Module:Hashtitle

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--[[
This module was created with the help of ChatGPT v4.
It generated a deterministic short hash for a page title,
with the purpose of being used in an Etherpad URL such as:
https://etherpad.wikimedia.org/p/{{hash}}
To implement this function and generate the etherpad URL,
simply add the following code:
[https://etherpad.wikimedia.org/p/{{#invoke:Hashtitle|hashTitle}} Etherpad]
The Module was developed for WikiIndaba 2023 held in Agadir Morocco.
]]
local p = {}

-- Bitwise XOR
function bxor(a, b)
    local result = 0
    local bitval = 1
    while a > 0 or b > 0 do
        local abit = a % 2
        local bbit = b % 2
        if abit ~= bbit then
            result = result + bitval
        end
        a = math.floor(a / 2)
        b = math.floor(b / 2)
        bitval = bitval * 2
    end
    return result
end

-- Bitwise AND
function band(a, b)
    local result = 0
    local bitval = 1
    while a > 0 and b > 0 do
        if (a % 2 == 1) and (b % 2 == 1) then
            result = result + bitval
        end
        a = math.floor(a / 2)
        b = math.floor(b / 2)
        bitval = bitval * 2
    end
    return result
end

-- FNV-1a hash function
function fnv_1a(str)
    local FNV_prime = 0x01000193
    local FNV_offset_basis = 0x811C9DC5

    local hash = FNV_offset_basis
    for i = 1, #str do
        hash = bxor(hash, str:byte(i))
        hash = band(hash * FNV_prime, 0xFFFFFFFF)
    end
    return hash
end

-- Function to convert a title to a unique hash
function p.hashTitle(frame)
    local title = mw.title.getCurrentTitle().text
    local hash = fnv_1a(title)
    return string.format("%X", hash)
end

return p