/*
Copyright 2017 The GoStor Authors All rights reserved.

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 scsi

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"sync"
	"unsafe"

	"github.com/gostor/gotgt/pkg/api"
	log "github.com/sirupsen/logrus"
)

// SCSITargetService SCSI target service
type SCSITargetService struct {
	mutex   sync.RWMutex
	Targets []*api.SCSITarget
}

var _instance *SCSITargetService
var service sync.Once

// NewSCSITargetService create a new SCSITargetService
func NewSCSITargetService() *SCSITargetService {
	service.Do(func() {
		_instance = &SCSITargetService{Targets: []*api.SCSITarget{}}
	})
	return _instance
}

// GetTargetList get SCSI target list
func (s *SCSITargetService) GetTargetList() ([]*api.SCSITarget, error) {
	result := []*api.SCSITarget{}
	s.mutex.RLock()
	defer s.mutex.RUnlock()
	for _, t := range s.Targets {
		result = append(result, t)
	}
	return result, nil
}

// Resize resize
func (s *SCSITargetService) Resize(size uint64) error {
	s.mutex.Lock()
	//TODO for multiple LUNs
	for _, t := range s.Targets {
		if t.Devices != nil {
			for i := range t.Devices {
				t.Devices[i].Size = size
			}
		}
	}
	s.mutex.Unlock()
	return nil
}

// AddCommandQueue add command queue
func (s *SCSITargetService) AddCommandQueue(tid int, scmd *api.SCSICommand) error {
	var (
		target *api.SCSITarget
		itn    *api.ITNexus
	)

	s.mutex.RLock()
	for _, t := range s.Targets {
		if t.TID == tid {
			target = t
			break
		}
	}
	s.mutex.RUnlock()
	if target == nil {
		return fmt.Errorf("Cannot find the target with ID(%d)", tid)
	}
	scmd.Target = target
	for _, it := range target.ITNexus {
		if it.ID == scmd.ITNexusID {
			itn = it
			break
		}
	}
	scmd.ITNexus = itn
	lun := *(*uint64)(unsafe.Pointer(&scmd.Lun))
	scmd.Device = target.Devices[lun]

	log.Debugf("scsi opcode: 0x%x, LUN: %d", int(scmd.SCB[0]), binary.LittleEndian.Uint64(scmd.Lun[:]))

	if scmd.Device == nil {
		scmd.Device = target.LUN0
		if lun != 0 {
			BuildSenseData(scmd, ILLEGAL_REQUEST, ASC_INVALID_FIELD_IN_CDB)
			scmd.Result = api.SAMStatCheckCondition.Stat
			log.Warnf("%v", api.SAMStatCheckCondition.Err)
			return nil
		}
	}

	result := scmd.Device.PerformCommand(tid, scmd)
	if result != api.SAMStatGood {
		scmd.Result = result.Stat
		log.Warnf("opcode: %xh err: %v", scmd.OpCode, result.Err)
	}
	return nil
}

// SCSIServiceAction SCSI service action
type SCSIServiceAction struct {
	ServiceAction      uint8
	CommandPerformFunc api.CommandFunc
}

// SCSIDeviceOperation SCSI device operation
type SCSIDeviceOperation struct {
	CommandPerformFunc api.CommandFunc
	ServiceAction      []*SCSIServiceAction
	PRConflictBits     uint8
}

// BaseSCSIDeviceProtocol base SCSI device protocol
type BaseSCSIDeviceProtocol struct {
	DeviceType    api.SCSIDeviceType
	SCSIDeviceOps []SCSIDeviceOperation
}

// NewSCSIDeviceOperation create a new SCSI device operation
func NewSCSIDeviceOperation(fn api.CommandFunc, sa []*SCSIServiceAction, pr uint8) SCSIDeviceOperation {
	return SCSIDeviceOperation{
		CommandPerformFunc: fn,
		ServiceAction:      sa,
		PRConflictBits:     pr,
	}
}

