package handlers

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strings"
	"strconv"
)

// Struct for incoming JSON request
type SignupRequest struct {
	Email string `json:"email"`
}

// Struct for JSON response
type SignupResponse struct {
	Message string `json:"message"`
}

type User struct {
	Email string `json:"email"`
}

func HandleSignup(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Only POST allowed", http.StatusMethodNotAllowed)
		return
	}

	if err := r.ParseForm(); err != nil {
		http.Error(w, "Failed to parse form", http.StatusBadRequest)
		return
	}

	email := strings.TrimSpace(r.FormValue("email"))
	if email == "" {
		http.Error(w, "Missing email", http.StatusBadRequest)
		return
	}

	// Optional: basic email format check
	if !strings.Contains(email, "@") {
		http.Error(w, "Invalid email format", http.StatusBadRequest)
		return
	}

	log.Printf("Received signup from email: %s", email)
	err := AddUserToFile(email, "db/users.json")
	if err != nil {
		log.Printf("Error saving user: %v", err)
		http.Error(w, "Failed to save user", http.StatusInternalServerError)
		return
	}

	// Respond with success
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(SignupResponse{
		Message: fmt.Sprintf("Signup received. In the coming days, you will receive an email telling you how to join."),
	})
}

func AddUserToFile(email string, filepath string) error {
	// Read the current users (if file exists)
	users := make(map[string]User)

	if existingData, err := os.ReadFile(filepath); err == nil && len(existingData) > 0 {
		if err := json.Unmarshal(existingData, &users); err != nil {
			return fmt.Errorf("invalid users.json format: %v", err)
		}
	}

	// Find the next numeric key
	maxID := 0
	for key := range users {
		id, err := strconv.Atoi(key)
		if err == nil && id > maxID {
			maxID = id
		}
	}
	newID := strconv.Itoa(maxID + 1)

	// Add new user
	users[newID] = User{Email: email}

	// Marshal updated data
	updated, err := json.MarshalIndent(users, "", "  ")
	if err != nil {
		return fmt.Errorf("could not marshal updated users: %v", err)
	}

	// Write updated data back to file
	if err := os.WriteFile(filepath, updated, 0644); err != nil {
		return fmt.Errorf("could not write to users file: %v", err)
	}

	return nil
}