import { createHmac, randomBytes, randomUUID } from 'node:crypto';
import { Logger } from '@nestjs/common';
import {
  Command,
  CommandHandler,
  EventsHandler,
  ICommandHandler,
  IEventHandler,
  IQueryHandler,
  Query,
  QueryHandler,
} from '@nestjs/cqrs';
import {
  BusinessRuleError,
  NotFoundError,
  assertThat,
} from '@task-stream/api/shared/domain';
import { TrackerEvent } from '@task-stream/api/tracker/domain';
import { WriteAccess } from '../commands/write-access';
import { FindIssuesRepository } from '../ports/find-issues.repository';
import { FindProjectsRepository } from '../ports/find-projects.repository';
import {
  OutgoingWebhook,
  OutgoingWebhooksRepository,
  WebhookDelivery,
  WebhookSender,
} from '../ports/outgoing-webhooks.repository';
import { UserDirectory } from '../ports/user-directory';
import {
  WEBHOOK_EVENTS,
  normalizeWebhookEvents,
  subscribes,
  webhookEventOf,
} from './webhook-events';

/** A project keeps at most this many webhooks. */
export const MAX_WEBHOOKS = 20;
/** Waits between attempts: right away, after 2 s, after 10 s. */
export const RETRY_DELAYS_MS = [0, 2_000, 10_000];

/** The webhook as listed: the secret is only ever shown when created. */
export type WebhookView = Omit<OutgoingWebhook, 'secret'>;
const view = ({ secret: _secret, ...rest }: OutgoingWebhook): WebhookView =>
  rest;

function assertUrl(url: string): string {
  const next = url.trim();
  let parsed: URL | null = null;
  try {
    parsed = new URL(next);
  } catch {
    parsed = null;
  }
  assertThat(
    !!parsed && ['http:', 'https:'].includes(parsed.protocol),
    'A webhook needs an http(s) URL',
  );
  return next;
}

export class CreateWebhookCommand extends Command<{
  id: string;
  secret: string;
}> {
  constructor(
    public readonly actorId: string,
    public readonly projectId: string,
    public readonly url: string,
    public readonly events: string[],
  ) {
    super();
  }
}

export class UpdateWebhookCommand extends Command<WebhookView> {
  constructor(
    public readonly actorId: string,
    public readonly webhookId: string,
    public readonly changes: {
      url?: string;
      events?: string[];
      active?: boolean;
    },
  ) {
    super();
  }
}

export class DeleteWebhookCommand extends Command<void> {
  constructor(
    public readonly actorId: string,
    public readonly webhookId: string,
  ) {
    super();
  }
}

/** Sends a `ping` now and tells how it went. */
export class TestWebhookCommand extends Command<WebhookDelivery> {
  constructor(
    public readonly actorId: string,
    public readonly webhookId: string,
  ) {
    super();
  }
}

export class GetWebhooksQuery extends Query<WebhookView[]> {
  constructor(
    public readonly viewerId: string,
    public readonly projectId: string,
  ) {
    super();
  }
}

/** Signs and sends deliveries, retrying a couple of times, and records the outcome. */
export class WebhookDispatcher {
  private readonly logger = new Logger(WebhookDispatcher.name);

  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    private readonly sender: WebhookSender,
    private readonly delays: number[] = RETRY_DELAYS_MS,
  ) {}

