"""endpoint installed-software (SBOM) snapshot table.

Adds endpointapplications: one row per installed application discovered on an
endpoint, reported by the agent as {displayname, displayversion, publisher}.
Stored as a per-asset snapshot (replaced on each report), the same way the
services/ports inventories are kept as the newest list rather than history.

appid is groundwork for a future link to the core applications catalog (the
"Managed Applications" concept): a nullable FK with ON DELETE SET NULL so
retiring a managed Application does not delete discovered rows. No
discovery-to-catalog matcher exists yet; the column is laid down now so the
association can be added without a second migration.

Idempotent: creation checks the live schema first so a db.create_all() site
(which already built the table) re-runs clean on strict MySQL 8.
"""
from alembic import op

import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = 'endpoints0004apps'
down_revision = 'endpoints0003cmdtarget'
branch_labels = None
depends_on = None


def _has_table(table_name):
    from sqlalchemy import inspect

    return inspect(op.get_bind()).has_table(table_name)


def upgrade():
    if _has_table('endpointapplications'):
        return

    op.create_table(
        'endpointapplications',
        # BigInteger, not Integer. This is a SNAPSHOT table: every check-in
        # deletes the endpoint's rows and reinserts them, so the surrogate key
        # burns through values at (endpoints x installed apps) per report and
        # never reuses them. A 32-bit key exhausts on MySQL - a few hundred
        # endpoints reporting a few hundred apps every 15 minutes reaches 2.1
        # billion inside a couple of years, and the failure is an insert that
        # stops working forever. SQLite has no such ceiling, so no test would
        # have caught it. Changed while the table is still unreleased.
        sa.Column('endpointapplicationid',
                  sa.BigInteger().with_variant(sa.Integer, 'sqlite'),
                  nullable=False),
        sa.Column('assetid', sa.Integer(), nullable=False),
        sa.Column('displayname', sa.String(length=255), nullable=False),
        sa.Column('displayversion', sa.String(length=128), nullable=True),
        sa.Column('publisher', sa.String(length=255), nullable=True),
        sa.Column('appid', sa.Integer(), nullable=True),
        sa.Column('recordedat', sa.DateTime(), nullable=False),
        sa.PrimaryKeyConstraint('endpointapplicationid'),
        sa.ForeignKeyConstraint(
            ['assetid'], ['assets.assetid'],
            name='fk_endpointapplications_assetid',
            ondelete='CASCADE'),
        sa.ForeignKeyConstraint(
            ['appid'], ['applications.appid'],
            name='fk_endpointapplications_appid',
            ondelete='SET NULL'),
    )
    op.create_index(
        'idx_endpointapplications_assetid',
        'endpointapplications', ['assetid'])
    op.create_index(
        'idx_endpointapplications_appid',
        'endpointapplications', ['appid'])
    op.create_index(
        'idx_endpointapplications_displayname',
        'endpointapplications', ['displayname'])
    op.create_index(
        'idx_endpointapplications_assetname',
        'endpointapplications', ['assetid', 'displayname'])


def downgrade():
    if not _has_table('endpointapplications'):
        return

    op.drop_index('idx_endpointapplications_assetname',
                  table_name='endpointapplications')
    op.drop_index('idx_endpointapplications_displayname',
                  table_name='endpointapplications')
    op.drop_index('idx_endpointapplications_appid',
                  table_name='endpointapplications')
    op.drop_index('idx_endpointapplications_assetid',
                  table_name='endpointapplications')
    op.drop_table('endpointapplications')