Add server side email prefix generation method (#525)

src/AliasVault.Api/AliasVault.Api.csproj

@@ -34,6 +34,7 @@
 
     <ItemGroup>
       <ProjectReference Include="..\Databases\AliasServerDb\AliasServerDb.csproj" />
+      <ProjectReference Include="..\Generators\AliasVault.Generators.Identity\AliasVault.Generators.Identity.csproj" />
       <ProjectReference Include="..\Shared\AliasVault.Shared.Server\AliasVault.Shared.Server.csproj" />
       <ProjectReference Include="..\Shared\AliasVault.Shared\AliasVault.Shared.csproj" />
       <ProjectReference Include="..\Utilities\AliasVault.Auth\AliasVault.Auth.csproj" />

src/AliasVault.Api/Controllers/IdentityController.cs

@@ -0,0 +1,163 @@
+//-----------------------------------------------------------------------
+// <copyright file="IdentityController.cs" company="lanedirt">
+// Copyright (c) lanedirt. All rights reserved.
+// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace AliasVault.Api.Controllers;
+
+using AliasServerDb;
+using AliasVault.Api.Controllers.Abstracts;
+using AliasVault.Generators.Identity;
+using AliasVault.Generators.Identity.Implementations.Factories;
+using AliasVault.Generators.Identity.Models;
+using Asp.Versioning;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+
+/// <summary>
+/// Controller for generating identities taking into account existing information on the AliasVault server.
+/// </summary>
+/// <param name="userManager">UserManager instance.</param>
+/// <param name="dbContextFactory">DbContextFactory instance.</param>
+[ApiVersion("1")]
+public class IdentityController(UserManager<AliasVaultUser> userManager, IAliasServerDbContextFactory dbContextFactory) : AuthenticatedRequestController(userManager)
+{
+    /// <summary>
+    /// Generates an email prefix based on provided identity fields.
+    /// </summary>
+    /// <param name="firstName">First name to use for generation.</param>
+    /// <param name="lastName">Last name to use for generation.</param>
+    /// <param name="birthDate">Birth date to use for generation.</param>
+    /// <param name="gender">Gender to use for generation (Male/Female).</param>
+    /// <param name="emailDomain">Email domain to use for checking if the to be generated email address is already taken.</param>
+    /// <param name="language">Two letter language code (en/nl) to use for generation.</param>
+    /// <returns>Generated email prefix.</returns>
+    [HttpGet("GenerateEmailPrefix")]
+    public async Task<IActionResult> GenerateEmailPrefix(
+        string? firstName = null,
+        string? lastName = null,
+        DateTime? birthDate = null,
+        string? gender = null,
+        string? emailDomain = null,
+        string language = "en")
+    {
+        var user = await GetCurrentUserAsync();
+        if (user == null)
+        {
+            return Unauthorized();
+        }
+
+        const int MaxAttempts = 10;
+        string emailPrefix;
+        var generator = new UsernameEmailGenerator();
+
+        // If no identity information is provided, generate a complete random identity
+        if (string.IsNullOrEmpty(firstName) && string.IsNullOrEmpty(lastName) && !birthDate.HasValue)
+        {
+            var identityGenerator = IdentityGeneratorFactory.CreateIdentityGenerator(language);
+            var identity = await identityGenerator.GenerateRandomIdentityAsync();
+            emailPrefix = identity.EmailPrefix;
+
+            // Try up to 10 times to generate a unique email prefix
+            int attempts = 1;
+            while (await EmailClaimExistsAsync(emailPrefix, emailDomain) && attempts < MaxAttempts)
+            {
+                identity = await identityGenerator.GenerateRandomIdentityAsync();
+                emailPrefix = identity.EmailPrefix;
+                attempts++;
+            }
+
+            // If still not unique, try with random numbers
+            if (await EmailClaimExistsAsync(emailPrefix, emailDomain))
+            {
+                emailPrefix = await GenerateUniqueEmailPrefixWithNumbersAsync(emailPrefix, emailDomain);
+            }
+
+            return Ok(new { emailPrefix });
+        }
+
+        // Create identity model with provided values
+        var identityModel = new Identity
+        {
+            FirstName = firstName ?? string.Empty,
+            LastName = lastName ?? string.Empty,
+            BirthDate = birthDate ?? DateTime.UtcNow.AddYears(-30),
+            Gender = gender?.Equals("Female", StringComparison.OrdinalIgnoreCase) == true ? Gender.Female : Gender.Male,
+            NickName = string.Empty,
+        };
+
+        // Generate initial email prefix
+        emailPrefix = generator.GenerateEmailPrefix(identityModel);
+
+        // Try up to 10 times to generate a unique email prefix
+        int baseAttempts = 1;
+        while (await EmailClaimExistsAsync(emailPrefix, emailDomain) && baseAttempts < MaxAttempts)
+        {
+            emailPrefix = generator.GenerateEmailPrefix(identityModel);
+            baseAttempts++;
+        }
+
+        // If still not unique, try with random numbers
+        if (await EmailClaimExistsAsync(emailPrefix, emailDomain))
+        {
+            emailPrefix = await GenerateUniqueEmailPrefixWithNumbersAsync(emailPrefix);
+        }
+
+        return Ok(new { emailPrefix });
+    }
+
+    /// <summary>
+    /// Verify that provided email address is not already taken by another user.
+    /// </summary>
+    /// <param name="emailPrefix">The email prefix to check.</param>
+    /// <param name="emailDomain">Email domain to use for checking if the to be generated email address is already taken.</param>
+    /// <returns>True if the email address is already taken, false otherwise.</returns>
+    private async Task<bool> EmailClaimExistsAsync(string emailPrefix, string? emailDomain = null)
+    {
+        if (emailDomain == null)
+        {
+            // If no email domain is provided, we assume a non-aliasvault address is used which cannot be taken.
+            return false;
+        }
+
+        await using var context = await dbContextFactory.CreateDbContextAsync();
+
+        var email = emailPrefix + "@" + emailDomain;
+        var claimExists = await context.UserEmailClaims.FirstOrDefaultAsync(c => c.Address == email);
+
+        return claimExists != null;
+    }
+
+    /// <summary>
+    /// Generate a unique email prefix with random numbers.
+    /// </summary>
+    /// <param name="basePrefix">The base prefix to use for generation.</param>
+    /// <param name="emailDomain">Email domain to use for checking if the to be generated email address is already taken.</param>
+    /// <returns>Unique email prefix with random numbers.</returns>
+    private async Task<string> GenerateUniqueEmailPrefixWithNumbersAsync(string basePrefix, string? emailDomain = null)
+    {
+        if (emailDomain == null)
+        {
+            // If no email domain is provided, we assume a non-aliasvault address is used which cannot be taken.
+            return basePrefix;
+        }
+
+        const int MaxAttempts = 10;
+        var random = new Random();
+
+        for (int i = 0; i < MaxAttempts; i++)
+        {
+            string prefix = $"{random.Next(10, 100)}.{basePrefix}.{random.Next(10, 100)}";
+            if (!await EmailClaimExistsAsync(prefix, emailDomain))
+            {
+                return prefix;
+            }
+        }
+
+        // If all attempts fail, return the last generated prefix
+        return $"{random.Next(10, 100)}.{basePrefix}.{random.Next(10, 100)}";
+    }
+}

