"""chat stats last deleted

Revision ID: f1c4a8e2d6b3
Revises: e8b3f1a6c2d4
Create Date: 2026-10-19 04:00:00.000000

"""

from collections.abc import Sequence

from alembic import op

revision: str = "f1c4a8e2d6b3"
down_revision: str | None = "e8b3f1a6c2d4"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None

_APPLY = """
CREATE OR REPLACE FUNCTION chat_stats_apply() RETURNS trigger LANGUAGE plpgsql AS $$
BEGIN
    IF TG_OP = 'INSERT' THEN
        INSERT INTO chat_stats AS cs (account_id, chat_id, message_count,
                                      last_date, last_message_id,
                                      last_text, last_sender_id{column})
        VALUES (NEW.account_id, NEW.chat_id, 1,
                CASE WHEN NEW.date <= now() + interval '1 day'
                     THEN NEW.date END,
                CASE WHEN NEW.date <= now() + interval '1 day'
                     THEN NEW.message_id END,
                NEW.text, NEW.sender_id{value})
        ON CONFLICT (account_id, chat_id) DO UPDATE SET
            message_count = cs.message_count + 1,
            last_date = CASE WHEN chat_stats_newer(cs, EXCLUDED)
                        THEN EXCLUDED.last_date ELSE cs.last_date END,
            last_message_id = CASE WHEN chat_stats_newer(cs, EXCLUDED)
                              THEN EXCLUDED.last_message_id
                              ELSE cs.last_message_id END,
            last_text = CASE WHEN chat_stats_newer(cs, EXCLUDED)
                        THEN EXCLUDED.last_text ELSE cs.last_text END,
            last_sender_id = CASE WHEN chat_stats_newer(cs, EXCLUDED)
                             THEN EXCLUDED.last_sender_id
                             ELSE cs.last_sender_id END{merge};
    ELSE
        UPDATE chat_stats
        SET last_text = NEW.text, last_sender_id = NEW.sender_id{update}
        WHERE account_id = NEW.account_id
          AND chat_id = NEW.chat_id
          AND last_message_id = NEW.message_id;
    END IF;
    RETURN NULL;
END;
$$
"""

_DELETED_PARTS = {
    "column": ", last_deleted",
    "value": ", NEW.deleted_at IS NOT NULL",
    "merge": (
        ",\n            last_deleted = CASE WHEN chat_stats_newer(cs, EXCLUDED)"
        " THEN EXCLUDED.last_deleted ELSE cs.last_deleted END"
    ),
    "update": ", last_deleted = NEW.deleted_at IS NOT NULL",
    "deleted": " OR OLD.deleted_at IS DISTINCT FROM NEW.deleted_at",
}
_PLAIN_PARTS = dict.fromkeys(_DELETED_PARTS, "")

_UPDATE_TRIGGER = (
    "CREATE TRIGGER messages_chat_stats_update AFTER UPDATE ON messages "
    "FOR EACH ROW WHEN (OLD.text IS DISTINCT FROM NEW.text "
    "OR OLD.sender_id IS DISTINCT FROM NEW.sender_id{deleted}) "
    "EXECUTE FUNCTION chat_stats_apply()"
)

_BACKFILL = """
UPDATE chat_stats cs SET last_deleted = true
FROM messages m
WHERE m.account_id = cs.account_id AND m.chat_id = cs.chat_id
  AND m.message_id = cs.last_message_id AND m.date = cs.last_date
  AND m.deleted_at IS NOT NULL
"""


def upgrade() -> None:
    op.execute(
        "ALTER TABLE chat_stats ADD COLUMN last_deleted boolean NOT NULL DEFAULT false"
    )
    op.execute(_BACKFILL)
    op.execute(_APPLY.format(**_DELETED_PARTS))
    op.execute("DROP TRIGGER IF EXISTS messages_chat_stats_update ON messages")
    op.execute(_UPDATE_TRIGGER.format(**_DELETED_PARTS))


def downgrade() -> None:
    op.execute("DROP TRIGGER IF EXISTS messages_chat_stats_update ON messages")
    op.execute(_UPDATE_TRIGGER.format(**_PLAIN_PARTS))
    op.execute(_APPLY.format(**_PLAIN_PARTS))
    op.execute("ALTER TABLE chat_stats DROP COLUMN last_deleted")