type Edge interface {
	attributes.Styleable
	attributes.Serializable

	// From returns the tail node this Edge is connected from
	From() Node
	// From returns the head node this Edge is connected to
	To() Node
	// Edge creates an Edge to a Node using the head node of this Edge as tail
	Edge(to Node) Edge
	// Edge creates an Edge with the provided attributes to a Node using the head
	// node of this Edge as tail
	EdgeWithAttributes(to Node, attributes attributes.Reader) Edge
	// EdgesTo returns all edges between the head Node of this Edge and the target
	// Node
	EdgesTo(to Node) []Edge
}

type EdgeInitializerFn func(StyledEdge)

type Graph interface {
	attributes.Identity
	attributes.Styleable
	attributes.Serializable

	// Root returns the root graph (i.e. the topmost, without a parent graph)
	Root() Graph
	// Type returns the graph type: directed, undirected or sub
	Type() GraphType
	// FindSubgraph returns the subgraph of this graph or from one of its parents
	FindSubgraph(id string) (Graph, bool)
	// Subgraph creates a subgraph of this graph
	Subgraph(optionsFn ...GraphOptionFn) (Graph, error)
	// Node gets a node by id, or creates a new one if it doesn't exist
	Node(id string) Node
	// Edge creates a new edge between the two provided nodes
	Edge(n1, n2 Node) StyledEdge
	// Edge creates a new edge between the two provided nodes, and also set the
	// given attributes
	EdgeWithAttributes(n1, n2 Node, attributes attributes.Reader) StyledEdge
	// FindEdges gets all edges in the graph between the two provided nodes
	FindEdges(fromNode, toNode Node) (found []Edge)
	// FindNode gets a node by id
	FindNode(id string) (Node, bool)
	// VisitNodes runs the provided function on all nodes recursively
	VisitNodes(callback func(node Node) (done bool))
	// AddToSameRank adds the given nodes to the specified rank group, forcing
	// them to be rendered in the same row
	AddToSameRank(group string, nodes ...Node)
	// FindNodeByID return node by id
	FindNodeByID(id string) (foundNode Node, found bool)
	// FindNodes returns all nodes recursively
	FindNodes() (nodes []Node)
	// HasSubgraphs returns true if the graph has any subgraphs
	HasSubgraphs() bool
	// HasNodes returns true if the graph has any nodes
	HasNodes() bool
	// HasEdges returns true if the graph has any nodes
	HasEdges() bool
	// HasSameRankNodes returns true if the graph has nodes grouped as same rank
	HasSameRankNodes() bool
	// IsStrict return true if the graph is set as strict
	IsStrict() bool
}

type GraphOptionFn func(GraphOptions) error

type GraphOptions interface {
	// SetID changes the id
	SetID(string)
	// ID returns the id
	ID() string
	// SetParent changes the parent graph
	SetParent(Graph)
	// Parent return the parent graph
	Parent() Graph
	// SetType changes the graph type
	SetType(GraphType)
	// Type returns the graph type
	Type() GraphType
	// SetStrict changes the strict flag
	SetStrict(bool)
	// Strict returns the strict flag
	Strict() bool
	// SetGenerator changes the ID generator
	SetGenerator(generators.IDGenerator)
	// Generator return the ID generator
	Generator() generators.IDGenerator
	// SetNodeInitializer changes the node initializer function
	SetNodeInitializer(NodeInitializerFn)
	// NodeInitializer returns the node initializer function
	NodeInitializer() NodeInitializerFn
	// SetEdgeInitializer changes the node initializer function
	SetEdgeInitializer(EdgeInitializerFn)
	// EdgeInitializer returns the node initializer function
	EdgeInitializer() EdgeInitializerFn
	// SetCluster changes the cluster flag
	SetCluster(bool)
	// Cluster returns if the graph is a cluster
	Cluster() bool
}

type GraphType string

type Node interface {
	attributes.Identity
	attributes.Styleable
	attributes.Serializable

	// Edge creates an Edge to a Node
	Edge(to Node) Edge
	// EdgeWithAttributes creates an Edge with the provided attributes to a Node
	EdgeWithAttributes(to Node, attributes attributes.Reader) Edge
	// EdgesTo returns all edges between this Node and the target Node
	EdgesTo(to Node) []Edge
}

type NodeInitializerFn func(Node)

type StyledEdge interface {
	Edge
	// Solid sets the edge style to solid
	Solid() Edge
	// Solid sets the edge style to bold
	Bold() Edge
	// Solid sets the edge style to dashed
	Dashed() Edge
	// Solid sets the edge style to dotted
	Dotted() Edge
}

type StyledNode interface {
	Node
	// Box sets the node style to box
	Box() Node
}