Zsolt Tasnadi
47e5e0ca17
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61 lines
2.0 KiB
Lua
61 lines
2.0 KiB
Lua
--- @section CodeGenerator
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CodeGenerator = {}
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local SALT = 27471
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local BASE36 = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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local NAME_LEN = 3
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-- Per-position offsets derived from SALT so each character slot
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-- maps to a different region of the 2-char base-36 space.
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local SALTS = {
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SALT % 36,
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math.floor(SALT / 36) % 36,
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math.floor(SALT / 1296) % 36,
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}
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--- Encodes a number (0–935) as exactly 2 base-36 characters.
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--- @within CodeGenerator
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function CodeGenerator.encode_pair(n)
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return BASE36:sub(math.floor(n / 36) + 1, math.floor(n / 36) + 1)
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.. BASE36:sub(n % 36 + 1, n % 36 + 1)
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end
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--- Decodes 2 base-36 characters back to a number.
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--- @within CodeGenerator
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function CodeGenerator.decode_pair(s)
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local d1 = BASE36:find(s:sub(1, 1), 1, true) - 1
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local d2 = BASE36:find(s:sub(2, 2), 1, true) - 1
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return d1 * 36 + d2
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end
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--- Encrypts a player name into a code twice its length.
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--- Each input character (A-Z, value 0-25) is encoded as
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--- c + SALTS[i] * 26, producing 2 base-36 output characters.
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--- @within CodeGenerator
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--- @param text string NAME_LEN-character uppercase player name.
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--- @return string Encrypted code (2 * NAME_LEN base-36 characters).
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function CodeGenerator.encrypt(text)
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local result = ""
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for i = 1, NAME_LEN do
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local c = math.max(0, (string.byte(text, i) or 65) - 65)
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result = result .. CodeGenerator.encode_pair(c + SALTS[i] * 26)
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end
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return result
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end
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--- Decrypts a personal code back to the original player name.
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--- @within CodeGenerator
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--- @param encrypted_text string The code to decrypt (2 * NAME_LEN chars).
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--- @return string Original player name, or "???" if the code is invalid.
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function CodeGenerator.decrypt(encrypted_text)
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local t = encrypted_text:upper()
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if #t ~= NAME_LEN * 2 then return "???" end
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local result = ""
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for i = 1, NAME_LEN do
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local pair = CodeGenerator.decode_pair(t:sub((i - 1) * 2 + 1, i * 2))
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result = result .. string.char(pair % 26 + 65)
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end
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return result
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end
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