feat(wait): strategy walk

docs/features/wait/walk.md

@@ -0,0 +1,12 @@
+# Walk
+
+Walk walks the strategies tree and calls the visit function for each node.
+
+If visit function returns `wait.VisitStop`, the walk stops.
+If visit function returns `wait.VisitRemove`, the current node is removed.
+
+## Walk removing entries
+
+<!--codeinclude-->
+[Walk a strategy and remove the all FileStrategy entries found](../../../wait/walk_test.go) inside_block:walkRemoveFileStrategy
+<!--/codeinclude-->

wait/walk.go

@@ -0,0 +1,74 @@
+package wait
+
+import (
+	"errors"
+)
+
+var (
+	// VisitStop is used as a return value from [VisitFunc] to stop the walk.
+	// It is not returned as an error by any function.
+	VisitStop = errors.New("stop the walk")
+
+	// VisitRemove is used as a return value from [VisitFunc] to have the current node removed.
+	// It is not returned as an error by any function.
+	VisitRemove = errors.New("remove this strategy")
+)
+
+// VisitFunc is a function that visits a strategy node.
+// If it returns [VisitStop], the walk stops.
+// If it returns [VisitRemove], the current node is removed.
+type VisitFunc func(root Strategy) error
+
+// Walk walks the strategies tree and calls the visit function for each node.
+func Walk(root *Strategy, visit VisitFunc) error {
+	if root == nil {
+		return errors.New("root strategy is nil")
+	}
+
+	if err := walk(root, visit); err != nil {
+		if errors.Is(err, VisitRemove) || errors.Is(err, VisitStop) {
+			return nil
+		}
+		return err
+	}
+
+	return nil
+}
+
+// walk walks the strategies tree and calls the visit function for each node.
+// It returns an error if the visit function returns an error.
+func walk(root *Strategy, visit VisitFunc) error {
+	if *root == nil {
+		// No strategy.
+		return nil
+	}
+
+	// Allow the visit function to customize the behaviour of the walk before visiting the children.
+	if err := visit(*root); err != nil {
+		if errors.Is(err, VisitRemove) {
+			*root = nil
+		}
+
+		return err
+	}
+
+	if s, ok := (*root).(*MultiStrategy); ok {
+		var i int
+		for range s.Strategies {
+			if err := walk(&s.Strategies[i], visit); err != nil {
+				if errors.Is(err, VisitRemove) {
+					s.Strategies = append(s.Strategies[:i], s.Strategies[i+1:]...)
+					if errors.Is(err, VisitStop) {
+						return VisitStop
+					}
+					continue
+				}
+
+				return err
+			}
+			i++
+		}
+	}
+
+	return nil
+}

wait/walk_test.go

@@ -0,0 +1,127 @@
+package wait_test
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/testcontainers/testcontainers-go"
+	"github.com/testcontainers/testcontainers-go/wait"
+)
+
+func TestWalk(t *testing.T) {
+	req := testcontainers.ContainerRequest{
+		WaitingFor: wait.ForAll(
+			wait.ForFile("/tmp/file"),
+			wait.ForHTTP("/health"),
+			wait.ForAll(
+				wait.ForFile("/tmp/other"),
+			),
+		),
+	}
+
+	t.Run("walk", func(t *testing.T) {
+		var count int
+		err := wait.Walk(&req.WaitingFor, func(_ wait.Strategy) error {
+			count++
+			return nil
+		})
+		require.NoError(t, err)
+		require.Equal(t, 5, count)
+	})
+
+	t.Run("stop", func(t *testing.T) {
+		var count int
+		err := wait.Walk(&req.WaitingFor, func(_ wait.Strategy) error {
+			count++
+			return wait.VisitStop
+		})
+		require.NoError(t, err)
+		require.Equal(t, 1, count)
+	})
+
+	t.Run("remove", func(t *testing.T) {
+		// walkRemoveFileStrategy {
+		var count, matched int
+		err := wait.Walk(&req.WaitingFor, func(s wait.Strategy) error {
+			count++
+			if _, ok := s.(*wait.FileStrategy); ok {
+				matched++
+				return wait.VisitRemove
+			}
+
+			return nil
+		})
+		// }
+		require.NoError(t, err)
+		require.Equal(t, 5, count)
+		require.Equal(t, 2, matched)
+
+		count = 0
+		matched = 0
+		err = wait.Walk(&req.WaitingFor, func(s wait.Strategy) error {
+			count++
+			if _, ok := s.(*wait.FileStrategy); ok {
+				matched++
+			}
+			return nil
+		})
+		require.NoError(t, err)
+		require.Equal(t, 3, count)
+		require.Zero(t, matched)
+	})
+
+	t.Run("remove-stop", func(t *testing.T) {
+		req := testcontainers.ContainerRequest{
+			WaitingFor: wait.ForAll(
+				wait.ForFile("/tmp/file"),
+				wait.ForHTTP("/health"),
+			),
+		}
+		var count int
+		err := wait.Walk(&req.WaitingFor, func(_ wait.Strategy) error {
+			count++
+			return errors.Join(wait.VisitRemove, wait.VisitStop)
+		})
+		require.NoError(t, err)
+		require.Equal(t, 1, count)
+		require.Nil(t, req.WaitingFor)
+	})
+
+	t.Run("nil-root", func(t *testing.T) {
+		err := wait.Walk(nil, func(_ wait.Strategy) error {
+			return nil
+		})
+		require.EqualError(t, err, "root strategy is nil")
+	})
+
+	t.Run("direct-single", func(t *testing.T) {
+		req := testcontainers.ContainerRequest{
+			WaitingFor: wait.ForFile("/tmp/file"),
+		}
+		requireVisits(t, req, 1)
+	})
+
+	t.Run("for-all-single", func(t *testing.T) {
+		req := testcontainers.ContainerRequest{
+			WaitingFor: wait.ForAll(
+				wait.ForFile("/tmp/file"),
+			),
+		}
+		requireVisits(t, req, 2)
+	})
+}
+
+// requireVisits validates the number of visits for a given request.
+func requireVisits(t *testing.T, req testcontainers.ContainerRequest, expected int) {
+	t.Helper()
+
+	var count int
+	err := wait.Walk(&req.WaitingFor, func(_ wait.Strategy) error {
+		count++
+		return nil
+	})
+	require.NoError(t, err)
+	require.Equal(t, expected, count)
+}