package uix

import (
	"git.kirsle.net/apps/doodle/pkg/balance"
	"git.kirsle.net/apps/doodle/pkg/drawtool"
	"git.kirsle.net/apps/doodle/pkg/level"
	"git.kirsle.net/apps/doodle/pkg/log"
	"git.kirsle.net/apps/doodle/pkg/shmem"
	"git.kirsle.net/go/render"
	"git.kirsle.net/go/ui"
)

// canvas_strokes.go: functions related to drawtool.Stroke and the Canvas.

// AddStroke installs a new Stroke to be superimposed over drawing data
// in the canvas.
//
// The stroke is added to the canvas's map by its ID so it can be removed later.
// The stroke must have a non-zero ID value set or this function will panic.
// drawtool.NewStroke() creates an initialized Stroke object to use here.
func (w *Canvas) AddStroke(stroke *drawtool.Stroke) {
	if stroke.ID == 0 {
		panic("Canvas.AddStroke: the Stroke is missing an ID; was it initialized properly?")
	}

	w.strokes[stroke.ID] = stroke
}

// RemoveStroke uninstalls a Stroke from the canvas using its ID.
//
// Returns true if the stroke existed to begin with, false if not.
func (w *Canvas) RemoveStroke(stroke *drawtool.Stroke) bool {
	if _, ok := w.strokes[stroke.ID]; ok {
		delete(w.strokes, stroke.ID)
		return true
	}
	return false
}

// UndoStroke rolls back the level's UndoHistory and deletes the pixels last
// added to the level. Returns false and emits a warning to the log if the
// canvas has no level loaded properly.
func (w *Canvas) UndoStroke() bool {
	if w.level == nil {
		log.Error("Canvas.UndoStroke: no Level currently available to the canvas")
		return false
	}

	latest := w.level.UndoHistory.Latest()
	if latest != nil {
		// TODO: only single-thickness lines will restore the original color;
		// thick lines just delete their pixels from the world due to performance.
		// But the Eraser Tool is always thick, which always should restore its
		// pixels. Can't do anything about that, so the inefficient thick rect
		// restore is used only for Eraser at least.
		if latest.Thickness > 0 {
			if latest.Shape == drawtool.Eraser {
				for rect := range latest.IterThickPoints() {
					var (
						xMin = rect.X
						xMax = rect.X + rect.W
						yMin = rect.Y
						yMax = rect.Y + rect.H
					)
					for x := xMin; x < xMax; x++ {
						for y := yMin; y < yMax; y++ {
							if v, ok := latest.OriginalPoints[render.NewPoint(x, y)]; ok {
								if swatch, ok := v.(*level.Swatch); ok {
									w.chunks.Set(render.NewPoint(x, y), swatch)
								}
							}
						}
					}
				}
			} else {
				for rect := range latest.IterThickPoints() {
					w.chunks.DeleteRect(rect)
				}
			}
		} else {
			for point := range latest.IterPoints() {
				// Was there a previous swatch at this point to restore?
				if v, ok := latest.OriginalPoints[point]; ok {
					if swatch, ok := v.(*level.Swatch); ok {
						w.chunks.Set(point, swatch)
						continue
					}
				}

				w.chunks.Delete(point)
			}

		}
	}
	return w.level.UndoHistory.Undo()
}

// RedoStroke rolls the level's UndoHistory forwards again and replays the
// recently undone changes.
func (w *Canvas) RedoStroke() bool {
	if w.level == nil {
		log.Error("Canvas.UndoStroke: no Level currently available to the canvas")
		return false
	}

	ok := w.level.UndoHistory.Redo()
	if !ok {
		return false
	}

	latest := w.level.UndoHistory.Latest()

	// We stored the ActiveSwatch on this stroke as we drew it. Recover it
	// and place the pixels back down.
	w.currentStroke = latest
	w.commitStroke(w.Tool, false)

	return ok
}

// presentStrokes is called as part of Present() and draws the strokes whose
// pixels are currently visible within the viewport.
func (w *Canvas) presentStrokes(e render.Engine) {
	// Turn stroke map into a list.
	var strokes []*drawtool.Stroke
	for _, stroke := range w.strokes {
		strokes = append(strokes, stroke)
	}
	w.drawStrokes(e, strokes)

	// Dynamic actor links visible in the ActorTool and LinkTool.
	if w.Tool == drawtool.ActorTool || w.Tool == drawtool.LinkTool {
		w.presentActorLinks(e)
	}
}

// presentActorLinks draws strokes connecting actors together by their links.
// TODO: the strokes are computed dynamically every tick in here, might be a
// way to better optimize later.
func (w *Canvas) presentActorLinks(e render.Engine) {
	var (
		strokes  = []*drawtool.Stroke{}
		actorMap = map[string]*Actor{}
	)