  async deliver(
    webhook: OutgoingWebhook,
    event: string,
    payload: Record<string, unknown>,
  ): Promise<WebhookDelivery> {
    const deliveryId = randomUUID();
    const body = JSON.stringify({ event, deliveryId, ...payload });
    const signature = createHmac('sha256', webhook.secret)
      .update(body)
      .digest('hex');
    let delivery: WebhookDelivery = {
      at: new Date().toISOString(),
      event,
      status: null,
      ok: false,
      error: null,
    };
    for (const delay of this.delays) {
      if (delay) await new Promise((resolve) => setTimeout(resolve, delay));
      try {
        const { status } = await this.sender.send({
          url: webhook.url,
          body,
          headers: {
            'content-type': 'application/json',
            'user-agent': 'TaskStream-Webhooks',
            'x-taskstream-event': event,
            'x-taskstream-delivery': deliveryId,
            'x-taskstream-signature': `sha256=${signature}`,
          },
        });
        delivery = {
          ...delivery,
          at: new Date().toISOString(),
          status,
          ok: status < 300,
          error: status < 300 ? null : `HTTP ${status}`,
        };
        // A 4xx will not get better by retrying.
        if (delivery.ok || (status >= 400 && status < 500)) break;
      } catch (error) {
        delivery = {
          ...delivery,
          at: new Date().toISOString(),
          status: null,
          ok: false,
          error: error instanceof Error ? error.message : String(error),
        };
      }
    }
    if (!delivery.ok)
      this.logger.warn(
        `Webhook ${webhook.id} (${event}) failed: ${delivery.error}`,
      );
    await this.webhooks.recordDelivery(webhook.id, delivery);
    return delivery;
  }
}

/** Whoever manages the project of a webhook. */
async function managedWebhook(
  webhooks: OutgoingWebhooksRepository,
  access: WriteAccess,
  webhookId: string,
  actorId: string,
): Promise<OutgoingWebhook> {
  const webhook = await webhooks.findById(webhookId);
  if (!webhook) throw new NotFoundError('Webhook', webhookId);
  (await access.project(webhook.projectId)).assertCanManage(actorId);
  return webhook;
}

@CommandHandler(CreateWebhookCommand)
export class CreateWebhookCommandHandler
  implements ICommandHandler<CreateWebhookCommand>
{
  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    private readonly access: WriteAccess,
    private readonly users: UserDirectory,
  ) {}

  async execute(command: CreateWebhookCommand) {
    (await this.access.project(command.projectId)).assertCanManage(
      command.actorId,
    );
    const events = normalizeWebhookEvents(command.events);
    assertThat(events.length > 0, 'Pick at least one event');
    if (
      (await this.webhooks.findByProject(command.projectId)).length >=
      MAX_WEBHOOKS
    )
      throw new BusinessRuleError(
        `A project keeps at most ${MAX_WEBHOOKS} webhooks`,
      );
    const users = await this.users.refs([command.actorId]);
    const webhook: OutgoingWebhook = {
      id: randomUUID(),
      projectId: command.projectId,
      url: assertUrl(command.url),
      secret: randomBytes(24).toString('hex'),
      events,
      active: true,
      createdBy: users.of(command.actorId),
      createdAt: new Date().toISOString(),
      lastDelivery: null,
    };
    await this.webhooks.insert(webhook);
    return { id: webhook.id, secret: webhook.secret };
  }
}

@CommandHandler(UpdateWebhookCommand)
export class UpdateWebhookCommandHandler
  implements ICommandHandler<UpdateWebhookCommand>
{
  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    private readonly access: WriteAccess,
  ) {}

  async execute(command: UpdateWebhookCommand): Promise<WebhookView> {
    const webhook = await managedWebhook(
      this.webhooks,
      this.access,
      command.webhookId,
      command.actorId,
    );
    const changes: { url?: string; events?: string[]; active?: boolean } = {};
    if (command.changes.url !== undefined)
      changes.url = assertUrl(command.changes.url);
    if (command.changes.events !== undefined) {
      changes.events = normalizeWebhookEvents(command.changes.events);
      assertThat(changes.events.length > 0, 'Pick at least one event');
    }
    if (command.changes.active !== undefined)
      changes.active = command.changes.active;
    await this.webhooks.update(webhook.id, changes);
    return view({ ...webhook, ...changes });
  }
}

@CommandHandler(DeleteWebhookCommand)
export class DeleteWebhookCommandHandler
  implements ICommandHandler<DeleteWebhookCommand>
{
  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    private readonly access: WriteAccess,
  ) {}

  async execute(command: DeleteWebhookCommand): Promise<void> {
    const webhook = await managedWebhook(
      this.webhooks,
      this.access,
      command.webhookId,
      command.actorId,
    );
    await this.webhooks.delete(webhook.id);
  }
}

