2 files changed, 95 insertions, 0 deletions
diff --git a/internal/filter/filter.go b/internal/filter/filter.go
new file mode 100644
index 0000000..3fff07f
--- /dev/null
+++ b/internal/filter/filter.go
@@ -0,0 +1,49 @@
+package filter
+
+import (
+	"fmt"
+)
+
+type Filter struct {
+	name       string
+	action     func(string) string
+	subfilters []Filter
+}
+
+type Greeter interface {
+	Greet()
+}
+
+type Filterer interface {
+	Greeter
+	Filter(string) string
+}
+
+func (f Filter) Greet() {
+	subfilterCount := len(f.subfilters)
+
+	fmt.Printf("I am a filter and my name is %v\n", f.name)
+	if subfilterCount > 0 {
+		fmt.Println("My subfilters are:")
+
+		for _, subfilter := range f.subfilters {
+			fmt.Printf("- %v\n", subfilter.name)
+		}
+	}
+}
+
+func (f Filter) Filter(token string) (modifiedToken string) {
+	subfilterCount := len(f.subfilters)
+	modifiedToken = token
+
+	if subfilterCount > 0 {
+		for _, subfilter := range f.subfilters {
+			modifiedToken = subfilter.action(modifiedToken)
+		}
+
+		return modifiedToken
+	}
+
+	modifiedToken = f.action(token)
+	return modifiedToken
+}
diff --git a/internal/filter/filters.go b/internal/filter/filters.go
new file mode 100644
index 0000000..8532fef
--- /dev/null
+++ b/internal/filter/filters.go
@@ -0,0 +1,46 @@
+package filter
+
+import (
+	"strings"
+)
+
+var filterList = map[string]interface{}{
+	"uppercase":       NewUppercaseFilter,
+	"lowercase":       NewLowercaseFilter,
+	"lowercase_extra": NewLowercaseFilterWithExtraSteps,
+}
+
+func NewUppercaseFilter() Filter {
+	uppercaseFilter := Filter{
+		name:       "Uppercase",
+		action:     strings.ToUpper,
+		subfilters: []Filter{},
+	}
+
+	return uppercaseFilter
+}
+
+func NewLowercaseFilter() Filter {
+	lowercaseFilter := Filter{
+		name:       "Lowercase",
+		action:     strings.ToLower,
+		subfilters: []Filter{},
+	}
+
+	return lowercaseFilter
+}
+
+func NewLowercaseFilterWithExtraSteps() Filter {
+	var subfilters []Filter
+
+	subfilters = append(subfilters, NewUppercaseFilter())
+	subfilters = append(subfilters, NewLowercaseFilter())
+
+	filter := Filter{
+		name:       "Lowercase (extra dumb)",
+		action:     func(string) string { return "" },
+		subfilters: subfilters,
+	}
+
+	return filter
+}