1 files changed, 173 insertions, 0 deletions
diff --git a/src/sync.rs b/src/sync.rs
new file mode 100644
index 0000000..3911d55
--- /dev/null
+++ b/src/sync.rs
@@ -0,0 +1,173 @@
+use crate::{
+    db, deck,
+    model::{DbEntry, Line, Question},
+};
+use anyhow::Result;
+use rusqlite::Connection;
+use std::collections::HashSet;
+
+pub fn run(conn: &mut Connection, deck_path: &str) -> Result<()> {
+    let db_entries = db::all(conn)?;
+    let lines = deck::read(deck_path)?;
+    let Diff {
+        new,
+        deleted,
+        undeleted,
+    } = diff(db_entries, lines);
+
+    db::insert(conn, &new)?;
+    db::delete(conn, &deleted)?;
+    db::undelete(conn, &undeleted)?;
+
+    Ok(())
+}
+
+struct Diff {
+    pub new: Vec<Question>,
+    pub deleted: Vec<Question>,
+    pub undeleted: Vec<Question>,
+}
+
+fn diff(db_entries: Vec<DbEntry>, lines: Vec<Line>) -> Diff {
+    let mut file_questions: HashSet<Question> = HashSet::new();
+    let mut db_questions_not_deleted: HashSet<Question> = HashSet::new();
+    let mut db_questions_deleted: HashSet<Question> = HashSet::new();
+
+    for Line { part_1, part_2 } in lines {
+        for question in part_1.clone() {
+            let mut responses = part_2.clone();
+            responses.sort();
+            file_questions.insert(Question {
+                question,
+                responses,
+            });
+        }
+        for question in part_2 {
+            let mut responses = part_1.clone();
+            responses.sort();
+            file_questions.insert(Question {
+                question,
+                responses,
+            });
+        }
+    }
+
+    for DbEntry {
+        question,
+        mut responses,
+        deleted,
+    } in db_entries
+    {
+        responses.sort();
+        if deleted.is_some() {
+            db_questions_deleted.insert(Question {
+                question,
+                responses,
+            });
+        } else {
+            db_questions_not_deleted.insert(Question {
+                question,
+                responses,
+            });
+        }
+    }
+
+    let new = file_questions
+        .difference(&db_questions_not_deleted)
+        .cloned()
+        .collect::<HashSet<Question>>()
+        .difference(&db_questions_deleted)
+        .cloned()
+        .collect();
+
+    let deleted = db_questions_not_deleted
+        .difference(&file_questions)
+        .cloned()
+        .collect();
+
+    let undeleted = file_questions
+        .intersection(&db_questions_deleted)
+        .cloned()
+        .collect();
+
+    Diff {
+        new,
+        deleted,
+        undeleted,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+
+    #[test]
+    fn sync() {
+        let db_entries = vec![
+            DbEntry {
+                question: "A".to_string(),
+                responses: vec!["A".to_string()],
+                deleted: None,
+            },
+            DbEntry {
+                question: "B".to_string(),
+                responses: vec!["B".to_string()],
+                deleted: None,
+            },
+            DbEntry {
+                question: "C".to_string(),
+                responses: vec!["C".to_string()],
+                deleted: Some(0),
+            },
+            DbEntry {
+                question: "D".to_string(),
+                responses: vec!["D".to_string()],
+                deleted: Some(0),
+            },
+        ];
+
+        let lines = vec![
+            Line {
+                part_1: vec!["A".to_string()],
+                part_2: vec!["A".to_string()],
+            },
+            Line {
+                part_1: vec!["C".to_string()],
+                part_2: vec!["C".to_string()],
+            },
+            Line {
+                part_1: vec!["E".to_string()],
+                part_2: vec!["E".to_string()],
+            },
+        ];
+
+        let Res {
+            new,
+            deleted,
+            undeleted,
+        } = sync(db_entries, lines);
+
+        assert_eq!(
+            new,
+            vec!(Question {
+                question: "E".to_string(),
+                responses: vec!("E".to_string())
+            })
+        );
+        assert_eq!(
+            deleted,
+            vec!(Question {
+                question: "B".to_string(),
+                responses: vec!("B".to_string())
+            })
+        );
+        assert_eq!(
+            undeleted,
+            vec!(Question {
+                question: "C".to_string(),
+                responses: vec!("C".to_string())
+            })
+        );
+    }
+}