@CommandHandler(TestWebhookCommand)
export class TestWebhookCommandHandler
  implements ICommandHandler<TestWebhookCommand>
{
  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    private readonly access: WriteAccess,
    private readonly sender: WebhookSender,
  ) {}

  async execute(command: TestWebhookCommand): Promise<WebhookDelivery> {
    const webhook = await managedWebhook(
      this.webhooks,
      this.access,
      command.webhookId,
      command.actorId,
    );
    // One attempt: someone is waiting for the answer.
    return new WebhookDispatcher(this.webhooks, this.sender, [0]).deliver(
      webhook,
      'ping',
      {
        occurredAt: new Date().toISOString(),
        projectId: webhook.projectId,
        actorId: command.actorId,
        data: { message: 'Hola desde TaskStream' },
      },
    );
  }
}

@QueryHandler(GetWebhooksQuery)
export class GetWebhooksQueryHandler
  implements IQueryHandler<GetWebhooksQuery, WebhookView[]>
{
  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    private readonly access: WriteAccess,
  ) {}

  async execute(query: GetWebhooksQuery): Promise<WebhookView[]> {
    (await this.access.project(query.projectId)).assertCanManage(
      query.viewerId,
    );
    return (await this.webhooks.findByProject(query.projectId)).map(view);
  }
}

/** The event's own fields: what happened, without the envelope. */
function dataOf(event: TrackerEvent): Record<string, unknown> {
  const {
    actorId: _actor,
    aggregateId: _aggregate,
    projectId: _project,
    occurredAt: _at,
    aggregateVersion: _version,
    ...data
  } = event as unknown as Record<string, unknown>;
  return data;
}

/**
 * Tells the project's webhooks about what happened. Deliveries go out in the
 * background: a slow receiver never holds the events bridge.
 */
@EventsHandler(...WEBHOOK_EVENTS.map(([type]) => type))
export class OutgoingWebhooksEventHandler
  implements IEventHandler<TrackerEvent>
{
  private readonly dispatcher: WebhookDispatcher;

  constructor(
    private readonly webhooks: OutgoingWebhooksRepository,
    sender: WebhookSender,
    private readonly findProjects: FindProjectsRepository,
    private readonly findIssues: FindIssuesRepository,
  ) {
    this.dispatcher = new WebhookDispatcher(webhooks, sender);
  }

  async handle(event: TrackerEvent) {
    const name = webhookEventOf(event);
    if (!name) return;
    const targets = (await this.webhooks.findActive(event.projectId)).filter(
      (w) => subscribes(w.events, name),
    );
    if (!targets.length) return;
    const project = await this.findProjects.findById(event.projectId);
    const issueId = event.constructor.name.startsWith('Issue')
      ? event.aggregateId
      : ((event as { issueId?: string; comment?: { issueId: string } })
          .issueId ??
        (event as { comment?: { issueId: string } }).comment?.issueId ??
        null);
    const issue = issueId ? await this.findIssues.findById(issueId) : null;
    const payload = {
      occurredAt: event.occurredAt,
      actorId: event.actorId,
      project: project
        ? { id: project.id, key: project.key }
        : { id: event.projectId },
      aggregateId: event.aggregateId,
      version: event.aggregateVersion ?? null,
      ...(issue
        ? { issue: { id: issue.id, key: issue.key, title: issue.title } }
        : {}),
      data: dataOf(event),
    };
    for (const webhook of targets)
      void this.dispatcher
        .deliver(webhook, name, payload)
        .catch(() => undefined);
  }
}

export const WEBHOOK_HANDLERS = [
  CreateWebhookCommandHandler,
  UpdateWebhookCommandHandler,
  DeleteWebhookCommandHandler,
  TestWebhookCommandHandler,
  GetWebhooksQueryHandler,
  OutgoingWebhooksEventHandler,
];