"""decouple musicians: standalone table, join table for references, fk for learned_from

Revision ID: 2bd4f3ff0ccc
Revises: ea4bb85f9908
Create Date: 2026-06-09
"""
from alembic import op
import sqlalchemy as sa

revision = "2bd4f3ff0ccc"
down_revision = "ea4bb85f9908"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # 1. Drop the old musicians table (string PK, tied to references)
    op.drop_table("musicians")

    # 2. Create standalone musicians table with integer PK
    op.create_table(
        "musicians",
        sa.Column("id",   sa.Integer(), primary_key=True, autoincrement=True, nullable=False),
        sa.Column("name", sa.String(),  nullable=False),
    )

    # 3. Create reference_musicians join table (many-to-many)
    op.create_table(
        "reference_musicians",
        sa.Column("reference_id", sa.Integer(),
                  sa.ForeignKey("references.id", ondelete="CASCADE"),
                  nullable=False),
        sa.Column("musician_id",  sa.Integer(),
                  sa.ForeignKey("musicians.id",  ondelete="CASCADE"),
                  nullable=False),
        sa.PrimaryKeyConstraint("reference_id", "musician_id"),
    )

    # 4. Add learned_from_id FK to banjo and fiddle (keep old learned_from text
    #    column for the downgrade path, then drop it)
    op.add_column("banjo",  sa.Column("learned_from_id", sa.Integer(),
                                      sa.ForeignKey("musicians.id", ondelete="SET NULL"),
                                      nullable=True))
    op.add_column("fiddle", sa.Column("learned_from_id", sa.Integer(),
                                      sa.ForeignKey("musicians.id", ondelete="SET NULL"),
                                      nullable=True))
    op.drop_column("banjo",  "learned_from")
    op.drop_column("fiddle", "learned_from")


def downgrade() -> None:
    op.add_column("banjo",  sa.Column("learned_from", sa.String(), nullable=True))
    op.add_column("fiddle", sa.Column("learned_from", sa.String(), nullable=True))
    op.drop_column("banjo",  "learned_from_id")
    op.drop_column("fiddle", "learned_from_id")
    op.drop_table("reference_musicians")
    op.drop_table("musicians")
    # Recreate original musicians table
    op.create_table(
        "musicians",
        sa.Column("name",         sa.String(),  primary_key=True, nullable=False),
        sa.Column("reference_id", sa.Integer(),
                  sa.ForeignKey("references.id", ondelete="CASCADE"),
                  nullable=True),
    )