Fake Shell

function FakeShell()
    local shell = {}
    shell.__cdir = ""
    shell.__path = ".:/rom/programs:/rom/programs/advanced:/rom/programs/rednet:/rom/programs/fun:/rom/programs/http:/rom/programs/fun/advanced"
    shell.__stack = {}

    shell.dir = function()
        return shell.__cdir
    end

    shell.setDir = function(path)
        shell.__cdir = path
    end

    shell.resolve = function(localPath)
        return fs.combine(shell.__cdir, localPath)
    end

    shell.resolveProgram = function(name)
        local firstChar = name:sub(1, 1)
        if firstChar == "/" or firstChar == "\\" then
            local path = fs.combine("", name)
            if fs.exists(path) and not fs.isDir(path) then return path end
            return nil
        end

        for path in shell.__path:gmatch("[^:]+") do
            path = fs.combine(shell.resolve(path), name)
            if fs.exists(path) and not fs.isDir(path) then return path end
        end

        return nil
    end

    shell.getRunningProgram = function()
        return shell.__stack[#shell.__stack]
    end

    shell.run = function(program, ...)
        local path = shell.resolveProgram(program)
        table.insert(shell.__stack, path)
        os.run({ shell = shell }, path, ...)
    end

    shell.path = function()
        return shell.__path
    end

    shell.setPath = function(path)
        shell.__path = path
    end

    return shell
end