package d2dagrelayout

import (
	"context"
	_ "embed"
	"encoding/json"
	"fmt"
	"math"
	"regexp"
	"sort"
	"strings"

	"cdr.dev/slog"
	"github.com/dop251/goja"

	"oss.terrastruct.com/util-go/xdefer"

	"oss.terrastruct.com/util-go/go2"

	"oss.terrastruct.com/d2/d2graph"
	"oss.terrastruct.com/d2/d2target"
	"oss.terrastruct.com/d2/lib/geo"
	"oss.terrastruct.com/d2/lib/label"
	"oss.terrastruct.com/d2/lib/log"
	"oss.terrastruct.com/d2/lib/shape"
)

//go:embed setup.js
var setupJS string

//go:embed dagre.js
var dagreJS string

const (
	MIN_RANK_SEP    = 60
	EDGE_LABEL_GAP  = 20
	DEFAULT_PADDING = 30.
)

type ConfigurableOpts struct {
	NodeSep int `json:"nodesep"`
	EdgeSep int `json:"edgesep"`
}

var DefaultOpts = ConfigurableOpts{
	NodeSep: 60,
	EdgeSep: 20,
}

type DagreNode struct {
	ID     string  `json:"id"`
	X      float64 `json:"x"`
	Y      float64 `json:"y"`
	Width  float64 `json:"width"`
	Height float64 `json:"height"`
}

type DagreEdge struct {
	Points []*geo.Point `json:"points"`
}

type dagreOpts struct {
	// for a top to bottom graph: ranksep is y spacing, nodesep is x spacing, edgesep is x spacing
	ranksep int
	// graph direction: tb (top to bottom)| bt | lr | rl
	rankdir string

	ConfigurableOpts
}

func DefaultLayout(ctx context.Context, g *d2graph.Graph) (err error) {
	return Layout(ctx, g, nil)
}

func Layout(ctx context.Context, g *d2graph.Graph, opts *ConfigurableOpts) (err error) {
	if opts == nil {
		opts = &DefaultOpts
	}
	defer xdefer.Errorf(&err, "failed to dagre layout")

	debugJS := false
	vm := goja.New()
	if _, err := vm.RunString(dagreJS); err != nil {
		return err
	}
	if _, err := vm.RunString(setupJS); err != nil {
		return err
	}

	rootAttrs := dagreOpts{
		ConfigurableOpts: ConfigurableOpts{
			EdgeSep: opts.EdgeSep,
			NodeSep: opts.NodeSep,
		},
	}
	isHorizontal := false
	switch g.Root.Direction.Value {
	case "down":
		rootAttrs.rankdir = "TB"
	case "right":
		rootAttrs.rankdir = "LR"
		isHorizontal = true
	case "left":
		rootAttrs.rankdir = "RL"
		isHorizontal = true
	case "up":
		rootAttrs.rankdir = "BT"
	default:
		rootAttrs.rankdir = "TB"
	}

	// set label and icon positions for dagre
	for _, obj := range g.Objects {
		positionLabelsIcons(obj)
	}

	maxLabelWidth := 0
	maxLabelHeight := 0
	for _, edge := range g.Edges {
		width := edge.LabelDimensions.Width
		height := edge.LabelDimensions.Height
		maxLabelWidth = go2.Max(maxLabelWidth, width)
		maxLabelHeight = go2.Max(maxLabelHeight, height)
	}

	if !isHorizontal {
		rootAttrs.ranksep = go2.Max(100, maxLabelHeight+40)
	} else {
		rootAttrs.ranksep = go2.Max(100, maxLabelWidth+40)
		// use existing config
		// rootAttrs.NodeSep = rootAttrs.EdgeSep
		// // configure vertical padding
		// rootAttrs.EdgeSep = maxLabelHeight + 40
		// Note: non-containers have both of these as padding (rootAttrs.NodeSep + rootAttrs.EdgeSep)
	}

	configJS := setGraphAttrs(rootAttrs)
	if _, err := vm.RunString(configJS); err != nil {
		return err
	}

	loadScript := ""
	idToObj := make(map[string]*d2graph.Object)
	for _, obj := range g.Objects {
		id := obj.AbsID()
		idToObj[id] = obj

		width, height := obj.Width, obj.Height

		loadScript += generateAddNodeLine(id, int(width), int(height))
		if obj.Parent != g.Root {
			loadScript += generateAddParentLine(id, obj.Parent.AbsID())
		}
	}

	for _, edge := range g.Edges {
		src, dst := getEdgeEndpoints(g, edge)

		width := edge.LabelDimensions.Width
		height := edge.LabelDimensions.Height

		numEdges := 0
		for _, e := range g.Edges {
			otherSrc, otherDst := getEdgeEndpoints(g, e)
			if (otherSrc == src && otherDst == dst) || (otherSrc == dst && otherDst == src) {
				numEdges++
			}
		}

		// We want to leave some gap between multiple edges
		if numEdges > 1 {
			switch g.Root.Direction.Value {
			case "down", "up", "":
				width += EDGE_LABEL_GAP
			case "left", "right":
				height += EDGE_LABEL_GAP
			}
		}

		loadScript += generateAddEdgeLine(src.AbsID(), dst.AbsID(), edge.AbsID(), width, height)
	}

	if debugJS {
		log.Debug(ctx, "script", slog.F("all", setupJS+configJS+loadScript))
	}

	if _, err := vm.RunString(loadScript); err != nil {
		return err
	}

	if _, err := vm.RunString(`dagre.layout(g)`); err != nil {
		if debugJS {
			log.Warn(ctx, "layout error", slog.F("err", err))
		}
		return err
	}

	for i := range g.Objects {
		val, err := vm.RunString(fmt.Sprintf("JSON.stringify(g.node(g.nodes()[%d]))", i))
		if err != nil {
			return err
		}
		var dn DagreNode
		if err := json.Unmarshal([]byte(val.String()), &dn); err != nil {
			return err
		}
		if debugJS {
			log.Debug(ctx, "graph", slog.F("json", dn))
		}

		obj := idToObj[dn.ID]

