feat(cable): support for custom preview offset parsing for cable channels

cable/unix-channels.toml

@@ -8,8 +8,9 @@ preview_command = "bat -n --color=always {}"
 [[cable_channel]]
 name = "text"
 source_command = "rg . --no-heading --line-number"
-preview_command = "bat -n --color=always {0} -H {1}"
+preview_command = "bat -n --color=always {0}"
 preview_delimiter = ":"
+preview_offset = "{1}"
 
 # Directories
 [[cable_channel]]

television/channels/cable.rs

@@ -14,6 +14,8 @@ use crate::matcher::Matcher;
 use crate::matcher::{config::Config, injector::Injector};
 use crate::utils::command::shell_command;
 
+use super::prototypes::format_prototype_string;
+
 pub struct Channel {
     pub name: String,
     matcher: Matcher<String>,
@@ -94,8 +96,27 @@ impl Channel {
 
     pub fn get_result(&self, index: u32) -> Option<Entry> {
         self.matcher.get_result(index).map(|item| {
-            let path = item.matched_string;
-            Entry::new(path)
+            let name = item.matched_string;
+            if let Some(cmd) = &self.preview_command {
+                if let Some(offset_expr) = &cmd.offset_expr {
+                    let offset_string = format_prototype_string(
+                        offset_expr,
+                        &name,
+                        &cmd.delimiter,
+                    );
+                    let offset_str = {
+                        offset_string
+                            .strip_prefix('\'')
+                            .and_then(|s| s.strip_suffix('\''))
+                            .unwrap_or(&offset_string)
+                    };
+
+                    return Entry::new(name).with_line_number(
+                        offset_str.parse::<usize>().unwrap(),
+                    );
+                }
+            }
+            Entry::new(name)
         })
     }
 

television/channels/preview.rs

@@ -2,12 +2,10 @@ use std::fmt::Display;
 
 use crate::channels::{
     entry::Entry,
-    prototypes::{ChannelPrototype, DEFAULT_DELIMITER},
+    prototypes::{
+        format_prototype_string, ChannelPrototype, DEFAULT_DELIMITER,
+    },
 };
-use lazy_regex::{regex, Lazy, Regex};
-use tracing::debug;
-
-static CMD_RE: &Lazy<Regex> = regex!(r"\{(\d+)\}");
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash, Default)]
 pub struct PreviewCommand {
@@ -47,23 +45,7 @@ impl PreviewCommand {
     /// assert_eq!(formatted_command, "something 'a:given:entry:to:preview' 'entry' 'a'");
     /// ```
     pub fn format_with(&self, entry: &Entry) -> String {
-        let parts = entry.name.split(&self.delimiter).collect::<Vec<&str>>();
-
-        let mut formatted_command = self
-            .command
-            .replace("{}", format!("'{}'", entry.name).as_str());
-        debug!("FORMATTED_COMMAND: {formatted_command}");
-        debug!("PARTS: {parts:?}");
-
-        formatted_command = CMD_RE
-            .replace_all(&formatted_command, |caps: &regex::Captures| {
-                let index =
-                    caps.get(1).unwrap().as_str().parse::<usize>().unwrap();
-                format!("'{}'", parts[index])
-            })
-            .to_string();
-
-        formatted_command
+        format_prototype_string(&self.command, &entry.name, &self.delimiter)
     }
 }
 

television/channels/prototypes.rs

@@ -1,3 +1,4 @@
+use lazy_regex::{regex, Lazy, Regex};
 use rustc_hash::FxHashMap;
 use std::{
     fmt::{self, Display, Formatter},
@@ -126,6 +127,29 @@ impl Display for ChannelPrototype {
     }
 }
 
+pub static CMD_RE: &Lazy<Regex> = regex!(r"\{(\d+)\}");
+
+pub fn format_prototype_string(
+    template: &str,
+    source: &str,
+    delimiter: &str,
+) -> String {
+    let parts = source.split(delimiter).collect::<Vec<&str>>();
+
+    let mut formatted_string =
+        template.replace("{}", format!("'{}'", source).as_str());
+
+    formatted_string = CMD_RE
+        .replace_all(&formatted_string, |caps: &regex::Captures| {
+            let index =
+                caps.get(1).unwrap().as_str().parse::<usize>().unwrap();
+            format!("'{}'", parts[index])
+        })
+        .to_string();
+
+    formatted_string
+}
+
 /// A neat `HashMap` of channel prototypes indexed by their name.
 ///
 /// This is used to store cable channel prototypes throughout the application

television/cli/args.rs

@@ -25,6 +25,14 @@ pub struct Cli {
     #[arg(short, long, value_name = "STRING", verbatim_doc_comment)]
     pub preview: Option<String>,
 
