feat(overseer): add Snacks output component for task display

lua/overseer/component/snacks_output.lua

@@ -0,0 +1,111 @@
+--- Overseer component: show task output in a Snacks window docked to the
+--- bottom of the editor, toggleterm-style: the window is focused and dropped
+--- into terminal mode when the task starts (and whenever the buffer is
+--- re-entered), and closes itself when the task exits.
+---
+--- The task's own terminal buffer (owned by the jobstart strategy, so exit
+--- status / output parsing keep working) is placed in a single shared
+--- bottom window. A newly started task takes the window over, so the most
+--- recent run is always the one visible. `fixbuf = false` lets overseer swap
+--- the buffer in place on restart (Task:start -> util.replace_buffer_in_wins).
+--- @module overseer.component.snacks_output
+
+--- @type snacks.win?
+local win
+
+--- @param bufnr integer
+--- @return boolean
+local function showing(bufnr)
+  return win ~= nil and win:win_valid() and vim.api.nvim_win_get_buf(win.win) == bufnr
+end
+
+--- Enter terminal mode if the task buffer is the current one. The jobstart
+--- strategy defers nvim_open_term while a floating window (the task picker)
+--- is current, so the buffer may not be a terminal yet: TermOpen fires once
+--- the deferred creation runs after our WinEnter.
+--- @param bufnr integer
+local function start_insert(bufnr)
+  if vim.api.nvim_get_current_buf() ~= bufnr then return end
+  if vim.bo[bufnr].buftype == "terminal" then
+    vim.cmd.startinsert()
+    return
+  end
+  vim.api.nvim_create_autocmd("TermOpen", {
+    buffer = bufnr,
+    once = true,
+    callback = function() vim.schedule(function() start_insert(bufnr) end) end,
+  })
+end
+
+--- @param bufnr integer
+--- @param params { height: integer, focus: boolean, auto_insert: boolean }
+local function show(bufnr, params)
+  if win and win:win_valid() then
+    if vim.api.nvim_win_get_buf(win.win) ~= bufnr then vim.api.nvim_win_set_buf(win.win, bufnr) end
+  else
+    win = require("snacks").win {
+      buf = bufnr,
+      position = "bottom",
+      height = params.height,
+      enter = false,
+      backdrop = false,
+      fixbuf = false,
+      wo = { number = false, relativenumber = false, signcolumn = "no", winbar = "", wrap = true },
+      keys = { q = "close" },
+    }
+  end
+  if params.auto_insert then
+    vim.api.nvim_create_autocmd("BufEnter", {
+      buffer = bufnr,
+      callback = function() start_insert(bufnr) end,
+    })
+  end
+  if params.focus then
+    win:focus()
+    if params.auto_insert then start_insert(bufnr) end
+  end
+end
+
+--- @type overseer.ComponentFileDefinition
+return {
+  desc = "Show task output in a Snacks window docked to the bottom",
+  params = {
+    height = {
+      desc = "Height of the bottom window in rows",
+      type = "integer",
+      default = 24,
+    },
+    focus = {
+      desc = "Focus the output window when the task starts",
+      type = "boolean",
+      default = true,
+    },
+    auto_insert = {
+      desc = "Enter terminal mode when the output buffer is focused",
+      type = "boolean",
+      default = true,
+    },
+    auto_close = {
+      desc = "Close the output window when the task exits",
+      type = "boolean",
+      default = true,
+    },
+  },
+  constructor = function(params)
+    --- @param task overseer.Task
+    local function close_if_showing(task)
+      local bufnr = task:get_bufnr()
+      if bufnr and showing(bufnr) then win:close() end
+    end
+    return {
+      on_start = function(_, task)
+        local bufnr = task:get_bufnr()
+        if bufnr then show(bufnr, params) end
+      end,
+      on_complete = function(_, task)
+        if params.auto_close then close_if_showing(task) end
+      end,
+      on_dispose = function(_, task) close_if_showing(task) end,
+    }
+  end,
+}