From 154186a58deefd4b837677a5f27000c1a3beae73 Mon Sep 17 00:00:00 2001
From: Park Juhyung <majecty@gmail.com>
Date: Sun, 21 Oct 2018 19:52:29 +0900
Subject: [PATCH] Add --pager option

---
 src/app.rs        |  4 ++++
 src/clap_app.rs   | 19 ++++++++++++++++---
 src/controller.rs |  2 +-
 src/output.rs     | 14 ++++++++------
 4 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/src/app.rs b/src/app.rs
index 06a0051f..126c718c 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -70,6 +70,9 @@ pub struct Config<'a> {
 
     /// File extension/name mappings
     pub syntax_mapping: SyntaxMapping,
+
+    /// Pager option
+    pub pager: Option<&'a str>,
 }
 
 fn is_truecolor_terminal() -> bool {
@@ -228,6 +231,7 @@ impl App {
             ),
             output_components,
             syntax_mapping,
+            pager: self.matches.value_of("pager"),
         })
     }
 
diff --git a/src/clap_app.rs b/src/clap_app.rs
index 25ed5517..7127d178 100644
--- a/src/clap_app.rs
+++ b/src/clap_app.rs
@@ -204,12 +204,25 @@ pub fn build_app(interactive_output: bool) -> ClapApp<'static, 'static> {
                 .long_help(
                     "Specify when to use the pager. To control which pager \
                      is used, set the PAGER or BAT_PAGER environment \
-                     variables (the latter takes precedence). The default \
-                     pager is 'less'. To disable the pager permanently, set \
-                     BAT_PAGER to an empty string. \
+                     variables (the latter takes precedence) or set --pager option.\
+                     The default  pager is 'less'. To disable the pager permanently,\
+                     set BAT_PAGER to an empty string. \
                      Possible values: *auto*, never, always.",
                 ),
         )
+        .arg(
+            Arg::with_name("pager")
+                .long("pager")
+                .overrides_with("pager")
+                .takes_value(true)
+                .value_name("pager-command")
+                .hidden_short_help(true)
+                .help("Set pager")
+                .long_help(
+                    "Set which pager is used. This option will overwrite \
+                    PAGER or BAT_PAGER environment variables.",
+                ),
+        )
         .arg(
             Arg::with_name("wrap")
                 .long("wrap")
diff --git a/src/controller.rs b/src/controller.rs
index bf8cef13..371ec484 100644
--- a/src/controller.rs
+++ b/src/controller.rs
@@ -19,7 +19,7 @@ impl<'b> Controller<'b> {
     }
 
     pub fn run(&self) -> Result<bool> {
-        let mut output_type = OutputType::from_mode(self.config.paging_mode)?;
+        let mut output_type = OutputType::from_mode(self.config.paging_mode, self.config.pager)?;
         let writer = output_type.handle()?;
         let mut no_errors: bool = true;
 
diff --git a/src/output.rs b/src/output.rs
index 43d0669e..66913abf 100644
--- a/src/output.rs
+++ b/src/output.rs
@@ -15,19 +15,21 @@ pub enum OutputType {
 }
 
 impl OutputType {
-    pub fn from_mode(mode: PagingMode) -> Result<Self> {
+    pub fn from_mode(mode: PagingMode, pager: Option<&str>) -> Result<Self> {
         use self::PagingMode::*;
         Ok(match mode {
-            Always => OutputType::try_pager(false)?,
-            QuitIfOneScreen => OutputType::try_pager(true)?,
+            Always => OutputType::try_pager(false, pager)?,
+            QuitIfOneScreen => OutputType::try_pager(true, pager)?,
             _ => OutputType::stdout(),
         })
     }
 
     /// Try to launch the pager. Fall back to stdout in case of errors.
-    fn try_pager(quit_if_one_screen: bool) -> Result<Self> {
-        let pager = env::var("BAT_PAGER")
-            .or_else(|_| env::var("PAGER"))
+    fn try_pager(quit_if_one_screen: bool, pager_from_config: Option<&str>) -> Result<Self> {
+        let pager_from_env = env::var("BAT_PAGER")
+            .or_else(|_| env::var("PAGER"));
+        let pager = pager_from_config.map(|p| p.to_string())
+            .or(pager_from_env.ok())
             .unwrap_or(String::from("less"));
 
         let pagerflags = shell_words::split(&pager)