package notify

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

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

	mu       sync.RWMutex
	handler  func(StreamAcceptInfo) error
	streams  map[string]*streamHandle
	data     map[string]map[uint64]*streamHandle
	reserved map[string]map[uint64]struct{}
	cfg      streamConfig
	flow     *streamFlowController
}

func newStreamRuntime(rolePrefix string) *streamRuntime {
	cfg := defaultStreamConfig()
	dataStart, dataStep := uint64(1), uint64(1)
	if rolePrefix == "cstrm" {
		dataStep = 2
	} else if rolePrefix == "sstrm" {
		dataStart = 2
		dataStep = 2
	}
	return &streamRuntime{
		rolePrefix: rolePrefix,
		dataStart:  dataStart,
		dataStep:   dataStep,
		streams:    make(map[string]*streamHandle),
		data:       make(map[string]map[uint64]*streamHandle),
		reserved:   make(map[string]map[uint64]struct{}),
		cfg:        cfg,
		flow:       newStreamFlowController(cfg),
	}
}

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

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

func (r *streamRuntime) reserveDataID(scope string) (uint64, error) {
	if r == nil {
		return 0, errStreamRuntimeNil
	}
	scope = normalizeFileScope(scope)
	r.mu.Lock()
	defer r.mu.Unlock()
	id, err := r.nextDataIDLocked(scope, true)
	return id, err
}

func (r *streamRuntime) 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)
		}
	}
}

func (r *streamRuntime) nextDataIDLocked(scope string, reserve bool) (uint64, error) {
	if r == nil {
		return 0, errStreamRuntimeNil
	}
	for {
		candidate, ok := r.nextDataCandidateLocked(false)
		if !ok {
			return 0, errStreamDataIDExhausted
		}
		if r.dataInUseLocked(scope, candidate) {
			continue
		}
		if reserve {
			reserved := r.reserved[scope]
			if reserved == nil {
				reserved = make(map[uint64]struct{})
				r.reserved[scope] = reserved
			}
			reserved[candidate] = struct{}{}
		}
		return candidate, nil
	}
}

func (r *streamRuntime) nextPeerDataIDLocked(scope string) (uint64, error) {
	if r == nil {
		return 0, errStreamRuntimeNil
	}
	for {
		candidate, ok := r.nextDataCandidateLocked(true)
		if !ok {
			return 0, errStreamDataIDExhausted
		}
		if r.dataInUseLocked(scope, candidate) {
			continue
		}
		return candidate, nil
	}
}

func (r *streamRuntime) nextDataCandidateLocked(peer bool) (uint64, bool) {
	seq := &r.dataSeq
	start, step := r.dataStart, r.dataStep
	if peer && step == 2 {
		seq = &r.peerDataSeq
		start = 3 - r.dataStart
	}
	if step == 0 {
		step = 1
	}
	if *seq == 0 {
		if start == 0 {
			return 0, false
		}
		*seq = start
		return start, true
	}
	if *seq > ^uint64(0)-step {
		return 0, false
	}
	candidate := *seq + step
	if step == 2 && candidate%2 != start%2 {
		if candidate == ^uint64(0) {
			return 0, false
		}
		candidate++
	}
	*seq = candidate
	return candidate, true
}

func (r *streamRuntime) dataInUseLocked(scope string, dataID uint64) bool {
	if dataID == 0 {
		return true
	}
	if dataScope := r.data[scope]; dataScope != nil {
		if _, ok := dataScope[dataID]; ok {
			return true
		}
	}
	if reserved := r.reserved[scope]; reserved != nil {
		_, ok := reserved[dataID]
		return ok
	}
	return false
}

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

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

func (r *streamRuntime) register(scope string, stream *streamHandle) error {
	return r.registerWithDirection(scope, stream, false, false)
}

func (r *streamRuntime) registerInbound(scope string, stream *streamHandle) error {
	return r.registerWithDirection(scope, stream, true, false)
}

func (r *streamRuntime) registerReserved(scope string, stream *streamHandle) error {
	return r.registerWithDirection(scope, stream, false, true)
}

func (r *streamRuntime) registerWithDirection(scope string, stream *streamHandle, inbound bool, consumeReservation bool) error {
	if r == nil {
		return errStreamRuntimeNil
	}
	if stream == nil || stream.id == "" {
		return errStreamIDEmpty
	}
	scope = normalizeFileScope(scope)
	key := streamRuntimeKey(scope, stream.id)
	r.mu.Lock()
	defer r.mu.Unlock()
	if _, ok := r.streams[key]; ok {
		return errStreamAlreadyExists
	}
	if stream.dataID == 0 {
		var err error
		if inbound {
			stream.dataID, err = r.nextPeerDataIDLocked(scope)
		} else {
			stream.dataID, err = r.nextDataIDLocked(scope, false)
		}
		if err != nil {
			return err
		}
	}
	if stream.dataID != 0 {
		dataScope := r.data[scope]
		if dataScope == nil {
			dataScope = make(map[uint64]*streamHandle)
			r.data[scope] = dataScope
		}
		if _, ok := dataScope[stream.dataID]; ok {
			return errStreamAlreadyExists
		}
		if reserved := r.reserved[scope]; reserved != nil {
			if _, ok := reserved[stream.dataID]; ok {
				if !consumeReservation {
					return errStreamAlreadyExists
				}
				delete(reserved, stream.dataID)
				if len(reserved) == 0 {
					delete(r.reserved, scope)
				}
			}
		}
		dataScope[stream.dataID] = stream
	}
	r.streams[key] = stream
	return nil
}

