// For users of this class: Don't fill the maps directly, call
// mapAnchor + mapCurve.

srecord noeq G22MeshMapping(G22Mesh mesh1, G22Mesh mesh2) {
  delegate Anchor, Curve to G22Mesh.
  
  // A mapping of a curve to another curve may be "flipped"
  // (start becomes end and end becomes start)
  srecord MappedCurve(Curve curve, bool flipped) {
    Curve get() { ret curve; }
    
    Anchor start() { ret curve.anchor(flipped); }
    Anchor end()   { ret curve.anchor(!flipped); }
  }

  // For both maps: keys are from mesh1, values are from mesh2
  new BijectiveMap<Anchor> anchorMap;
  
  // forward (mesh1 -> mesh2) and backward (mesh2 -> mesh1)
  new Map<Curve, MappedCurve> curveMap;
  new Map<Curve, MappedCurve> curveBackwardMap;
  
  // General validity check that should cover all bases
  
  void validityCheck() {
    // For anchors, we only need to check that they come from the
    // right meshes. Bijectiveness is ensured by anchorMap itself.
    
    for (a1, a2 : anchorMap) {
      assertTrue(mesh1.containsAnchor(a1));
      assertTrue(mesh2.containsAnchor(a2));
    }
    
    for (c1, c2 : curveMap) {
      assertTrue(mesh1.containsCurve(c1));
      assertTrue(mesh2.containsCurve(c2!));
      
      // Check compatibility with anchor mappings
      
      assertEquals(c2.start(), getAnchorMapping(c1.start));
      assertEquals(c2.end(), getAnchorMapping(c1.end));
    }
  }
  
  // A mapping is complete iff all anchors and curves from both
  // meshes are covered.
  
  bool isComplete() {
    ret allEq(l(anchorMap), l(mesh1.anchors()), l(mesh2.anchors()))
      && allEq(l(curveMap), l(mesh1.curves()), l(mesh2.curves()));
  }
  
  void mapAnchor(Anchor a1, Anchor a2) {
    anchorMap.put(a1, a2);
  }
  
  void mapCurve(Curve c1, Curve c2, bool flipped) {
    curveMap.put(c1, new MappedCurve(c2, flipped));
    curveBackwardMap.put(c2, new MappedCurve(c1, flipped));
  }
  
  Anchor getAnchorMapping aka get(Anchor a) {
    ret anchorMap.get(a);
  }
  
  MappedCurve getCurveMapping aka get(Curve c) {
    ret curveMap.get(c);
  }
  
  bool isMapped(Anchor a1) {
    ret get(a1) != null;
  }
  
  bool isMapped(Curve c1) {
    ret get(c1) != null;
  }
}