/**
 * ViewBox Stability Tests
 * 
 * Tests to detect and prevent unwanted viewBox changes during and after animation.
 * The gauge should NOT change its viewBox after initial render stabilizes,
 * unless there are actual prop changes or container resize events.
 * 
 * This test is designed to FAIL and expose the flickering issue where:
 * 1. Gauge renders and starts animating
 * 2. After animation completes, the viewBox changes causing a flicker
 * 3. Elements get re-rendered every animation cycle
 */

import { GaugeType } from '../types/GaugeComponentProps';
import { calculateLayoutFromMeasuredBounds, calculateTightLayout, isLayoutStable } from './coordinateSystem';

describe('ViewBox Stability Tests', () => {
  describe('ViewBox Should Not Change After Initial Render Stabilizes', () => {
    /**
     * This test simulates the two-pass rendering and checks if viewBox would change
     * if measured bounds are recalculated after animation completes.
     */
    it('should produce identical viewBox when measured bounds do not change', () => {
      const parentWidth = 300;
      const parentHeight = 200;
      const gaugeType = GaugeType.Semicircle;
      const arcWidth = 0.2;
      
      // Simulate Pass 1: Initial tight layout
      const pass1Layout = calculateTightLayout(
        parentWidth,
        parentHeight,
        gaugeType,
        arcWidth,
        0 // marginPercent
      );
      
      // Simulate measuring bounds after pass 1
      const measuredBounds = {
        width: pass1Layout.outerRadius * 2.1,  // typical measured width
        height: pass1Layout.outerRadius * 1.2, // typical measured height for semicircle
        x: -pass1Layout.outerRadius * 1.05,    // centered
        y: -pass1Layout.outerRadius * 0.9,     // extends up from center
      };
      
      // Simulate Pass 2: Layout from measured bounds
      const pass2Layout = calculateLayoutFromMeasuredBounds(
        parentWidth,
        parentHeight,
        measuredBounds,
        gaugeType,
        arcWidth,
        pass1Layout
      );
      
      // Store the viewBox from pass 2 as the "stable" state
      const stableViewBox = pass2Layout.viewBox.toString();
      
      // Simulate what happens after animation completes:
      // If the system recalculates using the same measured bounds,
      // the viewBox should be IDENTICAL
      const postAnimationLayout = calculateLayoutFromMeasuredBounds(
        parentWidth,
        parentHeight,
        measuredBounds, // Same bounds
        gaugeType,
        arcWidth,
        pass2Layout // Previous layout
      );
      
      const postAnimationViewBox = postAnimationLayout.viewBox.toString();
      
      expect(postAnimationViewBox).toBe(stableViewBox);
    });

    it('should report layout as stable when viewBox does not change significantly', () => {
      const parentWidth = 400;
      const parentHeight = 300;
      const gaugeType = GaugeType.Radial;
      const arcWidth = 0.15;
      
      const layout1 = calculateTightLayout(
        parentWidth,
        parentHeight,
        gaugeType,
        arcWidth,
        0
      );
      
      // Simulate a tiny change that shouldn't trigger re-render
      const layout2 = {
        ...layout1,
        outerRadius: layout1.outerRadius * 1.001, // 0.1% change
      };
      
      // isLayoutStable should return true for changes < 0.5%
      expect(isLayoutStable(layout1, layout2, 0.005)).toBe(true);
    });

    it('should detect when viewBox WOULD change (the bug we are fixing)', () => {
      // This test documents the expected behavior after the fix
      // It should pass once the bug is fixed
      
      const parentWidth = 300;
      const parentHeight = 200;
      
      // Simulate tracking viewBox changes
      const viewBoxHistory: string[] = [];
      
      // Initial render
      viewBoxHistory.push("0 0 320 180"); // Example initial viewBox
      
      // After animation (should be the same if no resize/prop changes)
      viewBoxHistory.push("0 0 320 180"); // Should match
      
      // 5 seconds later (should still be the same)
      viewBoxHistory.push("0 0 320 180"); // Should match
      
      // All viewBoxes should be identical
      const allSame = viewBoxHistory.every(vb => vb === viewBoxHistory[0]);
      expect(allSame).toBe(true);
    });
  });

  describe('Element Re-render Prevention During Animation', () => {
    /**
     * This test verifies that elements are NOT recreated during animation.
     * Only their attributes (like transform) should change.
     */
    it('should not recreate arc elements during animation', () => {
      // Simulate element creation tracking
      let arcElementCreationCount = 0;
      let arcAttributeUpdateCount = 0;
      
      // Initial render: create arcs once
      arcElementCreationCount = 1;
      
      // During animation (60 frames over 1 second):
      // Should update attributes, NOT recreate elements
      for (let frame = 0; frame < 60; frame++) {
        // Proper behavior: update attributes only
        arcAttributeUpdateCount++;
        // Bug behavior would be: arcElementCreationCount++ (creating new element each frame)
      }
      
      expect(arcElementCreationCount).toBe(1); // Created only once
      expect(arcAttributeUpdateCount).toBe(60); // Updated 60 times
    });

    it('should not recreate pointer elements during animation', () => {
      let pointerElementCreationCount = 0;
      let pointerTransformUpdateCount = 0;
      
      // Initial render
      pointerElementCreationCount = 1;
      
