package database

import (
	"fmt"

	"gorm.io/gorm"
)

// The running totals in a webhook's event database keep the webhook
// page's lifetime figures right after retention has removed the rows
// they count, and let the page show them without counting every row.
// Each total changes in the transaction that writes or deletes the
// rows it counts.

// EventTotals is the single row counting a webhook's events: every
// event ever stored, and how many of them retention has deleted.
type EventTotals struct {
	ID int64 `gorm:"primaryKey"`

	Events        int64 `gorm:"not null"`
	EventsRemoved int64 `gorm:"not null"`
}

// TableName names the table AddEventTotals updates.
func (EventTotals) TableName() string {
	return "event_totals"
}

// TargetTotals is one row per target counting its deliveries: every
// delivery ever created, how many became delivered and how many
// failed, and how many deliveries and failed deliveries retention has
// deleted. The webhook's delivery figures are these rows summed.
type TargetTotals struct {
	TargetID string `gorm:"type:uuid;primaryKey"`

	Deliveries int64 `gorm:"not null"`
	Delivered  int64 `gorm:"not null"`
	Failed     int64 `gorm:"not null"`

	DeliveriesRemoved int64 `gorm:"not null"`
	FailedRemoved     int64 `gorm:"not null"`
}

// TableName names the table AddTargetTotals updates.
func (TargetTotals) TableName() string {
	return "target_totals"
}

// AddEventTotals adds each count in add to the webhook's event totals.
// Call it on the transaction that writes or deletes the events it
// counts.
func AddEventTotals(tx *gorm.DB, add EventTotals) error {
	err := tx.Exec(
		`UPDATE event_totals SET
			events = events + ?,
			events_removed = events_removed + ?`,
		add.Events, add.EventsRemoved,
	).Error
	if err != nil {
		return fmt.Errorf("adding to event totals: %w", err)
	}

	return nil
}

// AddTargetTotals adds each count in add to the totals of the target
// add.TargetID names, creating its row the first time. Call it on the
// transaction that writes or deletes the deliveries it counts.
func AddTargetTotals(tx *gorm.DB, add TargetTotals) error {
	err := tx.Exec(
		`INSERT INTO target_totals (target_id, deliveries, delivered,
			failed, deliveries_removed, failed_removed)
		VALUES (?, ?, ?, ?, ?, ?)
		ON CONFLICT (target_id) DO UPDATE SET
			deliveries = deliveries + excluded.deliveries,
			delivered = delivered + excluded.delivered,
			failed = failed + excluded.failed,
			deliveries_removed =
				deliveries_removed + excluded.deliveries_removed,
			failed_removed = failed_removed + excluded.failed_removed`,
		add.TargetID, add.Deliveries, add.Delivered,
		add.Failed, add.DeliveriesRemoved, add.FailedRemoved,
	).Error
	if err != nil {
		return fmt.Errorf(
			"adding to totals of target %s: %w", add.TargetID, err,
		)
	}

	return nil
}