import { describe, expect, it } from "vitest";
import {
  adjustPixels,
  estimateDeskew,
  luminance,
  otsuThreshold,
} from "../../src/scan/pixels";

function rgba(values: number[]) {
  return new Uint8ClampedArray(
    values.flatMap((value) => [value, value, value, 255]),
  );
}

describe("document pixels", () => {
  it("uses perceptual luminance", () => {
    expect(luminance(255, 0, 0)).toBe(54);
    expect(luminance(0, 255, 0)).toBe(182);
    expect(luminance(0, 0, 255)).toBe(18);
  });

  it("finds a separating Otsu threshold", () => {
    const threshold = otsuThreshold(rgba([5, 10, 15, 230, 240, 250]));
    expect(threshold).toBeGreaterThanOrEqual(15);
    expect(threshold).toBeLessThan(230);
  });

  it("creates an opaque black-and-white page", () => {
    expect([
      ...adjustPixels(rgba([20, 220]), {
        colourMode: "threshold",
        threshold: 100,
        brightness: 0,
        contrast: 0,
      }),
    ]).toEqual([0, 0, 0, 255, 255, 255, 255, 255]);
  });

  it("does not invent skew in an empty page", () => {
    expect(estimateDeskew(rgba(new Array(20 * 20).fill(255)), 20, 20)).toBe(0);
  });

  it("returns the corrective angle for tilted text lines", () => {
    const width = 120;
    const height = 90;
    const data = rgba(new Array(width * height).fill(255));
    const slope = Math.tan((3 * Math.PI) / 180);
    for (const baseline of [24, 44, 64]) {
      for (let x = 8; x < width - 8; x += 1) {
        const y = Math.round(baseline + (x - width / 2) * slope);
        for (let thickness = -1; thickness <= 1; thickness += 1) {
          const index = ((y + thickness) * width + x) * 4;
          data[index] = 0;
          data[index + 1] = 0;
          data[index + 2] = 0;
        }
      }
    }
    expect(estimateDeskew(data, width, height)).toBeCloseTo(-3, 0);
  });
});