		// dagre gives center of node
		obj.TopLeft = geo.NewPoint(math.Round(dn.X-dn.Width/2), math.Round(dn.Y-dn.Height/2))
		obj.Width = math.Ceil(dn.Width)
		obj.Height = math.Ceil(dn.Height)
	}

	for i, edge := range g.Edges {
		val, err := vm.RunString(fmt.Sprintf("JSON.stringify(g.edge(g.edges()[%d]))", i))
		if err != nil {
			return err
		}
		var de DagreEdge
		if err := json.Unmarshal([]byte(val.String()), &de); err != nil {
			return err
		}
		if debugJS {
			log.Debug(ctx, "graph", slog.F("json", de))
		}

		points := make([]*geo.Point, len(de.Points))
		for i := range de.Points {
			if edge.SrcArrow && !edge.DstArrow {
				points[len(de.Points)-i-1] = de.Points[i].Copy()
			} else {
				points[i] = de.Points[i].Copy()
			}
		}

		startIndex, endIndex := 0, len(points)-1
		start, end := points[startIndex], points[endIndex]

		// chop where edge crosses the source/target boxes since container edges were routed to a descendant
		if edge.Src != edge.Dst {
			for i := 1; i < len(points); i++ {
				segment := *geo.NewSegment(points[i-1], points[i])
				if intersections := edge.Src.Box.Intersections(segment); len(intersections) > 0 {
					start = intersections[0]
					startIndex = i - 1
				}

				if intersections := edge.Dst.Box.Intersections(segment); len(intersections) > 0 {
					end = intersections[0]
					endIndex = i
					break
				}
			}
		}
		points = points[startIndex : endIndex+1]
		points[0] = start
		points[len(points)-1] = end

		edge.Route = points
	}

	adjustRankSpacing(g, float64(rootAttrs.ranksep), isHorizontal)
	adjustCrossRankSpacing(g, float64(rootAttrs.ranksep), !isHorizontal)

	fitContainerPadding(g, float64(rootAttrs.ranksep), isHorizontal)

	for _, edge := range g.Edges {
		points := edge.Route
		startIndex, endIndex := 0, len(points)-1
		start, end := points[startIndex], points[endIndex]

		// arrowheads can appear broken if segments are very short from dagre routing a point just outside the shape
		// to fix this, we try extending the previous segment into the shape instead of having a very short segment
		if startIndex+2 < len(points) {
			newStartingSegment := *geo.NewSegment(start, points[startIndex+1])
			if newStartingSegment.Length() < d2graph.MIN_SEGMENT_LEN {
				// we don't want a very short segment right next to the source because it will mess up the arrowhead
				// instead we want to extend the next segment into the shape border if possible
				nextStart := points[startIndex+1]
				nextEnd := points[startIndex+2]

				// Note: in other direction to extend towards source
				nextSegment := *geo.NewSegment(nextStart, nextEnd)
				v := nextSegment.ToVector()
				extendedStart := nextEnd.ToVector().Add(v.AddLength(d2graph.MIN_SEGMENT_LEN)).ToPoint()
				extended := *geo.NewSegment(nextEnd, extendedStart)

				if intersections := edge.Src.Box.Intersections(extended); len(intersections) > 0 {
					startIndex++
					points[startIndex] = intersections[0]
					start = points[startIndex]
				}
			}
		}
		if endIndex-2 >= 0 {
			newEndingSegment := *geo.NewSegment(end, points[endIndex-1])
			if newEndingSegment.Length() < d2graph.MIN_SEGMENT_LEN {
				// extend the prev segment into the shape border if possible
				prevStart := points[endIndex-2]
				prevEnd := points[endIndex-1]

				prevSegment := *geo.NewSegment(prevStart, prevEnd)
				v := prevSegment.ToVector()
				extendedEnd := prevStart.ToVector().Add(v.AddLength(d2graph.MIN_SEGMENT_LEN)).ToPoint()
				extended := *geo.NewSegment(prevStart, extendedEnd)

				if intersections := edge.Dst.Box.Intersections(extended); len(intersections) > 0 {
					endIndex--
					points[endIndex] = intersections[0]
					end = points[endIndex]
				}
			}
		}

		var originalSrcTL, originalDstTL *geo.Point
		// if the edge passes through 3d/multiple, use the offset box for tracing to border
		if srcDx, srcDy := edge.Src.GetModifierElementAdjustments(); srcDx != 0 || srcDy != 0 {
			if start.X > edge.Src.TopLeft.X+srcDx &&
				start.Y < edge.Src.TopLeft.Y+edge.Src.Height-srcDy {
				originalSrcTL = edge.Src.TopLeft.Copy()
				edge.Src.TopLeft.X += srcDx
				edge.Src.TopLeft.Y -= srcDy
			}
		}
		if dstDx, dstDy := edge.Dst.GetModifierElementAdjustments(); dstDx != 0 || dstDy != 0 {
			if end.X > edge.Dst.TopLeft.X+dstDx &&
				end.Y < edge.Dst.TopLeft.Y+edge.Dst.Height-dstDy {
				originalDstTL = edge.Dst.TopLeft.Copy()
				edge.Dst.TopLeft.X += dstDx
				edge.Dst.TopLeft.Y -= dstDy
			}
		}

		startIndex, endIndex = edge.TraceToShape(points, startIndex, endIndex)
		points = points[startIndex : endIndex+1]

		// build a curved path from the dagre route
		vectors := make([]geo.Vector, 0, len(points)-1)
		for i := 1; i < len(points); i++ {
			vectors = append(vectors, points[i-1].VectorTo(points[i]))
		}

		path := make([]*geo.Point, 0)
		path = append(path, points[0])
		if len(vectors) > 1 {
			path = append(path, points[0].AddVector(vectors[0].Multiply(.8)))
			for i := 1; i < len(vectors)-2; i++ {
				p := points[i]
				v := vectors[i]
				path = append(path, p.AddVector(v.Multiply(.2)))
				path = append(path, p.AddVector(v.Multiply(.5)))
				path = append(path, p.AddVector(v.Multiply(.8)))
			}
			path = append(path, points[len(points)-2].AddVector(vectors[len(vectors)-1].Multiply(.2)))
			edge.IsCurve = true
		}
		path = append(path, points[len(points)-1])

		edge.Route = path
		// compile needs to assign edge label positions
		if edge.Label.Value != "" {
			edge.LabelPosition = go2.Pointer(string(label.InsideMiddleCenter))
		}

