import { Router, type Request, type Response, type IRouter } from 'express';
import { nanoid } from 'nanoid';
import { db } from '../db/index.js';
import { agentOutputs, tipFeedback, tipViews, userPreferences } from '../db/schema.js';
import { eq, and, gt, lt } from 'drizzle-orm';
import { config } from '../config.js';
import { getProfile, type Profile } from '../profile/builder.js';
import { todoistSource } from '../signals/todoist.js';
import { SignalAggregator } from '../signals/aggregator.js';

const router: IRouter = Router();

// Separate aggregator instance — avoids circular dep with recommender.ts.
const _agentAggregator = new SignalAggregator().register(todoistSource);

// ── Internal auth helper ──────────────────────────────────────────────────────

function checkInternalToken(req: Request, res: Response): boolean {
  const token = req.headers['x-internal-token'];
  if (!config.INTERNAL_API_TOKEN || token !== config.INTERNAL_API_TOKEN) {
    res.status(401).json({ error: 'Unauthorized' });
    return false;
  }
  return true;
}

// ── DB helpers ────────────────────────────────────────────────────────────────

export async function getActiveAgentOutputs(userId: string) {
  const now = new Date().toISOString();
  return db
    .select()
    .from(agentOutputs)
    .where(and(eq(agentOutputs.userId, userId), gt(agentOutputs.expiresAt, now)));
}

async function storeAgentOutput(output: {
  user_id: string;
  agent_id: string;
  prompt_text: string;
  signals_snapshot?: unknown;
  computed_at: string;
  expires_at: string;
  agent_version: string;
}) {
  await db
    .delete(agentOutputs)
    .where(and(eq(agentOutputs.userId, output.user_id), eq(agentOutputs.agentId, output.agent_id)));
  await db.insert(agentOutputs).values({
    id: nanoid(),
    userId: output.user_id,
    agentId: output.agent_id,
    promptText: output.prompt_text,
    signalsSnapshot: output.signals_snapshot ? JSON.stringify(output.signals_snapshot) : null,
    computedAt: output.computed_at,
    expiresAt: output.expires_at,
    agentVersion: output.agent_version,
  });
}

// ── GET /api/agents/active-users ──────────────────────────────────────────────
// Returns user IDs that have requested a tip in the last 48 hours.
// Returns user IDs for fan-out precompute tasks.

router.get('/active-users', async (req: Request, res: Response) => {
  if (!checkInternalToken(req, res)) return;
  const cutoff = new Date(Date.now() - 48 * 60 * 60 * 1000).toISOString();
  try {
    const rows = await db
      .selectDistinct({ userId: tipViews.userId })
      .from(tipViews)
      .where(gt(tipViews.servedAt, cutoff));
    res.json({ user_ids: rows.map((r) => r.userId) });
  } catch (err: any) {
    res.status(500).json({ error: err.message });
  }
});

// ── Core compute logic (used by route + scheduler) ───────────────────────────

/** Load agent prefs for a user from user_preferences, merging user+inferred.
 * User source wins: if both exist, the 'user' row is returned. */
async function loadAgentPrefs(userId: string, agentId: string): Promise<Record<string, unknown>> {
  const scope = `agent:${agentId}`;
  const rows = await db
    .select({ key: userPreferences.key, valueJson: userPreferences.valueJson, source: userPreferences.source })
    .from(userPreferences)
    .where(and(eq(userPreferences.userId, userId), eq(userPreferences.scope, scope)));

  // Build merged dict: 'user' source takes precedence over 'inferred'
  const merged: Record<string, { value: unknown; source: string }> = {};
  for (const row of rows) {
    try {
      const value = JSON.parse(row.valueJson);
      const existing = merged[row.key];
      if (!existing || row.source === 'user') {
        merged[row.key] = { value, source: row.source };
      }
    } catch {
      // skip malformed
    }
  }
  return Object.fromEntries(Object.entries(merged).map(([k, v]) => [k, v.value]));
}

/** Persist inferred prefs to user_preferences, skipping keys the user has explicitly set. */
async function persistInferredPrefs(
  userId: string,
  agentId: string,
  inferredPrefs: Record<string, unknown>,
): Promise<void> {
  if (!Object.keys(inferredPrefs).length) return;
  const scope = `agent:${agentId}`;
  const now = new Date().toISOString();
  for (const [key, value] of Object.entries(inferredPrefs)) {
    const valueJson = JSON.stringify(value);
    await db
      .insert(userPreferences)
      .values({ userId, scope, key, valueJson, source: 'inferred', updatedAt: now })
      .onConflictDoUpdate({
        target: [userPreferences.userId, userPreferences.scope, userPreferences.key],
        set: { valueJson, updatedAt: now },
        // Only overwrite rows already marked inferred; user overrides are untouched.
        setWhere: eq(userPreferences.source, 'inferred'),
      });
  }
}

export async function computeAndStore(userId: string, agentId: string): Promise<void> {
  let tasks: object[] = [];
  try {
    const signals = await _agentAggregator.fetchAll(userId);
    tasks = signals.map((s) => ({
      id: s.id,
      content: s.content,
      priority: (s.features.priority as number) ?? 1,
      is_overdue: Boolean(s.features.is_overdue),
      task_age_days: (s.features.task_age_days as number) ?? 0,
      project_id: (s.metadata as Record<string, unknown>).project_id ?? null,
    }));
  } catch {
    // No integration or fetch error — agents that need tasks will report "no tasks"
  }

