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

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

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


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


def log_event(kind, sev='info', msg='', meta=None):
    entry = {'ts': int(__import__('time').time()), 'kind': str(kind),
             'sev': sev, 'msg': msg[:500]}
    if meta:
        entry['meta'] = meta
    line = json.dumps(entry) + '\n'
    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:
                out.extend(json.loads(l) for l in f if l.strip())
        except (OSError, ValueError):
            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'))