package tins2020

import (
	"opslag.de/schobers/geom"
	"opslag.de/schobers/zntg/ui"
)

func mapToTile(q geom.PointF32) geom.Point {
	return geom.Pt(int(geom.Round32(q.X)), int(geom.Round32(q.Y)))
}

type projection struct {
	center  geom.PointF32
	zoom    float32
	zoomInv float32

	windowInteractRect geom.Rectangle
	windowVisibleRect  geom.Rectangle
	tileScreenDelta    geom.PointF32
	tileScreenDeltaInv geom.PointF32
	tileScreenOffset   geom.Point
	tileScreenSize     geom.Point
	tileFitScreenSize  geom.Point
	windowCenter       geom.Point
}

func newProjection() projection {
	return projection{zoom: 1, tileScreenDelta: geom.PtF32(64, 32), tileScreenDeltaInv: geom.PtF32(1./64, 1./32)}
}

func (p *projection) mapToScreen(x, y int) geom.Point {
	return p.mapToScreenF(float32(x), float32(y))
}

func (p *projection) mapToScreenF(x, y float32) geom.Point {
	translated := geom.PtF32(x-p.center.X, y-p.center.Y)
	return geom.Pt(p.windowCenter.X+int((translated.X-translated.Y)*64*p.zoom), p.windowCenter.Y+int((translated.X+translated.Y)*32*p.zoom))
}

func (p *projection) screenToMap(x, y int) geom.PointF32 {
	pos := p.screenToMapRel(x-p.windowCenter.X, y-p.windowCenter.Y)
	return p.center.Add(pos)
}

func (p *projection) screenToMapInt(x, y int) geom.Point {
	pos := p.screenToMap(x, y)
	return mapToTile(pos)
}

func (p *projection) screenToMapRel(x, y int) geom.PointF32 {
	normX := p.zoomInv * float32(x)
	normY := p.zoomInv * float32(y)
	return geom.PtF32(.5*(p.tileScreenDeltaInv.X*normX+p.tileScreenDeltaInv.Y*normY), .5*(-p.tileScreenDeltaInv.X*normX+p.tileScreenDeltaInv.Y*normY))
}

func (p *projection) screenToTileFitRect(pos geom.Point) geom.Rectangle {
	return geom.RectRel(pos.X-p.tileFitScreenSize.X, pos.Y-p.tileFitScreenSize.Y, 2*p.tileFitScreenSize.X, 2*p.tileFitScreenSize.Y)
}

func (p *projection) screenToTileRect(pos geom.Point) geom.Rectangle {
	return geom.RectRel(pos.X-p.tileScreenOffset.X, pos.Y-p.tileScreenOffset.Y, p.tileScreenSize.X, p.tileScreenSize.Y)
}

func (p *projection) update(renderer ui.Renderer) {
	p.zoomInv = 1 / p.zoom

	p.tileScreenOffset = geom.Pt(int(p.zoom*64), int(p.zoom*112))
	p.tileScreenSize = geom.Pt(int(p.zoom*128), int(p.zoom*160))
	p.tileFitScreenSize = geom.Pt(int(p.zoom*64), int(p.zoom*32))

	windowF32 := renderer.Size()
	window := geom.Pt(int(windowF32.X), int(windowF32.Y))
	p.windowCenter = geom.Pt(window.X/2, window.Y/2)
	p.windowInteractRect = geom.Rect(buttonBarWidth, 64, window.X-buttonBarWidth, window.Y)
	p.windowVisibleRect = geom.Rect(buttonBarWidth, 0, window.X-buttonBarWidth, window.Y+p.tileScreenSize.Y) // Adding a tile height to the bottom for trees that stick out from the cells below.
}

func (p *projection) visibleTiles(action func(int, int, geom.Point)) {
	visible := p.windowVisibleRect
	topLeft := p.screenToMap(visible.Min.X, visible.Min.Y)
	topRight := p.screenToMap(visible.Max.X, visible.Min.Y)
	bottomLeft := p.screenToMap(visible.Min.X, visible.Max.Y)
	bottomRight := p.screenToMap(visible.Max.Y, visible.Max.Y)
	minY, maxY := int(Floor32(topRight.Y)), int(Ceil32(bottomLeft.Y))
	minX, maxX := int(Floor32(topLeft.X)), int(Ceil32(bottomRight.X))
	for y := minY; y <= maxY; y++ {
		for x := minX; x <= maxX; x++ {
			pos := p.mapToScreen(x, y)
			rectFit := p.screenToTileFitRect(pos)
			if rectFit.Max.X < visible.Min.X || rectFit.Max.Y < visible.Min.Y {
				continue
			}
			if rectFit.Min.X > visible.Max.X || rectFit.Min.Y > visible.Max.Y {
				break
			}
			action(x, y, pos)
		}
	}
}

func (p *projection) Pan(ctx ui.Context, delta geom.PointF32) {
	p.center = p.center.Add(delta.Mul(p.zoomInv))
	p.update(ctx.Renderer())
}

func (p *projection) SetZoom(ctx ui.Context, center geom.PointF32, zoom float32) {
	if p.zoom == zoom {
		return
	}
	p.center = center.Sub(center.Sub(p.center).Mul(p.zoom / zoom))
	p.zoom = zoom
	p.update(ctx.Renderer())
}

func (p *projection) ZoomOut(ctx ui.Context, center geom.PointF32) {
	if p.zoom <= .25 {
		return
	}
	p.SetZoom(ctx, center, .5*p.zoom)
}

func (p *projection) ZoomIn(ctx ui.Context, center geom.PointF32) {
	if p.zoom >= 2 {
		return
	}
	p.SetZoom(ctx, center, 2*p.zoom)
}