import { randomUUID } from 'node:crypto';
import { Logger } from '@nestjs/common';
import {
  Command,
  CommandBus,
  CommandHandler,
  EventPublisher,
  EventsHandler,
  ICommandHandler,
  IEventHandler,
  IQueryHandler,
  Query,
  QueryHandler,
} from '@nestjs/cqrs';
import {
  BusinessRuleError,
  NotFoundError,
} from '@task-stream/api/shared/domain';
import {
  CommentAddedEvent,
  CommentFactory,
  Issue,
  IssueAssignedEvent,
  IssueCreatedEvent,
  IssueDevLinkRecordedEvent,
  IssuePriority,
  IssueStatusChangedEvent,
  Project,
  SYSTEM_ACTOR_ID,
  TrackerEvent,
} from '@task-stream/api/tracker/domain';
import { WriteAccess } from '../commands/write-access';
import {
  Automation,
  AutomationsRepository,
} from '../ports/automations.repository';
import { FindSprintsRepository } from '../ports/find-sprints.repository';
import { UserDirectory } from '../ports/user-directory';
import {
  AutomationAction,
  AutomationActionKind,
  AutomationConditions,
  AutomationTrigger,
  normalizeRule,
  ruleApplies,
  triggerOf,
} from './automation-rules';

/** A project keeps at most this many rules. */
export const MAX_AUTOMATIONS = 50;

export interface AutomationInput {
  name: string;
  trigger: AutomationTrigger;
  conditions: AutomationConditions;
  action: AutomationAction;
}

export class CreateAutomationCommand extends Command<Automation> {
  constructor(
    public readonly actorId: string,
    public readonly projectId: string,
    public readonly rule: AutomationInput,
  ) {
    super();
  }
}

export class UpdateAutomationCommand extends Command<Automation> {
  constructor(
    public readonly actorId: string,
    public readonly automationId: string,
    public readonly changes: { name?: string; active?: boolean },
  ) {
    super();
  }
}

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

/** Event handler only: one rule's action on one ticket, as TaskStream. */
export class RunAutomationCommand extends Command<string | null> {
  constructor(
    public readonly automation: Automation,
    public readonly issueId: string,
  ) {
    super();
  }
}

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

async function managedProject(
  access: WriteAccess,
  projectId: string,
  actorId: string,
): Promise<Project> {
  const project = await access.project(projectId);
  project.assertCanManage(actorId);
  return project;
}

async function managedAutomation(
  automations: AutomationsRepository,
  access: WriteAccess,
  automationId: string,
  actorId: string,
): Promise<Automation> {
  const automation = await automations.findById(automationId);
  if (!automation) throw new NotFoundError('Automation', automationId);
  await managedProject(access, automation.projectId, actorId);
  return automation;
}

@CommandHandler(CreateAutomationCommand)
export class CreateAutomationCommandHandler
  implements ICommandHandler<CreateAutomationCommand>
{
  constructor(
    private readonly automations: AutomationsRepository,
    private readonly access: WriteAccess,
    private readonly users: UserDirectory,
  ) {}

  async execute(command: CreateAutomationCommand): Promise<Automation> {
    const project = await managedProject(
      this.access,
      command.projectId,
      command.actorId,
    );
    if (
      (await this.automations.findByProject(project.id)).length >=
      MAX_AUTOMATIONS
    )
      throw new BusinessRuleError(
        `A project keeps at most ${MAX_AUTOMATIONS} rules`,
      );
    const rule = normalizeRule(command.rule, project.workflow, (id) =>
      project.isMember(id),
    );
    const users = await this.users.refs([command.actorId]);
    const automation: Automation = {
      id: randomUUID(),
      projectId: project.id,
      ...rule,
      active: true,
      createdBy: users.of(command.actorId),
      createdAt: new Date().toISOString(),
      runs: 0,
      lastRunAt: null,
      lastError: null,
    };
    await this.automations.insert(automation);
    return automation;
  }
}

@CommandHandler(UpdateAutomationCommand)
export class UpdateAutomationCommandHandler
  implements ICommandHandler<UpdateAutomationCommand>
{
  constructor(
    private readonly automations: AutomationsRepository,
    private readonly access: WriteAccess,
  ) {}

  async execute(command: UpdateAutomationCommand): Promise<Automation> {
    const automation = await managedAutomation(
      this.automations,
      this.access,
      command.automationId,
      command.actorId,
    );
    const changes: { name?: string; active?: boolean } = {};
    if (command.changes.name !== undefined) {
      const name = command.changes.name.trim();
      if (!name || name.length > 80)
        throw new BusinessRuleError(
          'A rule needs a name (up to 80 characters)',
        );
      changes.name = name;
    }
    if (command.changes.active !== undefined)
      changes.active = command.changes.active;
    await this.automations.update(automation.id, changes);
    return { ...automation, ...changes };
  }
}

@CommandHandler(DeleteAutomationCommand)
export class DeleteAutomationCommandHandler
  implements ICommandHandler<DeleteAutomationCommand>
{
  constructor(
    private readonly automations: AutomationsRepository,
    private readonly access: WriteAccess,
  ) {}

  async execute(command: DeleteAutomationCommand): Promise<void> {
    const automation = await managedAutomation(
      this.automations,
      this.access,
      command.automationId,
      command.actorId,
    );
    await this.automations.delete(automation.id);
  }
}

