[#149] Use chi instead of gorilla mux

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/router_filter.go

@@ -0,0 +1,133 @@
+package api
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type HandlerFilters struct {
+	filters        []Filter
+	defaultHandler http.Handler
+}
+
+type Filter struct {
+	queries []Pair
+	headers []Pair
+	h       http.Handler
+}
+
+type Pair struct {
+	Key   string
+	Value string
+}
+
+func NewHandlerFilter() *HandlerFilters {
+	return &HandlerFilters{}
+}
+
+func NewFilter() *Filter {
+	return &Filter{}
+}
+
+func (hf *HandlerFilters) Add(filter *Filter) *HandlerFilters {
+	hf.filters = append(hf.filters, *filter)
+	return hf
+}
+
+// HeadersMatch adds a matcher for header values.
+// It accepts a sequence of key/value pairs. Values may define variables.
+// Panics if number of parameters is not even.
+// Supports only exact matching.
+// If the value is an empty string, it will match any value if the key is set.
+func (f *Filter) HeadersMatch(pairs ...string) *Filter {
+	length := len(pairs)
+	if length%2 != 0 {
+		panic(fmt.Errorf("filter headers: number of parameters must be multiple of 2, got %v", pairs))
+	}
+
+	for i := 0; i < length; i += 2 {
+		f.headers = append(f.headers, Pair{
+			Key:   pairs[i],
+			Value: pairs[i+1],
+		})
+	}
+
+	return f
+}
+
+// Headers is similar to HeadersMatch but accept only header keys, set value to empty string internally.
+func (f *Filter) Headers(headers ...string) *Filter {
+	for _, header := range headers {
+		f.headers = append(f.headers, Pair{
+			Key:   header,
+			Value: "",
+		})
+	}
+
+	return f
+}
+
+func (f *Filter) Handler(handler http.HandlerFunc) *Filter {
+	f.h = handler
+	return f
+}
+
+// QueriesMatch adds a matcher for URL query values.
+// It accepts a sequence of key/value pairs. Values may define variables.
+// Panics if number of parameters is not even.
+// Supports only exact matching.
+// If the value is an empty string, it will match any value if the key is set.
+func (f *Filter) QueriesMatch(pairs ...string) *Filter {
+	length := len(pairs)
+	if length%2 != 0 {
+		panic(fmt.Errorf("filter headers: number of parameters must be multiple of 2, got %v", pairs))
+	}
+
+	for i := 0; i < length; i += 2 {
+		f.queries = append(f.queries, Pair{
+			Key:   pairs[i],
+			Value: pairs[i+1],
+		})
+	}
+
+	return f
+}
+
+// Queries is similar to QueriesMatch but accept only query keys, set value to empty string internally.
+func (f *Filter) Queries(queries ...string) *Filter {
+	for _, query := range queries {
+		f.queries = append(f.queries, Pair{
+			Key:   query,
+			Value: "",
+		})
+	}
+
+	return f
+}
+
+func (hf *HandlerFilters) DefaultHandler(handler http.HandlerFunc) *HandlerFilters {
+	hf.defaultHandler = handler
+	return hf
+}
+
+func (hf *HandlerFilters) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+LOOP:
+	for _, filter := range hf.filters {
+		for _, header := range filter.headers {
+			hdrVals := r.Header.Values(header.Key)
+			if len(hdrVals) == 0 || header.Value != "" && header.Value != hdrVals[0] {
+				continue LOOP
+			}
+		}
+		for _, query := range filter.queries {
+			queryVal := r.URL.Query().Get(query.Key)
+			if !r.URL.Query().Has(query.Key) || queryVal != "" && query.Value != queryVal {
+				continue LOOP
+			}
+		}
+		filter.h.ServeHTTP(w, r)
+		return
+	}
+
+	hf.defaultHandler.ServeHTTP(w, r)
+}