import { describe, expect, it } from "vitest";
import {
  ACCURACY_BONUS_MAX,
  AIM_TRAINER_DIFFICULTIES,
  CIVILIAN_PENALTY,
  COMPLETION_XP,
  COURSE_DURATION_MS,
  HEADSHOT_POINTS,
  MAX_CONCURRENT_CIVILIANS,
  MAX_CIVILIAN_HITS,
  MAX_DESPAWNED_TARGETS,
  MAX_HITS,
  MAX_SHOTS_FIRED,
  NEW_TIER_RECORD_XP,
  POINTS_PER_XP,
  SCORE_XP_RATE,
  TORSO_POINTS,
  XP_CAP,
  type AimTrainerTarget,
  aimTrainerTargetBounds,
  boundsOverlap,
  calculateAimTrainerAccuracy,
  calculateAimTrainerScore,
  calculateAimTrainerXp,
  createAimTrainerTarget,
  isAimTrainerDifficulty,
  resolveAimTrainerHitZone,
  resolveAimTrainerTargetCollisions,
  resolveAimTrainerTargetHit,
  stepAimTrainerTarget,
  stepAimTrainerTargets,
} from "@/lib/aim-trainer";

/** Deterministic LCG-style RNG so target creation is reproducible across runs. */
function seededRng(seed: number): () => number {
  let state = seed >>> 0;
  return () => {
    state = (state * 1664525 + 1013904223) >>> 0;
    return state / 0x100000000;
  };
}

describe("Aim Trainer constants", () => {
  it("exposes the course duration and scoring constants", () => {
    expect(COURSE_DURATION_MS).toBe(30_000);
    expect(TORSO_POINTS).toBe(100);
    expect(HEADSHOT_POINTS).toBe(250);
    expect(CIVILIAN_PENALTY).toBe(100);
    expect(ACCURACY_BONUS_MAX).toBe(500);
    expect(POINTS_PER_XP).toBe(500);
    expect(SCORE_XP_RATE).toBe(0.125);
    expect(COMPLETION_XP).toBe(1);
    expect(NEW_TIER_RECORD_XP).toBe(2);
    expect(XP_CAP).toBe(50);
  });

  it("exposes the server safety caps", () => {
    expect(MAX_SHOTS_FIRED).toBe(500);
    expect(MAX_HITS).toBe(180);
    expect(MAX_DESPAWNED_TARGETS).toBe(60);
    expect(MAX_CONCURRENT_CIVILIANS).toBe(1);
    expect(MAX_CIVILIAN_HITS).toBe(30);
  });
});

describe("AIM_TRAINER_DIFFICULTIES", () => {
  it("defines exactly the three tiers with the specified values", () => {
    expect(AIM_TRAINER_DIFFICULTIES).toEqual({
      recruit: {
        torsoW: 76,
        torsoH: 118,
        headRadius: 21,
        movingRatio: 0.25,
        speed: 80,
        targetLifetimeMs: 2000,
        replacementDelayMs: 400,
        maxConcurrentTargets: 1,
        civilianChance: 0.2,
      },
      veteran: {
        torsoW: 62,
        torsoH: 100,
        headRadius: 18,
        movingRatio: 0.55,
        speed: 140,
        targetLifetimeMs: 1500,
        replacementDelayMs: 300,
        maxConcurrentTargets: 2,
        civilianChance: 0.3,
      },
      elite: {
        torsoW: 50,
        torsoH: 82,
        headRadius: 15,
        movingRatio: 0.8,
        speed: 220,
        targetLifetimeMs: 1100,
        replacementDelayMs: 200,
        maxConcurrentTargets: 2,
        civilianChance: 0.35,
      },
    });
  });

