package proc

import (
	"bytes"
	"debug/dwarf"
	"encoding/binary"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"reflect"
	"strconv"
	"strings"
	"unsafe"

	"github.com/derekparker/delve/dwarf/op"
	"github.com/derekparker/delve/dwarf/reader"
)

const (
	maxVariableRecurse = 1  // How far to recurse when evaluating nested types.
	maxArrayValues     = 64 // Max value for reading large arrays.
	maxErrCount        = 3  // Max number of read errors to accept while evaluating slices, arrays and structs

	ChanRecv = "chan receive"
	ChanSend = "chan send"
)

// Represents a variable.
type Variable struct {
	Addr      uintptr
	Name      string
	DwarfType dwarf.Type
	RealType  dwarf.Type
	Kind      reflect.Kind
	thread    *Thread

	Value interface{}

	Len int64
	Cap int64

	base      uintptr
	stride    int64
	fieldType dwarf.Type

	Children []Variable

	loaded     bool
	Unreadable error
}

// Represents a runtime M (OS thread) structure.
type M struct {
	procid   int     // Thread ID or port.
	spinning uint8   // Busy looping.
	blocked  uint8   // Waiting on futex / semaphore.
	curg     uintptr // Current G running on this thread.
}

const (
	// G status, from: src/runtime/runtime2.go
	Gidle            uint64 = iota // 0
	Grunnable                      // 1 runnable and on a run queue
	Grunning                       // 2
	Gsyscall                       // 3
	Gwaiting                       // 4
	Gmoribund_unused               // 5 currently unused, but hardcoded in gdb scripts
	Gdead                          // 6
	Genqueue                       // 7 Only the Gscanenqueue is used.
	Gcopystack                     // 8 in this state when newstack is moving the stack
)

// Represents a runtime G (goroutine) structure (at least the
// fields that Delve is interested in).
type G struct {
	Id         int    // Goroutine ID
	PC         uint64 // PC of goroutine when it was parked.
	SP         uint64 // SP of goroutine when it was parked.
	GoPC       uint64 // PC of 'go' statement that created this goroutine.
	WaitReason string // Reason for goroutine being parked.
	Status     uint64

	// Information on goroutine location
	CurrentLoc Location

	// PC of entry to top-most deferred function.
	DeferPC uint64

	// Thread that this goroutine is currently allocated to
	thread *Thread

	dbp *Process
}

// Scope for variable evaluation
type EvalScope struct {
	Thread *Thread
	PC     uint64
	CFA    int64
}

func newVariable(name string, addr uintptr, dwarfType dwarf.Type, thread *Thread) *Variable {
	v := &Variable{
		Name:      name,
		Addr:      addr,
		DwarfType: dwarfType,
		thread:    thread,
	}

	v.RealType = v.DwarfType
	for {
		if tt, ok := v.RealType.(*dwarf.TypedefType); ok {
			v.RealType = tt.Type
		} else {
			break
		}
	}

	switch t := v.RealType.(type) {
	case *dwarf.PtrType:
		v.Kind = reflect.Ptr
	case *dwarf.StructType:
		switch {
		case t.StructName == "string":
			v.Kind = reflect.String
		case strings.HasPrefix(t.StructName, "[]"):
			v.Kind = reflect.Slice
			if v.Addr != 0 {
				v.loadSliceInfo(t)
			}
		default:
			v.Kind = reflect.Struct
		}
	case *dwarf.ArrayType:
		v.Kind = reflect.Array
		v.base = v.Addr
		v.Len = t.Count
		v.Cap = -1
		v.fieldType = t.Type
		v.stride = 0

		if t.Count > 0 {
			v.stride = t.ByteSize / t.Count
		}
	case *dwarf.ComplexType:
		switch t.ByteSize {
		case 8:
			v.Kind = reflect.Complex64
		case 16:
			v.Kind = reflect.Complex128
		}
	case *dwarf.IntType:
		v.Kind = reflect.Int
	case *dwarf.UintType:
		v.Kind = reflect.Uint
	case *dwarf.FloatType:
		switch t.ByteSize {
		case 4:
			v.Kind = reflect.Float32
		case 8:
			v.Kind = reflect.Float64
		}
	case *dwarf.BoolType:
		v.Kind = reflect.Bool
	case *dwarf.FuncType:
		v.Kind = reflect.Func
	case *dwarf.VoidType:
		v.Kind = reflect.Invalid
	case *dwarf.UnspecifiedType:
		v.Kind = reflect.Invalid
	default:
		v.Unreadable = fmt.Errorf("Unknown type: %T", t)
	}

