package main

import (
	"bytes"
	"reflect"
	"syscall/js"
	"unsafe"

	"bitbucket.org/ausocean/av/codec/adpcm"
)

func main() {
	dec := NewDecoder()
	dec.Start()
}

// Decoder is a client side adpcm decoder
type Decoder struct {
	inBuf                               []uint8
	onImgLoadCb, initMemCb, getDecLenCb js.Func
	console                             js.Value
	done                                chan struct{}
}

// NewDecoder returns a new instance of decoder
func NewDecoder() *Decoder {
	return &Decoder{
		console: js.Global().Get("console"),
		done:    make(chan struct{}),
	}
}

func (s *Decoder) setupOnImgLoadCb() {
	s.onImgLoadCb = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		// reader := bytes.NewReader(s.inBuf)

		//DECODING HAPPENS HERE

		decoded := bytes.NewBuffer(make([]byte, 0, len(s.inBuf)*4))
		dec := adpcm.NewDecoder(decoded)
		dec.Write(s.inBuf)

		s.inBuf = decoded.Bytes()

		return nil
	})
}

func (s *Decoder) setupInitMemCb() {
	// The length of the data array buffer is passed.
	// Then the buf slice is initialized to that length.
	// A pointer to that slice is passed back to the browser.
	s.initMemCb = js.FuncOf(func(this js.Value, i []js.Value) interface{} {
		length := i[0].Int()
		s.console.Call("log", "length:", length)
		s.inBuf = make([]uint8, length)
		hdr := (*reflect.SliceHeader)(unsafe.Pointer(&s.inBuf))
		ptr := uintptr(unsafe.Pointer(hdr.Data))
		s.console.Call("log", "ptr:", ptr)
		js.Global().Call("gotMem", ptr)
		return nil
	})
}

func (s *Decoder) setupGetDecLenCb() {
	s.getDecLenCb = js.FuncOf(func(this js.Value, i []js.Value) interface{} {
		return len(s.inBuf)
	})
}

// Start sets up all the callbacks and waits for the close signal
// to be sent from the browser.
func (s *Decoder) Start() {
	s.setupInitMemCb()
	js.Global().Set("initMem", s.initMemCb)
	s.setupOnImgLoadCb()
	js.Global().Set("loadData", s.onImgLoadCb)
	s.setupGetDecLenCb()
	js.Global().Set("getDecLen", s.getDecLenCb)
	<-s.done
}