/** Detection canvas dimensions (smaller than video for performance). */
export const DETECTION_CANVAS_WIDTH = 320;
export const DETECTION_CANVAS_HEIGHT = 240;

/** Milliseconds before a tracked card is dropped when not re-detected. */
export const TRACK_STALE_MS = 3000;

/** Shape-detection polling interval in the camera scanner hook. */
export const SHAPE_DETECTION_INTERVAL_MS = 200;

/** Verification polling interval in the camera scanner hook. */
export const VERIFICATION_INTERVAL_MS = 1000;

/** Minimum stable frames before a tracked card is sent for identification. */
export const MIN_STABLE_COUNT_FOR_VERIFY = 3;

/** Minimum time (ms) a card must be tracked before verification. */
export const MIN_FIRST_SEEN_MS_FOR_VERIFY = 800;

/** Delay after camera start before detection loops begin. */
export const DETECTION_START_DELAY_MS = 1000;

/** Tracked cards eligible for one-shot server verification. */
export function selectCardsReadyForVerification(
  trackedCards,
  now = Date.now(),
  {
    minStableCount = MIN_STABLE_COUNT_FOR_VERIFY,
    maxScanAttempts = 1,
    minFirstSeenMs = MIN_FIRST_SEEN_MS_FOR_VERIFY,
  } = {}
) {
  return trackedCards.filter(
    (card) =>
      card.status === 'detecting' &&
      card.stableCount >= minStableCount &&
      card.scanAttempts < maxScanAttempts &&
      now - card.firstSeen > minFirstSeenMs
  );
}

/** Convert detection-canvas coordinates to video pixel coordinates. */
export function convertToVideoCoordinates(detection, canvas, video) {
  const scaleX = video.videoWidth / canvas.width;
  const scaleY = video.videoHeight / canvas.height;

  return {
    x: detection.x * scaleX,
    y: detection.y * scaleY,
    width: detection.width * scaleX,
    height: detection.height * scaleY,
  };
}

/** True when overlap area exceeds `threshold` of the smaller rectangle. */
export function rectanglesOverlap(rect1, rect2, threshold = 0.3) {
  const x1 = Math.max(rect1.x, rect2.x);
  const y1 = Math.max(rect1.y, rect2.y);
  const x2 = Math.min(rect1.x + rect1.width, rect2.x + rect2.width);
  const y2 = Math.min(rect1.y + rect1.height, rect2.y + rect2.height);

  if (x2 <= x1 || y2 <= y1) return false;

  const overlapArea = (x2 - x1) * (y2 - y1);
  const rect1Area = rect1.width * rect1.height;
  const rect2Area = rect2.width * rect2.height;
  const smallerArea = Math.min(rect1Area, rect2Area);

  return overlapArea / smallerArea > threshold;
}

/**
 * Draw the current video frame on `detectionCanvas` and return up to 5 card-like
 * bounding boxes in video coordinates.
 */
export function detectCardShapesFromFrame(video, detectionCanvas) {
  if (!video || !detectionCanvas) return [];

  const ctx = detectionCanvas.getContext('2d');
  detectionCanvas.width = DETECTION_CANVAS_WIDTH;
  detectionCanvas.height = DETECTION_CANVAS_HEIGHT;

  ctx.drawImage(video, 0, 0, detectionCanvas.width, detectionCanvas.height);

  const imageData = ctx.getImageData(0, 0, detectionCanvas.width, detectionCanvas.height);
  const data = imageData.data;

  const grayscale = [];
  const edges = [];

  for (let i = 0; i < data.length; i += 4) {
    const gray = Math.round(0.299 * data[i] + 0.587 * data[i + 1] + 0.114 * data[i + 2]);
    grayscale.push(gray);
  }

  for (let y = 1; y < detectionCanvas.height - 1; y++) {
    for (let x = 1; x < detectionCanvas.width - 1; x++) {
      const idx = y * detectionCanvas.width + x;

      const gx =
        -grayscale[idx - 1] +
        grayscale[idx + 1] +
        -2 * grayscale[idx - 1 + detectionCanvas.width] +
        2 * grayscale[idx + 1 + detectionCanvas.width] +
        -grayscale[idx - 1 + 2 * detectionCanvas.width] +
        grayscale[idx + 1 + 2 * detectionCanvas.width];

      const gy =
        -grayscale[idx - detectionCanvas.width] -
        2 * grayscale[idx] -
        grayscale[idx + detectionCanvas.width] +
        grayscale[idx - detectionCanvas.width + 2 * detectionCanvas.width] +
        2 * grayscale[idx + 2 * detectionCanvas.width] +
        grayscale[idx + detectionCanvas.width + 2 * detectionCanvas.width];

