use std::usize;

use crate::{float::floating_window, theme::*};
use crossterm::event::{KeyCode, KeyEvent, KeyEventKind};
use ego_tree::{tree, NodeId};
use ratatui::{
    layout::Rect,
    style::{Style, Stylize},
    text::Line,
    widgets::{Block, Borders, List, ListState},
    Frame,
};

struct ListNode {
    name: &'static str,
    command: &'static str,
}

/// This is a data structure that has everything necessary to draw and manage a menu of commands
pub struct CustomList {
    /// The tree data structure, to represent regular items
    /// and "directories"
    inner_tree: ego_tree::Tree<ListNode>,
    /// This stack keeps track of our "current dirrectory". You can think of it as `pwd`. but not
    /// just the current directory, all paths that took us here, so we can "cd .."
    visit_stack: Vec<NodeId>,
    /// This is the state asociated with the list widget, used to display the selection in the
    /// widget
    list_state: ListState,
    /// This stores the preview windows state. If it is None, it will not be displayed.
    /// If it is Some, we show it with the content of the selected item
    preview_window_state: Option<PreviewWindowState>,
}

/// This struct stores the preview window state
struct PreviewWindowState {
    /// The text inside the window
    text: Vec<String>,
    /// The current line scroll
    scroll: usize,
}

impl PreviewWindowState {
    /// Create a new PreviewWindowState
    pub fn new(text: Vec<String>) -> Self {
        Self { text, scroll: 0 }
    }
}

impl CustomList {
    pub fn new() -> Self {
        // When a function call ends with an exclamation mark, it means it's a macro, like in this
        // case the tree! macro expands to `ego-tree::tree` data structure
        let tree = tree!(ListNode {
            name: "root",
            command: ""
        } => {
            ListNode {
                name: "Full System Update",
                command: include_str!("commands/system-update.sh"),
            },
            ListNode {
                name: "Setup Bash Prompt",
                command: "bash -c \"$(curl -s https://raw.githubusercontent.com/ChrisTitusTech/mybash/main/setup.sh)\""
            },
            ListNode {
                name: "Setup Neovim",
                command: "bash -c \"$(curl -s https://raw.githubusercontent.com/ChrisTitusTech/neovim/main/setup.sh)\""
            },
            // ListNode {
            //     name: "Just ls, nothing special, trust me",
            //     command: include_str!("commands/special_ls.sh"),
            // },
            ListNode {
                name: "System Setup",
                command: ""
            } => {
                ListNode {
                    name: "Build Prerequisites",
                    command: include_str!("commands/system-setup/1-compile-setup.sh"),
                },
                ListNode {
                    name: "Gaming Dependencies",
                    command: include_str!("commands/system-setup/2-gaming-setup.sh"),
                },
                ListNode {
                    name: "Recursion?",
                    command: "cargo run"
                }
            },
            ListNode {
                name: "Titus Dotfiles",
                command: ""
            } => {
                ListNode {
                    name: "Alacritty Setup",
                    command: include_str!("commands/dotfiles/alacritty-setup.sh"),
                },
                ListNode {
                    name: "Kitty Setup",
                    command: include_str!("commands/dotfiles/kitty-setup.sh"),
                },
                ListNode {
                    name: "Rofi Setup",
                    command: include_str!("commands/dotfiles/rofi-setup.sh"),
                },
            }
        });
        // We don't get a reference, but rather an id, because references are siginficantly more
        // paintfull to manage
        let root_id = tree.root().id();
        Self {
            inner_tree: tree,
            visit_stack: vec![root_id],
            list_state: ListState::default().with_selected(Some(0)),
            // By default the PreviewWindowState is set to None, so it is not being shown
            preview_window_state: None,
        }
    }

    /// Draw our custom widget to the frame
    pub fn draw(&mut self, frame: &mut Frame, area: Rect) {
        // Get the last element in the `visit_stack` vec
        let theme = get_theme();
        let curr = self
            .inner_tree
            .get(*self.visit_stack.last().unwrap())
            .unwrap();
        let mut items = vec![];

        // If we are not at the root of our filesystem tree, we need to add `..` path, to be able
        // to go up the tree
        // icons:   
        if !self.at_root() {
            items.push(Line::from(format!("{}  ..", theme.dir_icon)).style(theme.dir_color));
        }

        // Iterate through all the children
        for node in curr.children() {
            // The difference between a "directory" and a "command" is simple: if it has children,
            // it's a directory and will be handled as such
            if node.has_children() {
                items.push(
                    Line::from(format!("{}  {}", theme.dir_icon, node.value().name))
                        .style(theme.dir_color),
                );
            } else {
                items.push(
                    Line::from(format!("{}  {}", theme.cmd_icon, node.value().name))
                        .style(theme.cmd_color),
                );
            }
        }

        // create the normal list widget containing only item in our "working directory" / tree
        // node
        let list = List::new(items)
            .highlight_style(Style::default().reversed())
            .block(Block::default().borders(Borders::ALL).title(format!(
                "Linux Toolbox - {}",
                chrono::Local::now().format("%Y-%m-%d")
            )))
            .scroll_padding(1);

        // Render it
        frame.render_stateful_widget(list, area, &mut self.list_state);

        // Draw the preview window if it's active
        if let Some(pw_state) = &self.preview_window_state {
            // Set the window to be floating
            let floating_area = floating_window(area);

            // Draw the preview windows lines
            let lines: Vec<Line> = pw_state
                .text
                .iter()
                .skip(pw_state.scroll)
                .take(floating_area.height as usize)
                .map(|line| Line::from(line.as_str()))
                .collect();

