Add comment generator (#10)

* feat(_utils.ts): get package

* feat(_utils.ts): get interface

* feat(_utils.ts): update type annotations

* feat(comments): first naive implementation

* docs: add comment [skip ci]

lua/gopher/comment.lua

@@ -0,0 +1,50 @@
+local ts_utils = require "gopher._utils.ts"
+
+local function generate(row, col)
+  local comment, ns = nil, nil
+
+  ns = ts_utils.get_package_node_at_pos(row, col)
+  if ns ~= nil and ns ~= {} then
+    comment = "// Package " .. ns.name .. " provides " .. ns.name
+    return comment, ns
+  end
+
+  ns = ts_utils.get_struct_node_at_pos(row, col)
+  if ns ~= nil and ns ~= {} then
+    comment = "// " .. ns.name .. " " .. ns.type .. " "
+    return comment, ns
+  end
+
+  ns = ts_utils.get_func_method_node_at_pos(row, col)
+  if ns ~= nil and ns ~= {} then
+    comment = "// " .. ns.name .. " " .. ns.type .. " "
+    return comment, ns
+  end
+
+  ns = ts_utils.get_interface_node_at_pos(row, col)
+  if ns ~= nil and ns ~= {} then
+    comment = "// " .. ns.name .. " " .. ns.type .. " "
+    return comment, ns
+  end
+
+  return "// ", {}
+end
+
+return function()
+  local row, col = unpack(vim.api.nvim_win_get_cursor(0))
+  local comment, ns = generate(row + 1, col + 1)
+
+  vim.api.nvim_win_set_cursor(0, {
+    ns.dim.s.r,
+    ns.dim.s.c,
+  })
+
+  vim.fn.append(row - 1, comment)
+
+  vim.api.nvim_win_set_cursor(0, {
+    ns.dim.s.r,
+    #comment + 1,
+  })
+
+  vim.cmd [[startinsert!]]
+end