reorganize

gpx-rs/src/engine/state/mod.rs

@@ -0,0 +1,3 @@
+mod stack;
+
+pub use stack::*;

gpx-rs/src/engine/state/stack.rs

@@ -0,0 +1,158 @@
+use std::{
+    collections::{HashMap, HashSet},
+    rc::Rc,
+};
+
+use crate::{File, FileId};
+
+#[derive(Debug, Default)]
+pub struct Stack {
+    entries: Vec<StackEntry>,
+    index: Option<usize>,
+}
+
+impl Stack {
+    pub fn current(&self) -> Option<&StackEntry> {
+        self.index.map_or_default(|i| self.get(i))
+    }
+
+    pub fn create_and_push_next<F>(&mut self, f: F) -> Option<Diff>
+    where
+        F: FnOnce(&mut StackEntry) -> bool,
+    {
+        self.record_diff(|stack| {
+            let mut next = stack.current().map_or_default(|c| c.clone());
+            if f(&mut next) {
+                stack.push(next);
+            }
+        })
+    }
+
+    pub fn undo(&mut self) -> Option<Diff> {
+        self.record_diff(|stack| {
+            if let Some(i) = stack.index {
+                if i == 0 {
+                    stack.index = None;
+                } else {
+                    stack.index = Some(i - 1);
+                }
+            }
+        })
+    }
+
+    pub fn redo(&mut self) -> Option<Diff> {
+        self.record_diff(|stack| match stack.index {
+            Some(i) => {
+                if i + 1 < stack.entries.len() {
+                    stack.index = Some(i + 1);
+                }
+            }
+            None => {
+                if !stack.entries.is_empty() {
+                    stack.index = Some(0);
+                }
+            }
+        })
+    }
+
+    pub fn can_undo(&self) -> bool {
+        self.index.is_some()
+    }
+
+    pub fn can_redo(&self) -> bool {
+        match self.index {
+            Some(i) => i + 1 < self.entries.len(),
+            None => !self.entries.is_empty(),
+        }
+    }
+
+    fn get(&self, index: usize) -> Option<&StackEntry> {
+        if index < self.entries.len() {
+            Some(&self.entries[index])
+        } else {
+            None
+        }
+    }
+
+    fn push(&mut self, entry: StackEntry) {
+        if let Some(i) = self.index {
+            if i + 1 < self.entries.len() {
+                self.entries.truncate(i + 1);
+            }
+        }
+
+        self.entries.push(entry);
+        self.index = Some(self.entries.len() - 1);
+    }
+
+    fn record_diff<F>(&mut self, f: F) -> Option<Diff>
+    where
+        F: FnOnce(&mut Self),
+    {
+        let prev = self.index;
+        f(self);
+        let cur = self.index;
+        if prev == cur {
+            return None;
+        }
+        let prev = prev.map_or_default(|i| self.get(i));
+        let cur = cur.map_or_default(|i| self.get(i));
+        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));
+            let after = cur.map_or_default(|e| e.get(id));
+            if before != after {
+                modified.push(*id);
+            }
+        }
+        Some(Diff {
+            added: cur_ids.difference(&prev_ids).copied().collect(),
+            removed: prev_ids.difference(&cur_ids).copied().collect(),
+            modified,
+        })
+    }
+}
+
+pub type StackEntry = HashMap<FileId, Rc<File>>;
+
+#[derive(Debug, Default)]
+pub struct Diff {
+    pub added: Vec<FileId>,
+    pub removed: Vec<FileId>,
+    pub modified: Vec<FileId>,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_new_file() {
+        let mut stack = Stack::default();
+
+        assert!(!stack.can_undo());
+        assert!(!stack.can_redo());
+        assert!(stack.current().is_none());
+
+        let diff = stack.create_and_push_next(|e| {
+            let file = Rc::new(File::default());
+            e.insert(file.id, file);
+            true
+        });
+
+        assert!(stack.can_undo());
+        assert!(!stack.can_redo());
+        assert!(stack.current().is_some());
+
+        assert!(diff.is_some());
+
+        let diff = diff.unwrap();
+        assert_eq!(diff.added.len(), 1);
+        assert!(diff.removed.is_empty());
+        assert!(diff.modified.is_empty());
+    }
+
+    // TODO more tests
+}