commit 61f485ea3f96044ea341cba9bdd17fb149b00fe3
Author: Devin R <devin.ragotzy@gmail.com>
Date:   Fri Jul 17 10:07:03 2020 -0400

    Initial commit sketching out ideas

diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
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--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "state-res"
+version = "0.1.0"
+authors = ["Devin R <devin.ragotzy@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[dependencies]
+petgraph = "0.5.1"
+serde = { version = "1.0.114", features = ["derive"] }
+serde_json = "1.0.56"
+
+[dependencies.ruma]
+git = "https://github.com/ruma/ruma"
+features = ["client-api", "federation-api", "appservice-api"]
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 00000000..fa2a6c50
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,154 @@
+use std::{collections::BTreeMap, time::SystemTime};
+
+use petgraph::Graph;
+use ruma::{
+    events::{
+        room::{self},
+        AnyStateEvent, AnyStrippedStateEvent, AnySyncStateEvent, EventType,
+    },
+    identifiers::{EventId, RoomId, RoomVersionId},
+};
+use serde::{Deserialize, Serialize};
+
+mod state_event;
+mod state_store;
+
+pub use state_event::StateEvent;
+pub use state_store::StateStore;
+
+pub enum ResolutionResult {
+    Conflicted(Vec<StateMap<EventId>>),
+    Resolved(Vec<StateMap<EventId>>),
+}
+
+/// A mapping of event type and state_key to some value `T`, usually an `EventId`.
+pub type StateMap<T> = BTreeMap<(EventType, String), T>;
+
+/// A mapping of `EventId` to `T`, usually a `StateEvent`.
+pub type EventMap<T> = BTreeMap<EventId, T>;
+
+#[derive(Debug, Default, Deserialize, Serialize)] // TODO make the ser/de impls useful
+pub struct StateResolution {
+    // TODO remove pub after initial testing
+    /// The set of resolved events over time.
+    pub resolved_events: Vec<StateEvent>,
+    /// The resolved state, kept to have easy access to the last resolved
+    /// layer of state.
+    pub state: BTreeMap<EventType, BTreeMap<String, StateEvent>>,
+    /// The graph of authenticated events, kept to find the most recent auth event
+    /// in a chain for incoming state sets.
+    pub auth_graph: BTreeMap<EventId, Vec<StateMap<EventId>>>,
+    /// The last known point in the state graph.
+    pub most_recent_resolved: Option<(EventType, String)>,
+
+    // fields for temp storage during resolution
+    pub conflicting_events: Vec<StateEvent>,
+}
+
+impl StateResolution {
+    /// Resolve sets of state events as they come in. Internally `StateResolution` builds a graph
+    /// and an auth chain to allow for state conflict resolution.
+    pub fn resolve(
+        &mut self,
+        room_id: &RoomId,
+        room_version: &RoomVersionId,
+        state_sets: Vec<StateMap<EventId>>,
+        store: &mut dyn StateStore,
+        // TODO actual error handling (`thiserror`??)
+    ) -> Result<ResolutionResult, serde_json::Error> {
+        let mut event_map = EventMap::new();
+        // split non-conflicting and conflicting state
+        let (clean, mut conflicting) = self.seperate(&state_sets);
+
+        if conflicting.is_empty() {
+            return Ok(ResolutionResult::Resolved(clean));
+        }
+
+        // the set of auth events that are not common across server forks
+        let mut auth_diff = self.get_auth_chain_diff(&state_sets, &mut event_map, store)?;
+
+        // add the auth_diff to conflicting now we have a full set of conflicting events
+        auth_diff.extend(conflicting.iter().flat_map(|map| map.values().cloned()));
+        let all_conflicted = auth_diff;
+
+        let all_conflicted = conflicting;
+
+        let power_events = all_conflicted
+            .iter()
+            .filter(is_power_event)
+            .flat_map(|map| map.values())
+            .cloned()
+            .collect::<Vec<_>>();
+
+        // sort the power events based on power_level/clock/event_id and outgoing/incoming edges
+        let sorted_power_levels = self.revers_topological_power_sort(
+            room_id,
+            &power_events,
+            &mut event_map,
+            store,
+            &all_conflicted,
+        );
+
+        // sequentially auth check each event.
+        let resolved = self.iterative_auth_check(
+            room_id,
+            room_version,
+            &power_events,
+            &clean,
+            &mut event_map,
+            store,
+        );
+
+        // TODO return something not a place holder
+        Ok(ResolutionResult::Resolved(vec![]))
+    }
+
+    fn seperate(
+        &mut self,
+        state_sets: &[StateMap<EventId>],
+    ) -> (Vec<StateMap<EventId>>, Vec<StateMap<EventId>>) {
+        panic!()
+    }
+
+    /// Returns a Vec of deduped EventIds that appear in some chains but no others.
