Track the buffer and slot name each variable refers to

This will be used to handle print statements in pyactr (#32)

actr/chunk.go

@@ -23,6 +23,11 @@ func (model Model) LookupChunk(chunkName string) *Chunk {
 	return nil
 }
 
+// SlotName returns the name of the slot given the index.
+func (c Chunk) SlotName(index int) (str string) {
+	return c.SlotNames[index]
+}
+
 func (c Chunk) IsInternal() bool {
 	return c.Name[0] == '_'
 }

actr/production.go

@@ -6,12 +6,21 @@ type Production struct {
 	Name        string
 	Description *string // optional description to output as a comment in the generated code
 
+	VarIndexMap map[string]VarIndex // track the buffer and slot name each variable refers to
+
 	Matches      []*Match
 	DoStatements []*Statement
 
 	AMODLineNumber int // line number in the amod file of the this production
 }
 
+// VarIndex is used to track which buffer slot a variable refers to
+type VarIndex struct {
+	Var      string
+	Buffer   BufferInterface
+	SlotName string
+}
+
 type Match struct {
 	Buffer  BufferInterface
 	Pattern *Pattern

amod/amod.go

@@ -369,6 +369,7 @@ func addProductions(model *actr.Model, log *amodlog.Log, productions *production
 		prod := actr.Production{
 			Name:           production.Name,
 			Description:    production.Description,
+			VarIndexMap:    map[string]actr.VarIndex{},
 			AMODLineNumber: production.Pos.Line,
 		}
 
@@ -384,12 +385,31 @@ func addProductions(model *actr.Model, log *amodlog.Log, productions *production
 			}
 
 			name := item.Name
-
-			prod.Matches = append(prod.Matches, &actr.Match{
+			match := actr.Match{
 				Buffer:  model.LookupBuffer(name),
 				Pattern: pattern,
-			})
+			}
+
+			prod.Matches = append(prod.Matches, &match)
 
+			for index, slot := range pattern.Slots {
+				item := slot.Items[0]
+
+				if item.Var == nil {
+					continue
+				}
+
+				// Track the buffer and slot name the variable refers to
+				varItem := *item.Var
+				if _, ok := prod.VarIndexMap[varItem]; !ok {
+					varIndex := actr.VarIndex{
+						Var:      varItem,
+						Buffer:   match.Buffer,
+						SlotName: pattern.Chunk.SlotName(index),
+					}
+					prod.VarIndexMap[varItem] = varIndex
+				}
+			}
 		}
 
 		if production.Do.Statements != nil {

amod/validate.go

@@ -177,7 +177,7 @@ func validateSetStatement(set *setStatement, model *actr.Model, log *amodlog.Log
 
 			for slotIndex, slot := range set.Pattern.Slots {
 				if len(slot.Items) > 1 {
-					log.Error(set.Pattern.Pos.Line, "cannot set '%s.%v' to compound var in production '%s'", bufferName, chunk.SlotNames[slotIndex], production.Name)
+					log.Error(set.Pattern.Pos.Line, "cannot set '%s.%v' to compound var in production '%s'", bufferName, chunk.SlotName(slotIndex), production.Name)
 					err = CompileError{}
 
 					continue
@@ -193,8 +193,7 @@ func validateSetStatement(set *setStatement, model *actr.Model, log *amodlog.Log
 				match := production.LookupMatchByVariable(varItem)
 				if match == nil {
 					if varItem == "?" {
-
-						log.Error(set.Pattern.Pos.Line, "cannot set '%s.%v' to anonymous var ('?') in production '%s'", bufferName, chunk.SlotNames[slotIndex], production.Name)
+						log.Error(set.Pattern.Pos.Line, "cannot set '%s.%v' to anonymous var ('?') in production '%s'", bufferName, chunk.SlotName(slotIndex), production.Name)
 					} else {
 						log.Error(set.Pattern.Pos.Line, "set statement variable '%s' not found in matches for production '%s'", varItem, production.Name)
 					}