	return v
}

func (v *Variable) clone() *Variable {
	r := *v
	return &r
}

func (v *Variable) toField(field *dwarf.StructField) (*Variable, error) {
	if v.Unreadable != nil {
		return v.clone(), nil
	}
	if v.Addr == 0 {
		return nil, fmt.Errorf("%s is nil", v.Name)
	}

	name := ""
	if v.Name != "" {
		parts := strings.Split(field.Name, ".")
		if len(parts) > 1 {
			name = fmt.Sprintf("%s.%s", v.Name, parts[1])
		} else {
			name = fmt.Sprintf("%s.%s", v.Name, field.Name)
		}
	}
	return newVariable(name, uintptr(int64(v.Addr)+field.ByteOffset), field.Type, v.thread), nil
}

func (scope *EvalScope) DwarfReader() *reader.Reader {
	return scope.Thread.dbp.DwarfReader()
}

func (scope *EvalScope) Type(offset dwarf.Offset) (dwarf.Type, error) {
	return scope.Thread.dbp.dwarf.Type(offset)
}

func (scope *EvalScope) PtrSize() int {
	return scope.Thread.dbp.arch.PtrSize()
}

// Returns whether the goroutine is blocked on
// a channel read operation.
func (g *G) ChanRecvBlocked() bool {
	return g.WaitReason == ChanRecv
}

// chanRecvReturnAddr returns the address of the return from a channel read.
func (g *G) chanRecvReturnAddr(dbp *Process) (uint64, error) {
	locs, err := dbp.GoroutineStacktrace(g, 4)
	if err != nil {
		return 0, err
	}
	topLoc := locs[len(locs)-1]
	return topLoc.Current.PC, nil
}

// NoGError returned when a G could not be found
// for a specific thread.
type NoGError struct {
	tid int
}

func (ng NoGError) Error() string {
	return fmt.Sprintf("no G executing on thread %d", ng.tid)
}

func parseG(thread *Thread, gaddr uint64, deref bool) (*G, error) {
	initialInstructions := make([]byte, thread.dbp.arch.PtrSize()+1)
	initialInstructions[0] = op.DW_OP_addr
	binary.LittleEndian.PutUint64(initialInstructions[1:], gaddr)
	if deref {
		gaddrbytes, err := thread.readMemory(uintptr(gaddr), thread.dbp.arch.PtrSize())
		if err != nil {
			return nil, fmt.Errorf("error derefing *G %s", err)
		}
		initialInstructions = append([]byte{op.DW_OP_addr}, gaddrbytes...)
		gaddr = binary.LittleEndian.Uint64(gaddrbytes)
		if gaddr == 0 {
			return nil, NoGError{tid: thread.Id}
		}
	}

	rdr := thread.dbp.DwarfReader()
	rdr.Seek(0)
	entry, err := rdr.SeekToTypeNamed("runtime.g")
	if err != nil {
		return nil, err
	}

	// Parse defer
	deferAddr, err := rdr.AddrForMember("_defer", initialInstructions)
	if err != nil {
		return nil, err
	}
	var deferPC uint64
	// Dereference *defer pointer
	deferAddrBytes, err := thread.readMemory(uintptr(deferAddr), thread.dbp.arch.PtrSize())
	if err != nil {
		return nil, fmt.Errorf("error derefing defer %s", err)
	}
	if binary.LittleEndian.Uint64(deferAddrBytes) != 0 {
		initialDeferInstructions := append([]byte{op.DW_OP_addr}, deferAddrBytes...)
		_, err = rdr.SeekToTypeNamed("runtime._defer")
		if err != nil {
			return nil, err
		}
		deferPCAddr, err := rdr.AddrForMember("fn", initialDeferInstructions)
		deferPC, err = thread.readUintRaw(uintptr(deferPCAddr), 8)
		if err != nil {
			return nil, err
		}
		deferPC, err = thread.readUintRaw(uintptr(deferPC), 8)
		if err != nil {
			return nil, err
		}
	}

	// Let's parse all of the members we care about in order so that
	// we don't have to spend any extra time seeking.

