local DEFAULT_UPATH = 'https://raw.githubusercontent.com/kepler155c/opus/develop/sys/apis'
local PASTEBIN_URL  = 'http://pastebin.com/raw'
local GIT_URL       = 'https://raw.githubusercontent.com'

-- fix broken http get
local syncLocks = { }

local function sync(obj, fn)
  local key = tostring(obj)
  if syncLocks[key] then
    local cos = tostring(coroutine.running())
    table.insert(syncLocks[key], cos)
    repeat
      local _, co = os.pullEvent('sync_lock')
    until co == cos
  else
    syncLocks[key] = { }
  end
  local s, m = pcall(fn)
  local co = table.remove(syncLocks[key], 1)
  if co then
    os.queueEvent('sync_lock', co)
  else
    syncLocks[key] = nil
  end
  if not s then
    error(m)
  end
end

local function loadUrl(url)
  local c
  sync(url, function()
    local h = http.get(url)
    if h then
      c = h.readAll()
      h.close()
    end
  end)
  if c and #c > 0 then
    return c
  end
end

local function requireWrapper(env)

  local function standardSearcher(modname, env, shell)
    if package.loaded[modname] then
      return function()
        return package.loaded[modname]
      end
    end
  end

  local function shellSearcher(modname, env, shell)
    local fname = modname:gsub('%.', '/') .. '.lua'

    if shell and type(shell.dir) == 'function' then
      local path = shell.resolve(fname)
      if fs.exists(path) and not fs.isDir(path) then
        return loadfile(path, env)
      end
    end
  end

  local function pathSearcher(modname, env, shell)
    local fname = modname:gsub('%.', '/') .. '.lua'

    for dir in string.gmatch(package.path, "[^:]+") do
      local path = fs.combine(dir, fname)
      if fs.exists(path) and not fs.isDir(path) then
        return loadfile(path, env)
      end
    end
  end

  -- require('BniCQPVf')
  local function pastebinSearcher(modname, env, shell)
    if #modname == 8 and not modname:match('%W') then
      local url = PASTEBIN_URL .. '/' .. modname
      local c = loadUrl(url)
      if c then
        return load(c, modname, nil, env)
      end
    end
  end

  -- require('kepler155c.opus.master.sys.apis.util')
  local function gitSearcher(modname, env, shell)
    local fname = modname:gsub('%.', '/') .. '.lua'
    local _, count = fname:gsub("/", "")
    if count >= 3 then
      local url = GIT_URL .. '/' .. fname
      local c = loadUrl(url)
      if c then
        return load(c, modname, nil, env)
      end
    end
  end

  local function urlSearcher(modname, env, shell)
    local fname = modname:gsub('%.', '/') .. '.lua'

    if fname:sub(1, 1) ~= '/' then
      for entry in string.gmatch(package.upath, "[^;]+") do
        local url = entry .. '/' .. fname
        local c = loadUrl(url)
        if c then
          return load(c, modname, nil, env)
        end
      end
    end
  end

  -- place package and require function into env
  package = {
    path = LUA_PATH or 'sys/apis',
    upath = LUA_UPATH or DEFAULT_UPATH,
    config = '/\n:\n?\n!\n-',
    loaded = {
      math   = math,
      string = string,
      table  = table,
      io     = io,
      os     = os,
    },
    loaders = {
      standardSearcher,
      shellSearcher,
      pathSearcher,
      pastebinSearcher,
      gitSearcher,
      urlSearcher,
    }
  }

  function require(modname)

    for _,searcher in ipairs(package.loaders) do
      local fn, msg = searcher(modname, env, shell)
      if fn then
        local module, msg = fn(modname, env)
        if not module then
          error(msg or (modname .. ' module returned nil'), 2)
        end
        package.loaded[modname] = module
        return module
      end
      if msg then
        error(msg, 2)
      end
    end
    error('Unable to find module ' .. modname)
  end

  return require -- backwards compatible
end

return function(env)
  setfenv(requireWrapper, env)
  return requireWrapper(env)
end