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 { DomainEventsService } from '../domain-events/domain-events.service';
import { utcDay } from '../domain-events/domain-event-types';
import { assertTransactionClient } from '../prisma/db-client';
import { lockRowForUpdate, lockRowsForUpdate } from '../prisma/row-lock';
import { Prisma, Queen, QueenStatus } from '../../generated/prisma';
import { CreateQueenDto } from './dto/create-queen.dto';
import { UpdateQueenDto } from './dto/update-queen.dto';
import { AssignColonyDto } from './dto/assign-colony.dto';
import { CreateQueenEvaluationDto } from './dto/create-queen-evaluation.dto';
import { UpdateQueenEvaluationDto } from './dto/update-queen-evaluation.dto';
import {
  TERMINAL_COLONY_STATUSES,
  isLivingColonyStatus,
} from '../colonies/colony-status';

export interface QueenFilter {
  status?: QueenStatus;
}

export interface QueenLineageAncestor {
  id: string;
  code: string;
  hatchYear: number | null;
  status: QueenStatus;
  mother: QueenLineageAncestor | null;
}

export interface QueenLineageDescendant {
  id: string;
  code: string;
  hatchYear: number | null;
  status: QueenStatus;
  daughters: QueenLineageDescendant[];
}

export interface QueenLineage {
  queen: QueenLineageAncestor;
  descendants: QueenLineageDescendant[];
}

const MAX_LINEAGE_DEPTH = 8;

// Once a queen reaches one of these statuses she is no longer really "in"
// whatever colony currently points at her - a colony's currentQueenId and
// status would otherwise silently go stale (still showing a dead/lost
// queen as current, never flagged QUEENLESS) until someone happens to
// notice and fix it by hand.
const QUEEN_NO_LONGER_AVAILABLE_STATUSES: QueenStatus[] = [
  'LOST',
  'DECEASED',
  'REPLACED',
  'SOLD',
];

/**
 * deactivatedAt for a queen moving to `status`: the /queens history and the
 * queen lifespans in the statistics read it. Stamped when she becomes
 * unavailable (the first date kept on a move between such statuses), cleared
 * when a status is corrected back to an available one.
 */
function deactivatedAtFor(before: Queen, status: QueenStatus): Date | null {
  if (QUEEN_NO_LONGER_AVAILABLE_STATUSES.includes(status)) {
    return before.deactivatedAt ?? new Date();
  }
  return null;
}

@Injectable()
export class QueensService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly auditLog: AuditLogService,
    private readonly webhooks: WebhooksService,
    private readonly events: DomainEventsService,
  ) {}

  async findAll(filter: QueenFilter = {}): Promise<Queen[]> {
    return this.prisma.queen.findMany({
      where: { status: filter.status },
      orderBy: { code: 'asc' },
    });
  }

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

  async create(dto: CreateQueenDto, actingUserId: string): Promise<Queen> {
    if (dto.motherQueenId) {
      await this.assertMotherQueenExists(dto.motherQueenId);
    }
    const queen = await this.prisma.queen.create({ data: { ...dto } });
    await this.auditLog.record({
      entityType: 'Queen',
      entityId: queen.id,
      action: 'CREATE',
      userId: actingUserId,
      afterData: queen,
    });
    await this.webhooks.dispatch('queen.created', queen);
    return queen;
  }

  async update(
    id: string,
    dto: UpdateQueenDto,
    actingUserId: string,
  ): Promise<Queen> {
    const before = await this.findById(id);
    if (dto.motherQueenId) {
      if (dto.motherQueenId === id) {
        throw new BadRequestException('A queen cannot be her own mother');
      }
      await this.assertMotherQueenExists(dto.motherQueenId);
    }
    const becameUnavailable =
      dto.status !== undefined &&
      dto.status !== before.status &&
      QUEEN_NO_LONGER_AVAILABLE_STATUSES.includes(dto.status);

