1 files changed, 74 insertions, 0 deletions
diff --git a/lib/sql/header.ml b/lib/sql/header.ml
new file mode 100644
index 0000000..3cac5fb
--- /dev/null
+++ b/lib/sql/header.ml
@@ -0,0 +1,74 @@
+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 'header' ('table' TEXT, 'column' INTEGER, \
+     'label', PRIMARY KEY ('table', 'column'))"
+  |> T.to_result
+
+let insert_header :
+    'a T.t ->
+    ImportDataTypes.Table.t ->
+    (int * ImportCSV.DataType.t) array ->
+    unit T.result =
+ fun db table values ->
+  let table_name = Table.name table in
+
+  let query =
+    String.concat ~sep:""
+      [
+        "INSERT INTO 'header' ('table', 'column', 'label') VALUES ('";
+        table_name;
+        "', :column, :label) ON CONFLICT(header.'table', header.'column') DO \
+         UPDATE SET 'label' = :label";
+      ]
+  in
+
+  let statement = Sqlite3.prepare db query in
+
+  let* _ = T.begin_transaction db in
+  let* _ =
+    Array.fold_left values ~init:(Ok ()) ~f:(fun acc (column, value) ->
+        let* _ = acc in
+        let sql_data = T.of_datatype value in
+        let* _ = Sqlite3.bind_name statement ":label" sql_data |> T.to_result in
+
+        let* _ =
+          Sqlite3.bind_name statement ":column"
+            (Sqlite3.Data.INT (Int64.of_int column))
+          |> T.to_result
+        in
+        let* _ = T.to_result (Sqlite3.step statement) in
+        T.reset statement)
+  in
+  T.commit db
+
+let query_headers :
+    'a T.t -> ImportDataTypes.Table.t -> ImportCSV.DataType.t array T.result =
+ fun db table ->
+  let table_name = Table.name table in
+  let query =
+    String.concat ~sep:""
+      [
+        "SELECT label FROM 'header' WHERE header.'table' = '";
+        table_name;
+        "' ORDER BY column DESC";
+      ]
+  in
+
+  let* stmt =
+    try Ok (Sqlite3.prepare db query) with
+    | e -> Error e
+  in
+  let state, res =
+    Sqlite3.fold stmt ~init:[] ~f:(fun acc d ->
+        let value = T.to_datatype (Array.get d 0) in
+        value :: acc)
+  in
+
+  let* _ = T.to_result state in
+  Ok (Array.of_list res)