func buildAAR()

in cmd/gomobile/bind_androidapp.go [136:269]
122 lines of code
30 McCabe index (conditional complexity)

func buildAAR(srcDir, androidDir string, pkgs []*packages.Package, targets []targetInfo) (err error) {
	var out io.Writer = ioutil.Discard
	if buildO == "" {
		buildO = pkgs[0].Name + ".aar"
	}
	if !strings.HasSuffix(buildO, ".aar") {
		return fmt.Errorf("output file name %q does not end in '.aar'", buildO)
	}
	if !buildN {
		f, err := os.Create(buildO)
		if err != nil {
			return err
		}
		defer func() {
			if cerr := f.Close(); err == nil {
				err = cerr
			}
		}()
		out = f
	}

	aarw := zip.NewWriter(out)
	aarwcreate := func(name string) (io.Writer, error) {
		if buildV {
			fmt.Fprintf(os.Stderr, "aar: %s\n", name)
		}
		return aarw.Create(name)
	}
	w, err := aarwcreate("AndroidManifest.xml")
	if err != nil {
		return err
	}
	const manifestFmt = `<manifest xmlns:android="http://schemas.android.com/apk/res/android" package=%q>
<uses-sdk android:minSdkVersion="%d"/></manifest>`
	fmt.Fprintf(w, manifestFmt, "go."+pkgs[0].Name+".gojni", buildAndroidAPI)

	w, err = aarwcreate("proguard.txt")
	if err != nil {
		return err
	}
	fmt.Fprintln(w, `-keep class go.** { *; }`)
	if bindJavaPkg != "" {
		fmt.Fprintln(w, `-keep class `+bindJavaPkg+`.** { *; }`)
	} else {
		for _, p := range pkgs {
			fmt.Fprintln(w, `-keep class `+p.Name+`.** { *; }`)
		}
	}

	w, err = aarwcreate("classes.jar")
	if err != nil {
		return err
	}
	if err := buildJar(w, srcDir); err != nil {
		return err
	}

	files := map[string]string{}
	for _, pkg := range pkgs {
		// TODO(hajimehoshi): This works only with Go tools that assume all source files are in one directory.
		// Fix this to work with other Go tools.
		assetsDir := filepath.Join(filepath.Dir(pkg.GoFiles[0]), "assets")
		assetsDirExists := false
		if fi, err := os.Stat(assetsDir); err == nil {
			assetsDirExists = fi.IsDir()
		} else if !os.IsNotExist(err) {
			return err
		}

		if assetsDirExists {
			err := filepath.Walk(
				assetsDir, func(path string, info os.FileInfo, err error) error {
					if err != nil {
						return err
					}
					if info.IsDir() {
						return nil
					}
					f, err := os.Open(path)
					if err != nil {
						return err
					}
					defer f.Close()
					name := "assets/" + path[len(assetsDir)+1:]
					if orig, exists := files[name]; exists {
						return fmt.Errorf("package %s asset name conflict: %s already added from package %s",
							pkg.PkgPath, name, orig)
					}
					files[name] = pkg.PkgPath
					w, err := aarwcreate(name)
					if err != nil {
						return nil
					}
					_, err = io.Copy(w, f)
					return err
				})
			if err != nil {
				return err
			}
		}
	}

	for _, t := range targets {
		toolchain := ndk.Toolchain(t.arch)
		lib := toolchain.abi + "/libgojni.so"
		w, err = aarwcreate("jni/" + lib)
		if err != nil {
			return err
		}
		if !buildN {
			r, err := os.Open(filepath.Join(androidDir, "src/main/jniLibs/"+lib))
			if err != nil {
				return err
			}
			defer r.Close()
			if _, err := io.Copy(w, r); err != nil {
				return err
			}
		}
	}

	// TODO(hyangah): do we need to use aapt to create R.txt?
	w, err = aarwcreate("R.txt")
	if err != nil {
		return err
	}

	w, err = aarwcreate("res/")
	if err != nil {
		return err
	}

	return aarw.Close()
}