diff --git a/gpx-rs/src/algorithm/smooth.rs b/gpx-rs/src/algorithm/smooth.rs
index 636e6948b..9c520419c 100644
--- a/gpx-rs/src/algorithm/smooth.rs
+++ b/gpx-rs/src/algorithm/smooth.rs
@@ -8,43 +8,44 @@ macro_rules! for_each_window {
         |$a:ident, $b:ident| $distance:expr,
         |$i:ident, $l:ident, $r:ident| $body:block,
     ) => {{
-        let mut start = $left.unwrap_or_default();
-        let mut cur = $left;
-        while let Some(idx) = cur {
+        let mut window_start = $left.unwrap_or_default();
+        let mut window_center = $left;
+        let mut window_end = $left.unwrap_or_default();
+        while let Some(idx) = window_center {
             // advance left if needed
-            while start != idx && {
-                let $a = start;
+            while window_start != idx && {
+                let $a = window_start;
                 let $b = idx;
                 $distance
             } > $window {
-                if let Some(next) = $trkseg.next_index(Some(start)) {
+                if let Some(next) = $trkseg.next_index(Some(window_start)) {
                     if next == idx {
                         break;
                     }
-                    start = next;
+                    window_start = next;
                 } else {
                     break;
                 }
             }
             // advance right if needed
-            let mut end = idx;
-            while let Some(next) = $trkseg.next_index(Some(end)) {
-                if {
+            window_end = window_end.max(idx);
+            while let Some(next) = $trkseg.next_index(Some(window_end)) {
+                if window_end != idx && {
                     let $a = idx;
-                    let $b = end;
+                    let $b = next;
                     $distance
                 } > $window {
                     break;
                 }
-                end = next;
+                window_end = next;
             }
             // apply body
             let $i = idx;
-            let $l = start;
-            let $r = end;
+            let $l = window_start;
+            let $r = window_end;
             $body
             // go next
-            cur = $trkseg.next_index(cur);
+            window_center = $trkseg.next_index(window_center);
         }
     }};
 }
diff --git a/gpx-rs/src/buffer/coordinates.rs b/gpx-rs/src/buffer/coordinates.rs
new file mode 100644
index 000000000..25282d4fa
--- /dev/null
+++ b/gpx-rs/src/buffer/coordinates.rs
@@ -0,0 +1,4 @@
+pub struct CoordinatesBuffer {
+    pub lng: Vec<f64>,
+    pub lat: Vec<f64>,
+}
diff --git a/gpx-rs/src/buffer/mod.rs b/gpx-rs/src/buffer/mod.rs
new file mode 100644
index 000000000..88a55c55a
--- /dev/null
+++ b/gpx-rs/src/buffer/mod.rs
@@ -0,0 +1,5 @@
+mod coordinates;
+mod statistics;
+
+pub use coordinates::*;
+pub use statistics::*;
diff --git a/gpx-rs/src/statistics/buffer.rs b/gpx-rs/src/buffer/statistics.rs
similarity index 92%
rename from gpx-rs/src/statistics/buffer.rs
rename to gpx-rs/src/buffer/statistics.rs
index 89057d1f3..09c12528e 100644
--- a/gpx-rs/src/statistics/buffer.rs
+++ b/gpx-rs/src/buffer/statistics.rs
@@ -1,11 +1,11 @@
-use crate::statistics::{GPXStatistics, GlobalStatistics, sum_options};
+use crate::statistics::{GlobalStatistics, Statistics, sum_options};
 
 #[derive(Debug, Default)]
 pub struct StatisticsBuffer {
     pub total_distance: Vec<f64>,
     pub moving_distance: Vec<f64>,
-    pub total_time: Vec<i64>,
-    pub moving_time: Vec<i64>,
+    pub total_time: Vec<i32>,
+    pub moving_time: Vec<i32>,
     pub speed: Vec<f64>,
     pub elevation_gain: Vec<f64>,
     pub elevation_loss: Vec<f64>,
@@ -15,7 +15,7 @@ pub struct StatisticsBuffer {
 }
 
 impl StatisticsBuffer {
-    pub fn update(&mut self, stats: &[&GPXStatistics]) {
+    pub fn update(&mut self, stats: &[&Statistics]) {
         self.total_distance.clear();
         self.moving_distance.clear();
         self.total_time.clear();
diff --git a/gpx-rs/src/engine.rs b/gpx-rs/src/engine.rs
index fd26c09dd..dc26b5e75 100644
--- a/gpx-rs/src/engine.rs
+++ b/gpx-rs/src/engine.rs
@@ -2,75 +2,151 @@
 
 use std::rc::Rc;
 
