"""add learnable_languages table

Revision ID: 0004
Revises: 0003
Create Date: 2026-03-27

"""
from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op
from sqlalchemy.dialects import postgresql

revision: str = "0004"
down_revision: Union[str, None] = "0003"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.create_table(
        "learnable_languages",
        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
        sa.Column("user_id", postgresql.UUID(as_uuid=True), sa.ForeignKey("users.id"), nullable=False),
        sa.Column("source_language", sa.String(10), nullable=False),
        sa.Column("target_language", sa.String(10), nullable=False),
        sa.Column("proficiencies", postgresql.ARRAY(sa.String(5)), nullable=False),
        sa.UniqueConstraint("user_id", "source_language", "target_language", name="uq_learnable_language_user_pair"),
    )
    op.create_index("ix_learnable_languages_user_id", "learnable_languages", ["user_id"])


def downgrade() -> None:
    op.drop_index("ix_learnable_languages_user_id", table_name="learnable_languages")
    op.drop_table("learnable_languages")