+    /// A preview line number offset template to use to scroll the preview to for each
+    /// entry.
+    ///
+    /// This template uses the same syntax as the `preview` option and will be formatted
+    /// using the currently selected entry.
+    #[arg(long, value_name = "STRING", verbatim_doc_comment)]
+    pub preview_offset: Option<String>,
+
     /// Disable the preview panel entirely on startup.
     #[arg(long, default_value = "false", verbatim_doc_comment)]
     pub no_preview: bool,

television/cli/mod.rs

@@ -75,8 +75,7 @@ impl From<Cli> for PostProcessedCli {
         let preview_command = cli.preview.map(|preview| PreviewCommand {
             command: preview,
             delimiter: cli.delimiter.clone(),
-            // TODO: add the --preview-offset option to the CLI
-            offset_expr: None,
+            offset_expr: cli.preview_offset.clone(),
         });
 
         let mut channel: ChannelPrototype;

television/previewer/state.rs

@@ -9,7 +9,7 @@ pub struct PreviewState {
 }
 
 const PREVIEW_MIN_SCROLL_LINES: u16 = 3;
-pub const ANSI_BEFORE_CONTEXT_SIZE: u16 = 10;
+pub const ANSI_BEFORE_CONTEXT_SIZE: u16 = 3;
 const ANSI_CONTEXT_SIZE: usize = 500;
 
 impl PreviewState {
@@ -51,7 +51,7 @@ impl PreviewState {
         scroll: u16,
         target_line: Option<u16>,
     ) {
-        if self.preview.title != preview.title {
+        if self.preview.title != preview.title || self.scroll != scroll {
             self.preview = preview;
             self.scroll = scroll;
             self.target_line = target_line;
@@ -59,16 +59,31 @@ impl PreviewState {
     }
 
     pub fn for_render_context(&self) -> Self {
-        let skipped_lines =
+        let num_skipped_lines =
             self.scroll.saturating_sub(ANSI_BEFORE_CONTEXT_SIZE);
         let cropped_content = self
             .preview
             .content
             .lines()
-            .skip(skipped_lines as usize)
+            .skip(num_skipped_lines as usize)
             .take(ANSI_CONTEXT_SIZE)
             .collect::<Vec<_>>()
             .join("\n");
+
+        let target_line: Option<u16> =
+            if let Some(target_line) = self.target_line {
+                if num_skipped_lines < target_line
+                    && (target_line - num_skipped_lines)
+                        <= u16::try_from(ANSI_CONTEXT_SIZE).unwrap()
+                {
+                    Some(target_line.saturating_sub(num_skipped_lines))
+                } else {
+                    None
+                }
+            } else {
+                None
+            };
+
         PreviewState::new(
             self.enabled,
             Preview::new(
@@ -77,8 +92,8 @@ impl PreviewState {
                 self.preview.icon,
                 self.preview.total_lines,
             ),
-            skipped_lines,
-            self.target_line,
+            num_skipped_lines,
+            target_line,
         )
     }
 }

television/screen/preview.rs

@@ -32,13 +32,19 @@ pub fn draw_preview_content_block(
         use_nerd_font_icons,
     )?;
     // render the preview content
-    let rp = build_preview_paragraph(&preview_state.preview.content);
+    let rp = build_preview_paragraph(
+        preview_state,
+        colorscheme.preview.highlight_bg,
+    );
     f.render_widget(rp, inner);
 
     Ok(())
 }
 
-pub fn build_preview_paragraph(content: &str) -> Paragraph<'_> {
+pub fn build_preview_paragraph(
+    preview_state: &PreviewState,
+    highlight_bg: Color,
+) -> Paragraph<'_> {
     let preview_block =
         Block::default().style(Style::default()).padding(Padding {
             top: 0,
@@ -47,14 +53,30 @@ pub fn build_preview_paragraph(content: &str) -> Paragraph<'_> {
             left: 1,
         });
 
-    build_ansi_text_paragraph(content, preview_block)
+    build_ansi_text_paragraph(
+        &preview_state.preview.content,
+        preview_block,
+        preview_state.target_line,
+        highlight_bg,
+    )
 }
 
 fn build_ansi_text_paragraph<'a>(
     text: &'a str,
     preview_block: Block<'a>,
+    target_line: Option<u16>,
+    highlight_bg: Color,
 ) -> Paragraph<'a> {
-    Paragraph::new(text.into_text().unwrap()).block(preview_block)
+    let mut t = text.into_text().unwrap();
+    if let Some(target_line) = target_line {
+        // Highlight the target line
+        if let Some(line) = t.lines.get_mut((target_line - 1) as usize) {
+            for span in &mut line.spans {
+                span.style = span.style.bg(highlight_bg);
+            }
+        }
+    }
+    Paragraph::new(t).block(preview_block)
 }
 
 pub fn build_meta_preview_paragraph<'a>(

television/television.rs

@@ -416,10 +416,7 @@ impl Television {
             // available previews
             let entry = selected_entry.as_ref().unwrap();
             if let Ok(preview) = receiver.try_recv() {
-                self.preview_state.update(
-                    preview,
-                    // scroll to center the selected entry
-                    entry
+                let scroll = entry
                     .line_number
                     .unwrap_or(0)
                     .saturating_sub(
@@ -427,14 +424,18 @@ impl Television {
                             .ui_state
                             .layout
                             .preview_window
-                                .map_or(0, |w| w.height)
+                            .map_or(0, |w| w.height.saturating_sub(2)) // borders
                             / 2)
                         .into(),
                     )
+                    .saturating_add(3) // 3 lines above the center
                     .try_into()
                     // if the scroll doesn't fit in a u16, just scroll to the top
                     // this is a current limitation of ratatui
-                        .unwrap_or(0),
+                    .unwrap_or(0);
+                self.preview_state.update(
+                    preview,
+                    scroll,
                     entry.line_number.and_then(|l| l.try_into().ok()),
                 );
                 self.action_tx.send(Action::Render)?;