  it("asserts every field of every tier explicitly", () => {
    const recruit = AIM_TRAINER_DIFFICULTIES.recruit;
    expect(recruit.torsoW).toBe(76);
    expect(recruit.torsoH).toBe(118);
    expect(recruit.headRadius).toBe(21);
    expect(recruit.movingRatio).toBe(0.25);
    expect(recruit.speed).toBe(80);
    expect(recruit.targetLifetimeMs).toBe(2000);
    expect(recruit.replacementDelayMs).toBe(400);
    expect(recruit.maxConcurrentTargets).toBe(1);
    expect(recruit.civilianChance).toBe(0.2);

    const veteran = AIM_TRAINER_DIFFICULTIES.veteran;
    expect(veteran.torsoW).toBe(62);
    expect(veteran.torsoH).toBe(100);
    expect(veteran.headRadius).toBe(18);
    expect(veteran.movingRatio).toBe(0.55);
    expect(veteran.speed).toBe(140);
    expect(veteran.targetLifetimeMs).toBe(1500);
    expect(veteran.replacementDelayMs).toBe(300);
    expect(veteran.maxConcurrentTargets).toBe(2);
    expect(veteran.civilianChance).toBe(0.3);

    const elite = AIM_TRAINER_DIFFICULTIES.elite;
    expect(elite.torsoW).toBe(50);
    expect(elite.torsoH).toBe(82);
    expect(elite.headRadius).toBe(15);
    expect(elite.movingRatio).toBe(0.8);
    expect(elite.speed).toBe(220);
    expect(elite.targetLifetimeMs).toBe(1100);
    expect(elite.replacementDelayMs).toBe(200);
    expect(elite.maxConcurrentTargets).toBe(2);
    expect(elite.civilianChance).toBe(0.35);
  });
});

describe("isAimTrainerDifficulty", () => {
  it("accepts the three valid tiers", () => {
    expect(isAimTrainerDifficulty("recruit")).toBe(true);
    expect(isAimTrainerDifficulty("veteran")).toBe(true);
    expect(isAimTrainerDifficulty("elite")).toBe(true);
  });

  it("rejects unknown values", () => {
    expect(isAimTrainerDifficulty("legendary")).toBe(false);
    expect(isAimTrainerDifficulty("")).toBe(false);
    expect(isAimTrainerDifficulty(42)).toBe(false);
    expect(isAimTrainerDifficulty(null)).toBe(false);
    expect(isAimTrainerDifficulty(undefined)).toBe(false);
    expect(isAimTrainerDifficulty({})).toBe(false);
  });
});

describe("calculateAimTrainerAccuracy", () => {
  it("returns 0 when there were zero attempts", () => {
    expect(calculateAimTrainerAccuracy(0, 0, 0)).toBe(0);
  });

  it("counts hits against shots fired plus despawned unhit targets", () => {
    // 3 hits, 3 shots, 1 despawned unhit target -> 3 / 4
    expect(calculateAimTrainerAccuracy(3, 3, 1)).toBeCloseTo(0.75);
  });

  it("clamps the result to the [0, 1] range", () => {
    expect(calculateAimTrainerAccuracy(10, 2, 0)).toBe(1);
    expect(calculateAimTrainerAccuracy(0, 5, 5)).toBe(0);
  });
});

describe("calculateAimTrainerScore", () => {
  it("scores headshots, torso hits, and the accuracy bonus", () => {
    // 2 headshots + 1 torso, 3 shots fired, 1 despawned unhit target.
    // Hit score = 2*250 + 1*100 = 600. Accuracy = 3/4. Bonus = round(0.75*500) = 375. Total 975.
    expect(calculateAimTrainerScore(2, 1, 3, 1)).toBe(975);
  });

  it("scores a perfect run with no accuracy penalty", () => {
    // 1 headshot, 1 shot, no despawned targets -> 250 + round(1*500) = 750.
    expect(calculateAimTrainerScore(1, 0, 1, 0)).toBe(750);
  });

