SdkSpec is fully using ApiLevel

Previously, SdkSpec was constructed only from the user string. It didn't
make use of the Config struct where information about the latest stable
SDK version, etc. is recorded. As a result, the build system couldn't
check if the sdk version "current" is referring to the in-development
(i.e.  not-yet-frozen) SDK version or the latest stable version.
"current" was always assumed to be in-development (IsPreview() returns
true) even when Platform_sdk_final == true.

As the first step for fixing that, this change requires
android.EarlyModuleContext to be passed when constructing SdkSpec from
the user string.

In the following changes, "current" will be mapped to either
FutureApiLevel (10000) or one of the FinalApiLevels() depending on
whether the platform SDK was finalized or not.

Bug: 175678607
Test: m
Change-Id: Ifea12ebf147ecccf12e7266dd382819806571543
diff --git a/android/sdk_version.go b/android/sdk_version.go
index 5fdaa91..98db824 100644
--- a/android/sdk_version.go
+++ b/android/sdk_version.go
@@ -22,15 +22,15 @@
 
 type SdkContext interface {
 	// SdkVersion returns SdkSpec that corresponds to the sdk_version property of the current module
-	SdkVersion() SdkSpec
+	SdkVersion(ctx EarlyModuleContext) SdkSpec
 	// SystemModules returns the system_modules property of the current module, or an empty string if it is not set.
 	SystemModules() string
 	// MinSdkVersion returns SdkSpec that corresponds to the min_sdk_version property of the current module,
 	// or from sdk_version if it is not set.
-	MinSdkVersion() SdkSpec
+	MinSdkVersion(ctx EarlyModuleContext) SdkSpec
 	// TargetSdkVersion returns the SdkSpec that corresponds to the target_sdk_version property of the current module,
 	// or from sdk_version if it is not set.
-	TargetSdkVersion() SdkSpec
+	TargetSdkVersion(ctx EarlyModuleContext) SdkSpec
 }
 
 // SdkKind represents a particular category of an SDK spec like public, system, test, etc.
@@ -201,15 +201,23 @@
 	return ctx.Config().DefaultAppTargetSdk(ctx).String(), nil
 }
 
-func SdkSpecFrom(str string) SdkSpec {
+var (
+	SdkSpecNone = SdkSpec{SdkNone, NoneApiLevel, "(no version)"}
+	// TODO(b/175678607) ApiLevel of SdkSpecPrivate should be FutureApiLevel
+	SdkSpecPrivate = SdkSpec{SdkPrivate, NoneApiLevel, ""}
+	// TODO(b/175678607) ApiLevel of SdkSpecCorePlatform should be FutureApiLevel
+	SdkSpecCorePlatform = SdkSpec{SdkCorePlatform, NoneApiLevel, "core_platform"}
+)
+
+func SdkSpecFrom(ctx EarlyModuleContext, str string) SdkSpec {
 	switch str {
 	// special cases first
 	case "":
-		return SdkSpec{SdkPrivate, NoneApiLevel, str}
+		return SdkSpecPrivate
 	case "none":
-		return SdkSpec{SdkNone, NoneApiLevel, str}
+		return SdkSpecNone
 	case "core_platform":
-		return SdkSpec{SdkCorePlatform, NoneApiLevel, str}
+		return SdkSpecCorePlatform
 	default:
 		// the syntax is [kind_]version
 		sep := strings.LastIndex(str, "_")
@@ -242,15 +250,10 @@
 			return SdkSpec{SdkInvalid, NoneApiLevel, str}
 		}
 
-		var apiLevel ApiLevel
-		if versionString == "current" {
-			apiLevel = FutureApiLevel
-		} else if i, err := strconv.Atoi(versionString); err == nil {
-			apiLevel = uncheckedFinalApiLevel(i)
-		} else {
+		apiLevel, err := ApiLevelFromUser(ctx, versionString)
+		if err != nil {
 			return SdkSpec{SdkInvalid, apiLevel, str}
 		}
-
 		return SdkSpec{kind, apiLevel, str}
 	}
 }