package graphs

import "slices"

// DirectedGraph
type DirectedGraph[T comparable] struct {
	adjList map[T][]T
}

// NewDirectedGraph() -> Creates a Directed Graph
func NewDirectedGraph[T comparable]() *DirectedGraph[T] {
	gp := &DirectedGraph[T]{
		adjList: make(map[T][]T),
	}

	return gp
}

// AddIsolatedVertex() -> Creates an isolated Vertex returns True if ok ,
// false if vertex already exist
func (gp *DirectedGraph[T]) AddIsolatedVertex(newVertex T) bool {
	_, ok := gp.adjList[newVertex]
	if !ok {
		gp.adjList[newVertex] = make([]T, 0)
		return true
	}
	return false
}

// AddVertex() -> Creates a directed edge newVertex -> toVertex. Creates both
// vertices if they dont exist.
func (gp *DirectedGraph[T]) AddVertex(newVertex T, toVertex T) {
	// self loops are not allowed in this graph
	if newVertex == toVertex {
		return
	}

	gp.AddIsolatedVertex(newVertex)
	gp.AddIsolatedVertex(toVertex)

	// directed: only store the edge on the source's out-list, once.
	if !slices.Contains(gp.adjList[newVertex], toVertex) {
		gp.adjList[newVertex] = append(gp.adjList[newVertex], toVertex)
	}
}

// Order() -> returns the amount of Vertices
func (gp *DirectedGraph[T]) Order() int {
	return len(gp.adjList)
}

// Size() -> returns the amount of Edges
func (gp *DirectedGraph[T]) Size() int {
	var size int

	// directed: each edge is stored once, so no halving.
	for _, val := range gp.adjList {
		size += len(val)
	}
	return size
}

// Display() -> returns adjList[map]T []T
func (gp *DirectedGraph[T]) Display() map[T][]T {
	return gp.adjList
}