-use js_sys::Function;
+use js_sys::{Float64Array, Function, Int32Array};
 use uuid::Uuid;
 use wasm_bindgen::prelude::*;
 
 use crate::{
-    gpx::GPXFile,
+    buffer::StatisticsBuffer,
+    gpx::{File, FileId},
     io::parse,
     selection::Selection,
     state::{Stack, StackEntry},
-    statistics::StatisticsBuffer,
+    statistics::StatisticsCache,
 };
 
+extern crate console_error_panic_hook;
+
+#[derive(Debug, Default)]
 #[wasm_bindgen]
 pub struct Engine {
     stack: Stack,
     selection: Selection,
-    statistics: StatisticsBuffer,
-    callback: Function,
+    statistics_cache: StatisticsCache,
+    statistics_buffer: StatisticsBuffer,
+    callback: Option<Function>,
 }
 
 #[wasm_bindgen]
 impl Engine {
     #[wasm_bindgen(constructor)]
     pub fn new(callback: Function) -> Self {
+        console_error_panic_hook::set_once();
         Self {
             stack: Default::default(),
             selection: Default::default(),
-            statistics: Default::default(),
-            callback,
+            statistics_cache: Default::default(),
+            statistics_buffer: Default::default(),
+            callback: Some(callback),
         }
     }
 
-    #[wasm_bindgen]
+    pub fn total_distance(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.total_distance) }
+    }
+
+    pub fn moving_distance(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.moving_distance) }
+    }
+
+    pub fn total_time(&self) -> Int32Array {
+        unsafe { Int32Array::view(&self.statistics_buffer.total_time) }
+    }
+
+    pub fn moving_time(&self) -> Int32Array {
+        unsafe { Int32Array::view(&self.statistics_buffer.moving_time) }
+    }
+
+    pub fn speed(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.speed) }
+    }
+
+    pub fn elevation_gain(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.elevation_gain) }
+    }
+
+    pub fn elevation_loss(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.elevation_loss) }
+    }
+
+    pub fn slope(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.slope) }
+    }
+
+    pub fn slope_segment_slope(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.slope_segment_slope) }
+    }
+
+    pub fn slope_segment_distance(&self) -> Float64Array {
+        unsafe { Float64Array::view(&self.statistics_buffer.slope_segment_distance) }
+    }
+
     pub fn create_file(&mut self, name: &str) {
-        let mut file = GPXFile::default();
-        file.info.name = name.to_string();
-        self.stack.create_and_push_next(|entry: &mut StackEntry| {
+        self.event_loop(|entry| {
+            let mut file = File::default();
+            file.info.name = name.to_string();
             entry.insert(file.id, Rc::new(file));
             true
         });
     }
 
-    #[wasm_bindgen]
     pub fn load_file(&mut self, data: &[u8]) {
-        if let Ok(file) = parse(data) {
-            self.stack.create_and_push_next(|entry: &mut StackEntry| {
+        self.event_loop(|entry| {
+            if let Ok(file) = parse(data) {
                 entry.insert(file.id, Rc::new(file));
                 true
-            });
-        }
-        let _ = self.callback.call1(&JsValue::NULL, &JsValue::from("done!"));
+            } else {
+                false
+            }
+        });
     }
 
-    #[wasm_bindgen]
     pub fn delete_file(&mut self, id: &[u8]) {
-        if let Ok(id) = Uuid::from_slice(id) {
-            self.stack
-                .create_and_push_next(|entry: &mut StackEntry| entry.remove(&id).is_some());
-        }
+        self.event_loop(|entry| {
+            if let Ok(id) = Uuid::from_slice(id) {
+                let id = FileId(id);
+                entry.remove(&id).is_some()
+            } else {
+                false
+            }
+        });
     }
 
