        skip_missing_issues: bool,
        create_missing_issues: bool,
        include_confidential: bool,
        skip_confidential: bool,
):
    milestone_jsons = []
    with open(export_dir_path / 'milestones.ndjson') as milestones_file:
        for line in milestones_file:
            milestone_jsons.append(json.loads(line))

    milestone_ids_to_titles = {}
    for milestone_json in milestone_jsons:
        milestone_ids_to_titles[milestone_json['iid']] = milestone_json['title']

    issue_jsons = []
    with open(export_dir_path / 'issues.ndjson') as issues_file:
        for line in issues_file:
            issue_jsons.append(json.loads(line))

    if skip_confidential:
        issue_jsons = [x for x in issue_jsons if not x.get('confidential')]
        for issue_json in issue_jsons:
            issue_json['notes'] = [
                n
                for n in issue_json['notes']
                if not n.get('confidential')
            ]

    elif not include_confidential:
        have_confidential_issues = any(
            x.get('confidential')
            for x in issue_jsons
        )
        have_confidential_notes = any(
            n.get('confidential')
            for x in issue_jsons
            for n in x['notes']
        )
        confidential_types = []
        if have_confidential_issues:
            confidential_types.append('issues')
        if have_confidential_notes:
            confidential_types.append('notes')
        assert not (have_confidential_issues or have_confidential_notes), \
            f"Found confidential {' and '.join(confidential_types)}; please " \
            f"decide whether these should all be included, then pass either " \
            f"--include-confidential or --skip-confidential, or edit " \
            f"issues.ndjson for more fine-grained control."

    issue_jsons.sort(key=lambda x: x['iid'])

    max_issue_id = max(x['iid'] for x in issue_jsons)
    present_issue_id_set = {x['iid'] for x in issue_jsons}
    missing_issue_ids = set(range(1, max_issue_id + 1)) - present_issue_id_set
    if missing_issue_ids and not (skip_missing_issues or create_missing_issues):
        if skip_confidential:
            because_confidential_msg = \
                " (possibly because some confidential issues were excluded)"
        else:
            because_confidential_msg = ""

        raise RuntimeError(
            f"Don't have all issues from 1 to {max_issue_id}{because_confidential_msg}, "
            f"please pass --create-missing-issues or --skip-missing-issues to proceed."
        )

    issues_by_id = {}
    for issue_json in issue_jsons:
        issues_by_id[issue_json['iid']] = issue_json

    # Need to sort notes by date, they seem to come unsorted.
    for issue_json in issue_jsons:
        issue_json['notes'].sort(key=lambda x: x['created_at'])

    print("-------- CREATING TICKETS")

    issue_id_map: Dict[int, int] = {}

    # While we're creating tickets, we can't just loop over the sorted
    # issue_jsons.  We have to loop over potential issue IDs and handle any that
    # are missing as well.
    for gitlab_issue_id in range(1, max_issue_id + 1):
        if gitlab_issue_id not in issues_by_id:
            if create_missing_issues:
                file_missing_ticket(
                    smtp=smtp,
                    smtp_delay=smtp_delay,
                    mode=mode,
                    srht_owner=srht_owner,
                    srht_tracker=srht_tracker,
                    frm=frm,
                    issue_id=gitlab_issue_id,
                )
            elif not skip_missing_issues:
                raise RuntimeError(
                    f"Internal error, don't know what to do with missing "
                    f"issue ID {gitlab_issue_id}."
                )

            continue

        issue_json = issues_by_id[gitlab_issue_id]

        author_id = issue_json['author_id']
        created_by: Optional[str]
        if USERS is None:
            created_by = None
        else:
            assert author_id in USERS, \
                f"Unknown author #{author_id} of ticket #{gitlab_issue_id}, please add to USERS."
            created_by = USERS[author_id]

