import {
  BadRequestException,
  ConflictException,
  Injectable,
  NotFoundException,
} from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import { AuditLogService } from '../audit/audit-log.service';
import { WebhooksService } from '../webhooks/webhooks.service';
import { AutomationService } from '../automation/automation.service';
import { Colony, ColonyStatus } from '../../generated/prisma';
import { CreateColonyDto } from './dto/create-colony.dto';
import { UpdateColonyDto } from './dto/update-colony.dto';
import { MoveColonyDto } from './dto/move-colony.dto';
import { SplitColonyDto } from './dto/split-colony.dto';
import { MergeColonyDto } from './dto/merge-colony.dto';
import { isLivingColonyStatus } from './colony-status';

export interface ColonyFilter {
  status?: ColonyStatus;
  apiaryId?: string;
}

@Injectable()
export class ColoniesService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly auditLog: AuditLogService,
    private readonly webhooks: WebhooksService,
    private readonly automation: AutomationService,
  ) {}

  async findAll(filter: ColonyFilter = {}): Promise<Colony[]> {
    return this.prisma.colony.findMany({
      where: { status: filter.status, apiaryId: filter.apiaryId },
      orderBy: { code: 'asc' },
    });
  }

  async findById(id: string): Promise<Colony> {
    const colony = await this.prisma.colony.findUnique({ where: { id } });
    if (!colony) {
      throw new NotFoundException('Colony not found');
    }
    return colony;
  }

  // Only a colony that no longer exists (dissolved, sold, dead, merged) is
  // locked. Weak, conspicuous or queenless colonies are still worked with -
  // uniting a queenless colony with another is the textbook case for merge.
  private assertActive(colony: Colony): void {
    if (!isLivingColonyStatus(colony.status)) {
      throw new ConflictException(
        `Das Volk besteht nicht mehr (Status: ${colony.status})`,
      );
    }
  }

  // Colony.apiaryId is a plain FK with no built-in status check - without
  // this, a colony could be created or moved into an apiary that either
  // doesn't exist (a raw Prisma FK-constraint error instead of a clean
  // 404) or is deactivated (silently orphaning the colony the same way an
  // apiary deactivated out from under an existing colony would).
  private async assertApiaryActive(apiaryId: string): Promise<void> {
    const apiary = await this.prisma.apiary.findUnique({
      where: { id: apiaryId },
    });
    if (!apiary) {
      throw new NotFoundException('Bienenstand nicht gefunden');
    }
    if (apiary.status !== 'ACTIVE') {
      throw new ConflictException(
        'Der Bienenstand ist nicht aktiv und kann daher keine Völker aufnehmen',
      );
    }
  }

  async create(dto: CreateColonyDto, actingUserId: string): Promise<Colony> {
    await this.assertApiaryActive(dto.apiaryId);
    const colony = await this.prisma.colony.create({ data: { ...dto } });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: colony.id,
      action: 'CREATE',
      userId: actingUserId,
      afterData: colony,
    });
    await this.webhooks.dispatch('colony.created', colony);
    return colony;
  }

  async update(
    id: string,
    dto: UpdateColonyDto,
    actingUserId: string,
  ): Promise<Colony> {
    const before = await this.findById(id);
    const movesApiary =
      dto.apiaryId !== undefined && dto.apiaryId !== before.apiaryId;
    if (movesApiary) {
      await this.assertApiaryActive(dto.apiaryId!);
    }

    const colony = await this.prisma.$transaction(async (tx) => {
      const updated = await tx.colony.update({
        where: { id },
        data: { ...dto },
      });
      // Correcting the apiary has to leave the same trace a deliberate move
      // does - otherwise the colony's location history would silently skip a
      // stand it was recorded on.
      if (movesApiary) {
        await tx.colonyApiaryHistory.create({
          data: {
            colonyId: id,
            apiaryId: updated.apiaryId,
            movedByUserId: actingUserId,
            notes: 'Korrektur über Volk bearbeiten',
          },
        });
      }
      return updated;
    });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: id,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: before,
      afterData: colony,
    });
    await this.automation.evaluateColonyHealth(before, colony);
    return colony;
  }

  async move(
    id: string,
    dto: MoveColonyDto,
    actingUserId: string,
  ): Promise<Colony> {
    const before = await this.findById(id);
    this.assertActive(before);
    await this.assertApiaryActive(dto.apiaryId);
    const colony = await this.prisma.$transaction(async (tx) => {
      const updated = await tx.colony.update({
        where: { id },
        data: { apiaryId: dto.apiaryId },
      });
      await tx.colonyApiaryHistory.create({
        data: {
          colonyId: id,
          apiaryId: dto.apiaryId,
          movedByUserId: actingUserId,
          notes: dto.notes,
        },
      });
      return updated;
    });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: id,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: before,
      afterData: colony,
    });
    return colony;
  }

