feat(ui): Rework how highlights are applied to outlines

* Previously we used vim's pattern matching which is not a great way to
  do this in neovim, as tree-sitter doesn't support it.

* Now we use the neovim apis which are range based

lua/symbols-outline.lua

@@ -13,8 +13,8 @@ local function setup_global_autocmd()
     vim.cmd "au CursorHold * :lua require('symbols-outline')._highlight_current_item()"
   end
 
-vim.cmd "au InsertLeave,WinEnter,BufEnter,BufWinEnter,TabEnter,BufWritePost * :lua require('symbols-outline')._refresh()"
+  vim.cmd "au InsertLeave,WinEnter,BufEnter,BufWinEnter,TabEnter,BufWritePost * :lua require('symbols-outline')._refresh()"
-vim.cmd "au WinEnter * lua require'symbols-outline.preview'.close()"
+  vim.cmd "au WinEnter * lua require'symbols-outline.preview'.close()"
 end
 
 -------------------------
@@ -177,7 +177,6 @@ local function handler(response)
   M.state.flattened_outline_items = parser.flatten(items)
 
   writer.parse_and_write(M.view.bufnr, M.state.flattened_outline_items)
-  ui.setup_highlights()
 
   M._highlight_current_item(M.state.code_win)
 end
@@ -202,6 +201,7 @@ end
 
 function M.setup(opts)
   config.setup(opts)
+  ui.setup_highlights()
 
   M.view = View:new()
   setup_global_autocmd()

lua/symbols-outline/parser.lua

@@ -180,19 +180,22 @@ end
 function M.get_lines(flattened_outline_items)
   local lines = {}
   local hl_info = {}
-  for _, value in ipairs(flattened_outline_items) do
+
-    local line = str_to_table(string.rep(' ', value.depth))
+  for node_line, node in ipairs(flattened_outline_items) do
+    local line = str_to_table(string.rep(' ', node.depth))
 
     if config.options.show_guides then
       -- makes the guides
       for index, _ in ipairs(line) do
+        local guide_hl_type = 'SymbolsOutlineConnector'
         -- all items start with a space (or two)
         if index == 1 then
           line[index] = ' '
+          guide_hl_type = 'Normal'
           -- if index is last, add a bottom marker if current item is last,
           -- else add a middle marker
         elseif index == #line then
-          if value.isLast then
+          if node.isLast then
             line[index] = ui.markers.bottom
           else
             line[index] = ui.markers.middle
@@ -200,25 +203,30 @@ function M.get_lines(flattened_outline_items)
           -- else if the parent was not the last in its group, add a
           -- vertical marker because there are items under us and we need
           -- to point to those
-        elseif not value.hierarchy[index] then
+        elseif not node.hierarchy[index] then
           line[index] = ui.markers.vertical
         end
+
+        line[index] = line[index] .. ' '
+
+        local guide_hl_start = index * 2
+        local guide_hl_end = index * 2 + #line[index]
+
+        table.insert(
+          hl_info,
+          { node_line, guide_hl_start, guide_hl_end, guide_hl_type }
+        )
       end
     end
 
-    local final_prefix = {}
+    local final_prefix = line
-    -- Add 1 space between the guides
-    for _, v in ipairs(line) do
-      table.insert(final_prefix, v)
-      table.insert(final_prefix, ' ')
-    end
 
     local string_prefix = table_to_str(final_prefix)
     local hl_start = #string_prefix
-    local hl_end = #string_prefix + #value.icon
+    local hl_end = #string_prefix + #node.icon
-    table.insert(lines, string_prefix .. value.icon .. ' ' .. value.name)
+    table.insert(lines, string_prefix .. node.icon .. ' ' .. node.name)
-    local hl_type = config.options.symbols[symbols.kinds[value.kind]].hl
+    local hl_type = config.options.symbols[symbols.kinds[node.kind]].hl
-    table.insert(hl_info, { hl_start, hl_end, hl_type })
+    table.insert(hl_info, { node_line, hl_start, hl_end, hl_type })
   end
   return lines, hl_info
 end

lua/symbols-outline/ui.lua

@@ -1,4 +1,3 @@
-local vim = vim
 local M = {}
 
 M.markers = {
@@ -25,11 +24,6 @@ function M.add_hover_highlight(bufnr, line, col_start)
   )
 end
 
-local function highlight_text(name, text, hl_group)
-  vim.cmd(string.format('syn match %s /%s/', name, text))
-  vim.cmd(string.format('hi def link %s %s', name, hl_group))
-end
-
 function M.setup_highlights()
   -- Setup the FocusedSymbol highlight group if it hasn't been done already by
   -- a theme or manually set
@@ -52,20 +46,6 @@ function M.setup_highlights()
       string.format('hi SymbolsOutlineConnector guifg=%s', comment_fg_gui)
     )
   end
-
-  -- markers
-  highlight_text('marker_middle', M.markers.middle, 'SymbolsOutlineConnector')
-  highlight_text(
-    'marker_vertical',
-    M.markers.vertical,
-    'SymbolsOutlineConnector'
-  )
-  highlight_text(
-    'markers_horizontal',
-    M.markers.horizontal,
-    'SymbolsOutlineConnector'
-  )
-  highlight_text('markers_bottom', M.markers.bottom, 'SymbolsOutlineConnector')
 end
 
 return M

lua/symbols-outline/writer.lua

@@ -24,8 +24,8 @@ function M.write_outline(bufnr, lines)
 end
 
 function M.add_highlights(bufnr, hl_info)
-  for line, line_hl in ipairs(hl_info) do
+  for _, line_hl in ipairs(hl_info) do
-    local hl_start, hl_end, hl_type = unpack(line_hl)
+    local line, hl_start, hl_end, hl_type = unpack(line_hl)
     vim.api.nvim_buf_add_highlight(
       bufnr,
       hlns,