local ls = require "luasnip"

local snippet_from_nodes = ls.sn
local c = ls.choice_node
local t = ls.text_node
local d = ls.dynamic_node
local i = ls.insert_node
local rep = require("luasnip.extras").rep
local fmt = require("luasnip.extras.fmt").fmt

local get_node_text = vim.treesitter.get_node_text

vim.treesitter.query.set(
  "go",
  "LuaSnip_Result",
  [[
  [
    (method_declaration result: (_) @id)
    (function_declaration result: (_) @id)
    (func_literal result: (_) @id)
  ]
]]
)

local transform = function(text, info)
  if text == "int" then
    return t "0"
  elseif text == "error" then
    if info then
      info.index = info.index + 1

      return c(info.index, {
        t(string.format('fmt.Errorf("%s %%w", %s)', info.func_name, info.err_name)),
        t(info.err_name),
      })
    else
      return t "err"
    end
  elseif text == "bool" then
    return t "false"
  elseif text == "string" then
    return t '""'
  elseif string.find(text, "*", 1, true) then
    return t "nil"
  end

  return t(text)
end

local handlers = {
  ["parameter_list"] = function(node, info)
    local result = {}

    local count = node:named_child_count()
    for idx = 0, count - 1 do
      table.insert(result, transform(get_node_text(node:named_child(idx), 0), info))
      if idx ~= count - 1 then
        table.insert(result, t { ", " })
      end
    end

    return result
  end,

  ["type_identifier"] = function(node, info)
    local text = get_node_text(node, 0)
    return { transform(text, info) }
  end,
}

-- `nvim-treesitter.locals`/`ts_utils` no existen en la rama `main`; subimos a
-- mano por los padres del nodo bajo el cursor hasta la función que lo contiene.
local function go_result_type(info)
  local function_node
  local node = vim.treesitter.get_node()
  while node do
    local kind = node:type()
    if kind == "function_declaration" or kind == "method_declaration" or kind == "func_literal" then
      function_node = node
      break
    end
    node = node:parent()
  end

  if not function_node then
    return
  end

  local query = vim.treesitter.query.get("go", "LuaSnip_Result")
  if not query then
    return
  end
  for _, node in query:iter_captures(function_node, 0) do
    if handlers[node:type()] then
      return handlers[node:type()](node, info)
    end
  end
end

local go_ret_vals = function(args)
  local info = { index = 0, err_name = args[1][1], func_name = args[2][1] }
  return snippet_from_nodes(nil, go_result_type(info))
end

local M = {
  main = {
    t { "func main() {", "\t" },
    i(0),
    t { "", "}" },
  },
  ef = {
    i(1, { "val" }),
    t ", err := ",
    i(2, { "f" }),
    t "(",
    i(3),
    t ")",
    i(0),
  },
  efi = {
    i(1, { "val" }),
    ", ",
    i(2, { "err" }),
    " := ",
    i(3, { "f" }),
    "(",
    i(4),
    ")",
    t { "", "if " },
    rep(2),
    t { " != nil {", "\treturn " },
    d(5, go_ret_vals, { 2, 3 }),
    t { "", "}" },
    i(0),
  },
}

M.f = fmt("func {}({}) {} {{\n\t{}\n}}", { i(1, "name"), i(2), i(3), i(0) })

return M