-- Copyright (C) 2015 Tomoyuki Fujimori <moyu@dromozoa.com>
--
-- This file is part of dromozoa-commons.
--
-- dromozoa-commons is free software: you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation, either version 3 of the License, or
-- (at your option) any later version.
--
-- dromozoa-commons is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with dromozoa-commons.  If not, see <http://www.gnu.org/licenses/>.

local lua_version_num = require "dromozoa.commons.lua_version_num"

local function byte(v, endian)
  local b = v % 0x100
  local a = (v - b) / 0x100
  if endian == ">" then
    return a, b
  else
    return b, a
  end
end

local function char(v, endian)
  return string.char(byte(v, endian))
end

local function read(handle, n, endian)
  if n == nil or n == 1 then
    local a, b = handle:read(2):byte(1, 2)
    if endian == ">" then
      return a * 0x100 + b
    else
      return b * 0x100 + a
    end
  else
    local a, b, c, d = handle:read(4):byte(1, 4)
    local u
    local v
    if endian == ">" then
      u = a * 0x100 + b
      v = c * 0x100 + d
    else
      u = b * 0x100 + a
      v = d * 0x100 + c
    end
    if n == 2 then
      return u, v
    else
      return u, v, read(handle, n - 2, endian)
    end
  end
end

if lua_version_num >= 503 then
  local function read(handle, n, endian)
    if n == nil or n == 1 then
      if endian == ">" then
        return ((">I2"):unpack(handle:read(2)))
      else
        return (("<I2"):unpack(handle:read(2)))
      end
    else
      local u
      local v
      if endian == ">" then
        u, v = (">I2I2"):unpack(handle:read(4))
      else
        u, v = ("<I2I2"):unpack(handle:read(4))
      end
      if n == 2 then
        return u, v
      else
        return u, v, read(handle, n - 2, endian)
      end
    end
  end

  return {
    byte = function (v, endian)
      if endian == ">" then
        local a, b = ("BB"):unpack((">I2"):pack(v))
        return a, b
      else
        local a, b = ("BB"):unpack(("<I2"):pack(v))
        return a, b
      end
    end;
    char = function (v, endian)
      if endian == ">" then
        return (">I2"):pack(v)
      else
        return ("<I2"):pack(v)
      end
    end;
    read = read;
  }
else
  return {
    byte = byte;
    char = char;
    read = read;
  }
end