import { Injectable } from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import { LIVING_COLONY_WHERE } from '../colonies/colony-status';

export interface DashboardSummary {
  apiariesActive: number;
  coloniesActive: number;
  queensActive: number;
  openTasks: number;
  honeyBatchesTotal: number;
  stockItemsLowCount: number;
}

export interface DashboardAlert {
  type:
    | 'OVERDUE_TASK'
    | 'COLONY_ATTENTION'
    | 'LOW_STOCK'
    | 'OVERDUE_SWARM_CHECK'
    | 'OLD_QUEEN';
  message: string;
  relatedType: string;
  relatedId: string;
}

const ATTENTION_COLONY_STATUSES = ['WEAK', 'QUEENLESS', 'CONSPICUOUS'] as const;
// Queens rarely stay reliably productive past their third season - laying
// rate and swarming risk both worsen well before then, so this flags a
// colony for evaluation rather than demanding immediate requeening.
const OLD_QUEEN_AGE_YEARS = 3;

@Injectable()
export class DashboardService {
  constructor(private readonly prisma: PrismaService) {}

  async summary(): Promise<DashboardSummary> {
    const [
      apiariesActive,
      coloniesActive,
      queensActive,
      openTasks,
      honeyBatchesTotal,
      stockItems,
    ] = await Promise.all([
      this.prisma.apiary.count({ where: { status: 'ACTIVE' } }),
      this.prisma.colony.count({ where: LIVING_COLONY_WHERE }),
      this.prisma.queen.count({
        where: { status: { in: ['ACTIVE', 'RESERVE'] } },
      }),
      this.prisma.task.count({
        where: { status: { in: ['OPEN', 'IN_PROGRESS'] } },
      }),
      this.prisma.honeyBatch.count(),
      this.prisma.stockItem.findMany({
        where: { minThreshold: { not: null } },
      }),
    ]);
    const stockItemsLowCount = stockItems.filter(
      (item) => item.minThreshold !== null && item.quantity < item.minThreshold,
    ).length;

    return {
      apiariesActive,
      coloniesActive,
      queensActive,
      openTasks,
      honeyBatchesTotal,
      stockItemsLowCount,
    };
  }

  async alerts(): Promise<DashboardAlert[]> {
    const [
      overdueTasks,
      attentionColonies,
      stockItems,
      swarmChecks,
      queenedColonies,
    ] = await Promise.all([
      this.prisma.task.findMany({
        where: {
          status: { in: ['OPEN', 'IN_PROGRESS'] },
          dueDate: { lt: new Date() },
        },
      }),
      this.prisma.colony.findMany({
        where: { status: { in: [...ATTENTION_COLONY_STATUSES] } },
      }),
      this.prisma.stockItem.findMany({
        where: { minThreshold: { not: null } },
      }),
      this.prisma.swarmControlCheck.findMany({
        where: { colony: LIVING_COLONY_WHERE },
        orderBy: [{ colonyId: 'asc' }, { date: 'desc' }],
        select: {
          colonyId: true,
          nextCheckDate: true,
          colony: { select: { code: true } },
        },
      }),
      this.prisma.colony.findMany({
        where: {
          ...LIVING_COLONY_WHERE,
          currentQueen: { hatchYear: { not: null } },
        },
        select: {
          id: true,
          code: true,
          currentQueen: { select: { hatchYear: true } },
        },
      }),
    ]);

    const alerts: DashboardAlert[] = [];
    for (const task of overdueTasks) {
      alerts.push({
        type: 'OVERDUE_TASK',
        message: `Aufgabe "${task.title}" ist überfällig`,
        relatedType: 'Task',
        relatedId: task.id,
      });
    }
    for (const colony of attentionColonies) {
      alerts.push({
        type: 'COLONY_ATTENTION',
        message: `Volk ${colony.code} benötigt Aufmerksamkeit (${colony.status})`,
        relatedType: 'Colony',
        relatedId: colony.id,
      });
    }
    for (const item of stockItems) {
      if (item.minThreshold !== null && item.quantity < item.minThreshold) {
        alerts.push({
          type: 'LOW_STOCK',
          message: `Lagerartikel "${item.name}" unter Mindestbestand`,
          relatedType: 'StockItem',
          relatedId: item.id,
        });
      }
    }
    // swarmChecks is ordered by colonyId then date desc, so the first entry
    // seen per colonyId is that colony's most recent check - only the most
    // recent nextCheckDate matters, an older overdue one has been superseded.
    const now = new Date();
    const latestCheckByColony = new Map<string, (typeof swarmChecks)[number]>();
    for (const check of swarmChecks) {
      if (!latestCheckByColony.has(check.colonyId)) {
        latestCheckByColony.set(check.colonyId, check);
      }
    }
    for (const check of latestCheckByColony.values()) {
      if (check.nextCheckDate && check.nextCheckDate < now) {
        alerts.push({
          type: 'OVERDUE_SWARM_CHECK',
          message: `Schwarmkontrolle für Volk ${check.colony.code} überfällig`,
          relatedType: 'Colony',
          relatedId: check.colonyId,
        });
      }
    }
    const currentYear = now.getFullYear();
    for (const colony of queenedColonies) {
      // The where clause above already requires currentQueen and its
      // hatchYear to exist, but the relation is still nullable in the type.
      if (!colony.currentQueen?.hatchYear) {
        continue;
      }
      const ageYears = currentYear - colony.currentQueen.hatchYear;
      if (ageYears >= OLD_QUEEN_AGE_YEARS) {
        alerts.push({
          type: 'OLD_QUEEN',
          message: `Königin in Volk ${colony.code} ist ${ageYears} Jahre alt - Nachzucht prüfen`,
          relatedType: 'Colony',
          relatedId: colony.id,
        });
      }
    }
    return alerts;
  }
}