// Investor Flow — AdapterQueue (DESIGN.md §5). Shared queue for all sources.
// Implements CacheScheduler (so CacheRepository.get schedules refreshes through it).
// Dedupe: adapter_queue PRIMARY KEY(key) + status check collapses concurrent same-key jobs
// to one fetch (ADR-0004). Token-bucket per source. Exponential backoff on failure.
import type { DatabaseSync } from 'node:sqlite';
import type { CacheKey, SourceKind, CacheRepository, CacheScheduler } from '../cache/CacheRepository.ts';
import { parseCacheKey } from '../cache/CacheRepository.ts';
import type { SourceFetch } from '../adapters/SourceAdapter.ts';

export interface AdapterQueueOptions {
  db: DatabaseSync;
  adapters: Map<SourceKind, SourceFetch>;
  /** Override per-source min-interval (ms); tests pass 0 to skip throttling. */
  rateLimitMs?: Partial<Record<SourceKind, number>>;
}

const DEFAULT_RATE_MS: Record<SourceKind, number> = { yfinance: 1000, sec: 125, 'sec-fetch': 1000, reddit: 1000, x: 3000, macro: 1000, llm: 0 };
const BACKOFF_MS = [2000, 4000, 8000, 16000, 60000];
const MAX_ATTEMPTS = 5;

const sleep = (ms: number) => new Promise<void>((r) => setTimeout(r, ms));

export interface QueueHealthDetailed {
  queued: number;
  in_flight: number;
  failed: number;
  backoff: number;
  done: number;
  backoff_until: string | null;
  last_error: string | undefined;
  paused: boolean;
  counts: Record<string, number>;
  lastErrors: Array<{ key: string; error: string | null }>;
}

export interface QueueErrorEntry {
  attempt: number;
  errorMessage: string | null;
  errorStack: string | null;
  ts: string;
}

export interface ScheduleEntry {
  sourceKind: string;
  intervalMs: number;
  lastEnqueued: string | null;
  nextEnqueue: string | null;
}

export class AdapterQueue implements CacheScheduler {
  private readonly _db: DatabaseSync;
  private readonly _adapters: Map<SourceKind, SourceFetch>;
  private readonly _rate: Record<SourceKind, number>;
  private _cache: CacheRepository | null = null;
  private _lastFetchAt: Partial<Record<SourceKind, number>> = {};
  private _lastError: string | null = null;

  constructor(opts: AdapterQueueOptions) {
    this._db = opts.db;
    this._adapters = opts.adapters;
    this._rate = { ...DEFAULT_RATE_MS, ...(opts.rateLimitMs ?? {}) } as Record<SourceKind, number>;
  }

  set cache(c: CacheRepository) { this._cache = c; }

  isPaused(): boolean {
    const row = this._db.prepare("SELECT value FROM queue_state WHERE key='paused'").get() as { value: string } | undefined;
    return row?.value === 'true';
  }

  setPaused(paused: boolean): void {
    this._db.prepare("INSERT OR REPLACE INTO queue_state (key, value) VALUES ('paused', ?)").run(String(paused));
  }

  async queue(key: CacheKey, scheduledFor?: string): Promise<void> {
    const row = this._db.prepare('SELECT status, backoff_until FROM adapter_queue WHERE key=?').get(key) as { status?: string; backoff_until?: string | null } | undefined;
    if (row) {
      if (row.status === 'pending' || row.status === 'in_flight') return;
      if (row.status === 'backoff' && row.backoff_until && Date.parse(row.backoff_until) > Date.now()) return;
    }
    this._db.prepare('INSERT OR REPLACE INTO adapter_queue (key,status,last_attempt,retry_count,backoff_until,error,scheduled_for) VALUES (?,?,?,?,?,?,?)').run(key, 'pending', null, 0, null, null, scheduledFor ?? null);
  }

  async drain(): Promise<void> {
    if (!this._cache) return;
    if (this.isPaused()) return;
    const now = Date.now();
    const jobs = this._db.prepare(
      "SELECT key, retry_count, backoff_until, scheduled_for FROM adapter_queue WHERE status IN ('pending','backoff') ORDER BY (last_attempt IS NULL) DESC, last_attempt ASC",
    ).all() as Array<{ key: string; retry_count: number; backoff_until?: string | null; scheduled_for?: string | null }>;

