"""external_link table — off-platform file-host links found in post bodies

Creators host the real files on mega.nz / Google Drive / MediaFire / Dropbox /
Pixeldrain and link them in the post text. This table records each such link
(so nothing is silently dropped), and doubles as the dedup + dead-letter ledger
the download worker (a later slice) walks. `url` keeps the FULL link including
the `#fragment` — mega.nz's decryption key lives there; truncating it makes the
file undownloadable.

CHECK whitelists for host + status include the full enum up front (incl. the
download-worker statuses) so the worker slice needs no constraint migration.

Revision ID: 0049
Revises: 0048
Create Date: 2026-06-14
"""
from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

revision: str = "0049"
down_revision: Union[str, None] = "0048"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.create_table(
        "external_link",
        sa.Column("id", sa.Integer(), primary_key=True),
        sa.Column(
            "post_id", sa.Integer(),
            sa.ForeignKey("post.id", ondelete="CASCADE"), nullable=False,
        ),
        sa.Column(
            "artist_id", sa.Integer(),
            sa.ForeignKey("artist.id", ondelete="SET NULL"), nullable=True,
        ),
        sa.Column("host", sa.String(length=16), nullable=False),
        sa.Column("url", sa.Text(), nullable=False),
        sa.Column("label", sa.Text(), nullable=True),
        sa.Column(
            "status", sa.String(length=16), nullable=False,
            server_default="pending",
        ),
        sa.Column("attempts", sa.Integer(), nullable=False, server_default="0"),
        sa.Column("last_error", sa.Text(), nullable=True),
        sa.Column(
            "attachment_id", sa.Integer(),
            sa.ForeignKey("post_attachment.id", ondelete="SET NULL"),
            nullable=True,
        ),
        sa.Column(
            "created_at", sa.DateTime(timezone=True), nullable=False,
            server_default=sa.func.now(),
        ),
        sa.Column("completed_at", sa.DateTime(timezone=True), nullable=True),
        sa.Column("duration_seconds", sa.Float(), nullable=True),
        sa.CheckConstraint(
            "host IN ('mega','gdrive','mediafire','dropbox','pixeldrain')",
            name="ck_external_link_host",
        ),
        sa.CheckConstraint(
            "status IN ('pending','downloading','downloaded','failed',"
            "'skipped','dead')",
            name="ck_external_link_status",
        ),
    )
    op.create_index(
        "ix_external_link_post_id", "external_link", ["post_id"],
    )
    op.create_index(
        "ix_external_link_artist_id", "external_link", ["artist_id"],
    )
    op.create_index(
        "ix_external_link_status", "external_link", ["status"],
    )
    op.create_index(
        "uq_external_link_post_url", "external_link", ["post_id", "url"],
        unique=True,
    )


def downgrade() -> None:
    op.drop_index("uq_external_link_post_url", table_name="external_link")
    op.drop_index("ix_external_link_status", table_name="external_link")
    op.drop_index("ix_external_link_artist_id", table_name="external_link")
    op.drop_index("ix_external_link_post_id", table_name="external_link")
    op.drop_table("external_link")