From b2d0e93f8ce9705f627b8d1c68088bb1b6e92043 Mon Sep 17 00:00:00 2001
From: Gwilym Inzani <email@gwilym.dev>
Date: Wed, 30 Oct 2024 10:35:48 +0000
Subject: [PATCH] Add serde support to agb_hashmap::HashMap

---
 agb-hashmap/Cargo.toml   |  2 ++
 agb-hashmap/src/lib.rs   |  3 ++
 agb-hashmap/src/serde.rs | 76 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 agb-hashmap/src/serde.rs

diff --git a/agb-hashmap/Cargo.toml b/agb-hashmap/Cargo.toml
index f4f91ac7..fba3c796 100644
--- a/agb-hashmap/Cargo.toml
+++ b/agb-hashmap/Cargo.toml
@@ -9,9 +9,11 @@ exclude = ["/benches"]
 
 [features]
 allocator_api = []
+serde = ["dep:serde"]
 
 [dependencies]
 rustc-hash = { version = "1", default-features = false }
+serde = { version = "1", default-features = false, optional = true }
 
 [dev-dependencies]
 rand = { version = "0.8", default-features = false, features = ["small_rng"] }
diff --git a/agb-hashmap/src/lib.rs b/agb-hashmap/src/lib.rs
index 940df370..30c13fd0 100644
--- a/agb-hashmap/src/lib.rs
+++ b/agb-hashmap/src/lib.rs
@@ -44,6 +44,9 @@ mod allocate {
     pub(crate) use core::alloc::Allocator;
 }
 
+#[cfg(feature = "serde")]
+mod serde;
+
 use core::{
     borrow::Borrow,
     fmt::Debug,
diff --git a/agb-hashmap/src/serde.rs b/agb-hashmap/src/serde.rs
new file mode 100644
index 00000000..e014120f
--- /dev/null
+++ b/agb-hashmap/src/serde.rs
@@ -0,0 +1,76 @@
+use core::{hash::Hash, marker::PhantomData};
+use serde::{
+    de::{MapAccess, Visitor},
+    ser::SerializeMap,
+    Deserialize, Serialize,
+};
+
+use crate::{ClonableAllocator, HashMap};
+
+impl<K: Serialize, V: Serialize, ALLOCATOR: ClonableAllocator> Serialize
+    for HashMap<K, V, ALLOCATOR>
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        let mut map = serializer.serialize_map(Some(self.len()))?;
+
+        for (key, value) in self {
+            map.serialize_entry(key, value)?;
+        }
+
+        map.end()
+    }
+}
+
+impl<'de, K, V> Deserialize<'de> for HashMap<K, V>
+where
+    K: Deserialize<'de> + Hash + Eq,
+    V: Deserialize<'de>,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        deserializer.deserialize_map(HashMapVisitor::new())
+    }
+}
+
+#[derive(Default)]
+struct HashMapVisitor<K, V> {
+    _marker: PhantomData<fn() -> HashMap<K, V>>,
+}
+
+impl<K, V> HashMapVisitor<K, V> {
+    fn new() -> Self {
+        Self {
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, K, V> Visitor<'de> for HashMapVisitor<K, V>
+where
+    K: Deserialize<'de> + Hash + Eq,
+    V: Deserialize<'de>,
+{
+    type Value = HashMap<K, V>;
+
+    fn expecting(&self, formatter: &mut alloc::fmt::Formatter) -> alloc::fmt::Result {
+        formatter.write_str("an agb::HashMap")
+    }
+
+    fn visit_map<M>(self, mut access: M) -> Result<Self::Value, M::Error>
+    where
+        M: MapAccess<'de>,
+    {
+        let mut map = HashMap::with_capacity(access.size_hint().unwrap_or(8));
+
+        while let Some((key, value)) = access.next_entry()? {
+            map.insert(key, value);
+        }
+
+        Ok(map)
+    }
+}