  it("subtracts the civilian penalty from the hit score", () => {
    // 1 headshot + 1 torso = 350, minus 2 civilian hits = -200.
    // Accuracy counts only real hits: 2/2 shots -> round(1*500) = 500. Total 650.
    expect(calculateAimTrainerScore(1, 1, 2, 0, 2)).toBe(650);
  });

  it("clamps the total to zero when civilian penalties outweigh the hits", () => {
    // No real hits, 3 civilian hits -> -300 + round(0*500) clamped to 0.
    expect(calculateAimTrainerScore(0, 0, 3, 0, 3)).toBe(0);
  });

  it("excludes civilian hits from the accuracy denominator numerator", () => {
    // 1 torso + 1 civilian, 2 shots: accuracy = 1/2 (civilian not a hit).
    // 100 - 100 + round(0.5*500) = 250.
    expect(calculateAimTrainerScore(0, 1, 2, 0, 1)).toBe(250);
  });
});

describe("calculateAimTrainerXp", () => {
  it("awards the completion XP for a zero score", () => {
    expect(calculateAimTrainerXp(0, false)).toBe(1);
  });

  it("awards completion XP plus 0.125 per full 500 points", () => {
    expect(calculateAimTrainerXp(499, false)).toBe(1);
    expect(calculateAimTrainerXp(500, false)).toBe(1.125);
    expect(calculateAimTrainerXp(999, false)).toBe(1.125);
    expect(calculateAimTrainerXp(1000, false)).toBe(1.25);
  });

  it("adds the new-tier-best bonus", () => {
    expect(calculateAimTrainerXp(0, true)).toBe(3);
    expect(calculateAimTrainerXp(500, true)).toBe(3.125);
  });

  it("caps the result at XP_CAP", () => {
    expect(calculateAimTrainerXp(1_000_000, true)).toBe(50);
    expect(calculateAimTrainerXp(1_000_000, false)).toBe(50);
  });
});

describe("createAimTrainerTarget", () => {
  const canvasW = 800;
  const canvasH = 600;

  it("returns a target with the tier's dimensions and a deterministic position", () => {
    const rng = seededRng(1234);
    const target = createAimTrainerTarget(rng, canvasW, canvasH, "veteran");
    expect(target.torsoW).toBe(62);
    expect(target.torsoH).toBe(100);
    expect(target.headRadius).toBe(18);
    expect(typeof target.moving).toBe("boolean");
    expect(typeof target.x).toBe("number");
    expect(typeof target.y).toBe("number");
    expect(typeof target.vx).toBe("number");
    expect(typeof target.vy).toBe("number");
    expect(target.kind).toBe("standard");
  });

  it("marks civilian targets when requested", () => {
    const target = createAimTrainerTarget(seededRng(7), canvasW, canvasH, "veteran", {
      civilian: true,
    });
    expect(target.kind).toBe("civilian");
  });

  it("avoids spawning on top of existing targets", () => {
    const blocker: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: 0,
      vy: 0,
      moving: false,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    for (let seed = 0; seed < 50; seed++) {
      const target = createAimTrainerTarget(seededRng(seed), canvasW, canvasH, "veteran", {
        existingTargets: [blocker],
      });
      expect(
        boundsOverlap(aimTrainerTargetBounds(target), aimTrainerTargetBounds(blocker)),
      ).toBe(false);
    }
  });

  it("is deterministic for the same seed across repeated calls", () => {
    // Given: a fixed seed for Elite target generation.
    const seed = 42;

    // When: identical seeded streams each generate their first target.
    const a = createAimTrainerTarget(seededRng(seed), canvasW, canvasH, "elite");
    const b = createAimTrainerTarget(seededRng(seed), canvasW, canvasH, "elite");

