bp2build: Refactor metrics collection to use exported functions.

This CL splits the metric count into handcrafted, generated, and
unconverted modules.

Test: CI
Test: m bp2build, the metrics reported are identical.
Change-Id: I80e3d2fd2989222bd40b6433b4a1924b4943d0ba
diff --git a/bp2build/metrics.go b/bp2build/metrics.go
index 9e7b3b6..1cc4143 100644
--- a/bp2build/metrics.go
+++ b/bp2build/metrics.go
@@ -9,14 +9,17 @@
 // Simple metrics struct to collect information about a Blueprint to BUILD
 // conversion process.
 type CodegenMetrics struct {
-	// Total number of Soong/Blueprint modules
-	TotalModuleCount int
+	// Total number of Soong modules converted to generated targets
+	generatedModuleCount int
+
+	// Total number of Soong modules converted to handcrafted targets
+	handCraftedModuleCount int
+
+	// Total number of unconverted Soong modules
+	unconvertedModuleCount int
 
 	// Counts of generated Bazel targets per Bazel rule class
-	RuleClassCount map[string]int
-
-	// Total number of handcrafted targets
-	handCraftedTargetCount int
+	ruleClassCount map[string]int
 
 	moduleWithUnconvertedDepsMsgs []string
 
@@ -26,22 +29,49 @@
 // Print the codegen metrics to stdout.
 func (metrics *CodegenMetrics) Print() {
 	generatedTargetCount := 0
-	for _, ruleClass := range android.SortedStringKeys(metrics.RuleClassCount) {
-		count := metrics.RuleClassCount[ruleClass]
+	for _, ruleClass := range android.SortedStringKeys(metrics.ruleClassCount) {
+		count := metrics.ruleClassCount[ruleClass]
 		fmt.Printf("[bp2build] %s: %d targets\n", ruleClass, count)
 		generatedTargetCount += count
 	}
 	fmt.Printf(
 		"[bp2build] Generated %d total BUILD targets and included %d handcrafted BUILD targets from %d Android.bp modules.\n With %d modules with unconverted deps \n\t%s",
 		generatedTargetCount,
-		metrics.handCraftedTargetCount,
-		metrics.TotalModuleCount,
+		metrics.handCraftedModuleCount,
+		metrics.TotalModuleCount(),
 		len(metrics.moduleWithUnconvertedDepsMsgs),
 		strings.Join(metrics.moduleWithUnconvertedDepsMsgs, "\n\t"))
 }
 
-func (metrics *CodegenMetrics) AddConvertedModule(moduleName string) {
+func (metrics *CodegenMetrics) IncrementRuleClassCount(ruleClass string) {
+	metrics.ruleClassCount[ruleClass] += 1
+}
+
+func (metrics *CodegenMetrics) IncrementUnconvertedCount() {
+	metrics.unconvertedModuleCount += 1
+}
+
+func (metrics *CodegenMetrics) TotalModuleCount() int {
+	return metrics.handCraftedModuleCount +
+		metrics.generatedModuleCount +
+		metrics.unconvertedModuleCount
+}
+
+type ConversionType int
+
+const (
+	Generated ConversionType = iota
+	Handcrafted
+)
+
+func (metrics *CodegenMetrics) AddConvertedModule(moduleName string, conversionType ConversionType) {
 	// Undo prebuilt_ module name prefix modifications
 	moduleName = android.RemoveOptionalPrebuiltPrefix(moduleName)
 	metrics.convertedModules = append(metrics.convertedModules, moduleName)
+
+	if conversionType == Handcrafted {
+		metrics.handCraftedModuleCount += 1
+	} else if conversionType == Generated {
+		metrics.generatedModuleCount += 1
+	}
 }