changes for beta2

.github/workflows/testing.yml

@@ -7,6 +7,10 @@ on:
 
 jobs:
 
+  api_breakage:
+    name: Check API breakage
+    uses: BinaryBirds/github-workflows/.github/workflows/api_breakage.yml@main
+
   swiftlang_checks:
     name: Swiftlang Checks
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
@@ -27,13 +31,7 @@ jobs:
     uses: BinaryBirds/github-workflows/.github/workflows/extra_soundness.yml@main
     with:
       local_swift_dependencies_check_enabled : true
+      run_tests_with_cache_enabled : true
       headers_check_enabled : false
       docc_warnings_check_enabled : true
-
-  swiftlang_tests:
-    name: Swiftlang Tests
-    uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
-    with:
-      enable_windows_checks : false
-      linux_build_command: "swift test --parallel --enable-code-coverage"
-      linux_exclude_swift_versions: "[{\"swift_version\": \"5.8\"}, {\"swift_version\": \"5.9\"}, {\"swift_version\": \"5.10\"}, {\"swift_version\": \"nightly\"}, {\"swift_version\": \"nightly-main\"}, {\"swift_version\": \"6.0\"}, {\"swift_version\": \"nightly-6.0\"}, {\"swift_version\": \"nightly-6.1\"}, {\"swift_version\": \"nightly-6.3\"}]"
+      run_tests_swift_versions: '["6.1","6.2"]'

Makefile

@@ -4,6 +4,9 @@ baseUrl = https://raw.githubusercontent.com/BinaryBirds/github-workflows/refs/he
 
 check: symlinks language deps lint headers docc-warnings package
 
+breakage:
+	curl -s $(baseUrl)/check-api-breakage.sh | bash
+
 package:
 	curl -s $(baseUrl)/check-swift-package.sh | bash
 

README.md

@@ -2,8 +2,8 @@
 
 An abstract mail component for Feather CMS.
 
-[![Release: 1.0.0-beta.1](https://img.shields.io/badge/Release-1%2E0%2E0--beta%2E1-F05138)](
-    https://github.com/feather-framework/feather-mail/releases/tag/1.0.0-beta.1
+[![Release: 1.0.0-beta.2](https://img.shields.io/badge/Release-1%2E0%2E0--beta%2E2-F05138)](
+    https://github.com/feather-framework/feather-mail/releases/tag/1.0.0-beta.2
 )
 
 ## Features
@@ -16,10 +16,11 @@ An abstract mail component for Feather CMS.
 ## Requirements
 
 ![Swift 6.1+](https://img.shields.io/badge/Swift-6%2E1%2B-F05138)
-![Platforms: macOS, iOS, tvOS, watchOS, visionOS](https://img.shields.io/badge/Platforms-macOS_%7C_iOS_%7C_tvOS_%7C_watchOS_%7C_visionOS-F05138)
+![Platforms: Linux, macOS, iOS, tvOS, watchOS, visionOS](https://img.shields.io/badge/Platforms-Linux_%7C_macOS_%7C_iOS_%7C_tvOS_%7C_watchOS_%7C_visionOS-F05138)
 
 - Swift 6.1+
 - Platforms:
+  - Linux
   - macOS 15+
   - iOS 18+
   - tvOS 18+
@@ -31,7 +32,7 @@ An abstract mail component for Feather CMS.
 Use Swift Package Manager; add the dependency to your `Package.swift` file:
 
 ```swift
-.package(url: "https://github.com/feather-framework/feather-mail", exact: "1.0.0-beta.1"),
+.package(url: "https://github.com/feather-framework/feather-mail", exact: "1.0.0-beta.2"),
 ```
 
 Then add `FeatherMail` to your target dependencies:

