use crate::tui::component::{Action, Component, ComponentState, Focus};
use anyhow::{Context, Result, bail};
use ratatui::buffer::Buffer;
use ratatui::crossterm::event::{Event, KeyCode, KeyEvent, MouseEvent, MouseEventKind};
use ratatui::layout::{Alignment, Position, Rect};
use ratatui::prelude::Style;
use ratatui::style::{Color, Modifier};
use ratatui::widgets::{Block, Borders, StatefulWidget, Widget};
use std::fs;
use std::path::PathBuf;
use tui_tree_widget::{Tree, TreeItem, TreeState};

#[derive(Debug)]
pub struct Explorer<'a> {
    pub(crate) root_path: PathBuf,
    tree_items: TreeItem<'a, String>,
    tree_state: TreeState<String>,
    pub(crate) component_state: ComponentState,
}

impl<'a> Explorer<'a> {
    pub fn id() -> &'static str {
        "Explorer"
    }

    pub fn new(path: &std::path::PathBuf) -> Result<Self> {
        let explorer = Explorer {
            root_path: path.to_owned(),
            tree_items: Self::build_tree_from_path(path.to_owned())?,
            tree_state: TreeState::default(),
            component_state: ComponentState::default().with_help_text(
                "(↑/k)/(↓/j): Select item | ←/h: Close folder | →/l/Enter: Open folder",
            ),
        };
        Ok(explorer)
    }

    fn build_tree_from_path(path: std::path::PathBuf) -> Result<TreeItem<'static, String>> {
        let mut children = vec![];
        if let Ok(entries) = fs::read_dir(&path) {
            let mut paths = entries
                .map(|res| res.map(|e| e.path()))
                .collect::<Result<Vec<_>, std::io::Error>>()
                .context(format!(
                    "Failed to build vector of paths under directory: {:?}",
                    path
                ))?;
            paths.sort();
            for path in paths {
                if path.is_dir() {
                    children.push(Self::build_tree_from_path(path)?);
                } else {
                    if let Ok(path) = std::path::absolute(&path) {
                        let path_str = path.to_string_lossy().to_string();
                        children.push(TreeItem::new_leaf(
                            path_str,
                            path.file_name()
                                .context("Failed to get file name from path.")?
                                .to_string_lossy()
                                .to_string(),
                        ));
                    }
                }
            }
        }

        let abs = std::path::absolute(&path)
            .context(format!(
                "Failed to find absolute path for TreeItem: {:?}",
                path
            ))?
            .to_string_lossy()
            .to_string();
        TreeItem::new(
            abs,
            path.file_name()
                .expect("Failed to get file name from path.")
                .to_string_lossy()
                .to_string(),
            children,
        )
        .context("Failed to build tree from path.")
    }

    pub fn selected(&self) -> Result<String> {
        if let Some(path) = self.tree_state.selected().last() {
            return Ok(std::path::absolute(path)?
                .to_str()
                .context("Failed to get absolute path to selected TreeItem")?
                .to_string());
        }
        bail!("Failed to get selected TreeItem")
    }
}

impl<'a> Widget for &mut Explorer<'a> {
    fn render(self, area: Rect, buf: &mut Buffer) {
        if let Ok(tree) = Tree::new(&self.tree_items.children()) {
            let file_name = self.root_path.file_name().unwrap_or("Unknown".as_ref());
            StatefulWidget::render(
                tree.style(Style::default())
                    .block(
                        Block::default()
                            .borders(Borders::ALL)
                            .title(file_name.to_string_lossy())
                            .title_style(Style::default().fg(Color::Green))
                            .title_alignment(Alignment::Center),
                    )
                    .highlight_style(
                        Style::new()
                            .fg(Color::Black)
                            .bg(Color::Rgb(57, 59, 64))
                            .add_modifier(Modifier::BOLD),
                    ),
                area,
                buf,
                &mut self.tree_state,
            );
        }
    }
}

impl<'a> Component for Explorer<'a> {
    fn handle_event(&mut self, event: Event) -> Result<Action> {
        if let Some(key_event) = event.as_key_event() {
            // Handle events here that should not be passed on to the vim emulation handler.
            match self.handle_key_events(key_event)? {
                Action::Handled => return Ok(Action::Handled),
                _ => {}
            }
        }
        if let Some(mouse_event) = event.as_mouse_event() {
            match self.handle_mouse_events(mouse_event)? {
                Action::Handled => return Ok(Action::Handled),
                _ => {}
            }
        }
        Ok(Action::Pass)
    }

    fn handle_key_events(&mut self, key: KeyEvent) -> Result<Action> {
        let changed = match key.code {
            KeyCode::Up | KeyCode::Char('k') => self.tree_state.key_up(),
            KeyCode::Down | KeyCode::Char('j') => self.tree_state.key_down(),
            KeyCode::Left | KeyCode::Char('h') => {
                // Do not call key_left(); Calling it on a closed folder clears the selection.
                let key = self.tree_state.selected().to_owned();
                self.tree_state.close(key.as_ref())
            }
            KeyCode::Right | KeyCode::Char('l') => self.tree_state.key_right(),
            KeyCode::Enter => self.tree_state.toggle_selected(),
            _ => false,
        };
        if changed {
            return Ok(Action::Handled);
        }
        Ok(Action::Noop)
    }

    fn handle_mouse_events(&mut self, mouse: MouseEvent) -> Result<Action> {
        let changed = match mouse.kind {
            MouseEventKind::ScrollDown => self.tree_state.scroll_down(1),
            MouseEventKind::ScrollUp => self.tree_state.scroll_up(1),
            MouseEventKind::Down(_button) => self
                .tree_state
                .click_at(Position::new(mouse.column, mouse.row)),
            _ => false,
        };
        if changed {
            return Ok(Action::Handled);
        }
        Ok(Action::Noop)
    }

    fn is_active(&self) -> bool {
        self.component_state.focus == Focus::Active
    }
}