package tins2020

import (
	"fmt"
	"log"

	"opslag.de/schobers/geom"

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

type terrainRenderer struct {
	terrain *Map
	hover   PointF
	project projection

	interact interaction
}

type interaction struct {
	mousePos      Point
	mouseLeftDown bool
	mouseDrag     *Point
}

type projection struct {
	center  PointF
	zoom    float32
	zoomInv float32

	tileScreenDelta    PointF
	tileScreenDeltaInv PointF
	tileScreenOffset   Point
	tileScreenSize     Point
	windowCenter       Point
}

func newProjection() projection {
	return projection{zoom: 1, tileScreenDelta: PtF(65, 32), tileScreenDeltaInv: PtF(1./65, 1./32)}
}

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

	p.tileScreenOffset = Pt(int32(p.zoomInv*256), int32(p.zoomInv*300))
	p.tileScreenSize = Pt(int32(p.zoomInv*512), int32(p.zoomInv*512))

	windowW, windowH, err := renderer.GetOutputSize()
	if err != nil {
		log.Fatal(err)
	}
	p.windowCenter = Pt(windowW/2, windowH/2)
}

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)*65*p.zoomInv), p.windowCenter.Y+int32((translated.X+translated.Y)*32*p.zoomInv))
}

func (p *projection) screenToMapRel(x, y int32) PointF {
	normX := p.zoom * float32(x)
	normY := p.zoom * 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) screenToMap(x, y int32) PointF {
	pos := p.screenToMapRel(x-p.windowCenter.X, y-p.windowCenter.Y)
	return p.center.Add(pos)
}

func (p *projection) screenToTileRect(pos Point) *sdl.Rect {
	return &sdl.Rect{X: pos.X - p.tileScreenOffset.X, Y: pos.Y - p.tileScreenOffset.Y, W: p.tileScreenSize.X, H: p.tileScreenSize.Y}
}

func NewTerrainRenderer(terrain *Map) Control {
	return &terrainRenderer{terrain: terrain, project: newProjection()}
}

func (r *terrainRenderer) Init(ctx *Context) error {
	r.project.update(ctx.Renderer)
	return nil
}

func (r *terrainRenderer) Handle(ctx *Context, event sdl.Event) {
	switch e := event.(type) {
	case *sdl.MouseButtonEvent:
		if e.Button == sdl.BUTTON_LEFT {
			r.interact.mouseLeftDown = e.Type == sdl.MOUSEBUTTONDOWN
			if r.interact.mouseLeftDown && r.interact.mouseDrag == nil {
				r.interact.mouseDrag = &Point{e.X, e.Y}
			} else if !r.interact.mouseLeftDown && r.interact.mouseDrag != nil {
				r.interact.mouseDrag = nil
			}
		}
	case *sdl.MouseMotionEvent:
		r.hover = r.project.screenToMap(e.X, e.Y)
		if r.interact.mouseDrag != nil {
			r.project.center = r.project.center.Sub(r.project.screenToMapRel(e.X-r.interact.mouseDrag.X, e.Y-r.interact.mouseDrag.Y))
			r.project.update(ctx.Renderer)
			r.interact.mouseDrag = &Point{e.X, e.Y}
		}
	case *sdl.MouseWheelEvent:
		if e.Y > 0 && r.project.zoom > .5 {
			r.project.zoom *= .5
			r.project.update(ctx.Renderer)
		} else if e.Y < 0 && r.project.zoom < 4 {
			r.project.zoom *= 2
			r.project.update(ctx.Renderer)
		}
	case *sdl.WindowEvent:
		if e.Event == sdl.WINDOWEVENT_RESIZED {
			r.project.update(ctx.Renderer)
		}
	}
}

func (r *terrainRenderer) Render(ctx *Context) {
	toTileTexture := func(temp, humid float64) *Texture {
		if temp < .35 {
			return ctx.Textures.Texture("tile-snow")
		}
		if temp > .65 {
			return ctx.Textures.Texture("tile-dirt")
		}
		return ctx.Textures.Texture("tile-grass")
	}

	variantToInt := func(variant float64) int {
		if variant < .25 {
			return 1
		}
		if variant < .5 {
			return 2
		}
		if variant < .75 {
			return 3
		}
		if variant < 1 {
			return 4
		}
		return -1
	}

	variantToTexture := func(format string, variant float64) *Texture {
		textName := fmt.Sprintf(format, variantToInt(variant))
		return ctx.Textures.Texture(textName)
	}

	stretch := func(x, from, to float64) float64 { return (x - from) * 1 / (to - from) }

	toPropTexture := func(temp, humid, variant float64) *Texture {
		if temp < .35 {
			if humid < .2 {
				return nil
			} else if humid < .7 {
				return variantToTexture("bush-small-%d", variant*5)
			}
			return variantToTexture("tree-pine-%d", variant*5)
		}
		if temp > .65 {
			if humid < .2 {
				return nil
			}
			if humid < .7 {
				return variantToTexture("cactus-short-%d", variant*7)
			}
			return variantToTexture("cactus-tall-%d", variant*2)
		}
		if humid < .2 {
			return nil
		}
		multiplier := 1 - stretch(humid, 0.2, 1)
		if variant < .5 {
			return variantToTexture("tree-fat-%d", stretch(variant, 0, .5)*multiplier*3)
		} else if variant < .8 {
			return variantToTexture("grass-small-%d", stretch(variant, .5, .8)*multiplier*2)
		}
		return variantToTexture("bush-large-%d", stretch(variant, .8, 1)*multiplier)
	}

	// horizontal: [191, 321) = 130
	// vertical: [267,332) = 65

	hover := Pt(int32(geom.Round32(r.hover.X)), int32(geom.Round32(r.hover.Y)))
	for y := int32(-100); y < 100; y++ {
		for x := int32(-100); x < 100; x++ {
			if x == hover.X && y == hover.Y {
				continue
			}
			temp := r.terrain.Temp.Value(x, y)
			humid := r.terrain.Humid.Value(x, y)
			text := toTileTexture(temp, humid)
			pos := r.project.mapToScreen(x, y)
			text.Copy(ctx.Renderer, r.project.screenToTileRect(pos))
		}
	}

	for y := int32(-100); y < 100; y++ {
		for x := int32(-100); x < 100; x++ {
			variant := r.terrain.Variant.Value(x, y)
			if variant < -1 || variant > 1 {
				continue
			}

			temp := r.terrain.Temp.Value(x, y)
			humid := r.terrain.Humid.Value(x, y)
			text := toPropTexture(temp, humid, variant)
			if text == nil {
				continue
			}

			placeX, placeY := r.terrain.PlaceX.Value(x, y), r.terrain.PlaceY.Value(x, y)
			pos := r.project.mapToScreenF(float32(x)-.2+float32(.8*placeX-.4), float32(y)-.2+float32(.8*placeY-.4))

			text.Copy(ctx.Renderer, r.project.screenToTileRect(pos))
		}
	}
}