import { Injectable } from '@nestjs/common';
import type {
  AnyDomainEventEnvelope,
  DomainEventPayloads,
  DomainEventType,
} from '../domain-events/domain-event-types';
import { OnDomainEvent } from '../domain-events/on-domain-event.decorator';
import { Prisma } from '../../generated/prisma';
import { honeyBatchInclude } from '../honey-batches/honey-batch-include';
import { WebhookEvent } from './webhook-events';
import { WebhooksService } from './webhooks.service';

/** Which domain event goes out as which webhook event. */
export const DOMAIN_EVENT_WEBHOOKS: Readonly<
  Partial<Record<DomainEventType, WebhookEvent>>
> = Object.freeze({
  InspectionRecorded: 'inspection.created',
  VarroaMeasured: 'varroa.measured',
  TreatmentRecorded: 'treatment.created',
  FeedingRecorded: 'feeding.created',
  HarvestRecorded: 'harvest.created',
  BatchBottled: 'batch.updated',
  BottlingCorrected: 'batch.updated',
  HoneyBatchRecorded: 'batch.created',
  StockChanged: 'stock.changed',
  TaskCreated: 'task.created',
  TaskCompleted: 'task.completed',
  QueenAssigned: 'queen.replaced',
});

/**
 * Turns domain events into queued webhook deliveries. Pure DB writer: it
 * reads the record through the delivery transaction and queues the rows in
 * it (WebhooksService.enqueueDeliveries); the worker's webhook-deliveries
 * loop sends them. Errors propagate, so a failed delivery is retried.
 */
@Injectable()
export class WebhookEventHandlers {
  constructor(private readonly webhooks: WebhooksService) {}

  @OnDomainEvent(
    Object.keys(DOMAIN_EVENT_WEBHOOKS) as DomainEventType[],
    'webhooks.forward',
  )
  async forward(
    event: AnyDomainEventEnvelope,
    tx: Prisma.TransactionClient,
  ): Promise<void> {
    const webhookEvent = DOMAIN_EVENT_WEBHOOKS[event.type];
    if (webhookEvent === undefined) {
      return;
    }
    const data = await webhookData(event, tx);
    // The record is gone (deleted before the event was dispatched), or the
    // change is of no interest to receivers: nothing to send.
    if (data === null) {
      return;
    }
    await this.webhooks.enqueueDeliveries(tx, webhookEvent, data);
  }
}

/**
 * The webhook's `data`, as the legacy path sent it: the record the event is
 * about. Null when there is nothing to send.
 */
async function webhookData(
  event: AnyDomainEventEnvelope,
  tx: Prisma.TransactionClient,
): Promise<unknown> {
  const byAggregate = { where: { id: event.aggregateId } };
  switch (event.type) {
    case 'InspectionRecorded':
      return tx.inspection.findUnique(byAggregate);
    case 'VarroaMeasured':
      return tx.varroaMeasurement.findUnique(byAggregate);
    case 'TreatmentRecorded':
      return tx.treatment.findUnique(byAggregate);
    case 'FeedingRecorded':
      return tx.feeding.findUnique(byAggregate);
    case 'HarvestRecorded':
      return tx.harvest.findUnique({
        ...byAggregate,
        include: { colonies: { include: { colony: true } } },
      });
    // The aggregate is the bottling batch; receivers get its honey batch,
    // which outlives a removed bottling.
    case 'BatchBottled':
    case 'BottlingCorrected':
      return tx.honeyBatch.findUnique({
        where: { id: event.payload.honeyBatchId },
      });
    // The new honey batch with the relations the API shows, as the legacy
    // path sent it after the create.
    case 'HoneyBatchRecorded':
      return tx.honeyBatch.findUnique({
        ...byAggregate,
        include: honeyBatchInclude,
      });
    case 'StockChanged':
      return stockChange(event.payload);
    case 'TaskCreated':
    case 'TaskCompleted':
      return tx.task.findUnique(byAggregate);
    case 'QueenAssigned':
      return tx.queen.findUnique(byAggregate);
    default:
      return null;
  }
}

/**
 * Receivers (the shop) fetch the numbers themselves. Raw material is not
 * sold there, so a change that only touches raw material is not sent.
 */
function stockChange(
  payload: DomainEventPayloads['StockChanged'],
): { bottlingBatchIds: string[]; productIds: string[] } | null {
  if (
    payload.bottlingBatchIds.length === 0 &&
    payload.productIds.length === 0
  ) {
    return null;
  }
  return {
    bottlingBatchIds: [...new Set(payload.bottlingBatchIds)],
    productIds: [...new Set(payload.productIds)],
  };
}