  let profile: Profile = {};
  try {
    profile = await getProfile(userId);
  } catch {}

  const sevenDaysAgo = new Date(Date.now() - 7 * 24 * 60 * 60 * 1000).toISOString();
  const feedbackRows = await db
    .select({ action: tipFeedback.action, dwellMs: tipFeedback.dwellMs, createdAt: tipFeedback.createdAt })
    .from(tipFeedback)
    .where(and(eq(tipFeedback.userId, userId), gt(tipFeedback.createdAt, sevenDaysAgo)));

  const feedbackHistory = feedbackRows.map((f) => ({
    action: f.action,
    dwell_ms: f.dwellMs,
    created_at: f.createdAt,
  }));

  // Load agent prefs (user overrides + previous inferences) to inject into the compute call.
  const agentPrefs = await loadAgentPrefs(userId, agentId);

  const mlResp = await fetch(`${config.ML_SERVING_URL}/agents/${agentId}/compute`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ user_id: userId, tasks, profile, feedback_history: feedbackHistory, agent_prefs: agentPrefs }),
    signal: AbortSignal.timeout(15_000),
  });

  if (!mlResp.ok) {
    const detail = await mlResp.text().catch(() => '');
    throw new Error(`ml/serving /agents/${agentId}/compute returned ${mlResp.status}: ${detail}`);
  }

  const output = await mlResp.json() as {
    user_id: string; agent_id: string; prompt_text: string;
    signals_snapshot: unknown; computed_at: string; expires_at: string; agent_version: string;
  };

  await storeAgentOutput(output);

  // Run inference framework for this agent and persist results.
  // Failures are non-fatal — the compute result is already stored.
  try {
    const inferResp = await fetch(`${config.ML_SERVING_URL}/agents/${agentId}/infer`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ user_id: userId, feedback_history: feedbackHistory }),
      signal: AbortSignal.timeout(10_000),
    });
    if (inferResp.ok) {
      const inferResult = await inferResp.json() as { inferred_prefs: Record<string, unknown> };
      await persistInferredPrefs(userId, agentId, inferResult.inferred_prefs);
    }
  } catch {
    // inference failure is non-fatal
  }
}

// ── POST /api/agents/:agentId/compute ─────────────────────────────────────────
// Orchestrating endpoint for per-(user, agent) compute tasks.
// Body: { user_id: string }

router.post('/:agentId/compute', async (req: Request, res: Response) => {
  if (!checkInternalToken(req, res)) return;

  const { agentId } = req.params as { agentId: string };
  const { user_id } = req.body as { user_id: string };

  if (!user_id) {
    res.status(422).json({ error: 'Missing user_id' });
    return;
  }

  try {
    await computeAndStore(user_id, agentId);
    res.json({ ok: true, agent_id: agentId, user_id });
  } catch (err: any) {
    const status = err.message?.includes('returned 4') ? 422 : 500;
    res.status(status).json({ error: err.message });
  }
});

// ── POST /api/agents/outputs ──────────────────────────────────────────────────
// Stores a pre-computed agent output directly (used if the DAG calls ml/serving
// itself and pushes the result separately).

router.post('/outputs', async (req: Request, res: Response) => {
  if (!checkInternalToken(req, res)) return;

  const { user_id, agent_id, prompt_text, signals_snapshot, computed_at, expires_at, agent_version } =
    req.body as Record<string, string>;

  if (!user_id || !agent_id || !prompt_text || !computed_at || !expires_at || !agent_version) {
    res.status(422).json({
      error: 'Missing required fields: user_id, agent_id, prompt_text, computed_at, expires_at, agent_version',
    });
    return;
  }

  try {
    await storeAgentOutput({ user_id, agent_id, prompt_text, signals_snapshot, computed_at, expires_at, agent_version });
    res.json({ ok: true });
  } catch (err: any) {
    res.status(500).json({ error: err.message });
  }
});

// ── DELETE /api/agents/outputs/expired ───────────────────────────────────────
// Purges rows expired more than 24 hours ago.

router.delete('/outputs/expired', async (req: Request, res: Response) => {
  if (!checkInternalToken(req, res)) return;
  const cutoff = new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString();
  try {
    await db.delete(agentOutputs).where(lt(agentOutputs.expiresAt, cutoff));
    res.json({ ok: true });
  } catch (err: any) {
    res.status(500).json({ error: err.message });
  }
});

// ── GET /api/agents/:userId/outputs ──────────────────────────────────────────
// Returns non-expired agent outputs. Admin observability; recommender calls
// getActiveAgentOutputs() directly (no HTTP hop).

router.get('/:userId/outputs', async (req: Request, res: Response) => {
  const { userId } = req.params as { userId: string };
  try {
    const rows = await getActiveAgentOutputs(userId);
    res.json({
      user_id: userId,
      outputs: rows.map((r) => ({
        agent_id: r.agentId,
        prompt_text: r.promptText,
        computed_at: r.computedAt,
        expires_at: r.expiresAt,
        agent_version: r.agentVersion,
      })),
    });
  } catch (err: any) {
    res.status(500).json({ error: err.message });
  }
});

export default router;