import { Injectable, Logger } from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import { DoeOpenDataAdapter } from './adapters/doe-opendata.adapter';
import { TenderMatchingService } from './tender-matching.service';
import { TenderNormalizerService } from './tender-normalizer.service';

const DOE_SOURCE_TYPE = 'doe-opendata';
const RETENTION_DAYS = 90;
/** Polite delay between successive catch-up day-fetches (RESEARCH Open Question 1). */
const CATCH_UP_DELAY_MS = 1_500;
const MS_PER_DAY = 86_400_000;

/**
 * Day-cursor gate (RESEARCH.md "Day-cursor gate" snippet) — replaces a
 * `since: Date` timestamp cursor, because the DÖE OpenData API has no
 * incremental/since parameter; it is a daily batch-export API only.
 *
 * Returns the next `YYYY-MM-DD` to fetch, or `null` when nothing new is
 * available yet (dayCursor is not strictly before Europe/Berlin "today" —
 * D-01's "from now" semantics: the first eligible day for a never-polled
 * config is today itself, which is gated out until the next calendar day).
 */
export function nextDayToFetch(lastIngestedDay: Date | null): string | null {
  const berlinToday = new Date().toLocaleDateString('en-CA', {
    timeZone: 'Europe/Berlin',
  }); // YYYY-MM-DD
  const next = lastIngestedDay
    ? new Date(lastIngestedDay.getTime() + MS_PER_DAY).toISOString().slice(0, 10)
    : new Date().toISOString().slice(0, 10);
  return next < berlinToday ? next : null; // null = no-op this tick (Pitfall A)
}

function addOneDay(day: string): string {
  return new Date(new Date(`${day}T00:00:00Z`).getTime() + MS_PER_DAY)
    .toISOString()
    .slice(0, 10);
}

/**
 * TenderIngestionService — orchestrates the DÖE poll tick: day-cursor gate
 * -> fetch -> normalize -> upsert (SCHEMA-02 change detection) -> advance
 * cursor -> prune expired (D-05).
 *
 * Multi-tenant safety (D-03, T-10-09): uses the plain, non-tenant-scoped
 * PrismaService injected as-is. Never wraps `Tender`/`TenderSourcePollConfig`
 * queries in the tenant RLS extension — these are platform-global,
 * RLS-exempt tables. Applying that extension here would silently filter
 * out platform data for a 2nd tenant's session.
 *
 * Plan 12-01 (NOTIFY-03): pollDueSources now collects the IDs of genuinely
 * NEW Tender rows created this tick (via an indexed pre-check against the
 * existing upsert) and calls `TenderMatchingService.matchDelta` with only
 * those IDs at the end of the tick — this is the delta-only matching
 * boundary (D-07) that structurally prevents a backfill flood. Rows that
 * merely changed (SCHEMA-02 contentHash update) are NOT included.
 */
@Injectable()
export class TenderIngestionService {
  private readonly logger = new Logger(TenderIngestionService.name);

  /** Overridable (tests zero this out to avoid real sleeps). */
  protected politeDelayMs = CATCH_UP_DELAY_MS;

  constructor(
    private readonly prisma: PrismaService,
    private readonly doeAdapter: DoeOpenDataAdapter,
    private readonly normalizer: TenderNormalizerService,
    private readonly matching: TenderMatchingService,
  ) {}

  /**
   * Single global poll tick — poll-once-fan-out-many (INGEST-06). Called by
   * TenderSchedulerService's cron tick, on a shared, admin-configurable
   * interval, regardless of tenant count. Never throws — catch-and-log per
   * tick (DKV pattern), so a scheduler tick failure never crashes the process.
   */
  async pollDueSources(): Promise<void> {
    try {
      const config = await this.prisma.tenderSourcePollConfig.findUnique({
        where: { sourceType: DOE_SOURCE_TYPE },
      });
      if (!config?.isActive) return;

      let cursorDay = nextDayToFetch(config.lastIngestedDay);
      if (!cursorDay) {
        this.logger.debug(
          'Tender poll tick: no new DÖE day yet (day-cursor gate) — expected no-op, not a bug',
        );
        return;
      }

      const berlinToday = new Date().toLocaleDateString('en-CA', {
        timeZone: 'Europe/Berlin',
      });
      let fetchedAtLeastOneDay = false;
      let isFirstFetch = true;
      // Delta-only matching boundary (D-07, NOTIFY-03): only genuinely NEW
      // tender rows created THIS tick are collected here and handed to
      // matchDelta below — never changed/re-seen rows, never historical rows.
      const newTenderIds: string[] = [];