            // Create list widget
            let list = List::new(lines)
                .block(
                    Block::default()
                        .borders(Borders::ALL)
                        .title("Action preview"),
                )
                .highlight_style(Style::default().reversed());

            // Finally render the preview window
            frame.render_widget(list, floating_area);
        }
    }

    /// Handle key events, we are only interested in `Press` and `Repeat` events
    pub fn handle_key(&mut self, event: KeyEvent) -> Option<&'static str> {
        if event.kind == KeyEventKind::Release {
            return None;
        }
        match event.code {
            // Damm you Up arrow, use vim lol
            KeyCode::Char('j') | KeyCode::Down => {
                // If the preview window is active, scroll down and consume the scroll action,
                // so the scroll does not happen in the main window as well
                if self.preview_window_state.is_some() {
                    self.scroll_preview_window_down();
                    return None;
                }

                self.try_scroll_down();
                None
            }
            KeyCode::Char('k') | KeyCode::Up => {
                // If the preview window is active, scroll up and consume the scroll action,
                // so the scroll does not happen in the main window as well
                if self.preview_window_state.is_some() {
                    self.scroll_preview_window_up();
                    return None;
                }

                self.try_scroll_up();
                None
            }
            // The 'p' key toggles the preview on and off
            KeyCode::Char('p') => {
                self.toggle_preview_window();
                None
            }
            KeyCode::Enter => self.handle_enter(),
            _ => None,
        }
    }
    fn toggle_preview_window(&mut self) {
        // If the preview window is active, disable it
        if self.preview_window_state.is_some() {
            self.preview_window_state = None;
        } else {
            // If the preview windows is not active, show it

            // Get the selected command
            if let Some(selected_command) = self.get_selected_command() {
                // If command is a folder, we don't display a preview
                if selected_command == "" {
                    return;
                }

                // Reconstruct the line breaks and file formatting after the
                // 'include_str!()' call in the node
                let lines: Vec<String> = selected_command
                    .lines()
                    .map(|line| line.to_string())
                    .collect();

                // Show the preview window with the text lines
                self.preview_window_state = Some(PreviewWindowState::new(lines));
            }
        }
    }
    fn try_scroll_up(&mut self) {
        self.list_state
            .select(Some(self.list_state.selected().unwrap().saturating_sub(1)));
    }
    fn try_scroll_down(&mut self) {
        let curr = self
            .inner_tree
            .get(*self.visit_stack.last().unwrap())
            .unwrap();

        let count = curr.children().count();

        let curr_selection = self.list_state.selected().unwrap();
        if self.at_root() {
            self.list_state
                .select(Some((curr_selection + 1).min(count - 1)));
        } else {
            // When we are not at the root, we have to account for 1 more "virtual" node, `..`. So
            // the count is 1 bigger (select is 0 based, because it's an index)
            self.list_state
                .select(Some((curr_selection + 1).min(count)));
        }
    }

    /// Scroll the preview window down
    fn scroll_preview_window_down(&mut self) {
        if let Some(pw_state) = &mut self.preview_window_state {
            if pw_state.scroll + 1 < pw_state.text.len() {
                pw_state.scroll += 1;
            }
        }
    }

    /// Scroll the preview window up
    fn scroll_preview_window_up(&mut self) {
        if let Some(pw_state) = &mut self.preview_window_state {
            if pw_state.scroll > 0 {
                pw_state.scroll = pw_state.scroll.saturating_sub(1);
            }
        }
    }

    /// This method return the currently selected command, or None if no command is selected.
    /// It was extracted from the 'handle_enter()'
    ///
    /// This could probably be integrated into the 'handle_enter()' method as to avoid code
    /// duplication, but I don't want to make too major changes to the codebase.
    fn get_selected_command(&self) -> Option<&'static str> {
        let curr = self
            .inner_tree
            .get(*self.visit_stack.last().unwrap())
            .unwrap();
        let selected = self.list_state.selected().unwrap();

        // If we are not at the root and the first item is selected, it's the `..` item
        if !self.at_root() && selected == 0 {
            return None;
        }

        for (mut idx, node) in curr.children().enumerate() {
            if !self.at_root() {
                idx += 1;
            }
            if idx == selected {
                return Some(node.value().command);
            }
        }
        None
    }

    /// Handles the <Enter> key. This key can do 3 things:
    /// - Run a command, if it is the currently selected item,
    /// - Go up a directory
    /// - Go down into a directory
    /// Returns `Some(command)` when command is selected, othervise we returns `None`
    fn handle_enter(&mut self) -> Option<&'static str> {
        // Get the current node (current directory)
        let curr = self
            .inner_tree
            .get(*self.visit_stack.last().unwrap())
            .unwrap();
        let selected = self.list_state.selected().unwrap();

        // if we are not at the root, and the first element is selected,
        // we can be sure it's '..', so we go up the directory
        if !self.at_root() && selected == 0 {
            self.visit_stack.pop();
            self.list_state.select(Some(0));
            return None;
        }

        for (mut idx, node) in curr.children().enumerate() {
            // at this point, we know that we are not on the .. item, and our indexes of the items never had ..
            // item. so to balance it out, in case the selection index contains .., se add 1 to our node index
            if !self.at_root() {
                idx += 1;
            }
            if idx == selected {
                if node.has_children() {
                    self.visit_stack.push(node.id());
                    self.list_state.select(Some(0));
                    return None;
                } else {
                    return Some(node.value().command);
                }
            }
        }
        None
    }

    /// Checks weather the current tree node is the root node (can we go up the tree or no)
    /// Returns `true` if we can't go up the tree (we are at the tree root)
    /// else returns `false`
    fn at_root(&self) -> bool {
        self.visit_stack.len() == 1
    }
}