rudimentary file preview support

 - this currently has only been tested with text files
 - no line formatting is done yet
 - only prints the preview as a single line
 - folder previews can now be pushed onto a separate thread if needed

4 files changed, 119 insertions, 14 deletions

diff --git a/src/ui/tui_backend.rs b/src/ui/tui_backend.rs
index f04450d..cf32c01 100644
--- a/src/ui/tui_backend.rs
+++ b/src/ui/tui_backend.rs
@@ -4,11 +4,14 @@ use std::io::Write;
 use termion::raw::{IntoRawMode, RawTerminal};
 use termion::screen::AlternateScreen;
 use tui::backend::TermionBackend;
-use tui::widgets::Widget;
+use tui::layout::{Constraint, Direction, Layout, Rect};
+use tui::widgets::{Block, Borders, Widget};
 
 #[cfg(feature = "mouse")]
 use termion::input::MouseTerminal;
 
+use crate::util::display::DisplayOption;
+
 trait New {
     fn new() -> std::io::Result<Self>
     where
@@ -81,3 +84,50 @@ impl TuiBackend {
         Ok(())
     }
 }
+
+pub fn build_layout(
+    area: Rect,
+    constraints: &[Constraint; 3],
+    display_options: &DisplayOption,
+) -> Vec<Rect> {
+    let layout_rect = if display_options.show_borders() {
+        let area = Rect {
+            y: area.top() + 1,
+            height: area.height - 2,
+            ..area
+        };
+
+        let block = Block::default().borders(Borders::ALL);
+        let inner = block.inner(area);
+
+        let layout_rect = Layout::default()
+            .direction(Direction::Horizontal)
+            .constraints(constraints.as_ref())
+            .split(inner);
+
+        let block = Block::default().borders(Borders::RIGHT);
+        let inner1 = block.inner(layout_rect[0]);
+
+        let block = Block::default().borders(Borders::LEFT);
+        let inner3 = block.inner(layout_rect[2]);
+
+        vec![inner1, layout_rect[1], inner3]
+    } else {
+        let mut layout_rect = Layout::default()
+            .direction(Direction::Horizontal)
+            .vertical_margin(1)
+            .constraints(constraints.as_ref())
+            .split(area);
+
+        layout_rect[0] = Rect {
+            width: layout_rect[0].width - 1,
+            ..layout_rect[0]
+        };
+        layout_rect[1] = Rect {
+            width: layout_rect[1].width - 1,
+            ..layout_rect[1]
+        };
+        layout_rect
+    };
+    layout_rect
+}
diff --git a/src/ui/views/tui_folder_view.rs b/src/ui/views/tui_folder_view.rs
index be3909a..e391473 100644
--- a/src/ui/views/tui_folder_view.rs
+++ b/src/ui/views/tui_folder_view.rs
@@ -6,7 +6,10 @@ use tui::text::Span;
 use tui::widgets::{Block, Borders, Paragraph, Widget, Wrap};
 
 use crate::context::AppContext;
-use crate::ui::widgets::{TuiDirList, TuiDirListDetailed, TuiFooter, TuiTabBar, TuiTopBar};
+use crate::ui;
+use crate::ui::widgets::{
+    TuiDirList, TuiDirListDetailed, TuiFilePreview, TuiFooter, TuiTabBar, TuiTopBar,
+};
 
 const TAB_VIEW_WIDTH: u16 = 15;
 
@@ -26,22 +29,33 @@ impl<'a> TuiFolderView<'a> {
 
 impl<'a> Widget for TuiFolderView<'a> {
     fn render(self, area: Rect, buf: &mut Buffer) {
+        let preview_context = self.context.preview_context_ref();
         let curr_tab = self.context.tab_context_ref().curr_tab_ref();
 
         let curr_list = curr_tab.curr_list_ref();
         let parent_list = curr_tab.parent_list_ref();
         let child_list = curr_tab.child_list_ref();
 
+        let curr_entry = curr_list.and_then(|c| c.curr_entry_ref());
+
         let config = self.context.config_ref();
+        let display_options = config.display_options_ref();
 
