From ba7f7b539817511cb3b30fa78e04e9aa70c05008 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@alhur.es>
Date: Sun, 14 Feb 2021 22:38:54 -0300
Subject: [PATCH] add filter helpers following the new nip-01.

---
 filter/filter.go | 104 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 filter/filter.go

diff --git a/filter/filter.go b/filter/filter.go
new file mode 100644
index 0000000..093e6b5
--- /dev/null
+++ b/filter/filter.go
@@ -0,0 +1,104 @@
+package filter
+
+import "github.com/fiatjaf/go-nostr/event"
+
+type EventFilter struct {
+	ID         string   `json:"id,omitempty"`
+	Author     string   `json:"author,omitempty"`
+	Kind       uint8    `json:"kind,omitempty"`
+	Authors    []string `json:"authors,omitempty"`
+	TagEvent   string   `json:"#e,omitempty"`
+	TagProfile string   `json:"#p,omitempty"`
+	Since      uint32   `json:"since,omitempty"`
+}
+
+func (ef EventFilter) Matches(event *event.Event) bool {
+	if event == nil {
+		return false
+	}
+
+	if ef.ID != "" && ef.ID != event.ID {
+		return false
+	}
+
+	if ef.Author != "" && ef.Author != event.PubKey {
+		return false
+	}
+
+	if ef.Authors != nil {
+		found := false
+		for _, pubkey := range ef.Authors {
+			if pubkey == event.PubKey {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	if ef.TagEvent != "" {
+		found := false
+		for _, tag := range event.Tags {
+			if len(tag) < 2 {
+				continue
+			}
+
+			tagType, ok := tag[0].(string)
+			if !ok {
+				continue
+			}
+
+			if tagType == "e" {
+				taggedID, ok := tag[1].(string)
+				if !ok {
+					continue
+				}
+
+				if taggedID == ef.TagEvent {
+					found = true
+					break
+				}
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	if ef.TagProfile != "" {
+		found := false
+		for _, tag := range event.Tags {
+			if len(tag) < 2 {
+				continue
+			}
+
+			tagType, ok := tag[0].(string)
+			if !ok {
+				continue
+			}
+
+			if tagType == "p" {
+				taggedID, ok := tag[1].(string)
+				if !ok {
+					continue
+				}
+
+				if taggedID == ef.TagProfile {
+					found = true
+					break
+				}
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	if ef.Since != 0 && event.CreatedAt < ef.Since {
+		return false
+	}
+
+	return true
+}