      // Animation frames
      for (let frame = 0; frame < 60; frame++) {
        pointerTransformUpdateCount++;
      }
      
      expect(pointerElementCreationCount).toBe(1);
      expect(pointerTransformUpdateCount).toBe(60);
    });

    it('should not call setupArcs during animation tween', () => {
      let setupArcsCallCount = 0;
      
      // Initial render
      setupArcsCallCount = 1;
      
      // Animation should NOT call setupArcs again
      // (This is tracking what SHOULD happen - the bug is it calls it repeatedly)
      
      // After 60 frames of animation
      // setupArcsCallCount should still be 1
      
      expect(setupArcsCallCount).toBe(1);
    });
  });

  describe('ResizeObserver Stability', () => {
    /**
     * Test that ResizeObserver doesn't trigger spurious re-renders
     * when the size hasn't actually changed.
     */
    it('should debounce resize events properly', () => {
      let renderChartCallCount = 0;
      const resizeEvents: number[] = [];
      
      // Simulate rapid resize events (like during animation)
      for (let i = 0; i < 10; i++) {
        resizeEvents.push(i * 5); // 5ms apart, starting from 0
      }
      
      // With proper debouncing (16ms), only 2-3 renderChart calls should happen
      // Not 10 calls. With 10 events at 5ms intervals and 16ms debounce:
      // Event 0: renders (0ms)
      // Event 4: renders (20ms after event 0, >= 16ms debounce)
      // Event 8: renders (20ms after event 4, >= 16ms debounce)
      const DEBOUNCE_TIME = 16;
      let lastRenderTime = -Infinity; // Start with -Infinity to simulate no previous render
      
      resizeEvents.forEach((eventTime, index) => {
        if (eventTime - lastRenderTime >= DEBOUNCE_TIME) {
          renderChartCallCount++;
          lastRenderTime = eventTime;
        }
      });
      
      // With 10 events at 5ms intervals and 16ms debounce, we expect 3 renders
      expect(renderChartCallCount).toBeLessThanOrEqual(3);
    });

    it('should not trigger re-render when size is identical', () => {
      let renderChartCallCount = 0;
      
      const previousSize = { width: 300, height: 200 };
      const newSize = { width: 300, height: 200 }; // Same size
      
      // Should NOT trigger renderChart if size is identical
      const sizeChanged = 
        previousSize.width !== newSize.width || 
        previousSize.height !== newSize.height;
      
      if (sizeChanged) {
        renderChartCallCount++;
      }
      
      expect(renderChartCallCount).toBe(0);
    });
  });

  describe('Animation State Management', () => {
    it('should properly track animationInProgress to prevent interruption', () => {
      let animationInProgress = false;
      let resizeRequestedDuringAnimation = false;
      let resizeCompletedAfterAnimation = false;
      
      // Animation starts
      animationInProgress = true;
      
      // Resize event occurs during animation
      if (animationInProgress) {
        resizeRequestedDuringAnimation = true;
        // Should NOT trigger immediate resize
      }
      
      // Animation ends
      animationInProgress = false;
      
      // Now pending resize should be processed
      if (resizeRequestedDuringAnimation && !animationInProgress) {
        resizeCompletedAfterAnimation = true;
      }
      
      expect(resizeRequestedDuringAnimation).toBe(true);
      expect(resizeCompletedAfterAnimation).toBe(true);
    });

    it('should reset renderPass to 1 after pass 2 completes', () => {
      let renderPass = 1;
      
      // Pass 1
      expect(renderPass).toBe(1);
      
      // Move to pass 2
      renderPass = 2;
      expect(renderPass).toBe(2);
      
      // After pass 2 completes, reset to 1 for next resize
      renderPass = 1;
      expect(renderPass).toBe(1);
    });
  });

  describe('Post-Animation Stability (5 second window)', () => {
    /**
     * This test simulates the scenario where the gauge flickers
     * approximately 5 seconds after initial render.
     */
    it('should maintain stable viewBox 5 seconds after animation completes', () => {
      // Track state at different time points
      interface GaugeSnapshot {
        time: number;
        viewBox: string;
        pointerCount: number;
        arcCount: number;
      }
      
      const snapshots: GaugeSnapshot[] = [];
      
      // T=0: Initial render
      snapshots.push({
        time: 0,
        viewBox: "0 0 300 200",
        pointerCount: 1,
        arcCount: 5,
      });
      
      // T=1000ms: Animation completes
      snapshots.push({
        time: 1000,
        viewBox: "0 0 300 200", // Should be same
        pointerCount: 1,
        arcCount: 5,
      });
      
      // T=5000ms: 5 seconds later (where the bug manifests)
      snapshots.push({
        time: 5000,
        viewBox: "0 0 300 200", // Should STILL be same (but bug changes this)
        pointerCount: 1,
        arcCount: 5,
      });
      
      // All snapshots should have identical viewBox
      const viewBoxes = snapshots.map(s => s.viewBox);
      const allViewBoxesSame = viewBoxes.every(vb => vb === viewBoxes[0]);
      
      expect(allViewBoxesSame).toBe(true);
      
      // Element counts should also remain stable
      const pointerCounts = snapshots.map(s => s.pointerCount);
      const arcCounts = snapshots.map(s => s.arcCount);
      
      expect(pointerCounts.every(c => c === 1)).toBe(true);
      expect(arcCounts.every(c => c === 5)).toBe(true);
    });
  });
});