-    fn event_loop(&mut self) {
-        // Control flow
-        // - get lock to cancel any other updates
-        // - update files
-        // - update separate statistics
-        // - update selection
-        // - update selection statistics
-        // self.statistics.update(stats);
-        // - notify UI through callback (changed files, updated selection, new stats)
+    fn event_loop<F>(&mut self, f: F)
+    where
+        F: FnOnce(&mut StackEntry) -> bool,
+    {
+        if let Some(diff) = self.stack.create_and_push_next(f) {
+            self.selection.select(diff.added[0]);
+            self.statistics_cache.update(self.stack.current());
+            self.statistics_buffer.update(
+                &self
+                    .statistics_cache
+                    .get(self.stack.current(), &self.selection),
+            );
+            if let Some(c) = &self.callback {
+                let _ = c.call0(&JsValue::NULL);
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{fs::File, io::Read};
+
+    use super::*;
+
+    #[test]
+    fn test_load_file() {
+        let mut engine = Engine::default();
+
+        let mut f = File::open("data/simple.gpx").unwrap();
+        let mut data = String::new();
+        let _ = f.read_to_string(&mut data);
+
+        engine.load_file(data.as_bytes());
+
+        assert_eq!(engine.statistics_buffer.total_distance.len(), 80);
     }
 }
diff --git a/gpx-rs/src/gpx/chunk.rs b/gpx-rs/src/gpx/chunk.rs
index 31b8a11d7..7d624ad09 100644
--- a/gpx-rs/src/gpx/chunk.rs
+++ b/gpx-rs/src/gpx/chunk.rs
@@ -4,19 +4,19 @@ use crate::gpx::{Trackpoint, Waypoint};
 
 static MAX_TRKPT_CHUNK_SIZE: usize = 4096;
 
-#[derive(Debug)]
-pub struct TrackpointChunk {
-    pub id: Uuid,
-    pub trkpt: Vec<Trackpoint>,
+#[derive(Debug, PartialEq, Eq)]
+pub struct TrackpointChunkId(Uuid);
+
+impl Default for TrackpointChunkId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
 }
 
-impl Default for TrackpointChunk {
-    fn default() -> Self {
-        Self {
-            id: Uuid::new_v4(),
-            trkpt: Default::default(),
-        }
-    }
+#[derive(Debug, Default)]
+pub struct TrackpointChunk {
+    pub id: TrackpointChunkId,
+    pub trkpt: Vec<Trackpoint>,
 }
 
 impl PartialEq for TrackpointChunk {
@@ -31,21 +31,21 @@ impl TrackpointChunk {
     }
 }
 
-static MAX_WPT_CHUNK_SIZE: usize = 128;
+#[derive(Debug, PartialEq, Eq)]
+pub struct WaypointChunkId(Uuid);
 
-#[derive(Debug)]
-pub struct WaypointChunk {
-    pub id: Uuid,
-    pub wpt: Vec<Waypoint>,
+impl Default for WaypointChunkId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
 }
 
-impl Default for WaypointChunk {
-    fn default() -> Self {
-        Self {
-            id: Uuid::new_v4(),
-            wpt: Default::default(),
-        }
-    }
+static MAX_WPT_CHUNK_SIZE: usize = 128;
+
+#[derive(Debug, Default)]
+pub struct WaypointChunk {
+    pub id: WaypointChunkId,
+    pub wpt: Vec<Waypoint>,
 }
 
 impl PartialEq for WaypointChunk {
diff --git a/gpx-rs/src/gpx/file.rs b/gpx-rs/src/gpx/file.rs
index 35459846a..8ccfcd8ef 100644
--- a/gpx-rs/src/gpx/file.rs
+++ b/gpx-rs/src/gpx/file.rs
@@ -4,28 +4,26 @@ use uuid::Uuid;
 
 use crate::gpx::{Link, Track, WaypointChunk};
 
-#[derive(Debug, PartialEq)]
-pub struct GPXFile {
-    pub id: Uuid,
-    pub info: GPXFileInfo,
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct FileId(pub Uuid);
+
+impl Default for FileId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
+#[derive(Debug, Default, PartialEq)]
+pub struct File {
+    pub id: FileId,
+    pub info: FileInfo,
     pub trk: Vec<Track>,
     pub wpt: Vec<Rc<WaypointChunk>>,
     // TODO routes
 }
 
-impl Default for GPXFile {
-    fn default() -> Self {
-        Self {
-            id: Uuid::new_v4(),
-            info: Default::default(),
-            trk: Default::default(),
-            wpt: Default::default(),
-        }
-    }
-}
-
 #[derive(Debug, Default, PartialEq)]
-pub struct GPXFileInfo {
+pub struct FileInfo {
     pub name: String,
     pub desc: Option<String>,
     pub author: Option<Author>,
diff --git a/gpx-rs/src/gpx/segment.rs b/gpx-rs/src/gpx/segment.rs
index 50dd59723..7d6104d91 100644
--- a/gpx-rs/src/gpx/segment.rs
+++ b/gpx-rs/src/gpx/segment.rs
@@ -1,9 +1,31 @@
 use std::{ops::Index, rc::Rc};
 
