package notify

import (
	"fmt"
	"net"
	"strings"
	"sync"
	"sync/atomic"
)

type bulkRuntime struct {
	rolePrefix string
	seq        atomic.Uint64
	dataSeq    uint64
	dataStart  uint64
	dataStep   uint64

	mu       sync.RWMutex
	handler  func(BulkAcceptInfo) error
	bulks    map[string]*bulkHandle
	inbound  map[string]map[uint64]*bulkHandle
	outbound map[string]map[uint64]*bulkHandle
	reserved map[string]map[uint64]struct{}
}

type bulkDataIndexDirection uint8

const (
	bulkDataIndexInbound bulkDataIndexDirection = 1 << iota
	bulkDataIndexOutbound
	bulkDataIndexBoth = bulkDataIndexInbound | bulkDataIndexOutbound
)

func newBulkRuntime(rolePrefix string) *bulkRuntime {
	dataStart, dataStep := uint64(1), uint64(1)
	// Client- and server-originated IDs occupy disjoint wire namespaces. A
	// bulk is duplex, so every incoming frame must be routable by DataID alone;
	// partitioning the allocator prevents simultaneous opens from colliding.
	if rolePrefix == "cblk" {
		dataStep = 2
	} else if rolePrefix == "sblk" {
		dataStart = 2
		dataStep = 2
	}
	return &bulkRuntime{
		rolePrefix: rolePrefix,
		dataStart:  dataStart,
		dataStep:   dataStep,
		bulks:      make(map[string]*bulkHandle),
		inbound:    make(map[string]map[uint64]*bulkHandle),
		outbound:   make(map[string]map[uint64]*bulkHandle),
		reserved:   make(map[string]map[uint64]struct{}),
	}
}

func (r *bulkRuntime) nextID() string {
	if r == nil {
		return ""
	}
	return fmt.Sprintf("%s-%d", r.rolePrefix, r.seq.Add(1))
}

func (r *bulkRuntime) nextDataID() uint64 {
	if r == nil {
		return 0
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	id, _ := r.nextDataIDLocked(defaultFileScope, nil)
	return id
}

// reserveDataID allocates a DataID before an open request is sent. The
// reservation prevents another concurrent open from selecting the same ID
// while the caller is still constructing and registering its bulk handle.
func (r *bulkRuntime) reserveDataID(scope string, requested uint64) (uint64, error) {
	if r == nil {
		return 0, errBulkRuntimeNil
	}
	scope = normalizeFileScope(scope)
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.nextDataIDLocked(scope, &requested)
}

func (r *bulkRuntime) releaseDataID(scope string, dataID uint64) {
	if r == nil || dataID == 0 {
		return
	}
	scope = normalizeFileScope(scope)
	r.mu.Lock()
	defer r.mu.Unlock()
	if reserved := r.reserved[scope]; reserved != nil {
		delete(reserved, dataID)
		if len(reserved) == 0 {
			delete(r.reserved, scope)
		}
	}
}

// nextDataIDLocked chooses an ID under r.mu. requested is nil for an
// internal auto allocation and points to zero/non-zero for a caller that
// wants a reservation for an outbound open.
func (r *bulkRuntime) nextDataIDLocked(scope string, requested *uint64) (uint64, error) {
	if r == nil {
		return 0, errBulkRuntimeNil
	}
	var wanted uint64
	if requested != nil {
		wanted = *requested
	}
	dataScope := r.outbound[scope]
	inboundScope := r.inbound[scope]
	reserved := r.reserved[scope]
	if wanted != 0 {
		if !r.localDataID(wanted) {
			return 0, errBulkDataIDEmpty
		}
		if dataScope != nil {
			if _, exists := dataScope[wanted]; exists {
				return 0, errBulkAlreadyExists
			}
		}
		if inboundScope != nil {
			if _, exists := inboundScope[wanted]; exists {
				return 0, errBulkAlreadyExists
			}
		}
		if _, exists := reserved[wanted]; exists {
			return 0, errBulkAlreadyExists
		}
		if wanted > r.dataSeq {
			r.dataSeq = wanted
		}
		if reserved == nil {
			reserved = make(map[uint64]struct{})
			r.reserved[scope] = reserved
		}
		reserved[wanted] = struct{}{}
		return wanted, nil
	}
	for {
		candidate, ok := r.nextDataCandidateLocked()
		if !ok {
			return 0, errBulkDataIDExhausted
		}
		if dataScope != nil {
			if _, exists := dataScope[candidate]; exists {
				continue
			}
		}
		if inboundScope != nil {
			if _, exists := inboundScope[candidate]; exists {
				continue
			}
		}
		if _, exists := reserved[candidate]; exists {
			continue
		}
		if requested != nil {
			if reserved == nil {
				reserved = make(map[uint64]struct{})
				r.reserved[scope] = reserved
			}
			reserved[candidate] = struct{}{}
		}
		return candidate, nil
	}
}