		// undo 3d/multiple offset
		if originalSrcTL != nil {
			edge.Src.TopLeft.X = originalSrcTL.X
			edge.Src.TopLeft.Y = originalSrcTL.Y
		}
		if originalDstTL != nil {
			edge.Dst.TopLeft.X = originalDstTL.X
			edge.Dst.TopLeft.Y = originalDstTL.Y
		}
	}

	return nil
}

func getEdgeEndpoints(g *d2graph.Graph, edge *d2graph.Edge) (*d2graph.Object, *d2graph.Object) {
	// dagre doesn't work with edges to containers so we connect container edges to their first child instead (going all the way down)
	// we will chop the edge where it intersects the container border so it only shows the edge from the container
	src := edge.Src
	for len(src.Children) > 0 && src.Class == nil && src.SQLTable == nil {
		// We want to get the bottom node of sources, setting its rank higher than all children
		src = getLongestEdgeChainTail(g, src)
	}
	dst := edge.Dst
	for len(dst.Children) > 0 && dst.Class == nil && dst.SQLTable == nil {
		dst = getLongestEdgeChainHead(g, dst)
	}
	if edge.SrcArrow && !edge.DstArrow {
		// for `b <- a`, edge.Edge is `a -> b` and we expect this routing result
		src, dst = dst, src
	}
	return src, dst
}

func setGraphAttrs(attrs dagreOpts) string {
	return fmt.Sprintf(`g.setGraph({
  ranksep: %d,
  edgesep: %d,
  nodesep: %d,
  rankdir: "%s",
});
`,
		attrs.ranksep,
		attrs.ConfigurableOpts.EdgeSep,
		attrs.ConfigurableOpts.NodeSep,
		attrs.rankdir,
	)
}

func escapeID(id string) string {
	// fixes \\
	id = strings.ReplaceAll(id, "\\", `\\`)
	// replaces \n with \\n whenever \n is not preceded by \ (does not replace \\n)
	re := regexp.MustCompile(`[^\\]\n`)
	id = re.ReplaceAllString(id, `\\n`)
	// avoid an unescaped \r becoming a \n in the layout result
	id = strings.ReplaceAll(id, "\r", `\r`)
	return id
}

func generateAddNodeLine(id string, width, height int) string {
	id = escapeID(id)
	return fmt.Sprintf("g.setNode(`%s`, { id: `%s`, width: %d, height: %d });\n", id, id, width, height)
}

func generateAddParentLine(childID, parentID string) string {
	return fmt.Sprintf("g.setParent(`%s`, `%s`);\n", escapeID(childID), escapeID(parentID))
}

func generateAddEdgeLine(fromID, toID, edgeID string, width, height int) string {
	return fmt.Sprintf("g.setEdge({v:`%s`, w:`%s`, name:`%s`}, { width:%d, height:%d, labelpos: `c` });\n", escapeID(fromID), escapeID(toID), escapeID(edgeID), width, height)
}

// getLongestEdgeChainHead finds the longest chain in a container and gets its head
// If there are multiple chains of the same length, get the head closest to the center
func getLongestEdgeChainHead(g *d2graph.Graph, container *d2graph.Object) *d2graph.Object {
	rank := make(map[*d2graph.Object]int)
	chainLength := make(map[*d2graph.Object]int)

	for _, obj := range container.ChildrenArray {
		isHead := true
		for _, e := range g.Edges {
			if inContainer(e.Src, container) != nil && inContainer(e.Dst, obj) != nil {
				isHead = false
				break
			}
		}
		if !isHead {
			continue
		}
		rank[obj] = 1
		chainLength[obj] = 1
		// BFS
		queue := []*d2graph.Object{obj}
		visited := make(map[*d2graph.Object]struct{})
		for len(queue) > 0 {
			curr := queue[0]
			queue = queue[1:]
			if _, ok := visited[curr]; ok {
				continue
			}
			visited[curr] = struct{}{}
			for _, e := range g.Edges {
				child := inContainer(e.Dst, container)
				if child == curr {
					continue
				}
				if child != nil && inContainer(e.Src, curr) != nil {
					if rank[curr]+1 > rank[child] {
						rank[child] = rank[curr] + 1
						chainLength[obj] = go2.Max(chainLength[obj], rank[child])
					}
					queue = append(queue, child)
				}
			}
		}
	}
	max := int(math.MinInt32)
	for _, obj := range container.ChildrenArray {
		if chainLength[obj] > max {
			max = chainLength[obj]
		}
	}

	var heads []*d2graph.Object
	for i, obj := range container.ChildrenArray {
		if rank[obj] == 1 && chainLength[obj] == max {
			heads = append(heads, container.ChildrenArray[i])
		}
	}

	if len(heads) > 0 {
		return heads[int(math.Floor(float64(len(heads))/2.0))]
	}
	return container.ChildrenArray[0]
}

// getLongestEdgeChainTail gets the node at the end of the longest edge chain, because that will be the end of the container
// and is what external connections should connect with.
// If there are multiple of same length, get the one closest to the middle
func getLongestEdgeChainTail(g *d2graph.Graph, container *d2graph.Object) *d2graph.Object {
	rank := make(map[*d2graph.Object]int)

	for _, obj := range container.ChildrenArray {
		isHead := true
		for _, e := range g.Edges {
			if inContainer(e.Src, container) != nil && inContainer(e.Dst, obj) != nil {
				isHead = false
				break
			}
		}
		if !isHead {
			continue
		}
		rank[obj] = 1
		// BFS
		queue := []*d2graph.Object{obj}
		visited := make(map[*d2graph.Object]struct{})
		for len(queue) > 0 {
			curr := queue[0]
			queue = queue[1:]
			if _, ok := visited[curr]; ok {
				continue
			}
			visited[curr] = struct{}{}
			for _, e := range g.Edges {
				child := inContainer(e.Dst, container)
				if child == curr {
					continue
				}
				if child != nil && inContainer(e.Src, curr) != nil {
					rank[child] = go2.Max(rank[child], rank[curr]+1)
					queue = append(queue, child)
				}
			}
		}
	}
	max := int(math.MinInt32)
	for _, obj := range container.ChildrenArray {
		if rank[obj] > max {
			max = rank[obj]
		}
	}

	var tails []*d2graph.Object
	for i, obj := range container.ChildrenArray {
		if rank[obj] == max {
			tails = append(tails, container.ChildrenArray[i])
		}
	}

