package tins2020

import (
	"log"

	"github.com/veandco/go-sdl2/sdl"
)

func mapToTile(q PointF) Point {
	return Pt(int32(Round32(q.X)), int32(Round32(q.Y)))
}

type projection struct {
	center  PointF
	zoom    float32
	zoomInv float32

	windowInteractRect Rectangle
	windowVisibleRect  Rectangle
	tileScreenDelta    PointF
	tileScreenDeltaInv PointF
	tileScreenOffset   Point
	tileScreenSize     Point
	tileFitScreenSize  Point
	windowCenter       Point
}

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

func (p *projection) mapToScreen(x, y int32) Point {
	return p.mapToScreenF(float32(x), float32(y))
}

func (p *projection) mapToScreenF(x, y float32) Point {
	translated := PtF(x-p.center.X, y-p.center.Y)
	return Pt(p.windowCenter.X+int32((translated.X-translated.Y)*64*p.zoom), p.windowCenter.Y+int32((translated.X+translated.Y)*32*p.zoom))
}

func (p *projection) screenToMap(x, y int32) PointF {
	pos := p.screenToMapRel(x-p.windowCenter.X, y-p.windowCenter.Y)
	return p.center.Add(pos)
}

func (p *projection) screenToMapInt(x, y int32) Point {
	pos := p.screenToMap(x, y)
	return mapToTile(pos)
}

func (p *projection) screenToMapRel(x, y int32) PointF {
	normX := p.zoomInv * float32(x)
	normY := p.zoomInv * float32(y)
	return PtF(.5*(p.tileScreenDeltaInv.X*normX+p.tileScreenDeltaInv.Y*normY), .5*(-p.tileScreenDeltaInv.X*normX+p.tileScreenDeltaInv.Y*normY))
}

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

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

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

	p.tileScreenOffset = Pt(int32(p.zoom*64), int32(p.zoom*112))
	p.tileScreenSize = Pt(int32(p.zoom*128), int32(p.zoom*160))
	p.tileFitScreenSize = Pt(int32(p.zoom*64), int32(p.zoom*32))

	windowW, windowH, err := renderer.GetOutputSize()
	if err != nil {
		log.Fatal(err)
	}
	p.windowCenter = Pt(windowW/2, windowH/2)
	p.windowInteractRect = RectAbs(buttonBarWidth, 64, windowW-buttonBarWidth, windowH)
	p.windowVisibleRect = RectAbs(buttonBarWidth, 0, windowW-buttonBarWidth, windowH+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(int32, int32, Point)) {
	visible := p.windowVisibleRect
	topLeft := p.screenToMap(visible.X, visible.Y)
	topRight := p.screenToMap(visible.X+visible.W, visible.Y)
	bottomLeft := p.screenToMap(visible.X, visible.Y+visible.H)
	bottomRight := p.screenToMap(visible.X+visible.W, visible.Y+visible.H)
	minY, maxY := int32(Floor32(topRight.Y)), int32(Ceil32(bottomLeft.Y))
	minX, maxX := int32(Floor32(topLeft.X)), int32(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.X+rectFit.W < visible.X || rectFit.Y+rectFit.H < visible.Y {
				continue
			}
			if rectFit.X > visible.X+visible.W || rectFit.Y > visible.Y+visible.H {
				break
			}
			action(x, y, pos)
		}
	}
}

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

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

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