// BuildSenseData build sense data
func BuildSenseData(cmd *api.SCSICommand, key byte, asc SCSISubError) {
	senseBuffer := &bytes.Buffer{}
	inBufLen, ok := SCSICDBBufXLength(cmd.SCB)
	var (
		length      uint32 = 0xa
		fixedFormat bool   = true
	)

	if cmd.Device != nil {
		if cmd.Device.Attrs.SenseFormat {
			fixedFormat = false
		}
	}

	if !fixedFormat {
		// descriptor format
		// current, not deferred
		senseBuffer.WriteByte(0x72)
		senseBuffer.WriteByte(key)
		senseBuffer.WriteByte(byte(asc>>8) & 0xff)
		senseBuffer.WriteByte(byte(asc) & 0xff)
		length = 8
	} else {
		// fixed format
		// current, not deferred
		senseBuffer.WriteByte(0x70)
		senseBuffer.WriteByte(0x00)
		senseBuffer.WriteByte(key)
		for i := 0; i < 4; i++ {
			senseBuffer.WriteByte(0x00)
		}
		senseBuffer.WriteByte(byte(length))
		for i := 0; i < 4; i++ {
			senseBuffer.WriteByte(0x00)
		}
		senseBuffer.WriteByte(byte(asc>>8) & 0xff)
		senseBuffer.WriteByte(byte(asc) & 0xff)
		for i := 0; i < 4; i++ {
			senseBuffer.WriteByte(0x00)
		}
		length += 8
	}
	if ok {
		if int64(length) > inBufLen {
			log.Warnf("sense buffer is bigger than in buffer")
			senseBuffer.Truncate(int(inBufLen))
		}
	} else {
		log.Debugf("cannot calc cbd alloc length. truncate failed")
	}
	// Note: cmd.Result should be set by the caller, not here
	// The caller should set cmd.Result = api.SAM_STAT_CHECK_CONDITION when returning error
	cmd.SenseBuffer = &api.SenseBuffer{Buffer: senseBuffer.Bytes(), Length: length}
}

func getSCSIReadWriteOffset(scb []byte) uint64 {
	var off uint64
	var opcode = api.SCSICommandType(scb[0])

	switch opcode {
	case api.READ_6, api.WRITE_6:
		off = uint64((scb[1]&0x1f))<<16 + uint64(scb[2])<<8 + uint64(scb[3])
	case api.READ_10, api.PRE_FETCH_10, api.WRITE_10, api.VERIFY_10, api.WRITE_VERIFY, api.WRITE_SAME, api.SYNCHRONIZE_CACHE, api.READ_12, api.WRITE_12, api.VERIFY_12, api.WRITE_VERIFY_12:
		off = uint64(binary.BigEndian.Uint32(scb[2:]))
	case api.READ_16, api.PRE_FETCH_16, api.WRITE_16, api.ORWRITE_16, api.VERIFY_16, api.WRITE_VERIFY_16, api.WRITE_SAME_16, api.SYNCHRONIZE_CACHE_16, api.COMPARE_AND_WRITE:
		off = binary.BigEndian.Uint64(scb[2:])
	default:
	}

	return off
}

func getSCSIReadWriteCount(scb []byte) uint32 {
	var cnt uint32
	var opcode = api.SCSICommandType(scb[0])

	switch opcode {
	case api.READ_6, api.WRITE_6:
		cnt = uint32(scb[4])
		if cnt == 0 {
			cnt = 256
		}
	case api.READ_10, api.PRE_FETCH_10, api.WRITE_10, api.VERIFY_10, api.WRITE_VERIFY, api.WRITE_SAME, api.SYNCHRONIZE_CACHE:
		cnt = uint32(scb[7])<<8 | uint32(scb[8])
	case api.READ_12, api.WRITE_12, api.VERIFY_12, api.WRITE_VERIFY_12:
		cnt = binary.BigEndian.Uint32(scb[6:])
		// Note: READ(12)/WRITE(12) have 32-bit transfer length field, but only use lower 16 bits
		// per SCSI SBC-3 spec. Zero means zero blocks.
	case api.READ_16, api.PRE_FETCH_16, api.WRITE_16, api.ORWRITE_16, api.VERIFY_16, api.WRITE_VERIFY_16, api.WRITE_SAME_16, api.SYNCHRONIZE_CACHE_16:
		cnt = binary.BigEndian.Uint32(scb[10:])
	case api.COMPARE_AND_WRITE:
		cnt = uint32(scb[13])
	default:
	}

	return cnt
}