From 7f0bd43b34e6c79b6c96f8fa76d33ef554dbc159 Mon Sep 17 00:00:00 2001
From: Barrett Ruth <br.barrettruth@gmail.com>
Date: Tue, 24 Feb 2026 22:01:57 -0500
Subject: [PATCH] feat(buffer): preserve category fold state across re-renders

Problem: pressing :w, toggling priority, or any other operation that
calls buffer.render() reset foldlevel = 99, causing all manually
collapsed category sections to snap back open.

Solution: snapshot which categories are folded (per window) before
nvim_buf_set_lines destroys the fold tree, then restore them after
fold options are re-applied by calling normal! zc on each previously
closed header line. State persists across all render call sites
within a session.
---
 lua/pending/buffer.lua | 48 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/lua/pending/buffer.lua b/lua/pending/buffer.lua
index 2036357..861aca3 100644
--- a/lua/pending/buffer.lua
+++ b/lua/pending/buffer.lua
@@ -12,6 +12,8 @@ local task_ns = vim.api.nvim_create_namespace('pending')
 local current_view = nil
 ---@type pending.LineMeta[]
 local _meta = {}
+---@type table<integer, table<string, boolean>>
+local _fold_state = {}
 
 ---@return pending.LineMeta[]
 function M.meta()
@@ -148,6 +150,50 @@ local function setup_highlights()
   vim.api.nvim_set_hl(0, 'PendingPriority', { link = 'DiagnosticWarn', default = true })
 end
 
+local function snapshot_folds(bufnr)
+  if current_view ~= 'category' then
+    return
+  end
+  for _, winid in ipairs(vim.fn.win_findbuf(bufnr)) do
+    local state = {}
+    vim.api.nvim_win_call(winid, function()
+      for lnum, m in ipairs(_meta) do
+        if m.type == 'header' and m.category then
+          if vim.fn.foldclosed(lnum) ~= -1 then
+            state[m.category] = true
+          end
+        end
+      end
+    end)
+    _fold_state[winid] = state
+  end
+end
+
+local function restore_folds(bufnr)
+  if current_view ~= 'category' then
+    return
+  end
+  for _, winid in ipairs(vim.fn.win_findbuf(bufnr)) do
+    local state = _fold_state[winid]
+    if not state or next(state) == nil then
+      goto continue
+    end
+    vim.api.nvim_win_call(winid, function()
+      vim.cmd('normal! zx')
+      local saved = vim.api.nvim_win_get_cursor(0)
+      for lnum, m in ipairs(_meta) do
+        if m.type == 'header' and m.category and state[m.category] then
+          vim.api.nvim_win_set_cursor(0, { lnum, 0 })
+          vim.cmd('normal! zc')
+        end
+      end
+      vim.api.nvim_win_set_cursor(0, saved)
+    end)
+    _fold_state[winid] = nil
+    ::continue::
+  end
+end
+
 ---@param bufnr? integer
 function M.render(bufnr)
   bufnr = bufnr or task_bufnr
@@ -167,6 +213,7 @@ function M.render(bufnr)
 
   _meta = line_meta
 
+  snapshot_folds(bufnr)
   vim.bo[bufnr].modifiable = true
   vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines)
   vim.bo[bufnr].modified = false
@@ -185,6 +232,7 @@ function M.render(bufnr)
       vim.wo[winid].foldenable = false
     end
   end
+  restore_folds(bufnr)
 end
 
 function M.toggle_view()