Add scaffolding for scope package

pkg/scope/scope.go

@@ -0,0 +1,96 @@
+package scope
+
+import (
+	"net/http"
+	"regexp"
+	"sync"
+)
+
+type Scope struct {
+	mu    sync.Mutex
+	rules []Rule
+}
+
+type Rule struct {
+	URL    *regexp.Regexp
+	Header Header
+	Body   *regexp.Regexp
+}
+
+type Header struct {
+	Key   *regexp.Regexp
+	Value *regexp.Regexp
+}
+
+func New(rules []Rule) *Scope {
+	s := &Scope{}
+	if rules != nil {
+		s.rules = rules
+	}
+	return s
+}
+
+func (s *Scope) Rules() []Rule {
+	return s.rules
+}
+
+func (s *Scope) SetRules(rules []Rule) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.rules = rules
+}
+
+func (s *Scope) Match(req *http.Request, body []byte) bool {
+	// TODO(?): Do we need to lock here as well?
+	for _, rule := range s.rules {
+		if matches := rule.Match(req, body); matches {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (r Rule) Match(req *http.Request, body []byte) bool {
+	if r.URL != nil {
+		if matches := r.URL.MatchString(req.URL.String()); matches {
+			return true
+		}
+	}
+
+	for key, values := range req.Header {
+		var keyMatches, valueMatches bool
+		if r.Header.Key != nil {
+			if matches := r.Header.Key.MatchString(key); matches {
+				keyMatches = true
+			}
+		}
+		if r.Header.Value != nil {
+			for _, value := range values {
+				if matches := r.Header.Value.MatchString(value); matches {
+					valueMatches = true
+					break
+				}
+			}
+		}
+		// When only key or value is set, match on whatever is set.
+		// When both are set, both must match.
+		switch {
+		case r.Header.Key != nil && r.Header.Value == nil && keyMatches:
+			return true
+		case r.Header.Key == nil && r.Header.Value != nil && valueMatches:
+			return true
+		case r.Header.Key != nil && r.Header.Value != nil && keyMatches && valueMatches:
+			return true
+		}
+	}
+
+	if r.Body != nil {
+		if matches := r.Body.Match(body); matches {
+			return true
+		}
+	}
+
+	return false
+}