/**
 * Applies the action straight on the aggregates, as TaskStream (the system
 * actor): the rule was set up by someone who manages the project, and the
 * workflow still has the last word. Returns why nothing happened, if so.
 */
@CommandHandler(RunAutomationCommand)
export class RunAutomationCommandHandler
  implements ICommandHandler<RunAutomationCommand>
{
  constructor(
    private readonly access: WriteAccess,
    private readonly findSprints: FindSprintsRepository,
    private readonly commentFactory: CommentFactory,
    private readonly eventPublisher: EventPublisher,
  ) {}

  async execute(command: RunAutomationCommand): Promise<string | null> {
    const issue = await this.access.live(command.issueId, Issue);
    const project = issue
      ? await this.access.live(issue.projectId, Project)
      : null;
    if (!issue || !project) return 'The ticket is gone';
    const { kind, value } = command.automation.action;
    const actor = SYSTEM_ACTOR_ID;
    switch (kind) {
      case AutomationActionKind.SET_STATUS:
        if (!value || issue.status === value) return null;
        issue.changeStatus(actor, value, 'Automatización', project.workflow);
        break;
      case AutomationActionKind.ASSIGN:
      case AutomationActionKind.ASSIGN_REPORTER: {
        const assignee =
          kind === AutomationActionKind.ASSIGN
            ? (value ?? null)
            : issue.reporterId;
        if (!assignee || !project.isMember(assignee))
          return 'That person is no longer a member';
        issue.assign(actor, assignee);
        break;
      }
      case AutomationActionKind.ADD_LABEL:
        if (!value || issue.labels.includes(value)) return null;
        issue.updateDetails(
          actor,
          { labels: [...issue.labels, value] },
          project.workflow,
        );
        break;
      case AutomationActionKind.SET_PRIORITY:
        issue.updateDetails(
          actor,
          { priority: value as IssuePriority },
          project.workflow,
        );
        break;
      case AutomationActionKind.ADD_TO_ACTIVE_SPRINT: {
        const active = await this.findSprints.findActive(project.id);
        if (!active) return 'No sprint is under way';
        issue.setSprint(actor, active.id);
        break;
      }
      case AutomationActionKind.ADD_COMMENT: {
        const comment = this.commentFactory.create({
          issueId: issue.id,
          projectId: issue.projectId,
          authorId: actor,
          body: value ?? '',
        });
        this.eventPublisher.mergeObjectContext(comment);
        await comment.commitAndWait();
        return null;
      }
    }
    await issue.commitAndWait();
    return null;
  }
}

@QueryHandler(GetAutomationsQuery)
export class GetAutomationsQueryHandler
  implements IQueryHandler<GetAutomationsQuery, Automation[]>
{
  constructor(
    private readonly automations: AutomationsRepository,
    private readonly access: WriteAccess,
  ) {}

  async execute(query: GetAutomationsQuery): Promise<Automation[]> {
    await managedProject(this.access, query.projectId, query.viewerId);
    return this.automations.findByProject(query.projectId);
  }
}

/**
 * Runs the project's rules on what people do. What rules themselves do (as
 * TaskStream) triggers nothing more: no chains, no loops. Each rule runs once
 * per event, also when the event is delivered again.
 */
@EventsHandler(
  IssueCreatedEvent,
  IssueStatusChangedEvent,
  IssueAssignedEvent,
  CommentAddedEvent,
  IssueDevLinkRecordedEvent,
)
export class AutomationsEventHandler implements IEventHandler<TrackerEvent> {
  private readonly logger = new Logger(AutomationsEventHandler.name);

  constructor(
    private readonly automations: AutomationsRepository,
    private readonly access: WriteAccess,
    private readonly commandBus: CommandBus,
  ) {}

  async handle(event: TrackerEvent) {
    // Git reports come as the system too, and a merge is worth reacting to.
    if (
      event.actorId === SYSTEM_ACTOR_ID &&
      !(event instanceof IssueDevLinkRecordedEvent)
    )
      return;
    const trigger = triggerOf(event);
    if (!trigger) return;
    const rules = await this.automations.findActive(event.projectId);
    if (!rules.length) return;
    const issue = await this.access.live(trigger.issueId, Issue);
    if (!issue) return;
    for (const rule of rules) {
      if (!ruleApplies(rule, trigger, issue)) continue;
      const key = `${event.aggregateId}:${event.aggregateVersion ?? event.occurredAt}`;
      if (!(await this.automations.claimRun(rule.id, key))) continue;
      let error: string | null;
      try {
        error = await this.commandBus.execute(
          new RunAutomationCommand(rule, trigger.issueId),
        );
      } catch (failure) {
        error = failure instanceof Error ? failure.message : String(failure);
        this.logger.warn(`Rule ${rule.id} on ${trigger.issueId}: ${error}`);
      }
      await this.automations.recordRun(rule.id, error);
    }
  }
}

export const AUTOMATION_HANDLERS = [
  CreateAutomationCommandHandler,
  UpdateAutomationCommandHandler,
  DeleteAutomationCommandHandler,
  RunAutomationCommandHandler,
  GetAutomationsQueryHandler,
  AutomationsEventHandler,
];