local get_visual = function(args, parent)
  if #parent.snippet.env.SELECT_RAW > 0 then
    return sn(nil, i(1, parent.snippet.env.SELECT_RAW))
  else
    return sn(nil, i(1, ""))
  end
end
local function char_count_same(c1, c2)
  local line = vim.api.nvim_get_current_line()
  -- '%'-escape chars to force explicit match (gsub accepts patterns).
  -- second return value is number of substitutions.
  local _, ct1 = string.gsub(line, "%" .. c1, "")
  local _, ct2 = string.gsub(line, "%" .. c2, "")
  return ct1 == ct2
end

local function even_count(c)
  local line = vim.api.nvim_get_current_line()
  local _, ct = string.gsub(line, c, "")
  return ct % 2 == 0
end

local function neg(fn, ...)
  return not fn(...)
end

local function part(fn, ...)
  local args = { ...; }
  return function()
    return fn(unpack(args))
  end
end

-- This makes creation of pair-type snippets easier.
local function pair(pair_begin, pair_end, expand_func, ...)
  -- triggerd by opening part of pair, wordTrig=false to trigger anywhere.
  -- ... is used to pass any args following the expand_func to it.
  return s(
    { trig = pair_begin; wordTrig = false; snippetType = "autosnippet"; },
    { t({ pair_begin; }); d(1, get_visual); t({ pair_end; }); },
    { condition = part(expand_func, part(..., pair_begin, pair_end)); }
  )
end

local maybe = { pair = nil; }
if vim.bo.filetype == "tex" then
  maybe.pair = pair("<", ">", neg, char_count_same)
end

local output_table = {
  pair("(", ")", neg, char_count_same);
  pair("{", "}", neg, char_count_same);
  pair("[", "]", neg, char_count_same);
  pair("'", "'", neg, even_count);
  pair('"', '"', neg, even_count);
  pair("`", "`", neg, even_count);
}
output_table[#output_table + 1] = maybe.pair

return output_table