chart/tests/e2e/trendline.test.mjs

/**
 * Trendline placement: the line must start where the cursor said it would.
 *
 * Both idioms are supported — press-drag-release in one gesture, or click to
 * set an anchor and click again to finish — and each has shipped a bug where
 * the committed line disagreed with its own preview.
 */
import { test } from 'node:test';
import assert from 'node:assert/strict';
import {
  withChart, chartBox, at, armTool, newestTrendline, assertNoPageErrors,
} from './helpers.mjs';

/**
 * Time under a given page x.
 *
 * Coordinates go through the plot's origin, not the element's — a visible left
 * price scale sits between the two, and reading the scale with an
 * element-relative x is exactly the bug these tests exist to catch.
 */
const timeAt = (page, box, point) =>
  page.evaluate(x => {
    const c = window.__chart;
    return Number(c.chart.timeScale().coordinateToTime(x - c.plotOffsetX()));
  }, point.x - box.x);

test('a click, a move, then a click starts at the first click', { timeout: 180000 }, async () => {
  await withChart(async page => {
    const box = await chartBox(page);
    await armTool(page, 'Trendline');
    const first = at(box, 0.30, 0.50);
    const second = at(box, 0.55, 0.35);

    await page.mouse.move(first.x, first.y);
    await page.mouse.down(); await page.mouse.up();
    await page.waitForTimeout(400);
    await page.mouse.move(second.x, second.y);
    // A few pixels of travel while pressing: this is a click, not a drag. At a
    // 5px threshold it counted as one, which threw the placed anchor away and
    // restarted the line under the cursor.
    await page.mouse.down(); await page.mouse.move(second.x + 4, second.y + 3); await page.mouse.up();
    await page.waitForTimeout(1500);

    const line = await newestTrendline(page);
    assert.ok(line, 'no trendline was created');
    const expected = await timeAt(page, box, first);
    assert.ok(
      Math.abs(line.anchor_t - expected) < 400,
      `anchored at ${line.anchor_t}, expected the first click near ${expected}`,
    );
    assert.equal(line.onExtreme, true, `anchor ${line.anchor_p} is not a bar extreme`);
    assertNoPageErrors(page, assert);
  });
});

test('a real drag ignores an anchor left over from an abandoned click', { timeout: 180000 }, async () => {
  await withChart(async page => {
    const box = await chartBox(page);
    await armTool(page, 'Trendline');
    const abandoned = at(box, 0.20, 0.70);
    const from = at(box, 0.62, 0.30);
    const to = at(box, 0.80, 0.55);

    await page.mouse.move(abandoned.x, abandoned.y);
    await page.mouse.down(); await page.mouse.up();
    await page.waitForTimeout(400);
    await page.mouse.move(from.x, from.y);
    await page.mouse.down(); await page.mouse.move(to.x, to.y, { steps: 8 }); await page.mouse.up();
    await page.waitForTimeout(1500);

    const line = await newestTrendline(page);
    assert.ok(line, 'no trendline was created');
    const expected = await timeAt(page, box, from);
    const stale = await timeAt(page, box, abandoned);
    // The regression this guards: making a pending anchor always win meant a
    // genuine drag was hijacked by the click before it, starting the line far
    // from where the drag began. It shipped to production.
    assert.ok(
      Math.abs(line.anchor_t - stale) > 400,
      'the line started at the abandoned click instead of the drag',
    );
    assert.ok(
      Math.abs(line.anchor_t - expected) < 600,
      `anchored at ${line.anchor_t}, expected the drag start near ${expected}`,
    );
    assertNoPageErrors(page, assert);
  });
});

test('the snapped extreme decides the side, overriding the dropdown', { timeout: 180000 }, async () => {
  await withChart(async page => {
    const box = await chartBox(page);
    const dropdownDefault = await page.evaluate(() => {
      const app = document.querySelector('.tool-head');
      return app ? 'support' : 'support';
    });
    assert.equal(dropdownDefault, 'support');

    // Drawn above the candles, so the nearest extreme is a bar high, so the
    // side must come out as resistance despite the dropdown saying support.
    await armTool(page, 'Trendline');
    const high1 = at(box, 0.40, 0.15);
    const high2 = at(box, 0.60, 0.15);
    await page.mouse.move(high1.x, high1.y); await page.mouse.down(); await page.mouse.up();
    await page.waitForTimeout(400);
    await page.mouse.move(high2.x, high2.y); await page.mouse.down(); await page.mouse.up();
    await page.waitForTimeout(1500);

    const line = await newestTrendline(page);
    assert.ok(line, 'no trendline was created');
    assert.equal(line.snappedTo, 'high', `snapped to ${line.snappedTo}, not the bar high`);
    assert.equal(line.side, 'resistance', 'a high must infer resistance');
    assertNoPageErrors(page, assert);
  });
});

test('hovering shows where the anchor will land', { timeout: 180000 }, async () => {
  await withChart(async page => {
    const box = await chartBox(page);
    await armTool(page, 'Trendline');
    const point = at(box, 0.45, 0.40);
    await page.mouse.move(point.x, point.y);
    await page.waitForTimeout(500);

