module S3SwfUpload
  module Signature
    $hexcase = false  # hex output format. false - lowercase; true - uppercase
    $b64pad  = '=' # base-64 pad character. "=" for strict RFC compliance
    $chrsz   = 8  # bits per input character. 8 - ASCII; 16 - Unicode

    def hex_sha1(s)
      binb2hex(core_sha1(str2binb(s), s.length * $chrsz))
    end

    def b64_hmac_sha1(key, data)
      binb2b64(core_hmac_sha1(key, data))
    end

    # Absolute barebones "unit" tests
    def assert(expr)
      fail 'Assertion failed' unless expr
    end

    def self_test
      num, cnt = [1_732_584_193, 5]

      assert(core_sha1(str2binb('abc'), 'abc'.length) == [-519_653_305, -1_566_383_753, -2_070_791_546, -753_729_183, -204_968_198])
      assert(rol(num, cnt) == -391_880_660)
      assert(safe_add(2_042_729_798, num) == -519_653_305)
      assert((num.js_shl(cnt)) == -391_880_672)
      assert((num.js_shr_zf(32 - cnt)) == 12)
      assert(sha1_ft(0, -271_733_879, -1_732_584_194, 271_733_878) == -1_732_584_194)
      assert(sha1_kt(0) == 1_518_500_249)
      assert(safe_add(safe_add(rol(num, cnt), sha1_ft(0, -271_733_879, -1_732_584_194, 271_733_878)), safe_add(safe_add(-1_009_589_776, 1_902_273_280), sha1_kt(0))) == 286_718_899)
      assert(str2binb('foo bar hey there') == [1_718_578_976, 1_650_553_376, 1_751_480_608, 1_952_998_770, 1_694_498_816])
      assert(hex_sha1('abc') == 'a9993e364706816aba3e25717850c26c9cd0d89d')
      assert(b64_hmac_sha1('foo', 'abc') == 'frFXMR9cNoJdsSPnjebZpBhUKzI=')
    end

    # Calculate the SHA-1 of an array of big-endian words, and a bit length
    def core_sha1(x, len)
      # append padding
      x[len >> 5] ||= 0
      x[len >> 5] |= 0x80 << (24 - len % 32)
      x[((len + 64 >> 9) << 4) + 15] = len

      w = Array.new(80, 0)
      a =  1_732_584_193
      b = -271_733_879
      c = -1_732_584_194
      d =  271_733_878
      e = -1_009_589_776

      # for(var i = 0; i < x.length; i += 16)
      i = 0
      while i < x.length
        olda = a
        oldb = b
        oldc = c
        oldd = d
        olde = e

        # for(var j = 0; j < 80; j++)
        j = 0
        while j < 80
          if j < 16
            w[j] = x[i + j] || 0
          else
            w[j] = rol(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1)
          end

          t = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)),
                       safe_add(safe_add(e, w[j]), sha1_kt(j)))
          e = d
          d = c
          c = rol(b, 30)
          b = a
          a = t
          j += 1
        end

        a = safe_add(a, olda)
        b = safe_add(b, oldb)
        c = safe_add(c, oldc)
        d = safe_add(d, oldd)
        e = safe_add(e, olde)
        i += 16
      end
      [a, b, c, d, e]
    end

    # Perform the appropriate triplet combination function for the current
    # iteration
    def sha1_ft(t, b, c, d)
      return (b & c) | ((~b) & d) if t < 20
      return b ^ c ^ d if t < 40
      return (b & c) | (b & d) | (c & d) if t < 60
      b ^ c ^ d
    end

    # Determine the appropriate additive constant for the current iteration
    def sha1_kt(t)
      if t < 20
        1_518_500_249
      elsif t < 40
        1_859_775_393
      elsif t < 60
        -1_894_007_588
      else
        -899_497_514
      end
    end