  async split(
    id: string,
    dto: SplitColonyDto,
    actingUserId: string,
  ): Promise<Colony> {
    const parent = await this.findById(id);
    this.assertActive(parent);
    const child = await this.prisma.$transaction(async (tx) => {
      const created = await tx.colony.create({
        data: {
          code: dto.code,
          apiaryId: parent.apiaryId,
          colonyType: dto.colonyType,
          notes: dto.notes,
        },
      });
      await tx.colonyLineage.create({
        data: {
          type: 'SPLIT',
          fromColonyId: parent.id,
          toColonyId: created.id,
          date: new Date(),
          notes: dto.notes,
        },
      });
      return created;
    });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: child.id,
      action: 'CREATE',
      userId: actingUserId,
      afterData: { ...child, splitFromColonyId: parent.id },
    });
    return child;
  }

  async merge(
    id: string,
    dto: MergeColonyDto,
    actingUserId: string,
  ): Promise<Colony> {
    const survivor = await this.findById(id);
    this.assertActive(survivor);
    if (dto.mergedColonyIds.includes(survivor.id)) {
      throw new BadRequestException(
        'Ein Volk kann nicht mit sich selbst vereinigt werden',
      );
    }
    if (new Set(dto.mergedColonyIds).size !== dto.mergedColonyIds.length) {
      throw new BadRequestException(
        'Jedes Volk darf nur einmal zur Vereinigung ausgewählt werden',
      );
    }
    await this.prisma.$transaction(async (tx) => {
      for (const mergedColonyId of dto.mergedColonyIds) {
        const merged = await tx.colony.findUnique({
          where: { id: mergedColonyId },
        });
        if (!merged) {
          throw new NotFoundException(
            'Zu vereinigendes Volk wurde nicht gefunden',
          );
        }
        this.assertActive(merged);
        // currentQueenId is unique across colonies - if it stayed set on
        // this now-dead colony, any later attempt to assign her queen to a
        // different colony would fail with a unique-constraint conflict.
        // The survivor keeps its own queen; merged-away queens are simply
        // released, not auto-transferred (which colony's queen "wins" a
        // merge is a beekeeper decision, not one to guess here).
        await tx.colony.update({
          where: { id: mergedColonyId },
          data: {
            status: 'MERGED',
            deactivatedAt: new Date(),
            currentQueenId: null,
          },
        });
        if (merged.currentQueenId) {
          await tx.queenColonyHistory.updateMany({
            where: {
              queenId: merged.currentQueenId,
              colonyId: mergedColonyId,
              endDate: null,
            },
            data: { endDate: new Date() },
          });
        }
        await tx.colonyLineage.create({
          data: {
            type: 'MERGE',
            fromColonyId: mergedColonyId,
            toColonyId: survivor.id,
            date: new Date(),
            notes: dto.notes,
          },
        });
      }
    });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: survivor.id,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: survivor,
      afterData: { ...survivor, mergedColonyIds: dto.mergedColonyIds },
    });
    return this.findById(survivor.id);
  }

  async dissolve(id: string, actingUserId: string): Promise<Colony> {
    const before = await this.findById(id);
    // Re-dissolving would overwrite deactivatedAt and the terminal status
    // (e.g. MERGED -> DISSOLVED), losing when and how the colony really ended.
    this.assertActive(before);
    const colony = await this.prisma.$transaction(async (tx) => {
      const updated = await tx.colony.update({
        where: { id },
        data: {
          status: 'DISSOLVED',
          deactivatedAt: new Date(),
          currentQueenId: null,
        },
      });
      if (before.currentQueenId) {
        await tx.queenColonyHistory.updateMany({
          where: {
            queenId: before.currentQueenId,
            colonyId: id,
            endDate: null,
          },
          data: { endDate: new Date() },
        });
      }
      return updated;
    });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: id,
      action: 'DEACTIVATE',
      userId: actingUserId,
      beforeData: before,
      afterData: colony,
    });
    return colony;
  }

  async reactivate(id: string, actingUserId: string): Promise<Colony> {
    const before = await this.findById(id);
    // Only an ended colony can be brought back. A weak or queenless one
    // still exists - reactivating it would just overwrite its condition.
    if (isLivingColonyStatus(before.status)) {
      throw new ConflictException('Colony is already active');
    }
    const colony = await this.prisma.colony.update({
      where: { id },
      data: { status: 'ACTIVE', deactivatedAt: null },
    });
    await this.auditLog.record({
      entityType: 'Colony',
      entityId: id,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: before,
      afterData: colony,
    });
    return colony;
  }

  async getHistory(id: string) {
    await this.findById(id);
    const [apiaryHistory, queenHistory, lineageAsSource, lineageAsResult] =
      await Promise.all([
        this.prisma.colonyApiaryHistory.findMany({
          where: { colonyId: id },
          orderBy: { movedAt: 'desc' },
        }),
        this.prisma.queenColonyHistory.findMany({
          where: { colonyId: id },
          orderBy: { startDate: 'desc' },
        }),
        this.prisma.colonyLineage.findMany({ where: { fromColonyId: id } }),
        this.prisma.colonyLineage.findMany({ where: { toColonyId: id } }),
      ]);
    return { apiaryHistory, queenHistory, lineageAsSource, lineageAsResult };
  }
}