feat(plugin-api): allow replacing pane with existing pane (#4246)

* work

* make the api work

* some cleanups

* close pane

* style(fmt): rustfmt

9 files changed, 164 insertions, 10 deletions

diff --git a/zellij-server/src/plugins/zellij_exports.rs b/zellij-server/src/plugins/zellij_exports.rs
index b928b224..7b682f6d 100644
--- a/zellij-server/src/plugins/zellij_exports.rs
+++ b/zellij-server/src/plugins/zellij_exports.rs
@@ -495,6 +495,14 @@ fn host_run_plugin_command(mut caller: Caller<'_, PluginEnv>) {
                     PluginCommand::ClearKeyPressesIntercepts => {
                         clear_key_presses_intercepts(&mut env)
                     },
+                    PluginCommand::ReplacePaneWithExistingPane(
+                        pane_id_to_replace,
+                        existing_pane_id,
+                    ) => replace_pane_with_existing_pane(
+                        &mut env,
+                        pane_id_to_replace.into(),
+                        existing_pane_id.into(),
+                    ),
                 },
                 (PermissionStatus::Denied, permission) => {
                     log::error!(
@@ -2455,6 +2463,19 @@ fn clear_key_presses_intercepts(env: &mut PluginEnv) {
         .send_to_screen(ScreenInstruction::ClearKeyPressesIntercepts(env.client_id));
 }
 
+fn replace_pane_with_existing_pane(
+    env: &mut PluginEnv,
+    pane_to_replace: PaneId,
+    existing_pane: PaneId,
+) {
+    let _ = env
+        .senders
+        .send_to_screen(ScreenInstruction::ReplacePaneWithExistingPane(
+            pane_to_replace,
+            existing_pane,
+        ));
+}
+
 // Custom panic handler for plugins.
 //
 // This is called when a panic occurs in a plugin. Since most panics will likely originate in the
@@ -2621,6 +2642,7 @@ fn check_command_permission(
         | PluginCommand::CloseMultiplePanes(..)
         | PluginCommand::FloatMultiplePanes(..)
         | PluginCommand::EmbedMultiplePanes(..)
+        | PluginCommand::ReplacePaneWithExistingPane(..)
         | PluginCommand::KillSessions(..) => PermissionType::ChangeApplicationState,
         PluginCommand::UnblockCliPipeInput(..)
         | PluginCommand::BlockCliPipeInput(..)
diff --git a/zellij-server/src/screen.rs b/zellij-server/src/screen.rs
index d1b2139c..376c726e 100644
--- a/zellij-server/src/screen.rs
+++ b/zellij-server/src/screen.rs
@@ -422,6 +422,7 @@ pub enum ScreenInstruction {
     SetMouseSelectionSupport(PaneId, bool),
     InterceptKeyPresses(PluginId, ClientId),
     ClearKeyPressesIntercepts(ClientId),
+    ReplacePaneWithExistingPane(PaneId, PaneId),
 }
 
