import os
import json
import hashlib
from pathlib import Path


# Resolve cache directory with graceful fallbacks for unprivileged environments
def _resolve_cache_dir() -> Path:
    env = os.environ.get("FESTER_CACHE_DIR")
    if env:
        p = Path(env)
        p.mkdir(parents=True, exist_ok=True)
        return p
    for c in [
        Path("/var/lib/fester/cache"),
        Path.home() / ".fester" / "cache",
        Path("/tmp/fester_cache"),
    ]:
        try:
            c.mkdir(parents=True, exist_ok=True)
            return c
        except (OSError, PermissionError):
            continue
    # Last-resort in-memory (caller must handle None)
    return None


CACHE_DIR = _resolve_cache_dir()


def hash_dict(d):
    raw = json.dumps(d, sort_keys=True).encode()
    return hashlib.sha256(raw).hexdigest()


def make_build_key(snapshot_hash, target, env):
    return hashlib.sha256(
        f"{snapshot_hash}:{target}:{hash_dict(env)}".encode()
    ).hexdigest()


def cache_hit(key):
    if CACHE_DIR is None:
        return False
    return (CACHE_DIR / key / "done").exists()


def cache_store(key, log):
    if CACHE_DIR is None:
        return False
    base = CACHE_DIR / key
    base.mkdir(parents=True, exist_ok=True)

    (base / "done").write_text("1")
    (base / "log.txt").write_text(log)
    return True


def cache_log(key):
    if CACHE_DIR is None:
        return None
    p = CACHE_DIR / key / "log.txt"
    return p.read_text() if p.exists() else None


# ----------------------------
# ccache health probe
# ----------------------------
def ccache_stats():
    try:
        import subprocess

        out = subprocess.check_output(
            ["ccache", "-s"],
            stderr=subprocess.STDOUT
        ).decode()

        return out
    except:
        return "ccache not available"