package backup

import (
	"context"
	"sort"
	"sync"
	"time"

	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
)

// ForeignKeyLedger (R-366 slice 2, `09` §3 decision 168) holds, per backup tier, the whole-guest archives the
// restore-test pick skipped because another key wrote them (R-727 — an earlier install of this box). Since R-727 the
// skip was one INFO log line per archive and nothing else, so after a reinstall the operator was never told that the
// box's older whole-guest copies are unreadable to it. The host report carries this ledger; the hub raises ONE
// operator event when it changes.
//
// It reports nil until a tier has been evaluated since the agent started, so a restart does not read as "the set
// changed to empty" (the hub keeps its last state for an absent field).
type ForeignKeyLedger struct {
	mu       sync.Mutex
	byTarget map[string]hub.ForeignKeyArchives
}

// NewForeignKeyLedger builds an empty ledger.
func NewForeignKeyLedger() *ForeignKeyLedger {
	return &ForeignKeyLedger{}
}

func (l *ForeignKeyLedger) set(target string, n int, oldest, newest int64) {
	l.mu.Lock()
	defer l.mu.Unlock()
	if l.byTarget == nil {
		l.byTarget = map[string]hub.ForeignKeyArchives{}
	}
	e := hub.ForeignKeyArchives{Target: target, Count: n}
	if n > 0 {
		e.Oldest = time.Unix(oldest, 0).UTC().Format(time.RFC3339)
		e.Newest = time.Unix(newest, 0).UTC().Format(time.RFC3339)
	}
	l.byTarget[target] = e
}

// ForeignKeyArchives implements hub.ForeignKeyArchiveReporter: nil before any evaluation; otherwise the tiers that
// hold such archives (`Tiers` empty, never nil, when none do), sorted by tier.
func (l *ForeignKeyLedger) ForeignKeyArchives(context.Context) *hub.ForeignKeyArchivesStanza {
	l.mu.Lock()
	defer l.mu.Unlock()
	if l.byTarget == nil {
		return nil
	}
	out := []hub.ForeignKeyArchives{}
	for _, e := range l.byTarget {
		if e.Count > 0 {
			out = append(out, e)
		}
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Target < out[j].Target })
	return &hub.ForeignKeyArchivesStanza{Tiers: out}
}