 impl From<&ScreenInstruction> for ScreenContext {
@@ -654,6 +655,9 @@ impl From<&ScreenInstruction> for ScreenContext {
             ScreenInstruction::ClearKeyPressesIntercepts(..) => {
                 ScreenContext::ClearKeyPressesIntercepts
             },
+            ScreenInstruction::ReplacePaneWithExistingPane(..) => {
+                ScreenContext::ReplacePaneWithExistingPane
+            },
         }
     }
 }
@@ -2608,6 +2612,50 @@ impl Screen {
         }
         Ok(())
     }
+    pub fn replace_pane_with_existing_pane(
+        &mut self,
+        pane_id_to_replace: PaneId,
+        pane_id_of_existing_pane: PaneId,
+    ) {
+        let Some(tab_index_of_pane_id_to_replace) = self
+            .tabs
+            .iter()
+            .find(|(_tab_index, tab)| tab.has_pane_with_pid(&pane_id_to_replace))
+            .map(|(_tab_index, tab)| tab.position)
+        else {
+            log::error!("Could not find tab");
+            return;
+        };
+        let Some(tab_index_of_existing_pane) = self
+            .tabs
+            .iter()
+            .find(|(_tab_index, tab)| tab.has_pane_with_pid(&pane_id_of_existing_pane))
+            .map(|(_tab_index, tab)| tab.position)
+        else {
+            log::error!("Could not find tab");
+            return;
+        };
+        let Some(extracted_pane_from_other_tab) = self
+            .tabs
+            .iter_mut()
+            .find(|(_, t)| t.position == tab_index_of_existing_pane)
+            .and_then(|(_, t)| t.extract_pane(pane_id_of_existing_pane, false))
+        else {
+            log::error!("Failed to find pane");
+            return;
+        };
+        if let Some(tab) = self
+            .tabs
+            .iter_mut()
+            .find(|(_, t)| t.position == tab_index_of_pane_id_to_replace)
+        {
+            tab.1.close_pane_and_replace_with_other_pane(
+                pane_id_to_replace,
+                extracted_pane_from_other_tab,
+            );
+        }
+        let _ = self.log_and_report_session_state();
+    }
     pub fn reconfigure(
         &mut self,
         new_keybinds: Keybinds,
@@ -5488,6 +5536,9 @@ pub(crate) fn screen_thread_main(
             ScreenInstruction::ClearKeyPressesIntercepts(client_id) => {
                 keybind_intercepts.remove(&client_id);
             },
+            ScreenInstruction::ReplacePaneWithExistingPane(old_pane_id, new_pane_id) => {
+                screen.replace_pane_with_existing_pane(old_pane_id, new_pane_id)
+            },
         }
     }
     Ok(())
diff --git a/zellij-server/src/tab/mod.rs b/zellij-server/src/tab/mod.rs
index 0e4ee7fe..683a3d4a 100644
--- a/zellij-server/src/tab/mod.rs
+++ b/zellij-server/src/tab/mod.rs
@@ -1617,6 +1617,30 @@ impl Tab {
         }
         Ok(())
     }
+    pub fn close_pane_and_replace_with_other_pane(
+        &mut self,
+        pane_id_to_replace: PaneId,
+        pane_to_replace_with: Box<dyn Pane>,
+    ) {
+        let mut replaced_pane = if self.floating_panes.panes_contain(&pane_id_to_replace) {
+            self.floating_panes
+                .replace_pane(pane_id_to_replace, pane_to_replace_with)
+                .ok()
+        } else {
+            self.tiled_panes
+                .replace_pane(pane_id_to_replace, pane_to_replace_with)
+        };
+        if let Some(replaced_pane) = replaced_pane.take() {
+            let pane_id = replaced_pane.pid();
+            let _ = self.senders.send_to_pty(PtyInstruction::ClosePane(pane_id));
+            let _ = self.senders.send_to_plugin(PluginInstruction::Update(vec![(
+                None,
+                None,
+                Event::PaneClosed(pane_id.into()),
+            )]));
+            drop(replaced_pane);
+        }
+    }
     pub fn horizontal_split(
         &mut self,
         pid: PaneId,
diff --git a/zellij-tile/src/shim.rs b/zellij-tile/src/shim.rs
index 4a0945ea..608fa2e7 100644
--- a/zellij-tile/src/shim.rs
+++ b/zellij-tile/src/shim.rs
@@ -1451,6 +1451,14 @@ pub fn clear_key_presses_intercepts() {
     unsafe { host_run_plugin_command() };
 }
 
+pub fn replace_pane_with_existing_pane(pane_id_to_replace: PaneId, existing_pane_id: PaneId) {
+    let plugin_command =
+        PluginCommand::ReplacePaneWithExistingPane(pane_id_to_replace, existing_pane_id);
+    let protobuf_plugin_command: ProtobufPluginCommand = plugin_command.try_into().unwrap();
+    object_to_stdout(&protobuf_plugin_command.encode_to_vec());
+    unsafe { host_run_plugin_command() };
+}
+
 // Utility Functions
 