	return tails[int(math.Floor(float64(len(tails))/2.0))]
}

func inContainer(obj, container *d2graph.Object) *d2graph.Object {
	if obj == nil {
		return nil
	}
	if obj == container {
		return obj
	}
	if obj.Parent == container {
		return obj
	}
	return inContainer(obj.Parent, container)
}

type spacing struct {
	top, bottom, left, right float64
}

func getSpacing(obj *d2graph.Object) (margin, padding spacing) {
	if obj.HasLabel() {
		var position label.Position
		if obj.LabelPosition != nil {
			position = label.Position(*obj.LabelPosition)
		} else if len(obj.ChildrenArray) == 0 && obj.HasOutsideBottomLabel() {
			position = label.OutsideBottomCenter
		}

		labelWidth := float64(obj.LabelDimensions.Width) + 2*label.PADDING
		labelHeight := float64(obj.LabelDimensions.Height) + 2*label.PADDING

		switch position {
		case label.OutsideTopLeft, label.OutsideTopCenter, label.OutsideTopRight:
			margin.top = labelHeight
		case label.OutsideBottomLeft, label.OutsideBottomCenter, label.OutsideBottomRight:
			margin.bottom = labelHeight
		case label.OutsideLeftTop, label.OutsideLeftMiddle, label.OutsideLeftBottom:
			margin.left = labelWidth
		case label.OutsideRightTop, label.OutsideRightMiddle, label.OutsideRightBottom:
			margin.right = labelWidth
		case label.InsideTopLeft, label.InsideTopCenter, label.InsideTopRight:
			padding.top = labelHeight
		case label.InsideBottomLeft, label.InsideBottomCenter, label.InsideBottomRight:
			padding.bottom = labelHeight
		case label.InsideMiddleLeft:
			padding.left = labelWidth
		case label.InsideMiddleRight:
			padding.right = labelWidth
		}
	}

	if obj.Icon != nil && obj.Shape.Value != d2target.ShapeImage {
		var position label.Position
		if obj.IconPosition != nil {
			position = label.Position(*obj.IconPosition)
		}

		iconSize := float64(d2target.MAX_ICON_SIZE + 2*label.PADDING)
		switch position {
		case label.OutsideTopLeft, label.OutsideTopCenter, label.OutsideTopRight:
			margin.top = math.Max(margin.top, iconSize)
		case label.OutsideBottomLeft, label.OutsideBottomCenter, label.OutsideBottomRight:
			margin.bottom = math.Max(margin.bottom, iconSize)
		case label.OutsideLeftTop, label.OutsideLeftMiddle, label.OutsideLeftBottom:
			margin.left = math.Max(margin.left, iconSize)
		case label.OutsideRightTop, label.OutsideRightMiddle, label.OutsideRightBottom:
			margin.right = math.Max(margin.right, iconSize)
		case label.InsideTopLeft, label.InsideTopCenter, label.InsideTopRight:
			padding.top = math.Max(padding.top, iconSize)
		case label.InsideBottomLeft, label.InsideBottomCenter, label.InsideBottomRight:
			padding.bottom = math.Max(padding.bottom, iconSize)
		case label.InsideMiddleLeft:
			padding.left = math.Max(padding.left, iconSize)
		case label.InsideMiddleRight:
			padding.right = math.Max(padding.right, iconSize)
		}
	}

	dx, dy := obj.GetModifierElementAdjustments()
	margin.right += dx
	margin.top += dy

	return
}

func positionLabelsIcons(obj *d2graph.Object) {
	if obj.Icon != nil && obj.IconPosition == nil {
		if len(obj.ChildrenArray) > 0 {
			obj.IconPosition = go2.Pointer(string(label.OutsideTopLeft))
			if obj.LabelPosition == nil {
				obj.LabelPosition = go2.Pointer(string(label.OutsideTopRight))
				return
			}
		} else {
			obj.IconPosition = go2.Pointer(string(label.InsideMiddleCenter))
		}
	}
	if obj.HasLabel() && obj.LabelPosition == nil {
		if len(obj.ChildrenArray) > 0 {
			obj.LabelPosition = go2.Pointer(string(label.OutsideTopCenter))
		} else if obj.HasOutsideBottomLabel() {
			obj.LabelPosition = go2.Pointer(string(label.OutsideBottomCenter))
		} else if obj.Icon != nil {
			obj.LabelPosition = go2.Pointer(string(label.InsideTopCenter))
		} else {
			obj.LabelPosition = go2.Pointer(string(label.InsideMiddleCenter))
		}
	}
}

func getRanks(g *d2graph.Graph, isHorizontal bool) (ranks [][]*d2graph.Object, objectRanks, startingParentRanks, endingParentRanks map[*d2graph.Object]int) {
	alignedObjects := make(map[float64][]*d2graph.Object)
	for _, obj := range g.Objects {
		if !obj.IsContainer() {
			if !isHorizontal {
				y := math.Ceil(obj.TopLeft.Y + obj.Height/2)
				alignedObjects[y] = append(alignedObjects[y], obj)
			} else {
				x := math.Ceil(obj.TopLeft.X + obj.Width/2)
				alignedObjects[x] = append(alignedObjects[x], obj)
			}
		}
	}

	levels := make([]float64, 0, len(alignedObjects))
	for l := range alignedObjects {
		levels = append(levels, l)
	}
	sort.Slice(levels, func(i, j int) bool {
		return levels[i] < levels[j]
	})

	ranks = make([][]*d2graph.Object, 0, len(levels))
	objectRanks = make(map[*d2graph.Object]int)
	for i, l := range levels {
		for _, obj := range alignedObjects[l] {
			objectRanks[obj] = i
		}
		ranks = append(ranks, alignedObjects[l])
	}

	startingParentRanks = make(map[*d2graph.Object]int)
	endingParentRanks = make(map[*d2graph.Object]int)
	for _, obj := range g.Objects {
		if obj.IsContainer() {
			continue
		}
		r := objectRanks[obj]
		// update all ancestor's min/max ranks
		for parent := obj.Parent; parent != nil && parent != g.Root; parent = parent.Parent {
			if start, has := startingParentRanks[parent]; !has || r < start {
				startingParentRanks[parent] = r
			}
			if end, has := endingParentRanks[parent]; !has || r > end {
				endingParentRanks[parent] = r
			}
		}
	}