	err = rdr.SeekToEntry(entry)
	if err != nil {
		return nil, err
	}

	// Parse sched
	schedAddr, err := rdr.AddrForMember("sched", initialInstructions)
	if err != nil {
		return nil, err
	}
	// From sched, let's parse PC and SP.
	sp, err := thread.readUintRaw(uintptr(schedAddr), 8)
	if err != nil {
		return nil, err
	}
	pc, err := thread.readUintRaw(uintptr(schedAddr+uint64(thread.dbp.arch.PtrSize())), 8)
	if err != nil {
		return nil, err
	}
	// Parse atomicstatus
	atomicStatusAddr, err := rdr.AddrForMember("atomicstatus", initialInstructions)
	if err != nil {
		return nil, err
	}
	atomicStatus, err := thread.readUintRaw(uintptr(atomicStatusAddr), 4)
	// Parse goid
	goidAddr, err := rdr.AddrForMember("goid", initialInstructions)
	if err != nil {
		return nil, err
	}
	goid, err := thread.readIntRaw(uintptr(goidAddr), 8)
	if err != nil {
		return nil, err
	}
	// Parse waitreason
	waitReasonAddr, err := rdr.AddrForMember("waitreason", initialInstructions)
	if err != nil {
		return nil, err
	}
	waitreason, _, err := thread.readString(uintptr(waitReasonAddr))
	if err != nil {
		return nil, err
	}
	// Parse gopc
	gopcAddr, err := rdr.AddrForMember("gopc", initialInstructions)
	if err != nil {
		return nil, err
	}
	gopc, err := thread.readUintRaw(uintptr(gopcAddr), 8)
	if err != nil {
		return nil, err
	}

	f, l, fn := thread.dbp.goSymTable.PCToLine(pc)
	g := &G{
		Id:         int(goid),
		GoPC:       gopc,
		PC:         pc,
		SP:         sp,
		CurrentLoc: Location{PC: pc, File: f, Line: l, Fn: fn},
		WaitReason: waitreason,
		DeferPC:    deferPC,
		Status:     atomicStatus,
		dbp:        thread.dbp,
	}
	return g, nil
}

// From $GOROOT/src/runtime/traceback.go:597
// isExportedRuntime reports whether name is an exported runtime function.
// It is only for runtime functions, so ASCII A-Z is fine.
func isExportedRuntime(name string) bool {
	const n = len("runtime.")
	return len(name) > n && name[:n] == "runtime." && 'A' <= name[n] && name[n] <= 'Z'
}

func (g *G) UserCurrent() Location {
	pc, sp := g.PC, g.SP
	if g.thread != nil {
		regs, err := g.thread.Registers()
		if err != nil {
			return g.CurrentLoc
		}
		pc, sp = regs.PC(), regs.SP()
	}
	it := newStackIterator(g.dbp, pc, sp)
	for it.Next() {
		frame := it.Frame()
		name := frame.Call.Fn.Name
		if (strings.Index(name, ".") >= 0) && (!strings.HasPrefix(name, "runtime.") || isExportedRuntime(name)) {
			return frame.Call
		}
	}
	return g.CurrentLoc
}

func (g *G) Go() Location {
	f, l, fn := g.dbp.goSymTable.PCToLine(g.GoPC)
	return Location{PC: g.GoPC, File: f, Line: l, Fn: fn}
}

// Returns information for the named variable.
func (scope *EvalScope) ExtractVariableInfo(name string) (*Variable, error) {
	parts := strings.Split(name, ".")
	varName := parts[0]
	memberNames := parts[1:]

	v, err := scope.extractVarInfo(varName)
	if err != nil {
		origErr := err
		// Attempt to evaluate name as a package variable.
		if len(memberNames) > 0 {
			v, err = scope.packageVarAddr(name)
		} else {
			_, _, fn := scope.Thread.dbp.PCToLine(scope.PC)
			if fn != nil {
				v, err = scope.packageVarAddr(fn.PackageName() + "." + name)
			}
		}
		if err != nil {
			return nil, origErr
		}
		v.Name = name
		return v, nil
	} else {
		if len(memberNames) > 0 {
			for i := range memberNames {
				v, err = v.structMember(memberNames[i])
				if err != nil {
					return nil, err
				}
			}
		}
	}
	return v, nil
}

