# verifier.py — проверка доставки: потери, дубли, задержка.
#
# Схема: паблишер кладёт в payload run_id + seq + sent_at (epoch ms).
# Верификатор читает телеметрию через API и сверяет:
#   - delivered  — сколько строк с run_id дошло;
#   - lost       — сколько seq не доехало;
#   - duplicates — сколько seq приехало более одного раза;
#   - latency    — ts(PG) - sent_at (epoch ms). Точность зависит от
#                  синхронизации часов тест-машины и платформы (обе NTP).
from datetime import datetime

from .common import latency_stats


def _ts_to_ms(ts):
    """'2026-08-16T14:23:22.363648+03:00' → epoch ms (UTC)."""
    try:
        return datetime.fromisoformat(ts).timestamp() * 1000
    except (ValueError, TypeError):
        return None


class Verifier:
    def __init__(self, api, ns, run_id):
        self.api = api
        self.ns = ns
        self.run_id = run_id

    def device_report(self, device_id, expected):
        """Сверка по одному устройству. expected — сколько seq ждали.
        Пагинация по 50 строк: шлюз платформы рвёт ответы >~15 КБ
        (баг MSS/MTU, тикет Nubes) — большие страницы НЕ использовать."""
        rows = []
        offset = 0
        pages = 0
        while pages < 40:
            page = self.api.telemetry(self.ns, device_id=device_id,
                                      limit=50, offset=offset)
            items = page.get("items", [])
            rows.extend(items)
            pages += 1
            offset += 50
            if len(items) < 50 or len(rows) >= max(expected + 100, 200):
                break
        seqs = {}
        for r in rows:
            p = r.get("payload") or {}
            if p.get("run_id") != self.run_id:
                continue
            s = p.get("seq")
            if s is None:
                continue
            seqs.setdefault(s, []).append(
                (r.get("ts"), p.get("sent_at"))
            )
        delivered = len(seqs)
        lost = max(0, expected - delivered)
        duplicates = sum(len(v) - 1 for v in seqs.values() if len(v) > 1)
        lat = []
        first_lat = None
        for s, entries in seqs.items():
            ts, sent = entries[0]
            ts_ms = _ts_to_ms(ts) if ts else None
            if ts_ms is not None and isinstance(sent, (int, float)):
                l = max(0.0, ts_ms - sent)
                lat.append(l)
                if s == 0:
                    first_lat = l
        return {
            "device_id": device_id,
            "expected": expected,
            "delivered": delivered,
            "lost": lost,
            "duplicates": duplicates,
            "lat_ms": lat,
            "latency": latency_stats(lat),
            "first_latency_ms": round(first_lat, 1) if first_lat is not None else None,
        }

    def run_report(self, devices, expected_per_device):
        """Сводка по всем устройствам. Возвращает dict метрик."""
        total_expected = expected_per_device * len(devices)
        total_delivered = total_lost = total_dups = 0
        per = []
        all_lat = []
        for d in devices:
            r = self.device_report(d["device_id"], expected_per_device)
            per.append(r)
            total_delivered += r["delivered"]
            total_lost += r["lost"]
            total_dups += r["duplicates"]
            all_lat += r["lat_ms"]
        return {
            "devices": len(devices),
            "expected": total_expected,
            "delivered": total_delivered,
            "lost": total_lost,
            "loss_rate": round(total_lost / total_expected, 6) if total_expected else 0.0,
            "duplicates": total_dups,
            "latency": latency_stats(all_lat),
            "per_device": per,
        }