source: server/auth.go@ 35bcb41

package main

import (
        "crypto/sha256"
        "database/sql"
        "encoding/hex"
        "errors"
        "fmt"
        "strings"

        "bp_project/server/db"
)

func hashPassword(pw string) string {
        sum := sha256.Sum256([]byte(pw))
        return hex.EncodeToString(sum[:])
}

// Register - UC0001
func Register() {
        fmt.Println("\n-- Register --")
        username := prompt("Username: ")
        email := prompt("Email: ")
        fullName := prompt("Full name: ")
        pw := prompt("Password (min 6 chars): ")

        if username == "" || email == "" || pw == "" {
                fmt.Println("Username, email and password are required.")
                return
        }
        if !strings.Contains(email, "@") {
                fmt.Println("Invalid email.")
                return
        }
        if len(pw) < 6 {
                fmt.Println("Password must be at least 6 characters.")
                return
        }

        var exists bool
        err := db.DB.QueryRow(
                `SELECT EXISTS(SELECT 1 FROM users WHERE username = $1 OR email = $2)`,
                username, email,
        ).Scan(&exists)
        if err != nil {
                fmt.Println("Database error:", err)
                return
        }
        if exists {
                fmt.Println("Username or email already taken.")
                return
        }

        _, err = db.DB.Exec(
                `INSERT INTO users (username, email, full_name, password_hash, available_balance)
                 VALUES ($1, $2, $3, $4, 0)`,
                username, email, fullName, hashPassword(pw),
        )
        if err != nil {
                fmt.Println("Failed to register:", err)
                return
        }
        fmt.Println("Account created. You can now log in.")
}

// Login - UC0002
func Login(s *Session) {
        fmt.Println("\n-- Login --")
        username := prompt("Username: ")
        pw := prompt("Password: ")
        if username == "" || pw == "" {
                fmt.Println("Username and password are required.")
                return
        }

        id, err := authenticate(username, pw)
        if err != nil {
                if errors.Is(err, errInvalidCreds) {
                        fmt.Println("Invalid credentials.")
                        return
                }
                fmt.Println("Login error:", err)
                return
        }
        s.UserID = id
        s.Username = username
        fmt.Println("Login successful.")
}

var errInvalidCreds = errors.New("invalid credentials")

func authenticate(username, pw string) (string, error) {
        var id, stored string
        err := db.DB.QueryRow(
                `SELECT id, password_hash FROM users WHERE username = $1`,
                username,
        ).Scan(&id, &stored)
        if err == sql.ErrNoRows {
                return "", errInvalidCreds
        }
        if err != nil {
                return "", err
        }
        if stored != hashPassword(pw) {
                return "", errInvalidCreds
        }
        return id, nil
}