    const queen = await this.prisma.$transaction(async (tx) => {
      const updated = await tx.queen.update({
        where: { id },
        data: {
          ...dto,
          deactivatedAt:
            dto.status === undefined
              ? undefined
              : deactivatedAtFor(before, dto.status),
        },
      });
      if (becameUnavailable) {
        const colony = await tx.colony.findUnique({
          where: { currentQueenId: id },
        });
        if (colony) {
          await tx.colony.update({
            where: { id: colony.id },
            data: {
              currentQueenId: null,
              status: TERMINAL_COLONY_STATUSES.includes(colony.status)
                ? undefined
                : 'QUEENLESS',
            },
          });
          await tx.queenColonyHistory.updateMany({
            where: { queenId: id, colonyId: colony.id, endDate: null },
            data: { endDate: new Date() },
          });
        }
      }
      return updated;
    });
    await this.auditLog.record({
      entityType: 'Queen',
      entityId: id,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: before,
      afterData: queen,
    });
    return queen;
  }

  /**
   * Differs from update(): this is the status alone, on the caller's
   * transaction, with the audit entry inside it. update() also lets go of
   * the colony that holds a queen who becomes unavailable (and audits after
   * its transaction); here that case is a 409, because the clean-up of an
   * ended colony must never unlink a colony she was re-assigned to.
   *
   * Sets the status of a queen on the caller's transaction: locks the queen,
   * reads it afterwards, audits the change. For a status that takes her out
   * of use it refuses while a colony still holds her (409) - the colony
   * side has to let go of her first (releaseQueenIn, assignColony); this
   * method never touches a colony. The same status again changes nothing.
   */
  async updateStatusIn(
    tx: Prisma.TransactionClient,
    id: string,
    status: QueenStatus,
    actingUserId: string,
  ): Promise<Queen> {
    assertTransactionClient(tx, 'QueensService.updateStatusIn');
    await lockRowForUpdate(tx, 'Queen', id);
    const before = await tx.queen.findUnique({ where: { id } });
    if (!before) {
      throw new NotFoundException('Queen not found');
    }
    if (before.status === status) {
      return before;
    }
    if (QUEEN_NO_LONGER_AVAILABLE_STATUSES.includes(status)) {
      const holder = await tx.colony.findUnique({
        where: { currentQueenId: id },
        select: { id: true },
      });
      if (holder) {
        throw new ConflictException(
          'Die Königin sitzt noch in einem Volk - bitte zuerst dort lösen',
        );
      }
    }
    const updated = await tx.queen.update({
      where: { id },
      data: { status, deactivatedAt: deactivatedAtFor(before, status) },
    });
    await this.auditLog.record(
      {
        entityType: 'Queen',
        entityId: id,
        action: 'UPDATE',
        userId: actingUserId,
        beforeData: before,
        afterData: updated,
      },
      tx,
    );
    return updated;
  }

  /**
   * Retires a queen who just left her colony with it (displaced by a new
   * queen, colony merged, dissolved or died): sets `status` through
   * updateStatusIn while she is still recorded as available, so she moves to
   * the archive. A status that already takes her out of use stays. The
   * caller has released her from the colony first.
   */
  async retireIn(
    tx: Prisma.TransactionClient,
    id: string,
    status: QueenStatus,
    actingUserId: string,
  ): Promise<void> {
    assertTransactionClient(tx, 'QueensService.retireIn');
    await lockRowForUpdate(tx, 'Queen', id);
    const queen = await tx.queen.findUnique({ where: { id } });
    if (!queen || QUEEN_NO_LONGER_AVAILABLE_STATUSES.includes(queen.status)) {
      return;
    }
    await this.updateStatusIn(tx, id, status, actingUserId);
  }

