package hostops

import (
	"context"

	"github.com/carlosframework/platform/internal/hostclaim"
)

// CompletePurgeFences releases every held purge fence, records that in the
// journal while the purging operation still owns admission, closes the
// incarnation with the typed CompletePurge (the only writer of last_purge),
// and finally removes the journal. Each step replays.
func (c Controller) CompletePurgeFences(ctx context.Context, h *OperationHandle) error {
	if c.Control == nil || h == nil || h.Kind() != OpPurging {
		return ErrContract
	}
	account, app, id, appID := h.Account(), h.App(), h.ID(), h.AppID()
	j, _, err := ReadPurgeJournal(ctx, c.Store, account, app, id, appID)
	if err != nil {
		return err
	}
	if j.Phase != "done" {
		return ErrPending
	}
	if !j.Cleanup.Fences {
		for host, ph := range j.Hosts {
			if ph.FenceState != "held" {
				continue
			}
			obs, err := hostclaim.Read(ctx, c.Store, host)
			if err != nil {
				return err
			}
			if obs.Absent {
				return ErrPending
			}
			if obs.Claim.Holder == nil && obs.Claim.Op.Kind == hostclaim.KindPurging && obs.Claim.Op.ID == id {
				if _, err = hostclaim.Update(ctx, c.Store, obs, ReleasePurgeFence(id)); err != nil {
					return err
				}
			} else if obs.Claim.Gen <= ph.FenceGen {
				return ErrPending
			}
			// A changed successor cannot have been admitted before this fence
			// was released. Do not touch it; keep the old generation as proof.
			fresh, tag, err := ReadPurgeJournal(ctx, c.Store, account, app, id, appID)
			if err != nil {
				return err
			}
			saved := fresh.Hosts[host]
			saved.FenceState = "released"
			fresh.Hosts[host] = saved
			if _, err = c.Control.SavePurgeJournal(ctx, fresh, tag); err != nil {
				return err
			}
		}
		fresh, tag, err := ReadPurgeJournal(ctx, c.Store, account, app, id, appID)
		if err != nil {
			return err
		}
		fresh.Cleanup.Fences = true
		if _, err = c.Control.SavePurgeJournal(ctx, fresh, tag); err != nil {
			return err
		}
	}
	if err = h.CompletePurge(ctx); err != nil {
		return err
	}
	return c.Control.RemovePurgeJournal(ctx, account, app, id)
}