"""Used to create the SQL dump which mimics the import of cave and expo
data from files.

Mimic the sqlite3 console shell's .dump command
Author: Paul Kippes <kippesp@gmail.com>

Every identifier in sql is quoted based on a comment in sqlite
documentation "SQLite adds new keywords from time to time when it
takes on new features. So to prevent your code from being broken by
future enhancements, you should normally quote any identifier that
is an English language word, even if you do not have to."
"""

def _iterdump(connection):
    """
    Returns an iterator to the dump of the database in an SQL text format.
    Used to produce an SQL dump of the database.  Useful to save an in-memory
    database for later restoration.  This function should not be called
    directly but instead called from the Connection method, iterdump().
    """

    cu = connection.cursor()
    yield('BEGIN TRANSACTION;')

    # sqlite_master table contains the SQL CREATE statements for the database.
    q = """
        SELECT "name", "type", "sql"
        FROM "sqlite_master"
            WHERE "sql" NOT NULL AND
            "type" == 'table'
            ORDER BY "name"
        """
    schema_res = cu.execute(q)
    for table_name, type, sql in schema_res.fetchall():
        if table_name == 'sqlite_sequence':
            yield('DELETE FROM "sqlite_sequence";')
        elif table_name == 'sqlite_stat1':
            yield('ANALYZE "sqlite_master";')
        elif table_name.startswith('sqlite_'):
            continue
        # NOTE: Virtual table support not implemented
        #elif sql.startswith('CREATE VIRTUAL TABLE'):
        #    qtable = table_name.replace("'", "''")
        #    yield("INSERT INTO sqlite_master(type,name,tbl_name,rootpage,sql)"\
        #        "VALUES('table','{0}','{0}',0,'{1}');".format(
        #        qtable,
        #        sql.replace("''")))
        else:
            yield(f'{sql};')

        # Build the insert statement for each row of the current table
        table_name_ident = table_name.replace('"', '""')
        res = cu.execute(f'PRAGMA table_info("{table_name_ident}")')
        column_names = [str(table_info[1]) for table_info in res.fetchall()]
        q = """SELECT 'INSERT INTO "{0}" VALUES({1})' FROM "{0}";""".format(
            table_name_ident,
            ",".join("""'||quote("{0}")||'""".format(col.replace('"', '""')) for col in column_names))
        query_res = cu.execute(q)
        for row in query_res:
            yield(row[0]) # '{0}'.format(row[0]) had unicode errors

    # Now when the type is 'index', 'trigger', or 'view'
    q = """
        SELECT "name", "type", "sql"
        FROM "sqlite_master"
            WHERE "sql" NOT NULL AND
            "type" IN ('index', 'trigger', 'view')
        """
    schema_res = cu.execute(q)
    for name, type, sql in schema_res.fetchall():
        yield(f'{sql};')

    yield('COMMIT;')