TaskRegistry implementation

Implemented the `pkg/api/snowblock.TaskRegistry` interface to register
future implementations of the `pkg/api/snowblock.TaskRunner` interface.
The validation logic of the `Add` function filters and denies task
runners that might try to register a duplicate task name.

Epic GH-33
Resolves GH-71

pkg/config/config.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/arcticicestudio/snowsaw/pkg/config/encoder"
 	"github.com/arcticicestudio/snowsaw/pkg/config/source/file"
+	"github.com/arcticicestudio/snowsaw/pkg/prt"
 )
 
 // Config represents the application-wide configurations.
@@ -43,6 +44,10 @@ type Snowblocks struct {
 
 func init() {
 	AppConfigPaths = genConfigPaths()
+	if err := registerSnowblockTaskRunner(); err != nil {
+		prt.Fatalf("Failed to register snowblock task runner: %v", err)
+		panic(err)
+	}
 }
 
 func genConfigPaths() []*file.File {
@@ -62,3 +67,13 @@ func genConfigPaths() []*file.File {
 
 	return files
 }
+
+func registerSnowblockTaskRunner() error {
+	for _, runner := range availableTaskRunner {
+		if err := SnowblockTaskRunnerRegistry.Add(runner); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

pkg/config/constants.go

@@ -12,7 +12,9 @@
 package config
 
 import (
+	"github.com/arcticicestudio/snowsaw/pkg/api/snowblock"
 	"github.com/arcticicestudio/snowsaw/pkg/config/source/file"
+	"github.com/arcticicestudio/snowsaw/pkg/snowblock/task"
 )
 
 const (
@@ -36,9 +38,14 @@ var (
 	// AppConfigPaths is the default paths the application will search for configuration files.
 	AppConfigPaths []*file.File
 
+	availableTaskRunner []snowblock.TaskRunner
+
 	// BuildDateTime is the date and time this application was build.
 	BuildDateTime string
 
+	// SnowblockTaskRunnerRegistry is the application-wide registry for snowblock task runner.
+	SnowblockTaskRunnerRegistry = task.NewRegistry()
+
 	// Version is the application version.
 	Version = "0.0.0"
 )

pkg/snowblock/task/doc.go

@@ -0,0 +1,13 @@
+// Copyright (C) 2017-present Arctic Ice Studio <development@arcticicestudio.com>
+// Copyright (C) 2017-present Sven Greb <development@svengreb.de>
+//
+// Project:    snowsaw
+// Repository: https://github.com/arcticicestudio/snowsaw
+// License:    MIT
+
+// Author: Arctic Ice Studio <development@arcticicestudio.com>
+// Author: Sven Greb <development@svengreb.de>
+// Since: 0.4.0
+
+// Package task provides task configuration and runner implementations of the snowblock API.
+package task

pkg/snowblock/task/registry.go

@@ -0,0 +1,46 @@
+// Copyright (C) 2017-present Arctic Ice Studio <development@arcticicestudio.com>
+// Copyright (C) 2017-present Sven Greb <development@svengreb.de>
+//
+// Project:    snowsaw
+// Repository: https://github.com/arcticicestudio/snowsaw
+// License:    MIT
+
+// Author: Arctic Ice Studio <development@arcticicestudio.com>
+// Author: Sven Greb <development@svengreb.de>
+// Since: 0.4.0
+
+package task
+
+import (
+	"fmt"
+
+	"github.com/fatih/color"
+
+	"github.com/arcticicestudio/snowsaw/pkg/api/snowblock"
+)
+
+// Registry is a registry for available task runner.
+type Registry struct {
+	runner map[string]snowblock.TaskRunner
+}
+
+// NewRegistry returns a new task runner registry instance.
+func NewRegistry() *Registry {
+	return &Registry{runner: make(map[string]snowblock.TaskRunner)}
+}
+
+// Add validates and adds the given task runner to the registry.
+// If the name of the given task runner has already been registered and error is returned.
+func (reg *Registry) Add(r snowblock.TaskRunner) error {
+	_, exists := reg.runner[r.GetTaskName()]
+	if exists {
+		return fmt.Errorf("runner for task name already exists: %s", color.CyanString(r.GetTaskName()))
+	}
+	reg.runner[r.GetTaskName()] = r
+	return nil
+}
+
+// GetAll returns a list of all currently registered task runner.
+func (reg *Registry) GetAll() map[string]snowblock.TaskRunner {
+	return reg.runner
+}