fix: resolve nvim_buf_attach detachment issue

This commit fixes an issue where toggling `csvview` multiple times
without editing the buffer caused `nvim_buf_attach` to remain attached
multiple times. This led to redundant parsing and recalculation during
edits.

Changes:
- Improved logic for detaching and reattaching buffer events.
- Added `lua/csvview/buf.lua` to consolidate buffer-related utilities.
- Removed redundant code and clarified module responsibilities.

lua/csvview/buf.lua

@@ -0,0 +1,70 @@
+--- Buffer utilities
+local M = {}
+
+--- Resolve bufnr
+---@param bufnr integer| nil
+---@return integer
+function M.resolve_bufnr(bufnr)
+  if not bufnr or bufnr == 0 then
+    return vim.api.nvim_get_current_buf()
+  else
+    return bufnr
+  end
+end
+
+--- Watch buffer-update events
+---@param bufnr integer
+---@param callbacks vim.api.keyset.buf_attach
+---@return fun() detach_bufevent
+function M.attach(bufnr, callbacks)
+  local detached = false
+  local function wrap_buf_attach_handler(cb)
+    if not cb then
+      return nil
+    end
+
+    return function(...)
+      if detached then
+        return true -- detach
+      end
+
+      return cb(...)
+    end
+  end
+
+  local function attach_events()
+    vim.api.nvim_buf_attach(bufnr, false, {
+      on_lines = wrap_buf_attach_handler(callbacks.on_lines),
+      on_bytes = wrap_buf_attach_handler(callbacks.on_bytes),
+      on_changedtick = wrap_buf_attach_handler(callbacks.on_changedtick),
+      on_reload = wrap_buf_attach_handler(callbacks.on_reload),
+      on_detach = wrap_buf_attach_handler(callbacks.on_detach),
+    })
+  end
+
+  -- Attach to buffer
+  attach_events()
+
+  -- Re-register events on `:e`
+  local buf_event_auid = vim.api.nvim_create_autocmd({ "BufReadPost" }, {
+    callback = function()
+      attach_events()
+      if callbacks.on_reload then
+        callbacks.on_reload("reload", bufnr)
+      end
+    end,
+    buffer = bufnr,
+  })
+
+  -- detach
+  return function()
+    if detached then
+      return
+    end
+
+    vim.api.nvim_del_autocmd(buf_event_auid)
+    detached = true
+  end
+end
+
+return M

lua/csvview/util.lua → lua/csvview/errors.lua

@@ -1,24 +1,30 @@
+--- Error handling utilities
 local M = {}
 
+--- @class CsvView.Error
+--- @field err string error message
+--- @field stacktrace? string error stacktrace
+--- @field [string] any additional context data
+
 --- Wrap error with stacktrace for `xpcall`
----@param err string | table
----@return table
+---@param err string|CsvView.Error|nil
+---@return CsvView.Error
 function M.wrap_stacktrace(err)
   if type(err) == "table" then
-    return err
+    return vim.tbl_deep_extend("keep", err, { stacktrace = debug.traceback("", 2) })
   else
     return { err = err, stacktrace = debug.traceback("", 2) }
   end
 end
 
 --- Propagate error with context
----@param err any
----@param context table | nil
+---@param err string|CsvView.Error|nil
+---@param context table<string,any>| nil
 function M.error_with_context(err, context)
-  if type(err) == "table" then
-    err = vim.tbl_deep_extend("keep", err, context or {})
-  elseif type(err) == "string" then
+  if type(err) == "string" then
     err = vim.tbl_deep_extend("keep", { err = err }, context or {})
+  elseif type(err) == "table" then
+    err = vim.tbl_deep_extend("keep", err, context or {})
   end
   error(err, 0)
 end
@@ -27,23 +33,22 @@ end
 ---@param tbl table
 ---@param key string
 ---@return any
-function M.tbl_remove_key(tbl, key)
+local function tbl_remove_key(tbl, key)
   local value = tbl[key] ---@type any
   tbl[key] = nil ---@type any
   return value
 end
 
 --- Print error message
----@param header string
----@param err string | table
+--- @type fun(header: string, err: string|CsvView.Error|nil)
 M.print_structured_error = vim.schedule_wrap(function(header, err)
   --- @type string
   local msg
 
   if type(err) == "table" then
     -- extract error message and stacktrace
-    local stacktrace = M.tbl_remove_key(err, "stacktrace") or "No stacktrace available"
-    local err_msg = M.tbl_remove_key(err, "err") or "An unspecified error occurred"
+    local stacktrace = tbl_remove_key(err, "stacktrace") or "No stacktrace available"
+    local err_msg = tbl_remove_key(err, "err") or "An unspecified error occurred"
 
