//! Top-level dropdown menu bar (F1 toggle).
//!
//! Inspired by QBasic 4.5's menu system and aptitude's TUI menus.
//! Activated with F1. Navigate with arrow keys, Enter to select, Esc/F1 to close.
//! Menu items dispatch to slash-commands or internal actions.

use crate::core::app::App;
use crate::tui::foundation::{NaimPalette, NaimStyle};
use ratatui::prelude::*;
use std::collections::VecDeque;

/// A single item inside a dropdown menu.
#[derive(Debug, Clone)]
pub struct MenuItem {
    pub label: String,
    /// Slash-command to dispatch, or an internal action tag.
    pub action: String,
    /// True if this item is a separator line (visual only).
    pub separator: bool,
}

/// A top-level menu heading that opens a dropdown.
#[derive(Debug, Clone)]
pub struct MenuBarEntry {
    pub label: String,
    pub items: Vec<MenuItem>,
}

impl MenuBarEntry {
    pub fn new(label: &str, items: Vec<MenuItem>) -> Self {
        Self { label: label.to_owned(), items }
    }
}

/// State machine for the menu bar overlay.
#[derive(Debug)]
pub struct MenuBarState {
    pub entries: Vec<MenuBarEntry>,
    /// Index into `entries` of the currently open dropdown, or `None` if closed.
    pub open_dropdown: Option<usize>,
    /// Highlighted item index within the open dropdown.
    pub highlight_idx: usize,
    /// True when the menu bar is active (F1 toggles this).
    pub active: bool,
    /// Queue of actions selected by the user (consumed by main loop).
    pub pending_actions: VecDeque<String>,
}

impl MenuBarState {
    pub fn new() -> Self {
        Self {
            entries: default_menus(),
            open_dropdown: None,
            highlight_idx: 0,
            active: false,
            pending_actions: VecDeque::new(),
        }
    }

    /// Toggle menu bar on/off.
    pub fn toggle(&mut self) {
        if self.active {
            self.close();
        } else {
            self.active = true;
            self.open_dropdown = Some(0);
            self.highlight_idx = 0;
        }
    }

    /// Close the menu bar entirely.
    pub fn close(&mut self) {
        self.active = false;
        self.open_dropdown = None;
    }

    /// Open a specific dropdown by index.
    pub fn open(&mut self, idx: usize) {
        self.active = true;
        self.open_dropdown = Some(idx);
        self.highlight_idx = 0;
    }

    /// Move highlight right to the next menu heading.
    pub fn move_right(&mut self) {
        if let Some(cur) = self.open_dropdown {
            let next = (cur + 1) % self.entries.len();
            self.open_dropdown = Some(next);
            self.highlight_idx = 0;
        }
    }

    /// Move highlight left to the previous menu heading.
    pub fn move_left(&mut self) {
        if let Some(cur) = self.open_dropdown {
            let prev = if cur == 0 { self.entries.len() - 1 } else { cur - 1 };
            self.open_dropdown = Some(prev);
            self.highlight_idx = 0;
        }
    }

    /// Move highlight down within the current dropdown.
    pub fn move_down(&mut self) {
        if let Some(di) = self.open_dropdown {
            let items = &self.entries[di].items;
            let non_sep: Vec<usize> = items.iter().enumerate()
                .filter(|(_, it)| !it.separator)
                .map(|(i, _)| i)
                .collect();
            if non_sep.is_empty() { return; }
            let cur_pos = non_sep.iter().position(|&i| i == self.highlight_idx)
                .unwrap_or(0);
            let next_pos = (cur_pos + 1) % non_sep.len();
            self.highlight_idx = non_sep[next_pos];
        }
    }

    /// Move highlight up within the current dropdown.
    pub fn move_up(&mut self) {
        if let Some(di) = self.open_dropdown {
            let items = &self.entries[di].items;
            let non_sep: Vec<usize> = items.iter().enumerate()
                .filter(|(_, it)| !it.separator)
                .map(|(i, _)| i)
                .collect();
            if non_sep.is_empty() { return; }
            let cur_pos = non_sep.iter().position(|&i| i == self.highlight_idx)
                .unwrap_or(0);
            let prev_pos = if cur_pos == 0 { non_sep.len() - 1 } else { cur_pos - 1 };
            self.highlight_idx = non_sep[prev_pos];
        }
    }

