import sqlite3


def migrate(conn: sqlite3.Connection):
    _ = conn.execute("""
        CREATE TABLE IF NOT EXISTS posts (
            id         INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id    TEXT NOT NULL,
            service    TEXT NOT NULL,
            identifier TEXT NOT NULL,
            parent_id  INTEGER NULL REFERENCES posts(id) ON DELETE SET NULL,
            root_id    INTEGER NULL REFERENCES posts(id) ON DELETE SET NULL
        );
    """)
    _ = conn.execute("""
        CREATE TABLE IF NOT EXISTS mappings (
            original_post_id INTEGER NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
            mapped_post_id   INTEGER NOT NULL
        );
    """)
    pass