    for (const job of jobs) {
      if (job.backoff_until && Date.parse(job.backoff_until) > now) continue;
      if (job.scheduled_for && Date.parse(job.scheduled_for) > now) continue;
      const { source } = parseCacheKey(job.key);
      const adapter = this._adapters.get(source);
      if (!adapter) { this._setStatus(job.key, 'done'); continue; }
      const last = this._lastFetchAt[source] ?? 0;
      const wait = (this._rate[source] ?? 0) - (Date.now() - last);
      if (wait > 0) await sleep(wait);
      this._lastFetchAt[source] = Date.now();
      this._setStatus(job.key, 'in_flight');
      const attempt = job.retry_count + 1;
      try {
        const res = await adapter.fetchOne(job.key);
        await this._cache.set(job.key, res.value, res.ttlClass, res.provenance);
        this._db.prepare("UPDATE adapter_queue SET status='done', last_attempt=?, error=NULL WHERE key=?").run(new Date().toISOString(), job.key);
      } catch (e) {
        const msg = e instanceof Error ? e.message : String(e);
        const stack = e instanceof Error ? (e.stack ?? msg) : msg;
        this._lastError = msg;
        this._db.prepare("INSERT INTO queue_errors (queue_key, attempt, error_message, error_stack, ts) VALUES (?,?,?,?,?)").run(job.key, attempt, msg, stack, new Date().toISOString());
        if (attempt >= MAX_ATTEMPTS) {
          this._db.prepare("UPDATE adapter_queue SET status='failed', last_attempt=?, retry_count=?, backoff_until=NULL, error=? WHERE key=?").run(new Date().toISOString(), attempt, msg, job.key);
        } else {
          const bo = BACKOFF_MS[Math.min(attempt - 1, BACKOFF_MS.length - 1)];
          this._db.prepare("UPDATE adapter_queue SET status='backoff', last_attempt=?, retry_count=?, backoff_until=?, error=? WHERE key=?").run(new Date().toISOString(), attempt, new Date(Date.now() + bo).toISOString(), msg, job.key);
        }
      }
    }
  }

  retryJob(key: string): void {
    this._db.prepare("UPDATE adapter_queue SET status='pending', backoff_until=NULL, retry_count=0, error=NULL WHERE key=?").run(key);
  }

  retrySource(kind: string): number {
    const res = this._db.prepare(
      "UPDATE adapter_queue SET status='pending', backoff_until=NULL, retry_count=0, error=NULL WHERE status IN ('failed','backoff') AND substr(key,1,instr(key,':')-1)=?"
    ).run(kind);
    return Number(res.changes);
  }

  clearDone(olderThanMs: number = 86400000): number {
    const cutoff = new Date(Date.now() - olderThanMs).toISOString();
    const res = this._db.prepare("DELETE FROM adapter_queue WHERE status='done' AND last_attempt < ?").run(cutoff);
    return Number(res.changes);
  }

  setSchedule(sourceKind: string, intervalMs: number): void {
    this._db.prepare("INSERT OR REPLACE INTO queue_schedules (source_kind, interval_ms, last_enqueued, next_enqueue) VALUES (?,?,?,?)").run(sourceKind, intervalMs, null, new Date(Date.now() + intervalMs).toISOString());
  }

  deleteSchedule(sourceKind: string): void {
    this._db.prepare("DELETE FROM queue_schedules WHERE source_kind=?").run(sourceKind);
  }

  listSchedules(): ScheduleEntry[] {
    const rows = this._db.prepare("SELECT source_kind, interval_ms, last_enqueued, next_enqueue FROM queue_schedules ORDER BY source_kind").all() as Array<{ source_kind: string; interval_ms: number; last_enqueued: string | null; next_enqueue: string | null }>;
    return rows.map((r) => ({
      sourceKind: r.source_kind,
      intervalMs: r.interval_ms,
      lastEnqueued: r.last_enqueued,
      nextEnqueue: r.next_enqueue,
    }));
  }