func (r *bulkRuntime) nextDataCandidateLocked() (uint64, bool) {
	if r == nil {
		return 0, false
	}
	step := r.dataStep
	if step == 0 {
		step = 1
	}
	if r.dataSeq == 0 {
		candidate := r.dataStart
		if candidate == 0 {
			return 0, false
		}
		r.dataSeq = candidate
		return candidate, true
	}
	if r.dataSeq > ^uint64(0)-step {
		return 0, false
	}
	candidate := r.dataSeq + step
	if step == 2 && candidate%2 != r.dataStart%2 {
		if candidate == ^uint64(0) {
			return 0, false
		}
		candidate++
	}
	r.dataSeq = candidate
	return candidate, true
}

func (r *bulkRuntime) localDataID(dataID uint64) bool {
	if r == nil || dataID == 0 {
		return false
	}
	if r.dataStep != 2 {
		return true
	}
	return dataID%2 == r.dataStart%2
}

func (r *bulkRuntime) setHandler(fn func(BulkAcceptInfo) error) {
	if r == nil {
		return
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	r.handler = fn
}

func (r *bulkRuntime) handlerSnapshot() func(BulkAcceptInfo) error {
	if r == nil {
		return nil
	}
	r.mu.RLock()
	defer r.mu.RUnlock()
	return r.handler
}

func (r *bulkRuntime) register(scope string, bulk *bulkHandle) error {
	// Keep the old helper usable by package-local callers and tests. Production
	// paths use registerInbound/registerOutbound so a DataID can exist once in
	// each direction without making inbound frame dispatch ambiguous.
	return r.registerWithDirections(scope, bulk, bulkDataIndexBoth, false)
}

func (r *bulkRuntime) registerInbound(scope string, bulk *bulkHandle) error {
	return r.registerWithDirections(scope, bulk, bulkDataIndexInbound, false)
}

// adoptInbound transfers ownership of a newly-created handle to the runtime.
// A failed registration is terminal because the handle has already started
// its background workers and must not be reused by the caller.
func (r *bulkRuntime) adoptInbound(scope string, bulk *bulkHandle) error {
	err := r.registerInbound(scope, bulk)
	if err != nil && bulk != nil {
		bulk.markReset(err)
	}
	return err
}

func (r *bulkRuntime) registerOutbound(scope string, bulk *bulkHandle) error {
	return r.registerWithDirections(scope, bulk, bulkDataIndexOutbound, false)
}

func (r *bulkRuntime) registerReserved(scope string, bulk *bulkHandle) error {
	return r.registerWithDirections(scope, bulk, bulkDataIndexOutbound, true)
}

// adoptReserved is the outbound counterpart of adoptInbound. The caller must
// still release an unconsumed DataID reservation when this method fails.
func (r *bulkRuntime) adoptReserved(scope string, bulk *bulkHandle) error {
	err := r.registerReserved(scope, bulk)
	if err != nil && bulk != nil {
		bulk.markReset(err)
	}
	return err
}

