From 3f6049b17c506b1103ea13786d2773446fdebfbc Mon Sep 17 00:00:00 2001
From: Sivansh Gupta <76725678+sivansh11@users.noreply.github.com>
Date: Thu, 20 Nov 2025 14:33:06 +0530
Subject: [PATCH] feat: `D` to describe a change in log buffer (#23)

---
 lua/jj/cmd.lua   | 69 +++++++++++++++++++++++++++++++++++-------------
 lua/jj/utils.lua | 20 ++++++++------
 2 files changed, 63 insertions(+), 26 deletions(-)

diff --git a/lua/jj/cmd.lua b/lua/jj/cmd.lua
index 560dba7..67e93e5 100644
--- a/lua/jj/cmd.lua
+++ b/lua/jj/cmd.lua
@@ -36,7 +36,9 @@ local state = {
 
 --- Close the current terminal buffer if it exists
 local function close_terminal_buffer()
-	if state.buf and vim.api.nvim_buf_is_valid(state.buf) then
+  if not state.buf then
+    return
+  elseif state.buf and vim.api.nvim_buf_is_valid(state.buf) then
 		vim.cmd("bwipeout! " .. state.buf)
 	else
 		vim.cmd("close")
@@ -421,6 +423,17 @@ local function handle_log_diff()
 	end
 end
 
+--- Handle describign a log line
+local function handle_log_describe()
+	local line = vim.api.nvim_get_current_line()
+	local revset = get_rev_from_log_line(line)
+	if revset then
+    M.describe(nil, revset)
+	else
+		utils.notify("No valid revision found in the log line", vim.log.levels.ERROR)
+	end
+end
+
 --- Run a command and show it's output in a terminal buffer
 --- If a previous command already existed it smartly reuses the buffer cleaning the previous output
 ---@param cmd string
@@ -594,6 +607,7 @@ local function run(cmd)
 		register_command_keymap({ "n" }, "r", function()
 			M.redo()
 		end, { desc = "Redo last operation" })
+		register_command_keymap({ "n" }, "D", handle_log_describe, { desc = "Describe change under cursor" })
 	end
 
 	if #new_command_keymaps > 0 then
@@ -627,17 +641,25 @@ end
 
 --- Execute jj describe command with the given description
 ---@param description string The description text
-local function execute_describe(description)
+local function execute_describe(description, revset)
 	if not description or description == "" then
 		utils.notify("Description cannot be empty", vim.log.levels.ERROR)
 		return
 	end
-
-	-- Use --stdin to properly handle multi-line and special characters
-	local _, success = utils.execute_command("jj describe --stdin", "Failed to describe", description)
-	if success then
-		utils.notify("Description set.", vim.log.levels.INFO)
-	end
+  if revset == nil then
+	  -- Use --stdin to properly handle multi-line and special characters
+	  local _, success = utils.execute_command("jj describe --stdin", "Failed to describe", description)
+	  if success then
+	  	utils.notify("Description set.", vim.log.levels.INFO)
+	  end
+  else
+	  -- Use --stdin to properly handle multi-line and special characters
+    local cmd = "jj describe -r " .. revset .. " --stdin"
+	  local _, success = utils.execute_command(cmd, "Failed to describe", description)
+	  if success then
+	  	utils.notify("Description set.", vim.log.levels.INFO)
+	  end
+  end
 end
 
 --- @class jj.cmd.describe_opts
@@ -651,28 +673,38 @@ local default_describe_opts = {
 --- Jujutsu describe
 ---@param description? string Optional description text
 ---@param opts? jj.cmd.describe_opts Optional command options
-function M.describe(description, opts)
+function M.describe(description, revset, opts)
 	if not utils.ensure_jj() then
 		return
-	end
+  end
 
