Start adding code generation

src/code_gen/main.jl

@@ -0,0 +1,32 @@
+using DataStructures
+
+function gen_code(graph::DAG)
+    code = Vector{Expr}()
+    sizehint!(code, length(graph.nodes))
+
+    nodeQueue = PriorityQueue{Node, Int}()
+    inputSyms = Vector{Symbol}()
+
+    for node in get_entry_nodes(graph)
+        enqueue!(nodeQueue, node => 1)
+        push!(inputSyms, Symbol("data_$(replace(string(node.id), "-"=>"_"))_in"))
+    end
+
+    node = nothing
+    while !isempty(nodeQueue)
+        prio = peek(nodeQueue)[2]
+        node = dequeue!(nodeQueue)
+
+        push!(code, get_expression(node))
+        for parent in node.parents
+            if (!haskey(nodeQueue, parent))
+                enqueue!(nodeQueue, parent => prio + length(parent.children))
+            end
+        end
+    end
+
+    # node is now the last node we looked at -> the output node
+    outSym = Symbol("data_$(replace(string(node.id), "-"=>"_"))")
+    
+    return (code = Expr(:block, code...), inputSymbols = inputSyms, outputSymbol = outSym)
+end