	return ranks, objectRanks, startingParentRanks, endingParentRanks
}

// shift everything down by distance if it is at or below start position
func shiftDown(g *d2graph.Graph, start, distance float64, isHorizontal bool) {
	if isHorizontal {
		for _, obj := range g.Objects {
			if obj.TopLeft.X < start {
				continue
			}
			obj.TopLeft.X += distance
		}
		for _, edge := range g.Edges {
			for _, p := range edge.Route {
				// Note: == so incoming edge shifts down with object at startY
				if p.X <= start {
					continue
				}
				p.X += distance
			}
		}
	} else {
		for _, obj := range g.Objects {
			if obj.TopLeft.Y < start {
				continue
			}
			obj.TopLeft.Y += distance
		}
		for _, edge := range g.Edges {
			for _, p := range edge.Route {
				// Note: == so incoming edge shifts down with object at startY
				if p.Y <= start {
					continue
				}
				p.Y += distance
			}
		}
	}
}

func shiftUp(g *d2graph.Graph, start, distance float64, isHorizontal bool) {
	if isHorizontal {
		for _, obj := range g.Objects {
			if start < obj.TopLeft.X {
				continue
			}
			obj.TopLeft.X -= distance
		}
		for _, edge := range g.Edges {
			for _, p := range edge.Route {
				// Note: == so incoming edge shifts down with object at startY
				if start <= p.X {
					continue
				}
				p.X -= distance
			}
		}
	} else {
		for _, obj := range g.Objects {
			if start < obj.TopLeft.Y {
				continue
			}
			obj.TopLeft.Y -= distance
		}
		for _, edge := range g.Edges {
			for _, p := range edge.Route {
				// Note: == so incoming edge shifts down with object at startY
				if start <= p.Y {
					continue
				}
				p.Y -= distance
			}
		}
	}
}

// shift down everything that is below start
// shift all nodes that are reachable via an edge or being directly below a shifting node or expanding container
// expand containers to wrap shifted nodes
func shiftReachableDown(g *d2graph.Graph, obj *d2graph.Object, start, distance float64, isHorizontal, isMargin bool) map[*d2graph.Object]struct{} {
	q := []*d2graph.Object{obj}

	seen := make(map[*d2graph.Object]struct{})
	shifted := make(map[*d2graph.Object]struct{})
	shiftedEdges := make(map[*d2graph.Edge]struct{})
	queue := func(o *d2graph.Object) {
		if _, in := seen[o]; in {
			return
		}
		q = append(q, o)
	}

	// if object below is within this distance after shifting, also shift it
	threshold := 100.
	checkBelow := func(curr *d2graph.Object) {
		currBottom := curr.TopLeft.Y + curr.Height
		currRight := curr.TopLeft.X + curr.Width
		if isHorizontal {
			originalRight := currRight
			if _, in := shifted[curr]; in {
				originalRight -= distance
			}
			for _, other := range g.Objects {
				if other == curr || curr.IsDescendantOf(other) {
					continue
				}
				if originalRight < other.TopLeft.X &&
					other.TopLeft.X < originalRight+distance+threshold &&
					curr.TopLeft.Y < other.TopLeft.Y+other.Height &&
					other.TopLeft.Y < currBottom {
					queue(other)
				}
			}
		} else {
			originalBottom := currBottom
			if _, in := shifted[curr]; in {
				originalBottom -= distance
			}
			for _, other := range g.Objects {
				if other == curr || curr.IsDescendantOf(other) {
					continue
				}
				if originalBottom < other.TopLeft.Y &&
					other.TopLeft.Y < originalBottom+distance+threshold &&
					curr.TopLeft.X < other.TopLeft.X+other.Width &&
					other.TopLeft.X < currRight {
					queue(other)
				}
			}
		}
	}

	processQueue := func() {
		for len(q) > 0 {
			curr := q[0]
			q = q[1:]
			if _, was := seen[curr]; was {
				continue
			}
			// skip other objects behind start
			if curr != obj {
				if isHorizontal {
					if curr.TopLeft.X < start {
						continue
					}
				} else {
					if curr.TopLeft.Y < start {
						continue
					}
				}
			}

			if isHorizontal {
				shift := false
				if !isMargin {
					shift = start < curr.TopLeft.X
				} else {
					shift = start <= curr.TopLeft.X
				}

				if shift {
					curr.TopLeft.X += distance
					shifted[curr] = struct{}{}
				}
			} else {
				shift := false
				if !isMargin {
					shift = start < curr.TopLeft.Y
				} else {
					shift = start <= curr.TopLeft.Y
				}
				if shift {
					curr.TopLeft.Y += distance
					shifted[curr] = struct{}{}
				}
			}
			seen[curr] = struct{}{}

			if curr.Parent != g.Root && !curr.IsDescendantOf(obj) {
				queue(curr.Parent)
			}

			for _, child := range curr.ChildrenArray {
				queue(child)
			}

			for _, e := range g.Edges {
				if _, in := shiftedEdges[e]; in {
					continue
				}
				if e.Src == curr && e.Dst == curr {
					if isHorizontal {
						for _, p := range e.Route {
							p.X += distance
						}
					} else {
						for _, p := range e.Route {
							p.Y += distance
						}
					}
					shiftedEdges[e] = struct{}{}
					continue
				} else if e.Src == curr {
					queue(e.Dst)
					if isHorizontal {
						for _, p := range e.Route {
							if start <= p.X {
								p.X += distance
							}
						}
					} else {
						for _, p := range e.Route {
							if start <= p.Y {
								p.Y += distance
							}
						}
					}
					shiftedEdges[e] = struct{}{}
				} else if e.Dst == curr {
					queue(e.Src)
					if isHorizontal {
						for _, p := range e.Route {
							if start <= p.X {
								p.X += distance
							}
						}
					} else {
						for _, p := range e.Route {
							if start <= p.Y {
								p.Y += distance
							}
						}
					}
					shiftedEdges[e] = struct{}{}
				}
			}

