'use strict';

const sharp = require('../../');
const fixtures = require('../fixtures');

const assert = require('assert');

describe('Linear adjustment', function () {
  const blackPoint = 70;
  const whitePoint = 203;
  const a = 255 / (whitePoint - blackPoint);
  const b = -blackPoint * a;

  it('applies linear levels adjustment w/o alpha ch', function (done) {
    sharp(fixtures.inputJpgWithLowContrast)
      .linear(a, b)
      .toBuffer(function (err, data, info) {
        if (err) throw err;
        fixtures.assertSimilar(fixtures.expected('low-contrast-linear.jpg'), data, done);
      });
  });

  it('applies slope level adjustment w/o alpha ch', function (done) {
    sharp(fixtures.inputJpgWithLowContrast)
      .linear(a)
      .toBuffer(function (err, data, info) {
        if (err) throw err;
        fixtures.assertSimilar(fixtures.expected('low-contrast-slope.jpg'), data, done);
      });
  });

  it('applies offset level adjustment w/o alpha ch', function (done) {
    sharp(fixtures.inputJpgWithLowContrast)
      .linear(null, b)
      .toBuffer(function (err, data, info) {
        if (err) throw err;
        fixtures.assertSimilar(fixtures.expected('low-contrast-offset.jpg'), data, done);
      });
  });

  it('applies linear levels adjustment w alpha ch', function (done) {
    sharp(fixtures.inputPngOverlayLayer1)
      .linear(a, b)
      .toBuffer(function (err, data, info) {
        if (err) throw err;
        fixtures.assertSimilar(fixtures.expected('alpha-layer-1-fill-linear.png'), data, done);
      });
  });

  it('applies slope level adjustment w alpha ch', function (done) {
    sharp(fixtures.inputPngOverlayLayer1)
      .linear(a)
      .toBuffer(function (err, data, info) {
        if (err) throw err;
        fixtures.assertSimilar(fixtures.expected('alpha-layer-1-fill-slope.png'), data, done);
      });
  });

  it('applies offset level adjustment w alpha ch', function (done) {
    sharp(fixtures.inputPngOverlayLayer1)
      .linear(null, b)
      .toBuffer(function (err, data, info) {
        if (err) throw err;
        fixtures.assertSimilar(fixtures.expected('alpha-layer-1-fill-offset.png'), data, done);
      });
  });

  it('Invalid linear arguments', function () {
    assert.throws(function () {
      sharp(fixtures.inputPngOverlayLayer1)
        .linear('foo');
    });

    assert.throws(function () {
      sharp(fixtures.inputPngOverlayLayer1)
        .linear(undefined, { 'bar': 'baz' });
    });
  });
});