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/build_conversion.go b/bp2build/build_conversion.go
index 07f492e..b1a6e2c 100644
--- a/bp2build/build_conversion.go
+++ b/bp2build/build_conversion.go
@@ -261,7 +261,7 @@
 
 	// Simple metrics tracking for bp2build
 	metrics := CodegenMetrics{
-		RuleClassCount: make(map[string]int),
+		ruleClassCount: make(map[string]int),
 	}
 
 	dirs := make(map[string]bool)
@@ -277,14 +277,28 @@
 
 		switch ctx.Mode() {
 		case Bp2Build:
+			// There are two main ways of converting a Soong module to Bazel:
+			// 1) Manually handcrafting a Bazel target and associating the module with its label
+			// 2) Automatically generating with bp2build converters
+			//
+			// bp2build converters are used for the majority of modules.
 			if b, ok := m.(android.Bazelable); ok && b.HasHandcraftedLabel() {
-				metrics.handCraftedTargetCount += 1
-				metrics.TotalModuleCount += 1
-				metrics.AddConvertedModule(m.Name())
+				// Handle modules converted to handcrafted targets.
+				//
+				// Since these modules are associated with some handcrafted
+				// target in a BUILD file, we simply append the entire contents
+				// of that BUILD file to the generated BUILD file.
+				//
+				// The append operation is only done once, even if there are
+				// multiple modules from the same directory associated to
+				// targets in the same BUILD file (or package).
+
+				// Log the module.
+				metrics.AddConvertedModule(m.Name(), Handcrafted)
+
 				pathToBuildFile := getBazelPackagePath(b)
-				// We are using the entire contents of handcrafted build file, so if multiple targets within
-				// a package have handcrafted targets, we only want to include the contents one time.
 				if _, exists := buildFileToAppend[pathToBuildFile]; exists {
+					// Append the BUILD file content once per package, at most.
 					return
 				}
 				t, err := getHandcraftedBuildContent(ctx, b, pathToBuildFile)
@@ -297,23 +311,29 @@
 				// something more targeted based on the rule type and target
 				buildFileToAppend[pathToBuildFile] = true
 			} else if aModule, ok := m.(android.Module); ok && aModule.IsConvertedByBp2build() {
+				// Handle modules converted to generated targets.
+
+				// Log the module.
+				metrics.AddConvertedModule(m.Name(), Generated)
+
+				// Handle modules with unconverted deps. By default, emit a warning.
 				if unconvertedDeps := aModule.GetUnconvertedBp2buildDeps(); len(unconvertedDeps) > 0 {
 					msg := fmt.Sprintf("%q depends on unconverted modules: %s", m.Name(), strings.Join(unconvertedDeps, ", "))
 					if ctx.unconvertedDepMode == warnUnconvertedDeps {
 						metrics.moduleWithUnconvertedDepsMsgs = append(metrics.moduleWithUnconvertedDepsMsgs, msg)
 					} else if ctx.unconvertedDepMode == errorModulesUnconvertedDeps {
-						metrics.TotalModuleCount += 1
 						errs = append(errs, fmt.Errorf(msg))
 						return
 					}
 				}
 				targets = generateBazelTargets(bpCtx, aModule)
-				metrics.AddConvertedModule(m.Name())
 				for _, t := range targets {
-					metrics.RuleClassCount[t.ruleClass] += 1
+					// A module can potentially generate more than 1 Bazel
+					// target, each of a different rule class.
+					metrics.IncrementRuleClassCount(t.ruleClass)
 				}
 			} else {
-				metrics.TotalModuleCount += 1
+				metrics.IncrementUnconvertedCount()
 				return
 			}
 		case QueryView:
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
+	}
 }