transactional-http.go

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"math/rand"
	"net/http"
	"strconv"
	"time"
)

func HandleOperation(ctx context.Context, duplex *TransactionalDuplex) {
	defer fmt.Println("end operation")
	for {
		select {
		case operation := <-duplex.input:
			// do the operation
			switch o := operation.(type) {
			case *OperationInputSubmit:
				duplex.result <- &OperationResultSubmit{Message: "submit done" + o.Data}
			case *OperationInputCommit:
				// do commit and invalidate this func
				fmt.Println("Commit")
				return
			case *OperationInputRollback:
				// do rollback and invalidate this func
				fmt.Println("Rollback")
				return
			default:
				fmt.Println("operation handler created")
			}
		case <-ctx.Done():
			return
		}
	}
}

type OperationInput interface{}

type OperationInputSubmit struct {
	OperationInput
	Data string
}
type OperationInputCommit struct {
	OperationInput
}
type OperationInputRollback struct {
	OperationInput
}

type OperationResult interface{}
type OperationResultSubmit struct {
	Message string
}

type TransactionalDuplex struct {
	input  chan OperationInput
	result chan OperationResult
}

func NewTransactionalDuplex() *TransactionalDuplex {
	return &TransactionalDuplex{
		input:  make(chan OperationInput),
		result: make(chan OperationResult),
	}
}

type transactionCache map[string]*TransactionalDuplex
type TransactionalHandler struct {
	session transactionCache
}

func (t TransactionalHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {

	switch req.URL.Path {
	case "/tx":
		// generate random transaction ID
		tx := randomTx()
		duplex := NewTransactionalDuplex()
		t.session[tx] = duplex
		// routine out this function
		go func() {
			// this routine gonna end after this function exit
			ctx, _ := context.WithTimeout(context.Background(), time.Second*60)
			HandleOperation(ctx, t.session[tx])
		}()
		w.WriteHeader(201)
		_, _ = w.Write([]byte("transaction created! " + tx))

	case "/tx/submit":
		id := req.URL.Query().Get("id")
		if id == "" {
			w.WriteHeader(400)
			_, _ = w.Write([]byte("invalid id"))
			return
		}

		duplex := t.session[id]
		duplex.input <- &OperationInputSubmit{Data: "random submit data"}
		result := <-duplex.result
		b, _ := json.Marshal(result)
		_, _ = w.Write(b)
	case "/tx/commit":
		id := req.URL.Query().Get("id")
		if id == "" {
			w.WriteHeader(400)
			_, _ = w.Write([]byte("invalid id"))
			return
		}
		duplex := t.session[id]
		duplex.input <- &OperationInputCommit{}
		delete(t.session, id)
	}

}

func main() {

	err := http.ListenAndServe(":9901", &TransactionalHandler{
		session: make(transactionCache),
	})
	if err != nil {
		panic(err)
	}

}

func randomTx() string {
	return strconv.Itoa(rand.Int())
}