feat: add server authoritative travel flow

apps/api/src/travel/travel.service.ts

@@ -0,0 +1,224 @@
+import { Inject, Injectable } from '@nestjs/common';
+import { DataSource, Repository } from 'typeorm';
+import { Character } from '../characters/entities/character.entity';
+import { LocationConnection } from '../world/entities/location-connection.entity';
+import { LocationDefinition } from '../world/entities/location-definition.entity';
+import { CLOCK } from './clock';
+import type { Clock } from './clock';
+import { Travel } from './entities/travel.entity';
+import {
+  characterNotFound,
+  invalidTravelState,
+  invalidTravelTarget,
+  travelAlreadyActive,
+} from './travel.errors';
+import { TravelStatus } from './travel-status.enum';
+
+export interface LocationSummary {
+  id: string;
+  key: string;
+  name: string;
+}
+
+export interface IdleTravelResponse {
+  status: 'IDLE';
+}
+
+export interface TravellingResponse {
+  status: TravelStatus.TRAVELLING;
+  originLocation: LocationSummary;
+  targetLocation: LocationSummary;
+  startedAt: Date;
+  arrivesAt: Date;
+}
+
+export interface CompletedTravelResponse {
+  status: TravelStatus.COMPLETED;
+  targetLocation: LocationSummary;
+}
+
+export type CurrentTravelResponse =
+  IdleTravelResponse | TravellingResponse | CompletedTravelResponse;
+
+@Injectable()
+export class TravelService {
+  constructor(
+    private readonly dataSource: DataSource,
+    @Inject(CLOCK) private readonly clock: Clock,
+  ) {}
+
+  startTravel(
+    characterId: string,
+    targetLocationId: string,
+  ): Promise<TravellingResponse> {
+    return this.dataSource.transaction(async (manager) => {
+      const characters = manager.getRepository(Character);
+      const travels = manager.getRepository(Travel);
+      const locations = manager.getRepository(LocationDefinition);
+      const connections = manager.getRepository(LocationConnection);
+
+      const character = await this.lockCharacter(characters, characterId);
+      const activeTravel = await this.lockActiveTravel(travels, characterId);
+      if (activeTravel) {
+        throw travelAlreadyActive();
+      }
+
+      const targetLocation = await locations.findOneBy({
+        id: targetLocationId,
+      });
+      if (!targetLocation) {
+        throw invalidTravelTarget();
+      }
+
+      const connection = await connections.findOneBy({
+        fromLocationId: character.currentLocationId,
+        toLocationId: targetLocationId,
+        enabled: true,
+      });
+      if (!connection) {
+        throw invalidTravelTarget();
+      }
+
+      const originLocation = await locations.findOneBy({
+        id: character.currentLocationId,
+      });
+      if (!originLocation) {
+        throw invalidTravelState();
+      }
+
+      const startedAt = new Date(this.clock.now().getTime());
+      const arrivesAt = new Date(
+        startedAt.getTime() + connection.travelDurationSeconds * 1000,
+      );
+      const travel = travels.create({
+        characterId,
+        originLocationId: character.currentLocationId,
+        targetLocationId,
+        startedAt,
+        arrivesAt,
+        status: TravelStatus.TRAVELLING,
+      });
+      await travels.save(travel);
+
+      return this.toTravellingResponse(travel, originLocation, targetLocation);
+    });
+  }
+
+  async getCurrentTravel(characterId: string): Promise<CurrentTravelResponse> {
+    const travels = this.dataSource.getRepository(Travel);
+    const travel = await travels.findOneBy({
+      characterId,
+      status: TravelStatus.TRAVELLING,
+    });
+    if (!travel) {
+      return { status: 'IDLE' };
+    }
+
+    const locations = this.dataSource.getRepository(LocationDefinition);
+    const { originLocation, targetLocation } = await this.loadTravelLocations(
+      locations,
+      travel,
+    );
+    return this.toTravellingResponse(travel, originLocation, targetLocation);
+  }
+
+  completeTravelIfDue(characterId: string): Promise<CurrentTravelResponse> {
+    return this.dataSource.transaction(async (manager) => {
+      const characters = manager.getRepository(Character);
+      const travels = manager.getRepository(Travel);
+      const locations = manager.getRepository(LocationDefinition);
+
+      const character = await this.lockCharacter(characters, characterId);
+      const travel = await this.lockActiveTravel(travels, characterId);
+      if (!travel) {
+        return { status: 'IDLE' };
+      }
+
+      const { originLocation, targetLocation } = await this.loadTravelLocations(
+        locations,
+        travel,
+      );
+      const now = this.clock.now();
+      if (travel.arrivesAt.getTime() > now.getTime()) {
+        return this.toTravellingResponse(
+          travel,
+          originLocation,
+          targetLocation,
+        );
+      }
+
+      travel.status = TravelStatus.COMPLETED;
+      character.currentLocationId = travel.targetLocationId;
+      await travels.save(travel);
+      await characters.save(character);
+
+      return {
+        status: TravelStatus.COMPLETED,
+        targetLocation: this.toLocationSummary(targetLocation),
+      };
+    });
+  }
+
+  private async lockCharacter(
+    characters: Repository<Character>,
+    characterId: string,
+  ): Promise<Character> {
+    const character = await characters.findOne({
+      where: { id: characterId },
+      lock: { mode: 'pessimistic_write' },
+    });
+    if (!character) {
+      throw characterNotFound();
+    }
+    return character;
+  }
+
+  private lockActiveTravel(
+    travels: Repository<Travel>,
+    characterId: string,
+  ): Promise<Travel | null> {
+    return travels.findOne({
+      where: { characterId, status: TravelStatus.TRAVELLING },
+      lock: { mode: 'pessimistic_write' },
+    });
+  }
+
+  private async loadTravelLocations(
+    locations: Repository<LocationDefinition>,
+    travel: Travel,
+  ): Promise<{
+    originLocation: LocationDefinition;
+    targetLocation: LocationDefinition;
+  }> {
+    const [originLocation, targetLocation] = await Promise.all([
+      locations.findOneBy({ id: travel.originLocationId }),
+      locations.findOneBy({ id: travel.targetLocationId }),
+    ]);
+    if (!originLocation || !targetLocation) {
+      throw invalidTravelState();
+    }
+    return { originLocation, targetLocation };
+  }
+
+  private toTravellingResponse(
+    travel: Travel,
+    originLocation: LocationDefinition,
+    targetLocation: LocationDefinition,
+  ): TravellingResponse {
+    return {
+      status: TravelStatus.TRAVELLING,
+      originLocation: this.toLocationSummary(originLocation),
+      targetLocation: this.toLocationSummary(targetLocation),
+      startedAt: travel.startedAt,
+      arrivesAt: travel.arrivesAt,
+    };
+  }
+
+  private toLocationSummary(location: LocationDefinition): LocationSummary {
+    return {
+      id: location.id,
+      key: location.key,
+      name: location.name,
+    };
+  }
+}