  async assignColony(
    id: string,
    dto: AssignColonyDto,
    actingUserId: string,
  ): Promise<Queen> {
    await this.findById(id);
    // Only to know which colony to lock; the transaction re-reads it.
    const preRead = await this.prisma.colony.findUnique({
      where: { currentQueenId: id },
      select: { id: true },
    });
    return this.prisma.$transaction(async (tx) => {
      // Colonies first (one statement, ascending ids), then the queen: the
      // order every writer of both uses.
      await lockRowsForUpdate(tx, 'Colony', [
        dto.colonyId,
        ...(preRead ? [preRead.id] : []),
      ]);
      await lockRowForUpdate(tx, 'Queen', id);
      const queen = await tx.queen.findUnique({ where: { id } });
      if (!queen) {
        throw new NotFoundException('Queen not found');
      }
      if (QUEEN_NO_LONGER_AVAILABLE_STATUSES.includes(queen.status)) {
        throw new ConflictException(
          'Die Königin ist nicht mehr verfügbar für eine Zuweisung - korrigiere zuerst ihren Status, falls dies ein Versehen war',
        );
      }
      const colony = await tx.colony.findUnique({
        where: { id: dto.colonyId },
      });
      if (!colony) {
        throw new NotFoundException('Colony not found');
      }
      if (!isLivingColonyStatus(colony.status)) {
        throw new ConflictException(
          `Das Volk besteht nicht mehr (Status: ${colony.status}) und kann keine Königin aufnehmen`,
        );
      }
      if (colony.currentQueenId === queen.id) {
        throw new ConflictException('Die Königin sitzt bereits in diesem Volk');
      }
      // The colony the queen leaves must let go of her - currentQueenId is
      // unique, and a stale pointer would both block this assignment and
      // keep showing her in a colony she is no longer in.
      const previousColony = await tx.colony.findUnique({
        where: { currentQueenId: queen.id },
      });
      if ((previousColony?.id ?? null) !== (preRead?.id ?? null)) {
        throw new ConflictException(
          'Die Königin wurde gerade umgesetzt - bitte erneut versuchen',
        );
      }

      const now = new Date();
      if (colony.currentQueenId) {
        await tx.queenColonyHistory.updateMany({
          where: {
            queenId: colony.currentQueenId,
            colonyId: colony.id,
            endDate: null,
          },
          data: { endDate: now },
        });
      }
      if (previousColony) {
        await tx.colony.update({
          where: { id: previousColony.id },
          data: {
            currentQueenId: null,
            status: TERMINAL_COLONY_STATUSES.includes(previousColony.status)
              ? undefined
              : 'QUEENLESS',
          },
        });
      }
      await tx.queenColonyHistory.updateMany({
        where: { queenId: queen.id, endDate: null },
        data: { endDate: now },
      });
      await tx.colony.update({
        where: { id: colony.id },
        data: {
          currentQueenId: queen.id,
          // Receiving a queen is what ends queenlessness; every other status
          // (weak, conspicuous) describes something a queen does not fix.
          status: colony.status === 'QUEENLESS' ? 'ACTIVE' : undefined,
        },
      });
      if (colony.currentQueenId) {
        await this.retireIn(
          tx,
          colony.currentQueenId,
          'REPLACED',
          actingUserId,
        );
      }
      const history = await tx.queenColonyHistory.create({
        data: {
          queenId: queen.id,
          colonyId: colony.id,
          startDate: now,
          notes: dto.notes,
        },
      });
      await this.auditLog.record(
        {
          entityType: 'Queen',
          entityId: queen.id,
          action: 'UPDATE',
          userId: actingUserId,
          beforeData: queen,
          afterData: { ...queen, assignedColonyId: colony.id },
        },
        tx,
      );
      await this.events.record(tx, {
        type: 'QueenAssigned',
        aggregateType: 'Queen',
        aggregateId: queen.id,
        actorUserId: actingUserId,
        payload: {
          colonyId: colony.id,
          historyId: history.id,
          assignedOn: utcDay(now),
          previousColonyId: previousColony?.id ?? null,
        },
      });
      return tx.queen.findUniqueOrThrow({ where: { id } });
    });
  }

