// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package pipe

import (
	"fmt"
	"math"
	"syscall"

	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
	"gvisor.googlesource.com/gvisor/pkg/waiter"
)

// ReaderWriter satisfies the FileOperations interface and services both
// read and write requests. This should only be used directly for named pipes.
// pipe(2) and pipe2(2) only support unidirectional pipes and should use
// either pipe.Reader or pipe.Writer.
//
// +stateify savable
type ReaderWriter struct {
	fsutil.FilePipeSeek      `state:"nosave"`
	fsutil.FileNotDirReaddir `state:"nosave"`
	fsutil.FileNoFsync       `state:"nosave"`
	fsutil.FileNoopFlush     `state:"nosave"`
	fsutil.FileNoMMap        `state:"nosave"`
	*Pipe
}

// Release implements fs.FileOperations.Release.
func (rw *ReaderWriter) Release() {
	rw.Pipe.rClose()
	rw.Pipe.wClose()
	// Wake up readers and writers.
	rw.Pipe.Notify(waiter.EventIn | waiter.EventOut)
}

// Read implements fs.FileOperations.Read.
func (rw *ReaderWriter) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, _ int64) (int64, error) {
	n, err := rw.Pipe.read(ctx, dst)
	if n > 0 {
		rw.Pipe.Notify(waiter.EventOut)
	}
	return n, err
}

// Write implements fs.FileOperations.Write.
func (rw *ReaderWriter) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
	n, err := rw.Pipe.write(ctx, src)
	if n > 0 {
		rw.Pipe.Notify(waiter.EventIn)
	}
	return n, err
}

// Readiness returns the ready events in the underlying pipe.
func (rw *ReaderWriter) Readiness(mask waiter.EventMask) waiter.EventMask {
	return rw.Pipe.rwReadiness() & mask
}

// Ioctl implements fs.FileOperations.Ioctl.
func (rw *ReaderWriter) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
	// Switch on ioctl request.
	switch int(args[1].Int()) {
	case linux.FIONREAD:
		v := rw.queuedSize()
		if v > math.MaxInt32 {
			panic(fmt.Sprintf("Impossibly large pipe queued size: %d", v))
		}
		// Copy result to user-space.
		_, err := usermem.CopyObjectOut(ctx, io, args[2].Pointer(), int32(v), usermem.IOOpts{
			AddressSpaceActive: true,
		})
		return 0, err
	default:
		return 0, syscall.ENOTTY
	}
}