lane idx and tee connection types

cutting down our memory usage from 32+ to EIGHT! also tee connection
types

Author: philocalyst

asyncgit/src/graph/mod.rs

@@ -8,34 +8,55 @@ pub use walker::GraphWalker;
 /// The maximum number of colors to use for graph lanes
 pub const MAX_LANE_COLORS: usize = 16;
 
-/// The type of connection between nodes in the graph
+// Yes, there are repositories where this is exceeded
+// Are they very rare? Yes.
+// On most terminals can more than 256 lanes even be represneted usefully? Not really.
+pub type LaneIdx = u8;
+
+/// Convert a lane position into the compact [`LaneIdx`]
+/// representation. This way we can keep full granularity when computing,
+/// but not when storing.
+pub(crate) fn to_lane_idx(lane: usize) -> LaneIdx {
+	LaneIdx::try_from(lane).unwrap_or(LaneIdx::MAX)
+}
+
+/// The type of connection between nodes in the graph.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum ConnectionType {
 	Vertical,
 	VerticalDotted,
-	Cross,
 	CommitNormal,
 	CommitBranch,
 	CommitMerge,
 	CommitStash,
 	CommitUncommitted,
+	/// a bridge turning down into a lane that starts here
 	MergeBridgeStart,
+	/// a bridge passing over an empty lane slot
 	MergeBridgeMid,
+	/// a bridge turning down, lane starting to its right
 	MergeBridgeEnd,
-	BranchDown,
+	/// a lane from above turning left into a commit
 	BranchUp,
+	///  a lane from above turning right into a commit
 	BranchUpRight,
-	BranchUpMergeStart,
-	BranchUpRightMergeEnd,
+	/// a continuing lane absorbing a bridge from its left
+	TeeLeft,
+	/// a continuing lane absorbing a bridge from its right
+	TeeRight,
+	/// a lane ending from above while a bridge passes through
+	TeeUp,
+	/// a lane starting downward while a bridge passes through
+	TeeDown,
 }
 
 #[derive(Clone, Debug, Default)]
 pub struct GraphRow {
 	/// Number of active lanes at this commit row
-	pub lane_count: usize,
+	pub lane_count: LaneIdx,
 
 	/// Which lane index this commit sits on
-	pub commit_lane: usize,
+	pub commit_lane: LaneIdx,
 
 	/// Whether this is a merge commit (two parents)
 	pub is_merge: bool,
@@ -49,13 +70,13 @@ pub struct GraphRow {
 	/// Connections emitted per lane:
 	/// None = empty space
 	/// Some((ConnectionType, `color_index`)) = draw this connector in this color
-	pub lanes: Vec<Option<(ConnectionType, usize)>>,
+	pub lanes: Vec<Option<(ConnectionType, LaneIdx)>>,
 
 	/// Horizontal merge bridge: if this commit merges rightward,
 	/// (`from_lane`, `to_lane`) — the span to draw ─ ╭ ╮ across
-	pub merge_bridge: Option<(usize, usize)>,
+	pub merge_bridge: Option<(LaneIdx, LaneIdx)>,
 
 	/// Horizontal branch bridges: if this commit spawns branches,
 	/// spans to draw ─ ╭ ╮ across
-	pub branches: Vec<(usize, usize)>,
+	pub branches: Vec<(LaneIdx, LaneIdx)>,
 }