import {
  BadRequestException,
  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 { BottlingBatch } from '../../generated/prisma';
import { CreateBottlingBatchDto } from './dto/create-bottling-batch.dto';
import { UpdateBottlingBatchDto } from './dto/update-bottling-batch.dto';

const bottlingBatchInclude = {
  honeyBatch: true,
  product: true,
} as const;

export interface BottlingBatchFilter {
  honeyBatchId?: string;
}

/**
 * Amounts are kept in kilograms with gram precision. Rounding on every write
 * keeps a honey batch's remaining amount from drifting when a bottling batch
 * is corrected or removed and its amount is given back.
 */
function roundKg(amount: number): number {
  return Math.round(amount * 1000) / 1000;
}

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

  async findAll(filter: BottlingBatchFilter = {}) {
    return this.prisma.bottlingBatch.findMany({
      where: { honeyBatchId: filter.honeyBatchId },
      include: bottlingBatchInclude,
      orderBy: { date: 'desc' },
    });
  }

  async findById(id: string) {
    const bottlingBatch = await this.prisma.bottlingBatch.findUnique({
      where: { id },
      include: bottlingBatchInclude,
    });
    if (!bottlingBatch) {
      throw new NotFoundException('Bottling batch not found');
    }
    return bottlingBatch;
  }

  async create(dto: CreateBottlingBatchDto, actingUserId: string) {
    const honeyBatch = await this.prisma.honeyBatch.findUnique({
      where: { id: dto.honeyBatchId },
    });
    if (!honeyBatch) {
      throw new NotFoundException('Honey batch not found');
    }
    if (dto.productId) {
      const product = await this.prisma.product.findUnique({
        where: { id: dto.productId },
      });
      if (!product) {
        throw new NotFoundException('Product not found');
      }
    }

    const totalAmount = (dto.jarSize * dto.jarCount) / 1000;
    if (honeyBatch.amount !== null && totalAmount > honeyBatch.amount) {
      throw new BadRequestException(
        'Abfüllmenge übersteigt die verfügbare Menge der Honigcharge',
      );
    }

    const lotNumber =
      dto.lotNumber ??
      (await this.automation.generateNumber('BOTTLING_LOT_NUMBER_FORMAT'));
    if (!lotNumber) {
      throw new BadRequestException(
        'Los-/Chargennummer erforderlich (oder Automatisierung "Los-/Chargennummer-Format" aktivieren)',
      );
    }

    const bottlingBatch: BottlingBatch = await this.prisma.$transaction(
      async (tx) => {
        const created = await tx.bottlingBatch.create({
          data: {
            honeyBatchId: dto.honeyBatchId,
            productId: dto.productId,
            date: new Date(dto.date),
            jarSize: dto.jarSize,
            jarCount: dto.jarCount,
            totalAmount,
            bestBeforeDate: new Date(dto.bestBeforeDate),
            lotNumber,
            userId: actingUserId,
          },
        });
        await tx.honeyBatch.update({
          where: { id: dto.honeyBatchId },
          data: {
            amount:
              honeyBatch.amount !== null
                ? honeyBatch.amount - totalAmount
                : null,
            status: 'BOTTLED',
          },
        });
        return created;
      },
    );

    await this.auditLog.record({
      entityType: 'BottlingBatch',
      entityId: bottlingBatch.id,
      action: 'CREATE',
      userId: actingUserId,
      afterData: bottlingBatch,
    });

    const created = await this.findById(bottlingBatch.id);
    await this.webhooks.dispatch('batch.updated', created.honeyBatch);
    return created;
  }

