feat: add cache manager

internal/cache/cache_manager.go

@@ -0,0 +1,43 @@
+package cache_manager
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+)
+
+type CacheManager struct {
+	Root string
+}
+
+// Creates a new cache manager rooted at <cacheRoot>.
+//
+// If <cacheRoot> does not exist, returns an error.
+func NewCacheManager(cacheRoot string) (*CacheManager, error) {
+	if _, err := os.Stat(cacheRoot); errors.Is(err, os.ErrNotExist) {
+		return nil, errors.New("Cache root must exist.")
+	}
+
+	return &CacheManager{
+		Root: cacheRoot,
+	}, nil
+}
+
+// Returns a path prefixed with the cache root.
+func (c CacheManager) Path(elems ...string) string {
+	return filepath.Join(c.Root, filepath.Join(elems...))
+}
+
+// Checks whether a specific top-level items exists in the cache.
+func (c CacheManager) Exists(key string) bool {
+    if _, err := os.Stat(c.Path(key)); errors.Is(err, os.ErrNotExist) {
+		return false
+	}
+
+    return true
+}
+
+// Deletes an element from the cache, if it exists.
+func (c CacheManager) Evict(key string) {
+    os.RemoveAll(c.Path(key))
+}

internal/cache/cache_manager_test.go

@@ -0,0 +1,44 @@
+package cache_manager
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestNewCacheManagerFailsIfNonExistentRoot(t *testing.T) {
+	nonPath := "/not/a/path"
+
+	mgr, err := NewCacheManager(nonPath)
+
+	if err == nil {
+		t.Error("Expected error, got nil.")
+	}
+
+	if mgr != nil {
+		t.Error("Expected nil manager, got non-nil.")
+	}
+}
+
+func TestNewCacheManagerReturnsCacheManagerPointer(t *testing.T) {
+	mgr, err := NewCacheManager(t.TempDir())
+
+	if err != nil {
+		t.Errorf("Expected nil error, got %s.", err)
+	}
+
+	if mgr == nil {
+		t.Error("Expected non-nil manager, got nil.")
+	}
+}
+
+func TestCacheManagerPathReturnsPathRootedAtCacheRoot(t *testing.T) {
+	tmpRoot := t.TempDir()
+	mgr, _ := NewCacheManager(tmpRoot)
+
+	rootedPath := mgr.Path("test")
+	expectedPath := filepath.Join(tmpRoot, "test")
+
+	if rootedPath != expectedPath {
+		t.Errorf("Expected %s, got %s.", expectedPath, rootedPath)
+	}
+}

internal/commands/execute_workflow.go

@@ -19,6 +19,7 @@ func ExecuteWorkflow(configuration Configuration, workflowFile string) error {
 	runnerInstance := runner.NewRunner(
 		driver,
 		configuration.Runner.Labels,
+		configuration.Cache.Dir,
 	)
 
 	workflow, err := workflow.FromYamlFile(workflowFile)

internal/runner/runner.go

@@ -2,6 +2,7 @@ package runner
 
 import (
 	"context"
+	cache "courgette/internal/cache"
 	driver "courgette/internal/driver"
 	logger "courgette/internal/logging"
 	workflow "courgette/internal/workflow"
@@ -13,14 +14,18 @@ import (
 type Runner struct {
 	Labels map[string]string
 	Driver driver.ContainerDriver
+	Cache  cache.CacheManager
 	Runs   int
 	// Deferred tasks, in order their were scheduled.
 	deferred *DeferredTaskManager
 }
 
-func NewRunner(driver driver.ContainerDriver, labels map[string]string) Runner {
+func NewRunner(driver driver.ContainerDriver, labels map[string]string, cacheRoot string) Runner {
+	cacheManager, _ := cache.NewCacheManager(cacheRoot)
+
 	return Runner{
 		Driver:   driver,
+		Cache:    *cacheManager,
 		Labels:   labels,
 		deferred: NewDeferredTaskManager(),
 	}

internal/runner/runner_flow_test.go

@@ -48,7 +48,7 @@ func TestRunJobInContainerSchedulesStoppingContainers(t *testing.T) {
 	mockDriver := driver.NewMockDriver()
 	mockDriver.WithMockedCall("Exec", driver.CommandResult{ExitCode: 1, Error: nil}, "test-container", "test-command", ".", fmt.Sprintf("%#v", map[string]string{}))
 