	// Loop over actors and collect linked ones into the map.
	for _, actor := range w.actors {
		if len(actor.Actor.Links) > 0 {
			actorMap[actor.ID()] = actor
		}
	}

	// If no links, stop.
	if len(actorMap) == 0 {
		return
	}

	// The glow colored line. Huge hacky block of code but makes for some
	// basic visualization for now.
	var color = balance.LinkLineColor
	var lightenStep = float64(balance.LinkLighten) / 16
	var step = shmem.Tick % balance.LinkAnimSpeed
	if step < 32 {
		for i := uint64(0); i < step; i++ {
			color = color.Lighten(int(lightenStep))
		}
		if step > 16 {
			for i := uint64(0); i < step-16; i++ {
				color = color.Darken(int(lightenStep))
			}
		}
	}

	// Loop over the linked actors and draw stroke lines.
	for _, actor := range actorMap {
		for _, linkID := range actor.Actor.Links {
			if _, ok := actorMap[linkID]; !ok {
				continue
			}

			var (
				aP = actor.Position()
				aS = actor.Size()
				bP = actorMap[linkID].Position()
				bS = actorMap[linkID].Size()
			)

			// Draw a line connecting the centers of each actor together.
			stroke := drawtool.NewStroke(drawtool.Line, color)
			stroke.Thickness = 1
			stroke.PointA = render.Point{
				X: aP.X + (aS.W / 2),
				Y: aP.Y + (aS.H / 2),
			}
			stroke.PointB = render.Point{
				X: bP.X + (bS.W / 2),
				Y: bP.Y + (bS.H / 2),
			}

			strokes = append(strokes, stroke)
		}
	}

	w.drawStrokes(e, strokes)
}

// drawStrokes is the common base function behind presentStrokes and
// presentActorLinks to actually draw the lines to the canvas.
func (w *Canvas) drawStrokes(e render.Engine, strokes []*drawtool.Stroke) {
	var (
		P  = ui.AbsolutePosition(w) // Canvas point in UI
		VP = w.ViewportRelative()   // Canvas scroll viewport
	)

	for _, stroke := range strokes {
		// If none of this stroke is in our viewport, don't waste time
		// looping through it.
		if stroke.Shape == drawtool.Freehand || stroke.Shape == drawtool.Eraser {
			if len(stroke.Points) >= 2 {
				if !stroke.Points[0].Inside(VP) && !stroke.Points[len(stroke.Points)-1].Inside(VP) {
					continue
				}
			}
		} else {
			// TODO: a very long line that starts and ends outside the viewport
			// but passes thru it would disappear when both ends are out of
			// view.
			if !stroke.PointA.Inside(VP) && !stroke.PointB.Inside(VP) {
				continue
			}
		}

		// Iter the points and draw what's visible.
		if stroke.Thickness > 0 {
			for rect := range stroke.IterThickPoints() {
				if !rect.Intersects(VP) {
					continue
				}

				// Destination rectangle to draw to screen, taking into account
				// the position of the Canvas itself.
				dest := render.Rect{
					X: rect.X + P.X + w.Scroll.X + w.BoxThickness(1),
					Y: rect.Y + P.Y + w.Scroll.Y + w.BoxThickness(1),
					W: rect.W,
					H: rect.H,
				}

				// Cap the render square so it doesn't leave the Canvas and
				// overlap other UI elements!
				if dest.X < P.X {
					// Left edge. TODO: right edge
					delta := P.X - dest.X
					dest.X = P.X
					dest.W -= delta
				}
				if dest.Y < P.Y {
					// Top edge. TODO: bottom edge
					delta := P.Y - dest.Y
					dest.Y = P.Y
					dest.H -= delta
				}

				if balance.DebugCanvasStrokeColor != render.Invisible {
					e.DrawBox(balance.DebugCanvasStrokeColor, dest)
				} else {
					e.DrawBox(stroke.Color, dest)
				}
			}
		} else {
			for point := range stroke.IterPoints() {
				if !point.Inside(VP) {
					continue
				}

				dest := render.Point{
					X: P.X + w.Scroll.X + w.BoxThickness(1) + point.X,
					Y: P.Y + w.Scroll.Y + w.BoxThickness(1) + point.Y,
				}

				if balance.DebugCanvasStrokeColor != render.Invisible {
					e.DrawPoint(balance.DebugCanvasStrokeColor, dest)
				} else {
					e.DrawPoint(stroke.Color, dest)
				}
			}
		}
	}
}