 #[allow(unused)]
diff --git a/zellij-utils/assets/prost/api.plugin_command.rs b/zellij-utils/assets/prost/api.plugin_command.rs
index 52a8cd42..e3c63626 100644
--- a/zellij-utils/assets/prost/api.plugin_command.rs
+++ b/zellij-utils/assets/prost/api.plugin_command.rs
@@ -3,7 +3,7 @@
 pub struct PluginCommand {
     #[prost(enumeration="CommandName", tag="1")]
     pub name: i32,
-    #[prost(oneof="plugin_command::Payload", tags="2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110")]
+    #[prost(oneof="plugin_command::Payload", tags="2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111")]
     pub payload: ::core::option::Option<plugin_command::Payload>,
 }
 /// Nested message and enum types in `PluginCommand`.
@@ -211,10 +211,20 @@ pub mod plugin_command {
         RevokeWebLoginTokenPayload(super::RevokeWebLoginTokenPayload),
         #[prost(message, tag="110")]
         RenameWebLoginTokenPayload(super::RenameWebLoginTokenPayload),
+        #[prost(message, tag="111")]
+        ReplacePaneWithExistingPanePayload(super::ReplacePaneWithExistingPanePayload),
     }
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
+pub struct ReplacePaneWithExistingPanePayload {
+    #[prost(message, optional, tag="1")]
+    pub pane_id_to_replace: ::core::option::Option<PaneId>,
+    #[prost(message, optional, tag="2")]
+    pub existing_pane_id: ::core::option::Option<PaneId>,
+}
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
 pub struct RenameWebLoginTokenPayload {
     #[prost(string, tag="1")]
     pub old_name: ::prost::alloc::string::String,
@@ -1013,6 +1023,7 @@ pub enum CommandName {
     RenameWebLoginToken = 142,
     InterceptKeyPresses = 143,
     ClearKeyPressesIntercepts = 144,
+    ReplacePaneWithExistingPane = 155,
 }
 impl CommandName {
     /// String value of the enum field names used in the ProtoBuf definition.
@@ -1166,6 +1177,7 @@ impl CommandName {
             CommandName::RenameWebLoginToken => "RenameWebLoginToken",
             CommandName::InterceptKeyPresses => "InterceptKeyPresses",
             CommandName::ClearKeyPressesIntercepts => "ClearKeyPressesIntercepts",
+            CommandName::ReplacePaneWithExistingPane => "ReplacePaneWithExistingPane",
         }
     }
     /// Creates an enum from field names used in the ProtoBuf definition.
@@ -1316,6 +1328,7 @@ impl CommandName {
             "RenameWebLoginToken" => Some(Self::RenameWebLoginToken),
             "InterceptKeyPresses" => Some(Self::InterceptKeyPresses),
             "ClearKeyPressesIntercepts" => Some(Self::ClearKeyPressesIntercepts),
+            "ReplacePaneWithExistingPane" => Some(Self::ReplacePaneWithExistingPane),
             _ => None,
         }
     }
diff --git a/zellij-utils/src/data.rs b/zellij-utils/src/data.rs
index c6b6dcad..0520e15d 100644
--- a/zellij-utils/src/data.rs
+++ b/zellij-utils/src/data.rs
@@ -2496,4 +2496,5 @@ pub enum PluginCommand {
     RenameWebLoginToken(String, String), // (original_name, new_name)
     InterceptKeyPresses,
     ClearKeyPressesIntercepts,
+    ReplacePaneWithExistingPane(PaneId, PaneId), // (pane id to replace, pane id of existing)
 }
diff --git a/zellij-utils/src/errors.rs b/zellij-utils/src/errors.rs
index 4d647eee..b4082cd1 100644
--- a/zellij-utils/src/errors.rs
+++ b/zellij-utils/src/errors.rs
@@ -387,6 +387,7 @@ pub enum ScreenContext {
     SetMouseSelectionSupport,
     InterceptKeyPresses,
     ClearKeyPressesIntercepts,
+    ReplacePaneWithExistingPane,
 }
 
 /// Stack call representations corresponding to the different types of [`PtyInstruction`]s.
diff --git a/zellij-utils/src/plugin_api/plugin_command.proto b/zellij-utils/src/plugin_api/plugin_command.proto
index 4c1db71f..b1797214 100644
--- a/zellij-utils/src/plugin_api/plugin_command.proto
+++ b/zellij-utils/src/plugin_api/plugin_command.proto
@@ -158,6 +158,7 @@ enum CommandName {
   RenameWebLoginToken = 142;
   InterceptKeyPresses = 143;
   ClearKeyPressesIntercepts = 144;
+  ReplacePaneWithExistingPane = 155;
 }
 
 message PluginCommand {
@@ -263,9 +264,15 @@ message PluginCommand {
     GenerateWebLoginTokenPayload generate_web_login_token_payload = 108;
     RevokeWebLoginTokenPayload revoke_web_login_token_payload = 109;
     RenameWebLoginTokenPayload rename_web_login_token_payload = 110;
+    ReplacePaneWithExistingPanePayload replace_pane_with_existing_pane_payload = 111;
   }
 }
 