			// check for nodes below that need to move from the shift
			checkBelow(curr)
		}
	}

	processQueue()

	grown := make(map[*d2graph.Object]struct{})
	for o := range seen {
		if o.Parent == g.Root {
			continue
		}
		if _, in := shifted[o.Parent]; in {
			continue
		}
		if _, in := grown[o.Parent]; in {
			continue
		}

		for parent := o.Parent; parent != g.Root; parent = parent.Parent {
			if _, in := shifted[parent]; in {
				break
			}
			if _, in := grown[parent]; in {
				break
			}

			if isHorizontal {
				if parent.TopLeft.X < start {
					parent.Width += distance
					grown[parent] = struct{}{}

					checkBelow(parent)
					processQueue()
				}
			} else {
				if parent.TopLeft.Y < start {
					parent.Height += distance
					grown[parent] = struct{}{}

					checkBelow(parent)
					processQueue()
				}
			}
		}
	}

	increasedMargins := make(map[*d2graph.Object]struct{})
	movedObjects := make([]*d2graph.Object, 0, len(shifted))
	for obj := range shifted {
		movedObjects = append(movedObjects, obj)
	}
	for obj := range grown {
		movedObjects = append(movedObjects, obj)
	}
	for _, moved := range movedObjects {
		counts := true
		// check if any other shifted is directly above
		for _, other := range movedObjects {
			if other == moved {
				continue
			}
			if isHorizontal {
				if other.TopLeft.Y+other.Height < moved.TopLeft.Y ||
					moved.TopLeft.Y+moved.Height < other.TopLeft.Y {
					// doesn't line up vertically
					continue
				}

				// above and within threshold
				if other.TopLeft.X < moved.TopLeft.X &&
					moved.TopLeft.X < other.TopLeft.X+other.Width+threshold {
					counts = false
					break
				}
			} else {
				if other.TopLeft.X+other.Width < moved.TopLeft.X ||
					moved.TopLeft.X+moved.Width < other.TopLeft.X {
					// doesn't line up horizontally
					continue
				}

				// above and within threshold
				if other.TopLeft.Y < moved.TopLeft.Y &&
					moved.TopLeft.Y < other.TopLeft.Y+other.Height+threshold {
					counts = false
					break
				}
			}
		}
		if counts {
			increasedMargins[moved] = struct{}{}
		}
	}

	return increasedMargins
}

func adjustRankSpacing(g *d2graph.Graph, rankSep float64, isHorizontal bool) {
	ranks, objectRanks, startingParentRanks, endingParentRanks := getRanks(g, isHorizontal)

	// shifting bottom rank down first, then moving up to next rank
	for rank := len(ranks) - 1; rank >= 0; rank-- {
		var startingParents []*d2graph.Object
		var endingParents []*d2graph.Object
		for _, obj := range ranks[rank] {
			if obj.Parent == g.Root {
				continue
			}
			if r, has := endingParentRanks[obj.Parent]; has && r == rank {
				endingParents = append(endingParents, obj.Parent)
			}
			if r, has := startingParentRanks[obj.Parent]; has && r == rank {
				startingParents = append(startingParents, obj.Parent)
			}
		}

		startingAncestorPositions := make(map[*d2graph.Object]float64)
		for len(startingParents) > 0 {
			var ancestors []*d2graph.Object
			for _, parent := range startingParents {
				_, padding := getSpacing(parent)
				if _, has := startingAncestorPositions[parent]; !has {
					startingAncestorPositions[parent] = math.Inf(1)
				}
				var startPosition float64
				if isHorizontal {
					paddingIncrease := math.Max(0, padding.left-rankSep/2)
					startPosition = parent.TopLeft.X - paddingIncrease
				} else {
					paddingIncrease := math.Max(0, padding.top-rankSep/2)
					startPosition = parent.TopLeft.Y - paddingIncrease
				}
				startingAncestorPositions[parent] = math.Min(startingAncestorPositions[parent], startPosition)
				for _, child := range parent.ChildrenArray {
					if r, has := objectRanks[child]; has {
						if r != rank {
							continue
						}
					} else {
						startingRank := startingParentRanks[child]
						endingRank := endingParentRanks[child]
						if startingRank != rank && endingRank != rank {
							continue
						}
					}
					margin, _ := getSpacing(child)
					if isHorizontal {
						startPosition = child.TopLeft.X - margin.left
					} else {
						startPosition = child.TopLeft.Y - margin.top
					}
					startingAncestorPositions[parent] = math.Min(startingAncestorPositions[parent], startPosition)
				}
				if parent.Parent != g.Root {
					ancestors = append(ancestors, parent.Parent)
				}
			}
			startingParents = ancestors
		}

		endingAncestorPositions := make(map[*d2graph.Object]float64)
		for len(endingParents) > 0 {
			var ancestors []*d2graph.Object
			for _, parent := range endingParents {
				_, padding := getSpacing(parent)
				if _, has := endingAncestorPositions[parent]; !has {
					endingAncestorPositions[parent] = math.Inf(-1)
				}
				var endPosition float64
				if isHorizontal {
					endPosition = parent.TopLeft.X + parent.Width + padding.right - rankSep/2.
				} else {
					endPosition = parent.TopLeft.Y + parent.Height + padding.bottom - rankSep/2.
				}
				endingAncestorPositions[parent] = math.Max(endingAncestorPositions[parent], endPosition)
				for _, child := range parent.ChildrenArray {
					if r, has := objectRanks[child]; has {
						if r != rank {
							continue
						}
					} else {
						startingRank := startingParentRanks[child]
						endingRank := endingParentRanks[child]
						if startingRank != rank && endingRank != rank {
							continue
						}
					}
					margin, _ := getSpacing(child)

					if isHorizontal {
						endPosition = child.TopLeft.X + child.Width + margin.right
					} else {
						endPosition = child.TopLeft.Y + child.Height + margin.bottom
					}
					endingAncestorPositions[parent] = math.Max(endingAncestorPositions[parent], endPosition)
				}
				if parent.Parent != g.Root {
					ancestors = append(ancestors, parent.Parent)
				}
			}
			endingParents = ancestors
		}

		startingAdjustmentOrder := make([]*d2graph.Object, 0, len(startingAncestorPositions))
		for ancestor := range startingAncestorPositions {
			startingAdjustmentOrder = append(startingAdjustmentOrder, ancestor)
		}
		// adjust starting ancestors top-down
		sort.Slice(startingAdjustmentOrder, func(i, j int) bool {
			iPos := startingAncestorPositions[startingAdjustmentOrder[i]]
			jPos := startingAncestorPositions[startingAdjustmentOrder[j]]
			return iPos < jPos
		})

		endingAdjustmentOrder := make([]*d2graph.Object, 0, len(endingAncestorPositions))
		for ancestor := range endingAncestorPositions {
			endingAdjustmentOrder = append(endingAdjustmentOrder, ancestor)
		}

