src/utils/detection-parser.ts

import type { Detection } from "../hooks/LLMContext";

/**
 * Parse JSON detection output from Gemma 4.
 * Handles markdown code blocks, extra text, and partial output.
 * Returns array of {box_2d: [y1,x1,y2,x2], label: string}.
 */
export function parseJsonDetection(text: string): Detection[] {
  // Strip markdown code blocks
  let cleaned = text.replace(/```json\s*/g, "").replace(/```\s*/g, "").trim();

  // Try direct parse
  try {
    const result = JSON.parse(cleaned);
    if (Array.isArray(result)) return validateDetections(result);
  } catch {
    // fall through
  }

  // Try to find a JSON array in the text
  const match = cleaned.match(/\[[\s\S]*\]/);
  if (match) {
    try {
      const result = JSON.parse(match[0]);
      if (Array.isArray(result)) return validateDetections(result);
    } catch {
      // fall through
    }
  }

  return [];
}

function validateDetections(arr: unknown[]): Detection[] {
  return arr.filter(
    (d): d is Detection =>
      typeof d === "object" &&
      d !== null &&
      "box_2d" in d &&
      Array.isArray((d as Detection).box_2d) &&
      (d as Detection).box_2d.length === 4,
  );
}

/**
 * Convert Gemma 4 normalized coords (0-1000) to pixel coordinates.
 * Input: [y1, x1, y2, x2] (Gemma format, Y-first)
 * Output: [x1, y1, x2, y2] (canvas format, X-first)
 */
export function toPixelCoords(
  box_2d: [number, number, number, number],
  width: number,
  height: number,
): [number, number, number, number] {
  const [y1Norm, x1Norm, y2Norm, x2Norm] = box_2d;
  return [
    (x1Norm / 1000) * width,
    (y1Norm / 1000) * height,
    (x2Norm / 1000) * width,
    (y2Norm / 1000) * height,
  ];
}

export const DETECTION_COLORS = [
  "#ff6b6b", "#4ecdc4", "#45b7d1", "#f9ca24",
  "#6c5ce7", "#a8e6cf", "#fd79a8", "#fdcb6e",
  "#0984e3", "#00b894", "#e17055", "#74b9ff",
];