replace redis with eventstore

.gitginore

@@ -0,0 +1 @@
+.#*

.gitignore

@@ -1 +1,4 @@
 tmp
+todo*.txt
+\#*
+\.#*

README.md

@@ -1,16 +1,29 @@
 # Todo App with GO and HTMX
 
-## Plan
+## Plan day 1
 
 - [x] create Go webserver
 - [x] create landing page
 - [x] import HTMX code
 - [x] display todo list
-- [ ] add tailwind CSS
-- [ ] show todo list
-- [ ] let todos be marked completed
-- [ ] remove todos
-- [ ] add new todo with form
-- [ ] persist todos in redis
-- [ ] spruce up 
+- [x] add tailwind CSS
+- [x] show todo list
+- [x] let todos be marked completed
+- [x] remove todos
+- [x] add new todo with form
+- [x] persist todos in redis
+- [x] spruce up 
 
+## Plan day 2
+
+make it use only battery included features, 
+
+i.e. replace redis with an event driven approach
+
+- [x] modularize app
+- [x] replace redis with json stream
+- [x] use hashmap for fast individual access
+- [ ] cache data to avoid reading each time
+- [ ] create event store
+- [ ] make events
+- [ ] implement event store

internal/model.go

@@ -0,0 +1,8 @@
+package model
+
+type Todo struct {
+	Id int
+	Title string
+	Completed bool
+}
+var MaxId int = 0

internal/model/model.go

@@ -0,0 +1,10 @@
+package model
+
+type Todo struct {
+	Id int
+	Title string
+	Completed bool
+}
+
+
+type Todos map[int]Todo

internal/persist/persist.go

@@ -0,0 +1,132 @@
+package persist
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"io"
+)
+
+import "snamellit.com/play/todo/internal/model"
+
+var EMPTY_TODO = model.Todo{Id: 0, Title: "", Completed: false}
+
+var maxId int = 0
+
+var todos model.Todos
+
+type eventType string
+const (
+	ADDED eventType = "ADDED"
+	DELETED eventType = "DELETED"
+	CHANGED eventType = "CHANGED"
+)
+
+type event struct {
+	Kind eventType 
+	Todo model.Todo
+}
+
+func readTodos() (model.Todos, error) {
+	f, err := os.OpenFile("todo_events.txt", os.O_RDONLY|os.O_CREATE, 0644)
+	defer f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	dec := json.NewDecoder(f)
+
+	todos = make(model.Todos)
+	for {
+		var e event
+		err = dec.Decode(&e)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return nil, err
+		}
+		fmt.Println("Read event", e)
+		id := e.Todo.Id
+		if id > maxId {
+			maxId = id
+		}
+		applyEvent(e.Kind, e.Todo)
+	}
+	return todos, nil
+}
+
+func applyEvent(kind eventType, todo model.Todo) error {
+	id := todo.Id
+	switch t := kind; t {
+	case ADDED:
+		fmt.Println("apply add ", todo)
+		todos[id] = todo
+	case CHANGED:
+		fmt.Println("apply change ", todo)
+		todos[id] = todo
+	case DELETED:
+		fmt.Println("apply delete ", todo)
+		delete(todos, id)
+	default:
+		return fmt.Errorf("Unknown event type %s", t)
+	}
+	return nil
+}
+
+func addEvent(kind eventType, todo model.Todo) error {
+	err := applyEvent(kind, todo)
+	if err != nil {
+		return err
+	}
+	
+	f, err := os.OpenFile("todo_events.txt", os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
+	defer f.Close()
+	if err != nil {
+		return err
+	}
+	fmt.Println("Write todo", todo)
+	enc := json.NewEncoder(f)
+	e := event{Kind: kind, Todo: todo}
+	fmt.Println("Write event", e)
+	err = enc.Encode(e)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func GetTodos() (model.Todos, error) {
+	if len(todos) == 0 {
+		return readTodos()
+	}
+	return todos, nil
+}
+
+
+func GetTodoById(id int) (model.Todo, error) {
+	todo, present := todos[id]
+	if !present {
+		return EMPTY_TODO, fmt.Errorf("Todo with id %d not found", id)
+	}
+	return todo, nil
+}
+
+func SetTodo(todo model.Todo) error {
+	fmt.Println("SetTodo", todo)
+	todos[todo.Id] = todo
+	return addEvent(CHANGED, todo)
+}
+
+func AddTodo(title string) error {
+	fmt.Println("AddTodo", title)
+	maxId++;
+	todo := model.Todo{Id: maxId, Title: title, Completed: false}
+	return addEvent(ADDED, todo)
+}
+
+func DeleteTodoById(id int) error {
+	delete(todos, id)
+	return addEvent(DELETED, model.Todo{Id: id})
+}
+

