@RequiredArgsConstructor
public class StringFolderGui extends BaseGui{

    private final String title;

    private final int[] inventoryMap;
    private final VisualLink[] links;


    @Override
    public void onClick(InventoryClickEvent event) {
        final int clickedId = inventoryMap[event.getSlot()];
        if(clickedId >= 0)
            links[clickedId].link.run((Player) event.getWhoClicked());
    }

    @Override
    protected Inventory render() {
        Inventory inv = Bukkit.createInventory(null, inventoryMap.length);
        ItemStack[] contents = inv.getContents();

        for(int i = 0; i < inventoryMap.length; i++) {
            final int itemId = inventoryMap[i];
            if(itemId < 0)
                continue;
            contents[i] = links[itemId].item;
        }

        inv.setContents(contents);
        return inv;
    }

    @Data
    public static class VisualLink {
        public final Link link;
        public final ItemStack item;

        public static VisualLink of(Link link, ItemStack item) {
            return new VisualLink(link, item);
        }
    }

    public static Builder builder() {
        return new Builder();
    }


    public static class Builder {
        private String title = "Gui";
        private String map = "";
        private Map<Character, VisualLink> links = new HashMap<>();

        public Builder title(@NonNull String title) {
            this.title = title;
            return this;
        }

        public Builder map(@NonNull String map) {
            if(!isValid(map.length()))
                throw new IllegalArgumentException("Invalid map length: " + map.length());
            this.map = map;
            return this;
        }

        private boolean isValid(int length) {
            return length % 9 == 0 && length > 0 && length <= GuiSize.DOUBLE.size();
        }

        public Builder addLink(char c, VisualLink link) {
            links.put(c, link);
            return this;
        }

        public Builder addLink(char c, Link link, ItemStack item) {
            links.put(c, VisualLink.of(link, item));
            return this;
        }

        public Builder addLink(char c, Link link, Material display, String name, String... lores) {
            links.put(c, VisualLink.of(link, GuiUtils.itemStack(display, name, lores)));
            return this;
        }

        public StringFolderGui build() {
            VisualLink[] clinks = new VisualLink[links.size()];
            char[] linksbychar = new char[links.size()];
            {//compile clinks and linksbychar
                int index = 0;

                for (Map.Entry<Character, VisualLink> e : links.entrySet()) {
                    clinks[index] = e.getValue();
                    linksbychar[index] = e.getKey();
                    index++;
                }
            }

            int[] cmap = new int[map.length()];
            {//compile cmap
                for (int index = 0; index < cmap.length; index++) {
                    final char c = map.charAt(index);
                    int id = -1;
                    for (int i = 0; i < clinks.length; i++) {
                        if (linksbychar[i] == c) {
                            id = i;
                            break;
                        }
                    }
                    cmap[index] = id;
                }
            }

            return new StringFolderGui(title, cmap, clinks);
        }
    }
}