Lua color library

color.lua

local lib_color = {}

-- Constants
lib_color.color_type = { TYPE_8 = 39710315, TYPE_256 = 34942623, TYPE_RGB = 29505187 }
local FOREGROUND = 1
local BACKGROUND = 2


local ESCAPE = "\x1b["
local RESET =  "\x1b[0m"

lib_color.modifiers = {
    BOLD =          "1",
    DIM =           "2",
    ITALIC =        "3",
    UNDERLINE =     "4",
    BLINKING =      "5",
    INVERSE =       "7",
    INVISIBLE =     "8",
    STRIKETHROUGH = "9"
}

lib_color.colors = {
    BLACK =   { "30", "40" },
    RED =     { "31", "41" },
    GREEN =   { "32", "42" },
    YELLOW =  { "33", "43" },
    BLUE =    { "34", "44" },
    MAGENTA = { "35", "45" },
    CYAN =    { "36", "46" },
    WHITE =   { "37", "47" },
    DEFAULT = { "39", "39" }
}

-- Utility functions
local function assert_conditionally(condition, value, error) if condition then assert(value, error) end end
local function checkIfExistsInTable(item, table, checkIdx, idx)
    checkIdx = checkIdx or false
    for _, member in pairs(table) do
        if checkIdx then 
            if item == member[idx] then 
                return true
            end
        else
            if item == member then 
                return true
            end
        end
    end
    return false
end
local function checkIndexesInTable(item, table) 
    for _, member in ipairs(item) do 
        if not checkIfExistsInTable(member, table) then return false end
    end
    return true
end
local function validateRGB(rgb) 
    if type(rgb) ~= "table" then return false end
    if #rgb < 3 then return false end
    for i = 1, 3 do 
        local n = tonumber(rgb[i])
        if (n == nil) or (not (n >= 0 and n <= 255)) then return false end
    end
    return true
end

-- Library functions
lib_color.format = function(color_type, modifiers, color, background, text) 
    -- Validate color_type and modifiers
    assert(checkIfExistsInTable(color_type, lib_color.color_type), "Argument 'color_type' must be one of: TYPE_8, TYPE_256 or TYPE_RGB.")    
    assert(type(modifiers) == "table", "Argument 'modifiers' must be a table.")
    assert(checkIndexesInTable(modifiers, lib_color.modifiers), "Argument 'modifiers' contains an invalid modifier.")
    
    -- Validate color and background
    assert_conditionally(color_type == lib_color.color_type.TYPE_RGB, validateRGB(color), "Argument 'color' must be a table with 3 numbers >= 0 and <= 255 when using RGB.")
    assert_conditionally((color_type == lib_color.color_type.TYPE_RGB) and background, validateRGB(background), "Argument 'background' must be a table with 3 numbers >= 0 and <= 255 when using RGB.")
    
    assert_conditionally(color_type == lib_color.color_type.TYPE_8, checkIfExistsInTable((type(color) == "table" and color or {})[FOREGROUND], lib_color.colors, true, FOREGROUND), "Argument 'color' must be a valid color when using 8 colors.")
    assert_conditionally((color_type == lib_color.color_type.TYPE_8) and background, checkIfExistsInTable((type(background) == "table" and background or {})[BACKGROUND], lib_color.colors, true, BACKGROUND), "Argument 'background' must be a valid color when using 8 colors.")
    
    assert_conditionally(color_type == lib_color.color_type.TYPE_256, tonumber(color) and (tonumber(color) >= 0 and tonumber(color) <= 255), "Argument 'color' must be a number >= 0 and <= 255 when using 256 colors.")
    assert_conditionally((color_type == lib_color.color_type.TYPE_256) and background, tonumber(background) and (tonumber(background) >= 0 and tonumber(background) <= 255), "Argument 'background' must be a number >= 0 and <= 255 when using 256 colors.")

    local fmttdString = ESCAPE
    local modifiersAlreadySeen = {}

    if color_type == lib_color.color_type.TYPE_8 then 
        for _, modifier in pairs(modifiers) do 
            if not checkIfExistsInTable(modifier, modifiersAlreadySeen) then
                fmttdString = fmttdString .. modifier .. ";"
                table.insert(modifiersAlreadySeen, modifier)
            end
        end
        if background then 
            fmttdString = string.format("%s%s;%sm%s%s", fmttdString, color[FOREGROUND], background[BACKGROUND], text, RESET)
        else
            fmttdString = string.format("%s%sm%s%s", fmttdString, color[FOREGROUND], text, RESET)
        end
    elseif color_type == lib_color.color_type.TYPE_256 then
        for _, modifier in pairs(modifiers) do 
            if not checkIfExistsInTable(modifier, modifiersAlreadySeen) then
                fmttdString = fmttdString .. modifier .. ";"
                table.insert(modifiersAlreadySeen, modifier)
            end
        end
        if background then 
            fmttdString = string.format("%s38;5;%s;48;5;%sm%s%s", fmttdString, tostring(color), tostring(background), text, RESET)
        else
            fmttdString = string.format("%s38;5;%sm%s%s", fmttdString, tostring(color), text, RESET)
        end
    else
        for _, modifier in pairs(modifiers) do 
            if not checkIfExistsInTable(modifier, modifiersAlreadySeen) then
                fmttdString = fmttdString .. modifier .. ";"
                table.insert(modifiersAlreadySeen, modifier)
            end
        end
        if background then 
            fmttdString = string.format("%s38;2;%s;48;2;%sm%s%s", fmttdString, table.concat(color, ";"), table.concat(background, ";"), text, RESET)
        else
            fmttdString = string.format("%s38;2;%sm%s%s", fmttdString, table.concat(color, ";"), text, RESET)
        end
    end

    return fmttdString
end

return lib_color