+use uuid::Uuid;
+
 use crate::gpx::{Trackpoint, TrackpointChunk};
 
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct TrackSegmentId(Uuid);
+
+impl Default for TrackSegmentId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct TrackSegmentRevisionId(Uuid);
+
+impl Default for TrackSegmentRevisionId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
 #[derive(Debug, Default, PartialEq)]
 pub struct TrackSegment {
+    pub id: TrackSegmentId,
+    pub rev_id: TrackSegmentRevisionId,
     chunks: Vec<Rc<TrackpointChunk>>,
     cumul_length: Vec<usize>,
 }
diff --git a/gpx-rs/src/gpx/track.rs b/gpx-rs/src/gpx/track.rs
index 86d1c761c..00f5f0a8f 100644
--- a/gpx-rs/src/gpx/track.rs
+++ b/gpx-rs/src/gpx/track.rs
@@ -1,7 +1,19 @@
+use uuid::Uuid;
+
 use crate::gpx::{Link, TrackSegment};
 
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct TrackId(Uuid);
+
+impl Default for TrackId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
 #[derive(Debug, Default, PartialEq)]
 pub struct Track {
+    pub id: TrackId,
     pub info: TrackInfo,
     pub trkseg: Vec<TrackSegment>,
 }
diff --git a/gpx-rs/src/gpx/trackpoint.rs b/gpx-rs/src/gpx/trackpoint.rs
index 35dac699c..d08800dff 100644
--- a/gpx-rs/src/gpx/trackpoint.rs
+++ b/gpx-rs/src/gpx/trackpoint.rs
@@ -11,9 +11,3 @@ pub struct Trackpoint {
     pub power: Option<u16>,
     // TODO OSM data? or store intervals at a higher level?
 }
-
-impl Trackpoint {
-    pub fn time_diff(&self, other: &Trackpoint) -> Option<i64> {
-        self.time.zip(other.time).map(|(t1, t2)| t1 - t2)
-    }
-}
diff --git a/gpx-rs/src/gpx/waypoint.rs b/gpx-rs/src/gpx/waypoint.rs
index 9a2fc46d3..88b5ae335 100644
--- a/gpx-rs/src/gpx/waypoint.rs
+++ b/gpx-rs/src/gpx/waypoint.rs
@@ -1,7 +1,19 @@
+use uuid::Uuid;
+
 use crate::gpx::{Link, LngLat};
 
+#[derive(Debug, PartialEq, Eq)]
+pub struct WaypointId(Uuid);
+
+impl Default for WaypointId {
+    fn default() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
 #[derive(Debug, Default)]
 pub struct Waypoint {
+    pub id: WaypointId,
     pub coordinates: LngLat,
     pub ele: f64,
     pub time: Option<i64>,
diff --git a/gpx-rs/src/io/parse.rs b/gpx-rs/src/io/parse.rs
index 3f8bf285d..3f45f33ee 100644
--- a/gpx-rs/src/io/parse.rs
+++ b/gpx-rs/src/io/parse.rs
@@ -1,7 +1,7 @@
 use std::rc::Rc;
 
 use crate::gpx::{
-    Author, GPXFile, Link, LngLat, Track, TrackSegment, Trackpoint, TrackpointChunk, Waypoint,
+    Author, File, Link, LngLat, Track, TrackSegment, Trackpoint, TrackpointChunk, Waypoint,
     WaypointChunk,
 };
 use chrono::DateTime;
@@ -50,10 +50,10 @@ fn parse_coordinates(attributes: Attributes<'_>) -> LngLat {
     coordinates
 }
 
