MODULE SQLiteBackup;
(* Online backup API:
   backup_init/step/finish/remaining/pagecount. *)

FROM SYSTEM IMPORT ADDRESS;
FROM SQLite IMPORT
  SQLiteOk, SQLiteRow, SQLiteDone,
  sqlite3_open, sqlite3_close, sqlite3_exec,
  sqlite3_prepare_v2, sqlite3_step, sqlite3_column_int,
  sqlite3_finalize,
  sqlite3_backup_init, sqlite3_backup_step, sqlite3_backup_finish,
  sqlite3_backup_remaining, sqlite3_backup_pagecount,
  sqlite3_free;

VAR
  ExitCode : INTEGER;
  src, dst, dst2, bk : ADDRESS;
  rc, pages : INTEGER;
  ok : BOOLEAN;

PROCEDURE ExecSQL (h : ADDRESS; sql : ARRAY OF CHAR) : BOOLEAN;
VAR
  errmsg : ADDRESS;
  good : BOOLEAN;
BEGIN
  errmsg := NIL;
  good := sqlite3_exec(h, sql, NIL, NIL, errmsg) = SQLiteOk;
  IF errmsg # NIL THEN
    sqlite3_free(errmsg)
  END;
  RETURN good
END ExecSQL;

PROCEDURE CountRows (h : ADDRESS; want : INTEGER) : BOOLEAN;
VAR
  s : ADDRESS;
  code, got : INTEGER;
  good : BOOLEAN;
BEGIN
  s := NIL; got := -1; good := FALSE;
  code := sqlite3_prepare_v2(h, "SELECT count(*) FROM t;",
                             -1, s, NIL);
  IF (code = SQLiteOk) AND (s # NIL) THEN
    IF sqlite3_step(s) = SQLiteRow THEN
      got := sqlite3_column_int(s, 0);
      IF sqlite3_step(s) = SQLiteDone THEN good := TRUE END
    END;
    IF sqlite3_finalize(s) # SQLiteOk THEN good := FALSE END
  END;
  RETURN good AND (got = want)
END CountRows;

BEGIN
  ExitCode := 1;
  src := NIL; dst := NIL; dst2 := NIL; bk := NIL;
  ok := FALSE;

  IF (sqlite3_open(":memory:", src) = SQLiteOk) AND (src # NIL)
     AND (sqlite3_open(":memory:", dst) = SQLiteOk) AND (dst # NIL)
     AND (sqlite3_open(":memory:", dst2) = SQLiteOk) AND (dst2 # NIL) THEN
    ok := ExecSQL(src, "CREATE TABLE t(x INTEGER);")
          AND ExecSQL(src, "INSERT INTO t VALUES(1);")
          AND ExecSQL(src, "INSERT INTO t VALUES(2);")
  END;

  (* Full backup into another in-memory database. *)
  IF ok THEN
    bk := sqlite3_backup_init(dst, "main", src, "main");
    ok := bk # NIL;
    IF ok THEN
      ok := sqlite3_backup_step(bk, -1) = SQLiteDone
    END;
    IF ok THEN
      pages := sqlite3_backup_pagecount(bk);
      ok := (pages > 0) AND (sqlite3_backup_remaining(bk) = 0)
    END;
    IF sqlite3_backup_finish(bk) # SQLiteOk THEN ok := FALSE END;
    bk := NIL
  END;
  IF ok THEN ok := CountRows(dst, 2) END;

  (* Incremental backup, one page at a time. *)
  IF ok THEN
    bk := sqlite3_backup_init(dst2, "main", src, "main");
    ok := bk # NIL;
    IF ok THEN
      rc := sqlite3_backup_step(bk, 1);
      WHILE (rc = SQLiteOk) DO
        rc := sqlite3_backup_step(bk, 1)
      END;
      ok := (rc = SQLiteDone) AND (sqlite3_backup_remaining(bk) = 0);
      IF sqlite3_backup_finish(bk) # SQLiteOk THEN ok := FALSE END;
      bk := NIL
    END
  END;
  IF ok THEN ok := CountRows(dst2, 2) END;

  IF bk # NIL THEN
    IF sqlite3_backup_finish(bk) # SQLiteOk THEN ok := FALSE END
  END;
  IF src # NIL THEN
    IF sqlite3_close(src) # SQLiteOk THEN ok := FALSE END
  END;
  IF dst # NIL THEN
    IF sqlite3_close(dst) # SQLiteOk THEN ok := FALSE END
  END;
  IF dst2 # NIL THEN
    IF sqlite3_close(dst2) # SQLiteOk THEN ok := FALSE END
  END;
  IF ok THEN ExitCode := 42 END
END SQLiteBackup.