"""milestone_embeddings — a plan becomes findable by meaning (milestone 415)

Revision ID: 0102
Revises: 0101
Create Date: 2026-09-15

`search` covered notes, tasks and rules, and a milestone — the record a plan
lives in — could not be found at all. So "is there already a plan for this?"
had no tool, and a project whose roadmap was written as milestones had every
later plan opened as a new milestone beside the one that already described it.

The sibling of rule_embeddings (0089), for the reasons its model docstring and
note 3163 give. The vectors are DERIVED: nothing is backfilled here, the startup
backfill writes them.
"""
import sqlalchemy as sa
from alembic import op

revision = "0102"
down_revision = "0101"
branch_labels = None
depends_on = None

# Matches note_embeddings and rule_embeddings — bge-small-en-v1.5, 384-dim.
_EMBEDDING_DIM = 384


def upgrade() -> None:
    op.create_table(
        "milestone_embeddings",
        sa.Column(
            "milestone_id", sa.Integer(),
            sa.ForeignKey("milestones.id", ondelete="CASCADE"), primary_key=True,
        ),
        sa.Column("chunk_index", sa.Integer(), primary_key=True),
        sa.Column("chunk_text", sa.Text(), nullable=False),
        sa.Column("chunker_version", sa.Integer(), nullable=False),
        sa.Column(
            "updated_at", sa.DateTime(timezone=True), nullable=False,
            server_default=sa.text("now()"),
        ),
    )
    # Raw DDL for the vector column, as 0067 and 0089 do: the type comes from
    # the pgvector extension, not SQLAlchemy's type system.
    op.execute(
        f"ALTER TABLE milestone_embeddings ADD COLUMN embedding vector({_EMBEDDING_DIM}) NOT NULL"
    )
    op.execute(
        """
        CREATE INDEX ix_milestone_embeddings_embedding_hnsw
            ON milestone_embeddings
         USING hnsw (embedding vector_cosine_ops)
        """
    )


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS ix_milestone_embeddings_embedding_hnsw")
    op.drop_table("milestone_embeddings")