"""Track which articles a learner has opened, for "recently viewed".

Revision ID: w5c6d7e8f9a0
Revises: v4b5c6d7e8f9
"""
from alembic import op

revision = "w5c6d7e8f9a0"
down_revision = "v4b5c6d7e8f9"
branch_labels = None
depends_on = None


def upgrade():
    op.execute("""
    CREATE TABLE IF NOT EXISTS article_views (
        id SERIAL PRIMARY KEY,
        user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
        article_id INTEGER NOT NULL REFERENCES articles(id) ON DELETE CASCADE,
        viewed_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
        CONSTRAINT uq_article_view UNIQUE (user_id, article_id)
    )
    """)
    op.execute("CREATE INDEX IF NOT EXISTS ix_article_views_user ON article_views(user_id, viewed_at DESC)")


def downgrade():
    op.execute("DROP TABLE IF EXISTS article_views")