Add support for dropwizard input format (#2846)

internal/templating/node.go

@@ -0,0 +1,122 @@
+package templating
+
+import (
+	"sort"
+	"strings"
+)
+
+// node is an item in a sorted k-ary tree of filter parts. Each child is sorted by its part value.
+// The special value of "*", is always sorted last.
+type node struct {
+	separator string
+	value     string
+	children  nodes
+	template  *Template
+}
+
+// insert inserts the given string template into the tree.  The filter string is separated
+// on the template separator and each part is used as the path in the tree.
+func (n *node) insert(filter string, template *Template) {
+	n.separator = template.separator
+	n.recursiveInsert(strings.Split(filter, n.separator), template)
+}
+
+// recursiveInsert does the actual recursive insertion
+func (n *node) recursiveInsert(values []string, template *Template) {
+	// Add the end, set the template
+	if len(values) == 0 {
+		n.template = template
+		return
+	}
+
+	// See if the the current element already exists in the tree. If so, insert the
+	// into that sub-tree
+	for _, v := range n.children {
+		if v.value == values[0] {
+			v.recursiveInsert(values[1:], template)
+			return
+		}
+	}
+
+	// New element, add it to the tree and sort the children
+	newNode := &node{value: values[0]}
+	n.children = append(n.children, newNode)
+	sort.Sort(&n.children)
+
+	// Now insert the rest of the tree into the new element
+	newNode.recursiveInsert(values[1:], template)
+}
+
+// search searches for a template matching the input string
+func (n *node) search(line string) *Template {
+	separator := n.separator
+	return n.recursiveSearch(strings.Split(line, separator))
+}
+
+// recursiveSearch performs the actual recursive search
+func (n *node) recursiveSearch(lineParts []string) *Template {
+	// Nothing to search
+	if len(lineParts) == 0 || len(n.children) == 0 {
+		return n.template
+	}
+
+	// If last element is a wildcard, don't include it in this search since it's sorted
+	// to the end but lexicographically it would not always be and sort.Search assumes
+	// the slice is sorted.
+	length := len(n.children)
+	if n.children[length-1].value == "*" {
+		length--
+	}
+
+	// Find the index of child with an exact match
+	i := sort.Search(length, func(i int) bool {
+		return n.children[i].value >= lineParts[0]
+	})
+
+	// Found an exact match, so search that child sub-tree
+	if i < len(n.children) && n.children[i].value == lineParts[0] {
+		return n.children[i].recursiveSearch(lineParts[1:])
+	}
+	// Not an exact match, see if we have a wildcard child to search
+	if n.children[len(n.children)-1].value == "*" {
+		return n.children[len(n.children)-1].recursiveSearch(lineParts[1:])
+	}
+	return n.template
+}
+
+// nodes is simply an array of nodes implementing the sorting interface.
+type nodes []*node
+
+// Less returns a boolean indicating whether the filter at position j
+// is less than the filter at position k. Filters are order by string
+// comparison of each component parts.  A wildcard value "*" is never
+// less than a non-wildcard value.
+//
+// For example, the filters:
+//             "*.*"
+//             "servers.*"
+//             "servers.localhost"
+//             "*.localhost"
+//
+// Would be sorted as:
+//             "servers.localhost"
+//             "servers.*"
+//             "*.localhost"
+//             "*.*"
+func (n *nodes) Less(j, k int) bool {
+	if (*n)[j].value == "*" && (*n)[k].value != "*" {
+		return false
+	}
+
+	if (*n)[j].value != "*" && (*n)[k].value == "*" {
+		return true
+	}
+
+	return (*n)[j].value < (*n)[k].value
+}
+
+// Swap swaps two elements of the array
+func (n *nodes) Swap(i, j int) { (*n)[i], (*n)[j] = (*n)[j], (*n)[i] }
+
+// Len returns the length of the array
+func (n *nodes) Len() int { return len(*n) }