// Transform uses graphs to add network interfaces to Seeds
func Transform(orig *seed.Seed) (*seed.Seed, error) {
// build graph
g := seedGraph.SeedAsGraph(orig)
orig.Name = strings.Title(orig.Name) + "Server"
for inputName, input := range orig.Collections {
if input.Type != seed.CollectionInput {
continue
}
input.Key = append([]string{"@address"}, input.Key...)
start, ok := g.NodeFor(inputName)
if !ok {
panic("could not find node for " + inputName)
}
for outputName, output := range orig.Collections {
if output.Type != seed.CollectionOutput {
continue
}
goal, ok := g.NodeFor(outputName)
if !ok {
panic("could not find node for " + outputName)
}
path, cost, _ := graph.AStar(start, goal, g, cost, nil)
if math.IsInf(cost, 0) {
// there is no path (that does not go through a table)
continue
}
outputAddress := outputName + "_addr"
previousCollection := inputName
for _, node := range path[:len(path)] {
// unbox graph.internalNode;
node = g.GetNode(node.ID())
switch node := node.(type) {
case seedGraph.CollectionNode:
previousCollection = node.Name
switch node.Collection.Type {
case seed.CollectionInput, seed.CollectionScratch:
node.Collection.Key = prependIfNotExists(node.Collection.Key, outputAddress)
case seed.CollectionOutput:
node.Collection.Key = prependIfNotExists(node.Collection.Key, "@"+outputAddress)
case seed.CollectionChannel, seed.CollectionTable:
panic("should not encounter these collection types")
default:
panic(fmt.Sprintf("unhandled type: %d", node.Collection.Type))
}
case seedGraph.RuleNode:
exists := false
for _, expression := range node.Rule.Intension {
switch expression := expression.(type) {
case seed.QualifiedColumn:
if expression.Column == outputAddress {
// if a reference to the outputAddress already exists (i.e., from being added by another flow)
// then add a constraint to make the rows match up
node.Rule.Predicate = append(node.Rule.Predicate, seed.Constraint{
Left: expression,
Right: seed.QualifiedColumn{
Collection: previousCollection,
Column: outputAddress,
},
})
exists = true
}
case seed.MapFunction, seed.ReduceFunction:
continue
default:
panic(fmt.Sprintf("unhandled type: %v", reflect.TypeOf(expression).String()))
}
}
if !exists {
// add to the projection
node.Rule.Intension = append([]seed.Expression{seed.QualifiedColumn{
Collection: previousCollection,
Column: outputAddress,
}}, node.Rule.Intension...)
}
default:
panic(fmt.Sprintf("unhandled type: %v", reflect.TypeOf(node).String()))
}
}
}
}
// change inputs and outputs to channels
for _, collection := range orig.Collections {
switch collection.Type {
case seed.CollectionInput, seed.CollectionOutput:
collection.Type = seed.CollectionChannel
case seed.CollectionScratch, seed.CollectionTable, seed.CollectionChannel:
// no-op
default:
panic(collection.Type)
}
}
// rules supplying channels must be asynchronous
for _, rule := range orig.Rules {
collectionName := rule.Supplies
collection, ok := orig.Collections[collectionName]
if !ok {
// should never happen
panic(collectionName)
}
if collection.Type == seed.CollectionChannel {
rule.Operation = "<~"
}
}
return orig, nil
}