-pub fn parse(data: &[u8]) -> Result<GPXFile, Error> {
+pub fn parse(data: &[u8]) -> Result<File, Error> {
     let mut reader = Reader::from_reader(data);
     let mut buf = vec![];
-    let mut gpx = GPXFile::default();
+    let mut gpx = File::default();
     let mut stack: Vec<GPXElement> = vec![];
     let mut trkpt_chunk = TrackpointChunk::default();
     let mut wpt_chunk = WaypointChunk::default();
diff --git a/gpx-rs/src/lib.rs b/gpx-rs/src/lib.rs
index 11524e3e7..cd49cadf8 100644
--- a/gpx-rs/src/lib.rs
+++ b/gpx-rs/src/lib.rs
@@ -1,5 +1,6 @@
 mod action;
 mod algorithm;
+mod buffer;
 mod engine;
 mod gpx;
 mod io;
@@ -7,3 +8,5 @@ mod selection;
 mod state;
 mod statistics;
 mod utils;
+
+pub use engine::*;
diff --git a/gpx-rs/src/selection.rs b/gpx-rs/src/selection.rs
index d37a56592..ef93e74f7 100644
--- a/gpx-rs/src/selection.rs
+++ b/gpx-rs/src/selection.rs
@@ -1,29 +1,34 @@
 use std::collections::HashSet;
 
-use uuid::Uuid;
+use crate::gpx::{FileId, TrackId, TrackSegmentId, WaypointId};
 
 #[derive(Debug)]
 pub struct FileSelection {
-    files: HashSet<Uuid>,
+    pub files: HashSet<FileId>,
 }
 
 #[derive(Debug)]
 pub struct TrackSelection {
-    file: Uuid,
-    trk: HashSet<Uuid>,
+    pub file: FileId,
+    pub trk: HashSet<TrackId>,
 }
 
 #[derive(Debug)]
 pub struct TrackSegmentSelection {
-    file: Uuid,
-    trk: Uuid,
-    trkseg: HashSet<Uuid>,
+    pub file: FileId,
+    pub trk: TrackId,
+    pub trkseg: HashSet<TrackSegmentId>,
+}
+
+#[derive(Debug)]
+pub struct WaypointsSelection {
+    pub file: FileId,
 }
 
 #[derive(Debug)]
 pub struct WaypointSelection {
-    file: Uuid,
-    wpt: HashSet<Uuid>,
+    pub file: FileId,
+    pub wpt: HashSet<WaypointId>,
 }
 
 #[derive(Debug, Default)]
@@ -33,6 +38,14 @@ pub enum Selection {
     File(FileSelection),
     Track(TrackSelection),
     TrackSegment(TrackSegmentSelection),
-    Waypoints,
+    Waypoints(WaypointsSelection),
     Waypoint(WaypointSelection),
 }
+
+impl Selection {
+    pub fn select(&mut self, id: FileId) {
+        let mut files = HashSet::default();
+        files.insert(id);
+        *self = Selection::File(FileSelection { files });
+    }
+}
diff --git a/gpx-rs/src/state/stack.rs b/gpx-rs/src/state/stack.rs
index 7f0bec870..e70c121d7 100644
--- a/gpx-rs/src/state/stack.rs
+++ b/gpx-rs/src/state/stack.rs
@@ -3,11 +3,9 @@ use std::{
     rc::Rc,
 };
 
-use uuid::Uuid;
+use crate::gpx::{File, FileId};
 
-use crate::gpx::GPXFile;
-
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub struct Stack {
     entries: Vec<StackEntry>,
     index: Option<usize>,
@@ -99,8 +97,8 @@ impl Stack {
         }
         let prev = prev.map_or_default(|i| self.get(i));
         let cur = cur.map_or_default(|i| self.get(i));
-        let prev_ids: HashSet<Uuid> = prev.map_or_default(|e| e.keys().copied().collect());
-        let cur_ids: HashSet<Uuid> = cur.map_or_default(|e| e.keys().copied().collect());
+        let prev_ids: HashSet<FileId> = prev.map_or_default(|e| e.keys().copied().collect());
+        let cur_ids: HashSet<FileId> = cur.map_or_default(|e| e.keys().copied().collect());
         let mut modified = vec![];
         for id in prev_ids.intersection(&cur_ids) {
             let before = prev.map_or_default(|e| e.get(id));
@@ -117,13 +115,13 @@ impl Stack {
     }
 }
 
-pub type StackEntry = HashMap<Uuid, Rc<GPXFile>>;
+pub type StackEntry = HashMap<FileId, Rc<File>>;
 
 #[derive(Debug, Default)]
 pub struct Diff {
-    pub added: Vec<Uuid>,
-    pub removed: Vec<Uuid>,
-    pub modified: Vec<Uuid>,
+    pub added: Vec<FileId>,
+    pub removed: Vec<FileId>,
+    pub modified: Vec<FileId>,
 }
 
