#!/usr/bin/env python3
"""Enable durable local Redis writes and bound cache/queue memory without restart."""

import datetime
import fcntl
import json
import os
from pathlib import Path
import shutil
import subprocess
import time


def redis(*args):
    result = subprocess.run(
        ["redis-cli", "--json", *args], check=True, capture_output=True, text=True, timeout=10
    )
    if args[0] == "INFO":
        # redis-cli versions differ: INFO may remain raw with --json enabled.
        return json.loads(result.stdout) if result.stdout.lstrip().startswith('"') else result.stdout
    value = json.loads(result.stdout)
    if isinstance(value, dict) and "error" in value:
        raise RuntimeError("Redis configuration command failed")
    return value


def main():
    if os.geteuid() != 0:
        raise SystemExit("Run with sudo on CORP.")
    with open("/run/lock/eusrr-deploy.lock", "a") as lock:
        fcntl.flock(lock, fcntl.LOCK_EX | fcntl.LOCK_NB)
        configure_redis()


def info_fields(section):
    info = redis("INFO", section)
    if not isinstance(info, str):
        raise RuntimeError("Unsupported Redis INFO response")
    return dict(line.split(":", 1) for line in info.splitlines() if ":" in line)


def configure_redis():
    config = Path("/etc/redis/redis.conf")
    if config.is_symlink() or not config.is_file():
        raise SystemExit("Unexpected Redis configuration path.")
    old = redis(
        "CONFIG", "GET", "appendonly", "appendfsync", "maxmemory", "maxmemory-policy"
    )
    wanted = {
        "appendonly": "yes",
        "appendfsync": "everysec",
        "maxmemory": "268435456",
        "maxmemory-policy": "noeviction",
    }
    if not isinstance(old, dict) or set(old) != set(wanted):
        raise SystemExit("Unsupported redis-cli response format.")
    binds = redis("CONFIG", "GET", "bind")["bind"].split()
    if not binds or any(
        address.lstrip("-") not in {"127.0.0.1", "::1"} for address in binds
    ):
        raise SystemExit("Redis is not loopback-only; review networking first.")
    memory = info_fields("memory")
    used_memory = int(memory.get("used_memory", "-1"))
    if used_memory < 0 or used_memory > int(wanted["maxmemory"]) * 3 // 4:
        raise SystemExit("Redis is already too close to the proposed memory limit; size it before applying.")
    directory = redis("CONFIG", "GET", "dir").get("dir")
    if not directory or not Path(directory).is_absolute():
        raise SystemExit("Cannot verify the Redis persistence directory.")
    if shutil.disk_usage(directory).free < max(512 * 1024 * 1024, used_memory * 3):
        raise SystemExit("Insufficient free space for initial AOF and its rewrite reserve.")
    stamp = datetime.datetime.now(datetime.timezone.utc).strftime("%Y%m%dT%H%M%S%fZ")
    backup = Path("/var/lib/eusrr-deploy") / f"redis-backup-{stamp}"
    backup.mkdir(mode=0o700)
    shutil.copy2(config, backup / "redis.conf")
    try:
        for key, value in wanted.items():
            if redis("CONFIG", "SET", key, value) != "OK":
                raise RuntimeError("Redis rejected configuration change")
        for _ in range(30):
            fields = info_fields("persistence")
            if (
                fields.get("aof_rewrite_in_progress") == "0"
                and fields.get("aof_rewrite_scheduled") == "0"
            ):
                if (
                    fields.get("aof_enabled") != "1"
                    or fields.get("aof_last_bgrewrite_status") != "ok"
                ):
                    raise RuntimeError("Initial AOF snapshot failed")
                break
            time.sleep(1)
        else:
            raise RuntimeError("Initial AOF snapshot did not complete in time")
        if redis("CONFIG", "REWRITE") != "OK":
            raise RuntimeError("Could not persist Redis configuration")
        observed = redis("CONFIG", "GET", *wanted)
        if observed != wanted:
            raise RuntimeError("Redis settings verification failed")
    except BaseException as failure:
        recovery_errors = []
        for key, value in old.items():
            try:
                if redis("CONFIG", "SET", key, value) != "OK":
                    raise RuntimeError("Redis rejected rollback")
            except BaseException:
                recovery_errors.append(key)
        try:
            if redis("CONFIG", "REWRITE") != "OK":
                raise RuntimeError("Redis rejected rollback persistence")
        except BaseException:
            recovery_errors.append("configuration persistence")
        try:
            if redis("CONFIG", "GET", *old) != old:
                raise RuntimeError("Redis rollback verification failed")
        except BaseException:
            recovery_errors.append("verification")
        if recovery_errors:
            raise RuntimeError(
                f"Redis recovery incomplete ({', '.join(recovery_errors)}); inspect root backup {backup}"
            ) from failure
        raise
    print(
        "Redis AOF/everysec ready; maxmemory=256MiB, noeviction. No keys deleted, no restart."
    )
    print(f"Configuration backup: {backup}")


if __name__ == "__main__":
    main()