1 files changed, 78 insertions, 0 deletions
diff --git a/main/pathfilter.go b/main/pathfilter.go
new file mode 100644
index 0000000..7b6c64f
--- /dev/null
+++ b/main/pathfilter.go
@@ -0,0 +1,78 @@
+package main
+
+type MapTerminalFilter struct {}
+func (filter MapTerminalFilter) exec(state *ProgramState) bool {
+	terminal, isTerminal := state.space.value.(TerminalValue)
+	if !isTerminal {
+		return false
+	}
+	return terminal == MapBegin || terminal == MapEnd
+}
+
+type NonTerminalFilter struct {}
+func (filter NonTerminalFilter) exec(state *ProgramState) bool {
+	_, isTerminal := state.space.value.(TerminalValue)
+	return !isTerminal
+}
+
+type AnySegmentPathFilter struct {
+	next PathFilterState
+}
+func (filter AnySegmentPathFilter) eat(segment PathSegment) map[PathFilterState]struct{} {
+	res := make(map[PathFilterState]struct{})
+	res[filter.next] = struct{}{}
+	return res
+}
+func (filter AnySegmentPathFilter) accept() bool {
+	return false
+}
+
+type GroupPathFilter struct {
+	filters []PathFilterState
+}
+func (filter GroupPathFilter) eat(segment PathSegment) map[PathFilterState]struct{} {
+	res := make(map[PathFilterState]struct{})
+	for _, f := range filter.filters {
+		for r := range f.eat(segment) {
+			res[r] = struct{}{}
+		}
+	}
+	return res
+}
+func (filter GroupPathFilter) accept() bool {
+	for _, f := range filter.filters {
+		if f.accept() {
+			return true
+		}
+	}
+	return false
+}
+
+type NonePathFilter struct {}
+func (filter NonePathFilter) eat(segment PathSegment) map[PathFilterState]struct{} {
+	return make(map[PathFilterState]struct{})
+}
+func (filter NonePathFilter) accept() bool {
+	return true
+}
+
+type StringSegmentPathFilter struct {
+	index string
+	next PathFilterState
+}
+func (filter StringSegmentPathFilter) eat(segment PathSegment) map[PathFilterState]struct{} {
+	s, isString := segment.(string)
+	res := make(map[PathFilterState]struct{})
+	if isString && s == filter.index {
+		res[filter.next] = struct{}{}
+	}
+	return res
+}
+func (filter StringSegmentPathFilter) accept() bool {
+	return false
+}
+
+type PathFilterState interface {
+	eat(PathSegment) map[PathFilterState]struct{}
+	accept() bool
+}