// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package rpc

import (
	"net"
	"time"

	"github.com/zeebo/errs"
	"gopkg.in/spacemonkeygo/monkit.v2"

	"storj.io/storj/internal/memory"
)

//go:generate go run gen.go ../pb drpc compat_drpc.go
//go:generate go run gen.go ../pb grpc compat_grpc.go

var mon = monkit.Package()

// Error wraps all of the errors returned by this package.
var Error = errs.Class("rpccompat")

// timedConn wraps a net.Conn so that all reads and writes get the specified timeout and
// return bytes no faster than the rate. If the timeout or rate are zero, they are
// ignored.
type timedConn struct {
	net.Conn
	rate memory.Size
}

// now returns time.Now if there's a nonzero rate.
func (t *timedConn) now() (now time.Time) {
	if t.rate > 0 {
		now = time.Now()
	}
	return now
}

// delay ensures that we sleep to keep the rate if it is nonzero. n is the number of
// bytes in the read or write operation we need to delay.
func (t *timedConn) delay(start time.Time, n int) {
	if t.rate > 0 {
		expected := time.Duration(n * int(time.Second) / t.rate.Int())
		if actual := time.Since(start); expected > actual {
			time.Sleep(expected - actual)
		}
	}
}

// Read wraps the connection read and adds sleeping to ensure the rate.
func (t *timedConn) Read(p []byte) (int, error) {
	start := t.now()
	n, err := t.Conn.Read(p)
	t.delay(start, n)
	return n, err
}

// Write wraps the connection write and adds sleeping to ensure the rate.
func (t *timedConn) Write(p []byte) (int, error) {
	start := t.now()
	n, err := t.Conn.Write(p)
	t.delay(start, n)
	return n, err
}