ui: add auto_choose_multipart_alternative

Choose text/html by default if text/plain is empty in
multipart/alternative attachments

This happens in some newsletters I've come upon

4 files changed, 44 insertions, 3 deletions

diff --git a/ui/src/components/mail/view.rs b/ui/src/components/mail/view.rs
index a6328eae..7fcf78b4 100644
--- a/ui/src/components/mail/view.rs
+++ b/ui/src/components/mail/view.rs
@@ -21,6 +21,7 @@
 
 use super::*;
 use melib::list_management;
+use melib::parser::BytesExt;
 
 use std::convert::TryFrom;
 use std::process::{Command, Stdio};
@@ -605,6 +606,35 @@ impl Component for MailView {
                     self.subview = Some(Box::new(HtmlView::new(&body, context)));
                     self.mode = ViewMode::Subview;
                 }
+                ViewMode::Normal
+                    if context
+                        .settings
+                        .pager
+                        .auto_choose_multipart_alternative
+                        .is_true()
+                        && match body.content_type {
+                            ContentType::Multipart {
+                                kind: MultipartType::Alternative,
+                                ref parts,
+                                ..
+                            } => parts.iter().all(|p| {
+                                p.is_html() || (p.is_text() && p.body().trim().is_empty())
+                            }),
+                            _ => false,
+                        } =>
+                {
+                    self.subview = Some(Box::new(HtmlView::new(
+                        &body
+                            .content_type
+                            .parts()
+                            .unwrap()
+                            .into_iter()
+                            .find(|a| a.is_html())
+                            .unwrap_or(&body),
+                        context,
+                    )));
+                    self.mode = ViewMode::Subview;
+                }
                 ViewMode::Subview | ViewMode::ContactSelector(_) => {}
                 ViewMode::Raw => {
                     let text = {
diff --git a/ui/src/conf.rs b/ui/src/conf.rs
index ab15904b..550ab3d8 100644
--- a/ui/src/conf.rs
+++ b/ui/src/conf.rs
@@ -46,7 +46,7 @@ use self::terminal::TerminalSettings;
 use crate::pager::PagerSettings;
 use crate::plugins::Plugin;
 use melib::backends::SpecialUsageMailbox;
-use melib::conf::{toggleflag_de, AccountSettings, FolderConf, ToggleFlag};
+use melib::conf::{AccountSettings, FolderConf, ToggleFlag};
 use melib::error::*;
 
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
@@ -454,6 +454,10 @@ mod default_vals {
     pub(in crate::conf) fn internal_value_false() -> super::ToggleFlag {
         super::ToggleFlag::InternalVal(false)
     }
+
+    pub(in crate::conf) fn internal_value_true() -> super::ToggleFlag {
+        super::ToggleFlag::InternalVal(true)
+    }
 }
 
 mod deserializers {
diff --git a/ui/src/conf/notifications.rs b/ui/src/conf/notifications.rs
index beeac081..028d4fa9 100644
--- a/ui/src/conf/notifications.rs
+++ b/ui/src/conf/notifications.rs
@@ -20,7 +20,6 @@
  */
 
 use super::default_vals::internal_value_false;
-use super::toggleflag_de;
 
 fn none() -> Option<String> {
     None
@@ -38,7 +37,7 @@ pub struct NotificationsSettings {
     /// Default: None
     #[serde(default = "none")]
     pub xbiff_file_path: Option<String>,
-    #[serde(deserialize_with = "toggleflag_de", default = "internal_value_false")]
+    #[serde(default = "internal_value_false")]
     pub play_sound: super::ToggleFlag,
     #[serde(default = "none")]
     pub sound_file: Option<String>,
diff --git a/ui/src/conf/pager.rs b/ui/src/conf/pager.rs
index 39dde1c6..40c11d12 100644
--- a/ui/src/conf/pager.rs
+++ b/ui/src/conf/pager.rs
@@ -21,6 +21,8 @@
 
 use super::default_vals::*;
 use super::deserializers::*;
+use melib::ToggleFlag;
+
 /// Settings for the pager function.
 #[derive(Debug, Deserialize, Clone, Default, Serialize)]
 pub struct PagerSettings {
@@ -68,6 +70,12 @@ pub struct PagerSettings {
     /// Default: 80
     #[serde(default = "eighty_val")]
     pub minimum_width: usize,
+
+    /// Choose `text/html` alternative if `text/plain` is empty in `multipart/alternative`
+    /// attachments.
+    /// Default: true
+    #[serde(default = "internal_value_true")]
+    pub auto_choose_multipart_alternative: ToggleFlag,
 }
 
 fn eighty_val() -> usize {