"""merge tasks into notes table

Revision ID: 0004
Revises: 0003
Create Date: 2025-01-01 00:00:00.000000
"""

from alembic import op
import sqlalchemy as sa

revision = "0004"
down_revision = "0003"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # Add task columns to notes table
    op.add_column("notes", sa.Column("status", sa.Text(), nullable=True))
    op.add_column("notes", sa.Column("priority", sa.Text(), nullable=True))
    op.add_column("notes", sa.Column("due_date", sa.Date(), nullable=True))
    op.create_index("ix_notes_status", "notes", ["status"])

    conn = op.get_bind()

    # Migrate tasks that have companion notes:
    # Copy status/priority/due_date to the companion note,
    # and merge the task description into the note body if the note body is empty.
    conn.execute(sa.text("""
        UPDATE notes
        SET status = t.status,
            priority = t.priority,
            due_date = t.due_date,
            body = COALESCE(NULLIF(t.description, ''), notes.body),
            tags = CASE
                WHEN array_length(t.tags, 1) IS NOT NULL THEN t.tags
                ELSE notes.tags
            END
        FROM tasks t
        WHERE t.note_id = notes.id
    """))

    # Handle orphan tasks (note_id IS NULL) — insert them as new notes
    conn.execute(sa.text("""
        INSERT INTO notes (title, body, tags, status, priority, due_date, created_at, updated_at)
        SELECT title, description, tags, status, priority, due_date, created_at, updated_at
        FROM tasks
        WHERE note_id IS NULL
    """))

    # Drop tasks table and its indexes
    op.drop_table("tasks")

    # Drop the old enum types that are no longer used by any table
    op.execute("DROP TYPE IF EXISTS task_status")
    op.execute("DROP TYPE IF EXISTS task_priority")


def downgrade() -> None:
    raise NotImplementedError("Downgrade not supported for this migration")