From d9b25c0e116865171e4f6dd6c13a21e370693858 Mon Sep 17 00:00:00 2001
From: Yuki Kishimoto <yukikishimoto@protonmail.com>
Date: Mon, 23 Sep 2024 15:03:50 -0400
Subject: [PATCH] nostr: add `pow` field to `Filter`

* nostr: check `pow` in `Filter::match_event`
* lmdb: check `pow` in `DatabaseFilter::match_event`

Signed-off-by: Yuki Kishimoto <yukikishimoto@protonmail.com>
---
 crates/nostr-lmdb/src/store/types/filter.rs | 12 ++++++++++++
 crates/nostr/src/types/filter.rs            | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/crates/nostr-lmdb/src/store/types/filter.rs b/crates/nostr-lmdb/src/store/types/filter.rs
index 6a31aea30..ea0236a8a 100644
--- a/crates/nostr-lmdb/src/store/types/filter.rs
+++ b/crates/nostr-lmdb/src/store/types/filter.rs
@@ -5,6 +5,7 @@
 use std::collections::{BTreeMap, BTreeSet, HashSet};
 use std::str::FromStr;
 
+use nostr::nips::nip13;
 use nostr::{Filter, SingleLetterTag, Timestamp};
 use nostr_database::flatbuffers::event_fbs::Fixed32Bytes;
 
@@ -18,6 +19,7 @@ pub struct DatabaseFilter {
     pub search: Option<String>,
     pub since: Option<Timestamp>,
     pub until: Option<Timestamp>,
+    pub pow: Option<u8>,
     pub generic_tags: BTreeMap<SingleLetterTag, BTreeSet<String>>,
 }
 
@@ -78,6 +80,14 @@ impl DatabaseFilter {
         }
     }
 
+    #[inline]
+    fn pow_match(&self, event: &DatabaseEvent) -> bool {
+        match self.pow {
+            Some(difficulty) => nip13::get_leading_zero_bits(event.id.0) >= difficulty,
+            None => true,
+        }
+    }
+
     #[inline]
     pub fn match_event(&self, event: &DatabaseEvent) -> bool {
         self.ids_match(event)
@@ -86,6 +96,7 @@ impl DatabaseFilter {
             && self.since.map_or(true, |t| event.created_at >= t)
             && self.until.map_or(true, |t| event.created_at <= t)
             && self.tag_match(event)
+            && self.pow_match(event)
             && self.search_match(event)
     }
 }
@@ -121,6 +132,7 @@ impl From<Filter> for DatabaseFilter {
             }),
             since: filter.since,
             until: filter.until,
+            pow: filter.pow,
             generic_tags: filter.generic_tags,
         }
     }
diff --git a/crates/nostr/src/types/filter.rs b/crates/nostr/src/types/filter.rs
index 08b47433b..42a0db01a 100644
--- a/crates/nostr/src/types/filter.rs
+++ b/crates/nostr/src/types/filter.rs
@@ -291,6 +291,12 @@ pub struct Filter {
     #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(default)]
     pub limit: Option<usize>,
+    /// Minimum POW difficulty
+    ///
+    /// <https://github.com/nostr-protocol/nips/blob/master/13.md>
+    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(default)]
+    pub pow: Option<u8>,
     /// Generic tag queries
     #[serde(
         flatten,
@@ -768,6 +774,14 @@ impl Filter {
         }
     }
 
+    #[inline]
+    fn pow_match(&self, event: &Event) -> bool {
+        match self.pow {
+            Some(difficulty) => event.id.check_pow(difficulty),
+            None => true,
+        }
+    }
+
     /// Determine if [Filter] match given [Event].
     #[inline]
     pub fn match_event(&self, event: &Event) -> bool {
@@ -777,6 +791,7 @@ impl Filter {
             && self.since.map_or(true, |t| event.created_at >= t)
             && self.until.map_or(true, |t| event.created_at <= t)
             && self.tag_match(event)
+            && self.pow_match(event)
             && self.search_match(event)
     }
 }