package history

import (
	"context"
	"database/sql"
)

type BackfillCurrentFromObservationsResult struct {
	UpdatedComponentTypes int64 `json:"updated_component_types"`
	UpdatedInstallationSlots int64 `json:"updated_installation_slots"`
}

func (s *Service) BackfillCurrentFromObservations(ctx context.Context) (BackfillCurrentFromObservationsResult, error) {
	if s == nil || s.db == nil {
		return BackfillCurrentFromObservationsResult{}, sql.ErrConnDone
	}
	tx, err := s.db.BeginTx(ctx, &sql.TxOptions{})
	if err != nil {
		return BackfillCurrentFromObservationsResult{}, err
	}
	defer func() { _ = tx.Rollback() }()

	res1, err := tx.ExecContext(ctx, `
		UPDATE parts p
		LEFT JOIN observations o ON o.id = (
			SELECT o2.id
			FROM observations o2
			WHERE o2.part_id = p.id
			  AND JSON_EXTRACT(o2.details, '$.component_type') IS NOT NULL
			ORDER BY o2.observed_at DESC, o2.created_at DESC, o2.id DESC
			LIMIT 1
		)
		SET p.component_type = NULLIF(JSON_UNQUOTE(JSON_EXTRACT(o.details, '$.component_type')), '')
		WHERE (p.component_type IS NULL OR p.component_type = '')`)
	if err != nil {
		return BackfillCurrentFromObservationsResult{}, err
	}
	res2, err := tx.ExecContext(ctx, `
		UPDATE installations i
		LEFT JOIN observations o ON o.id = (
			SELECT o2.id
			FROM observations o2
			WHERE o2.part_id = i.part_id
			ORDER BY o2.observed_at DESC, o2.created_at DESC, o2.id DESC
			LIMIT 1
		)
		SET i.slot_name = COALESCE(
			i.slot_name,
			NULLIF(JSON_UNQUOTE(JSON_EXTRACT(o.details, '$.slot')), ''),
			NULLIF(JSON_UNQUOTE(JSON_EXTRACT(o.details, '$.attributes.location')), ''),
			CASE
			  WHEN JSON_EXTRACT(o.details, '$.attributes.socket') IS NULL THEN NULL
			  ELSE CONCAT('Socket ', JSON_UNQUOTE(JSON_EXTRACT(o.details, '$.attributes.socket')))
			END,
			NULLIF(JSON_UNQUOTE(JSON_EXTRACT(o.details, '$.attributes.bdf')), '')
		)
		WHERE i.removed_at IS NULL AND (i.slot_name IS NULL OR i.slot_name = '')`)
	if err != nil {
		return BackfillCurrentFromObservationsResult{}, err
	}

	if err := tx.Commit(); err != nil {
		return BackfillCurrentFromObservationsResult{}, err
	}
	updatedTypes, _ := res1.RowsAffected()
	updatedSlots, _ := res2.RowsAffected()
	return BackfillCurrentFromObservationsResult{UpdatedComponentTypes: updatedTypes, UpdatedInstallationSlots: updatedSlots}, nil
}