from __future__ import annotations

import hashlib
import json
import os
import time
from pathlib import Path
from typing import Any


def cache_root(config: dict) -> Path:
    root = Path(config.get("paths", {}).get("cache") or Path(config["paths"]["data"]) / "cache")
    root.mkdir(parents=True, exist_ok=True)
    return root


def cache_path(config: dict, namespace: str, key: str) -> Path:
    digest = hashlib.sha256(key.encode()).hexdigest()
    path = cache_root(config) / namespace / f"{digest}.json"
    path.parent.mkdir(parents=True, exist_ok=True)
    return path


def get_json(config: dict, namespace: str, key: str, ttl_seconds: int | None = None) -> Any | None:
    path = cache_path(config, namespace, key)
    if not path.exists():
        return None
    if ttl_seconds is not None and time.time() - path.stat().st_mtime > ttl_seconds:
        return None
    try:
        return json.loads(path.read_text())
    except (OSError, json.JSONDecodeError):
        return None


def set_json(config: dict, namespace: str, key: str, value: Any) -> None:
    path = cache_path(config, namespace, key)
    tmp = path.with_suffix(".tmp")
    tmp.write_text(json.dumps(value, sort_keys=True))
    tmp.replace(path)
    prune(config)


def remove_json(config: dict, namespace: str, key: str) -> None:
    path = cache_path(config, namespace, key)
    try:
        path.unlink()
    except FileNotFoundError:
        return


def prune(config: dict) -> None:
    root = cache_root(config)
    max_bytes = int(config.get("app", {}).get("cache_max_bytes", 20 * 1024**3))
    files = []
    total = 0
    for current, _, names in os.walk(root):
        for name in names:
            path = Path(current) / name
            try:
                stat = path.stat()
            except OSError:
                continue
            total += stat.st_size
            files.append((stat.st_mtime, stat.st_size, path))
    if total <= max_bytes:
        return
    for _, size, path in sorted(files):
        try:
            path.unlink()
            total -= size
        except OSError:
            continue
        if total <= max_bytes:
            break