        srht_issue_id = open_ticket(
            smtp=smtp,
            smtp_delay=smtp_delay,
            mode=mode,
            srht_owner=srht_owner,
            srht_tracker=srht_tracker,
            frm=frm,
            title=issue_json['title'],
            body=issue_json['description'],
            created_by=created_by,
            created_at=issue_json['created_at'],
            closed_at=issue_json['closed_at'],
            is_closed=(issue_json['state'] == 'closed'),
            is_confidential=(issue_json.get('confidential') is True),
            label_names=[x['label']['title'] for x in issue_json['label_links']],
            milestone_name=issue_json.get('milestone', {}).get('title') or None,
            gitlab_ticket_url=f"{gitlab_project_url}/-/issues/{gitlab_issue_id}",
        )

        if not skip_missing_issues:
            assert srht_issue_id == gitlab_issue_id, \
                f"Internal error, srht_issue_id {srht_issue_id} != " \
                f"gitlab_issue_id {gitlab_issue_id} " \
                f"(skip_missing_issues={skip_missing_issues}, " \
                f"create_missing_issues={create_missing_issues})."

        issue_id_map[gitlab_issue_id] = srht_issue_id

    print("-------- CREATING COMMENTS")

    for issue_json in issue_jsons:
        for note_json in issue_json['notes']:
            system_action = note_json.get('system_note_metadata', {}).get('action', None)

            body = note_json['note']

            # The "Removed" part is a guess here, don't know if that actually shows up.
            if LABELS is not None and (
                    system_action == 'label' or re.search(r'^(Added|Removed) ~[0-9]+ label', body)
            ):
                def expand_label(ref):
                    ref_num = int(ref.group(1))
                    assert ref_num in LABELS, \
                        f"Unknown label #{ref_num}, please add to LABELS."
                    return LABELS[ref_num]

                body = re.sub(r'~([0-9]+)', expand_label, body)

            if system_action == 'milestone' or re.search(r'^Milestone changed to %[0-9]+$', body):
                def expand_milestone(ref):
                    ref_num = int(ref.group(1))
                    assert ref_num in milestone_ids_to_titles, \
                        f"Unknown milestone #{ref_num}."
                    return milestone_ids_to_titles[ref_num]

                body = re.sub(r'%([0-9]+)', expand_milestone, body)

            send_comment(
                smtp=smtp,
                smtp_delay=smtp_delay,
                mode=mode,
                srht_owner=srht_owner,
                srht_tracker=srht_tracker,
                frm=frm,
                issue_id=issue_id_map[issue_json['iid']],
                body=body,
                author_name=note_json['author']['name'],
                created_at=note_json['created_at'],
                last_edited_at=note_json['last_edited_at'],
                is_system=note_json['system'],
                is_confidential=(note_json['confidential'] is True),
            )

    print("-------- CLOSING CLOSED ISSUES")

    for issue_json in issue_jsons:
        if issue_json['state'] == 'closed':
            close_ticket(
                smtp=smtp,
                smtp_delay=smtp_delay,
                mode=mode,
                srht_owner=srht_owner,
                srht_tracker=srht_tracker,
                frm=frm,
                issue_id=issue_id_map[issue_json['iid']],
                closed_at=issue_json['closed_at'],
                is_closed=(issue_json['state'] == 'closed'),
            )


def main():
    parser = argparse.ArgumentParser(
        prog='import_issues.py',
        description='Import Gitlab issues into Sourcehut via SMTP.',
    )

    parser.add_argument(
        '--srht-owner',
        required=True,
        help='Owner of the Sorucehut tracker.',
    )

    parser.add_argument(
        '--srht-tracker',
        required=True,
        help='Name of Sourcehut tracker to submit to.',
    )

    parser.add_argument(
        '--gitlab-project-url',
        required=True,
        help="The base URL the project on Gitlab.",
    )

    parser.add_argument(
        '--mode',
        default='print',
        help="Action to take, 'print' or 'send'.",
    )

    parser.add_argument(
        '--from',
        help="From address if mode is 'send'.",
    )

    parser.add_argument(
        '--smtp-host',
        help="SMTP host to use.",
    )

