Starting to implement install() by plopping the gem into the cache/ directory

build.gradle

@@ -29,6 +29,8 @@ dependencies {
     codenarc "org.codenarc:CodeNarc:0.24"
 
     testCompile "org.spockframework:spock-core:1.0-groovy-2.4"
+    /* used for cleaning up directories in tests */
+    testCompile 'org.apache.commons:commons-io:1.3.2+'
 }
 
 codenarc {

src/main/groovy/com/github/jrubygradle/groovygem/GemInstaller.groovy

@@ -7,6 +7,12 @@ import groovy.transform.CompileStatic
  */
 @CompileStatic
 class GemInstaller {
+    static enum DuplicateBehavior {
+        OVERWRITE,
+        SKIP,
+        FAIL
+    }
+
     protected File installDirectory
     protected List<File> gems
 

src/main/groovy/com/github/jrubygradle/groovygem/internal/GemInstaller.groovy

@@ -9,6 +9,10 @@ import org.slf4j.LoggerFactory
 
 import groovy.transform.CompileStatic
 
+import com.github.jrubygradle.groovygem.GemInstaller.DuplicateBehavior
+
+import java.nio.file.Files
+
 @CompileStatic
 class GemInstaller {
     static final List<String> GEM_HOME_DIRS = ['bin', 'build_info', 'cache', 'doc',
@@ -25,6 +29,27 @@ class GemInstaller {
         this.fileSystemManager = VFS.manager
     }
 
+    /** Install and overwrite anything that stands in the way */
+    void install() {
+        install(DuplicateBehavior.OVERWRITE)
+    }
+
+    void install(DuplicateBehavior onDuplicateBehavior) {
+        if (!mkdirs()) {
+            /* raise some exception? */
+        }
+
+        gems.each { File gem ->
+            installGem(installDirectory, gem, onDuplicateBehavior)
+        }
+    }
+
+    boolean installGem(File installDir, File gem, DuplicateBehavior onDuplicate) {
+        cacheGemInInstallDir(installDir, gem)
+
+        return true
+    }
+
     /**
      * Create the requisite directories to map a GEM_HOME structure, namely:
      *   bin/
@@ -80,4 +105,10 @@ class GemInstaller {
             return false
         }
     }
+
+    /** Cache the gem in GEM_HOME/cache */
+    protected void cacheGemInInstallDir(File installDir, File gem) {
+        File cacheDir = new File(installDir, 'cache')
+        Files.copy(gem.toPath(), (new File(cacheDir, gem.name)).toPath())
+    }
 }

src/test/groovy/com/github/jrubygradle/groovygem/internal/GemInstallerSpec.groovy

@@ -4,10 +4,12 @@ import spock.lang.*
 
 import java.nio.file.Files
 import java.nio.file.Path
+import org.apache.commons.io.FileUtils
 
 class GemInstallerSpec extends Specification {
-    final String FIXTURES_ROOT = new File(['src', 'test', 'resources'].join(File.separator)).absolutePath
-    final String GEM_FIXTURE = [FIXTURES_ROOT, 'thor-0.19.1.gem'].join(File.separator)
+    static final String FIXTURES_ROOT = new File(['src', 'test', 'resources'].join(File.separator)).absolutePath
+    static final String GEM_FILENAME = 'thor-0.19.1.gem'
+    static final String GEM_FIXTURE = [FIXTURES_ROOT, GEM_FILENAME].join(File.separator)
 
     GemInstaller installer
     Path installDirPath = Files.createTempDirectory("geminstallerspec")
@@ -67,3 +69,30 @@ class GemInstallerSpec extends Specification {
         installer.isValidGem(gem)
     }
 }
+
+class GemInstallerIntegrationSpec extends Specification {
+    GemInstaller installer
+
+    Path installDirPath = Files.createTempDirectory("geminstallerintegrationspec")
+    String installDir = installDirPath as String
+
+    def setup() {
+        installer = new GemInstaller(installDir, [new File(GemInstallerSpec.GEM_FIXTURE)])
+    }
+
+    def cleanup() {
+        File dir = new File(installDir)
+
+        if (dir.exists() && dir.absolutePath.startsWith('/tmp')) {
+            FileUtils.deleteDirectory(dir)
+        }
+    }
+
+    def "install() should actually install my gem in the happy path"() {
+        when:
+        installer.install()
+
+        then:
+        (new File(installDir, ['cache', GemInstallerSpec.GEM_FILENAME].join(File.separator))).exists()
+    }
+}