package main

import (
	"fmt"
	"log"
	"strings"
)

type Field interface {
	Initialize(p *Protocol)
	SrcName() string
	XmlName() string
	SrcType() string
	Size() Size

	Define(c *Context)
	Read(c *Context, prefix string)
	Write(c *Context, prefix string)
}

func (pad *PadField) Initialize(p *Protocol) {}

type PadField struct {
	Bytes uint
}

func (p *PadField) SrcName() string {
	panic("illegal to take source name of a pad field")
}

func (p *PadField) XmlName() string {
	panic("illegal to take XML name of a pad field")
}

func (f *PadField) SrcType() string {
	panic("it is illegal to call SrcType on a PadField field")
}

func (p *PadField) Size() Size {
	return newFixedSize(p.Bytes)
}

type SingleField struct {
	srcName string
	xmlName string
	Type    Type
}

func (f *SingleField) Initialize(p *Protocol) {
	f.srcName = SrcName(f.XmlName())
	f.Type = f.Type.(*Translation).RealType(p)
}

func (f *SingleField) SrcName() string {
	return f.srcName
}

func (f *SingleField) XmlName() string {
	return f.xmlName
}

func (f *SingleField) SrcType() string {
	return f.Type.SrcName()
}

func (f *SingleField) Size() Size {
	return f.Type.Size()
}

type ListField struct {
	srcName    string
	xmlName    string
	Type       Type
	LengthExpr Expression
}

func (f *ListField) SrcName() string {
	return f.srcName
}

func (f *ListField) XmlName() string {
	return f.xmlName
}

func (f *ListField) SrcType() string {
	if strings.ToLower(f.Type.XmlName()) == "char" {
		return fmt.Sprintf("string")
	}
	return fmt.Sprintf("[]%s", f.Type.SrcName())
}

func (f *ListField) Length() Size {
	if f.LengthExpr == nil {
		return newExpressionSize(&Function{
			Name: "len",
			Expr: &FieldRef{
				Name: f.SrcName(),
			},
		})
	}
	return newExpressionSize(f.LengthExpr)
}

func (f *ListField) Size() Size {
	simpleLen := &Function{
		Name: "pad",
		Expr: newBinaryOp("*", f.Length().Expression, f.Type.Size().Expression),
	}

	switch field := f.Type.(type) {
	case *Struct:
		if field.HasList() {
			sizeFun := &Function{
				Name: fmt.Sprintf("%sListSize", f.Type.SrcName()),
				Expr: &FieldRef{Name: f.SrcName()},
			}
			return newExpressionSize(sizeFun)
		} else {
			return newExpressionSize(simpleLen)
		}
	case *Union:
		return newExpressionSize(simpleLen)
		// sizeFun := &Function{ 
			// Name: fmt.Sprintf("%sListSize", f.Type.SrcName()), 
			// Expr: &FieldRef{Name: f.SrcName()}, 
		// } 
		// return newExpressionSize(sizeFun) 
	case *Base:
		return newExpressionSize(simpleLen)
	case *Resource:
		return newExpressionSize(simpleLen)
	case *TypeDef:
		return newExpressionSize(simpleLen)
	default:
		log.Panicf("Cannot compute list size with type '%T'.", f.Type)
	}
	panic("unreachable")
}

func (f *ListField) Initialize(p *Protocol) {
	f.srcName = SrcName(f.XmlName())
	f.Type = f.Type.(*Translation).RealType(p)
	if f.LengthExpr != nil {
		f.LengthExpr.Initialize(p)
	}
}

type LocalField struct {
	*SingleField
}

type ExprField struct {
	srcName string
	xmlName string
	Type    Type
	Expr    Expression
}

func (f *ExprField) SrcName() string {
	return f.srcName
}

func (f *ExprField) XmlName() string {
	return f.xmlName
}

func (f *ExprField) SrcType() string {
	return f.Type.SrcName()
}

func (f *ExprField) Size() Size {
	return f.Type.Size()
}

func (f *ExprField) Initialize(p *Protocol) {
	f.srcName = SrcName(f.XmlName())
	f.Type = f.Type.(*Translation).RealType(p)
	f.Expr.Initialize(p)
}

type ValueField struct {
	Parent interface{}
	MaskType Type
	MaskName string
	ListName string
}

func (f *ValueField) SrcName() string {
	panic("it is illegal to call SrcName on a ValueField field")
}

func (f *ValueField) XmlName() string {
	panic("it is illegal to call XmlName on a ValueField field")
}

func (f *ValueField) SrcType() string {
	return f.MaskType.SrcName()
}

func (f *ValueField) Size() Size {
	maskSize := f.MaskType.Size()
	listSize := newExpressionSize(&Function{
		Name: "pad",
		Expr: &BinaryOp{
			Op: "*",
			Expr1: &Value{v: 4},
			Expr2: &PopCount{
				Expr: &Function{
					Name: "int",
					Expr: &FieldRef{
						Name: f.MaskName,
					},
				},
			},
		},
	})
	return maskSize.Add(listSize)
}

func (f *ValueField) ListLength() Size {
	return newExpressionSize(&PopCount{
		Expr: &Function{
			Name: "int",
			Expr: &FieldRef{
				Name: f.MaskName,
			},
		},
	})
}

func (f *ValueField) Initialize(p *Protocol) {
	f.MaskType = f.MaskType.(*Translation).RealType(p)
	f.MaskName = SrcName(f.MaskName)
	f.ListName = SrcName(f.ListName)
}

type SwitchField struct {
	Name     string
	Expr     Expression
	Bitcases []*Bitcase
}

func (f *SwitchField) SrcName() string {
	panic("it is illegal to call SrcName on a SwitchField field")
}

func (f *SwitchField) XmlName() string {
	panic("it is illegal to call XmlName on a SwitchField field")
}

func (f *SwitchField) SrcType() string {
	panic("it is illegal to call SrcType on a SwitchField field")
}

// XXX: This is a bit tricky. The size has to be represented as a non-concrete
// expression that finds *which* bitcase fields are included, and sums the
// sizes of those fields.
func (f *SwitchField) Size() Size {
	return newFixedSize(0)
}

func (f *SwitchField) Initialize(p *Protocol) {
	f.Name = SrcName(f.Name)
	f.Expr.Initialize(p)
	for _, bitcase := range f.Bitcases {
		bitcase.Expr.Initialize(p)
		for _, field := range bitcase.Fields {
			field.Initialize(p)
		}
	}
}

type Bitcase struct {
	Fields []Field
	Expr   Expression
}