package inventory

import (
	"context"
	"errors"
	"time"

	"github.com/jackc/pgx/v5"
)

// BusStep is one planned bus upgrade (novox/hq to-be 45 §8, ADR 0235).
type BusStep struct {
	ID         int64
	Module     string
	Machines   []string
	From, To   string
	Snapshot   string
	Reversible bool
	By, Why    string
	Started    time.Time
	Ended      *time.Time
	Outcome    string
	Found      string
}

// StartBusStep records a bus upgrade starting. Refused while another runs.
func (i *Inventory) StartBusStep(ctx context.Context, s BusStep) (BusStep, error) {
	if _, err := i.actingEpoch(ctx); err != nil {
		return s, err
	}
	if open, found, err := i.LatestBusStep(ctx); err != nil {
		return s, err
	} else if found && open.Ended == nil {
		return s, ErrBusStepRunning
	}
	if s.Machines == nil {
		s.Machines = []string{}
	}
	err := i.store.Pool().QueryRow(ctx,
		`insert into bus_step (module, machines, from_build, to_build, snapshot, reversible, by_whom, why)
		 values ($1, $2, $3, $4, $5, $6, $7, $8) returning id, started`,
		s.Module, s.Machines, s.From, s.To, s.Snapshot, s.Reversible, s.By, s.Why).Scan(&s.ID, &s.Started)
	return s, err
}

// ErrBusStepRunning is a bus upgrade asked while one runs.
var ErrBusStepRunning = errors.New("a bus upgrade is already running")

// EndBusStep records how a bus upgrade ended: done or failed, with what was found.
func (i *Inventory) EndBusStep(ctx context.Context, id int64, outcome, found string) error {
	if _, err := i.actingEpoch(ctx); err != nil {
		return err
	}
	_, err := i.store.Pool().Exec(ctx,
		`update bus_step set ended = now(), outcome = $2, found = $3 where id = $1 and ended is null`, id, outcome, found)
	return err
}

// LatestBusStep is the newest bus upgrade, and whether there is any.
func (i *Inventory) LatestBusStep(ctx context.Context) (BusStep, bool, error) {
	var s BusStep
	err := i.store.Pool().QueryRow(ctx,
		`select id, module, machines, from_build, to_build, snapshot, reversible, by_whom, why, started, ended,
		        outcome, found
		   from bus_step order by id desc limit 1`).
		Scan(&s.ID, &s.Module, &s.Machines, &s.From, &s.To, &s.Snapshot, &s.Reversible, &s.By, &s.Why, &s.Started,
			&s.Ended, &s.Outcome, &s.Found)
	if errors.Is(err, pgx.ErrNoRows) {
		return s, false, nil
	}
	return s, err == nil, err
}