From 2da9d9185e10f0de0bb704fc0b4d39c3dd9ccdc1 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Tue, 26 Mar 2024 12:40:41 +0000
Subject: [PATCH] crypto: Add `OlmMachine::device_creation_time`

Turns out this is useful for https://github.com/element-hq/element-meta/issues/2313.
---
 crates/matrix-sdk-crypto/CHANGELOG.md   |  3 +++
 crates/matrix-sdk-crypto/src/machine.rs | 19 +++++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/crates/matrix-sdk-crypto/CHANGELOG.md b/crates/matrix-sdk-crypto/CHANGELOG.md
index c51e85b2100..14ff187ecd8 100644
--- a/crates/matrix-sdk-crypto/CHANGELOG.md
+++ b/crates/matrix-sdk-crypto/CHANGELOG.md
@@ -19,6 +19,9 @@ Breaking changes:
 
 Additions:
 
+- Expose new method `OlmMachine::device_creation_time`.
+  ([#3275](https://github.com/matrix-org/matrix-rust-sdk/pull/3275))
+
 - Log more details about the Olm session after encryption and decryption.
   ([#3242](https://github.com/matrix-org/matrix-rust-sdk/pull/3242))
 
diff --git a/crates/matrix-sdk-crypto/src/machine.rs b/crates/matrix-sdk-crypto/src/machine.rs
index 7ea6d4e296d..bede64636fe 100644
--- a/crates/matrix-sdk-crypto/src/machine.rs
+++ b/crates/matrix-sdk-crypto/src/machine.rs
@@ -40,8 +40,8 @@ use ruma::{
         AnyToDeviceEvent, MessageLikeEventContent,
     },
     serde::Raw,
-    DeviceId, DeviceKeyAlgorithm, OwnedDeviceId, OwnedDeviceKeyId, OwnedTransactionId, OwnedUserId,
-    RoomId, TransactionId, UInt, UserId,
+    DeviceId, DeviceKeyAlgorithm, MilliSecondsSinceUnixEpoch, OwnedDeviceId, OwnedDeviceKeyId,
+    OwnedTransactionId, OwnedUserId, RoomId, TransactionId, UInt, UserId,
 };
 use serde_json::value::to_raw_value;
 use tokio::sync::Mutex;
@@ -346,6 +346,16 @@ impl OlmMachine {
         &self.inner.device_id
     }
 
+    /// The time at which the `Account` backing this `OlmMachine` was created.
+    ///
+    /// An [`Account`] is created when an `OlmMachine` is first instantiated
+    /// against a given [`Store`], at which point it creates identity keys etc.
+    /// This method returns the timestamp, according to the local clock, at
+    /// which that happened.
+    pub fn device_creation_time(&self) -> MilliSecondsSinceUnixEpoch {
+        self.inner.store.static_account().creation_local_time()
+    }
+
     /// Get the public parts of our Olm identity keys.
     pub fn identity_keys(&self) -> IdentityKeys {
         let account = self.inner.store.static_account();
@@ -2410,8 +2420,13 @@ pub(crate) mod tests {
 
     #[async_test]
     async fn test_create_olm_machine() {
+        let test_start_ts = MilliSecondsSinceUnixEpoch::now();
         let machine = OlmMachine::new(user_id(), alice_device_id()).await;
 
+        let device_creation_time = machine.device_creation_time();
+        assert!(device_creation_time <= MilliSecondsSinceUnixEpoch::now());
+        assert!(device_creation_time >= test_start_ts);
+
         let cache = machine.store().cache().await.unwrap();
         let account = cache.account().await.unwrap();
         assert!(!account.shared());