gopher.nvim/lua/gopher/_utils/ts.lua

local ts = {}
local queries = {
  struct = [[
    [(type_spec name: (type_identifier) @_name
                type: (struct_type))
     (var_declaration (var_spec
                        name: (identifier) @_name @_var
                        type: (struct_type)))
     (short_var_declaration
       left:  (expression_list (identifier) @_name @_var)
       right: (expression_list (composite_literal
                                 type: (struct_type))))]
  ]],
  func = [[
    [(function_declaration name: (identifier)       @_name)
     (method_declaration   name: (field_identifier) @_name)]
  ]],
  package = [[
    (package_identifier) @_name
  ]],
  interface = [[
    (type_spec
      name: (type_identifier) @_name
      type: (interface_type))
  ]],
}

---@param parent_type string[]
---@param node TSNode
---@return TSNode?
local function get_parrent_node(parent_type, node)
  ---@type TSNode?
  local current = node
  while current do
    if vim.tbl_contains(parent_type, current:type()) then
      break
    end

    current = current:parent()
    if current == nil then
      return nil
    end
  end
  return current
end

---@param query vim.treesitter.Query
---@param node TSNode
---@param bufnr integer
---@return {name:string, is_varstruct:boolean}
local function get_captures(query, node, bufnr)
  local res = {}
  for id, _node in query:iter_captures(node, bufnr) do
    if query.captures[id] == "_name" then
      res["name"] = vim.treesitter.get_node_text(_node, bufnr)
    end

    if query.captures[id] == "_var" then
      res["is_varstruct"] = true
    end
  end

  return res
end

---@class gopher.TsResult
---@field name string
---@field start integer
---@field end_ integer
---@field is_varstruct boolean

---@param bufnr integer
---@param parent_type string[]
---@param query string
---@return gopher.TsResult
local function do_stuff(bufnr, parent_type, query)
  if not vim.treesitter.get_parser(bufnr, "go") then
    error "No treesitter parser found for go"
  end

  local node = vim.treesitter.get_node {
    bufnr = bufnr,
  }
  if not node then
    error "No nodes found under cursor"
  end

  local parent_node = get_parrent_node(parent_type, node)
  if not parent_node then
    error "No parent node found under cursor"
  end

  local q = vim.treesitter.query.parse("go", query)
  local res = get_captures(q, parent_node, bufnr)
  assert(res.name ~= nil, "No capture name found")

  local start_row, _, end_row, _ = parent_node:range()
  res["start"] = start_row + 1
  res["end_"] = end_row + 1

  return res
end

---@param bufnr integer
function ts.get_struct_under_cursor(bufnr)
  --- should be both type_spec and type_declaration
  --- because in cases like `type ( T struct{}, U strict{} )`
  --- i will be choosing always last struct in the list
  ---
  --- var_declaration is for cases like `var x struct{}`
  --- short_var_declaration is for cases like `x := struct{}{}`
  return do_stuff(bufnr, {
    "type_spec",
    "type_declaration",
    "var_declaration",
    "short_var_declaration",
  }, queries.struct)
end

---@param bufnr integer
function ts.get_func_under_cursor(bufnr)
  --- since this handles both and funcs and methods we should check for both parent nodes
  return do_stuff(bufnr, { "function_declaration", "method_declaration" }, queries.func)
end

---@param bufnr integer
function ts.get_package_under_cursor(bufnr)
  return do_stuff(bufnr, { "package_clause" }, queries.package)
end

---@param bufnr integer
function ts.get_interface_under_cursor(bufnr)
  return do_stuff(bufnr, { "type_declaration" }, queries.interface)
end

return ts