      while (cursorDay && cursorDay < berlinToday) {
        if (!isFirstFetch) {
          // Politeness delay between successive catch-up day-fetches only —
          // never before the first fetch of a tick.
          await this._delay(this.politeDelayMs);
        }
        isFirstFetch = false;

        const rawRecords = await this.doeAdapter.fetchTenders(cursorDay);
        const normalized = rawRecords.map((r) => this.normalizer.normalize(r));

        for (const tender of normalized) {
          // Indexed pre-check (dedupKey @unique) — the plain upsert below
          // does not report create-vs-update, so we check existence first
          // to determine whether this row is genuinely NEW this tick
          // (D-07 delta boundary). Negligible cost: a handful of records/
          // day for the DÖE source.
          const existing = await this.prisma.tender.findUnique({
            where: { dedupKey: tender.dedupKey },
            select: { id: true },
          });

          const saved = await this.prisma.tender.upsert({
            where: { dedupKey: tender.dedupKey },
            update: {
              title: tender.title,
              buyerName: tender.buyerName,
              cpvCodes: tender.cpvCodes,
              cpvDivisions: tender.cpvDivisions,
              region: tender.region,
              plz: tender.plz,
              bundesland: tender.bundesland,
              deadlineAt: tender.deadlineAt,
              estimatedValue: tender.estimatedValue,
              procedureType: tender.procedureType,
              sourceUrl: tender.sourceUrl,
              contentHash: tender.contentHash,
            },
            create: {
              sourcePortal: tender.sourcePortal,
              sourceNoticeId: tender.sourceNoticeId,
              ocid: tender.ocid,
              dedupKey: tender.dedupKey,
              title: tender.title,
              buyerName: tender.buyerName,
              cpvCodes: tender.cpvCodes,
              cpvDivisions: tender.cpvDivisions,
              region: tender.region,
              plz: tender.plz,
              bundesland: tender.bundesland,
              deadlineAt: tender.deadlineAt,
              estimatedValue: tender.estimatedValue,
              procedureType: tender.procedureType,
              status: tender.status,
              sourceUrl: tender.sourceUrl,
              contentHash: tender.contentHash,
              publishedAt: tender.publishedAt,
            },
          });

          if (!existing) newTenderIds.push(saved.id); // genuinely NEW row this tick (D-07)
        }

        await this.prisma.tenderSourcePollConfig.update({
          where: { sourceType: DOE_SOURCE_TYPE },
          data: { lastIngestedDay: new Date(`${cursorDay}T00:00:00Z`) },
        });

        fetchedAtLeastOneDay = true;
        cursorDay = addOneDay(cursorDay);
      }

      if (fetchedAtLeastOneDay) {
        await this.pruneExpiredTenders();
      }

      if (newTenderIds.length) {
        // Matching failures must never crash the ingestion tick — the
        // outer catch-and-log already covers this, but matchDelta itself
        // also catches per-profile (defense in depth).
        await this.matching.matchDelta(newTenderIds);
      }
    } catch (err) {
      this.logger.error(`Tender poll tick failed: ${(err as Error).message}`);
    }
  }

  /**
   * D-05 retention: mark past-deadline active rows 'expired', then delete
   * 'expired' rows whose deadline is older than the 90-day retention window.
   * Rows with `deadlineAt IS NULL` are excluded from BOTH operations — a
   * wrongly-deleted no-deadline tender is unrecoverable (RESEARCH Pattern 4
   * recommendation (a)); Prisma's `lt` comparison against null is always
   * false at the SQL level, so this exclusion holds structurally, not just
   * by convention.
   */
  async pruneExpiredTenders(): Promise<void> {
    const now = new Date();
    const retentionCutoff = new Date(now.getTime() - RETENTION_DAYS * MS_PER_DAY);

    await this.prisma.tender.updateMany({
      where: { status: 'active', deadlineAt: { lt: now } },
      data: { status: 'expired' },
    });

    await this.prisma.tender.deleteMany({
      where: { status: 'expired', deadlineAt: { lt: retentionCutoff } },
    });
  }

  private _delay(ms: number): Promise<void> {
    return new Promise((resolve) => setTimeout(resolve, ms));
  }
}