#!/usr/bin/python

import os
import subprocess
import sys
from datetime import datetime

BACKUP_DIR = os.environ["BACKUP_DIR"]

S3_PATH = os.environ["S3_PATH"]
S3_EXTRA_OPTIONS = os.environ.get("S3_EXTRA_OPTIONS") or ""

DB_USE_ENV = os.environ.get("DB_USE_ENV") or False
DB_NAME = os.environ["DB_NAME"] if "DB_NAME" in os.environ else os.environ.get("PGDATABASE")

if not DB_NAME:
    raise Exception("DB_NAME must be set")

if not DB_USE_ENV:
    DB_HOST = os.environ["DB_HOST"]
    DB_PASS = os.environ["DB_PASS"]
    DB_USER = os.environ["DB_USER"]
    DB_PORT = os.environ.get("DB_PORT") or "5432"

file_name = sys.argv[1]
backup_file = os.path.join(BACKUP_DIR, file_name)

if not S3_PATH.endswith("/"):
    S3_PATH = S3_PATH + "/"


def cmd(command, **kwargs):
    try:
        subprocess.check_output([command], shell=True, stderr=subprocess.STDOUT, **kwargs)
    except subprocess.CalledProcessError as e:
        sys.stderr.write("\n".join([
            "Command execution failed. Output:",
            "-" * 80,
            e.output,
            "-" * 80,
            ""
        ]))
        raise


def backup_exists():
    return os.path.exists(backup_file)


def restore_backup():
    if not backup_exists():
        sys.stderr.write("Backup file doesn't exists!\n")
        sys.exit(1)

    # restore postgres-backup
    env = os.environ.copy()
    if DB_USE_ENV:
        env.update({key: os.environ[key] for key in os.environ.keys() if key.startswith('PG')})
    else:
        env.update(
            {'PGPASSWORD': DB_PASS, 'PGHOST': DB_HOST, 'PGUSER': DB_USER, 'PGDATABASE': DB_NAME, 'PGPORT': DB_PORT})

    cmd("pg_restore -Fc -d %s %s" % (DB_NAME, backup_file), env=env)


def download_backup():
    cmd("aws s3 cp %s %s%s %s" % (S3_EXTRA_OPTIONS, S3_PATH, file_name, backup_file))


def log(msg):
    print("[%s]: %s" % (datetime.now().strftime("%Y-%m-%d %H:%M:%S"), msg))


def main():
    start_time = datetime.now()
    if backup_exists():
        log("Backup file already exists in filesystem %s" % backup_file)
    else:
        log("Downloading database dump")
        download_backup()

    log("Restoring database")
    restore_backup()

    log("Restore complete, took %.2f seconds" % (datetime.now() - start_time).total_seconds())


if __name__ == "__main__":
    main()