runtime: new execution engine

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

plan/task/task.go

@@ -0,0 +1,68 @@
+package task
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+
+	"cuelang.org/go/cue"
+	"go.dagger.io/dagger/compiler"
+	"go.dagger.io/dagger/environment"
+	"go.dagger.io/dagger/plancontext"
+	"go.dagger.io/dagger/solver"
+)
+
+var (
+	ErrNotTask = errors.New("not a task")
+	tasks      sync.Map
+	typePath   = cue.MakePath(cue.Hid("_type", "alpha.dagger.io/dagger"))
+)
+
+type NewFunc func() Task
+
+type Task interface {
+	Run(ctx context.Context, pctx *plancontext.Context, s solver.Solver, v *compiler.Value) (*compiler.Value, error)
+}
+
+// Register a task type and initializer
+func Register(typ string, f NewFunc) {
+	tasks.Store(typ, f)
+}
+
+// New creates a new Task of the given type.
+func New(typ string) Task {
+	v, ok := tasks.Load(typ)
+	if !ok {
+		return nil
+	}
+	fn := v.(NewFunc)
+	return fn()
+}
+
+func Lookup(v *compiler.Value) (Task, error) {
+	// FIXME: legacy pipelines
+	if environment.IsComponent(v) {
+		return New("#up"), nil
+	}
+
+	if v.Kind() != cue.StructKind {
+		return nil, ErrNotTask
+	}
+
+	typ := v.LookupPath(typePath)
+	if !typ.Exists() {
+		return nil, ErrNotTask
+	}
+
+	typeString, err := typ.String()
+	if err != nil {
+		return nil, err
+	}
+
+	t := New(typeString)
+	if t == nil {
+		return nil, fmt.Errorf("unknown type %q", typeString)
+	}
+	return t, nil
+}