// Returns the value of the named variable.
func (scope *EvalScope) EvalVariable(name string) (*Variable, error) {
	v, err := scope.ExtractVariableInfo(name)
	if err != nil {
		return nil, err
	}
	v.loadValue()
	return v, nil
}

// Sets the value of the named variable
func (scope *EvalScope) SetVariable(name, value string) error {
	v, err := scope.ExtractVariableInfo(name)
	if err != nil {
		return err
	}
	if v.Unreadable != nil {
		return fmt.Errorf("Variable \"%s\" is unreadable: %v\n", name, v.Unreadable)
	}
	return v.setValue(value)
}

func (scope *EvalScope) extractVariableFromEntry(entry *dwarf.Entry) (*Variable, error) {
	rdr := scope.DwarfReader()
	v, err := scope.extractVarInfoFromEntry(entry, rdr)
	if err != nil {
		return nil, err
	}
	v.loadValue()
	return v, nil
}

func (scope *EvalScope) extractVarInfo(varName string) (*Variable, error) {
	reader := scope.DwarfReader()

	_, err := reader.SeekToFunction(scope.PC)
	if err != nil {
		return nil, err
	}

	for entry, err := reader.NextScopeVariable(); entry != nil; entry, err = reader.NextScopeVariable() {
		if err != nil {
			return nil, err
		}

		n, ok := entry.Val(dwarf.AttrName).(string)
		if !ok {
			continue
		}

		if n == varName {
			return scope.extractVarInfoFromEntry(entry, reader)
		}
	}
	return nil, fmt.Errorf("could not find symbol value for %s", varName)
}

// LocalVariables returns all local variables from the current function scope.
func (scope *EvalScope) LocalVariables() ([]*Variable, error) {
	return scope.variablesByTag(dwarf.TagVariable)
}

// FunctionArguments returns the name, value, and type of all current function arguments.
func (scope *EvalScope) FunctionArguments() ([]*Variable, error) {
	return scope.variablesByTag(dwarf.TagFormalParameter)
}

// PackageVariables returns the name, value, and type of all package variables in the application.
func (scope *EvalScope) PackageVariables() ([]*Variable, error) {
	reader := scope.DwarfReader()

	vars := make([]*Variable, 0)

	for entry, err := reader.NextPackageVariable(); entry != nil; entry, err = reader.NextPackageVariable() {
		if err != nil {
			return nil, err
		}

		// Ignore errors trying to extract values
		val, err := scope.extractVariableFromEntry(entry)
		if err != nil {
			continue
		}
		vars = append(vars, val)
	}

	return vars, nil
}

func (dbp *Process) EvalPackageVariable(name string) (*Variable, error) {
	scope := &EvalScope{Thread: dbp.CurrentThread, PC: 0, CFA: 0}

	v, err := scope.packageVarAddr(name)
	if err != nil {
		return nil, err
	}
	v.loadValue()
	return v, nil
}

func (scope *EvalScope) packageVarAddr(name string) (*Variable, error) {
	reader := scope.DwarfReader()
	for entry, err := reader.NextPackageVariable(); entry != nil; entry, err = reader.NextPackageVariable() {
		if err != nil {
			return nil, err
		}

		n, ok := entry.Val(dwarf.AttrName).(string)
		if !ok {
			continue
		}

		if n == name {
			return scope.extractVarInfoFromEntry(entry, reader)
		}
	}
	return nil, fmt.Errorf("could not find symbol value for %s", name)
}

func (v *Variable) structMember(memberName string) (*Variable, error) {
	if v.Unreadable != nil {
		return v.clone(), nil
	}
	structVar := v.maybeDereference()
	structVar.Name = v.Name
	if structVar.Unreadable != nil {
		return structVar, nil
	}