+message ReplacePaneWithExistingPanePayload {
+  PaneId pane_id_to_replace = 1;
+  PaneId existing_pane_id = 2;
+}
+
 message RenameWebLoginTokenPayload {
   string old_name = 1;
   string new_name = 2;
diff --git a/zellij-utils/src/plugin_api/plugin_command.rs b/zellij-utils/src/plugin_api/plugin_command.rs
index 7fb583b7..296a8a74 100644
--- a/zellij-utils/src/plugin_api/plugin_command.rs
+++ b/zellij-utils/src/plugin_api/plugin_command.rs
@@ -26,15 +26,15 @@ pub use super::generated_api::api::{
         PaneIdAndFloatingPaneCoordinates, PaneType as ProtobufPaneType,
         PluginCommand as ProtobufPluginCommand, PluginMessagePayload, RebindKeysPayload,
         ReconfigurePayload, ReloadPluginPayload, RenameWebLoginTokenPayload,
-        RenameWebTokenResponse, RequestPluginPermissionPayload, RerunCommandPanePayload,
-        ResizePaneIdWithDirectionPayload, ResizePayload, RevokeAllWebTokensResponse,
-        RevokeTokenResponse, RevokeWebLoginTokenPayload, RunCommandPayload,
-        ScrollDownInPaneIdPayload, ScrollToBottomInPaneIdPayload, ScrollToTopInPaneIdPayload,
-        ScrollUpInPaneIdPayload, SetFloatingPanePinnedPayload, SetSelfMouseSelectionSupportPayload,
-        SetTimeoutPayload, ShowPaneWithIdPayload, StackPanesPayload, SubscribePayload,
-        SwitchSessionPayload, SwitchTabToPayload, TogglePaneEmbedOrEjectForPaneIdPayload,
-        TogglePaneIdFullscreenPayload, UnsubscribePayload, WebRequestPayload,
-        WriteCharsToPaneIdPayload, WriteToPaneIdPayload,
+        RenameWebTokenResponse, ReplacePaneWithExistingPanePayload, RequestPluginPermissionPayload,
+        RerunCommandPanePayload, ResizePaneIdWithDirectionPayload, ResizePayload,
+        RevokeAllWebTokensResponse, RevokeTokenResponse, RevokeWebLoginTokenPayload,
+        RunCommandPayload, ScrollDownInPaneIdPayload, ScrollToBottomInPaneIdPayload,
+        ScrollToTopInPaneIdPayload, ScrollUpInPaneIdPayload, SetFloatingPanePinnedPayload,
+        SetSelfMouseSelectionSupportPayload, SetTimeoutPayload, ShowPaneWithIdPayload,
+        StackPanesPayload, SubscribePayload, SwitchSessionPayload, SwitchTabToPayload,
+        TogglePaneEmbedOrEjectForPaneIdPayload, TogglePaneIdFullscreenPayload, UnsubscribePayload,
+        WebRequestPayload, WriteCharsToPaneIdPayload, WriteToPaneIdPayload,
     },
     plugin_permission::PermissionType as ProtobufPermissionType,
     resize::ResizeAction as ProtobufResizeAction,
@@ -1711,6 +1711,22 @@ impl TryFrom<ProtobufPluginCommand> for PluginCommand {
                 Some(_) => Err("ClearKeyPressesIntercepts should have no payload, found a payload"),
                 None => Ok(PluginCommand::ClearKeyPressesIntercepts),
             },
+            Some(CommandName::ReplacePaneWithExistingPane) => match protobuf_plugin_command.payload
+            {
+                Some(Payload::ReplacePaneWithExistingPanePayload(
+                    replace_pane_with_other_pane_payload,
+                )) => Ok(PluginCommand::ReplacePaneWithExistingPane(
+                    replace_pane_with_other_pane_payload
+                        .pane_id_to_replace
+                        .and_then(|p_id| PaneId::try_from(p_id).ok())
+                        .ok_or("Failed to parse ReplacePaneWithExistingPanePayload")?,
+                    replace_pane_with_other_pane_payload
+                        .existing_pane_id
+                        .and_then(|p_id| PaneId::try_from(p_id).ok())
+                        .ok_or("Failed to parse ReplacePaneWithExistingPanePayload")?,
+                )),
+                _ => Err("Mismatched payload for ReplacePaneWithExistingPane"),
+            },
             None => Err("Unrecognized plugin command"),
         }
     }
@@ -2848,6 +2864,17 @@ impl TryFrom<PluginCommand> for ProtobufPluginCommand {
                 name: CommandName::ClearKeyPressesIntercepts as i32,
                 payload: None,
             }),
+            PluginCommand::ReplacePaneWithExistingPane(pane_id_to_replace, existing_pane_id) => {
+                Ok(ProtobufPluginCommand {
+                    name: CommandName::ReplacePaneWithExistingPane as i32,
+                    payload: Some(Payload::ReplacePaneWithExistingPanePayload(
+                        ReplacePaneWithExistingPanePayload {
+                            pane_id_to_replace: ProtobufPaneId::try_from(pane_id_to_replace).ok(),
+                            existing_pane_id: ProtobufPaneId::try_from(existing_pane_id).ok(),
+                        },
+                    )),
+                })
+            },
         }
     }
 }