// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: MIT

/*!
 * \brief The StackView is a component that can be used to simulate a stack view.
 *
 * \note: Due to the language limitation only the partial implementation is possible.
 *        The component is meant to be a helper.
 *
 * \par Usage:
 * The component can be used in two ways:
 * - for smaller pages, where all pages are loaded at once,
 * - for more complex pages, where pages are loaded dynamically.
 *
 * Static pages:
 * \code{*.slint}
 * stack := StackView {
 *   current-index: 0;
 *   min-index: 0;
 *
 *   for color in [ Colors.red, Colors.green, Colors.blue ]:
 *     StackPage {
 *       is-current: self.check-is-current(stack.current-index);
 *       init => { self.page-index = stack.insert-page(); } // StackPage.count increased with insert-page function
 *
 *       TestPage {
 *         background: color;
 *         push => { stack.push(); }
 *         pop => { stack.pop(); }
 *       }
 *     }
 * }
 * \endcode
 *
 * Dynamic pages:
 * \code{*.slint}
 * stack := StackView {
 *   count: 2;  // StackPage.count provided manually
 *   current-index: 0;
 *   min-index: 0;
 *
 *   if (stack.current-index == 0): StackPage {
 *       page-index: 0; is-current: true;
 *
 *       TestPage {
 *         background: Colors.red;
 *         push => { stack.push(); }
 *         pop => { stack.pop(); }
 *       }
 *     }
 *   if (stack.current-index == 1): StackPage {
 *       page-index: 1; is-current: true;
 *
 *       TestPage {
 *         background: Colors.green;
 *         push => { stack.push(); }
 *         pop => { stack.pop(); }
 *       }
 *     }
 * }
 * \endcode
 *
 * \sa StackPage
 */
export component StackView inherits Rectangle {
    /// \brief This property states the number of items in the stack
    in-out property<int> count: 0;

    /// \brief This property states the index of the currently visible item
    in-out property<int> current-index: -1;

    /// \brief This property configures the minimum index the pop function can set (-1 by default)
    in property<int> min-index: -1;

    /// \brief This property configures the minimum index the push function can set (#count -1 by default)
    in property<int> max-index: self.count - 1;

    /// \brief This function increases the pages #count by one and returns new page index
    public function insert-page() -> int {
        self.count += 1;
        return  self.count - 1;
    }

    /// \brief This function increases the #current-index if possible
    public function push() {
        if (self.current-index < Math.min(self.max-index, self.count - 1)) {
            self.current-index += 1;
        }
    }

    /// \brief This function decreased the #current-index if possible
    public function pop() {
        if (self.current-index > Math.max(self.min-index, -1)) {
            self.current-index -= 1;
        }
    }
}

/*!
 * \brief The StackPage is a component to use in the StackView.
 *
 * The real content can either derive from the StackPage (which is Rectangle based) or can be contained
 * as the page children.
 *
 * Inherits:
 * \code{*.slint}
 * export TestPage inherits StackPage {
 *   background: color;
 * }
 * \endcode
 *
 * Contains:
 * \code{*.slint}
 * StackPage {
 *   TestPage {
 *     background: Colors.red;
 *   }
 * }
 * \endcode
 *
 * \sa StackView
 */
export component StackPage inherits TouchArea {
    /// \brief This property configures the page index
    in property<int> page-index: -1;

    /// \brief This property configures whether the page is a current page (if not, it is hidden)
    in property<bool> is-current: false;

    /// \brief This function is a helper function to use when setting the #is-current property
    public pure function check-is-current(current-index: int) -> bool {
        return current-index == self.page-index;
    }

    visible: self.is-current;
}