internal/webserver/webserver.go

@@ -0,0 +1,75 @@
+package webserver
+
+import ( 
+	"fmt"
+	"html/template"
+	"net/http"
+	"strconv"
+	"snamellit.com/play/todo/internal/persist"
+)
+
+
+func IndexHandler(w http.ResponseWriter, r *http.Request) {
+	t, _ := template.ParseFiles("templates/index.html")
+	t.Execute(w, nil)
+}
+
+
+func renderTodos(w http.ResponseWriter) {
+	fmt.Println("renderTodos")
+	todos,err := persist.GetTodos()
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "Error: %s", err)
+	}
+	t, _ := template.ParseFiles("templates/todos.html")
+	t.Execute(w, todos)
+}
+
+func TodosHandler(w http.ResponseWriter, r *http.Request) {
+	fmt.Println("TodosHandler")
+	if r.Method == "POST" {
+		r.ParseForm()
+		todoTitle := r.Form.Get("title")
+		persist.AddTodo(todoTitle)
+	}
+	renderTodos(w)
+}
+
+func ToggleTodoHandler(w http.ResponseWriter, r *http.Request) {
+	fmt.Println("ToggleTodoHandler")
+	todoId, err := strconv.Atoi(r.URL.Path)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "Error: %s", err)
+	}
+	fmt.Println("Toggle Todo Id: %d", todoId)
+	todo, err := persist.GetTodoById(todoId)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "Error: %s", err)
+	}
+	todo.Completed = !todo.Completed
+	err = persist.SetTodo(todo)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "Error: %s", err)
+	}
+	renderTodos(w)
+}
+
+func TodoHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "DELETE" {
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		fmt.Fprintf(w, "Method %s not allowed", r.Method)
+		return
+	}
+	todoId, err := strconv.Atoi(r.URL.Path)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println("Todo Id: %d", todoId)
+	persist.DeleteTodoById(todoId)
+	TodosHandler(w, r)
+	return
+}

main.go

@@ -1,141 +1,23 @@
 package main
 
 import (
-	"context"
 	"fmt"
-	"github.com/redis/go-redis/v9"
 	"log"
-	"encoding/json"
 	"net/http"
-	"html/template"
-	"strconv"
 )
 
-type todo struct {
-	Id int
-	Title string
-	Completed bool
-}
-var maxId int = 0
-
-var ctx = context.Background()
-var rdb = redis.NewClient(&redis.Options{
-        Addr:     "localhost:6379",
-        Password: "", // no password set
-        DB:       0,  // use default DB
-})
-
-func GetTodos() []todo {
-	var cursor uint64 = 0
-	todosJson, cursor, err := rdb.Scan(ctx, cursor, "todo:*", 20).Result()
-	if err != nil {
-		panic(err)
-	}
-	var todos []todo = make([]todo, len(todosJson))
-	for idx, todoJson := range todosJson {
-		todoJson :=  rdb.Get(ctx, todoJson).Val()
-		fmt.Println("Todo: %s", todoJson)
-		err = json.Unmarshal([]byte(todoJson), &todos[idx])
-		if err != nil {
-			panic(err)
-		}
-		if todos[idx].Id > maxId {
-			maxId = todos[idx].Id
-		}
-	}
-	return todos
-}
-
-func GetTodoById(id int) todo {
-	todoJson, err := rdb.Get(ctx, fmt.Sprintf("todo:%d", id)).Result()
-	if err != nil {
-		panic(err)
-	}
-	
-	var todo todo
-	err = json.Unmarshal([]byte(todoJson), &todo)
-	if err != nil {
-		panic(err)
-	}
-	return todo
-}
-
-func SetTodo(todo todo) {
-	todoJson, err := json.Marshal(todo)
-	if err != nil {
-		panic(err)
-	}
-	key := fmt.Sprintf("todo:%d", todo.Id)
-	err = rdb.Set(ctx, key, string(todoJson), 0).Err()
-	if err != nil {
-		panic(err)
-	}
-	fmt.Println("Set todo: %s", todoJson)
-}
-
-func DeleteTodoById(id int) {
-	err := rdb.Del(ctx, fmt.Sprintf("todo:%d", id)).Err()
-	if err != nil {
-		panic(err)
-	}
-}
-
-func IndexHandler(w http.ResponseWriter, r *http.Request) {
-	t, _ := template.ParseFiles("templates/index.html")
-	t.Execute(w, nil)
-}
-
-func TodosHandler(w http.ResponseWriter, r *http.Request) {
-	if r.Method == "POST" {
-		r.ParseForm()
-		todoTitle := r.Form.Get("title")
-		SetTodo(todo{Id: maxId + 1, Title: todoTitle, Completed: false})
-	}
-	todos := GetTodos()
-	t, _ := template.ParseFiles("templates/todos.html")
-	t.Execute(w, todos)
-}
-
-func ToggleTodoHandler(w http.ResponseWriter, r *http.Request) {
-	todoId, err := strconv.Atoi(r.URL.Path)
-	if err != nil {
-		panic(err)
-	}
-	fmt.Println("Todo Id: %d", todoId)
-	todo := GetTodoById(todoId)
-	todo.Completed = !todo.Completed
-	SetTodo(todo)
-	TodosHandler(w, r)
-	return
-}
-
-func TodoHandler(w http.ResponseWriter, r *http.Request) {
-	if r.Method != "DELETE" {
-		w.WriteHeader(http.StatusMethodNotAllowed)
-		fmt.Fprintf(w, "Method %s not allowed", r.Method)
-		return
-	}
-	todoId, err := strconv.Atoi(r.URL.Path)
-	if err != nil {
-		panic(err)
-	}
-	fmt.Println("Todo Id: %d", todoId)
-	DeleteTodoById(todoId)
-	TodosHandler(w, r)
-	return
-}
-
+import "snamellit.com/play/todo/internal/webserver"
 
