// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package lib

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"io"
	"sync"

	"v.io/v23/vom"
)

func HexVomEncode(v interface{}) (string, error) {
	var buf bytes.Buffer
	encoder := vom.NewEncoder(&buf)
	if err := encoder.Encode(v); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf.Bytes()), nil
}

func HexVomEncodeOrDie(v interface{}) string {
	s, err := HexVomEncode(v)
	if err != nil {
		panic(err)
	}
	return s
}

func HexVomDecode(data string, v interface{}) error {
	binbytes, err := hex.DecodeString(data)
	if err != nil {
		return fmt.Errorf("Error decoding hex string %q: %v", data, err)
	}
	decoder := vom.NewDecoder(bytes.NewReader(binbytes))
	return decoder.Decode(v)
}

// TypeReader implements io.Reader but allows changing the underlying buffer.
// This is useful for merging discrete messages that are part of the same flow.
type TypeReader struct {
	buf      bytes.Buffer
	mu       sync.Mutex
	isClosed bool
	cond     *sync.Cond
}

func NewTypeReader() *TypeReader {
	reader := &TypeReader{}
	reader.cond = sync.NewCond(&reader.mu)
	return reader
}

func (r *TypeReader) Add(data string) error {
	binBytes, err := hex.DecodeString(data)
	if err != nil {
		return err
	}
	r.mu.Lock()
	_, err = r.buf.Write(binBytes)
	r.mu.Unlock()
	r.cond.Signal()
	return err
}

func (r *TypeReader) Read(p []byte) (int, error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	for {
		if r.buf.Len() > 0 {
			return r.buf.Read(p)
		}
		if r.isClosed {
			return 0, io.EOF
		}
		r.cond.Wait()
	}

}

func (r *TypeReader) Close() {
	r.mu.Lock()
	r.isClosed = true
	r.mu.Unlock()
	r.cond.Broadcast()
}

// TypeWriter implements io.Writer but allows changing the underlying buffer.
// This is useful for merging discrete messages that are part of the same flow.
type TypeWriter struct {
	writer ClientWriter
}

func NewTypeWriter(w ClientWriter) *TypeWriter {
	return &TypeWriter{writer: w}
}

func (w *TypeWriter) Write(p []byte) (int, error) {
	err := w.writer.Send(ResponseTypeMessage, p)
	if err != nil {
		return 0, err
	}
	return len(p), nil
}