Add task api and resource locking ability

task/resources.go

@@ -0,0 +1,93 @@
+package task
+
+import (
+	"strings"
+)
+
+// AllLocalReposResourcesKey to be used as resource key when all local repos are needed
+const AllLocalReposResourcesKey = "__alllocalrepos__"
+
+// ResourceConflictError represents a list tasks
+// using conflicitng resources
+type ResourceConflictError struct {
+	Tasks   []Task
+	Message string
+}
+
+func (e *ResourceConflictError) Error() string {
+	return e.Message
+}
+
+// ResourcesSet represents a set of task resources.
+// A resource is represented by its unique key
+type ResourcesSet struct {
+	set map[string]*Task
+}
+
+// NewResourcesSet creates new instance of resources set
+func NewResourcesSet() *ResourcesSet {
+	return &ResourcesSet{make(map[string]*Task)}
+}
+
+// MarkInUse given resources as used by given task
+func (r *ResourcesSet) MarkInUse(resources []string, task *Task) {
+	for _, resource := range resources {
+		r.set[resource] = task
+	}
+}
+
+// UsedBy checks whether one of given resources
+// is used by a task and if yes returns slice of such task
+func (r *ResourcesSet) UsedBy(resources []string) []Task {
+	var tasks []Task
+	var task *Task
+	var found bool
+
+	for _, resource := range resources {
+
+		if resource == AllLocalReposResourcesKey {
+			for taskResource, task := range r.set {
+				if strings.HasPrefix(taskResource, "L") {
+					tasks = appendTask(tasks, task)
+				}
+			}
+		}
+
+		task, found = r.set[resource]
+		if found {
+			tasks = appendTask(tasks, task)
+		}
+	}
+
+	task, found = r.set[AllLocalReposResourcesKey]
+	if found {
+		tasks = appendTask(tasks, task)
+	}
+
+	return tasks
+}
+
+// appendTask only appends task to tasks slice if not already
+// on slice
+func appendTask(tasks []Task, task *Task) []Task {
+	needsAppending := true
+	for _, givenTask := range tasks {
+		if givenTask.ID == task.ID {
+			needsAppending = false
+			break
+		}
+	}
+
+	if needsAppending {
+		return append(tasks, *task)
+	}
+
+	return tasks
+}
+
+// Free removes given resources from dependency set
+func (r *ResourcesSet) Free(resources []string) {
+	for _, resource := range resources {
+		delete(r.set, resource)
+	}
+}