// openconn provides a basic context.Context object to be used with gaio.Watcher
// the context carries two channels, InChan and OutChan, which are used by menuHandler
// and doorHandler to read input from the remote connection
// TODO: decide whether or not we'll actuallly need OutChan - possibly for maintaining
// output writes in order and/or ensuring output is delivered exactly once
package openconn

import (
	"context"

	"github.com/xtaci/gaio"
)

// The key type is unexported to prevent collisions with context keys defined in
// other packages.
type key int

const inChanKey key = 0
const outChanKey key = 1

// NewContext returns a new Context carrying two new channels.
func NewContext(ctx context.Context) context.Context {
	inChan := make(chan gaio.OpResult)
	outChan := make(chan gaio.OpResult)
	ctx = context.WithValue(ctx, inChanKey, inChan)
	ctx = context.WithValue(ctx, outChanKey, outChan)
	return ctx
}

// FromContext extracts the two channels from ctx, if present.
func FromContext(ctx context.Context) (chan gaio.OpResult, chan gaio.OpResult, bool) {
	// ctx.Value returns nil if ctx has no value for the key;
	// the type assertion returns ok=false for nil.
	inChan, iok := ctx.Value(inChanKey).(chan gaio.OpResult)
	outChan, ook := ctx.Value(outChanKey).(chan gaio.OpResult)
	if iok && ook {
		return inChan, outChan, iok && ook
	}
	return nil, nil, iok && ook
}

// FromOpResult extracts the two channels from a gaio.OpResult, if present.
func FromOpResult(res gaio.OpResult) (chan gaio.OpResult, chan gaio.OpResult, bool) {
	ctx, ok := res.Context.(context.Context)
	if ok {
		inChan, iok := ctx.Value(inChanKey).(chan gaio.OpResult)
		outChan, ook := ctx.Value(outChanKey).(chan gaio.OpResult)
		return inChan, outChan, iok && ook
	}
	return nil, nil, ok
}