      const magnitude = Math.sqrt(gx * gx + gy * gy);
      edges[idx] = magnitude > 100 ? 255 : 0;
    }
  }

  const cardShapes = [];
  const { width, height } = detectionCanvas;

  const minCardWidth = Math.floor(width * 0.2);
  const maxCardWidth = Math.floor(width * 0.6);
  const minCardHeight = Math.floor(height * 0.25);
  const maxCardHeight = Math.floor(height * 0.7);

  for (let y = 0; y < height - minCardHeight; y += 15) {
    for (let x = 0; x < width - minCardWidth; x += 15) {
      for (let w = minCardWidth; w <= maxCardWidth && x + w < width; w += 20) {
        for (let h = minCardHeight; h <= maxCardHeight && y + h < height; h += 20) {
          const aspectRatio = w / h;
          if (aspectRatio < 0.63 || aspectRatio > 0.77) continue;

          let edgeCount = 0;
          let totalPixels = 0;
          let perimeterEdges = 0;

          for (let sy = y; sy < y + h; sy += 4) {
            for (let sx = x; sx < x + w; sx += 4) {
              const idx = sy * width + sx;
              if (edges[idx] === 255) {
                edgeCount++;

                const isPerimeter =
                  sx < x + w * 0.15 ||
                  sx > x + w * 0.85 ||
                  sy < y + h * 0.15 ||
                  sy > y + h * 0.85;
                if (isPerimeter) {
                  perimeterEdges++;
                }
              }
              totalPixels++;
            }
          }

          const edgeDensity = edgeCount / totalPixels;
          const perimeterRatio = perimeterEdges / (edgeCount || 1);

          if (edgeDensity > 0.2 && edgeDensity < 0.6 && perimeterRatio > 0.4 && edgeCount > 80) {
            const score = edgeDensity * 100 + perimeterRatio * 60 + edgeCount / 10;

            if (score > 50) {
              const videoCoords = convertToVideoCoordinates(
                { x, y, width: w, height: h },
                detectionCanvas,
                video
              );

              cardShapes.push({
                ...videoCoords,
                score,
                aspectRatio,
                edgeDensity,
              });
            }
          }
        }
      }
    }
  }

  return cardShapes.sort((a, b) => b.score - a.score).slice(0, 5);
}

/**
 * Merge fresh shape detections into the tracked-card list.
 * Returns updated cards and the next card id counter.
 */
export function mergeDetectedShapesIntoTrackedCards(
  trackedCards,
  detectedShapes,
  nextCardId,
  now = Date.now()
) {
  const updatedCards = [...trackedCards];

  for (let i = updatedCards.length - 1; i >= 0; i--) {
    if (now - updatedCards[i].lastSeen > TRACK_STALE_MS) {
      console.log(
        `🗑️ Removing stale tracked card ${updatedCards[i].id} (last seen ${Math.round((now - updatedCards[i].lastSeen) / 1000)}s ago)`
      );
      updatedCards.splice(i, 1);
    }
  }

  let idCounter = nextCardId;

  detectedShapes.forEach((shape) => {
    let matchedCard = null;

    for (const card of updatedCards) {
      if (rectanglesOverlap(shape, card.bounds, 0.4)) {
        matchedCard = card;
        break;
      }
    }

    if (matchedCard) {
      matchedCard.bounds = { ...shape };
      matchedCard.lastSeen = now;
      matchedCard.stableCount = Math.min(matchedCard.stableCount + 1, 10);

      const positionChange =
        Math.abs(matchedCard.bounds.x - shape.x) + Math.abs(matchedCard.bounds.y - shape.y);
      if (positionChange > 50 && matchedCard.status === 'negative') {
        console.log(`🔄 Card ${matchedCard.id} moved significantly, allowing re-scan`);
        matchedCard.status = 'detecting';
        matchedCard.scanAttempts = 0;
        matchedCard.stableCount = 1;
      }
    } else {
      const newCard = {
        id: idCounter++,
        bounds: { ...shape },
        status: 'detecting',
        firstSeen: now,
        lastSeen: now,
        stableCount: 1,
        scanAttempts: 0,
      };

      updatedCards.push(newCard);
      console.log(`🎯 New card shape detected: ${newCard.id}`);
    }
  });

  return { cards: updatedCards, nextCardId: idCounter };
}