;;;; Copyright (c) 2015, Jeremy Steward
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(test-begin "MultiGraph Properties")
(test-group "identity properties"
  (let* ([v (gen-vertex-obj)]
         [G1 (make-multigraph)]
         [G2 (graph-vertex-remove (graph-vertex-add G1 v) v)])
    (test-assert "Vertex identity - adjacency lists should be empty"
                 (and (equal? (graph->list G1) '())
                      (equal? (graph->list G2) '()))))

  (let ([u (gen-vertex-obj)]
        [v (gen-vertex-obj)]
        [id (random-integer 100)])
    (let* ([G1 (make-multigraph)]
           [G2 (graph-edge-remove (graph-edge-add G1 u v id) u v id)])
      (test-assert "Edge identity - v should not be adjacent to u"
        (not (graph-adjacent? G2 u v id)))
      (test-assert "Edge identity - u should not be adjacent to v"
        (not (graph-adjacent? G2 v u id)))
      (test-assert "Edge identity - neighbours of u should be empty set"
        (set-null? (graph-neighbours G2 u)))
      (test-assert "Edge identity - neighbours of v should be empty set"
        (set-null? (graph-neighbours G2 v)))
      (test-assert "Edge identity - vertex u should still exist despite edge removal"
        (graph-vertex-exists? G2 u))
      (test-assert "Edge identity - vertex v should still exist despite edge removal"
        (graph-vertex-exists? G2 v))
      (test-assert "Edge identity - original graph should not contain u->v"
        (not (graph-adjacent? G1 u v)))
      (test-assert "Edge identity - original graph should not have u or v vertices"
        (not (or (graph-vertex-exists? G1 u)
                 (graph-vertex-exists? G1 v)))))))

(test-group "commutativity properties"
  (let* ([u (gen-vertex-obj)]
         [v (let loop ([v (gen-vertex-obj)])
              (if (equal? u v) (loop (gen-vertex-obj)) v))]
         [id (random-integer 100)])
    (let* ([G1 (make-multigraph)]
           [G2 (graph-vertex-add (graph-vertex-add G1 u) v)]
           [G3 (graph-vertex-add (graph-vertex-add G1 v) u)]
           [G4 (graph-vertex-remove (graph-vertex-remove G2 u) v)]
           [G5 (graph-vertex-remove (graph-vertex-remove G2 v) u)])
      (test-assert "Vertex commutativity - u should be present in both graphs"
                   (and (graph-vertex-exists? G2 u)
                        (graph-vertex-exists? G3 u)))
      (test-assert "Vertex commutativity - v should be present in both graphs"
                   (and (graph-vertex-exists? G2 v)
                        (graph-vertex-exists? G3 v)))
      (test-assert "Vertex commutativity - order of removal should not matter"
                   (and (not (or (graph-vertex-exists? G4 u)
                                 (graph-vertex-exists? G4 v)))
                        (not (or (graph-vertex-exists? G5 u)
                                 (graph-vertex-exists? G5 v))))))

    (let* ([G1 (make-multigraph)]
           [G2 (graph-edge-add G1 u v id)]
           [G3 (graph-edge-add G1 v u id)]
           [G4 (graph-edge-remove G2 u v id)]
           [G5 (graph-edge-remove G2 v u id)])
      (test-assert "Edge commutativity - u should be adjacent to v"
        (and (graph-adjacent? G2 u v id)
             (graph-adjacent? G3 u v id)))
      (test-assert "Edge commutativity - v should be adjacent to u"
        (and (graph-adjacent? G2 v u id)
             (graph-adjacent? G3 v u id)))
      (test-assert "Edge commutativity - removing edge u<->v: order should not matter"
        (not (or (graph-adjacent? G4 u v id)
                 (graph-adjacent? G4 v u id)
                 (graph-adjacent? G5 u v id)
                 (graph-adjacent? G5 v u id)))))))

(test-end "MultiGraph Properties")