    // Then: the complete targets match and the moving target has the balanced Elite speed.
    expect(a).toEqual(b);
    expect(a.moving).toBe(true);
    expect(Math.hypot(a.vx, a.vy)).toBeCloseTo(220);
  });

  it("keeps the whole target (torso plus head) inside the canvas", () => {
    for (let seed = 0; seed < 200; seed++) {
      const target = createAimTrainerTarget(seededRng(seed), canvasW, canvasH, "recruit");
      const left = target.x - target.torsoW / 2;
      const right = target.x + target.torsoW / 2;
      const top = target.y - 2 * target.headRadius;
      const bottom = target.y + target.torsoH;
      expect(left).toBeGreaterThanOrEqual(0);
      expect(right).toBeLessThanOrEqual(canvasW);
      expect(top).toBeGreaterThanOrEqual(0);
      expect(bottom).toBeLessThanOrEqual(canvasH);
    }
  });

  it("selects moving vs stationary based on the RNG roll against movingRatio", () => {
    // A rng that always returns 0 -> always moving (0 < movingRatio).
    const alwaysMoving = createAimTrainerTarget(() => 0, canvasW, canvasH, "recruit");
    expect(alwaysMoving.moving).toBe(true);
    // A rng that always returns 1 -> never moving (1 < movingRatio is false).
    const neverMoving = createAimTrainerTarget(() => 1, canvasW, canvasH, "recruit");
    expect(neverMoving.moving).toBe(false);
  });

  it("gives stationary targets zero velocity", () => {
    const stationary = createAimTrainerTarget(() => 1, canvasW, canvasH, "veteran");
    expect(stationary.moving).toBe(false);
    expect(stationary.vx).toBe(0);
    expect(stationary.vy).toBe(0);
  });
});

describe("resolveAimTrainerHitZone", () => {
  const target: AimTrainerTarget = {
    x: 400,
    y: 300,
    vx: 0,
    vy: 0,
    moving: false,
    torsoW: 62,
    torsoH: 100,
    headRadius: 18,
    kind: "standard",
  };

  it("resolves a head hit inside the head circle", () => {
    // Head center is at (x, y - headRadius) = (400, 282).
    expect(resolveAimTrainerHitZone(target, 400, 282)).toBe("head");
  });

  it("resolves a torso hit inside the torso rectangle", () => {
    // Torso spans x in [369, 431], y in [300, 400].
    expect(resolveAimTrainerHitZone(target, 400, 350)).toBe("torso");
  });

  it("returns null for a miss outside both zones", () => {
    expect(resolveAimTrainerHitZone(target, 100, 100)).toBeNull();
  });

  it("checks the head zone before the torso rectangle", () => {
    // A point that is inside the head circle but also within the torso's x-range
    // must resolve to "head", proving head is checked first.
    expect(resolveAimTrainerHitZone(target, 400, 282)).toBe("head");
  });
});

describe("resolveAimTrainerTargetHit", () => {
  const rearTarget: AimTrainerTarget = {
    x: 400,
    y: 300,
    vx: 0,
    vy: 0,
    moving: false,
    torsoW: 62,
    torsoH: 100,
    headRadius: 18,
    kind: "standard",
  };
  const frontTarget: AimTrainerTarget = {
    ...rearTarget,
    y: 280,
  };

  it("resolves the topmost target first when ordered targets overlap", () => {
    // Given: index 1 is drawn above index 0, and (400, 282) hits its torso and index 0's head.
    const targets = [rearTarget, frontTarget];

    // When: the overlapping point is resolved against the ordered targets.
    const hit = resolveAimTrainerTargetHit(targets, 400, 282);

    // Then: the topmost target wins even though the lower target offers a headshot.
    expect(hit).toEqual({ index: 1, zone: "torso" });
  });

  it("returns null when every ordered target misses", () => {
    // Given: two overlapping targets whose complete geometry is away from the origin.
    const targets = [rearTarget, frontTarget];

    // When: a point outside every target is resolved.
    const hit = resolveAimTrainerTargetHit(targets, 0, 0);

