#!/usr/bin/env python3
#
# Copyright 2024 Rodolphe Bréard <rodolphe@what.tf>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.


import argparse
import os
import smtplib
import subprocess
import tempfile
import time
from datetime import datetime
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.utils import COMMASPACE, formatdate

DEFAULT_EMAIL_HOST = "localhost"
DEFAULT_EMAIL_PORT = 25
DEFAULT_EMAIL_REPORT_SENDER = "PostgreSQL maintenance script <noreply@example.org>"
DEFAULT_PG_ADMIN_USER = "postgres"


def init_report(args):
    if not args.email_recipient:
        return None
    report = MIMEMultipart("alternative")
    report["Subject"] = f"Database maintenance for `{args.db_name}`"
    report["From"] = args.email_sender
    report["To"] = COMMASPACE.join(args.email_recipient)
    report["Date"] = formatdate(localtime=True)
    report["User-Agent"] = "PostgreSQL maintenance script"
    report["Content-Language"] = "en-US"
    return report


def send_report(args, vacuum, analyze, backup_create, backup_upload):
    report = init_report(args)
    if report is None:
        return
    vacuum_report = get_cmd_report("Vacuum", vacuum)
    analyze_report = get_cmd_report("Analyze", analyze)
    backup_report = get_backup_report(backup_create, backup_upload)
    report_txt = f"""Database maintenance report for `{args.db_name}`.

{vacuum_report}
{analyze_report}
{backup_report}
"""
    report.attach(MIMEText(report_txt))
    if vacuum.stdout:
        attach_file(report, "vacuum.log", vacuum.stdout)
    if vacuum.stderr:
        attach_file(report, "vacuum.err.log", vacuum.stderr)
    if analyze.stdout:
        attach_file(report, "analyze.log", analyze.stdout)
    if analyze.stderr:
        attach_file(report, "analyze.err.log", analyze.stderr)
    with smtplib.SMTP(host=args.email_host, port=args.email_port) as smtp:
        smtp.send_message(report)


def attach_file(report, file_name, file_content):
    part = MIMEApplication(file_content)
    part["Content-Disposition"] = f'attachment; filename="{file_name}"'
    report.attach(part)


def run_sql_cmd(args, cmd):
    cmd = [
        "psql",
        "--quiet",
        "--echo-queries",
        "--username",
        args.db_admin_user,
        "--dbname",
        args.db_name,
        "--command",
        cmd,
    ]
    start = time.time()
    ret = subprocess.run(cmd, capture_output=True)
    end = time.time()
    ret.elapsed_time = round(end - start, 3)
    return ret


def create_backup(args):
    if not args.destination:
        return None
    output_file = tempfile.NamedTemporaryFile()
    cmd = [
        "pg_dump",
        "--create",
        "--clean",
        "--no-unlogged-table-data",
        "--compress",
        "zstd",
        "--file",
        output_file.name,
        "--username",
        args.db_admin_user,
        "--dbname",
        args.db_name,
    ]
    start = time.time()
    ret = subprocess.run(cmd, capture_output=True)
    end = time.time()
    ret.elapsed_time = round(end - start, 3)
    ret.file_size = os.path.getsize(output_file.name)
    ret.file = output_file
    return ret


def upload_backup(args, backup_create):
    if not args.destination:
        return None
    timestamp = datetime.today().strftime("%Y-%m-%d")
    file_name = f"{timestamp}_{args.db_name}.sql.zst"
    cmd = ["rsync", backup_create.file.name, os.path.join(args.destination, file_name)]
    start = time.time()
    ret = subprocess.run(cmd, capture_output=True)
    end = time.time()
    ret.elapsed_time = round(end - start, 3)
    return ret


def get_cmd_report(name, cmd_ret):
    if cmd_ret.returncode == 0:
        return f"{name} completed in {cmd_ret.elapsed_time} s."
    else:
        return f"""{name} failed:
- error code: {cmd_ret.returncode}
- elapsed time: {cmd_ret.elapsed_time} s"""


def get_backup_report(backup_create, backup_upload):
    if not args.destination:
        return "No backup upload destination found."
    if backup_create.returncode != 0:
        return f"""Backup creation failed:
- error code: {backup_create.returncode}
- elapsed time: {backup_create.elapsed_time}s"""
    ret = f"""Backup creation completed:
- file size: {backup_create.file_size} B
- elapsed time: {backup_create.elapsed_time} s
"""
    if backup_upload.returncode != 0:
        ret += """Backup upload failed:
- error code: {backup_upload.returncode}
- message: {backup_upload.stderr}"""
    else:
        ret += f"Backup uploaded in {backup_upload.elapsed_time} s."
    return ret


def daily_db_maintenance(args):
    vacuum = run_sql_cmd(args, "VACUUM VERBOSE")
    analyze = run_sql_cmd(args, "ANALYZE VERBOSE")
    backup_create = create_backup(args)
    backup_upload = upload_backup(args, backup_create)
    send_report(args, vacuum, analyze, backup_create, backup_upload)


def get_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("db_name", help="name of the database to run maintenance on")
    parser.add_argument(
        "-u",
        "--db-admin-user",
        default=DEFAULT_PG_ADMIN_USER,
        help="name of the PostgreSQL superuser",
    )
    parser.add_argument("-d", "--destination", help="backup upload destination")
    parser.add_argument(
        "--email-host", default=DEFAULT_EMAIL_HOST, help="hostname of the email server"
    )
    parser.add_argument(
        "--email-port",
        type=int,
        default=DEFAULT_EMAIL_PORT,
        help="email server submission port",
    )
    parser.add_argument(
        "--email-sender",
        default=DEFAULT_EMAIL_REPORT_SENDER,
        help="sender of the email report",
    )
    parser.add_argument(
        "--email-recipient",
        nargs="*",
        help="recipient of the email report (may be specified multi times)",
    )
    return parser.parse_args()


if __name__ == "__main__":
    args = get_args()
    daily_db_maintenance(args)