merge predicates in one file

examples/gno.land/r/demo/mail/predicates.gno

@@ -1,5 +1,59 @@
 package mail
 
+import (
+	"std"
+	"strings"
+	"time"
+)
+
 type Predicate interface {
 	Satisfy(mail *Mail) bool
 }
+
+type (
+	SenderIs       struct{ sender std.Address }
+	RecipientIs    struct{ recipient std.Address }
+	AndPred        struct{ a []Predicate }
+	Contains       struct{ s string }
+	ContainsEither struct{ a []string }
+	TopicContains  struct{ s string }
+	Not            struct{ pred Predicate }
+	TimeBefore     struct{ t time.Time } // <=
+	TimeAfter      struct{ t time.Time } // >=
+	TimeBetween    struct {
+		min time.Time
+		max time.Time
+	}
+)
+
+// `And(Contains("virus"), TimeBefore(covid))`
+func And(preds ...Predicate) Predicate { return AndPred{preds} }
+
+func (o AndPred) Satisfy(mail *Mail) bool     { return mail.Satisfies(o.a) }
+func (x SenderIs) Satisfy(mail *Mail) bool    { return mail.sender == x.sender }
+func (x RecipientIs) Satisfy(mail *Mail) bool { return mail.recipient == x.recipient }
+
+// searches are always case-insensitive, and within Topic+Body
+// You may combine if neeeded: Not{Contains} or And{Not{Contains}, Not{Contains}}
+func (o Contains) Satisfy(mail *Mail) bool { return mail.Contains(o.s) }
+func (o Not) Satisfy(mail *Mail) bool      { return !mail.Satisfies([]Predicate{o.pred}) }
+
+func (o TopicContains) Satisfy(mail *Mail) bool {
+	topic := strings.ToLower(mail.topic)
+	return strings.Contains(topic, strings.ToLower(o.s))
+}
+
+func (o ContainsEither) Satisfy(mail *Mail) bool {
+	for _, substring := range o.a {
+		if mail.Contains(substring) {
+			return true
+		}
+	}
+	return false
+}
+
+func (o TimeBefore) Satisfy(mail *Mail) bool { return !mail.time.After(o.t) }
+func (o TimeAfter) Satisfy(mail *Mail) bool  { return !mail.time.Before(o.t) }
+func (o TimeBetween) Satisfy(mail *Mail) bool {
+	return !mail.time.Before(o.min) && !mail.time.After(o.max)
+}