1 files changed, 79 insertions, 0 deletions
diff --git a/lib/sql/hashs.ml b/lib/sql/hashs.ml
new file mode 100644
index 0000000..af1f092
--- /dev/null
+++ b/lib/sql/hashs.ml
@@ -0,0 +1,79 @@
+(** 
+    This module store the hash of the indexes ([extern_key]) for each table in
+    order to update the file if the configuration changed.
+
+    The hashes are stored in a table named [hashes] and are evaluated just
+    before inserting the values. 
+*)
+
+open StdLabels
+module Table = ImportDataTypes.Table
+
+let ( let* ) = Result.bind
+
+let create_table : 'a T.t -> unit T.result =
+ fun db ->
+  Sqlite3.exec db
+    "CREATE TABLE IF NOT EXISTS 'hashes' ('table' TEXT, 'hash' INTEGER, \
+     PRIMARY KEY ('table'))"
+  |> T.to_result
+
+let evaluate : ImportAnalyser.Dependency.t -> int =
+ fun table ->
+  (* Extract all the references to this table *)
+  let keys =
+    List.map (ImportAnalyser.Dependency.keys table)
+      ~f:(fun ImportAnalyser.Dependency.{ name; columns; expression } ->
+        ignore columns;
+        (name, expression))
+  in
+  Hashtbl.hash keys
+
+let insert : 'a T.t -> ImportAnalyser.Dependency.t -> unit T.result =
+ fun db table ->
+  let source = ImportAnalyser.Dependency.table table in
+  let table_name = Table.name source in
+
+  let hash = evaluate table in
+
+  let query =
+    String.concat ~sep:""
+      [
+        "INSERT INTO 'hashes' ('table', 'hash') VALUES ('";
+        table_name;
+        "', :hash) ON CONFLICT(hashes.'table') DO UPDATE SET 'hash' = :hash";
+      ]
+  in
+  let* statement =
+    try Ok (Sqlite3.prepare db query) with
+    | e -> Error e
+  in
+
+  let* _ = T.begin_transaction db in
+  let sql_data = Sqlite3.Data.INT (Int64.of_int hash) in
+
+  let* _ = Sqlite3.bind_name statement ":hash" sql_data |> T.to_result in
+  let* _ = T.to_result (Sqlite3.step statement) in
+  T.commit db
+
+let query : 'a T.t -> ImportDataTypes.Table.t -> int option T.result =
+ fun db table ->
+  let table_name = Table.name table in
+  let query =
+    String.concat ~sep:""
+      [ "SELECT hash FROM 'hashes' WHERE hashes.'table' = '"; table_name; "'" ]
+  in
+
+  let* stmt =
+    try Ok (Sqlite3.prepare db query) with
+    | e -> Error e
+  in
+  let state, res =
+    Sqlite3.fold stmt ~init:None ~f:(fun _ d ->
+        Some (T.to_datatype (Array.get d 0)))
+  in
+
+  let* _ = T.to_result state in
+  match res with
+  | Some (ImportCSV.DataType.Integer i) -> Ok (Some i)
+  | _ -> Ok None