		// adjust ending ancestors bottom-up
		sort.Slice(endingAdjustmentOrder, func(i, j int) bool {
			iPos := endingAncestorPositions[endingAdjustmentOrder[i]]
			jPos := endingAncestorPositions[endingAdjustmentOrder[j]]
			return jPos < iPos
		})

		for _, ancestor := range endingAdjustmentOrder {
			var position float64
			if isHorizontal {
				position = ancestor.TopLeft.X + ancestor.Width
			} else {
				position = ancestor.TopLeft.Y + ancestor.Height
			}
			endDelta := endingAncestorPositions[ancestor] - position
			if endDelta > 0 {
				for _, obj := range g.Objects {
					if !obj.IsContainer() {
						continue
					}
					start := startingParentRanks[obj]
					end := endingParentRanks[obj]
					if start <= rank && rank <= end {
						if isHorizontal && position <= obj.TopLeft.X+obj.Width {
							obj.Width += endDelta
						} else if !isHorizontal &&
							position <= obj.TopLeft.Y+obj.Height {
							obj.Height += endDelta
						}
					}
				}
				shiftDown(g, position, endDelta, isHorizontal)
			}
		}

		for _, ancestor := range startingAdjustmentOrder {
			var position float64
			if isHorizontal {
				position = ancestor.TopLeft.X
			} else {
				position = ancestor.TopLeft.Y
			}
			startDelta := position - startingAncestorPositions[ancestor]
			if startDelta > 0 {
				for _, obj := range g.Objects {
					if !obj.IsContainer() {
						continue
					}
					start := startingParentRanks[obj]
					end := endingParentRanks[obj]
					if start <= rank && rank <= end {
						if isHorizontal && obj.TopLeft.X <= position {
							obj.Width += startDelta
						} else if !isHorizontal && obj.TopLeft.Y <= position {
							obj.Height += startDelta
						}
					}
				}
				shiftUp(g, position, startDelta, isHorizontal)
			}
		}
	}
}

func adjustCrossRankSpacing(g *d2graph.Graph, rankSep float64, isHorizontal bool) {
	var prevMarginTop, prevMarginBottom, prevMarginLeft, prevMarginRight map[*d2graph.Object]float64
	if isHorizontal {
		prevMarginLeft = make(map[*d2graph.Object]float64)
		prevMarginRight = make(map[*d2graph.Object]float64)
	} else {
		prevMarginTop = make(map[*d2graph.Object]float64)
		prevMarginBottom = make(map[*d2graph.Object]float64)
	}
	for _, obj := range g.Objects {
		if obj.IsGridDiagram() {
			continue
		}
		margin, padding := getSpacing(obj)
		if !isHorizontal {
			if prevShift, has := prevMarginBottom[obj]; has {
				margin.bottom -= prevShift
			}
			if margin.bottom > 0 {
				increased := shiftReachableDown(g, obj, obj.TopLeft.Y+obj.Height, margin.bottom, isHorizontal, true)
				for o := range increased {
					prevMarginBottom[o] = math.Max(prevMarginBottom[o], margin.bottom)
				}
			}
			if padding.bottom > 0 {
				shiftReachableDown(g, obj, obj.TopLeft.Y+obj.Height, padding.bottom, isHorizontal, false)
				obj.Height += padding.bottom
			}
			if prevShift, has := prevMarginTop[obj]; has {
				margin.top -= prevShift
			}
			if margin.top > 0 {
				increased := shiftReachableDown(g, obj, obj.TopLeft.Y, margin.top, isHorizontal, true)
				for o := range increased {
					prevMarginTop[o] = math.Max(prevMarginTop[o], margin.top)
				}
			}
			if padding.top > 0 {
				shiftReachableDown(g, obj, obj.TopLeft.Y, padding.top, isHorizontal, false)
				obj.Height += padding.top
			}
		} else {
			if prevShift, has := prevMarginRight[obj]; has {
				margin.right -= prevShift
			}
			if margin.right > 0 {
				increased := shiftReachableDown(g, obj, obj.TopLeft.X+obj.Width, margin.right, isHorizontal, true)
				for o := range increased {
					prevMarginRight[o] = math.Max(prevMarginRight[o], margin.right)
				}
			}
			if padding.right > 0 {
				shiftReachableDown(g, obj, obj.TopLeft.X+obj.Width, padding.right, isHorizontal, false)
				obj.Width += padding.right
			}
			if prevShift, has := prevMarginLeft[obj]; has {
				margin.left -= prevShift
			}
			if margin.left > 0 {
				increased := shiftReachableDown(g, obj, obj.TopLeft.X, margin.left, isHorizontal, true)
				for o := range increased {
					prevMarginLeft[o] = math.Max(prevMarginLeft[o], margin.left)
				}
			}
			if padding.left > 0 {
				shiftReachableDown(g, obj, obj.TopLeft.X, padding.left, isHorizontal, false)
				obj.Width += padding.left
			}
		}
	}
}

func fitContainerPadding(g *d2graph.Graph, rankSep float64, isHorizontal bool) {
	for _, obj := range g.Root.ChildrenArray {
		fitPadding(obj)
	}
}

func fitPadding(obj *d2graph.Object) {
	dslShape := strings.ToLower(obj.Shape.Value)
	shapeType := d2target.DSL_SHAPE_TO_SHAPE_TYPE[dslShape]
	// Note: there's no shape-specific padding/placement in dagre yet
	if !obj.IsContainer() || shapeType != shape.SQUARE_TYPE {
		return
	}
	for _, child := range obj.ChildrenArray {
		fitPadding(child)
	}

