import { describe, expect, it } from "vitest";
import {
  GRID_COLS,
  GRID_ROWS,
  LAND_NAV_DIFFICULTIES,
  calculateScore,
  calculateXp,
  createCourse,
  gridRef,
  isLegCorrect,
  isOptionCorrect,
  isLandNavDifficulty,
} from "@/lib/land-nav";

function seededRng(seed: number) {
  let state = seed;
  return () => {
    state = (state * 1664525 + 1013904223) % 4294967296;
    return state / 4294967296;
  };
}

describe("land-nav lib", () => {
  it("guards the difficulty keys", () => {
    expect(isLandNavDifficulty("waypoint")).toBe(true);
    expect(isLandNavDifficulty("route")).toBe(true);
    expect(isLandNavDifficulty("expedition")).toBe(true);
    expect(isLandNavDifficulty("patrol")).toBe(false);
    expect(isLandNavDifficulty(42)).toBe(false);
  });

  it("creates a valid course for every difficulty", () => {
    for (const difficulty of ["waypoint", "route", "expedition"] as const) {
      const config = LAND_NAV_DIFFICULTIES[difficulty];
      const course = createCourse(difficulty, seededRng(1));
      expect(course.legs).toHaveLength(config.legs);
      expect(course.features).toHaveLength(config.features);
      expect(course.cols).toBe(GRID_COLS);
      expect(course.rows).toBe(GRID_ROWS);

      const featureCells = new Set(course.features.map((f) => `${f.col},${f.row}`));
      expect(featureCells.size).toBe(config.features);
      for (const feature of course.features) {
        expect(feature.col).toBeGreaterThanOrEqual(0);
        expect(feature.col).toBeLessThan(GRID_COLS);
        expect(feature.row).toBeGreaterThanOrEqual(0);
        expect(feature.row).toBeLessThan(GRID_ROWS);
        expect(feature.name.length).toBeGreaterThan(0);
      }

      for (const leg of course.legs) {
        expect(leg.prompt.length).toBeGreaterThan(0);
        expect(leg.answerCell.col).toBeGreaterThanOrEqual(0);
        expect(leg.answerCell.col).toBeLessThan(GRID_COLS);
        expect(leg.answerCell.row).toBeGreaterThanOrEqual(0);
        expect(leg.answerCell.row).toBeLessThan(GRID_ROWS);
        if (leg.kind === "azimuth") {
          expect(leg.azimuth).toBeGreaterThanOrEqual(0);
          expect(leg.azimuth).toBeLessThanOrEqual(359);
          expect(leg.distanceM).toBeGreaterThan(0);
          expect(leg.startCell).toBeDefined();
        }
        if (leg.kind === "identify") {
          expect(leg.options).toHaveLength(4);
          expect(new Set(leg.options).size).toBe(4);
        }
      }
    }
  });

  it("produces 6-figure grid references", () => {
    const course = createCourse("waypoint", seededRng(7));
    const ref = gridRef(course, { col: 0, row: 0 });
    expect(ref).toMatch(/^\d{6}$/);
    expect(ref).toBe(
      `${String(course.easting0).padStart(3, "0")}${String(course.northing0).padStart(3, "0")}`,
    );
  });

  it("scores passes higher than fails and awards XP only on a pass", () => {
    const passScore = calculateScore("route", 6, 60, true);
    const failScore = calculateScore("route", 2, 60, false);
    expect(passScore).toBeGreaterThan(failScore);
    const faster = calculateScore("route", 6, 30, true);
    expect(faster).toBeGreaterThanOrEqual(passScore);
    expect(calculateXp(passScore, true)).toBeGreaterThanOrEqual(1);
    expect(calculateXp(passScore, false)).toBe(0);
  });

  it("validates leg answers", () => {
    const course = createCourse("waypoint", seededRng(3));
    const locateLeg = course.legs.find((leg) => leg.kind === "locate");
    const identifyLeg = course.legs.find((leg) => leg.kind === "identify");
    expect(locateLeg).toBeDefined();
    expect(identifyLeg).toBeDefined();
    if (locateLeg) {
      expect(isLegCorrect(locateLeg, locateLeg.answerCell)).toBe(true);
      expect(isLegCorrect(locateLeg, { col: 0, row: 0 })).toBe(
        locateLeg.answerCell.col === 0 && locateLeg.answerCell.row === 0,
      );
    }
    if (identifyLeg) {
      const answerFeature = course.features.find((f) => f.id === identifyLeg.answerFeatureId);
      expect(answerFeature).toBeDefined();
      expect(isOptionCorrect(identifyLeg, course, answerFeature!.name)).toBe(true);
      const wrongOption = (identifyLeg.options ?? []).find(
        (option) => option !== answerFeature!.name,
      );
      expect(isOptionCorrect(identifyLeg, course, wrongOption ?? "")).toBe(false);
    }
  });

  it("generates declination legs on harder courses with a consistent conversion", () => {
    let seen = 0;
    for (let seed = 1; seed <= 40 && seen < 5; seed += 1) {
      const course = createCourse("expedition", seededRng(seed));
      const declLegs = course.legs.filter((leg) => leg.kind === "declination");
      seen += declLegs.length;
      for (const leg of declLegs) {
        expect(leg.declination).not.toBe(0);
        expect(leg.startCell).toBeDefined();
        const radians = ((leg.azimuth ?? 0) * Math.PI) / 180;
        const distanceCells = (leg.distanceM ?? 0) / 100;
        const dx = Math.round(Math.sin(radians) * distanceCells);
        const dy = -Math.round(Math.cos(radians) * distanceCells) || 0;
        expect(leg.answerCell.col - leg.startCell!.col).toBe(dx);
        expect(leg.answerCell.row - leg.startCell!.row).toBe(dy);
        expect(leg.prompt).toMatch(/declination/i);
      }
    }
    expect(seen).toBeGreaterThan(0);
  });

  it("never generates declination legs on the waypoint course", () => {
    for (let seed = 1; seed <= 20; seed += 1) {
      const course = createCourse("waypoint", seededRng(seed));
      expect(course.legs.every((leg) => leg.kind !== "declination")).toBe(true);
    }
  });
});