    // Then: no target or zone is selected.
    expect(hit).toBeNull();
  });
});

describe("stepAimTrainerTarget", () => {
  const canvasW = 800;
  const canvasH = 600;

  it("moves a moving target by velocity times dt", () => {
    const target: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: 100,
      vy: 0,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    const stepped = stepAimTrainerTarget(target, 0.5, canvasW, canvasH);
    expect(stepped.x).toBeCloseTo(450);
    expect(stepped.y).toBeCloseTo(300);
  });

  it("leaves a stationary target in place", () => {
    const target: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: 100,
      vy: 50,
      moving: false,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    const stepped = stepAimTrainerTarget(target, 1, canvasW, canvasH);
    expect(stepped.x).toBe(400);
    expect(stepped.y).toBe(300);
  });

  it("bounces off the horizontal bounds and keeps the target inside", () => {
    const target: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: 1000,
      vy: 0,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    let current = target;
    for (let i = 0; i < 1000; i++) {
      current = stepAimTrainerTarget(current, 0.1, canvasW, canvasH);
      const left = current.x - current.torsoW / 2;
      const right = current.x + current.torsoW / 2;
      const top = current.y - 2 * current.headRadius;
      const bottom = current.y + current.torsoH;
      expect(left).toBeGreaterThanOrEqual(0);
      expect(right).toBeLessThanOrEqual(canvasW);
      expect(top).toBeGreaterThanOrEqual(0);
      expect(bottom).toBeLessThanOrEqual(canvasH);
    }
  });

  it("bounces off the vertical bounds and keeps the target inside", () => {
    const target: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: 0,
      vy: 1000,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    let current = target;
    for (let i = 0; i < 1000; i++) {
      current = stepAimTrainerTarget(current, 0.1, canvasW, canvasH);
      const top = current.y - 2 * current.headRadius;
      const bottom = current.y + current.torsoH;
      expect(top).toBeGreaterThanOrEqual(0);
      expect(bottom).toBeLessThanOrEqual(canvasH);
    }
  });
});

describe("resolveAimTrainerTargetCollisions", () => {
  const canvasW = 800;
  const canvasH = 600;

  it("bounces approaching targets apart without ever overlapping", () => {
    let a: AimTrainerTarget = {
      x: 300,
      y: 300,
      vx: 200,
      vy: 0,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    let b: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: -200,
      vy: 0,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    for (let i = 0; i < 200; i++) {
      const stepped = stepAimTrainerTargets([a, b], 0.05, canvasW, canvasH);
      if (!stepped[0] || !stepped[1]) throw new Error("expected two stepped targets");
      a = stepped[0];
      b = stepped[1];
      expect(boundsOverlap(aimTrainerTargetBounds(a), aimTrainerTargetBounds(b))).toBe(false);
    }
  });

  it("reflects velocity components that point into the other target", () => {
    const a: AimTrainerTarget = {
      x: 380,
      y: 300,
      vx: 100,
      vy: 0,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    const b: AimTrainerTarget = {
      x: 420,
      y: 300,
      vx: -100,
      vy: 0,
      moving: true,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    const resolved = resolveAimTrainerTargetCollisions([a, b], canvasW, canvasH);
    expect(resolved[0]?.vx).toBe(-100);
    expect(resolved[1]?.vx).toBe(100);
  });

  it("separates stationary targets without giving them velocity", () => {
    const a: AimTrainerTarget = {
      x: 400,
      y: 300,
      vx: 0,
      vy: 0,
      moving: false,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    const b: AimTrainerTarget = {
      x: 420,
      y: 300,
      vx: 0,
      vy: 0,
      moving: false,
      torsoW: 62,
      torsoH: 100,
      headRadius: 18,
      kind: "standard",
    };
    const resolved = resolveAimTrainerTargetCollisions([a, b], canvasW, canvasH);
    expect(resolved[0]?.vx).toBe(0);
    expect(resolved[0]?.vy).toBe(0);
    expect(resolved[1]?.vx).toBe(0);
    expect(resolved[1]?.vy).toBe(0);
  });
});