func (r *bulkRuntime) registerWithDirections(scope string, bulk *bulkHandle, direction bulkDataIndexDirection, consumeReservation bool) error {
	if r == nil {
		return errBulkRuntimeNil
	}
	if bulk == nil || bulk.id == "" {
		return errBulkIDEmpty
	}
	scope = normalizeFileScope(scope)
	key := bulkRuntimeKey(scope, bulk.id)
	r.mu.Lock()
	defer r.mu.Unlock()
	if _, ok := r.bulks[key]; ok {
		return errBulkAlreadyExists
	}
	if direction == 0 {
		return errBulkDataIDEmpty
	}
	if bulk.dataID == 0 {
		dataID, err := r.nextDataIDLocked(scope, nil)
		if err != nil {
			return err
		}
		bulk.dataID = dataID
	} else if direction&bulkDataIndexOutbound != 0 && r.localDataID(bulk.dataID) && bulk.dataID > r.dataSeq {
		r.dataSeq = bulk.dataID
	}
	inbound := r.inbound[scope]
	outbound := r.outbound[scope]
	if direction&bulkDataIndexInbound != 0 && inbound != nil {
		if _, ok := inbound[bulk.dataID]; ok {
			return errBulkAlreadyExists
		}
	}
	if direction&bulkDataIndexOutbound != 0 && outbound != nil {
		if _, ok := outbound[bulk.dataID]; ok {
			return errBulkAlreadyExists
		}
	}
	// New peers use disjoint odd/even namespaces. Reject a legacy peer's
	// colliding explicit ID when both directions would otherwise share one
	// wire DataID; the inbound-frame router cannot disambiguate that case.
	if r.dataStep == 2 {
		if direction&bulkDataIndexInbound != 0 && outbound != nil {
			if _, ok := outbound[bulk.dataID]; ok {
				return errBulkAlreadyExists
			}
		}
		if direction&bulkDataIndexOutbound != 0 && inbound != nil {
			if _, ok := inbound[bulk.dataID]; ok {
				return errBulkAlreadyExists
			}
		}
	}
	if direction&bulkDataIndexOutbound != 0 {
		if reserved := r.reserved[scope]; reserved != nil {
			if _, exists := reserved[bulk.dataID]; exists {
				if !consumeReservation {
					return errBulkAlreadyExists
				}
				delete(reserved, bulk.dataID)
				if len(reserved) == 0 {
					delete(r.reserved, scope)
				}
			}
		}
	}
	r.bulks[key] = bulk
	if direction&bulkDataIndexInbound != 0 {
		if inbound == nil {
			inbound = make(map[uint64]*bulkHandle)
			r.inbound[scope] = inbound
		}
		inbound[bulk.dataID] = bulk
	}
	if direction&bulkDataIndexOutbound != 0 {
		if outbound == nil {
			outbound = make(map[uint64]*bulkHandle)
			r.outbound[scope] = outbound
		}
		outbound[bulk.dataID] = bulk
	}
	return nil
}

func (r *bulkRuntime) lookup(scope string, bulkID string) (*bulkHandle, bool) {
	if r == nil || bulkID == "" {
		return nil, false
	}
	key := bulkRuntimeKey(scope, bulkID)
	r.mu.RLock()
	defer r.mu.RUnlock()
	bulk, ok := r.bulks[key]
	return bulk, ok
}

func (r *bulkRuntime) lookupByDataID(scope string, dataID uint64) (*bulkHandle, bool) {
	return r.lookupByDataIDDirection(scope, dataID, bulkDataIndexBoth)
}

func (r *bulkRuntime) lookupInboundByDataID(scope string, dataID uint64) (*bulkHandle, bool) {
	return r.lookupByDataIDDirection(scope, dataID, bulkDataIndexInbound)
}

// lookupInboundFrame chooses the local-open or peer-open index from the
// allocator partition. Both bulk kinds are duplex; the partition identifies
// which handle owns a wire DataID before consulting the corresponding map.
func (r *bulkRuntime) lookupInboundFrame(scope string, dataID uint64) (*bulkHandle, bool) {
	if r == nil {
		return nil, false
	}
	if r.dataStep != 2 {
		return r.lookupByDataID(scope, dataID)
	}
	if r.localDataID(dataID) {
		if bulk, ok := r.lookupOutboundByDataID(scope, dataID); ok {
			return bulk, true
		}
		// Legacy peers may send DataID=0 in the open request. The receiver
		// allocates an ID locally in that case, so accept the inbound index
		// when the preferred outbound slot is absent.
		return r.lookupInboundByDataID(scope, dataID)
	}
	if bulk, ok := r.lookupInboundByDataID(scope, dataID); ok {
		return bulk, true
	}
	// Keep old peers that selected the local namespace routable when no
	// inbound handle occupies the ID.
	return r.lookupOutboundByDataID(scope, dataID)
}

func (r *bulkRuntime) lookupOutboundByDataID(scope string, dataID uint64) (*bulkHandle, bool) {
	return r.lookupByDataIDDirection(scope, dataID, bulkDataIndexOutbound)
}

func (r *bulkRuntime) lookupByDataIDDirection(scope string, dataID uint64, direction bulkDataIndexDirection) (*bulkHandle, bool) {
	if r == nil || dataID == 0 {
		return nil, false
	}
	scope = normalizeFileScope(scope)
	r.mu.RLock()
	defer r.mu.RUnlock()
	var inbound, outbound *bulkHandle
	if direction&bulkDataIndexInbound != 0 {
		if dataScope := r.inbound[scope]; dataScope != nil {
			inbound = dataScope[dataID]
		}
	}
	if direction&bulkDataIndexOutbound != 0 {
		if dataScope := r.outbound[scope]; dataScope != nil {
			outbound = dataScope[dataID]
		}
	}
	if direction == bulkDataIndexBoth && inbound != nil && outbound != nil && inbound != outbound {
		return nil, false
	}
	if inbound != nil {
		return inbound, true
	}
	if outbound != nil {
		return outbound, true
	}
	return nil, false
}

