import { describe, it, expect } from 'vitest';
import { computeRouteLayout, travelledStopFor } from '../src/lib/roadmap-layout.js';

function isStrictlyIncreasing(xs: number[]): boolean {
  for (let i = 1; i < xs.length; i += 1) if (xs[i] <= xs[i - 1]) return false;
  return true;
}

describe('computeRouteLayout', () => {
  it('1 item — produces a valid single-point M path on the centreline', () => {
    const out = computeRouteLayout({ itemCount: 1, viewportWidth: 1000 });
    expect(out.itemX).toHaveLength(1);
    expect(out.midY).toBe(210); // trackHeight 420 / 2
    expect(out.itemY).toEqual([out.midY]);
    expect(out.cardSide).toEqual(['below']);
    expect(out.pathD.startsWith('M ')).toBe(true);
    expect(out.pathD).not.toContain('C ');
    // Target usable width = 1000 * 0.8 = 800; trackWidth = 800 + 60*2 = 920
    expect(out.trackWidth).toBe(920);
  });

  it('2 items — cards hang toward centreline (both below: i=0 centre, i=1 above-centre)', () => {
    const out = computeRouteLayout({ itemCount: 2, viewportWidth: 1000 });
    expect(out.itemX).toHaveLength(2);
    expect(isStrictlyIncreasing(out.itemX)).toBe(true);
    // i=0: centreline (below by convention). i=1: dot above centre → card below.
    expect(out.cardSide).toEqual(['below', 'below']);
    expect(out.pathD.startsWith('M ')).toBe(true);
    expect((out.pathD.match(/C /g) ?? []).length).toBe(1);
  });

  it('3 items — cards toward centreline; amplitude multiplier ramps', () => {
    const out = computeRouteLayout({ itemCount: 3, viewportWidth: 1000 });
    // i=0 centre (below), i=1 above-centre (card below), i=2 below-centre (card above).
    expect(out.cardSide).toEqual(['below', 'below', 'above']);
    expect(isStrictlyIncreasing(out.itemX)).toBe(true);
    // First item on centreline, second above (smaller y), third below.
    expect(out.itemY[0]).toBe(out.midY);
    expect(out.itemY[1]).toBeLessThan(out.midY);
    expect(out.itemY[2]).toBeGreaterThan(out.midY);
    expect(Math.abs(out.itemY[2] - out.midY)).toBeGreaterThan(Math.abs(out.itemY[1] - out.midY));
  });

  it('7 items — every card grows toward the centreline, never away from it', () => {
    const out = computeRouteLayout({ itemCount: 7, viewportWidth: 1200 });
    expect(out.itemX).toHaveLength(7);
    expect(isStrictlyIncreasing(out.itemX)).toBe(true);
    // i: 0 1 2 3 4 5 6 — odd indices dot-above-centre (card below), even
    // indices >0 dot-below-centre (card above). i=0 default below.
    expect(out.cardSide).toEqual(['below', 'below', 'above', 'below', 'above', 'below', 'above']);
    // Spot-check: every non-i=0 card's side is opposite to its dot's
    // offset from centre — i.e. cards always shrink toward midY.
    for (let i = 1; i < out.itemX.length; i += 1) {
      const dotAbove = out.itemY[i] < out.midY;
      if (dotAbove) expect(out.cardSide[i]).toBe('below');
      else          expect(out.cardSide[i]).toBe('above');
    }
    expect(out.pathD.startsWith('M ')).toBe(true);
    expect((out.pathD.match(/C /g) ?? []).length).toBe(6);
  });

  it('20 items — data-driven width wins over the 80% target', () => {
    const out = computeRouteLayout({ itemCount: 20, viewportWidth: 800 });
    expect(isStrictlyIncreasing(out.itemX)).toBe(true);
    // (20 - 1) * 320 + 60 * 2 = 6200; clearly beats 800 * 0.8 + 120 = 760.
    expect(out.trackWidth).toBe(6200);
  });

  it('few items on a wide viewport — track ≈ 80% of viewport + padding', () => {
    // 3 items at viewport 1400. Data-driven = 2 * 320 + 120 = 760.
    // 80% target = 1400 * 0.8 + 120 = 1240 — should win.
    const out = computeRouteLayout({ itemCount: 3, viewportWidth: 1400 });
    expect(out.trackWidth).toBe(1240);
  });
});

describe('travelledStopFor', () => {
  it('returns 0 when no items have shipped', () => {
    expect(travelledStopFor(['exploring', 'considering'])).toBe(0);
    expect(travelledStopFor([])).toBe(0);
  });

  it('returns (lastShippingIndex + 0.5) / itemCount', () => {
    // [shipping, shipping, in_beta, exploring] → lastShipping = 1 → (1.5)/4 = 0.375
    expect(travelledStopFor(['shipping', 'shipping', 'in_beta', 'exploring'])).toBeCloseTo(0.375, 5);
  });

  it('clamps to 0.98 when every item has shipped', () => {
    expect(travelledStopFor(['shipping', 'shipping', 'shipping'])).toBeCloseTo(0.833, 2);
    // even with 100 items all shipping, clamps to 0.98
    const allShipping = Array(100).fill('shipping') as ('shipping')[];
    expect(travelledStopFor(allShipping)).toBeLessThanOrEqual(0.98);
  });
});