	_, padding := getSpacing(obj)
	padding.top = math.Max(padding.top, DEFAULT_PADDING)
	padding.bottom = math.Max(padding.bottom, DEFAULT_PADDING)
	padding.left = math.Max(padding.left, DEFAULT_PADDING)
	padding.right = math.Max(padding.right, DEFAULT_PADDING)

	innerTop := math.Inf(1)
	innerBottom := math.Inf(-1)
	innerLeft := math.Inf(1)
	innerRight := math.Inf(-1)

	for _, child := range obj.ChildrenArray {
		margin, _ := getSpacing(child)
		dx, dy := child.GetModifierElementAdjustments()

		innerTop = math.Min(innerTop, child.TopLeft.Y-dy-math.Max(margin.top, padding.top))
		innerBottom = math.Max(innerBottom, child.TopLeft.Y+child.Height+math.Max(margin.bottom, padding.bottom))
		innerLeft = math.Min(innerLeft, child.TopLeft.X-math.Max(margin.left, padding.left))
		innerRight = math.Max(innerRight, child.TopLeft.X+child.Width+dx+math.Max(margin.right, padding.right))
	}

	currentTop := obj.TopLeft.Y
	currentBottom := obj.TopLeft.Y + obj.Height
	currentLeft := obj.TopLeft.X
	currentRight := obj.TopLeft.X + obj.Width

	topDelta := innerTop - currentTop
	bottomDelta := currentBottom - innerBottom
	leftDelta := innerLeft - currentLeft
	rightDelta := currentRight - innerRight

	if 0 < topDelta {
		topDelta = adjustDeltaForEdges(obj, currentTop, topDelta, false)
		if 0 < topDelta {
			obj.TopLeft.Y += topDelta
			obj.Height -= topDelta
			adjustEdges(obj, currentTop, topDelta, false)
		}
	}
	if 0 < bottomDelta {
		bottomDelta = adjustDeltaForEdges(obj, currentBottom, -bottomDelta, false)
		if 0 < bottomDelta {
			obj.Height -= bottomDelta
			adjustEdges(obj, currentBottom, -bottomDelta, false)
		}
	}
	if 0 < leftDelta {
		leftDelta = adjustDeltaForEdges(obj, currentLeft, leftDelta, true)
		if 0 < leftDelta {
			obj.TopLeft.X += leftDelta
			obj.Width -= leftDelta
			adjustEdges(obj, currentLeft, leftDelta, true)
		}
	}
	if 0 < rightDelta {
		rightDelta = adjustDeltaForEdges(obj, currentRight, -rightDelta, true)
		if 0 < rightDelta {
			obj.Width -= rightDelta
			adjustEdges(obj, currentRight, -rightDelta, true)
		}
	}
}

func adjustDeltaForEdges(obj *d2graph.Object, objPosition, delta float64, isHorizontal bool) (newMagnitude float64) {
	isOnCollapsingSide := func(p *geo.Point) bool {
		var position float64
		if isHorizontal {
			position = p.X
		} else {
			position = p.Y
		}
		if geo.PrecisionCompare(position, objPosition, 1) == 0 {
			return false
		}
		// check for edges on side corners
		var isOnSide bool
		if isHorizontal {
			if geo.PrecisionCompare(p.Y, obj.TopLeft.Y, 1) == 0 ||
				geo.PrecisionCompare(p.Y, obj.TopLeft.Y+obj.Height, 1) == 0 {
				isOnSide = true
			}
		} else {
			if geo.PrecisionCompare(p.X, obj.TopLeft.X, 1) == 0 ||
				geo.PrecisionCompare(p.X, obj.TopLeft.X+obj.Width, 1) == 0 {
				isOnSide = true
			}
		}
		if isOnSide {
			var isInRange bool
			if delta > 0 {
				if objPosition < position && position < objPosition+delta {
					isInRange = true
				}
			} else {
				if objPosition+delta < position && position < objPosition {
					isInRange = true
				}
			}
			if !isInRange {
				if isHorizontal {
					return false
				} else {
					return false
				}
			}
		}
		return true
	}
	outermost := objPosition + delta
	for _, edge := range obj.Graph.Edges {
		if edge.Src == obj {
			p := edge.Route[0]
			if isOnCollapsingSide(p) {
				var position float64
				if isHorizontal {
					position = p.X
				} else {
					position = p.Y
				}
				if delta < 0 {
					outermost = math.Max(outermost, position)
				} else {
					outermost = math.Min(outermost, position)
				}
			}
		}
		if edge.Dst == obj {
			p := edge.Route[len(edge.Route)-1]
			if isOnCollapsingSide(p) {
				var position float64
				if isHorizontal {
					position = p.X
				} else {
					position = p.Y
				}
				if delta < 0 {
					outermost = math.Max(outermost, position)
				} else {
					outermost = math.Min(outermost, position)
				}
			}
		}
	}
	newMagnitude = math.Abs(delta)
	if outermost != objPosition+delta {
		// only reduce to outermost + DEFAULT_PADDING
		if delta < 0 {
			newMagnitude = math.Max(0, objPosition-(outermost+DEFAULT_PADDING))
		} else {
			newMagnitude = math.Max(0, (outermost-DEFAULT_PADDING)-objPosition)
		}
	}
	return newMagnitude
}

func adjustEdges(obj *d2graph.Object, objPosition, delta float64, isHorizontal bool) {
	adjust := func(p *geo.Point) {
		var position float64
		if isHorizontal {
			position = p.X
		} else {
			position = p.Y
		}
		if geo.PrecisionCompare(position, objPosition, 1) == 0 {
			if isHorizontal {
				p.X += delta
			} else {
				p.Y += delta
			}
		} else {
			// check side corners
			var isOnSide bool
			if isHorizontal {
				if geo.PrecisionCompare(p.Y, obj.TopLeft.Y, 1) == 0 ||
					geo.PrecisionCompare(p.Y, obj.TopLeft.Y+obj.Height, 1) == 0 {
					isOnSide = true
				}
			} else {
				if geo.PrecisionCompare(p.X, obj.TopLeft.X, 1) == 0 ||
					geo.PrecisionCompare(p.X, obj.TopLeft.X+obj.Width, 1) == 0 {
					isOnSide = true
				}
			}
			if isOnSide {
				var isInRange bool
				if delta > 0 {
					if objPosition < position && position < objPosition+delta {
						isInRange = true
					}
				} else {
					if objPosition+delta < position && position < objPosition {
						isInRange = true
					}
				}
				if isInRange {
					if isHorizontal {
						p.X = objPosition + delta
					} else {
						p.Y = objPosition + delta
					}
				}
			}
		}
	}

	for _, edge := range obj.Graph.Edges {
		if edge.Src == obj {
			adjust(edge.Route[0])
		}
		if edge.Dst == obj {
			adjust(edge.Route[len(edge.Route)-1])
		}
	}
}