From 0cf35c2b24d5ea6a9eb1a9f1a0dcdbe27bd1cc34 Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fischer@muhq.space>
Date: Tue, 29 Jul 2025 13:36:54 +0200
Subject: support navigating a file by its symbols using the message window

---
 init.lua | 131 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)

diff --git a/init.lua b/init.lua
index 29a4ed2..6e81f14 100644
--- a/init.lua
+++ b/init.lua
@@ -723,6 +723,14 @@ function LanguageServer:call_text_document_method(method, params, win, ctx)
   self:request_diagnostics(win)
 end
 
+--- Call the textDocument/symbol method of the server if provided
+function LanguageServer:request_symbols(win, ctx)
+  if self.capabilities['documentSymbolProvider'] then
+    local params = {textDocument = {uri = path_to_uri(win.file.path)}}
+    self:call_text_document_method('documentSymbol', params, win, ctx)
+  end
+end
+
 local function lspc_handle_goto_method_response(req, result)
   if not result or type(result) ~= 'table' or next(result) == nil then
     lspc:warn(req.method .. ' found no results')
@@ -960,6 +968,12 @@ local function lspc_handle_initialize_response(ls, result)
   vis.events.emit(lspc.events.LS_INITIALIZED, ls)
 end
 
+local function lspc_handle_symbol_method_response(result, ctx)
+  if ctx.callback and type(ctx.callback) == 'function' then
+    ctx.callback(result, ctx)
+  end
+end
+
 --- Dispatch method response from the server
 -- @param method_response the response send from the server
 -- @param req the request causing this response
@@ -1009,6 +1023,9 @@ function LanguageServer:handle_method_response(method_response, req)
   elseif method == 'textDocument/diagnostic' then
     lspc_handle_diagnostic_method_response(self, result, req.ctx)
 
+  elseif method == 'textDocument/documentSymbol' then
+    lspc_handle_symbol_method_response(result, req.ctx)
+
   elseif method == 'shutdown' then
     self:send_notification('exit')
     self.fd:close()
@@ -1522,6 +1539,107 @@ local function lspc_show_diagnostic(win, line)
   end
 end
 
+local lsp_symbol_kinds = {
+  'File',
+  'Module',
+  'Namespace',
+  'Package',
+  'Class',
+  'Method',
+  'Property',
+  'Field',
+  'Constructor',
+  'Enum',
+  'Interface',
+  'Function',
+  'Variable',
+  'Constant',
+  'String',
+  'Number',
+  'Boolean',
+  'Array',
+  'Object',
+  'Key',
+  'Null',
+  'EnumMember',
+  'Struct',
+  'Event',
+  'Operator',
+  'TypeParameter',
+}
+
+local function recursive_bfs_symbols_flatten(symbols, indent)
+  local ranges = {}
+  local str = ''
+  for _, s in ipairs(symbols) do
+    local range = s.selectionRange or s.location.range
+    table.insert(ranges, range)
+    str = str ..
+              string.format('%s%s %s %d:%d\n', indent, lsp_symbol_kinds[s.kind], s.name,
+                            range.start.line + 1, range.start.character + 1)
+    -- Remember DocumentSymbol.selectionRange or SymbolInformation.location.range
+    if s.children then
+      local cstr, cranges = recursive_bfs_symbols_flatten(s.children, indent .. '  ')
+      str = str .. cstr
+      for _, v in ipairs(cranges) do
+        table.insert(ranges, v)
+      end
+    end
+  end
+  return str, ranges
+end
+
+local function lspc_navwin_from_symbols(symbols, ctx)
+  local symbols_outline, ranges = recursive_bfs_symbols_flatten(symbols, '')
+
+  vis.ui.layout = vis.ui.layouts.VERTICAL
+  vis:message('')
+  local navwin = vis.win
+
+  -- Prepare message window to be our symbol navigation window.
+  navwin.file = 'symbols'
+  local navfile = navwin.file
+  assert(navwin and navwin.file)
+  assert(navfile:delete(0, navfile.size))
+  assert(navfile:insert(0, symbols_outline))
+
+  -- Create event handlers to connect the position in the navigation window to
+  -- the original window.
+  local function nav_win_win_highlight_handler()
+    if vis.win ~= navwin then
+      return
+    end
+    local line = navwin.selection.line
+    if line > #ranges then
+      return
+    end
+    local sel = lsp_pos_to_vis_sel(ranges[navwin.selection.line].start)
+    vis_open_new_doc_pos({
+      file = ctx.win.file.path,
+      line = sel.line,
+      col = sel.col,
+    }, 'e', ctx.win)
+    vis.win = navwin
+  end
+  vis.events.subscribe(vis.events.WIN_HIGHLIGHT, nav_win_win_highlight_handler)
+
+  -- Remove the event handlers.
+  local nav_win_close_handler
+  nav_win_close_handler = function(win)
+    if win ~= navwin or win ~= ctx.win then
+      return
+    end
+    vis.events.unsubscribe(vis.events.UI_DRAW, nav_win_win_highlight_handler)
+    vis.events.unsubscribe(vis.events.WIN_CLOSE, nav_win_close_handler)
+  end
+  vis.events.subscribe(vis.events.WIN_CLOSE, nav_win_close_handler)
+end
+
+local function lspc_nav_symbols(ls, win)
+  local ctx = {win = win, callback = lspc_navwin_from_symbols}
+  ls:request_symbols(win, ctx)
+end
+
 -- vis-lspc commands
 
 vis:command_register('lspc-back', function()
@@ -1748,6 +1866,19 @@ vis:command_register('lspc-show-diagnostics', function(argv, _, win)
   end
 end)
 
+vis:command_register('lspc-navigate-symbols', function(argv, _, win)
+  local ls, err = lspc_get_usable_ls(win, argv[1])
+  if err then
+    lspc:err(err)
+    return
+  end
+  assert(ls)
+  if not ls:is_file_opened(win.file.path) then
+    lspc_open(ls, win, win.file)
+  end
+  lspc_nav_symbols(ls, win)
+end, 'navigate the file by its symbols')
+
 -- vis-lspc event hooks
 vis.events.subscribe(vis.events.WIN_OPEN, function(win)
   if lspc.autostart and win.syntax then
-- 
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