 func main() {
 	fmt.Println("Starting web server on port 8080")
         fs := http.FileServer(http.Dir("./static"))
         http.Handle("/static/", http.StripPrefix("/static/", fs))
-	http.HandleFunc("/", IndexHandler)
-	http.HandleFunc("/todos", TodosHandler)
+	http.HandleFunc("/", webserver.IndexHandler)
+	http.HandleFunc("/todos", webserver.TodosHandler)
 	togglePath := "/toggle-todo/"
-	http.Handle(togglePath, http.StripPrefix(togglePath, http.HandlerFunc(ToggleTodoHandler)))
+	http.Handle(togglePath, http.StripPrefix(togglePath, http.HandlerFunc(webserver.ToggleTodoHandler)))
 	todoPath := "/todo/"
-	http.Handle(todoPath, http.StripPrefix(todoPath, http.HandlerFunc(TodoHandler)))
+	http.Handle(todoPath, http.StripPrefix(todoPath, http.HandlerFunc(webserver.TodoHandler)))
 
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }

static/output.css

@@ -534,10 +534,6 @@ video {
   --tw-backdrop-sepia:  ;
 }
 
-.block {
-  display: block;
-}
-
 .flex {
   display: flex;
 }
@@ -554,10 +550,6 @@ video {
   grid-template-columns: repeat(1, minmax(0, 1fr));
 }
 
-.flex-row {
-  flex-direction: row;
-}
-
 .gap-2 {
   gap: 0.5rem;
 }
@@ -568,24 +560,10 @@ video {
   margin-left: calc(1rem * calc(1 - var(--tw-space-x-reverse)));
 }
 
-.rounded {
-  border-radius: 0.25rem;
-}
-
 .rounded-xl {
   border-radius: 0.75rem;
 }
 
-.bg-slate-100 {
-  --tw-bg-opacity: 1;
-  background-color: rgb(241 245 249 / var(--tw-bg-opacity));
-}
-
-.bg-slate-200 {
-  --tw-bg-opacity: 1;
-  background-color: rgb(226 232 240 / var(--tw-bg-opacity));
-}
-
 .bg-red-500 {
   --tw-bg-opacity: 1;
   background-color: rgb(239 68 68 / var(--tw-bg-opacity));
@@ -596,6 +574,16 @@ video {
   background-color: rgb(14 165 233 / var(--tw-bg-opacity));
 }
 
+.bg-slate-100 {
+  --tw-bg-opacity: 1;
+  background-color: rgb(241 245 249 / var(--tw-bg-opacity));
+}
+
+.bg-slate-200 {
+  --tw-bg-opacity: 1;
+  background-color: rgb(226 232 240 / var(--tw-bg-opacity));
+}
+
 .p-4 {
   padding: 1rem;
 }

templates/todos.html

@@ -2,10 +2,10 @@
   {{range $index, $task := . }}
   <li id={{$task.Id}} class="p-4 rounded-xl bg-slate-100">
     <input type="checkbox" {{if $task.Completed}}checked{{end}}
-      hx-post="/toggle-todo/{{$task.Id}}" hx-swap="outerHTML" hx-target="#todos">
+      hx-post="/toggle-todo/{{$index}}" hx-swap="outerHTML" hx-target="#todos">
       {{$task.Title}}
     <button class="bg-red-500"
-      hx-delete="/todo/{{$task.Id}}" hx-swap="outerHTML" hx-target="#todos">X</button>
+      hx-delete="/todo/{{$index}}" hx-swap="outerHTML" hx-target="#todos">X</button>
   </li>
   {{end}}
   <li>