ergonomic_seed.lua

local ErgonomicSeed = {
    -- default pool of adjectives
    adjectives = {
        'abdominal', 'beneficial', 'carping', 'Dejected', 'Elusive', 'Feisty', 'Gnomonic', 'Handsome', 'Illicit', 'Jokeless',
        'Knightly', 'Legless', 'Macho', 'Nebulous', 'oozy', 'peachy', 'quaint', 'radical', 'seedy', 'thievish', 'uneasy',
        'vague', 'wacky', 'xerophagous', 'yummy', 'zippy'
    },
    -- default pool of nouns
    nouns = {
        'aardvark', 'boubou', 'caterpillar', 'dowitcher', 'elephant', 'finwhale', 'gazelle', 'hippopotamus', 'isopod',
        'jellyfish', 'kestrel', 'ladybug', 'mantid', 'narwhale', 'orca', 'pheasant', 'quetzal', 'raptor', 'scorpion',
        'tortoise', 'unicorn', 'vulture', 'wasp', 'xenopus', 'yeti', 'zebu'
    },
    -- default format of adjectives and nouns
    format = 'lower',
    -- default delimiter between adjectives and nouns
    delimiter = '-',
    -- default length of seed
    length = 3,
    -- ensure unique seed due to second granularity of os time
    _seed_offset = 0,
    -- current version of library
    _version = '1.0.0'
}

local formats = {
    lower = function(str) return string.lower(str) end,
    upper = function(str) return string.upper(str) end,
    capitalize = function(str) return (str:gsub('^%l', string.upper)) end
}

-- djb2 hash function
local function djb2(str)
    local hash = 5381
    for i = 1, #str do hash = ((hash << 5) + hash) + str:byte(i) end
    return hash
end

local function randomseed(seed, seed_offset)
    math.randomseed(seed or (os.time() + seed_offset))
    return seed_offset + 1
end

local function generator(length, adjectives, nouns)
    local values = {}
    for i = 1, length - 1 do table.insert(values, adjectives[math.random(#adjectives)]) end
    table.insert(values, nouns[math.random(#nouns)])
    return values;
end

local function formatter(values, format)
    for key, value in pairs(values) do values[key] = (formats[format] or formats.lower)(value) end
    return values
end

-- Generates a random and reasonably unique human readable id along with
-- its corresponding hash value
-- @param options option table
-- @param options.seed initial number used in pseudo-random generator
-- @param options.format word format in the set {lower, upper, capitalize}
-- @param options.delimiter delimiter between words
-- @param options.length number of words to generate
-- @param options.adjectives table of adjectives
-- @param options.nouns table of nouns
function ErgonomicSeed:generate(options)
    options = options or {}
    self._seed_offset = randomseed(options.seed, self._seed_offset)
    local result = table.concat(formatter(generator(options.length or self.length, options.adjectives or self.adjectives,
                                                    options.nouns or self.nouns), options.format or self.format),
                                options.delimiter or self.delimiter)
    return result, djb2(result)
end

return ErgonomicSeed