	switch t := structVar.RealType.(type) {
	case *dwarf.StructType:
		for _, field := range t.Field {
			if field.Name != memberName {
				continue
			}
			return structVar.toField(field)
		}
		// Check for embedded field only if field was
		// not a regular struct member
		for _, field := range t.Field {
			isEmbeddedStructMember :=
				(field.Type.String() == ("struct " + field.Name)) ||
					(len(field.Name) > 1 &&
						field.Name[0] == '*' &&
						field.Type.String()[1:] == ("struct "+field.Name[1:]))
			if !isEmbeddedStructMember {
				continue
			}
			// Check for embedded field referenced by type name
			parts := strings.Split(field.Name, ".")
			if len(parts) > 1 && parts[1] == memberName {
				embeddedVar, err := structVar.toField(field)
				if err != nil {
					return nil, err
				}
				return embeddedVar, nil
			}
			// Recursively check for promoted fields on the embedded field
			embeddedVar, err := structVar.toField(field)
			if err != nil {
				return nil, err
			}
			embeddedVar.Name = structVar.Name
			embeddedField, err := embeddedVar.structMember(memberName)
			if embeddedField != nil {
				return embeddedField, nil
			}
		}
		return nil, fmt.Errorf("%s has no member %s", v.Name, memberName)
	default:
		return nil, fmt.Errorf("%s type %s is not a struct", v.Name, structVar.DwarfType)
	}
}

// Extracts the name and type of a variable from a dwarf entry
// then executes the instructions given in the  DW_AT_location attribute to grab the variable's address
func (scope *EvalScope) extractVarInfoFromEntry(entry *dwarf.Entry, rdr *reader.Reader) (*Variable, error) {
	if entry == nil {
		return nil, fmt.Errorf("invalid entry")
	}

	if entry.Tag != dwarf.TagFormalParameter && entry.Tag != dwarf.TagVariable {
		return nil, fmt.Errorf("invalid entry tag, only supports FormalParameter and Variable, got %s", entry.Tag.String())
	}

	n, ok := entry.Val(dwarf.AttrName).(string)
	if !ok {
		return nil, fmt.Errorf("type assertion failed")
	}

	offset, ok := entry.Val(dwarf.AttrType).(dwarf.Offset)
	if !ok {
		return nil, fmt.Errorf("type assertion failed")
	}

	t, err := scope.Type(offset)
	if err != nil {
		return nil, err
	}

	instructions, ok := entry.Val(dwarf.AttrLocation).([]byte)
	if !ok {
		return nil, fmt.Errorf("type assertion failed")
	}

	addr, err := op.ExecuteStackProgram(scope.CFA, instructions)
	if err != nil {
		return nil, err
	}

	return newVariable(n, uintptr(addr), t, scope.Thread), nil
}

// If v is a pointer a new variable is returned containing the value pointed by v.
func (v *Variable) maybeDereference() *Variable {
	if v.Unreadable != nil {
		return v
	}

	switch t := v.RealType.(type) {
	case *dwarf.PtrType:
		ptrval, err := v.thread.readUintRaw(uintptr(v.Addr), int64(v.thread.dbp.arch.PtrSize()))
		r := newVariable("", uintptr(ptrval), t.Type, v.thread)
		if err != nil {
			r.Unreadable = err
		}

		return r
	default:
		return v
	}
}

// Extracts the value of the variable at the given address.
func (v *Variable) loadValue() {
	v.loadValueInternal(0)
}

func (v *Variable) loadValueInternal(recurseLevel int) {
	if v.Unreadable != nil || v.loaded || v.Addr == 0 {
		return
	}
	v.loaded = true
	switch v.Kind {
	case reflect.Ptr:
		v.Len = 1
		v.Children = []Variable{*v.maybeDereference()}
		// Don't increase the recursion level when dereferencing pointers
		v.Children[0].loadValueInternal(recurseLevel)

	case reflect.String:
		v.Value, v.Len, v.Unreadable = v.thread.readString(uintptr(v.Addr))

	case reflect.Slice, reflect.Array:
		v.loadArrayValues(recurseLevel)

	case reflect.Struct:
		t := v.RealType.(*dwarf.StructType)
		v.Len = int64(len(t.Field))
		// Recursively call extractValue to grab
		// the value of all the members of the struct.
		if recurseLevel <= maxVariableRecurse {
			v.Children = make([]Variable, 0, len(t.Field))
			for i, field := range t.Field {
				f, _ := v.toField(field)
				v.Children = append(v.Children, *f)
				v.Children[i].Name = field.Name
				v.Children[i].loadValueInternal(recurseLevel + 1)
			}
		}

