"""drop notes.title and note_revisions.title — a note's name is its first line

Revision ID: 0026
Revises: 0025
Create Date: 2026-08-22

A note's name is its first non-empty body line, carried by `display_title`.

`notes.search_vector` is a stored generated column over `title` (0005, weight A), and
Postgres won't drop a column a generated one depends on. So it is recreated over
`display_title`, keeping the name ranked above the body. That recomputes every row
and rebuilds the GIN index, which takes a while on a large table.

`display_title` was already derived from the title, so every note keeps its name.
"""
from alembic import op
import sqlalchemy as sa

revision = "0026"
down_revision = "0025"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # Order matters: the generated column depends on `title`, so it goes first.
    op.execute("DROP INDEX IF EXISTS ix_notes_search")
    op.execute("ALTER TABLE notes DROP COLUMN IF EXISTS search_vector")

    op.drop_column("notes", "title")
    op.drop_column("note_revisions", "title")

    op.execute(
        """
        ALTER TABLE notes ADD COLUMN search_vector tsvector
        GENERATED ALWAYS AS (
            setweight(to_tsvector('english', coalesce(display_title, '')), 'A') ||
            setweight(to_tsvector('english', coalesce(body, '')), 'B')
        ) STORED
        """
    )
    op.execute("CREATE INDEX ix_notes_search ON notes USING GIN (search_vector)")


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS ix_notes_search")
    op.execute("ALTER TABLE notes DROP COLUMN IF EXISTS search_vector")

    # Comes back empty. The text is not gone — it is the first line of every body —
    # but which notes once had an explicit title is not recorded anywhere.
    op.add_column("notes", sa.Column("title", sa.Text(), nullable=True))
    op.add_column("note_revisions", sa.Column("title", sa.Text(), nullable=True))

    op.execute(
        """
        ALTER TABLE notes ADD COLUMN search_vector tsvector
        GENERATED ALWAYS AS (
            setweight(to_tsvector('english', coalesce(title, '')), 'A') ||
            setweight(to_tsvector('english', coalesce(body, '')), 'B')
        ) STORED
        """
    )
    op.execute("CREATE INDEX ix_notes_search ON notes USING GIN (search_vector)")