"""Mark VIII reliability event journal. JSONL on /mmc, rotated."""
import json, os, threading, time

MK8_DIR = '/mmc/mk8'
EVENTS_PATH = os.path.join(MK8_DIR, 'events.log')
MAX_BYTES = 5 * 1024 * 1024
KEEP = 4
_LOCK = threading.Lock()

_COUNTER_KEYS = {'boot': 'boots', 'unexpected_boot': 'unexpected_boots',
                 'rollback': 'rollbacks', 'restart': 'restarts',
                 'guard_fix': 'guard_fixes'}
COUNTER_KINDS = tuple(_COUNTER_KEYS)


def _ensure_dir():
    try:
        os.makedirs(MK8_DIR, exist_ok=True)
    except OSError:
        pass


def log_event(kind, sev='info', msg='', meta=None):
    """Append one journal entry. Never raises: a reliability journal that
    can crash its caller would defeat its purpose. Single-writer per
    process is assumed; there is no inter-process lock."""
    try:
        entry = {'ts': int(time.time()), 'kind': str(kind), 'sev': sev,
                 'msg': str(msg)[:500]}
        if meta is not None:
            json.dumps(meta)
            entry['meta'] = meta
        line = json.dumps(entry) + '\n'
    except Exception:
        try:
            line = json.dumps({'ts': int(time.time()), 'kind': str(kind),
                               'sev': sev, 'msg': str(msg)[:500],
                               'meta_repr': repr(meta)[:500]}) + '\n'
        except Exception:
            return
    with _LOCK:
        _ensure_dir()
        try:
            if os.path.exists(EVENTS_PATH) and \
                    os.path.getsize(EVENTS_PATH) > MAX_BYTES:
                for i in range(KEEP - 1, 0, -1):
                    src = '%s.%d' % (EVENTS_PATH, i)
                    dst = '%s.%d' % (EVENTS_PATH, i + 1)
                    if os.path.exists(src):
                        os.replace(src, dst)
                if os.path.exists(EVENTS_PATH):
                    os.replace(EVENTS_PATH, EVENTS_PATH + '.1')
            with open(EVENTS_PATH, 'a') as f:
                f.write(line)
        except OSError:
            pass


def read_events(limit=100):
    out = []
    paths = [EVENTS_PATH + '.%d' % i for i in range(KEEP, 0, -1)]
    paths.append(EVENTS_PATH)
    for path in paths:
        try:
            with open(path) as f:
                for l in f:
                    if not l.strip():
                        continue
                    try:
                        row = json.loads(l)
                    except ValueError:
                        continue
                    if isinstance(row, dict):
                        out.append(row)
        except OSError:
            continue
    out.sort(key=lambda r: r.get('ts', 0))
    return out[-limit:][::-1]


def counters():
    counts = {v: 0 for v in _COUNTER_KEYS.values()}
    for row in read_events(limit=5000):
        k = row.get('kind')
        if k in _COUNTER_KEYS:
            counts[_COUNTER_KEYS[k]] += 1
    return counts


def mark_boot(unexpected=False):
    log_event('unexpected_boot' if unexpected else 'boot', sev='warn'
              if unexpected else 'info',
              msg='service started' + ('' if unexpected else ' cleanly'))