 	-- Check if a description was provided otherwise require for input
 	if description then
 		-- Description provided directly
-		execute_describe(description)
+		execute_describe(description, revset)
 	else
 		-- Use buffer editor mode
 		if M.config.describe_editor == "buffer" then
 			-- Build initial lines
-			local status_files = utils.get_status_files()
-			local text = { "JJ: This commit contains the following changes:" }
+      if not revset then
+        revset = '@'
+      end
+      local cmd = "jj log -r " .. revset .. " --no-graph -T 'coalesce(description, \"(no description set)\n\")'"
+      local old_description_raw, success = utils.execute_command(cmd, "Failed to get old description")
+	    if not old_description_raw or not success then
+	    	return 
+	    end
+      local old_description = vim.trim(old_description_raw)
+      local status_files = utils.get_status_files(revset)
+			local text = { old_description }
+			table.insert(text, "") -- Empty line to separate from user input
+      table.insert(text, "JJ: Change ID: " .. revset)
+			table.insert(text, "JJ: This commit contains the following changes:")
 			for _, item in ipairs(status_files) do
 				table.insert(text, string.format("JJ:     %s %s", item.status, item.file))
 			end
 			table.insert(text, "JJ:") -- blank line
-			table.insert(text, 'JJ: Lines starting with "JJ:" (like this one) will be ignored when finalizing')
-			table.insert(text, "") -- Empty line to separate from user input
-			table.insert(text, "") -- Another empty line where user can start typing
+			table.insert(text, 'JJ: Lines starting with "JJ:" (like this one) will be removed')
 
 			utils.open_ephemeral_buffer(text, function(buf_lines)
 				local user_lines = {}
@@ -683,8 +715,9 @@ function M.describe(description, opts)
 				end
 				-- Join lines and trim leading/trailing whitespace
 				local trimmed_description = table.concat(user_lines, "\n"):gsub("^%s+", ""):gsub("%s+$", "")
-				execute_describe(trimmed_description)
+				execute_describe(trimmed_description, revset)
 			end)
+			close_terminal_buffer()
 		else
 			local merged_opts = vim.tbl_deep_extend("force", default_describe_opts, opts or {})
 			if merged_opts.with_status then
@@ -698,7 +731,7 @@ function M.describe(description, opts)
 			}, function(input)
 				-- If the user inputed something, execute the describe command
 				if input then
-					execute_describe(input)
+					execute_describe(input, revset)
 				end
 				-- Close the current terminal when finished
 				close_terminal_buffer()
diff --git a/lua/jj/utils.lua b/lua/jj/utils.lua
index d42ee9a..90a8308 100644
--- a/lua/jj/utils.lua
+++ b/lua/jj/utils.lua
@@ -158,12 +158,17 @@ end
 
 --- Get a list of files with their status in the current jj repository.
 --- @return table[] A list of tables with {status = string, file = string}
-function M.get_status_files()
+function M.get_status_files(revset)
 	if not M.ensure_jj() then
 		return {}
 	end
 
-	local result, success = M.execute_command("jj status", "Error getting status")
+  if revset == nil then
+    revset = '@'
+  end
+
+  cmd = "jj log -r " .. revset .. " --no-graph -T 'self.diff().summary()'"
+	local result, success = M.execute_command(cmd, "Error getting status")
 	if not success or not result then
 		return {}
 	end
@@ -304,12 +309,11 @@ function M.open_ephemeral_buffer(initial_text, on_done)
 
 	-- Position cursor at the end (after the last JJ: line) and enter insert mode
 	vim.schedule(function()
-		-- Get the number of lines in the buffer
-		local line_count = vim.api.nvim_buf_line_count(buf)
-		-- Move cursor to the last line, column 0
-		vim.api.nvim_win_set_cursor(0, { line_count, 0 })
-		-- Enter insert mode
-		vim.cmd("startinsert")
+    local line_count = vim.api.nvim_buf_line_count(buf)
+    local target_line_idx = line_count - 1 -- 0-indexed line number for API calls
+    local last_line_content = vim.api.nvim_buf_get_lines(buf, target_line_idx, line_count, false)[1]
+    local col_index = #last_line_content
+    vim.api.nvim_win_set_cursor(0, { 1, 0 })
 	end)
 
 	-- Handle :w and :wq commands