New static configuration loading system.

Co-authored-by: Mathieu Lonjaret <mathieu.lonjaret@gmail.com>

pkg/config/parser/labels_decode.go

@@ -0,0 +1,95 @@
+package parser
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+const labelRoot = "traefik"
+
+// DecodeToNode converts the labels to a tree of nodes.
+// If any filters are present, labels which do not match the filters are skipped.
+func DecodeToNode(labels map[string]string, filters ...string) (*Node, error) {
+	sortedKeys := sortKeys(labels, filters)
+
+	var node *Node
+	for i, key := range sortedKeys {
+		split := strings.Split(key, ".")
+
+		if split[0] != labelRoot {
+			return nil, fmt.Errorf("invalid label root %s", split[0])
+		}
+
+		var parts []string
+		for _, v := range split {
+			if v[0] == '[' {
+				return nil, fmt.Errorf("invalid leading character '[' in field name (bracket is a slice delimiter): %s", v)
+			}
+
+			if strings.HasSuffix(v, "]") && v[0] != '[' {
+				indexLeft := strings.Index(v, "[")
+				parts = append(parts, v[:indexLeft], v[indexLeft:])
+			} else {
+				parts = append(parts, v)
+			}
+		}
+
+		if i == 0 {
+			node = &Node{}
+		}
+		decodeToNode(node, parts, labels[key])
+	}
+
+	return node, nil
+}
+
+func decodeToNode(root *Node, path []string, value string) {
+	if len(root.Name) == 0 {
+		root.Name = path[0]
+	}
+
+	// it's a leaf or not -> children
+	if len(path) > 1 {
+		if n := containsNode(root.Children, path[1]); n != nil {
+			// the child already exists
+			decodeToNode(n, path[1:], value)
+		} else {
+			// new child
+			child := &Node{Name: path[1]}
+			decodeToNode(child, path[1:], value)
+			root.Children = append(root.Children, child)
+		}
+	} else {
+		root.Value = value
+	}
+}
+
+func containsNode(nodes []*Node, name string) *Node {
+	for _, n := range nodes {
+		if name == n.Name {
+			return n
+		}
+	}
+	return nil
+}
+
+func sortKeys(labels map[string]string, filters []string) []string {
+	var sortedKeys []string
+	for key := range labels {
+		if len(filters) == 0 {
+			sortedKeys = append(sortedKeys, key)
+			continue
+		}
+
+		for _, filter := range filters {
+			if len(key) >= len(filter) && strings.EqualFold(key[:len(filter)], filter) {
+				sortedKeys = append(sortedKeys, key)
+				continue
+			}
+		}
+	}
+	sort.Strings(sortedKeys)
+
+	return sortedKeys
+}