// lookupControl resolves the identity carried by a control message. A
// supplied BulkID is authoritative and, when present, DataID must agree. A
// DataID-only message is accepted only when it maps to one direction; using a
// colliding ID from the other direction would otherwise reset the wrong bulk.
func (r *bulkRuntime) lookupControl(scope string, bulkID string, dataID uint64) (*bulkHandle, bool) {
	if r == nil {
		return nil, false
	}
	scope = normalizeFileScope(scope)
	r.mu.RLock()
	defer r.mu.RUnlock()
	if bulkID != "" {
		bulk, ok := r.bulks[bulkRuntimeKey(scope, bulkID)]
		if !ok || bulk == nil {
			return nil, false
		}
		if dataID != 0 && bulk.dataID != dataID {
			return nil, false
		}
		return bulk, true
	}
	if dataID == 0 {
		return nil, false
	}
	var inbound, outbound *bulkHandle
	if dataScope := r.inbound[scope]; dataScope != nil {
		inbound = dataScope[dataID]
	}
	if dataScope := r.outbound[scope]; dataScope != nil {
		outbound = dataScope[dataID]
	}
	if inbound != nil && outbound != nil && inbound != outbound {
		return nil, false
	}
	if inbound != nil {
		return inbound, true
	}
	return outbound, outbound != nil
}

func (r *bulkRuntime) remove(scope string, expected *bulkHandle) {
	if r == nil || expected == nil || expected.id == "" {
		return
	}
	scope = normalizeFileScope(scope)
	key := bulkRuntimeKey(scope, expected.id)
	r.mu.Lock()
	defer r.mu.Unlock()
	bulk := r.bulks[key]
	if bulk != expected {
		return
	}
	if bulk.dataID != 0 {
		if dataScope := r.inbound[scope]; dataScope != nil {
			if dataScope[bulk.dataID] == bulk {
				delete(dataScope, bulk.dataID)
			}
			if len(dataScope) == 0 {
				delete(r.inbound, scope)
			}
		}
		if dataScope := r.outbound[scope]; dataScope != nil {
			if dataScope[bulk.dataID] == bulk {
				delete(dataScope, bulk.dataID)
			}
			if len(dataScope) == 0 {
				delete(r.outbound, scope)
			}
		}
	}
	delete(r.bulks, key)
}

func (r *bulkRuntime) closeAll(err error) {
	r.closeMatching(func(string) bool { return true }, err)
}

func (r *bulkRuntime) closeScope(scope string, err error) {
	scope = normalizeFileScope(scope)
	r.closeMatching(func(key string) bool {
		return strings.HasPrefix(key, scope+"\x00")
	}, err)
}

func (r *bulkRuntime) closeClientRoute(route clientSessionRoute, err error) {
	if r == nil {
		return
	}
	if !r.mu.TryRLock() {
		go r.closeClientRouteBlocking(route, err)
		return
	}
	bulks := r.collectClientRouteLocked(route)
	r.mu.RUnlock()
	r.resetClientRouteHandles(bulks, err)
}

func (r *bulkRuntime) closeClientRouteBlocking(route clientSessionRoute, err error) {
	r.mu.RLock()
	bulks := r.collectClientRouteLocked(route)
	r.mu.RUnlock()
	r.resetClientRouteHandles(bulks, err)
}

func (r *bulkRuntime) collectClientRouteLocked(route clientSessionRoute) []*bulkHandle {
	bulks := make([]*bulkHandle, 0)
	for _, bulk := range r.bulks {
		if bulk == nil || !sameClientSessionRoute(bulk.clientRoute, route) {
			continue
		}
		bulks = append(bulks, bulk)
	}
	return bulks
}

func (r *bulkRuntime) resetClientRouteHandles(bulks []*bulkHandle, err error) {
	resetErr := bulkRuntimeCloseError(err)
	for _, bulk := range bulks {
		bulk.markReset(resetErr)
	}
}

func (r *bulkRuntime) closeMatching(match func(string) bool, err error) {
	if r == nil || match == nil {
		return
	}
	resetErr := bulkRuntimeCloseError(err)
	r.mu.RLock()
	bulks := make([]*bulkHandle, 0, len(r.bulks))
	for key, bulk := range r.bulks {
		if bulk == nil || !match(key) {
			continue
		}
		bulks = append(bulks, bulk)
	}
	r.mu.RUnlock()
	for _, bulk := range bulks {
		bulk.markReset(resetErr)
	}
}

