"""Initial migration — creates the ``ix_jobs`` table per spec §4.

Hand-written (do NOT ``alembic revision --autogenerate``) so the table layout
stays byte-exact with the MVP spec. autogenerate tends to add/drop indexes in
an order that makes diffs noisy and occasionally swaps JSONB for JSON on
dialects that don't distinguish them.

Revision ID: 001
Revises:
Create Date: 2026-04-18
"""

from __future__ import annotations

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


# revision identifiers, used by Alembic.
revision = "001"
down_revision = None
branch_labels = None
depends_on = None


def upgrade() -> None:
    """Create ``ix_jobs`` + its indexes exactly as spec §4 describes.

    JSONB for ``request`` and ``response`` (Postgres-only; the MVP doesn't
    support any other backend). CHECK constraint bakes the status enum into
    the DDL so direct SQL inserts (the pg_queue_adapter path) can't land
    bogus values. The partial index on ``status='pending'`` matches the
    claim query's ``WHERE status='pending' ORDER BY created_at`` pattern.
    """

    op.create_table(
        "ix_jobs",
        sa.Column("job_id", postgresql.UUID(as_uuid=True), primary_key=True),
        sa.Column("ix_id", sa.Text(), nullable=False),
        sa.Column("client_id", sa.Text(), nullable=False),
        sa.Column("request_id", sa.Text(), nullable=False),
        sa.Column("status", sa.Text(), nullable=False),
        sa.Column("request", postgresql.JSONB(), nullable=False),
        sa.Column("response", postgresql.JSONB(), nullable=True),
        sa.Column("callback_url", sa.Text(), nullable=True),
        sa.Column("callback_status", sa.Text(), nullable=True),
        sa.Column("attempts", sa.Integer(), nullable=False, server_default="0"),
        sa.Column(
            "created_at",
            sa.DateTime(timezone=True),
            nullable=False,
            server_default=sa.text("now()"),
        ),
        sa.Column("started_at", sa.DateTime(timezone=True), nullable=True),
        sa.Column("finished_at", sa.DateTime(timezone=True), nullable=True),
        sa.CheckConstraint(
            "status IN ('pending', 'running', 'done', 'error')",
            name="ix_jobs_status_check",
        ),
        sa.CheckConstraint(
            "callback_status IS NULL OR callback_status IN "
            "('pending', 'delivered', 'failed')",
            name="ix_jobs_callback_status_check",
        ),
    )

    # Partial index: the claim query hits only pending rows ordered by age.
    # Partial-ness keeps the index small as done/error rows accumulate.
    op.create_index(
        "ix_jobs_status_created",
        "ix_jobs",
        ["status", "created_at"],
        postgresql_where=sa.text("status = 'pending'"),
    )
    # Unique index on (client_id, request_id) enforces caller-side idempotency
    # at the DB layer. The repo relies on the unique violation to detect an
    # existing pending/running row and return it unchanged.
    op.create_index(
        "ix_jobs_client_request",
        "ix_jobs",
        ["client_id", "request_id"],
        unique=True,
    )


def downgrade() -> None:
    op.drop_index("ix_jobs_client_request", table_name="ix_jobs")
    op.drop_index("ix_jobs_status_created", table_name="ix_jobs")
    op.drop_table("ix_jobs")