    parser.add_argument(
        '--smtp-port',
        default=None,
        help="SMTP port to use.",
    )

    parser.add_argument(
        '--smtp-ssl',
        action='store_true',
        help="Use SMTP over SSL.",
    )

    parser.add_argument(
        '--smtp-starttls',
        action='store_true',
        help="Use STARTTLS.",
    )

    parser.add_argument(
        '--smtp-user',
        help="SMTP username.",
    )

    parser.add_argument(
        '--smtp-password',
        help="SMTP password.",
    )

    parser.add_argument(
        '--smtp-delay',
        default=5,
        help="Decimal number of seconds to wait after sending each email.",
    )

    parser.add_argument(
        '--skip-missing-issues',
        action='store_true',
        help="Skip missing Gitlab issue IDs; GL and sr.ht IDs will not match.",
    )

    parser.add_argument(
        '--create-missing-issues',
        action='store_true',
        help="Create missing GL issues in sr.ht to make issue IDs match.",
    )

    parser.add_argument(
        '--include-confidential',
        action='store_true',
        help="Include confidential tickets and notes.",
    )

    parser.add_argument(
        '--skip-confidential',
        action='store_true',
        help="Skip confidential tickets and notes.",
    )

    parser.add_argument(
        'export_dir',
        help='Exported Gitlab tree/project/ directory containing ndjson files.',
    )

    args = vars(parser.parse_args())

    export_dir = args['export_dir']
    assert export_dir, f"Must have a exported project directory."
    export_dir_path = Path(export_dir)
    assert export_dir_path.is_dir(), \
        f"Project directory is not a directory: {export_dir_path}"

    mode = args['mode']
    frm = args['from']

    skip_missing_issues = args['skip_missing_issues']
    create_missing_issues = args['create_missing_issues']
    assert not (skip_missing_issues and create_missing_issues), \
        f"Can accept at most one of --skip-missing-issues and --create-missing-issues."

    include_confidential = args['include_confidential']
    skip_confidential = args['skip_confidential']
    assert not (include_confidential and skip_confidential), \
        f"Can accept at most one of --include-confidential and --skip-confidential."

    if mode == 'print':
        smtp = None
    elif mode == 'send':
        smtp_ssl = args['smtp_ssl']
        smtp_starttls = args['smtp_starttls']
        smtp_host = args['smtp_host'] or os.environ.get('SMTP_HOST', 'localhost')
        smtp_port = args['smtp_port'] or os.environ.get('SMTP_PORT', 465 if smtp_ssl else 25)
        smtp_user = args['smtp_user'] or os.environ.get('SMTP_USER', None)
        smtp_password = args['smtp_password'] or os.environ.get('SMTP_PASSWORD', None)

        assert smtp_user, f"No SMTP user given."
        assert smtp_password, f"No SMTP password given."

        print(f"Connecting to {smtp_host}:{smtp_port}, user {smtp_user!r}.")

        if smtp_ssl:
            smtp = smtplib.SMTP_SSL(host=smtp_host, port=smtp_port)
        else:
            smtp = smtplib.SMTP(host=smtp_host, port=smtp_port)

        # If SMTP isn't working:
        # smtp.set_debuglevel(2)

        if smtp_starttls:
            smtp.starttls()

        if smtp_user:
            smtp.login(smtp_user, smtp_password)

    run(
        smtp=smtp,
        smtp_delay=float(args['smtp_delay']),
        mode=mode,
        srht_owner=args['srht_owner'],
        srht_tracker=args['srht_tracker'],
        frm=frm,
        export_dir_path=export_dir_path,
        gitlab_project_url=args['gitlab_project_url'].rstrip('/'),
        skip_missing_issues=skip_missing_issues,
        create_missing_issues=create_missing_issues,
        include_confidential=include_confidential,
        skip_confidential=skip_confidential,
    )

    if mode == 'send':
        smtp.quit()


if __name__ == '__main__':
    main()