1 files changed, 89 insertions, 0 deletions
diff --git a/src/history.rs b/src/history.rs
new file mode 100644
index 0000000..25a9555
--- /dev/null
+++ b/src/history.rs
@@ -0,0 +1,89 @@
+use std::{fs::File, io::{self, Read, Seek, Write}};
+
+use serde::{Deserialize, Serialize};
+
+use crate::text_diff::TextChange;
+
+#[derive(Serialize, Deserialize, Debug)]
+pub struct FileHistory {
+    cursor: usize,
+    changes: Vec<FileChange>,
+}
+
+impl FileHistory {
+    pub fn from_file(file: &mut File) -> Result<FileHistory, ()> {
+        let mut buffer = Vec::new();
+        file.read_to_end(&mut buffer)
+            .expect("Could not read file history,");
+
+        let file_history = serde_json::from_slice::<FileHistory>(&buffer);
+        Ok(file_history.expect("Corrupted file history."))
+    }
+
+    pub fn cursor(&self) -> usize {
+        self.cursor
+    }
+
+    pub fn file_is_deleted(&self) -> bool {
+        match self.changes.last() {
+            Some(change) => match change {
+                FileChange::Deleted => true,
+                FileChange::Updated(_) => false,
+            },
+            None => false,
+        }
+    }
+
+    pub fn get_content(&self) -> String {
+        let mut buffer = String::new();
+        for file_change in self.changes.iter().take(self.cursor) {
+            if let FileChange::Updated(ref updated) = file_change {
+                for change in updated.iter() {
+                    change.apply(&mut buffer)
+                }
+            } else {
+                buffer = String::new();
+            }
+        }
+        buffer
+    }
+
+    pub fn write_to_file(&self, file: &mut File) -> io::Result<()> {
+        let encoded: Vec<u8> = serde_json::to_vec(self).unwrap();
+        file.rewind()?;
+        file.set_len(0)?;
+        file.write_all(encoded.as_ref())?;
+        Ok(())
+    }
+
+    pub fn set_cursor(&mut self, new_cursor: usize) {
+        if new_cursor < self.changes.len() {
+            self.cursor = new_cursor;
+        } else {
+            panic!(
+                "Out-of-bounds cursor for file history: {}, can be at most {}",
+                new_cursor,
+                self.changes.len()
+            );
+        }
+    }
+
+    pub fn add_change(&mut self, change: FileChange) {
+        self.changes.push(change);
+    }
+}
+
+impl Default for FileHistory {
+    fn default() -> Self {
+        Self {
+            cursor: 0,
+            changes: Vec::new(),
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+pub enum FileChange {
+    Updated(Vec<TextChange>),
+    Deleted,
+}