From 91d394dfc9bfa18e60031bbe1507e14e017240f3 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Sun, 7 Apr 2024 23:04:38 +0200
Subject: [node] Implemented multi hops in system navigation

---
 nodejs/lib/ships.ts | 31 +++++++++++++++++++++----------
 nodejs/lib/utils.ts | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/nodejs/lib/ships.ts b/nodejs/lib/ships.ts
index 67dca00..4ae64c7 100644
--- a/nodejs/lib/ships.ts
+++ b/nodejs/lib/ships.ts
@@ -10,6 +10,7 @@ import {
 	ShipIsStillOnCooldownError,
 	ShipRequiresMoreFuelForNavigationError,
 } from './errors.ts';
+import * as libSystems from './systems.ts';
 import {
 	Agent,
 	Cargo,
@@ -20,7 +21,11 @@ import {
 	Registration,
 	Waypoint,
 } from './types.ts';
+import {
+	shortestPath,
+} from './utils.ts';
 import * as dbAgents from '../database/agents.ts';
+import * as dbContracts from '../database/contracts.ts';
 
 export async function getShips(): Promise<Array<Ship>> {
 	const response = await send<Array<Ship>>({endpoint: `/my/ships`, page: 1});
@@ -98,26 +103,32 @@ export class Ship {
 		return this.cargo.units >= this.cargo.capacity * 0.9;
 	}
 	async navigate(waypoint: Waypoint): Promise<void> {
-		if (this.nav.waypointSymbol === waypoint.symbol) return;
-		// TODO compute fuel consumption and refuel if we do not have enough OR if the destination does not sell fuel?
-		await this.refuel();
+		let path = shortestPath(await libSystems.waypoint(this.nav.route.destination.symbol), waypoint, this.fuel.capacity, await libSystems.waypoints(this.nav.systemSymbol));
+		while (path.length > 0) {
+			const next = path.pop();
+			if (next === undefined) break;
+			if (next.fuel > this.fuel.current) {
+				// TODO also refuel if the destination does not sell fuel?
+				await this.refuel();
+			}
+			await this.navigateTo(next.symbol);
+		}
+	}
+	private async navigateTo(symbol: string): Promise<void> {
 		await this.orbit();
-		// TODO if we do not have enough fuel, make a stop to refuel along the way or drift to the destination
-		const response = await send<{fuel: Fuel, nav: Nav}>({endpoint: `/my/ships/${this.symbol}/navigate`, method: 'POST', payload: { waypointSymbol: waypoint.symbol }}); // TODO events field
+		const response = await send<{fuel: Fuel, nav: Nav}>({endpoint: `/my/ships/${this.symbol}/navigate`, method: 'POST', payload: { waypointSymbol: symbol }}); // TODO events field
 		if (response.error) {
 			switch(response.error.code) {
 				case 4203: // not enough fuel
+					// This should not happen given the logic in navigate()
 					const srmffne = response.error.data as ShipRequiresMoreFuelForNavigationError;
-					// TODO test if it exceeds our maximum
-					// find an intermediate stop to refuel if that is the case
 					debugLog(response);
+					debugLog(srmffne);
 					throw response;
-					//await refuel(ship);
-					//return await navigate(ship, waypoint);
 				case 4214:
 					const sicite = response.error.data as ShipIsCurrentlyInTransitError;
 					await sleep(sicite.secondsToArrival * 1000);
-					return await this.navigate(waypoint);
+					return await this.navigateTo(symbol);
 				default: // yet unhandled error
 					debugLog(response);
 					throw response;
diff --git a/nodejs/lib/utils.ts b/nodejs/lib/utils.ts
index 480e7a4..c8f3d7f 100644
--- a/nodejs/lib/utils.ts
+++ b/nodejs/lib/utils.ts
@@ -1,4 +1,9 @@
-import { Cargo, CargoManifest } from './types.ts';
+import { PriorityQueue } from './priority_queue.ts';
+import {
+	Cargo,
+	CargoManifest,
+	Waypoint,
+} from './types.ts';
 
 export type CategorizedCargo = {
 	wanted: CargoManifest;
@@ -45,6 +50,47 @@ export function sortByDistanceFrom<T extends Point>(a: Point, points: Array<T>):
 	return result;
 }
 
+type Step = {waypoint: Waypoint, prev: string, fuel: number, total: number};
+type ShortestPath = Array<{symbol: string, fuel: number}>;
+
+export function shortestPath(origin: Waypoint, destination: Waypoint, range: number, waypoints: Array<Waypoint>): ShortestPath {
+	let backtrace: {[key: string]: Step} = {};
+	let fuels: {[key: string]: number} = {}; // fuel = distance + 1 per hop
+	let unvisited: {[key: string]: Waypoint} = {};
+	waypoints.forEach(function(w) {
+		fuels[w.symbol] = Infinity;
+		unvisited[w.symbol] = w;
+	});
+	fuels[origin.symbol] = 0;
+	let queue = new PriorityQueue();
+	queue.enqueue({waypoint: origin, prev: origin.symbol, fuel: 0, total: 0}, 0);
+	while(!queue.isEmpty()) {
+		let step = queue.dequeue() as Step;
+		const symbol = step.waypoint.symbol;
+		if (!(symbol in unvisited)) continue;
+		backtrace[symbol] = step;
+		if (symbol === destination.symbol) break;
+		const prev = unvisited[symbol];
+		delete unvisited[symbol];
+		for(const ws in unvisited) {
+			const w = unvisited[ws];
+			const f = distance(prev, w) + 1;
+			if (f > range) continue;
+			const total = step.fuel + f;
+			if (fuels[ws] > total) {
+				fuels[ws] = total;
+				queue.enqueue({waypoint: w, prev: symbol, fuel: f, total: total}, total);
+			}
+		}
+	}
+	let result: ShortestPath = [];
+	for (let step = backtrace[destination.symbol]; step.waypoint.symbol != origin.symbol; step = backtrace[step.prev]) {
+		if (step === undefined) throw `Cannot compute shortest path from ${origin.symbol} to ${destination.symbol} with range ${range}.`;
+		result.push({symbol: step.waypoint.symbol, fuel: step.fuel});
+	}
+	return result;
+}
+
 export function systemFromWaypoint(waypoint: string): string {
 	return waypoint.split('-').slice(0,2).join('-');
 }
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