"""full-text relevance search on video titles

Revision ID: 0031_title_fts
Revises: 0030_search_finds
Create Date: 2026-06-30

Adds a PostgreSQL full-text search index over video titles so the feed search box can rank by
relevance (a YouTube-like "fuzzy" search: word-order-independent, multi-word AND, prefix on the
word being typed) instead of a whole-phrase substring match.

A custom text-search configuration `unaccent_simple` = the `simple` config (no stemming, no
stopwords — right for a multilingual HU/EN/DE catalog) plus the `unaccent` dictionary, so the
search stays accent-insensitive ("tiesto" matches "Tiësto"). A GIN expression index on
`to_tsvector('public.unaccent_simple', coalesce(title,''))` makes the @@ match fast; the feed
query uses the exact same expression so the planner picks the index. `unaccent` is already
enabled (migration 0029). The config-based 2-arg to_tsvector is IMMUTABLE, so it's index-safe.
"""
from typing import Sequence, Union

from alembic import op

revision: str = "0031_title_fts"
down_revision: Union[str, None] = "0030_search_finds"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.execute(
        "CREATE TEXT SEARCH CONFIGURATION public.unaccent_simple (COPY = pg_catalog.simple)"
    )
    op.execute(
        """
        ALTER TEXT SEARCH CONFIGURATION public.unaccent_simple
        ALTER MAPPING FOR asciiword, asciihword, hword_asciipart, word, hword, hword_part
        WITH unaccent, simple
        """
    )
    op.execute(
        """
        CREATE INDEX ix_videos_title_fts ON videos
        USING gin (to_tsvector('public.unaccent_simple', coalesce(title, '')))
        """
    )


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS ix_videos_title_fts")
    op.execute("DROP TEXT SEARCH CONFIGURATION IF EXISTS public.unaccent_simple")
