--[[
Name: LibBase64-1.0
Author(s): ckknight (ckknight@gmail.com)
Website: http://www.wowace.com/projects/libbase64-1-0/
Description: A library to encode and decode Base64 strings
License: MIT
]]

local MAJOR, MINOR = 'LibBase64-1.0_GW2', 2
local LibBase64 = LibStub:NewLibrary(MAJOR, MINOR)
if not LibBase64 then return end

local _chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
local byteToNum, numToChar = {}, {}
for i = 1, #_chars do
    numToChar[i - 1] = strsub(_chars, i, i)
    byteToNum[strbyte(_chars, i)] = i - 1
end

local t = {}
local equals_byte = strbyte("=")
local whitespace = {
    [strbyte(" ")] = true,
    [strbyte("\t")] = true,
    [strbyte("\n")] = true,
    [strbyte("\r")] = true,
}

--- Encode a normal bytestring into a Base64-encoded string
-- @param text a bytestring, can be binary data
-- @param maxLineLength This should be a multiple of 4, greater than 0 or nil. If non-nil, it will break up the output into lines no longer than the given number of characters. 76 is recommended.
-- @param lineEnding a string to end each line with. This is "\r\n" by default.
-- @usage LibBase64.Encode("Hello, how are you doing today?") == "SGVsbG8sIGhvdyBhcmUgeW91IGRvaW5nIHRvZGF5Pw=="
-- @return a Base64-encoded string
function LibBase64:Encode(text, maxLineLength, lineEnding)
    if type(text) ~= "string" then
        error(format("Bad argument #1 to `Encode'. Expected string, got %q", type(text)), 2)
    end

    if maxLineLength then
        if type(maxLineLength) ~= "number" then
            error(format("Bad argument #2 to `Encode'. Expected number or nil, got %q", type(maxLineLength)), 2)
        elseif (maxLineLength % 4) ~= 0 then
            error(format("Bad argument #2 to `Encode'. Expected a multiple of 4, got %s", maxLineLength), 2)
        elseif maxLineLength <= 0 then
            error(format("Bad argument #2 to `Encode'. Expected a number > 0, got %s", maxLineLength), 2)
        end
    end

    if lineEnding == nil then
        lineEnding = "\r\n"
    elseif type(lineEnding) ~= "string" then
        error(format("Bad argument #3 to `Encode'. Expected string, got %q", type(lineEnding)), 2)
    end

    local currentLength = 0
    for i = 1, #text, 3 do
        local a, b, c = strbyte(text, i, i+2)
        local nilNum = 0
        if not b then
            nilNum, b, c = 2, 0, 0
        elseif not c then
            nilNum, c = 1, 0
        end

        local num = a * 2^16 + b * 2^8 + c
        local d = num % 2^6;num = (num - d) / 2^6
        c = num % 2^6;num = (num - c) / 2^6
        b = num % 2^6;num = (num - b) / 2^6
        a = num % 2^6

        t[#t+1] = numToChar[a]
        t[#t+1] = numToChar[b]
        t[#t+1] = (nilNum >= 2) and "=" or numToChar[c]
        t[#t+1] = (nilNum >= 1) and "=" or numToChar[d]

        currentLength = currentLength + 4
        if maxLineLength and (currentLength % maxLineLength) == 0 then
            t[#t+1] = lineEnding
        end
    end

    local s = table.concat(t)
    wipe(t)

    return s
end

local t2 = {}

--- Decode a Base64-encoded string into a bytestring
-- this will raise an error if the data passed in is not a Base64-encoded string
-- this will ignore whitespace, but not invalid characters
-- @param text a Base64-encoded string
-- @usage LibBase64.Encode("SGVsbG8sIGhvdyBhcmUgeW91IGRvaW5nIHRvZGF5Pw==") == "Hello, how are you doing today?"
-- @return a bytestring
function LibBase64:Decode(text)
    if type(text) ~= "string" then
        error(format("Bad argument #1 to `Decode'. Expected string, got %q", type(text)), 2)
    end

    for i = 1, #text do
        local byte = strbyte(text, i)
        if not (whitespace[byte] or byte == equals_byte) then
            local num = byteToNum[byte]
            if not num then
                wipe(t2)

                error(format("Bad argument #1 to `Decode'. Received an invalid char: %q", strsub(text, i, i)), 2)
            end

            t2[#t2+1] = num
        end
    end

    for i = 1, #t2, 4 do
        local a, b, c, d = t2[i], t2[i+1], t2[i+2], t2[i+3]
        local nilNum = 0
        if not c then
            nilNum, c, d = 2, 0, 0
        elseif not d then
            nilNum, d = 1, 0
        end

        local num = a * 2^18 + b * 2^12 + c * 2^6 + d
        c = num % 2^8;num = (num - c) / 2^8
        b = num % 2^8;num = (num - b) / 2^8
        a = num % 2^8

        t[#t+1] = strchar(a)
        if nilNum < 2 then t[#t+1] = strchar(b) end
        if nilNum < 1 then t[#t+1] = strchar(c) end
    end

    wipe(t2)

    local s = table.concat(t)
    wipe(t)

    return s
end

function LibBase64:IsBase64(text)
    if type(text) ~= "string" then
        error(format("Bad argument #1 to `IsBase64'. Expected string, got %q", type(text)), 2)
    end

    if #text % 4 ~= 0 then
        return false
    end

    for i = 1, #text do
        local byte = strbyte(text, i)
        if not (whitespace[byte] or byte == equals_byte) then
            local num = byteToNum[byte]
            if not num then
                return false
            end
        end
    end

    return true
end