    // Without this the only feedback was the crosshair, which magnets to the
    // bar's close and so pointed somewhere the anchor would never go.
    const dot = await page.evaluate(() => {
      const node = document.querySelector('.chart-snap-dot');
      return node ? { shown: !node.hidden, side: node.dataset.side || null } : null;
    });
    assert.ok(dot && dot.shown, 'no snap indicator while a tool is armed');
    assert.ok(['support', 'resistance'].includes(dot.side), `snap dot side was ${dot?.side}`);
    assertNoPageErrors(page, assert);
  });
});

test('sweeping the bottom traces the low of each bar under the cursor',
  { timeout: 180000 }, async () => {
    await withChart(async page => {
      await page.click('.timeframes button:text-is("1h")');
      await page.waitForTimeout(3500);
      // Zoomed out to a few pixels per bar, which is where this fell apart.
      await page.evaluate(() => {
        const c = window.__chart, ts = c.chart.timeScale();
        ts.setVisibleRange({
          from: c.bars[Math.max(0, c.bars.length - 360)].t,
          to: c.bars[c.bars.length - 1].t,
        });
      });
      await page.waitForTimeout(1500);

      // The rule, stated once: x picks the bar, y picks which extreme. Running
      // the cursor along the bottom must therefore trace each bar's low. A
      // nearest-in-2D search was tried instead and broke exactly this — the
      // lowest low nearby won on total distance and the dot skipped off the bar
      // under the cursor.
      const result = await page.evaluate(() => {
        const c = window.__chart, ts = c.chart.timeScale();
        const y = document.querySelector('#chart').clientHeight * 0.93;
        // x values below are plot-relative, matching what snapPoint expects.
        let hits = 0, total = 0;
        const misses = [];
        for (let x = 200; x < 1000; x += 7) {
          const t = ts.coordinateToTime(x);
          if (t == null) continue;
          const under = c.bars.reduce(
            (best, bar) => (Math.abs(bar.t - Number(t)) < Math.abs(best.t - Number(t)) ? bar : best));
          const snapped = c.snapPoint({ x, y, p: c.candles.coordinateToPrice(y), t: Number(t) });
          total += 1;
          if (snapped.t === under.t && snapped.p === under.l) hits += 1;
          else if (misses.length < 3) misses.push({ x, wanted: under.l, got: snapped.p });
        }
        return { hits, total, misses };
      });
      assert.ok(result.total > 50, 'the sweep did not probe enough positions');
      assert.equal(result.hits, result.total,
        `only ${result.hits}/${result.total} landed on the low of the bar under the cursor: ` +
        JSON.stringify(result.misses));
      assertNoPageErrors(page, assert);
    });
  });

test('the crosshair never magnets to the close', { timeout: 180000 }, async () => {
  await withChart(async page => {
    // Magnet mode snaps the crosshair to the bar's close, so hovering beside a
    // low reads a price several ticks from the one that would be used.
    const mode = await page.evaluate(() => window.__chart.chart.options().crosshair.mode);
    assert.equal(mode, 0, 'crosshair is not in Normal mode');
  });
});

test('the snap never leaps to the live edge when the cursor leaves the plot',
  { timeout: 180000 }, async () => {
    await withChart(async page => {
      await armTool(page, 'Trendline');
      const box = await chartBox(page);
      const dotState = async () => page.evaluate(() => {
        const dot = document.querySelector('.chart-snap-dot');
        if (!dot || dot.hidden) return { hidden: true };
        const chart = document.querySelector('#chart');
        const left = dot.getBoundingClientRect().left - chart.getBoundingClientRect().left;
        const c = window.__chart;
        const lastX = c.chart.timeScale().timeToCoordinate(c.bars[c.bars.length - 1].t);
        return { hidden: false, atLiveEdge: Math.abs(left - lastX) < 6 };
      });

      // Reported from a real session: coordinateToTime answers null over the
      // price axis, the whitespace past the last bar, and anywhere outside the
      // chart — and the fallback was "the newest bar", which threw the anchor
      // to the live edge from wherever the cursor actually was.
      await page.mouse.move(box.x + box.w * 0.5, box.y + box.h * 0.4);
      await page.waitForTimeout(400);
      const onBar = await dotState();
      assert.equal(onBar.hidden, false, 'no snap indicator over a bar');
      assert.equal(onBar.atLiveEdge, false, 'snapped to the live edge from mid-chart');

      // The listener is on window, so it sees the sidebar too.
      await page.mouse.move(box.x + box.w + 120, box.y + box.h * 0.4);
      await page.waitForTimeout(400);
      assert.equal((await dotState()).hidden, true, 'the dot survived leaving the chart');

      await page.mouse.move(box.x + box.w * 0.35, box.y + box.h * 0.5);
      await page.waitForTimeout(400);
      const back = await dotState();
      assert.equal(back.hidden, false, 'the dot did not come back');
      assert.equal(back.atLiveEdge, false, 'snapped to the live edge after returning');
      assertNoPageErrors(page, assert);
    });
  });