    # Calculate the HMAC-SHA1 of a key and some data
    def core_hmac_sha1(key, data)
      bkey = str2binb(key)
      bkey = core_sha1(bkey, key.length * $chrsz) if bkey.length > 16

      ipad = Array.new(16, 0)
      opad = Array.new(16, 0)
      # for(var i = 0; i < 16; i++)
      i = 0
      while i < 16
        ipad[i] = (bkey[i] || 0) ^ 0x36363636
        opad[i] = (bkey[i] || 0) ^ 0x5C5C5C5C
        i += 1
      end

      hash = core_sha1((ipad + str2binb(data)), 512 + data.length * $chrsz)
      core_sha1((opad + hash), 512 + 160)
    end

    # Add integers, wrapping at 2^32. This uses 16-bit operations internally
    # to work around bugs in some JS interpreters.
    def safe_add(x, y)
      v = (x + y) % (2**32)
      v > 2**31 ? v - 2**32 : v
    end

    # Bitwise rotate a 32-bit number to the left.
    def rol(num, cnt)
      # return (num << cnt) | (num >>> (32 - cnt))
      (num.js_shl(cnt)) | (num.js_shr_zf(32 - cnt))
    end

    # Convert an 8-bit or 16-bit string to an array of big-endian words
    # In 8-bit function, characters >255 have their hi-byte silently ignored.
    def str2binb(str)
      bin = []
      mask = (1 << $chrsz) - 1
      # for(var i = 0; i < str.length * $chrsz; i += $chrsz)
      i = 0
      while i < str.length * $chrsz
        bin[i >> 5] ||= 0
        bin[i >> 5] |= (str[i / $chrsz] & mask) << (32 - $chrsz - i % 32)
        i += $chrsz
      end
      bin
    end

    # Convert an array of big-endian words to a string
    #   function binb2str(bin)
    # {
    #   var str = "";
    #   var mask = (1 << $chrsz) - 1;
    #   for(var i = 0; i < bin.length * 32; i += $chrsz)
    #     str += String.fromCharCode((bin[i>>5] >>> (32 - $chrsz - i%32)) & mask);
    #   return str;
    # }
    #

    # Convert an array of big-endian words to a hex string.
    def binb2hex(binarray)
      hex_tab = $hexcase ? '0123456789ABCDEF' : '0123456789abcdef'
      str = ''
      # for(var i = 0; i < binarray.length * 4; i++)
      i = 0
      while i < binarray.length * 4
        str += hex_tab[(binarray[i >> 2] >> ((3 - i % 4) * 8 + 4)) & 0xF].chr +
               hex_tab[(binarray[i >> 2] >> ((3 - i % 4) * 8)) & 0xF].chr
        i += 1
      end
      str
    end

    # Convert an array of big-endian words to a base-64 string
    def binb2b64(binarray)
      tab = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
      str = ''

      # for(var i = 0; i < binarray.length * 4; i += 3)
      i = 0
      while i < binarray.length * 4
        triplet = (((binarray[i >> 2].to_i >> 8 * (3 - i % 4)) & 0xFF) << 16) |
                     (((binarray[i + 1 >> 2].to_i >> 8 * (3 - (i + 1) % 4)) & 0xFF) << 8) |
                      ((binarray[i + 2 >> 2].to_i >> 8 * (3 - (i + 2) % 4)) & 0xFF)
        # for(var j = 0; j < 4; j++)
        j = 0
        while j < 4
          if i * 8 + j * 6 > binarray.length * 32
            str += $b64pad
          else
            str += tab[(triplet >> 6 * (3 - j)) & 0x3F].chr
          end
          j += 1
        end
        i += 3
      end
      str
    end
  end
end

class Integer
  # 32-bit left shift
  def js_shl(count)
    v = (self << count) & 0xffffffff
    v > 2**31 ? v - 2**32 : v
  end

  # 32-bit zero-fill right shift  (>>>)
  def js_shr_zf(count)
    self >> count & (2**(32 - count) - 1)
  end
end