YangOs

--define SYSTEM SETTINGS
local osWork = true
local osTargetFrames = 24
local osScrW,osScrH = 51, 19
local osBackground = colors.blue
--end SYSTEM SETTINGS



--define OS_SHADOW_FUNCTIONS
local function osShadow(sx, sy, sw, sh)
   return {
        x = sx,
        y = sy,
        width = sw,
        height = sh
   }
end
local function osShadowFromRect(r)
   return osShadow(r.x,r.y,r.width,r.height)
end
local function osShadowFromWindow(w)
    return osShadowFromRect(w.window_rect)
end
local function osShadowDraw(s)
    for yoffset = 0, s.height-1 do
        term.setCursorPos(s.x, s.y + yoffset)
        term.write( (' '):rep(s.width))
    end
end
--end OS_SHADOW_FUNCTIONS



--define OS_SHADOWS_FUNCTIONS
local function osShadowsFromRects(rs)
  local ss = {}
  for i,r in ipairs(rs) do
      ss[i]=osShadowFromRect(r)
  end
  return ss
end
local function osShadowsFromWindows(ws)
    local ss = {}
    for i,w in ipairs(ws) do
      ss[i]=osShadowFromWindow(w)
    end
    return ss
end
local function osShadowsDraw(ss)
    term.setBackgroundColor(osBackground)
    for _,s in ipairs(ss) do
        osShadowDraw(s)
    end
end
--end OS_SHADOWS_FUNCTIONS



--define OS_RECT_FUNCTIONS
local function osRect(rx, ry, rw, rh, ri, rc, rt, rtc)
    return {
        x = rx,
        y = ry,
        width = rw,
        height = rh,
        index = ri,
        color = rc,
        text = rt,
        text_color = rtc
    }
end
local function osRectCopy(r)
    return osRect(r.x,r.y,r.width,r.height,r.index,r.color,r.text,r.text_color)
end
local function osRectDraw(r)
    if r.text_color then
        term.setTextColor(r.text_color)
    end
    term.setBackgroundColor(r.color)
    local textoffset = 0
    for yoffset = 0, r.height-1 do
        term.setCursorPos(r.x, r.y + yoffset)
        if r.text then
            local soffset = yoffset*r.width
            local start, ends = 1+soffset+textoffset,r.width+soffset+textoffset
            local s = r.text:sub(start, ends)
            local nline = s:find('\n')
            local cnext = r.text:sub(ends+1,ends+1)
            if nline then
                s = s:sub(1,nline-1)..(' '):rep(r.width-nline+1)
                textoffset = textoffset - r.width + nline
            elseif cnext == '\n' then
                textoffset = textoffset + 1
            else
                local i = s:reverse():find(' ')
                if i and (cnext~='' and cnext~=' ' and cnext~='\n') then
                    textoffset = textoffset - i + 1
                    s = s:sub(1,-i)
                end
                if #s<r.width then s = s..(' '):rep(r.width-#s) end
            end
            term.write(s)
        else
            term.write( (' '):rep(r.width))
        end
    end
end
--end OS_RECT_FUNCTIONS



--define OS_RECTS_FUNCTIONS
local function osRectsCopy(rs)
    local copy = {}
    for i,r in ipairs(rs) do
        copy[i]=osRectCopy(r)
    end
    return copy
end
local function osRectsDraw(rs)
    local copy = osRectsCopy(rs)
    table.sort(copy, function(r1, r2)return r1.index >= r2.index end)
    for _,r in ipairs(copy) do
        osRectDraw(r)
    end
end
--end OS_RECTS_FUNCTIONS



--define OS_LOCAL_RECT_FUNCTIONS
local function osLocalRectDraw(lr, x0, y0)
    local copy = osRectCopy(lr)
    copy.x = copy.x+x0
    copy.y = copy.y+y0
    osRectDraw(copy)
end
--end OS_LOCAL_RECT_FUNCTIONS



--define OS_LOCAL_RECTS_FUNCTIONS
local function osLocalRectsDraw(lrs, x0, y0)
    for _,lr in ipairs(lrs) do
        osLocalRectDraw(lr, x0, y0)
    end
end
--end OS_LOCAL_RECTS_FUNCTIONS



--define OS_WINDOW_FUNCTIONS
local function osWindow(wr, wlrs)
    return {
        window_rect = wr,
        lrects = wlrs
    }
end
local function osWindowCopy(w)
    return osWindow(osRectCopy(w.window_rect), osRectsCopy(w.lrects))
end
local function osWindowDraw(w)
    local wr = w.window_rect
    osRectDraw(wr)
    osLocalRectsDraw(w.lrects, wr.x,wr.y)
end
--end OS_WINDOW_FUNCTIONS



--define OS_WINDOWS_FUNCTIONS
local function osWindowsCopy(ws)
    local copy = {}
    for i,w in pairs(ws) do
        copy[i] = osWindowCopy(w)
    end
    return copy
end
local function osWindowsDraw(ws)
    local copy = osWindowsCopy(ws)
    table.sort(copy, function(w1, w2)return w1.window_rect.index >= w2.window_rect.index end)
    for _,w in pairs(copy) do
        osWindowDraw(w)
    end
end
--end OS_WINDOWS_FUNCTIONS


--osRect rx, ry, rw, rh, ri, rc, rt, rtc
--define OS_FUNCTIONS
local osShadows = {}
local osWindows = {
    osWindow(
        osRect(10,1,20,10,1,colors.red,"Hello",colors.white),
        {osRect(1,5,5,5,1,colors.white,"Blue",colors.blue)}
    )
}

local function osMouseControl(x,y,event)
    for _,w in ipairs(osWindows) do
        local r = w.window_rect
        if r.index==1 then
            if event == "click" then
                r.x = x
                r.y = y
            elseif event=="drag" then
                r.width = math.abs(r.x-x)+1
                r.height = math.abs(r.y-y)+1
            end
        end
    end
end
local function osMouseClick()
    while osWork do
        local e,b,x,y=os.pullEvent('mouse_click')
        osMouseControl(x,y,"click")
    end
end
local function osMouseDrag()
   while osWork do
        local e,b,x,y=os.pullEvent('mouse_drag')
        osMouseControl(x,y,"drag")
   end
end
local function osMain()
    osRectDraw(osRect(1,1,osScrW,osScrH,0,osBackground))
    while osWork do
        sleep(1/osTargetFrames)
        osShadowsDraw(osShadows)
        osWindowsDraw(osWindows)
        osShadows = osShadowsFromWindows(osWindows)
    end
end
--end OS_FUNCTIONS



parallel.waitForAll(osMain,osMouseClick, osMouseDrag)