package d2layouts

import (
	"strings"

	"oss.terrastruct.com/d2/d2graph"
)

type GraphType string

const (
	DefaultGraphType  GraphType = ""
	ConstantNearGraph GraphType = "constant-near"
	GridDiagram       GraphType = "grid-diagram"
	SequenceDiagram   GraphType = "sequence-diagram"
)

func LayoutNested(g *d2graph.Graph, graphType GraphType, coreLayout d2graph.LayoutGraph) {
	// Before we can layout these nodes, we need to handle all nested diagrams first.
	extracted := make(map[*d2graph.Object]*d2graph.Graph)

	// Iterate top-down from Root so all nested diagrams can process their own contents
	queue := make([]*d2graph.Object, 0, len(g.Root.ChildrenArray))
	queue = append(queue, g.Root.ChildrenArray...)

	for _, child := range queue {
		if graphType := NestedGraphType(child); graphType != DefaultGraphType {
			// There is a nested diagram here, so extract its contents and process in the same way
			nestedGraph := ExtractNested(child)

			// Layout of nestedGraph is completed
			LayoutNested(nestedGraph, graphType, coreLayout)

			// Fit child to size of nested layout
			FitToGraph(child, nestedGraph)

			// We will restore the contents after running layout with child as the placeholder
			extracted[child] = nestedGraph
		} else if len(child.Children) > 0 {
			queue = append(queue, child.ChildrenArray...)
		}
	}

	// We can now run layout with accurate sizes of nested layout containers
	// Layout according to the type of diagram
	LayoutDiagram(g, graphType, coreLayout)

	// With the layout set, inject all the extracted graphs
	for n, nestedGraph := range extracted {
		InjectNested(n, nestedGraph)
	}
}

func NestedGraphType(obj *d2graph.Object) GraphType {
	if obj.Graph.RootLevel == 0 && obj.IsConstantNear() {
		return ConstantNearGraph
	}
	if obj.IsGridDiagram() {
		return GridDiagram
	}
	if obj.IsSequenceDiagram() {
		return SequenceDiagram
	}
	return DefaultGraphType
}

func ExtractNested(container *d2graph.Object) *d2graph.Graph {
	tempGraph := d2graph.NewGraph()
	tempGraph.RootLevel = int(container.Level())

	// separate out nested edges
	g := container.Graph
	remainingEdges := make([]*d2graph.Edge, 0, len(g.Edges))
	for _, edge := range g.Edges {
		if edge.Src.Parent.IsDescendantOf(container) && edge.Dst.Parent.IsDescendantOf(container) {
			tempGraph.Edges = append(tempGraph.Edges, edge)
		} else {
			remainingEdges = append(remainingEdges, edge)
		}
	}
	g.Edges = remainingEdges

	// separate out nested objects
	remainingObjects := make([]*d2graph.Object, 0, len(g.Objects))
	for _, obj := range g.Objects {
		if obj.IsDescendantOf(container) {
			tempGraph.Objects = append(tempGraph.Objects, obj)
		} else {
			remainingObjects = append(remainingObjects, obj)
		}
	}
	g.Objects = remainingObjects

	// update object and new root references
	for _, o := range tempGraph.Objects {
		o.Graph = tempGraph
	}
	// set root references
	tempGraph.Root.ChildrenArray = append(tempGraph.Root.ChildrenArray, container.ChildrenArray...)
	for _, child := range container.ChildrenArray {
		child.Parent = tempGraph.Root
		tempGraph.Root.Children[strings.ToLower(child.ID)] = child
	}

	// remove container's references
	for k := range container.Children {
		delete(container.Children, k)
	}
	container.ChildrenArray = nil

	return tempGraph
}

func InjectNested(container *d2graph.Object, graph *d2graph.Graph) {
	// TODO
}

func FitToGraph(container *d2graph.Object, graph *d2graph.Graph) {
	// TODO
}

func LayoutDiagram(graph *d2graph.Graph, graphType GraphType, coreLayout d2graph.LayoutGraph) {
	// TODO
}