  async enqueueDueSchedules(): Promise<void> {
    const now = new Date().toISOString();
    const due = this._db.prepare("SELECT * FROM queue_schedules WHERE next_enqueue IS NOT NULL AND next_enqueue <= ?").all(now) as Array<{ source_kind: string; interval_ms: number; last_enqueued: string | null; next_enqueue: string | null }>;
    for (const s of due) {
      const symbols = this._db.prepare("SELECT symbol FROM symbol_demand WHERE in_demand=1").all() as Array<{ symbol: string }>;
      if (s.source_kind === 'sec-fetch') {
        for (const sym of symbols) {
          await this.queue(`sec-fetch:fetch:${sym.symbol}`);
        }
      } else if (s.source_kind === 'yfinance') {
        for (const sym of symbols) {
          await this.queue(`yfinance:quote:${sym.symbol}`);
          await this.queue(`yfinance:candles:${sym.symbol}:1d`);
          await this.queue(`yfinance:symbol:${sym.symbol}`);
        }
      }
      const nextEnqueue = new Date(Date.now() + s.interval_ms).toISOString();
      this._db.prepare("UPDATE queue_schedules SET last_enqueued=?, next_enqueue=? WHERE source_kind=?").run(now, nextEnqueue, s.source_kind);
    }
  }

  seedDefaultSchedules(): void {
    const existing = this._db.prepare("SELECT COUNT(*) AS c FROM queue_schedules").get() as { c: number };
    if (existing.c > 0) return;
    const defaults: Array<[string, number]> = [
      ['sec-fetch', 86400000],
      ['yfinance', 300000],
    ];
    const insert = this._db.prepare("INSERT OR IGNORE INTO queue_schedules (source_kind, interval_ms, last_enqueued, next_enqueue) VALUES (?,?,?,?)");
    for (const [kind, ms] of defaults) {
      insert.run(kind, ms, null, new Date(Date.now() + ms).toISOString());
    }
  }

  health(): QueueHealthDetailed {
    const paused = this.isPaused();
    const row = this._db.prepare("SELECT SUM(status='pending') AS q, SUM(status='in_flight') AS i, SUM(status='failed') AS f, SUM(status='backoff') AS b, SUM(status='done') AS d, MAX(backoff_until) AS bu FROM adapter_queue").get() as { q: number | null; i: number | null; f: number | null; b: number | null; d: number | null; bu: string | null };
    const failedJobs = this._db.prepare("SELECT key, error FROM adapter_queue WHERE status='failed' AND error IS NOT NULL ORDER BY last_attempt DESC LIMIT 5").all() as Array<{ key: string; error: string | null }>;
    return {
      queued: row.q ?? 0,
      in_flight: row.i ?? 0,
      failed: row.f ?? 0,
      backoff: row.b ?? 0,
      done: row.d ?? 0,
      backoff_until: row.bu ?? null,
      last_error: this._lastError ?? undefined,
      paused,
      counts: { pending: row.q ?? 0, in_flight: row.i ?? 0, failed: row.f ?? 0, backoff: row.b ?? 0, done: row.d ?? 0 },
      lastErrors: failedJobs,
    };
  }

  getErrorLog(key: string, limit: number = 10): QueueErrorEntry[] {
    const rows = this._db.prepare("SELECT attempt, error_message, error_stack, ts FROM queue_errors WHERE queue_key=? ORDER BY attempt DESC LIMIT ?").all(key, limit) as Array<{ attempt: number; error_message: string | null; error_stack: string | null; ts: string }>;
    return rows.map((r) => ({
      attempt: r.attempt,
      errorMessage: r.error_message,
      errorStack: r.error_stack,
      ts: r.ts,
    }));
  }

  private _setStatus(key: string, status: string): void {
    this._db.prepare('UPDATE adapter_queue SET status=? WHERE key=?').run(status, key);
  }
}

export function createAdapterQueue(opts: AdapterQueueOptions): AdapterQueue {
  return new AdapterQueue(opts);
}