import { content } from "@deadhead/content";
import { describe, expect, it } from "vitest";
import {
  economicDistance,
  fuelCost,
  fullTankReach,
  legFuel,
  plainDistance,
  routeDistance,
} from "../src/index";

const { config } = content;
const courier = content.shipModel("courier")!;
const earth = content.location("earth")!;
const moon = content.location("moon")!;
const { referenceMillionKm: ref, exponent } = config.economicDistance;

describe("economic distance (decision 0.5.84)", () => {
  it("leaves an Earth–Moon length leg unchanged", () => {
    expect(economicDistance(ref, config)).toBeCloseTo(ref);
  });

  it("grows more slowly than distance past the reference, and keeps order", () => {
    expect(economicDistance(130, config)).toBeLessThan(130);
    expect(economicDistance(130, config)).toBeGreaterThan(economicDistance(60, config));
    // Doubling the distance multiplies it by 2^exponent.
    expect(economicDistance(20, config) / economicDistance(10, config)).toBeCloseTo(2 ** exponent);
  });

  it("is the plain distance with an exponent of 1", () => {
    const linear = { ...config, economicDistance: { referenceMillionKm: ref, exponent: 1 } };
    expect(economicDistance(130, linear)).toBeCloseTo(130);
  });
});

describe("fuel cost", () => {
  it("costs more Earth→Moon than Moon→Earth for the same ship", () => {
    const distance = routeDistance(earth, moon);
    expect(fuelCost(courier, earth, distance, config)).toBeGreaterThan(
      fuelCost(courier, moon, distance, config),
    );
  });

  it("scales with economic distance", () => {
    expect(fuelCost(courier, earth, 10, config) / fuelCost(courier, earth, 5, config)).toBeCloseTo(
      2 ** exponent,
    );
  });

  it("matches a hand calculation (Step 15.3: the leg's fuel at the origin's price)", () => {
    // 20 fu per M km × economic distance of 0.5M km, at 10 cr/fu × Earth's 1.6.
    const expected = 20 * ref * (0.5 / ref) ** exponent * 10 * 1.6;
    expect(fuelCost(courier, earth, 0.5, config)).toBeCloseTo(expected);
  });
});

describe("tanks and reach (decisions 0.5.94, 0.5.95)", () => {
  it("burns the burn rate × the economic distance of the leg ÷ the origin's range factor", () => {
    expect(legFuel(courier, earth, 0.5, config)).toBeCloseTo(20 * economicDistance(0.5, config));
    expect(legFuel(courier, moon, 0.5, config)).toBeCloseTo(
      20 * economicDistance(0.5 / 1.3, config),
    );
  });

  it("inverts the economic-distance curve", () => {
    for (const d of [0.2, 0.384, 5, 201, 792]) {
      expect(plainDistance(economicDistance(d, config), config)).toBeCloseTo(d, 6);
    }
  });

  it("reaches exactly as far as a full tank burns, stretched by the origin's factor", () => {
    for (const origin of content.locations) {
      for (const ship of content.shipModels) {
        const reach = fullTankReach(ship, origin, config);
        expect(legFuel(ship, origin, reach, config), `${ship.id} from ${origin.id}`).toBeCloseTo(
          ship.tankCapacityFu,
          6,
        );
        expect(reach).toBeCloseTo(fullTankReach(ship, earth, config) * origin.launchRangeFactor, 6);
      }
    }
  });
});