+    fn get_auth_chain_diff(
+        &mut self,
+        state_sets: &[StateMap<EventId>],
+        event_map: &EventMap<StateEvent>,
+        store: &mut dyn StateStore,
+    ) -> Result<Vec<EventId>, serde_json::Error> {
+        panic!()
+    }
+
+    fn revers_topological_power_sort(
+        &mut self,
+        room_id: &RoomId,
+        power_events: &[EventId],
+        event_map: &EventMap<StateEvent>,
+        store: &mut dyn StateStore,
+        conflicted_set: &[StateMap<EventId>],
+    ) -> Vec<StateEvent> {
+        panic!()
+    }
+
+    fn iterative_auth_check(
+        &mut self,
+        room_id: &RoomId,
+        room_version: &RoomVersionId,
+        power_events: &[EventId],
+        unconflicted_state: &[StateMap<EventId>],
+        event_map: &EventMap<StateEvent>,
+        store: &mut dyn StateStore,
+    ) -> Vec<StateEvent> {
+        panic!()
+    }
+}
+
+pub fn is_power_event(event: &&StateMap<EventId>) -> bool {
+    true
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+}
diff --git a/src/state_event.rs b/src/state_event.rs
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index 00000000..a42c1109
--- /dev/null
+++ b/src/state_event.rs
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+use ruma::events::{
+    from_raw_json_value, AnyStateEvent, AnyStrippedStateEvent, AnySyncStateEvent, EventDeHelper,
+};
+use serde::{de, Serialize};
+use serde_json::value::RawValue as RawJsonValue;
+
+#[derive(Clone, Debug, Serialize)]
+#[serde(untagged)]
+pub enum StateEvent {
+    Full(AnyStateEvent),
+    Sync(AnySyncStateEvent),
+    Stripped(AnyStrippedStateEvent),
+}
+
+impl<'de> de::Deserialize<'de> for StateEvent {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: de::Deserializer<'de>,
+    {
+        let json = Box::<RawJsonValue>::deserialize(deserializer)?;
+        let EventDeHelper {
+            state_key,
+            event_id,
+            room_id,
+            unsigned,
+            ..
+        } = from_raw_json_value(&json)?;
+
+        // Determine whether the event is a full, sync, or stripped
+        // based on the fields present.
+        if room_id.is_some() {
+            Ok(match unsigned {
+                Some(unsigned) if unsigned.redacted_because.is_some() => {
+                    panic!("TODO deal with redacted events")
+                }
+                _ => StateEvent::Full(from_raw_json_value(&json)?),
+            })
+        } else if event_id.is_some() {
+            Ok(match unsigned {
+                Some(unsigned) if unsigned.redacted_because.is_some() => {
+                    panic!("TODO deal with redacted events")
+                }
+                _ => StateEvent::Sync(from_raw_json_value(&json)?),
+            })
+        } else {
+            Ok(StateEvent::Stripped(from_raw_json_value(&json)?))
+        }
+    }
+}
diff --git a/src/state_store.rs b/src/state_store.rs
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index 00000000..f84e8127
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+++ b/src/state_store.rs
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+use std::{collections::BTreeMap, time::SystemTime};
+
+use petgraph::Graph;
+use ruma::{
+    events::{
+        room::{self},
+        AnyStateEvent, AnyStrippedStateEvent, AnySyncStateEvent, EventType,
+    },
+    identifiers::{EventId, RoomId, RoomVersionId},
+};
+
+use crate::StateEvent;
+
+pub trait StateStore {
+    /// Returns the events that correspond to the `event_ids` sorted in the same order.
+    fn get_events(&self, event_ids: &[EventId]) -> Result<Vec<StateEvent>, serde_json::Error>;
+
+    /// Returns a tuple of requested state events from `event_id` and the auth chain events that
+    /// relate to the.
+    fn get_remote_state_for_room(
+        &self,
+        room_id: &RoomId,
+        version: &RoomVersionId,
+        event_id: &EventId,
+    ) -> Result<(Vec<StateEvent>, Vec<StateEvent>), serde_json::Error>;
+}
diff --git a/state.md b/state.md
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index 00000000..cc5e8575
--- /dev/null
+++ b/state.md
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+Would it be possible to abstract state res into a `ruma-state-res` crate? I've been thinking about something along the lines of
+```rust
+// The would need to be Serialize/Deserialize to save state 
+struct StateResV2 {
+    resolved_events: Vec<Event>,
+    state_graph: of indexes into the events field?,
+    most_recent_resolved: index or ptr into the graph?,
+    // fields for temp storage during resolution
+    conflicting_events: Vec<Event>,
+}
+
+impl StateResV2 {
+    /// The point of this all add nonconflicting events to the graph
+    /// and resolve and add conflicting events.