    /// Select the currently highlighted item.
    pub fn select(&mut self) {
        if let Some(di) = self.open_dropdown {
            if let Some(item) = self.entries[di].items.get(self.highlight_idx) {
                if !item.separator {
                    self.pending_actions.push_back(item.action.clone());
                    self.close();
                }
            }
        }
    }

    /// Pop the next pending action (if any).
    pub fn pop_action(&mut self) -> Option<String> {
        self.pending_actions.pop_front()
    }
}

/// Render the menu bar. When active, draws the top row with headings and
/// the currently-open dropdown beneath it.
pub fn render_menubar(area: Rect, buf: &mut Buffer, state: &MenuBarState, palette: &NaimPalette, _app: &App) {
    if area.width == 0 || area.height == 0 {
        return;
    }

    let menu_bg = palette.statusbar_bg;
    let heading_fg = palette.self_fg;
    let heading_active_fg = palette.buddy_waiting_fg;
    let item_fg = palette.event_fg;
    let item_hl_fg = palette.self_fg;
    let item_hl_bg = palette.input_bg;
    let sep_fg = palette.buddy_idle_fg;
    let border_color = palette.buddy_idle_fg;

    // ── Menu bar row (always drawn when active) ──
    let bar_area = Rect::new(area.x, area.y, area.width, 1);
    let bar_bg_style = NaimStyle::pair(heading_fg, menu_bg);
    for x in bar_area.x..bar_area.x + bar_area.width {
        buf.set_string(x, bar_area.y, " ", bar_bg_style);
    }

    let mut x = bar_area.x;
    for (i, entry) in state.entries.iter().enumerate() {
        let is_open = state.open_dropdown == Some(i);
        let style = if is_open {
            NaimStyle::bold_pair(heading_active_fg, item_hl_bg)
        } else {
            NaimStyle::pair(heading_fg, menu_bg)
        };
        // Pad heading with a space on each side.
        let label = format!(" {} ", entry.label);
        if x + label.chars().count() as u16 <= bar_area.x + bar_area.width {
            buf.set_string(x, bar_area.y, &label, style);
            x += label.chars().count() as u16;
        }
    }

    // Right-align help hint.
    let help = " Esc=Close  \u{2190}\u{2192}=Menus  \u{2191}\u{2193}=Items  Enter=Select ";
    let hw = help.chars().count() as u16;
    if bar_area.width >= hw + 4 {
        buf.set_string(bar_area.x + bar_area.width - hw - 2, bar_area.y, help,
            NaimStyle::pair(sep_fg, menu_bg));
    }

    // ── Dropdown panel ──
    if let Some(di) = state.open_dropdown {
        let items = &state.entries[di].items;
        if items.is_empty() { return; }

        // Dropdown width: max item length + 4 padding, or heading width + 8.
        let heading_x = heading_x_offset(&state.entries, di, bar_area.x);
        let max_item_w = items.iter().map(|it| it.label.chars().count()).max().unwrap_or(10);
        let heading_offset = (heading_x - bar_area.x as usize) as u16;
        let dd_width = (max_item_w + 4).max(state.entries[di].label.chars().count() + 8)
            .min((area.width as usize).saturating_sub(heading_offset as usize)) as u16;
        let dd_height = (items.len() as u16 + 2).min(area.height.saturating_sub(2));

        let dd_x = (heading_x as u16).min(area.x + area.width - dd_width);
        let dd_y = bar_area.y + 1;
        let dd_area = Rect::new(dd_x, dd_y, dd_width, dd_height);

        // Background.
        for y in dd_area.y..dd_area.y + dd_area.height {
            for x in dd_area.x..dd_area.x + dd_area.width {
                buf.set_string(x, y, " ", NaimStyle::pair(item_fg, item_hl_bg));
            }
        }

        // Border.
        let border = NaimStyle::pair(border_color, item_hl_bg);
        // Top-left, top-right corners.
        if dd_area.width >= 2 && dd_area.height >= 2 {
            buf.set_string(dd_area.x, dd_area.y, "\u{250C}", border);
            buf.set_string(dd_area.x + dd_area.width - 1, dd_area.y, "\u{2510}", border);
            buf.set_string(dd_area.x, dd_area.y + dd_area.height - 1, "\u{2514}", border);
            buf.set_string(dd_area.x + dd_area.width - 1, dd_area.y + dd_area.height - 1, "\u{2518}", border);
        }
        // Horizontal borders.
        for bx in (dd_area.x + 1)..(dd_area.x + dd_area.width - 1) {
            buf.set_string(bx, dd_area.y, "\u{2500}", border);
            buf.set_string(bx, dd_area.y + dd_area.height - 1, "\u{2500}", border);
        }
        // Vertical borders.
        for by in (dd_area.y + 1)..(dd_area.y + dd_area.height - 1) {
            buf.set_string(dd_area.x, by, "\u{2502}", border);
            buf.set_string(dd_area.x + dd_area.width - 1, by, "\u{2502}", border);
        }

