package engine

import (
	"time"

	"jarl/internal/model"
	"jarl/internal/render"
)

// serialGreater reports whether a > b in RFC 1982 serial number
// arithmetic.
func serialGreater(a, b uint32) bool { return int32(a-b) > 0 }

// NextSerial returns the serial after old under policy, with the same
// semantics as BIND's serial-update-method.
func NextSerial(old uint32, policy string, now time.Time) uint32 {
	switch policy {
	case model.SerialUnixtime:
		t := uint32(now.Unix())
		if serialGreater(t, old) {
			return t
		}
		return old + 1
	case model.SerialIncrement:
		return old + 1
	default: // date: YYYYMMDDnn
		d := dateSerial(now)
		if serialGreater(d, old) {
			return d
		}
		return old + 1
	}
}

// SerialChange records a serial bump.
type SerialChange struct {
	ZoneID int64  `json:"zone_id"`
	Zone   string `json:"zone"`
	View   string `json:"view,omitempty"`
	Old    uint32 `json:"old"`
	New    uint32 `json:"new"`
}

// bumpSerials increments the serial of every primary zone in work whose
// DNS data differs from base, unless the serial was set explicitly.
func bumpSerials(base, work *model.State, now time.Time, user string) []SerialChange {
	var out []SerialChange
	for _, z := range work.SortedZones() {
		if z.Type != model.ZonePrimary {
			continue
		}
		policy := z.SerialPolicy
		if policy == "" {
			policy = work.Settings.SerialPolicy
		}
		old := base.Zones[z.ID]
		if old == nil || old.Type != model.ZonePrimary || old.ViewID != z.ViewID {
			// New to named (or moved): keep the serial it was created
			// with, which InitialSerial or the source zone provided.
			continue
		}
		if z.SOA.Serial != old.SOA.Serial {
			// Set explicitly by the user.
			continue
		}
		if render.ZoneContentHash(base, old) == render.ZoneContentHash(work, z) {
			continue
		}
		next := NextSerial(old.SOA.Serial, policy, now)
		out = append(out, SerialChange{ZoneID: z.ID, Zone: z.Name, View: work.ViewName(z), Old: old.SOA.Serial, New: next})
		z.SOA.Serial = next
		z.Touch(user, now)
	}
	return out
}