  /**
   * Corrects any field of an existing bottling batch. Changing the honey
   * batch, the jar size or the jar count also rebalances the remaining amount
   * of the affected honey batch(es): the previously bottled amount is given
   * back before the corrected amount is taken again, so a correction never
   * double-charges the source batch.
   */
  async update(id: string, dto: UpdateBottlingBatchDto, actingUserId: string) {
    const before = await this.findById(id);

    if (dto.productId) {
      const product = await this.prisma.product.findUnique({
        where: { id: dto.productId },
      });
      if (!product) {
        throw new NotFoundException('Product not found');
      }
    }

    const honeyBatchId = dto.honeyBatchId ?? before.honeyBatchId;
    const movedToOtherHoneyBatch = honeyBatchId !== before.honeyBatchId;
    const jarSize = dto.jarSize ?? before.jarSize;
    const jarCount = dto.jarCount ?? before.jarCount;
    const totalAmount = roundKg((jarSize * jarCount) / 1000);

    const targetHoneyBatch = movedToOtherHoneyBatch
      ? await this.prisma.honeyBatch.findUnique({ where: { id: honeyBatchId } })
      : before.honeyBatch;
    if (!targetHoneyBatch) {
      throw new NotFoundException('Honey batch not found');
    }

    // Capacity on the target batch, with this bottling batch's current amount
    // released first when it already sits on that same batch.
    const availableOnTarget =
      targetHoneyBatch.amount === null
        ? null
        : roundKg(
            targetHoneyBatch.amount +
              (movedToOtherHoneyBatch ? 0 : before.totalAmount),
          );
    if (availableOnTarget !== null && totalAmount > availableOnTarget) {
      throw new BadRequestException(
        'Abfüllmenge übersteigt die verfügbare Menge der Honigcharge',
      );
    }

    // A duplicate lotNumber surfaces as Prisma P2002 and is turned into a
    // 409 with a field-specific message by AllExceptionsFilter.
    await this.prisma.$transaction(async (tx) => {
      await tx.bottlingBatch.update({
        where: { id },
        data: {
          honeyBatchId,
          productId: dto.productId === undefined ? undefined : dto.productId,
          date: dto.date ? new Date(dto.date) : undefined,
          jarSize,
          jarCount,
          totalAmount,
          bestBeforeDate: dto.bestBeforeDate
            ? new Date(dto.bestBeforeDate)
            : undefined,
          lotNumber: dto.lotNumber,
        },
      });

      if (movedToOtherHoneyBatch) {
        await tx.honeyBatch.update({
          where: { id: before.honeyBatchId },
          data: {
            amount:
              before.honeyBatch.amount === null
                ? null
                : roundKg(before.honeyBatch.amount + before.totalAmount),
          },
        });
        await tx.honeyBatch.update({
          where: { id: honeyBatchId },
          data: {
            amount:
              availableOnTarget === null
                ? null
                : roundKg(availableOnTarget - totalAmount),
            status: 'BOTTLED',
          },
        });
      } else if (totalAmount !== before.totalAmount) {
        await tx.honeyBatch.update({
          where: { id: honeyBatchId },
          data: {
            amount:
              availableOnTarget === null
                ? null
                : roundKg(availableOnTarget - totalAmount),
          },
        });
      }
    });

    const bottlingBatch = await this.findById(id);
    await this.auditLog.record({
      entityType: 'BottlingBatch',
      entityId: id,
      action: 'UPDATE',
      userId: actingUserId,
      beforeData: before,
      afterData: bottlingBatch,
    });
    await this.webhooks.dispatch('batch.updated', bottlingBatch.honeyBatch);
    return bottlingBatch;
  }

  /**
   * Removes a bottling batch that was entered by mistake and gives its amount
   * back to the honey batch. The full record is kept in the audit log
   * (action DELETE, beforeData), so the history survives the row.
   *
   * The honey batch's status is deliberately left untouched: the status it
   * held before being bottled is not recoverable here, and guessing it would
   * write a fact that never happened.
   */
  async remove(id: string, actingUserId: string) {
    const before = await this.findById(id);

    await this.prisma.$transaction(async (tx) => {
      await tx.bottlingBatch.delete({ where: { id } });
      if (before.honeyBatch.amount !== null) {
        await tx.honeyBatch.update({
          where: { id: before.honeyBatchId },
          data: {
            amount: roundKg(before.honeyBatch.amount + before.totalAmount),
          },
        });
      }
    });

    await this.auditLog.record({
      entityType: 'BottlingBatch',
      entityId: id,
      action: 'DELETE',
      userId: actingUserId,
      beforeData: before,
    });
    await this.webhooks.dispatch('batch.updated', before.honeyBatch);
    return { id };
  }
}