 #[cfg(test)]
@@ -139,7 +137,7 @@ mod tests {
         assert!(stack.current().is_none());
 
         let diff = stack.create_and_push_next(|e| {
-            let file = Rc::new(GPXFile::default());
+            let file = Rc::new(File::default());
             e.insert(file.id, file);
             true
         });
diff --git a/gpx-rs/src/statistics/cache.rs b/gpx-rs/src/statistics/cache.rs
new file mode 100644
index 000000000..adfcb7078
--- /dev/null
+++ b/gpx-rs/src/statistics/cache.rs
@@ -0,0 +1,113 @@
+use std::{
+    collections::{HashMap, HashSet, hash_map::Entry},
+    rc::Rc,
+};
+
+use crate::{
+    gpx::{File, Track, TrackSegment, TrackSegmentRevisionId},
+    selection::Selection,
+    state::StackEntry,
+    statistics::Statistics,
+};
+
+#[derive(Debug, Default)]
+pub struct StatisticsCache {
+    map: HashMap<TrackSegmentRevisionId, Statistics>,
+}
+
+impl StatisticsCache {
+    pub fn update(&mut self, state: Option<&StackEntry>) {
+        let mut stale: HashSet<TrackSegmentRevisionId> = self.map.keys().copied().collect();
+        if let Some(state) = state {
+            for file in state.values() {
+                for trk in file.trk.iter() {
+                    for trkseg in trk.trkseg.iter() {
+                        match self.map.entry(trkseg.rev_id) {
+                            Entry::Occupied(_) => {
+                                stale.remove(&trkseg.rev_id);
+                            }
+                            Entry::Vacant(e) => {
+                                e.insert(Statistics::compute(trkseg));
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        for id in stale.iter() {
+            self.map.remove(id);
+        }
+    }
+
+    pub fn get<'a>(
+        &'a self,
+        state: Option<&StackEntry>,
+        selection: &Selection,
+    ) -> Vec<&'a Statistics> {
+        let mut stats = vec![];
+        if let Some(state) = state {
+            match selection {
+                Selection::Empty => (),
+                Selection::File(s) => {
+                    for id in s.files.iter() {
+                        if let Some(file) = state.get(id) {
+                            self.add_file_stats(file, &mut stats);
+                        }
+                    }
+                }
+                Selection::Track(s) => {
+                    if let Some(file) = state.get(&s.file) {
+                        for trk in file.trk.iter() {
+                            if s.trk.contains(&trk.id) {
+                                self.add_track_stats(trk, &mut stats);
+                            }
+                        }
+                    }
+                }
+                Selection::TrackSegment(s) => {
+                    if let Some(file) = state.get(&s.file) {
+                        for trk in file.trk.iter() {
+                            if s.trk == trk.id {
+                                for trkseg in trk.trkseg.iter() {
+                                    if s.trkseg.contains(&trkseg.id) {
+                                        self.add_segment_stats(trkseg, &mut stats);
+                                    }
+                                }
+                                break;
+                            }
+                        }
+                    }
+                }
+                Selection::Waypoints(s) => {
+                    if let Some(file) = state.get(&s.file) {
+                        self.add_file_stats(file, &mut stats);
+                    }
+                }
+                Selection::Waypoint(s) => {
+                    if let Some(file) = state.get(&s.file) {
+                        self.add_file_stats(file, &mut stats);
+                    }
+                }
+            }
+        }
+        stats
+    }
+
+    fn add_file_stats<'a>(&'a self, file: &Rc<File>, stats: &mut Vec<&'a Statistics>) {
+        for trk in file.trk.iter() {
+            self.add_track_stats(trk, stats);
+        }
+    }
+
+    fn add_track_stats<'a>(&'a self, trk: &Track, stats: &mut Vec<&'a Statistics>) {
+        for trkseg in trk.trkseg.iter() {
+            self.add_segment_stats(trkseg, stats);
+        }
+    }
+
+    fn add_segment_stats<'a>(&'a self, trkseg: &TrackSegment, stats: &mut Vec<&'a Statistics>) {
+        if let Some(s) = self.map.get(&trkseg.rev_id) {
+            stats.push(s);
+        }
+    }
+}
diff --git a/gpx-rs/src/statistics/mod.rs b/gpx-rs/src/statistics/mod.rs
index 0db599c42..0e9972d24 100644
--- a/gpx-rs/src/statistics/mod.rs
+++ b/gpx-rs/src/statistics/mod.rs
@@ -1,7 +1,7 @@
-mod buffer;
+mod cache;
 mod statistics;
 mod utils;
 