	case reflect.Complex64, reflect.Complex128:
		v.readComplex(v.RealType.(*dwarf.ComplexType).ByteSize)
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		v.Value, v.Unreadable = v.thread.readIntRaw(v.Addr, v.RealType.(*dwarf.IntType).ByteSize)
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		v.Value, v.Unreadable = v.thread.readUintRaw(v.Addr, v.RealType.(*dwarf.UintType).ByteSize)
	case reflect.Bool:
		val, err := v.thread.readMemory(v.Addr, 1)
		v.Unreadable = err
		if err == nil {
			v.Value = val[0] != 0
		}
	case reflect.Float32, reflect.Float64:
		v.Value, v.Unreadable = v.readFloatRaw(v.RealType.(*dwarf.FloatType).ByteSize)
	case reflect.Func:
		v.readFunctionPtr()
	case reflect.Map:
		fallthrough
	default:
		v.Unreadable = fmt.Errorf("unknown or unsupported kind: \"%s\"", v.Kind.String())
	}
}

func (v *Variable) setValue(value string) error {
	switch t := v.RealType.(type) {
	case *dwarf.PtrType:
		return v.writeUint(false, value, int64(v.thread.dbp.arch.PtrSize()))
	case *dwarf.ComplexType:
		return v.writeComplex(value, t.ByteSize)
	case *dwarf.IntType:
		return v.writeUint(true, value, t.ByteSize)
	case *dwarf.UintType:
		return v.writeUint(false, value, t.ByteSize)
	case *dwarf.FloatType:
		return v.writeFloat(value, t.ByteSize)
	case *dwarf.BoolType:
		return v.writeBool(value)
	default:
		return fmt.Errorf("Can not set value of variables of kind: %s\n", v.RealType.String())
	}
}

func (thread *Thread) readString(addr uintptr) (string, int64, error) {
	// string data structure is always two ptrs in size. Addr, followed by len
	// http://research.swtch.com/godata

	// read len
	val, err := thread.readMemory(addr+uintptr(thread.dbp.arch.PtrSize()), thread.dbp.arch.PtrSize())
	if err != nil {
		return "", 0, fmt.Errorf("could not read string len %s", err)
	}
	strlen := int64(binary.LittleEndian.Uint64(val))
	if strlen < 0 {
		return "", 0, fmt.Errorf("invalid length: %d", strlen)
	}

	count := strlen
	if count > maxArrayValues {
		count = maxArrayValues
	}

	// read addr
	val, err = thread.readMemory(addr, thread.dbp.arch.PtrSize())
	if err != nil {
		return "", 0, fmt.Errorf("could not read string pointer %s", err)
	}
	addr = uintptr(binary.LittleEndian.Uint64(val))
	if addr == 0 {
		return "", 0, nil
	}

	val, err = thread.readMemory(addr, int(count))
	if err != nil {
		return "", 0, fmt.Errorf("could not read string at %#v due to %s", addr, err)
	}

	retstr := *(*string)(unsafe.Pointer(&val))

	return retstr, strlen, nil
}

func (v *Variable) loadSliceInfo(t *dwarf.StructType) {
	var err error
	for _, f := range t.Field {
		switch f.Name {
		case "array":
			var base uint64
			base, err = v.thread.readUintRaw(uintptr(int64(v.Addr)+f.ByteOffset), int64(v.thread.dbp.arch.PtrSize()))
			if err == nil {
				v.base = uintptr(base)
				// Dereference array type to get value type
				ptrType, ok := f.Type.(*dwarf.PtrType)
				if !ok {
					v.Unreadable = fmt.Errorf("Invalid type %s in slice array", f.Type)
					return
				}
				v.fieldType = ptrType.Type
			}
		case "len":
			lstrAddr, _ := v.toField(f)
			lstrAddr.loadValue()
			err = lstrAddr.Unreadable
			if err == nil {
				v.Len = lstrAddr.Value.(int64)
			}
		case "cap":
			cstrAddr, _ := v.toField(f)
			cstrAddr.loadValue()
			err = cstrAddr.Unreadable
			if err == nil {
				v.Cap = cstrAddr.Value.(int64)
			}
		}
		if err != nil {
			v.Unreadable = err
			return
		}
	}

	v.stride = v.fieldType.Size()
	if _, ok := v.fieldType.(*dwarf.PtrType); ok {
		v.stride = int64(v.thread.dbp.arch.PtrSize())
	}

	return
}

func (v *Variable) loadArrayValues(recurseLevel int) {
	if v.Unreadable != nil {
		return
	}

	errcount := 0

	for i := int64(0); i < v.Len; i++ {
		// Cap number of elements
		if i >= maxArrayValues {
			break
		}