func (r *bulkRuntime) resetDedicatedByConn(scope string, conn net.Conn, err error) {
	if r == nil || conn == nil {
		return
	}
	scope = normalizeFileScope(scope)
	resetErr := bulkRuntimeCloseError(err)
	prefix := scope + "\x00"
	r.mu.RLock()
	bulks := make([]*bulkHandle, 0, len(r.bulks))
	for key, bulk := range r.bulks {
		if bulk == nil {
			continue
		}
		if !strings.HasPrefix(key, prefix) {
			continue
		}
		if !bulk.Dedicated() {
			continue
		}
		if bulk.dedicatedConnSnapshot() != conn {
			continue
		}
		bulks = append(bulks, bulk)
	}
	r.mu.RUnlock()
	for _, bulk := range bulks {
		bulk.markReset(resetErr)
	}
}

func (r *bulkRuntime) handleDedicatedReadErrorByConn(scope string, conn net.Conn, err error) {
	if r == nil || conn == nil {
		return
	}
	scope = normalizeFileScope(scope)
	prefix := scope + "\x00"
	r.mu.RLock()
	bulks := make([]*bulkHandle, 0, len(r.bulks))
	for key, bulk := range r.bulks {
		if bulk == nil {
			continue
		}
		if !strings.HasPrefix(key, prefix) {
			continue
		}
		if !bulk.Dedicated() {
			continue
		}
		if bulk.dedicatedConnSnapshot() != conn {
			continue
		}
		bulks = append(bulks, bulk)
	}
	r.mu.RUnlock()
	for _, bulk := range bulks {
		handleDedicatedBulkReadError(bulk, err)
	}
}

func (r *bulkRuntime) attachSharedDedicatedConn(scope string, laneID uint32, conn net.Conn) {
	if r == nil || conn == nil {
		return
	}
	scope = normalizeFileScope(scope)
	laneID = normalizeBulkDedicatedLaneID(laneID)
	prefix := scope + "\x00"
	r.mu.RLock()
	bulks := make([]*bulkHandle, 0, len(r.bulks))
	for key, bulk := range r.bulks {
		if bulk == nil {
			continue
		}
		if !strings.HasPrefix(key, prefix) {
			continue
		}
		if !bulk.Dedicated() {
			continue
		}
		if bulk.dedicatedLaneIDSnapshot() != laneID {
			continue
		}
		bulks = append(bulks, bulk)
	}
	r.mu.RUnlock()
	for _, bulk := range bulks {
		current := bulk.dedicatedConnSnapshot()
		switch {
		case current == conn:
			_ = bulk.attachDedicatedConnShared(conn)
		case current == nil:
			_ = bulk.attachDedicatedConnShared(conn)
		default:
			oldConn, oldSender, err := bulk.replaceDedicatedConnShared(conn)
			if err != nil {
				bulk.markReset(err)
				continue
			}
			if oldSender != nil {
				oldSender.stop()
			}
			if oldConn != nil {
				_ = oldConn.Close()
			}
		}
	}
}

func (r *bulkRuntime) dedicatedBulksForConn(scope string, conn net.Conn) []*bulkHandle {
	if r == nil || conn == nil {
		return nil
	}
	scope = normalizeFileScope(scope)
	prefix := scope + "\x00"
	r.mu.RLock()
	bulks := make([]*bulkHandle, 0, len(r.bulks))
	for key, bulk := range r.bulks {
		if bulk == nil {
			continue
		}
		if !strings.HasPrefix(key, prefix) {
			continue
		}
		if !bulk.Dedicated() {
			continue
		}
		if bulk.dedicatedConnSnapshot() != conn {
			continue
		}
		bulks = append(bulks, bulk)
	}
	r.mu.RUnlock()
	return bulks
}

func (r *bulkRuntime) snapshots() []BulkSnapshot {
	if r == nil {
		return nil
	}
	r.mu.RLock()
	snapshots := make([]BulkSnapshot, 0, len(r.bulks))
	for _, bulk := range r.bulks {
		if bulk == nil {
			continue
		}
		snapshots = append(snapshots, bulk.snapshot())
	}
	r.mu.RUnlock()
	sortBulkSnapshots(snapshots)
	return snapshots
}

func bulkRuntimeKey(scope string, bulkID string) string {
	return normalizeFileScope(scope) + "\x00" + bulkID
}

func bulkRuntimeCloseError(err error) error {
	if err != nil {
		return err
	}
	return errServiceShutdown
}

func (c *ClientCommon) getBulkRuntime() *bulkRuntime {
	if c == nil {
		return nil
	}
	return c.bulkRuntime
}

func (s *ServerCommon) getBulkRuntime() *bulkRuntime {
	if s == nil {
		return nil
	}
	return s.bulkRuntime
}