feat: Add source code for "Let's Go" chapter (#29)

LetsGo/README.md

@@ -0,0 +1,22 @@
+## Let's Go
+
+### Test Your API
+
+Start the server:
+```shell
+$ go run cmd/server/main.go
+```
+
+Add records:
+```shell
+$ curl -X POST localhost:8080 -d '{"record": { "value": "TGV0J3MgR28gIzMK" }}'
+$ curl -X POST localhost:8080 -d '{"record": { "value": "TGV0J3MgR28gIzEK" }}'
+$ curl -X POST localhost:8080 -d '{"record": { "value": "TGV0J3MgR28gIzIK" }}'
+```
+
+Retrieve records:
+```shell
+$ curl -X GET localhost:8080 -d '{"offset": 0}'
+$ curl -X GET localhost:8080 -d '{"offset": 1}'
+$ curl -X GET localhost:8080 -d '{"offset": 2}'
+```

LetsGo/cmd/server/main.go

@@ -0,0 +1,12 @@
+package main
+
+import (
+	"log"
+
+	"github.com/igor-baiborodine/proglog/internal/server"
+)
+
+func main() {
+	srv := server.NewHTTPServer(":8080")
+	log.Fatal(srv.ListenAndServe())
+}

LetsGo/go.mod

@@ -0,0 +1,5 @@
+module github.com/igor-baiborodine/proglog
+
+go 1.13
+
+require github.com/gorilla/mux v1.7.3

LetsGo/go.sum

@@ -0,0 +1,2 @@
+github.com/gorilla/mux v1.7.3 h1:gnP5JzjVOuiZD07fKKToCAOjS0yOpj/qPETTXCCS6hw=
+github.com/gorilla/mux v1.7.3/go.mod h1:1lud6UwP+6orDFRuTfBEV8e9/aOM/c4fVVCaMa2zaAs=

LetsGo/internal/server/http.go

@@ -0,0 +1,89 @@
+package server
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/gorilla/mux"
+)
+
+func NewHTTPServer(addr string) *http.Server {
+	httpsrv := newHTTPServer()
+	r := mux.NewRouter()
+	r.HandleFunc("/", httpsrv.handleProduce).Methods("POST")
+	r.HandleFunc("/", httpsrv.handleConsume).Methods("GET")
+	return &http.Server{
+		Addr:    addr,
+		Handler: r,
+	}
+}
+
+type httpServer struct {
+	Log *Log
+}
+
+func newHTTPServer() *httpServer {
+	return &httpServer{
+		Log: NewLog(),
+	}
+}
+
+type ProduceRequest struct {
+	Record Record `json:"record"`
+}
+
+type ProduceResponse struct {
+	Offset uint64 `json:"offset"`
+}
+
+type ConsumeRequest struct {
+	Offset uint64 `json:"offset"`
+}
+
+type ConsumeResponse struct {
+	Record Record `json:"record"`
+}
+
+func (s *httpServer) handleProduce(w http.ResponseWriter, r *http.Request) {
+	var req ProduceRequest
+	err := json.NewDecoder(r.Body).Decode(&req)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+	off, err := s.Log.Append(req.Record)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	res := ProduceResponse{Offset: off}
+	err = json.NewEncoder(w).Encode(res)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+}
+
+func (s *httpServer) handleConsume(w http.ResponseWriter, r *http.Request) {
+	var req ConsumeRequest
+	err := json.NewDecoder(r.Body).Decode(&req)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+	record, err := s.Log.Read(req.Offset)
+	if err == ErrOffsetNotFound {
+		http.Error(w, err.Error(), http.StatusNotFound)
+		return
+	}
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	res := ConsumeResponse{Record: record}
+	err = json.NewEncoder(w).Encode(res)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+}

LetsGo/internal/server/log.go

@@ -0,0 +1,39 @@
+package server
+
+import (
+	"fmt"
+	"sync"
+)
+
+type Log struct {
+	mu      sync.Mutex
+	records []Record
+}
+
+func NewLog() *Log {
+	return &Log{}
+}
+
+func (c *Log) Append(record Record) (uint64, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	record.Offset = uint64(len(c.records))
+	c.records = append(c.records, record)
+	return record.Offset, nil
+}
+
+func (c *Log) Read(offset uint64) (Record, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if offset >= uint64(len(c.records)) {
+		return Record{}, ErrOffsetNotFound
+	}
+	return c.records[offset], nil
+}
+
+type Record struct {
+	Value  []byte `json:"value"`
+	Offset uint64 `json:"offset"`
+}
+
+var ErrOffsetNotFound = fmt.Errorf("offset not found")

README.md

@@ -7,7 +7,7 @@ but is updated and executed against the latest versions of dependent Go packages
 
 **Table of Contents**
 
-- [ ] 1.Let's Go
+- [X] 1.[Let's Go](/LetsGo)
 - [ ] 2.Structure Data with Protocol Buffers
 - [ ] 3.Write a Log Package
 - [ ] 4.Serve Requests with gRPC