import { Injectable, Logger } from '@nestjs/common';
import { and, asc, eq, gte, isNull, lt, ne } from 'drizzle-orm';
import { db } from '../db/client';
import { organizations, researchBriefs, savedSegments, tasks } from '../db/schema';
import { AiGatewayService } from '../ai-gateway/ai-gateway.service';
import type { AuthenticatedSession } from '../auth/tenant.guard';

const SEVEN_DAYS_MS = 7 * 24 * 60 * 60 * 1000;
const BRIEFING_TEMPLATE_VERSION = 'daily-briefing@v1';

/**
 * Blueprint 17 "Daily Briefing": Scheduler -> collect tasks/deadlines -> deterministic
 * priority -> AI explanation -> save -> notify. Aici implementam doar partea
 * deterministica (colectare + prioritizare); explicatia AI vine cu AI Gateway-ul
 * (blueprint 14), inca neconstruit -- nu simulam text generat de AI.
 */
@Injectable()
export class BriefingService {
  private readonly logger = new Logger(BriefingService.name);

  constructor(private readonly aiGateway: AiGatewayService) {}

  async today(session: AuthenticatedSession) {
    const now = new Date();
    const weekAgo = new Date(now.getTime() - SEVEN_DAYS_MS);
    const weekFromNow = new Date(now.getTime() + SEVEN_DAYS_MS);

    const activeStatuses = [ne(tasks.status, 'done'), ne(tasks.status, 'cancelled')] as const;

    const [overdueTasks, upcomingTasks, newOrganizations, recentSegments, recentBriefs] =
      await Promise.all([
        db.query.tasks.findMany({
          where: and(
            eq(tasks.tenantId, session.tenantId),
            isNull(tasks.deletedAt),
            ...activeStatuses,
            lt(tasks.dueAt, now),
          ),
          orderBy: asc(tasks.dueAt),
        }),
        db.query.tasks.findMany({
          where: and(
            eq(tasks.tenantId, session.tenantId),
            isNull(tasks.deletedAt),
            ...activeStatuses,
            gte(tasks.dueAt, now),
            lt(tasks.dueAt, weekFromNow),
          ),
          orderBy: [asc(tasks.priority), asc(tasks.dueAt)],
        }),
        db.query.organizations.findMany({
          where: and(
            eq(organizations.tenantId, session.tenantId),
            isNull(organizations.deletedAt),
            gte(organizations.createdAt, weekAgo),
          ),
        }),
        db.query.savedSegments.findMany({
          where: and(eq(savedSegments.tenantId, session.tenantId), gte(savedSegments.createdAt, weekAgo)),
        }),
        db.query.researchBriefs.findMany({
          where: and(eq(researchBriefs.tenantId, session.tenantId), gte(researchBriefs.createdAt, weekAgo)),
        }),
      ]);

    const weekInReview = {
      newOrganizations: newOrganizations.length,
      newSegments: recentSegments.length,
      newResearchBriefs: recentBriefs.length,
    };

    return {
      generatedAt: now.toISOString(),
      overdueTasks,
      upcomingTasks,
      weekInReview,
      aiExplanation: await this.explain(session, overdueTasks, upcomingTasks, weekInReview),
    };
  }

  /**
   * Narativul AI peste datele deja prioritizate determinist (blueprint 17:
   * "deterministic priority -> AI explanation"). AI-ul explica, nu decide
   * ordinea. Esecul nu strica briefingul -- intoarce null, iar UI arata doar
   * partea deterministica.
   */
  private async explain(
    session: AuthenticatedSession,
    overdueTasks: { title: string; dueAt: Date | null }[],
    upcomingTasks: { title: string; dueAt: Date | null }[],
    weekInReview: { newOrganizations: number; newSegments: number; newResearchBriefs: number },
  ): Promise<string | null> {
    if (overdueTasks.length === 0 && upcomingTasks.length === 0) {
      return null;
    }

    const formatTask = (task: { title: string; dueAt: Date | null }) =>
      `- ${task.title}${task.dueAt ? ` (termen ${task.dueAt.toISOString().slice(0, 10)})` : ''}`;

    const state = [
      `Restante (${overdueTasks.length}):`,
      ...overdueTasks.slice(0, 10).map(formatTask),
      `Urmatoarele 7 zile (${upcomingTasks.length}):`,
      ...upcomingTasks.slice(0, 10).map(formatTask),
      `Saptamana: ${weekInReview.newOrganizations} companii noi, ${weekInReview.newSegments} segmente, ${weekInReview.newResearchBriefs} research briefs.`,
    ].join('\n');

    try {
      const result = await this.aiGateway.complete({
        tenantId: session.tenantId,
        requestedByUserId: session.userId,
        purpose: 'daily_briefing',
        actionClass: 'read_only',
        allowedCategories: ['tasks', 'deadlines', 'organizations'],
        deniedCategories: ['health', 'identity_documents'],
        model: 'gpt-4o-mini',
        templateVersion: BRIEFING_TEMPLATE_VERSION,
        systemPrompt:
          'Esti chief of staff. Scrii 2-3 propozitii in romana, direct, fara introduceri. ' +
          'Folosesti exclusiv datele primite; nu inventezi taskuri sau termene. ' +
          'Spui ce merita atentie azi si de ce.',
        userPrompt: `Rezuma situatia de azi pe baza starii de mai jos:\n\n${state}`,
        maxCostUsd: 0.05,
      });
      return result.content;
    } catch (error) {
      this.logger.warn(`Daily briefing AI explanation unavailable: ${(error as Error).message}`);
      return null;
    }
  }
}