		fieldvar := newVariable("", uintptr(int64(v.base)+(i*v.stride)), v.fieldType, v.thread)
		fieldvar.loadValueInternal(recurseLevel + 1)

		if fieldvar.Unreadable != nil {
			errcount++
		}

		v.Children = append(v.Children, *fieldvar)
		if errcount > maxErrCount {
			break
		}
	}
}

func (v *Variable) readComplex(size int64) {
	var fs int64
	switch size {
	case 8:
		fs = 4
	case 16:
		fs = 8
	default:
		v.Unreadable = fmt.Errorf("invalid size (%d) for complex type", size)
		return
	}

	ftyp := &dwarf.FloatType{BasicType: dwarf.BasicType{CommonType: dwarf.CommonType{ByteSize: fs, Name: fmt.Sprintf("float%d", fs)}, BitSize: fs * 8, BitOffset: 0}}

	realvar := newVariable("real", v.Addr, ftyp, v.thread)
	imagvar := newVariable("imaginary", v.Addr+uintptr(fs), ftyp, v.thread)
	realvar.loadValue()
	imagvar.loadValue()
	v.Len = 2
	v.Children = []Variable{*realvar, *imagvar}
}

func (v *Variable) writeComplex(value string, size int64) error {
	var real, imag float64

	expr, err := parser.ParseExpr(value)
	if err != nil {
		return err
	}

	var lits []*ast.BasicLit

	if e, ok := expr.(*ast.ParenExpr); ok {
		expr = e.X
	}

	switch e := expr.(type) {
	case *ast.BinaryExpr: // "<float> + <float>i" or "<float>i + <float>"
		x, xok := e.X.(*ast.BasicLit)
		y, yok := e.Y.(*ast.BasicLit)
		if e.Op != token.ADD || !xok || !yok {
			return fmt.Errorf("Not a complex constant: %s", value)
		}
		lits = []*ast.BasicLit{x, y}
	case *ast.CallExpr: // "complex(<float>, <float>)"
		tname, ok := e.Fun.(*ast.Ident)
		if !ok {
			return fmt.Errorf("Not a complex constant: %s", value)
		}
		if (tname.Name != "complex64") && (tname.Name != "complex128") {
			return fmt.Errorf("Not a complex constant: %s", value)
		}
		if len(e.Args) != 2 {
			return fmt.Errorf("Not a complex constant: %s", value)
		}
		for i := range e.Args {
			lit, ok := e.Args[i].(*ast.BasicLit)
			if !ok {
				return fmt.Errorf("Not a complex constant: %s", value)
			}
			lits = append(lits, lit)
		}
		lits[1].Kind = token.IMAG
		lits[1].Value = lits[1].Value + "i"
	case *ast.BasicLit: // "<float>" or "<float>i"
		lits = []*ast.BasicLit{e}
	default:
		return fmt.Errorf("Not a complex constant: %s", value)
	}

	for _, lit := range lits {
		var err error
		var v float64
		switch lit.Kind {
		case token.FLOAT, token.INT:
			v, err = strconv.ParseFloat(lit.Value, int(size/2))
			real += v
		case token.IMAG:
			v, err = strconv.ParseFloat(lit.Value[:len(lit.Value)-1], int(size/2))
			imag += v
		default:
			return fmt.Errorf("Not a complex constant: %s", value)
		}
		if err != nil {
			return err
		}
	}

	err = v.writeFloatRaw(real, int64(size/2))
	if err != nil {
		return err
	}
	imagaddr := *v
	imagaddr.Addr += uintptr(size / 2)
	return imagaddr.writeFloatRaw(imag, int64(size/2))
}

func (thread *Thread) readIntRaw(addr uintptr, size int64) (int64, error) {
	var n int64

	val, err := thread.readMemory(addr, int(size))
	if err != nil {
		return 0, err
	}

	switch size {
	case 1:
		n = int64(val[0])
	case 2:
		n = int64(binary.LittleEndian.Uint16(val))
	case 4:
		n = int64(binary.LittleEndian.Uint32(val))
	case 8:
		n = int64(binary.LittleEndian.Uint64(val))
	}

	return n, nil
}

func (v *Variable) writeUint(signed bool, value string, size int64) error {
	var (
		n   uint64
		err error
	)
	if signed {
		var m int64
		m, err = strconv.ParseInt(value, 0, int(size*8))
		n = uint64(m)
	} else {
		n, err = strconv.ParseUint(value, 0, int(size*8))
	}
	if err != nil {
		return err
	}

	val := make([]byte, size)

	switch size {
	case 1:
		val[0] = byte(n)
	case 2:
		binary.LittleEndian.PutUint16(val, uint16(n))
	case 4:
		binary.LittleEndian.PutUint32(val, uint32(n))
	case 8:
		binary.LittleEndian.PutUint64(val, uint64(n))
	}

