// Copyright 2024 the Go-FUSE Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package fuse

import (
	"sync"
)

// protocolServer bridges from the FUSE datatypes to a RawFileSystem
type protocolServer struct {
	fileSystem RawFileSystem

	interruptMu    sync.Mutex
	reqInflight    []*request
	connectionDead bool

	latencies LatencyMap

	kernelSettings InitIn

	opts *MountOptions

	// in-flight notify-retrieve queries
	retrieveMu   sync.Mutex
	retrieveNext uint64
	retrieveTab  map[uint64]*retrieveCacheRequest // notifyUnique -> retrieve request
}

func (ms *protocolServer) handleRequest(h *operationHandler, req *request) {
	ms.addInflight(req)
	defer ms.dropInflight(req)

	if req.status.Ok() && ms.opts.Debug {
		ms.opts.Logger.Println(req.InputDebug())
	}

	if req.inHeader().NodeId == pollHackInode ||
		req.inHeader().NodeId == FUSE_ROOT_ID && h.FileNames > 0 && req.filename() == pollHackName {
		doPollHackLookup(ms, req)
	} else if req.status.Ok() && h.Func == nil {
		ms.opts.Logger.Printf("Unimplemented opcode %v", operationName(req.inHeader().Opcode))
		req.status = ENOSYS
	} else if req.status.Ok() {
		h.Func(ms, req)
	}

	// Forget/NotifyReply do not wait for reply from filesystem server.
	switch req.inHeader().Opcode {
	case _OP_FORGET, _OP_BATCH_FORGET, _OP_NOTIFY_REPLY:
		req.suppressReply = true
	case _OP_INTERRUPT:
		// ? what other status can interrupt generate?
		if req.status.Ok() {
			req.suppressReply = true
		}
	}
	if req.status == EINTR {
		ms.interruptMu.Lock()
		dead := ms.connectionDead
		ms.interruptMu.Unlock()
		if dead {
			req.suppressReply = true
		}
	}
	if req.suppressReply {
		return
	}
	if req.inHeader().Opcode == _OP_INIT && ms.kernelSettings.Minor <= 22 {
		// v8-v22 don't have TimeGran and further fields.
		// This includes osxfuse (a.k.a. macfuse).
		req.outHeader().Length = uint32(sizeOfOutHeader) + 24
	}
	if req.fdData != nil && ms.opts.DisableSplice {
		req.outPayload, req.status = req.fdData.Bytes(req.outPayload)
		req.fdData = nil
	}

	req.serializeHeader(req.outPayloadSize())

	if ms.opts.Debug {
		ms.opts.Logger.Println(req.OutputDebug())
	}
}

func (ms *protocolServer) addInflight(req *request) {
	ms.interruptMu.Lock()
	defer ms.interruptMu.Unlock()
	req.inflightIndex = len(ms.reqInflight)
	ms.reqInflight = append(ms.reqInflight, req)
}

func (ms *protocolServer) dropInflight(req *request) {
	ms.interruptMu.Lock()
	defer ms.interruptMu.Unlock()
	this := req.inflightIndex
	last := len(ms.reqInflight) - 1
	if last != this {
		ms.reqInflight[this] = ms.reqInflight[last]
		ms.reqInflight[this].inflightIndex = this
	}
	ms.reqInflight = ms.reqInflight[:last]
}

func (ms *protocolServer) interruptRequest(unique uint64) Status {
	ms.interruptMu.Lock()
	defer ms.interruptMu.Unlock()

	// This is slow, but this operation is rare.
	for _, inflight := range ms.reqInflight {
		if unique == inflight.inHeader().Unique && !inflight.interrupted {
			close(inflight.cancel)
			inflight.interrupted = true
			return OK
		}
	}

	return EAGAIN
}

func (ms *protocolServer) cancelAll() {
	ms.interruptMu.Lock()
	defer ms.interruptMu.Unlock()
	ms.connectionDead = true
	for _, req := range ms.reqInflight {
		if !req.interrupted {
			close(req.cancel)
			req.interrupted = true
		}
	}
	// Leave ms.reqInflight alone, or dropInflight will barf.
}