package code

import (
	"encoding/binary"
	"math"
)

type Builder struct {
	code      []byte
	debugInfo DebugInfo

	currentLine int
	lineStart   int
}

func NewBuilder() Builder {
	return Builder{
		code:        make([]byte, 0, 64),
		debugInfo:   NewDebugInfo("unknown file"),
		lineStart:   -1,
		currentLine: -1,
	}
}

func (b *Builder) AppendOp(op Op) {
	b.code = append(b.code, byte(op))
}

func (b *Builder) AppendInt(x int64) {
	b.code = append(b.code, make([]byte, 8)...)
	binary.LittleEndian.PutUint64(b.code[len(b.code)-8:], uint64(x))
}

func (b *Builder) AppendFloat(x float64) {
	b.AppendInt(int64(math.Float64bits(x)))
}

func (b *Builder) AppendString(s string) {
	b.code = append(b.code, []byte(s)...)
	b.code = append(b.code, 0)
}

func (b *Builder) AppendRaw(raw Raw) {
	b.code = append(b.code, raw...)
}

func (b *Builder) StartLine(line int) {
	if b.lineStart != -1 {
		panic("line already started")
	}

	b.currentLine = line
	b.lineStart = len(b.code)
}

func (b *Builder) EndLine() {
	defer func() {
		b.currentLine = -1
		b.lineStart = -1
	}()

	if b.lineStart == -1 {
		panic("line not started")
	}

	if b.lineStart == len(b.code) {
		return
	}
	
	b.debugInfo.AppendLine(len(b.code)-1, b.currentLine)
}

func (b *Builder) SetInt(at int, x int64) {
	binary.LittleEndian.PutUint64(b.code[at:], uint64(x))
}

func (b *Builder) Code() Raw {
	return Raw(b.code)
}

func (b *Builder) Len() int {
	return len(b.code)
}

func (b *Builder) Build() Code {
	return New(b.code, b.debugInfo)
}