	_, err = v.thread.writeMemory(v.Addr, val)
	return err
}

func (thread *Thread) readUintRaw(addr uintptr, size int64) (uint64, error) {
	var n uint64

	val, err := thread.readMemory(addr, int(size))
	if err != nil {
		return 0, err
	}

	switch size {
	case 1:
		n = uint64(val[0])
	case 2:
		n = uint64(binary.LittleEndian.Uint16(val))
	case 4:
		n = uint64(binary.LittleEndian.Uint32(val))
	case 8:
		n = uint64(binary.LittleEndian.Uint64(val))
	}

	return n, nil
}

func (v *Variable) readFloatRaw(size int64) (float64, error) {
	val, err := v.thread.readMemory(v.Addr, int(size))
	if err != nil {
		return 0.0, err
	}
	buf := bytes.NewBuffer(val)

	switch size {
	case 4:
		n := float32(0)
		binary.Read(buf, binary.LittleEndian, &n)
		return float64(n), nil
	case 8:
		n := float64(0)
		binary.Read(buf, binary.LittleEndian, &n)
		return n, nil
	}

	return 0.0, fmt.Errorf("could not read float")
}

func (v *Variable) writeFloat(value string, size int64) error {
	f, err := strconv.ParseFloat(value, int(size*8))
	if err != nil {
		return err
	}
	return v.writeFloatRaw(f, size)
}

func (v *Variable) writeFloatRaw(f float64, size int64) error {
	buf := bytes.NewBuffer(make([]byte, 0, size))

	switch size {
	case 4:
		n := float32(f)
		binary.Write(buf, binary.LittleEndian, n)
	case 8:
		n := float64(f)
		binary.Write(buf, binary.LittleEndian, n)
	}

	_, err := v.thread.writeMemory(v.Addr, buf.Bytes())
	return err
}

func (v *Variable) writeBool(value string) error {
	b, err := strconv.ParseBool(value)
	if err != nil {
		return err
	}
	val := []byte{0}
	if b {
		val[0] = *(*byte)(unsafe.Pointer(&b))
	}
	_, err = v.thread.writeMemory(v.Addr, val)
	return err
}

func (v *Variable) readFunctionPtr() {
	val, err := v.thread.readMemory(v.Addr, v.thread.dbp.arch.PtrSize())
	if err != nil {
		v.Unreadable = err
		return
	}

	// dereference pointer to find function pc
	fnaddr := uintptr(binary.LittleEndian.Uint64(val))
	if fnaddr == 0 {
		v.Unreadable = err
		return
	}

	val, err = v.thread.readMemory(fnaddr, v.thread.dbp.arch.PtrSize())
	if err != nil {
		v.Unreadable = err
		return
	}

	funcAddr := binary.LittleEndian.Uint64(val)
	fn := v.thread.dbp.goSymTable.PCToFunc(uint64(funcAddr))
	if fn == nil {
		v.Unreadable = fmt.Errorf("could not find function for %#v", funcAddr)
		return
	}

	v.Value = fn.Name
}

// Fetches all variables of a specific type in the current function scope
func (scope *EvalScope) variablesByTag(tag dwarf.Tag) ([]*Variable, error) {
	reader := scope.DwarfReader()

	_, err := reader.SeekToFunction(scope.PC)
	if err != nil {
		return nil, err
	}

	vars := make([]*Variable, 0)

	for entry, err := reader.NextScopeVariable(); entry != nil; entry, err = reader.NextScopeVariable() {
		if err != nil {
			return nil, err
		}

		if entry.Tag == tag {
			val, err := scope.extractVariableFromEntry(entry)
			if err != nil {
				// skip variables that we can't parse yet
				continue
			}

			vars = append(vars, val)
		}
	}

	return vars, nil
}