---@toc_entry Generate comments
---@tag gopher.nvim-comments
---@text
--- This module provides a way to generate comments for Go code.
---
---@usage
--- Set cursor on line with function/method/struct/etc and
--- run `:GoCmt` to generate a comment.

local ts = require "gopher._utils.ts"
local log = require "gopher._utils.log"
local u = require "gopher._utils"
local comment = {}

--- NOTE: The order of functions executed inside this function is IMPORTANT.
--- This function is extremely fragile; run tests after making any changes.
---
---@param bufnr integer
---@param line string
---@return string
---@dochide
local function generate(bufnr, line)
  local sf_ok, sf_res = pcall(ts.get_struct_field_under_cursor, bufnr)
  if sf_ok then
    return u.indent(line, sf_res.indent) .. "// " .. sf_res.name .. " "
  end

  local s_ok, s_res = pcall(ts.get_struct_under_cursor, bufnr)
  if s_ok then
    return u.indent(line, s_res.indent) .. "// " .. s_res.name .. " "
  end

  local v_ok, v_res = pcall(ts.get_variable_under_cursor, bufnr)
  if v_ok then
    return u.indent(line, v_res.indent) .. "// " .. v_res.name .. " "
  end

  local f_ok, f_res = pcall(ts.get_func_under_cursor, bufnr)
  if f_ok then
    return u.indent(line, f_res.indent) .. "// " .. f_res.name .. " "
  end

  local i_ok, i_res = pcall(ts.get_interface_under_cursor, bufnr)
  if i_ok then
    return u.indent(line, i_res.indent) .. "// " .. i_res.name .. " "
  end

  local p_ok, p_res = pcall(ts.get_package_under_cursor, bufnr)
  if p_ok then
    return "// Package " .. p_res.name .. " provides "
  end

  return "// "
end

function comment.comment()
  local bufnr = vim.api.nvim_get_current_buf()
  local lnum = vim.fn.getcurpos()[2]
  local line = vim.fn.getline(lnum)
  local cmt = generate(bufnr, line)
  log.debug("generated comment:", {
    comment = cmt,
    line = line,
  })

  vim.fn.append(lnum - 1, cmt)
  vim.fn.setpos(".", { bufnr, lnum, #cmt })
  vim.cmd "startinsert!"
end

return comment