-        let constraints: &[Constraint; 3] = if !config.display_options_ref().collapse_preview() {
-            &config.display_options_ref().default_layout
-        } else {
-            match child_list {
-                Some(_) => &config.display_options_ref().default_layout,
-                None => &config.display_options_ref().no_preview_layout,
-            }
-        };
+        let (default_layout, constraints): (bool, &[Constraint; 3]) =
+            if !display_options.collapse_preview() {
+                (true, &display_options.default_layout)
+            } else {
+                match child_list {
+                    Some(_) => (true, &display_options.default_layout),
+                    None => match curr_entry {
+                        None => (false, &display_options.no_preview_layout),
+                        Some(e) => match preview_context.get_preview(e.file_path()) {
+                            Some(_) => (true, &display_options.default_layout),
+                            None => (false, &display_options.no_preview_layout),
+                        },
+                    },
+                }
+            };
 
         let layout_rect = if config.display_options_ref().show_borders() {
             let area = Rect {
@@ -73,7 +87,7 @@ impl<'a> Widget for TuiFolderView<'a> {
                 };
 
                 intersections.render_left(buf);
-                if child_list.as_ref().is_some() {
+                if default_layout {
                     intersections.render_right(buf);
                 }
             }
@@ -108,7 +122,7 @@ impl<'a> Widget for TuiFolderView<'a> {
         // render parent view
         if let Some(list) = parent_list.as_ref() {
             TuiDirList::new(&list).render(layout_rect[0], buf);
-        };
+        }
 
         // render current view
         if let Some(list) = curr_list.as_ref() {
@@ -137,12 +151,16 @@ impl<'a> Widget for TuiFolderView<'a> {
                     TuiFooter::new(list).render(rect, buf);
                 }
             }
-        };
+        }
 
         // render preview
         if let Some(list) = child_list.as_ref() {
             TuiDirList::new(&list).render(layout_rect[2], buf);
-        };
+        } else if let Some(entry) = curr_entry {
+            if let Some(preview) = preview_context.get_preview(entry.file_path()) {
+                TuiFilePreview::new(entry, preview).render(layout_rect[2], buf);
+            }
+        }
 
         let topbar_width = area.width;
         let rect = Rect {
diff --git a/src/ui/widgets/mod.rs b/src/ui/widgets/mod.rs
index 451ccdb..6319d91 100644
--- a/src/ui/widgets/mod.rs
+++ b/src/ui/widgets/mod.rs
@@ -1,5 +1,6 @@
 mod tui_dirlist;
 mod tui_dirlist_detailed;
+mod tui_file_preview;
 mod tui_footer;
 mod tui_menu;
 mod tui_prompt;
@@ -10,6 +11,7 @@ mod tui_worker;
 
 pub use self::tui_dirlist::TuiDirList;
 pub use self::tui_dirlist_detailed::{trim_file_label, TuiDirListDetailed};
+pub use self::tui_file_preview::TuiFilePreview;
 pub use self::tui_footer::TuiFooter;
 pub use self::tui_menu::TuiMenu;
 pub use self::tui_prompt::TuiPrompt;
diff --git a/src/ui/widgets/tui_file_preview.rs b/src/ui/widgets/tui_file_preview.rs
new file mode 100644
index 0000000..f731a0e
--- /dev/null
+++ b/src/ui/widgets/tui_file_preview.rs
@@ -0,0 +1,35 @@
+use std::process;
+
+use tui::buffer::Buffer;
+use tui::layout::Rect;
+use tui::style::{Color, Modifier, Style};
+use tui::widgets::Widget;
+
+use crate::fs::JoshutoDirEntry;
+use crate::preview::preview_file::FilePreview;
+use crate::util::format;
+use crate::util::string::UnicodeTruncate;
+use crate::util::style;
+use unicode_width::UnicodeWidthStr;
+
+const MIN_LEFT_LABEL_WIDTH: i32 = 15;
+
+const ELLIPSIS: &str = "…";
+
+pub struct TuiFilePreview<'a> {
+    entry: &'a JoshutoDirEntry,
+    preview: &'a FilePreview,
+}
+
+impl<'a> TuiFilePreview<'a> {
+    pub fn new(entry: &'a JoshutoDirEntry, preview: &'a FilePreview) -> Self {
+        Self { entry, preview }
+    }
+}
+
+impl<'a> Widget for TuiFilePreview<'a> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        let style = Style::default();
+        buf.set_string(area.x, area.y, self.preview.output.as_str(), style);
+    }
+}