feat(api): Get symbol and breadcrumb at location

Currently the implementation is very limited.

Ref: #24

- Outline must be open and have been loaded for it to work (requires
  lazy loading or headless loading of Sidebar)
- Empty string returned if cursor is not in any symbol ('closest' symbol
  not yet supported)
- Line column not used
- Returning concatenated symbol names rather than a list of tables with
  node info (requires a refactor of outline.SymbolNode type)
- Subject to config.symbols.filter and folds (requires finding hover
  list somewhere outside of writer.make_outline)

lua/outline/init.lua

@@ -120,13 +120,14 @@ end
 function M.open_outline(opts)
   local tab = vim.api.nvim_get_current_tabpage()
   local sidebar = M.sidebars[tab]
-  M.current = sidebar
 
   if not sidebar then
     sidebar = Sidebar:new()
     M.sidebars[tab] = sidebar
   end
 
+  M.current = sidebar
+
   return sidebar:open(opts)
 end
 
@@ -135,6 +136,85 @@ function M.is_focus_in_outline()
   return M._sidebar_do('has_focus')
 end
 
+M.has_focus = M.is_focus_in_outline
+
+---@return boolean
+function M.is_open()
+  local sidebar = M._get_sidebar()
+  if sidebar then
+    return sidebar.view:is_open()
+  end
+  return false
+end
+
+---@param sidebar outline.Sidebar
+---@param opts outline.BreadcrumbOpts
+---@return string
+local function _get_breadcrumb(sidebar, opts)
+  local list = sidebar.hovered
+  -- TODO: Use cursor column in writer.make_outline to prevent
+  -- siblings being included
+  local names = {}
+  for _, node in ipairs(list) do
+    if node.depth > opts.depth then
+      break
+    end
+    names[node.depth] = node.name
+  end
+
+  return table.concat(names, opts.sep)
+end
+
+---@param opts outline.BreadcrumbOpts?
+---@return string? breadcrumb nil if outline not open
+function M.get_breadcrumb(opts)
+  local sidebar = M._get_sidebar()
+
+  if not sidebar then
+    return
+  end
+
+  opts = opts or {}
+  opts.sep = opts.sep or ' > '
+  if not opts.depth or opts.depth < 1 then
+    opts.depth = math.huge
+  end
+
+  return _get_breadcrumb(sidebar, opts)
+end
+
+---@param opts outline.SymbolOpts
+---@return string?
+function M.get_symbol(opts)
+  local sidebar = M._get_sidebar()
+  if not sidebar then
+    return
+  end
+
+  opts = opts or {}
+  local depth = opts.depth
+  if not opts.depth or opts.depth < 1 then
+    depth = math.huge
+  end
+
+  if not utils.table_has_content(sidebar.hovered) then
+    return ""
+  end
+
+  local kind
+  if opts.kind then
+    kind = require('outline.symbols').str_to_kind[opts.kind]
+  end
+
+  for i = #sidebar.hovered, 1, -1 do
+    local node = sidebar.hovered[i]
+    if node.depth <= depth and (not kind or node.kind == kind) then
+      return node.name
+    end
+  end
+  return ""
+end
+
 ---Handle follow cursor command with bang
 local function _cmd_follow_cursor(opts)
   M.follow_cursor({ focus_outline = not opts.bang })

lua/outline/providers/coc.lua

@@ -28,12 +28,7 @@ end
 ---@param result table
 local function convert_symbols(result)
   local s = {}
-  local kinds_index = {}
-  -- create a inverse indexing of symbols.kind
-  local symbols = require('outline.symbols')
-  for k, v in pairs(symbols.kinds) do
-    kinds_index[v] = k
-  end
+  local kinds_index = require('outline.symbol').str_to_kind
   -- rebuild coc.nvim symbol list hierarchy according to the 'level' key
   for _, value in pairs(result) do
     value.children = {}