-	runner := NewRunner(&mockDriver, map[string]string{})
+	runner := NewRunner(&mockDriver, map[string]string{}, t.TempDir())
 
 	jobCtx := context.WithValue(context.Background(), "currentJob", workflow.Job{})
 	jobCtx = context.WithValue(jobCtx, "workflow", workflow.Workflow{})

internal/runner/runner_job_test.go

@@ -21,7 +21,7 @@ jobs:
 	workflow, _ := workflow.FromYamlBytes([]byte(workflowSample))
 	mockDriver := driver.NewMockDriver()
 
-	runner := NewRunner(&mockDriver, map[string]string{"test": "test"})
+	runner := NewRunner(&mockDriver, map[string]string{"test": "test"}, t.TempDir())
 
 	jobContext := context.WithValue(context.Background(), "workflow", *workflow)
 	jobContext = context.WithValue(jobContext, "currentJob", workflow.Jobs["jobA"])
@@ -46,7 +46,7 @@ jobs:
 	workflow, _ := workflow.FromYamlBytes([]byte(workflowSample))
 	mockDriver := driver.NewMockDriver()
 
-	runner := NewRunner(&mockDriver, map[string]string{"test": "test"})
+	runner := NewRunner(&mockDriver, map[string]string{"test": "test"}, t.TempDir())
 
 	jobContext := context.WithValue(context.Background(), "workflow", *workflow)
 	jobContext = context.WithValue(jobContext, "currentJob", workflow.Jobs["jobA"])
@@ -73,7 +73,7 @@ jobs:
 	mockDriver := driver.NewMockDriver()
 
 	mockDriver.WithMockedCall("Exec", driver.CommandResult{Error: errors.New("exit 1!"), ExitCode: 1}, "testContainer", "exit 1", fmt.Sprintf("%#v", map[string]string{}))
-	runner := NewRunner(&mockDriver, map[string]string{"test": "test"})
+	runner := NewRunner(&mockDriver, map[string]string{"test": "test"}, t.TempDir())
 
 	jobContext := context.WithValue(context.Background(), "workflow", *workflow)
 	jobContext = context.WithValue(jobContext, "currentJob", workflow.Jobs["jobA"])
@@ -101,7 +101,7 @@ jobs:
 	mockDriver := driver.NewMockDriver()
 
 	mockDriver.WithMockedCall("Exec", driver.CommandResult{Error: errors.New("exit 1!"), ExitCode: 1}, "testContainer", "exit 1", fmt.Sprintf("%#v", map[string]string{}))
-	runner := NewRunner(&mockDriver, map[string]string{"test": "test"})
+	runner := NewRunner(&mockDriver, map[string]string{"test": "test"}, t.TempDir())
 
 	jobContext := context.WithValue(context.Background(), "workflow", *workflow)
 	jobContext = context.WithValue(jobContext, "currentJob", workflow.Jobs["jobA"])
@@ -133,7 +133,7 @@ jobs:
 	mockDriver := driver.NewMockDriver()
 
 	mockDriver.WithMockedCall("Exec", driver.CommandResult{Error: errors.New("exit 1!"), ExitCode: 1}, "testContainer", "exit 1", ".", fmt.Sprintf("%#v", map[string]string{}))
-	runner := NewRunner(&mockDriver, map[string]string{"test": "test"})
+	runner := NewRunner(&mockDriver, map[string]string{"test": "test"}, t.TempDir())
 
 	jobContext := context.WithValue(context.Background(), "workflow", *workflow)
 	jobContext = context.WithValue(jobContext, "currentJob", workflow.Jobs["jobA"])
@@ -164,7 +164,7 @@ jobs:
 	mockDriver := driver.NewMockDriver()
 
 	mockDriver.WithMockedCall("Exec", driver.CommandResult{Error: errors.New("exit 1!"), ExitCode: 1}, "testContainer", "exit 1", ".", fmt.Sprintf("%#v", map[string]string{}))
-	runner := NewRunner(&mockDriver, map[string]string{"test": "test"})
+	runner := NewRunner(&mockDriver, map[string]string{"test": "test"}, t.TempDir())
 
 	jobContext := context.WithValue(context.Background(), "workflow", *workflow)
 	jobContext = context.WithValue(jobContext, "currentJob", workflow.Jobs["jobA"])