Sources/FeatherMail/Encoder/Base64+UInt8.swift

@@ -0,0 +1,54 @@
+//
+//  Base64+UInt8.swift
+//  feather-mail
+//
+//  Created by Binary Birds on 2026. 02. 06..
+//
+
+//  Foundation-free Base64 encoding for byte arrays.
+public extension Array where Element == UInt8 {
+    /// Returns a Base64 string representation of the byte array.
+    func base64EncodedString() -> String {
+        guard !isEmpty else {
+            return ""
+        }
+
+        let alphabet = Array(
+            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+                .utf8
+        )
+        var output: [UInt8] = []
+        output.reserveCapacity(((count + 2) / 3) * 4)
+
+        var index = 0
+        while index < count {
+            let byte0 = self[index]
+            let byte1 = (index + 1 < count) ? self[index + 1] : 0
+            let byte2 = (index + 2 < count) ? self[index + 2] : 0
+
+            let triple =
+                (UInt32(byte0) << 16) | (UInt32(byte1) << 8) | UInt32(byte2)
+
+            output.append(alphabet[Int((triple >> 18) & 0x3F)])
+            output.append(alphabet[Int((triple >> 12) & 0x3F)])
+
+            if index + 1 < count {
+                output.append(alphabet[Int((triple >> 6) & 0x3F)])
+            }
+            else {
+                output.append(UInt8(ascii: "="))
+            }
+
+            if index + 2 < count {
+                output.append(alphabet[Int(triple & 0x3F)])
+            }
+            else {
+                output.append(UInt8(ascii: "="))
+            }
+
+            index += 3
+        }
+
+        return String(decoding: output, as: UTF8.self)
+    }
+}

Sources/FeatherMail/Encoder/MailEncoder.swift

@@ -0,0 +1,20 @@
+//
+//  MailEncoder.swift
+//  feather-mail
+//
+//  Created by Binary Birds on 2026. 02. 06.
+//
+
+/// Encodes `Mail` values into raw MIME messages suitable for transport providers.
+public protocol MailEncoder: Sendable {
+
+    /// Encodes a mail into a raw MIME message string.
+    ///
+    /// - Parameter mail: The mail to encode. The mail must be validated
+    ///   before calling this method.
+    /// - Returns: A raw MIME string suitable for transport providers.
+    /// - Throws: `MailError.validation(.mailEncodeError)` when the message cannot be constructed.
+    func encode(
+        mail: Mail
+    ) throws(MailError) -> String
+}

Sources/FeatherMail/Encoder/RawMailEncoder.swift

@@ -12,35 +12,59 @@
 /// The encoding logic preserves the legacy behavior and output format.
 ///
 /// The encoder:
-/// - builds standard email headers (From, To, Cc, Reply-To, Subject, Date)
+/// - builds standard email headers (From, To, Cc, Reply-To, Subject, Date, Message-ID)
 /// - supports plain text and HTML bodies
 /// - supports attachments using `multipart/mixed`
 ///
 /// This type performs **no validation**. Callers are expected to validate
 /// the `Mail` instance before encoding.
-public struct RawMailEncoder: Sendable {
+public struct RawMailEncoder: MailEncoder {
+
+    var boundaryEncodingStrategy: (@Sendable (Mail) -> String)
+    var messageIDEncodingStrategy: (@Sendable (Mail) -> String)
+    var headerDateEncodingStrategy: (@Sendable () -> String)
 
     /// Creates a raw mail encoder.
-    public init() {}
+    ///
+    /// - Parameters:
+    ///   - boundaryEncodingStrategy: Provides the MIME boundary string used
+    ///     when attachments are present.
+    ///   - messageIDEncodingStrategy: Provides the Message-ID header value,
+    ///     including angle brackets.
+    ///   - headerDateEncodingStrategy: Provides the RFC 2822-formatted Date header
+    ///     value, for example `Mon, 26 Jan 2026 12:34:56 +0000`.
+    public init(
+        boundaryEncodingStrategy: (@escaping @Sendable (Mail) -> String) = {
+            _ in
+            "Boundary-\(String(UInt64.random(in: UInt64.min...UInt64.max), radix: 16))"
+        },
+        messageIDEncodingStrategy: (@escaping @Sendable (Mail) -> String) = {
+            mail in
+            let nonce = UInt64.random(in: UInt64.min...UInt64.max)
+            return "<\(nonce)\(mail.from.email.drop { $0 != "@" })>"
+        },
+        headerDateEncodingStrategy: (@escaping @Sendable () -> String)
+    ) {
+        self.boundaryEncodingStrategy = boundaryEncodingStrategy
+        self.messageIDEncodingStrategy = messageIDEncodingStrategy
+        self.headerDateEncodingStrategy = headerDateEncodingStrategy
+    }
 