lua/outline/sidebar.lua

@@ -17,6 +17,7 @@ local Sidebar = {}
 ---@field view outline.View
 ---@field items outline.SymbolNode[]
 ---@field flats outline.FlatSymbolNode[]
+---@field hovered outline.FlatSymbolNode[]
 ---@field original_cursor string
 ---@field code outline.SidebarCodeState
 ---@field autocmds { [integer]: integer } winnr to autocmd id
@@ -27,6 +28,7 @@ function Sidebar:new()
     code = { buf = 0, win = 0 },
     items = {},
     flats = {},
+    hovered = {},
     autocmds = {},
     original_cursor = vim.o.guicursor,
   }, { __index = Sidebar })
@@ -94,7 +96,7 @@ function Sidebar:initial_handler(response, opts)
   self.items = items
 
   local current
-  self.flats, current = writer.make_outline(self.view.bufnr, items, self.code.win)
+  self.flats, current, self.hovered = writer.make_outline(self.view.bufnr, items, self.code.win)
 
   self:update_cursor_pos(current)
 
@@ -261,7 +263,7 @@ end
 ---@param set_cursor_to_node outline.SymbolNode|outline.FlatSymbolNode?
 function Sidebar:_update_lines(update_cursor, set_cursor_to_node)
   local current
-  self.flats, current =
+  self.flats, current, self.hovered =
     writer.make_outline(self.view.bufnr, self.items, self.code.win, set_cursor_to_node)
   if update_cursor ~= false then
     self:update_cursor_pos(current)

lua/outline/symbols.lua

@@ -39,6 +39,12 @@ M.kinds = {
   [255] = 'Macro',
 }
 
+-- inverse indexing of symbols.kind
+M.str_to_kind = {}
+for k, v in pairs(M.kinds) do
+  M.str_to_kind[v] = k
+end
+
 ---@param kind string|integer
 function M.icon_from_kind(kind)
   local kindstr = kind

lua/outline/types/outline.lua

@@ -93,3 +93,11 @@
 ---@class outline.OutlineOpts
 ---@field focus_outline boolean?  Whether to focus on outline of after some operation. If nil, defaults to true
 ---@field split_command string?
+
+---@class outline.BreadcrumbOpts
+---@field depth integer?
+---@field sep string?
+
+---@class outline.SymbolOpts
+---@field depth integer?
+---@field kind string?

lua/outline/writer.lua

@@ -68,16 +68,17 @@ end
 ---@param items outline.SymbolNode[] Tree of symbols after being parsed by parser.parse_result
 ---@param codewin integer code window
 ---@param find_node outline.FlatSymbolNode|outline.SymbolNode? Find a given node rather than node matching cursor position in codewin
----@return outline.FlatSymbolNode[],outline.FlatSymbolNode? flattened_items Empty table returned if bufnr is invalid
+---@return outline.FlatSymbolNode[],outline.FlatSymbolNode?,outline.FlatSymbolNode[]? flattened_items Empty table returned if bufnr is invalid
 function M.make_outline(bufnr, items, codewin, find_node)
   if not M.is_buffer_outline(bufnr) then
-    return {}, nil
+    return {}, nil, {}
   end
   local codebuf = vim.api.nvim_win_get_buf(codewin)
   -- 0-indexed
   local hovered_line = vim.api.nvim_win_get_cursor(codewin)[1] - 1
   -- Deepest matching node to put cursor on based on hovered line
   local put_cursor
+  local hover_list = {}
 
   clear_virt_text(bufnr)
 
@@ -144,6 +145,7 @@ function M.make_outline(bufnr, items, codewin, find_node)
       -- XXX: not setting for children, but it works because when unfold is called
       -- this function is called again anyway.
       node.hovered = true
+      table.insert(hover_list, node)
       if not find_node then
         put_cursor = node
       end
@@ -270,7 +272,7 @@ function M.make_outline(bufnr, items, codewin, find_node)
     end
   end
 
-  return flattened, put_cursor
+  return flattened, put_cursor, hover_list
 end
 -- XXX: Is the performance tradeoff of calling `nvim_buf_set_lines` on each
 -- iteration worth it in order to put setting of highlights, details, and