  async getHistory(id: string) {
    await this.findById(id);
    return this.prisma.queenColonyHistory.findMany({
      where: { queenId: id },
      orderBy: { startDate: 'desc' },
    });
  }

  async getEvaluations(id: string) {
    await this.findById(id);
    return this.prisma.queenEvaluation.findMany({
      where: { queenId: id },
      orderBy: { date: 'desc' },
    });
  }

  async updateEvaluation(
    evaluationId: string,
    dto: UpdateQueenEvaluationDto,
    actingUserId: string,
  ) {
    const before = await this.prisma.queenEvaluation.findUnique({
      where: { id: evaluationId },
    });
    if (!before) {
      throw new NotFoundException('Queen evaluation not found');
    }
    const evaluation = await this.prisma.queenEvaluation.update({
      where: { id: evaluationId },
      data: { ...dto, date: dto.date ? new Date(dto.date) : undefined },
    });
    await this.auditLog.record({
      entityType: 'QueenEvaluation',
      entityId: evaluationId,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: before,
      afterData: evaluation,
    });
    return evaluation;
  }

  async addEvaluation(
    id: string,
    dto: CreateQueenEvaluationDto,
    actingUserId: string,
  ) {
    await this.findById(id);
    const evaluation = await this.prisma.queenEvaluation.create({
      data: {
        queenId: id,
        colonyId: dto.colonyId,
        date: new Date(dto.date),
        colonyStrength: dto.colonyStrength,
        gentleness: dto.gentleness,
        combBuild: dto.combBuild,
        swarmingTendency: dto.swarmingTendency,
        broodPattern: dto.broodPattern,
        honeyYield: dto.honeyYield,
        notes: dto.notes,
        userId: actingUserId,
      },
    });
    await this.auditLog.record({
      entityType: 'QueenEvaluation',
      entityId: evaluation.id,
      action: 'CREATE',
      userId: actingUserId,
      afterData: evaluation,
    });
    return evaluation;
  }

  async getLineage(id: string): Promise<QueenLineage> {
    const queen = await this.findById(id);
    const ancestorChain = await this.buildAncestorChain(
      queen,
      MAX_LINEAGE_DEPTH,
    );
    const descendants = await this.buildDescendantTree(id, MAX_LINEAGE_DEPTH);
    return { queen: ancestorChain, descendants };
  }

  private async assertMotherQueenExists(motherQueenId: string): Promise<void> {
    const mother = await this.prisma.queen.findUnique({
      where: { id: motherQueenId },
    });
    if (!mother) {
      throw new NotFoundException('Mother queen not found');
    }
  }

  private async buildAncestorChain(
    queen: Queen,
    depthRemaining: number,
  ): Promise<QueenLineageAncestor> {
    const node: QueenLineageAncestor = {
      id: queen.id,
      code: queen.code,
      hatchYear: queen.hatchYear,
      status: queen.status,
      mother: null,
    };
    if (queen.motherQueenId && depthRemaining > 0) {
      const mother = await this.prisma.queen.findUnique({
        where: { id: queen.motherQueenId },
      });
      if (mother) {
        node.mother = await this.buildAncestorChain(mother, depthRemaining - 1);
      }
    }
    return node;
  }

  private async buildDescendantTree(
    queenId: string,
    depthRemaining: number,
  ): Promise<QueenLineageDescendant[]> {
    if (depthRemaining <= 0) {
      return [];
    }
    const daughters = await this.prisma.queen.findMany({
      where: { motherQueenId: queenId },
      orderBy: { code: 'asc' },
    });
    return Promise.all(
      daughters.map(async (daughter) => ({
        id: daughter.id,
        code: daughter.code,
        hatchYear: daughter.hatchYear,
        status: daughter.status,
        daughters: await this.buildDescendantTree(
          daughter.id,
          depthRemaining - 1,
        ),
      })),
    );
  }
}