+    fn resolve(&mut self, events: Vec<Event>) -> Vec<Event> { }
+
+}
+
+```
+Now to be totally fair I have no real understanding of state res 
diff --git a/tests/init.rs b/tests/init.rs
new file mode 100644
index 00000000..93efbc12
--- /dev/null
+++ b/tests/init.rs
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+use std::convert::TryFrom;
+
+use ruma::{
+    events::{
+        room::{self},
+        AnyStateEvent, AnyStrippedStateEvent, AnySyncStateEvent, EventType,
+    },
+    identifiers::{EventId, RoomId, RoomVersionId},
+};
+use serde_json::{from_value as from_json_value, json, Value as JsonValue};
+use state_res::{ResolutionResult, StateEvent, StateResolution, StateStore};
+
+// TODO make this an array of events
+fn federated_json() -> JsonValue {
+    json!({
+        "content": {
+            "creator": "@example:example.org",
+            "m.federate": true,
+            "predecessor": {
+                "event_id": "$something:example.org",
+                "room_id": "!oldroom:example.org"
+            },
+            "room_version": "6"
+        },
+        "event_id": "$aaa:example.org",
+        "origin_server_ts": 1,
+        "room_id": "!room_id:example.org",
+        "sender": "@alice:example.org",
+        "state_key": "",
+        "type": "m.room.create",
+        "unsigned": {
+            "age": 1234
+        }
+    })
+}
+
+fn room_create() -> JsonValue {
+    json!({
+        "content": {
+            "creator": "@example:example.org",
+            "m.federate": true,
+            "predecessor": {
+                "event_id": "$something:example.org",
+                "room_id": "!oldroom:example.org"
+            },
+            "room_version": "6"
+        },
+        "event_id": "$aaa:example.org",
+        "origin_server_ts": 1,
+        "room_id": "!room_id:example.org",
+        "sender": "@alice:example.org",
+        "state_key": "",
+        "type": "m.room.create",
+        "unsigned": {
+            "age": 1234
+        }
+    })
+}
+
+fn join_rules() -> JsonValue {
+    json!({
+        "content": {
+            "join_rule": "public"
+        },
+        "event_id": "$bbb:example.org",
+        "origin_server_ts": 2,
+        "room_id": "!room_id:example.org",
+        "sender": "@alice:example.org",
+        "state_key": "",
+        "type": "m.room.join_rules",
+        "unsigned": {
+            "age": 1234
+        }
+    })
+}
+
+fn join_event() -> JsonValue {
+    json!({
+        "content": {
+            "avatar_url": null,
+            "displayname": "example",
+            "membership": "join"
+        },
+        "event_id": "$ccc:example.org",
+        "membership": "join",
+        "room_id": "!room_id:example.org",
+        "origin_server_ts": 3,
+        "sender": "@alice:example.org",
+        "state_key": "@alice:example.org",
+        "type": "m.room.member",
+        "unsigned": {
+            "age": 1,
+            "replaces_state": "$151800111315tsynI:example.org",
+            "prev_content": {
+                "avatar_url": null,
+                "displayname": "example",
+                "membership": "invite"
+            }
+        }
+    })
+}
+
+fn power_levels() -> JsonValue {
+    json!({
+        "content": {
+            "ban": 50,
+            "events": {
+                "m.room.name": 100,
+                "m.room.power_levels": 100
+            },
+            "events_default": 0,
+            "invite": 50,
+            "kick": 50,
+            "notifications": {
+                "room": 20
+            },
+            "redact": 50,
+            "state_default": 50,
+            "users": {
+                "@example:example.org": 100
+            },
+            "users_default": 0
+        },
+        "event_id": "$ddd:example.org",
+        "origin_server_ts": 4,
+        "room_id": "!room_id:example.org",
+        "sender": "@example:example.org",
+        "state_key": "",
+        "type": "m.room.power_levels",
+        "unsigned": {
+            "age": 1234
+        }
+    })
+}
+
+pub struct TestStore;
+
+impl StateStore for TestStore {
+    fn get_events(&self, events: &[EventId]) -> Result<Vec<StateEvent>, serde_json::Error> {
+        Ok(vec![from_json_value(power_levels())?])
+    }
+
+    fn get_remote_state_for_room(
+        &self,
+        room_id: &RoomId,
+        version: &RoomVersionId,
+        event_id: &EventId,
+    ) -> Result<(Vec<StateEvent>, Vec<StateEvent>), serde_json::Error> {
+        Ok((
+            vec![from_json_value(federated_json())?],
+            vec![from_json_value(power_levels())?],
+        ))
+    }
+}
+
+#[test]
+fn it_works() {
+    let mut store = TestStore;
+
+    let room_id = RoomId::try_from("!room_id:example.org").unwrap();
+    let room_version = RoomVersionId::version_6();
+
+    let a = from_json_value::<StateEvent>(room_create()).unwrap();
+    let b = from_json_value::<StateEvent>(join_rules()).unwrap();
+    let c = from_json_value::<StateEvent>(join_event()).unwrap();
+
+    let mut resolver = StateResolution::default();
+
+    let res = resolver
+        .resolve(&room_id, &room_version, vec![a.clone()], &mut store)
+        .unwrap();
+    assert!(if let ResolutionResult::Resolved(_) = res {
+        true
+    } else {
+        false
+    });
+
+    let resolved = resolver
+        .resolve(&room_id, &room_version, vec![b, c], &mut store)
+        .unwrap();
+
+    assert!(resolver.conflicting_events.is_empty());
+    assert_eq!(resolver.resolved_events.len(), 3);
+}