UPDATE: Adds web app (#79)

Things missing:

* Browse mode
* Front end tests
* Storybook

base/src/user_model/history.rs

@@ -0,0 +1,164 @@
+use std::collections::HashMap;
+
+use bitcode::{Decode, Encode};
+
+use crate::types::{Cell, Col, Row, Style};
+
+#[derive(Clone, Encode, Decode)]
+pub(crate) struct RowData {
+    pub(crate) row: Option<Row>,
+    pub(crate) data: HashMap<i32, Cell>,
+}
+
+#[derive(Clone, Encode, Decode)]
+pub(crate) struct ColumnData {
+    pub(crate) column: Option<Col>,
+    pub(crate) data: HashMap<i32, Cell>,
+}
+
+#[derive(Clone, Encode, Decode)]
+pub(crate) enum Diff {
+    // Cell diffs
+    SetCellValue {
+        sheet: u32,
+        row: i32,
+        column: i32,
+        new_value: String,
+        old_value: Box<Option<Cell>>,
+    },
+    CellClearContents {
+        sheet: u32,
+        row: i32,
+        column: i32,
+        old_value: Box<Option<Cell>>,
+    },
+    CellClearAll {
+        sheet: u32,
+        row: i32,
+        column: i32,
+        old_value: Box<Option<Cell>>,
+        old_style: Box<Style>,
+    },
+    SetCellStyle {
+        sheet: u32,
+        row: i32,
+        column: i32,
+        old_value: Box<Style>,
+        new_value: Box<Style>,
+    },
+    // Column and Row diffs
+    SetColumnWidth {
+        sheet: u32,
+        column: i32,
+        new_value: f64,
+        old_value: f64,
+    },
+    SetRowHeight {
+        sheet: u32,
+        row: i32,
+        new_value: f64,
+        old_value: f64,
+    },
+    InsertRow {
+        sheet: u32,
+        row: i32,
+    },
+    DeleteRow {
+        sheet: u32,
+        row: i32,
+        old_data: Box<RowData>,
+    },
+    InsertColumn {
+        sheet: u32,
+        column: i32,
+    },
+    DeleteColumn {
+        sheet: u32,
+        column: i32,
+        old_data: Box<ColumnData>,
+    },
+    SetFrozenRowsCount {
+        sheet: u32,
+        new_value: i32,
+        old_value: i32,
+    },
+    SetFrozenColumnsCount {
+        sheet: u32,
+        new_value: i32,
+        old_value: i32,
+    },
+    DeleteSheet {
+        sheet: u32,
+    },
+    NewSheet {
+        index: u32,
+        name: String,
+    },
+    RenameSheet {
+        index: u32,
+        old_value: String,
+        new_value: String,
+    },
+    SetSheetColor {
+        index: u32,
+        old_value: String,
+        new_value: String,
+    },
+    SetShowGridLines {
+        sheet: u32,
+        old_value: bool,
+        new_value: bool,
+    }, // FIXME: we are missing SetViewDiffs
+}
+
+pub(crate) type DiffList = Vec<Diff>;
+
+#[derive(Default)]
+pub(crate) struct History {
+    pub(crate) undo_stack: Vec<DiffList>,
+    pub(crate) redo_stack: Vec<DiffList>,
+}
+
+impl History {
+    pub fn push(&mut self, diff_list: DiffList) {
+        self.undo_stack.push(diff_list);
+        self.redo_stack = vec![];
+    }
+
+    pub fn undo(&mut self) -> Option<Vec<Diff>> {
+        match self.undo_stack.pop() {
+            Some(diff_list) => {
+                self.redo_stack.push(diff_list.clone());
+                Some(diff_list)
+            }
+            None => None,
+        }
+    }
+
+    pub fn redo(&mut self) -> Option<Vec<Diff>> {
+        match self.redo_stack.pop() {
+            Some(diff_list) => {
+                self.undo_stack.push(diff_list.clone());
+                Some(diff_list)
+            }
+            None => None,
+        }
+    }
+
+    pub fn clear(&mut self) {
+        self.redo_stack = vec![];
+        self.undo_stack = vec![];
+    }
+}
+
+#[derive(Clone, Encode, Decode)]
+pub enum DiffType {
+    Undo,
+    Redo,
+}
+
+#[derive(Clone, Encode, Decode)]
+pub struct QueueDiffs {
+    pub r#type: DiffType,
+    pub list: DiffList,
+}