package approval

import (
	"encoding/json"
	"fmt"
	"time"

	assignerseat "git.novox.be/novox/mesh-contracts/go/seats/meshmoduleassigner"
)

// AskedOn is the seat an ask is raised on, whose holder must be there for a marked call to be asked (§19).
const AskedOn = "operator-channel"

// UnreadableAfter is how long the state approvals fails before the runner's finding says so (§19).
const UnreadableAfter = 5 * time.Minute

// unreadableKey is the bound key whose expiry raises `approvals-unreadable` (lead answer A-157).
func (g *Gate) unreadableKey() string { return g.d.Node + ".unreadable." + StateName }

// held says why no marked call can be asked now, or "" (§19): no module holds operator-channel, as the assigner's view
// of the seat's holders says, or that view is not read.
func (g *Gate) held() string {
	if g.d.Holder == nil {
		return "the tool runner reads no view of the seats' holders, so it cannot tell that a module holds " + AskedOn
	}
	ok, err := g.d.Holder(AskedOn)
	switch {
	case err != nil:
		return fmt.Sprintf("whether a module holds %s cannot be read: %v", AskedOn, err)
	case !ok:
		return "no module holds " + AskedOn + ", so nobody can be asked"
	}
	return ""
}

// stateFailed notes that the state approvals could not be read or written: no marked call runs on this machine until it
// can, the failed read or write is made again at the next marked call and at the next membership change (A-157), and
// five minutes on the runner's finding says it (§19).
func (g *Gate) stateFailed(err error) {
	g.mu.Lock()
	first := g.failingSince.IsZero()
	if first {
		g.failingSince = g.d.Now()
	}
	g.mu.Unlock()
	if first {
		g.d.Logf("[mesh-tools] the state %s on %s cannot be read or written (%v): no marked call runs here until it can", StateName, g.d.Node, err)
		if g.d.Bounds != nil {
			if e := g.d.Bounds.CreateTTL(g.unreadableKey(), map[string]string{"since": g.d.Now().UTC().Format(time.RFC3339)}, UnreadableAfter); e != nil {
				g.d.Logf("[mesh-tools] the bound of the state %s's failure is not kept: %v", StateName, e)
			}
		}
	}
}

// stateRead notes that the state approvals was read or written: a failure noted before ends, its finding cleared.
func (g *Gate) stateRead() {
	g.mu.Lock()
	was := !g.failingSince.IsZero()
	g.failingSince = time.Time{}
	g.mu.Unlock()
	if !was {
		return
	}
	if g.d.Bounds != nil {
		_ = g.d.Bounds.Delete(g.unreadableKey())
	}
	g.finding(StateName, KindApprovalsUnreadable, false, "the state "+StateName+" is read again", "")
}

// failing says the state approvals is failing now.
func (g *Gate) failing() bool {
	g.mu.Lock()
	defer g.mu.Unlock()
	return !g.failingSince.IsZero()
}

// StateAgain makes the failed read of the state approvals again: at the next membership change the runner hears (A-157).
func (g *Gate) StateAgain() {
	if g.d.State == nil || !g.failing() {
		return
	}
	if _, err := g.d.State.Keys(); err != nil {
		return
	}
	g.stateRead()
}

// unreadableExpired is the bound key of a failing state expiring: the finding raised while the state still fails.
func (g *Gate) unreadableExpired() {
	g.mu.Lock()
	since := g.failingSince
	g.mu.Unlock()
	if since.IsZero() {
		return
	}
	g.finding(StateName, KindApprovalsUnreadable, true, fmt.Sprintf("the state %s on %s cannot be read or written since %s: no marked call "+
		"runs here until it can", StateName, g.d.Node, since.UTC().Format(time.RFC3339)), "approvals unreadable on "+g.d.Node)
}

// HoldersIn is Holder over the assigner's view of the seats' holders as the runner holds it (§19): view answers the view's
// values by key, an error while its first view is not answered; a seat is held when its key names a holder.
func HoldersIn(view func() (map[string][]byte, error)) func(seat string) (bool, error) {
	return func(seat string) (bool, error) {
		values, err := view()
		if err != nil {
			return false, err
		}
		raw, ok := values[assignerseat.SeatHoldersBySeatKey(seat)]
		if !ok {
			return false, nil
		}
		var h assignerseat.SeatHolders
		if err := json.Unmarshal(raw, &h); err != nil {
			return false, fmt.Errorf("the holders of %s cannot be read: %w", seat, err)
		}
		return len(h.Holders) > 0, nil
	}
}