feat(message-reader): add css classname provider

Author: rafaeltonholo

app-common/build.gradle.kts

@@ -49,6 +49,8 @@ dependencies {
 
     implementation(projects.feature.mail.message.export.api)
     implementation(projects.feature.mail.message.export.implEml)
+    implementation(projects.feature.mail.message.reader.api)
+    implementation(projects.feature.mail.message.reader.impl)
 
     implementation(projects.mail.protocols.imap)
     implementation(projects.backend.imap)

app-common/src/main/kotlin/net/thunderbird/android/feature/mail/message/reader/api/css/DefaultCssClassNameProvider.kt

@@ -0,0 +1,26 @@
+package net.thunderbird.android.feature.mail.message.reader.api.css
+
+import com.fsck.k9.message.html.EmailTextToHtml
+import net.thunderbird.core.featureflag.FeatureFlagProvider
+import net.thunderbird.feature.mail.message.reader.api.MessageReaderFeatureFlags
+import net.thunderbird.feature.mail.message.reader.api.css.CssClassNameProvider
+
+class DefaultCssClassNameProvider(
+    featureFlagProvider: FeatureFlagProvider,
+    override val defaultNamespaceClassName: String,
+) : CssClassNameProvider {
+    override val rootClassName: String = "${defaultNamespaceClassName}__message-viewer"
+    override val mainContentClassName: String = "${defaultNamespaceClassName}__main-content"
+    override val plainTextMessagePreClassName: String =
+        if (featureFlagProvider.provide(MessageReaderFeatureFlags.UseNewMessageReaderCssStyles).isEnabled()) {
+            EmailTextToHtml.K9MAIL_CSS_CLASS
+        } else {
+            "${defaultNamespaceClassName}__plain-text-message-pre"
+        }
+    override val signatureClassName: String =
+        if (featureFlagProvider.provide(MessageReaderFeatureFlags.UseNewMessageReaderCssStyles).isEnabled()) {
+            "${defaultNamespaceClassName}__signature"
+        } else {
+            "k9mail-signature"
+        }
+}

app-k9mail/src/main/kotlin/app/k9mail/feature/FeatureModule.kt

@@ -5,8 +5,11 @@ import app.k9mail.feature.funding.featureFundingModule
 import app.k9mail.feature.migration.launcher.featureMigrationModule
 import app.k9mail.feature.onboarding.migration.onboardingMigrationModule
 import app.k9mail.feature.telemetry.telemetryModule
+import com.fsck.k9.BuildConfig
+import net.thunderbird.android.feature.mail.message.reader.api.css.DefaultCssClassNameProvider
 import net.thunderbird.feature.account.settings.featureAccountSettingsModule
 import net.thunderbird.feature.mail.message.list.featureMessageListModule
+import net.thunderbird.feature.mail.message.reader.api.css.CssClassNameProvider
 import org.koin.dsl.module
 
 val featureModule = module {
@@ -18,4 +21,11 @@ val featureModule = module {
     includes(featureMessageListModule)
 
     single<FundingSettings> { K9FundingSettings() }
+
+    single<CssClassNameProvider> {
+        DefaultCssClassNameProvider(
+            featureFlagProvider = get(),
+            defaultNamespaceClassName = BuildConfig.APPLICATION_ID.replace(".", "-"),
+        )
+    }
 }

app-thunderbird/src/main/kotlin/net/thunderbird/android/feature/FeatureModule.kt

@@ -5,8 +5,11 @@ import app.k9mail.feature.funding.featureFundingModule
 import app.k9mail.feature.migration.launcher.featureMigrationModule
 import app.k9mail.feature.onboarding.migration.onboardingMigrationModule
 import app.k9mail.feature.telemetry.telemetryModule
+import net.thunderbird.android.BuildConfig
+import net.thunderbird.android.feature.mail.message.reader.api.css.DefaultCssClassNameProvider
 import net.thunderbird.feature.account.settings.featureAccountSettingsModule
 import net.thunderbird.feature.mail.message.list.featureMessageListModule
+import net.thunderbird.feature.mail.message.reader.api.css.CssClassNameProvider
 import org.koin.dsl.module
 
 internal val featureModule = module {
@@ -18,4 +21,11 @@ internal val featureModule = module {
     includes(featureMessageListModule)
 
     single<FundingSettings> { TbFundingSettings() }
+
+    single<CssClassNameProvider> {
+        DefaultCssClassNameProvider(
+            featureFlagProvider = get(),
+            defaultNamespaceClassName = BuildConfig.APPLICATION_ID.replace(".", "-"),
+        )
+    }
 }

feature/mail/message/reader/api/src/commonMain/kotlin/net/thunderbird/feature/mail/message/reader/api/css/CssClassNameProvider.kt

@@ -0,0 +1,37 @@
+package net.thunderbird.feature.mail.message.reader.api.css
+
+/**
+ * Provides CSS class names used for styling the message viewer.
+ *
+ * This allows for a consistent and centralized way to manage the class names
+ * used in the HTML of the message display, making it easier to style and
+ * maintain.
+ */
+interface CssClassNameProvider {
+    /**
+     * The class name used to namespace all CSS rules to avoid conflicts with message content.
+     *
+     * This class should be applied to a high-level container element wrapping the entire message view.
+     */
+    val defaultNamespaceClassName: String
+
+    /**
+     * The class name for the root element of the message content. This is typically the `<body>` tag.
+     */
+    val rootClassName: String
+
+    /**
+     * The class name for the main content block of the message viewer.
+     */
+    val mainContentClassName: String
+
+    /**
+     * The class name for the `<pre>` tag that wraps plain text messages to preserve formatting.
+     */
+    val plainTextMessagePreClassName: String
+
+    /**
+     * The class name used to style email signatures.
+     */
+    val signatureClassName: String
+}