galaxy-game/client/world/renderer_lines_test.go

package world

import (
	"testing"

	"github.com/stretchr/testify/require"
)

func TestDrawLinesFromPlan_WrapX_SplitsAndDrawsInThreeXTiles(t *testing.T) {
	t.Parallel()

	w := NewWorld(10, 10)
	w.resetGrid(2 * SCALE)

	// Horizontal line that wraps across X: 9 -> 1 at y=5.
	id, err := w.AddLine(9, 5, 1, 5)
	require.NoError(t, err)
	w.indexObject(w.objects[id])

	params := RenderParams{
		ViewportWidthPx:  10,
		ViewportHeightPx: 10,
		MarginXPx:        2,
		MarginYPx:        2,
		CameraXWorldFp:   5 * SCALE,
		CameraYWorldFp:   5 * SCALE,
		CameraZoom:       1.0,
	}

	plan, err := w.buildRenderPlanStageA(params)
	require.NoError(t, err)

	d := &fakePrimitiveDrawer{}
	drawLinesFromPlan(d, plan, w.W, w.H)

	// Expect drawing in 3 X tiles (left partial, middle full, right partial) for the central Y tile:
	// Each tile group: Save, ClipRect, AddLine(s), Stroke, Restore
	//
	// Left tile (offsetX=-10000): 1 line segment.
	// Middle tile (offsetX=0): 2 segments (wrapped split).
	// Right tile (offsetX=10000): 1 segment.
	wantNames := []string{
		"Save", "ClipRect", "AddLine", "Stroke", "Restore",
		"Save", "ClipRect", "AddLine", "AddLine", "Stroke", "Restore",
		"Save", "ClipRect", "AddLine", "Stroke", "Restore",
	}
	require.Equal(t, wantNames, d.CommandNames())

	// Group 1: left strip clip (0,2,2,10), line at y=7 from x=1..2
	{
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 1), 0, 2, 2, 10)
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 2), 1, 7, 2, 7)
	}

	// Group 2: middle strip clip (2,2,10,10), two segments:
	// segment [9000..10000] => x 11..12, y 7
	// segment [0..1000]     => x 2..3,  y 7
	{
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 6), 2, 2, 10, 10)

		// The order of segments is stable with our splitting: first the one ending at boundary, then the remainder.
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 7), 11, 7, 12, 7)
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 8), 2, 7, 3, 7)
	}

	// Group 3: right strip clip (12,2,2,10), line at y=7 from x=12..13
	{
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 12), 12, 2, 2, 10) // ClipRect
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 13), 12, 7, 13, 7) // AddLine
	}
}

func TestDrawLinesFromPlan_WrapY_SplitsAndDrawsInThreeYTiles(t *testing.T) {
	t.Parallel()

	w := NewWorld(10, 10)
	w.resetGrid(2 * SCALE)

	// Vertical line that wraps across Y: 9 -> 1 at x=5.
	id, err := w.AddLine(5, 9, 5, 1)
	require.NoError(t, err)
	w.indexObject(w.objects[id])

	params := RenderParams{
		ViewportWidthPx:  10,
		ViewportHeightPx: 10,
		MarginXPx:        2,
		MarginYPx:        2,
		CameraXWorldFp:   5 * SCALE,
		CameraYWorldFp:   5 * SCALE,
		CameraZoom:       1.0,
	}

	plan, err := w.buildRenderPlanStageA(params)
	require.NoError(t, err)

	d := &fakePrimitiveDrawer{}
	drawLinesFromPlan(d, plan, w.W, w.H)

	// Here we expect 3 Y tiles for the central X tile:
	// Top partial, middle full (two segments), bottom partial.
	//
	// The exact ordering of tiles is by tx then ty, so X=middle strips first.
	// For this geometry the line only intersects the middle X tiles (offsetX=0),
	// but spans Y across -1,0,1.
	wantNames := []string{
		"Save", "ClipRect", "AddLine", "Stroke", "Restore",
		"Save", "ClipRect", "AddLine", "AddLine", "Stroke", "Restore",
		"Save", "ClipRect", "AddLine", "Stroke", "Restore",
	}
	require.Equal(t, wantNames, d.CommandNames())

	// Group 1: top strip clip (2,0,10,2), line at x=7 from y=1..2
	{
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 1), 2, 0, 10, 2)
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 2), 7, 1, 7, 2)
	}

	// Group 2: middle strip clip (2,2,10,10), two segments:
	// segment [9000..10000] => y 11..12 at x=7
	// segment [0..1000]     => y 2..3  at x=7
	{
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 6), 2, 2, 10, 10)
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 7), 7, 11, 7, 12)
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 8), 7, 2, 7, 3)
	}

	// Group 3: bottom strip clip (2,12,10,2), line at x=7 from y=12..13
	{
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 12), 2, 12, 10, 2) // ClipRect
		requireCommandArgs(t, requireDrawerCommandAt(t, d, 13), 7, 12, 7, 13) // AddLine
	}
}

func TestTorusShortestLineSegments_TieCaseIsDeterministicAndSplits(t *testing.T) {
	t.Parallel()

	// World 10 units => 10000 fixed.
	worldW := 10 * SCALE
	worldH := 10 * SCALE

	// Tie-case along X: 1 -> 6 is exactly half world apart (dx = +5000).
	// Deterministic rule chooses negative delta representation (wrap is applied).
	l := Line{
		X1: 1 * SCALE, Y1: 5 * SCALE,
		X2: 6 * SCALE, Y2: 5 * SCALE,
	}

	segs := torusShortestLineSegments(l, worldW, worldH)

	// Expect two horizontal segments:
	// [6000..10000] and [0..1000] at y=5000.
	require.Len(t, segs, 2)

	// Direction is deterministic and follows the chosen negative-delta representation.
	require.Equal(t, lineSeg{x1: 1000, y1: 5000, x2: 0, y2: 5000}, segs[0])
	require.Equal(t, lineSeg{x1: 10000, y1: 5000, x2: 6000, y2: 5000}, segs[1])
}