src/AliasVault.Api/Controllers/VaultController.cs

@@ -386,7 +386,7 @@ private async Task UpdateUserEmailClaims(AliasServerDbContext context, string us
         foreach (var email in newEmailAddresses)
         {
             // Sanitize email address.
-            var sanitizedEmail = email.Trim().ToLower();
+            var sanitizedEmail = EmailHelper.SanitizeEmail(email);
 
             // If email address is invalid according to the EmailAddressAttribute, skip it.
             if (!new EmailAddressAttribute().IsValid(sanitizedEmail))

src/AliasVault.Api/Helpers/EmailHelper.cs

@@ -0,0 +1,24 @@
+//-----------------------------------------------------------------------
+// <copyright file="EmailHelper.cs" company="lanedirt">
+// Copyright (c) lanedirt. All rights reserved.
+// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace AliasVault.Api.Helpers;
+
+/// <summary>
+/// EmailHelper class which contains helper methods for email.
+/// </summary>
+public static class EmailHelper
+{
+    /// <summary>
+    /// Sanitize email address by trimming and converting to lowercase.
+    /// </summary>
+    /// <param name="email">Email address to sanitize.</param>
+    /// <returns>Sanitized email address.</returns>
+    public static string SanitizeEmail(string email)
+    {
+        return email.Trim().ToLower();
+    }
+}