#!/usr/bin/lua

local lgi = require('lgi')
local player = lgi.Playerctl.Player{}

-- penlight func, temporary.
function assert_arg (n,val,tp,verify,msg,lev)
    if type(val) ~= tp then
        error(("argument %d expected a '%s', got a '%s'"):format(n,tp,type(val)),lev or 2)
    end
    if verify and not verify(val) then
        error(("argument %d: '%s' %s"):format(n,val,msg),lev or 2)
    end
    return val
end

-- penlight func
local function assert_string (n,s)
    assert_arg(n,s,'string')
end

-- decode uri to standard unix path
local decodeURI
do
    local char, gsub, tonumber = string.char, string.gsub, tonumber
    local function _(hex) return char(tonumber(hex, 16)) end

    function decodeURI(s)
        s = gsub(s, '%%(%x%x)', _)
        s = gsub(s, 'file://', '')
        return s
    end
end

-- check if file is available, if not return
local raw_path = player:print_metadata_prop('xesam:url')
if raw_path == nil then
    return
else
    path = decodeURI(raw_path)
end

-- capture system cmd
function os.capture(cmd)
    local f = io.popen(cmd, 'r')
    local s = f:read()
    f:close()
    return s
end

-- get bitrate
function string_to_decode(str)
    local cmd = ('mediainfo --inform="Audio;%BitRate/String%" "' ..path.. '" ')
    local buf = os.capture(cmd)
    return buf
end

-- when albumarArtist is a list, filter all but first artist
local raw_albumArtist = player:print_metadata_prop('xesam:albumArtist')
function format_artist()
    for word in string.gmatch(raw_albumArtist, '([^,;]+)') do
       return word
    end
end

-- fetch metadata via playerctl lib
local title = player:get_title()
local albumartist = format_artist()
local album = player:get_album()
-- get bitrate from mediainfo
local bitrate = string_to_decode(str)

-- concat metadata values into a single string
function listvalues(s)
    local t = { }
    for k,v in ipairs(s) do
        t[#t+1] = tostring(v)
    end
    return table.concat(t,"  /  ")
end


-- calculate at what length to truncate
local total_length = utf8.len(title) +utf8.len(albumartist) +utf8.len(album) +utf8.len(bitrate)
local chars = total_length - 75

local max_title = math.floor( utf8.len(title) - chars )
local max_albumartist = math.floor( utf8.len(albumartist) - chars )
local max_album = math.floor( utf8.len(album) - chars )

function shorten(s,w)
    local ellipsis = "…"
    local n_ellipsis = utf8.len(ellipsis)
    assert_string(1,s)
    if utf8.len(s) > w then
        return s:sub(1,w-n_ellipsis) .. ellipsis
    end
    return s
end

-- only truncate the longest string...
-- figure out a better way to determine the longset variable.
if utf8.len(title) >= utf8.len(albumartist) and utf8.len(title) >= utf8.len(album) then
    metadata = { shorten(title, max_title), albumartist, album, bitrate }
elseif utf8.len(albumartist) >= utf8.len(title) and utf8.len(albumartist) >= utf8.len(album) then
    metadata = { title, shorten(albumartist, max_albumartist), album, bitrate }
elseif utf8.len(album) >= utf8.len(title) and utf8.len(album) >= utf8.len(albumartist) then
    metadata = { title, albumartist, shorten(album, max_album), bitrate }
end

print(listvalues(metadata))