;;;; Copyright (c) 2015, Jeremy Steward
;;;; All rights reserved.
;;;;
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;;; NOTE: Bear in mind all the procedures in the following files must first be
;;; defined in the graphs module:
;;;
;;;     src/utils
;;;     src/low-level
;;;     src/classes
;;;     src/multidigraph
;;;

(define (make-multigraph #!rest attr)
  (make <multigraph>
        'gattr (parse-graph-attr attr)))

(define-method (print-object (object <multigraph>) port)
  (display "MultiGraph\n" port)
  (display "----------\n" port)
  (hash-table-for-each (graph-vertex-attr object)
                       (lambda (key val)
                         (display key port)
                         (display " |-> " port)
                         (display (graph-neighbours object key) port))))

(define-method (graph-copy (g <multigraph>))
  (make <multigraph>
        'gattr (hash-table-copy (graph-attr g))
        'vattr (hash-table-copy (graph-vertex-attr g))
        'atbl (hash-table-copy (adjacency-table g))))

(define-method (graph-adjacent? (g <multigraph>) u v #!optional (id #f))
  @("Tests whether an edge u->v and v->u exists in graph g"
    (g "The graph to test")
    (u "The head vertex")
    (v "The tail vertex")
    (id "The ID of the edge to check for")
    (@to "bool")
    (@no-source))
  (cond
    [(not (and (graph-vertex-exists? g u)
               (graph-vertex-exists? g v)))
     #f]
    [(and (set-in v (set-map car (graph-neighbours g u)))
          (set-in u (set-map car (graph-neighbours g v))))
     (if id
       (set-in id (set-map cadr (set-filter (lambda (x)
                                              (equal? (car x) v))
                                            (graph-neighbours g u))))
       #t)]
    [(or (set-in v (set-map car (graph-neighbours g u)))
         (set-in u (set-map car (graph-neighbours g v))))
     (error 'graph-adjacent?
            "Undirected graph has unbalanced edges")]
    [else #f]))

(define-method (graph-edge-add (g <multigraph>) u v id #!rest attr)
  @("Adds an edge u->v that does not already exist within the graph g. (Non-destructive)"
    "If the graph is not a digraph, also adds v->u to balance the graph."
    (g "The graph of which to update")
    (u "The head vertex")
    (v "The tail vertex")
    (id "Unique identifier for the edge (to differentiate it from other edges from u->v)")
    (attr "A list of keywords and their corresponding values that define attributes for the edge.")
    (weight "Specific keyword in the edge attributes that corresponds to the edge weight.")
    (@to "<multigraph>")
    (@no-source))
  (let ([new-graph (graph-copy g)]
        [attr (cons id: (cons id attr))])
    (unless (graph-vertex-exists? new-graph u)
      (graph-vertex-add! new-graph u))
    (unless (graph-vertex-exists? new-graph v)
      (graph-vertex-add! new-graph v))
    (multiedge-add! new-graph u v attr)
    (unless (equal? u v)
      (multiedge-add! new-graph v u attr))
    new-graph))

(define-method (graph-edge-add! (g <multigraph>) u v id #!rest attr)
  @("Adds an edge u->v that does not already exist within the graph g. (Destructive)"
    "If the graph is not a digraph, also adds v->u to balance the graph."
    (g "The graph of which to update")
    (u "The head vertex")
    (v "The tail vertex")
    (id "Unique identifier for the edge (to differentiate it from other edges from u->v)")
    (attr "A list of keywords and their corresponding values that define attributes for the edge.")
    (weight "Specific keyword in the edge attributes that corresponds to the edge weight.")
    (@no-source))
  (let ([attr (cons id: (cons id attr))])
   (if (not (graph-vertex-exists? g u))
     (graph-vertex-add! g u))
   (if (not (graph-vertex-exists? g v))
     (graph-vertex-add! g v))
   (multiedge-add! g u v attr)
   (unless (equal? u v)
     (multiedge-add! g v u attr))))

(define-method (graph-edge-remove (g <multigraph>) u v #!optional (id #f))
  @("Removes an edge u->v and v->u with identity `id` from a graph. (Non-destructive)"
    "If no edge with the corresponding ID can be found, an error is raised."
    "If ID is false, then all edges u->v (and v->u) are removed."
    (g "The multigraph to remove the edge from.")
    (u "The head vertex")
    (v "The tail vertex")
    (@to "<multigraph>")
    (@no-source))
  (let ([new-graph (graph-copy g)])
   (cond
     [id
      (multiedge-remove! new-graph u v id)
      (unless (equal? u v)
        (multiedge-remove! new-graph v u id))]
     [else
      (edge-remove! new-graph u v)
      (unless (equal? u v)
        (edge-remove! new-graph v u))])
   new-graph))

(define-method (graph-edge-remove! (g <multigraph>) u v #!optional (id #f))
  @("Removes an edge u->v and v->u with identity `id` from a graph. (Destructive)"
    "If no edge with the corresponding ID can be found, an error is raised."
    "If ID is false, then all edges u->v (and v->u) are removed."
    (g "The multigraph to remove the edge from.")
    (u "The head vertex")
    (v "The tail vertex")
    (@no-source))
  (cond
    [id
     (multiedge-remove! g u v id)
     (unless (equal? u v)
       (multiedge-remove! g v u id))]
    [else
     (edge-remove! g u v)
     (unless (equal? u v)
       (edge-remove! g v u))]))

(define-method (graph-edge-update (g <multigraph>) u v id #!rest attr)
  @("Updates the edges u->v and v->u with ID := `id` present within a multigraph g. (Non-destructive)"
    "If `id` is #f then all edges u->v and v->u are updated."
    (g "The graph of which to update")
    (u "The base vertex")
    (v "The extended vertex")
    (@to "<multigraph>")
    (@no-source))
  (let ([new-graph (graph-copy g)])
   (multiedge-update! new-graph u v id attr)
   (unless (equal? u v)
     (multiedge-update! new-graph v u id attr))
   new-graph))

(define-method (graph-edge-update! (g <multigraph>) u v id #!rest attr)
  @("Updates the edges u->v and v->u with ID := `id` present within a multigraph g. (Destructive)"
    "If `id` is #f then all edges u->v and v->u are updated."
    (g "The graph of which to update")
    (u "The base vertex")
    (v "The extended vertex")
    (@no-source))
  (multiedge-update! g u v id attr)
  (unless (equal? u v)
    (multiedge-update! g v u id attr)))

(define-method (graph-degree (g <multigraph>) u #!key (weighted #t))
  (graph-outdegree g u weighted: weighted))