Add xplr.util.layout_replaced (#574)

Closes: https://github.com/sayanarijit/xplr/issues/573

src/lua/util.rs

@@ -5,6 +5,7 @@ use crate::msg::in_::external::ExplorerConfig;
 use crate::path;
 use crate::path::RelativityConfig;
 use crate::ui;
+use crate::ui::Layout;
 use crate::ui::Style;
 use crate::ui::WrapOptions;
 use anyhow::Result;
@@ -42,6 +43,7 @@ pub(crate) fn create_table(lua: &Lua) -> Result<Table> {
     util = relative_to(util, lua)?;
     util = shortened(util, lua)?;
     util = textwrap(util, lua)?;
+    util = layout_replaced(util, lua)?;
 
     Ok(util)
 }
@@ -511,3 +513,49 @@ pub fn textwrap<'a>(util: Table<'a>, lua: &Lua) -> Result<Table<'a>> {
     util.set("textwrap", func)?;
     Ok(util)
 }
+
+/// Find the target layout in the given layout and replace it with the replacement layout,
+/// returning a new layout.
+///
+/// Type: function( layout:[Layout][4], target:[Layout][4], replacement:[Layout][4] ) -> layout:[Layout][4]
+///
+/// Example:
+///
+/// ```lua
+/// local layout = {
+///   Horizontal = {
+///     splits = {
+///       "Table",  -- Target
+///       "HelpMenu",
+///     },
+///     config = ...,
+///   }
+/// }
+///
+/// xplr.util.layout_replaced(layout, "Table", "Selection")
+/// -- {
+/// --   Horizontal = {
+/// --     splits = {
+/// --       "Selection",  -- Replaced
+/// --       "HelpMenu",
+/// --     },
+/// --     config = ...
+/// --   }
+/// -- }
+/// ```
+pub fn layout_replaced<'a>(util: Table<'a>, lua: &Lua) -> Result<Table<'a>> {
+    let func = lua.create_function(
+        move |lua, (layout, target, replacement): (Table, Table, Table)| {
+            let layout: Layout = lua.from_value(Value::Table(layout))?;
+            let target: Layout = lua.from_value(Value::Table(target))?;
+            let replacement: Layout = lua.from_value(Value::Table(replacement))?;
+
+            let res = layout.replace(&target, &replacement);
+            let res = lua.to_value(&res)?;
+
+            Ok(res)
+        },
+    )?;
+    util.set("layout_replaced", func)?;
+    Ok(util)
+}

src/ui.rs

@@ -168,6 +168,32 @@ impl Layout {
             (_, other) => other.to_owned(),
         }
     }
+
+    pub fn replace(self, target: &Self, replacement: &Self) -> Self {
+        match self {
+            Self::Horizontal { splits, config } => Self::Horizontal {
+                splits: splits
+                    .into_iter()
+                    .map(|s| s.replace(target, replacement))
+                    .collect(),
+                config,
+            },
+            Self::Vertical { splits, config } => Self::Vertical {
+                splits: splits
+                    .into_iter()
+                    .map(|s| s.replace(target, replacement))
+                    .collect(),
+                config,
+            },
+            other => {
+                if other == *target {
+                    replacement.to_owned()
+                } else {
+                    other
+                }
+            }
+        }
+    }
 }
 
 #[derive(
@@ -1540,4 +1566,42 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn test_layout_replace() {
+        let layout = Layout::Horizontal {
+            config: LayoutOptions {
+                margin: Some(2),
+                horizontal_margin: Some(3),
+                vertical_margin: Some(4),
+                constraints: Some(vec![
+                    Constraint::Percentage(80),
+                    Constraint::Percentage(20),
+                ]),
+            },
+            splits: vec![Layout::Table, Layout::HelpMenu],
+        };
+
+        let res = layout.clone().replace(&Layout::Table, &Layout::Selection);
+
+        match (res, layout) {
+            (
+                Layout::Horizontal {
+                    config: res_config,
+                    splits: res_splits,
+                },
+                Layout::Horizontal {
+                    config: layout_config,
+                    splits: layout_splits,
+                },
+            ) => {
+                assert_eq!(res_config, layout_config);
+                assert_eq!(res_splits.len(), layout_splits.len());
+                assert_eq!(res_splits[0], Layout::Selection);
+                assert_ne!(res_splits[0], layout_splits[0]);
+                assert_eq!(res_splits[1], layout_splits[1]);
+            }
+            _ => panic!("Unexpected layout"),
+        }
+    }
 }