     -- format error message
     msg = string.format(

lua/csvview/init.lua

@@ -1,15 +1,20 @@
 local M = {}
 
+local CsvView = require("csvview.view").View
+local get_view = require("csvview.view").get
+local attach_view = require("csvview.view").attach
+local detach_view = require("csvview.view").detach
+local setup_view = require("csvview.view").setup
+
 local CsvViewMetrics = require("csvview.metrics")
-local buffer_event = require("csvview.buffer_event")
+local buf = require("csvview.buf")
 local config = require("csvview.config")
-local view = require("csvview.view")
 
 --- check if csv table view is enabled
 ---@param bufnr integer
 ---@return boolean
 function M.is_enabled(bufnr)
-  return view.get(bufnr) ~= nil
+  return get_view(bufnr) ~= nil
 end
 
 --- enable csv table view
@@ -24,37 +29,32 @@ function M.enable(bufnr, opts)
     return
   end
 
-  -- Calculate metrics and attach view.
+  local detach_bufevent_handle --- @type fun()
   local metrics = CsvViewMetrics:new(bufnr, opts)
-  metrics:compute_buffer(function()
-    view.attach(bufnr, metrics, opts)
+  local view = CsvView:new(bufnr, metrics, opts, function()
+    detach_bufevent_handle()
+    metrics:clear()
   end)
 
-  -- Register buffer events.
-  buffer_event.register(bufnr, {
+  -- Register buffer-update events.
+  detach_bufevent_handle = buf.attach(bufnr, {
     on_lines = function(_, _, _, first, last, last_updated)
-      -- detach if disabled
-      if not M.is_enabled(bufnr) then
-        return true
-      end
-
-      -- Recalculate only the difference.
       metrics:update(first, last, last_updated)
     end,
-
     on_reload = function()
-      -- detach if disabled
-      if not M.is_enabled(bufnr) then
-        return true
-      end
-
-      -- Recalculate all fields.
-      view.detach(bufnr)
+      view:clear()
+      metrics:clear()
+      view:lock()
       metrics:compute_buffer(function()
-        view.attach(bufnr, metrics, opts)
+        view:unlock()
       end)
     end,
   })
+
+  -- Calculate metrics and attach view.
+  metrics:compute_buffer(function()
+    attach_view(bufnr, view)
+  end)
 end
 
 --- disable csv table view
@@ -66,9 +66,7 @@ function M.disable(bufnr)
     return
   end
 
-  -- Unregister buffer events and detach view.
-  buffer_event.unregister(bufnr)
-  view.detach(bufnr)
+  detach_view(bufnr)
 end
 
 --- toggle csv table view
@@ -87,7 +85,7 @@ end
 ---@param opts CsvView.Options?
 function M.setup(opts)
   config.setup(opts)
-  view.setup()
+  setup_view()
 end
 
 return M

lua/csvview/parser.lua

@@ -1,5 +1,5 @@
 local M = {}
-local util = require("csvview.util")
+local errors = require("csvview.errors")
 
 ---@class Csvview.Parser.Callbacks
 ---@field on_line fun(lnum:integer,is_comment:boolean,fields:string[]) the callback to be called for each line
@@ -145,9 +145,9 @@ local function iter(startlnum, endlnum, bufnr, opts, cb)
   -- iterate lines
   local parsed_num = 0
   for i = startlnum, endlnum do
-    local ok, err = xpcall(parse_line, util.wrap_stacktrace, i)
+    local ok, err = xpcall(parse_line, errors.wrap_stacktrace, i)
     if not ok then
-      util.error_with_context(err, { lnum = i })
+      errors.error_with_context(err, { lnum = i })
     end
 
     -- yield every chunksize
@@ -178,16 +178,16 @@ function M.iter_lines_async(bufnr, startlnum, endlnum, cb, opts)
 
   -- create coroutine to iterate lines
   local co = coroutine.create(function() ---@async
-    local ok, err = xpcall(iter, util.wrap_stacktrace, startlnum, endlnum, bufnr, opts, cb)
+    local ok, err = xpcall(iter, errors.wrap_stacktrace, startlnum, endlnum, bufnr, opts, cb)
     if not ok then
-      util.error_with_context(err, { startlnum = startlnum, endlnum = endlnum })
+      errors.error_with_context(err, { startlnum = startlnum, endlnum = endlnum })
     end
   end)
 
   local function resume_co()
     local ok, err = coroutine.resume(co)
     if not ok then
-      util.print_structured_error("CsvView Error parsing buffer", err)
+      errors.print_structured_error("CsvView Error parsing buffer", err)
     elseif coroutine.status(co) ~= "dead" then
       vim.schedule(resume_co)
     end