-pub use buffer::*;
+pub use cache::*;
 pub use statistics::*;
 pub use utils::*;
diff --git a/gpx-rs/src/utils.rs b/gpx-rs/src/utils.rs
index 7ad73f2a6..1fd5fe8a9 100644
--- a/gpx-rs/src/utils.rs
+++ b/gpx-rs/src/utils.rs
@@ -18,8 +18,15 @@ pub fn distance(p1: LngLat, p2: LngLat) -> f64 {
     EARTH_RADIUS * c
 }
 
+pub fn time_diff(a: &Option<i64>, b: &Option<i64>) -> Option<i32> {
+    match (a, b) {
+        (Some(t1), Some(t2)) => Some((t1 - t2) as i32),
+        _ => None,
+    }
+}
+
 /// Computes the speed for a given distance in kilometers and a time in milliseconds
-pub fn speed(distance: f64, time: i64) -> f64 {
+pub fn speed(distance: f64, time: i32) -> f64 {
     distance / (time as f64 / 3600_000.0)
 }
 
@@ -40,7 +47,7 @@ fn get_meters_per_longitude_degree(latitude: f64) -> f64 {
 // Calculates the point on the line segment defined by p1 and p2
 // that is closest to the third point, p3.
 // Uses simple planar geometry (ignores earth curvature).
-fn projected(p1: LngLat, p2: LngLat, coord3: LngLat) -> LngLat {
+fn projected(p1: LngLat, p2: LngLat, p3: LngLat) -> LngLat {
     // Convert to meters using approximate scaling
     let meters_per_longitude_degree = get_meters_per_longitude_degree(p1.lat);
 
@@ -48,8 +55,8 @@ fn projected(p1: LngLat, p2: LngLat, coord3: LngLat) -> LngLat {
     let y1 = p1.lat * METERS_PER_LATITUDE_DEGREE;
     let x2 = p2.lng * meters_per_longitude_degree;
     let y2 = p2.lat * METERS_PER_LATITUDE_DEGREE;
-    let x3 = coord3.lng * meters_per_longitude_degree;
-    let y3 = coord3.lat * METERS_PER_LATITUDE_DEGREE;
+    let x3 = p3.lng * meters_per_longitude_degree;
+    let y3 = p3.lat * METERS_PER_LATITUDE_DEGREE;
 
     let dx = x2 - x1;
     let dy = y2 - y1;
@@ -78,17 +85,20 @@ fn projected(p1: LngLat, p2: LngLat, coord3: LngLat) -> LngLat {
 /// Calculates the perpendicular distance in meters
 /// between a line segment (defined by p1 and p2) and a third point, p3.
 /// Uses simple planar geometry (ignores earth curvature).
-fn crossarc(p1: LngLat, p2: LngLat, p3: LngLat) -> f64 {
+fn crossarc_lnglat(p1: LngLat, p2: LngLat, p3: LngLat) -> f64 {
     // Convert to meters using approximate scaling
     let meters_per_longitude_degree = get_meters_per_longitude_degree(p1.lat);
+    crossarc(
+        p1.lng * meters_per_longitude_degree,
+        p1.lat * METERS_PER_LATITUDE_DEGREE,
+        p2.lng * meters_per_longitude_degree,
+        p2.lat * METERS_PER_LATITUDE_DEGREE,
+        p3.lng * meters_per_longitude_degree,
+        p3.lat * METERS_PER_LATITUDE_DEGREE,
+    )
+}
 
-    let x1 = p1.lng * meters_per_longitude_degree;
-    let y1 = p1.lat * METERS_PER_LATITUDE_DEGREE;
-    let x2 = p2.lng * meters_per_longitude_degree;
-    let y2 = p2.lat * METERS_PER_LATITUDE_DEGREE;
-    let x3 = p3.lng * meters_per_longitude_degree;
-    let y3 = p3.lat * METERS_PER_LATITUDE_DEGREE;
-
+pub fn crossarc(x1: f64, y1: f64, x2: f64, y2: f64, x3: f64, y3: f64) -> f64 {
     let dx = x2 - x1;
     let dy = y2 - y1;
     let segment_length_squared = dx * dx + dy * dy;