/**
 * Task D11 - Snap-Erweiterungen: tangent, perpendicular, quadrant, fromOffset.
 *
 * quadrant: Kreis-Quadrantenpunkte (0/90/180/270 auf dem Radius).
 * perpendicular: Fuspunkt auf Linie senkrecht zum Referenzpunkt.
 * tangent: Tangentialpunkte am Kreis vom Referenzpunkt.
 * fromOffset: Basispunkt + dx/dy-Eingabefeld.
 */
import { describe, it, expect } from 'vitest';
import { SnapEngine, fromOffset, type SnapConfig } from '../src/canvas/SnapEngine';
import type { CADElement } from '../src/types/cad.types';

function cfg(modes: string[], extra: Partial<SnapConfig> = {}): Partial<SnapConfig> {
  return {
    enabled: true,
    modes: new Set(modes as never),
    tolerance: 10,
    ...extra,
  };
}

function circle(id: string, cx: number, cy: number, r: number): CADElement {
  return {
    id, type: 'circle', layerId: 'l',
    x: cx, y: cy, width: r * 2, height: r * 2,
    properties: { radius: r },
  } as unknown as CADElement;
}

function line(id: string, x1: number, y1: number, x2: number, y2: number): CADElement {
  return {
    id, type: 'line', layerId: 'l',
    x: (x1 + x2) / 2, y: (y1 + y2) / 2,
    width: Math.abs(x2 - x1), height: Math.abs(y2 - y1),
    properties: { x1, y1, x2, y2 },
  } as unknown as CADElement;
}

// ─── Quadrant ──────────────────────────────────────────────

describe('D11: quadrant snap', () => {
  it('Kreis r=50: alle 4 Quadrantenpunkte werden geliefert', () => {
    const eng = new SnapEngine(cfg(['quadrant']));
    eng.setElements([circle('c1', 100, 100, 50)]);
    // Cursor in der Naehe des 0-Quadranten (150,100)
    const res = eng.snap(148, 100);
    expect(res.point).not.toBeNull();
    expect(res.point!.type).toBe('quadrant');
    expect(res.point!.x).toBe(150);
    expect(res.point!.y).toBe(100);
  });

  it('90-Quadrant (100,50) wird gefunden', () => {
    const eng = new SnapEngine(cfg(['quadrant']));
    eng.setElements([circle('c1', 100, 100, 50)]);
    const res = eng.snap(100, 52);
    expect(res.point!.x).toBe(100);
    expect(res.point!.y).toBe(50);
    expect(res.point!.type).toBe('quadrant');
  });

  it('270-Quadrant (unten) wird gefunden', () => {
    const eng = new SnapEngine(cfg(['quadrant']));
    eng.setElements([circle('c1', 100, 100, 50)]);
    const res = eng.snap(100, 148);
    expect(res.point!.y).toBe(150);
    expect(res.point!.type).toBe('quadrant');
  });

  it('Modus nicht aktiviert -> kein quadrant snap', () => {
    const eng = new SnapEngine(cfg(['endpoint']));
    eng.setElements([circle('c1', 100, 100, 50)]);
    const res = eng.snap(148, 100);
    expect(res.point?.type ?? null).not.toBe('quadrant');
  });
});

// ─── Perpendicular ─────────────────────────────────────────

describe('D11: perpendicular snap', () => {
  it('Fuspunkt senkrecht vom refPoint auf horizontale Linie', () => {
    const eng = new SnapEngine(cfg(['perpendicular']));
    // Horizontale Linie y=100, refPoint (50,50): Fuspunkt (50,100)
    eng.setElements([line('l1', 0, 100, 200, 100)]);
    const res = eng.snap(52, 98, { x: 50, y: 50 });
    expect(res.point).not.toBeNull();
    expect(res.point!.type).toBe('perpendicular');
    expect(res.point!.x).toBe(50);
    expect(res.point!.y).toBe(100);
  });

  it('Schrge Linie: Fuspunkt berechnet', () => {
    const eng = new SnapEngine(cfg(['perpendicular']));
    // Linie (0,0)-(100,100), refPoint (100,0): Fuspunkt (50,50)
    eng.setElements([line('l1', 0, 0, 100, 100)]);
    const res = eng.snap(51, 49, { x: 100, y: 0 });
    expect(res.point!.x).toBeCloseTo(50, 0);
    expect(res.point!.y).toBeCloseTo(50, 0);
  });

  it('ohne refPoint kein perpendicular snap (Modus still)', () => {
    const eng = new SnapEngine(cfg(['perpendicular']));
    eng.setElements([line('l1', 0, 100, 200, 100)]);
    const res = eng.snap(50, 98);
    expect(res.point?.type ?? null).not.toBe('perpendicular');
  });
});

// ─── Tangent ───────────────────────────────────────────────

describe('D11: tangent snap', () => {
  it('Tangentialpunkt am Kreis von refPoint (rechts vom Kreis)', () => {
    const eng = new SnapEngine(cfg(['tangent']));
    // Kreis (100,100) r=50, refPoint (200,100), d=100:
    // halfAng = acos(r/d) = 60° → Tangentenpunkte bei (125, 143.3)/(125, 56.7)
    eng.setElements([circle('c1', 100, 100, 50)]);
    const res = eng.snap(127, 145, { x: 200, y: 100 });
    expect(res.point).not.toBeNull();
    expect(res.point!.type).toBe('tangent');
    expect(res.point!.x).toBeCloseTo(125, 0);
    expect(res.point!.y).toBeCloseTo(143.3, 0);
  });

  it('refPoint AUF dem Kreiszentrum -> kein Tangentenpunkt (degeneriert)', () => {
    const eng = new SnapEngine(cfg(['tangent']));
    eng.setElements([circle('c1', 100, 100, 50)]);
    const res = eng.snap(148, 100, { x: 100, y: 100 });
    expect(res.point?.type ?? null).not.toBe('tangent');
  });
});

// ─── fromOffset ────────────────────────────────────────────

describe('D11: fromOffset', () => {
  it('Basispunkt + dx/dy ergibt Zielpunkt', () => {
    const p = fromOffset({ x: 100, y: 200 }, 50, -30);
    expect(p).toEqual({ x: 150, y: 170 });
  });

  it('dx=dy=0 bleibt am Basispunkt', () => {
    const p = fromOffset({ x: 10, y: 20 }, 0, 0);
    expect(p).toEqual({ x: 10, y: 20 });
  });

  it('negative Offsets funktionieren', () => {
    const p = fromOffset({ x: 0, y: 0 }, -100, -50);
    expect(p).toEqual({ x: -100, y: -50 });
  });
});