// adopt transfers ownership of a newly-created stream to the runtime. A
// failed registration is terminal so its child context cannot remain attached
// to the session after the caller drops the handle.
func (r *streamRuntime) adopt(scope string, stream *streamHandle) error {
	err := r.register(scope, stream)
	if err != nil && stream != nil {
		stream.markReset(err)
	}
	return err
}

func (r *streamRuntime) adoptInbound(scope string, stream *streamHandle) error {
	err := r.registerInbound(scope, stream)
	if err != nil && stream != nil {
		stream.markReset(err)
	}
	return err
}

func (r *streamRuntime) adoptReserved(scope string, stream *streamHandle) error {
	err := r.registerReserved(scope, stream)
	if err != nil && stream != nil {
		stream.markReset(err)
	}
	return err
}

func (r *streamRuntime) lookup(scope string, streamID string) (*streamHandle, bool) {
	if r == nil || streamID == "" {
		return nil, false
	}
	key := streamRuntimeKey(scope, streamID)
	r.mu.RLock()
	defer r.mu.RUnlock()
	stream, ok := r.streams[key]
	return stream, ok
}

func (r *streamRuntime) lookupByDataID(scope string, dataID uint64) (*streamHandle, bool) {
	if r == nil || dataID == 0 {
		return nil, false
	}
	scope = normalizeFileScope(scope)
	r.mu.RLock()
	defer r.mu.RUnlock()
	dataScope := r.data[scope]
	if dataScope == nil {
		return nil, false
	}
	stream, ok := dataScope[dataID]
	return stream, ok
}

func (r *streamRuntime) lookupControl(scope string, streamID string, dataID uint64) (*streamHandle, bool) {
	if r == nil {
		return nil, false
	}
	scope = normalizeFileScope(scope)
	r.mu.RLock()
	defer r.mu.RUnlock()
	if streamID != "" {
		stream, ok := r.streams[streamRuntimeKey(scope, streamID)]
		if !ok || stream == nil {
			return nil, false
		}
		if dataID != 0 && stream.dataID != dataID {
			return nil, false
		}
		return stream, true
	}
	if dataID == 0 {
		return nil, false
	}
	stream := r.data[scope][dataID]
	return stream, stream != nil
}

func (r *streamRuntime) remove(scope string, expected *streamHandle) {
	if r == nil || expected == nil || expected.id == "" {
		return
	}
	scope = normalizeFileScope(scope)
	key := streamRuntimeKey(scope, expected.id)
	r.mu.Lock()
	defer r.mu.Unlock()
	stream := r.streams[key]
	if stream != expected {
		return
	}
	if stream.dataID != 0 {
		if dataScope := r.data[scope]; dataScope != nil {
			if dataScope[stream.dataID] == stream {
				delete(dataScope, stream.dataID)
			}
			if len(dataScope) == 0 {
				delete(r.data, scope)
			}
		}
	}
	delete(r.streams, key)
}

func (r *streamRuntime) acquireOutbound(ctx context.Context, size int) (func(), error) {
	if r == nil || r.flow == nil {
		return func() {}, nil
	}
	return r.flow.acquire(ctx, size)
}

func (r *streamRuntime) tryAcquireOutbound(size int) bool {
	if r == nil || r.flow == nil {
		return true
	}
	return r.flow.tryAcquire(size)
}

func (r *streamRuntime) releaseOutbound(size int) {
	if r == nil || r.flow == nil {
		return
	}
	r.flow.release(size)
}

func (r *streamRuntime) snapshots() []StreamSnapshot {
	if r == nil {
		return nil
	}
	r.mu.RLock()
	snapshots := make([]StreamSnapshot, 0, len(r.streams))
	for _, stream := range r.streams {
		if stream == nil {
			continue
		}
		snapshots = append(snapshots, stream.snapshot())
	}
	r.mu.RUnlock()
	sortStreamSnapshots(snapshots)
	return snapshots
}

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

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

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

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

func (r *streamRuntime) collectClientRouteLocked(route clientSessionRoute) []*streamHandle {
	streams := make([]*streamHandle, 0)
	for _, stream := range r.streams {
		if stream == nil || !sameClientSessionRoute(stream.clientRoute, route) {
			continue
		}
		streams = append(streams, stream)
	}
	return streams
}

func (r *streamRuntime) resetClientRouteHandles(streams []*streamHandle, err error) {
	resetErr := streamRuntimeCloseError(err)
	for _, stream := range streams {
		stream.markReset(resetErr)
	}
}

func (r *streamRuntime) closeMatching(match func(string) bool, err error) {
	if r == nil || match == nil {
		return
	}
	resetErr := streamRuntimeCloseError(err)
	r.mu.RLock()
	streams := make([]*streamHandle, 0, len(r.streams))
	for key, stream := range r.streams {
		if stream == nil || !match(key) {
			continue
		}
		streams = append(streams, stream)
	}
	r.mu.RUnlock()
	for _, stream := range streams {
		stream.markReset(resetErr)
	}
}

func streamRuntimeKey(scope string, streamID string) string {
	return normalizeFileScope(scope) + "\x00" + streamID
}

func (c *ClientCommon) getStreamRuntime() *streamRuntime {
	if c == nil {
		return nil
	}
	return c.streamRuntime
}

func (s *ServerCommon) getStreamRuntime() *streamRuntime {
	if s == nil {
		return nil
	}
	return s.streamRuntime
}