import datatypes

struct Fluid[T] {
mut:
    elements  datatypes.Queue[T]
    switch    bool // 0 by default
    selements datatypes.Stack[T]
}

fn (mut fluid Fluid[T]) push(item T) {
    if fluid.switch {
        fluid.selements.push(item)
    } else {
        fluid.elements.push(item)
    }
}

fn (mut fluid Fluid[T]) pop() !T {
    if fluid.switch {
        return fluid.selements.pop()!
    } else {
        return fluid.elements.pop()!
    }
}

fn (fluid Fluid[T]) str() string {
    if fluid.switch {
        return fluid.selements.str()
    } else {
        return fluid.elements.str()
    }
}

fn (fluid Fluid[T]) peek() !T {
    if fluid.switch {
        return fluid.selements.peek()!
    } else {
        return fluid.elements.peek()!
    }
}

// this function converts queue to stack
fn (mut fluid Fluid[T]) to_stack() !bool {
    if !fluid.switch {
        // convert queue to stack
        for i in 1 .. fluid.elements.len() + 1 {
            fluid.selements.push(fluid.elements.index(fluid.elements.len() - i)!)
        }
        fluid.switch = true
    }
    return true
}

fn test_array_init_with_fields() {
    mut arr := []Fluid[string]{len: 10}
    for i in 0 .. arr.len {
        // add str to queue
        arr[i].push('${10 + i}')
    }
    println(arr)
    ret := arr[1].to_stack()!
    assert ret
}