     /// Encodes a mail into a raw MIME message string.
     ///
-    /// - Parameters:
-    ///   - mail: The mail to encode. The mail must be validated
-    ///     before calling this method.
-    ///   - dateHeader: RFC 2822-formatted date header value.
-    ///   - messageID: Message identifier value, including angle brackets.
+    /// - Parameter mail: The mail to encode. The mail must be validated
+    ///   before calling this method.
     /// - Returns: A raw MIME string suitable for transport providers.
-    /// - Throws: `MailError.validation(.mailEncodeError)` when the message cannot be constructed.
+    /// - Throws: `MailError.validation(.emptyHeaderDateString)` when the configured Date header value is empty.
     public func encode(
-        _ mail: Mail,
-        dateHeader: String,
-        messageID: String
+        mail: Mail
     ) throws(MailError) -> String {
 
-        var out = String()
-        out.reserveCapacity(4096)
+        guard !headerDateEncodingStrategy().isEmpty else {
+            throw MailError.validation(.emptyHeaderDateString)
+        }
 
+        var out = String()
         out += "From: \(mail.from.mime)\r\n"
 
         if !mail.to.isEmpty {
@@ -57,15 +81,18 @@ public struct RawMailEncoder: Sendable {
         }
 
         out += "Subject: \(mail.subject)\r\n"
-        out += "Date: \(dateHeader)\r\n"
-        out += "Message-ID: \(messageID)\r\n"
+        out += "Date: \(headerDateEncodingStrategy())\r\n"
+        out += "Message-ID: \(messageIDEncodingStrategy(mail))\r\n"
 
         if let reference = mail.reference {
             out += "In-Reply-To: \(reference)\r\n"
             out += "References: \(reference)\r\n"
         }
 
-        let boundary = mail.attachments.isEmpty ? nil : createBoundary()
+        let boundary =
+            mail.attachments.isEmpty
+            ? nil
+            : (boundaryEncodingStrategy(mail))
 
         if let boundary {
             out += "Content-type: multipart/mixed; boundary=\"\(boundary)\"\r\n"
@@ -103,68 +130,12 @@ public struct RawMailEncoder: Sendable {
                 out += attachment.data.base64EncodedString()
                 out += "\r\n"
             }
+            out += "--\(boundary)--\r\n"
         }
 
         out += "\r\n"
 
         return out
     }
-}
-
-// MARK: - Helpers
 
-private extension RawMailEncoder {
-
-    /// Creates a unique MIME boundary without Foundation.
-    func createBoundary() -> String {
-        "Boundary-\(String(UInt64.random(in: UInt64.min...UInt64.max), radix: 16))"
-    }
-}
-
-//  Foundation-free Base64 encoding for byte arrays.
-private extension Array where Element == UInt8 {
-    /// Returns a Base64 string representation of the byte array.
-    func base64EncodedString() -> String {
-        guard !isEmpty else {
-            return ""
-        }
-
-        let alphabet = Array(
-            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
-                .utf8
-        )
-        var output: [UInt8] = []
-        output.reserveCapacity(((count + 2) / 3) * 4)
-
-        var index = 0
-        while index < count {
-            let byte0 = self[index]
-            let byte1 = (index + 1 < count) ? self[index + 1] : 0
-            let byte2 = (index + 2 < count) ? self[index + 2] : 0
-
-            let triple =
-                (UInt32(byte0) << 16) | (UInt32(byte1) << 8) | UInt32(byte2)
-
-            output.append(alphabet[Int((triple >> 18) & 0x3F)])
-            output.append(alphabet[Int((triple >> 12) & 0x3F)])
-
-            if index + 1 < count {
-                output.append(alphabet[Int((triple >> 6) & 0x3F)])
-            }
-            else {
-                output.append(UInt8(ascii: "="))
-            }
-
-            if index + 2 < count {
-                output.append(alphabet[Int(triple & 0x3F)])
-            }
-            else {
-                output.append(UInt8(ascii: "="))
-            }
-
-            index += 3
-        }
-
-        return String(decoding: output, as: UTF8.self)
-    }
 }

Sources/FeatherMail/Models/Error/MailValidationError.swift

@@ -35,6 +35,9 @@ public enum MailValidationError: Error, Equatable {
 
     // MARK: - Encoding errors
 
+    /// The required Date header value is empty.
+    case emptyHeaderDateString
+
     /// Failed to encode the mail into the required transport format.
     ///
     /// This can occur when generating raw MIME data for providers like SES.