        // Items.
        let inner_x = dd_area.x + 1;
        let inner_w = dd_area.width.saturating_sub(2);
        for (idx, item) in items.iter().enumerate() {
            let row = dd_area.y + 1 + idx as u16;
            if row >= dd_area.y + dd_area.height - 1 { break; }

            if item.separator {
                // Separator line.
                for sx in (inner_x + 1)..(inner_x + inner_w - 1) {
                    buf.set_string(sx, row, "\u{2500}", NaimStyle::pair(sep_fg, item_hl_bg));
                }
            } else {
                let is_hl = idx == state.highlight_idx;
                let style = if is_hl {
                    NaimStyle::bold_pair(item_hl_fg, palette.event_alt_fg)
                } else {
                    NaimStyle::pair(item_fg, item_hl_bg)
                };
                // Clear the row.
                for sx in inner_x..(inner_x + inner_w) {
                    buf.set_string(sx, row, " ", style);
                }
                // Truncate label to fit.
                let max_chars = inner_w as usize;
                let display: String = item.label.chars().take(max_chars).collect();
                buf.set_string(inner_x, row, &display, style);
                // Right-align the shortcut hint if present.
                if let Some((_lbl, _shortcut)) = item.label.split_once('\t') {
                    if let Some(sc) = item.label.split('\t').nth(1) {
                        let sc_display: String = sc.chars().take(max_chars).collect();
                        let sc_w = sc_display.chars().count() as u16;
                        if sc_w < inner_w {
                            buf.set_string(inner_x + inner_w - sc_w, row, &sc_display,
                                NaimStyle::pair(sep_fg, if is_hl { palette.event_alt_fg } else { item_hl_bg }));
                        }
                    }
                }
            }
        }
    }
}

/// Compute the x-offset (in chars) for a given dropdown heading.
fn heading_x_offset(entries: &[MenuBarEntry], target: usize, base_x: u16) -> usize {
    let mut x = base_x as usize;
    for (i, e) in entries.iter().enumerate() {
        if i == target { return x; }
        x += e.label.chars().count() + 2; // " label " → 1 space + label + 1 space
    }
    x
}

/// Build the default menu structure.
///
/// ## Action conventions
///
/// - **Direct execution** (safe with no args): action is the exact `/command`.
///   e.g. `"/clear"`, `"/disconnect"`.
/// - **Prompt mode** (needs user input): action is `"__prompt:/cmd "`.
///   The `__prompt:` prefix causes the input bar to be pre-filled with the
///   command prefix so the user can type the required arguments and press Enter.
///   e.g. `"__prompt:/join "` puts `/join ` in the input bar.
/// - **Internal actions**: `"__server_list"` etc. are handled directly in
///   the main event loop's menu dispatch block.
fn default_menus() -> Vec<MenuBarEntry> {
    use MenuItem as MI;
    vec![
        // ── File ────────────────────────────────────────────────────
        MenuBarEntry::new("File", vec![
            MI { label: "Connect…\t__prompt:/connect ".into(), action: "__prompt:/connect ".into(), separator: false },
            MI { label: "Disconnect\t/disconnect".into(), action: "/disconnect".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Save Config\t/save".into(), action: "/save".into(), separator: false },
            MI { label: "Source File…\t__prompt:/source ".into(), action: "__prompt:/source ".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Quit\t/quit".into(), action: "/quit".into(), separator: false },
        ]),
        // ── Edit ────────────────────────────────────────────────────
        MenuBarEntry::new("Edit", vec![
            MI { label: "Clear Window\t/clear".into(), action: "/clear".into(), separator: false },
            MI { label: "Clear All Windows\t/clearall".into(), action: "/clearall".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Set Variable…\t__prompt:/set ".into(), action: "__prompt:/set ".into(), separator: false },
            MI { label: "Get Variable…\t__prompt:/get ".into(), action: "__prompt:/get ".into(), separator: false },
            MI { label: "Evaluate…\t__prompt:/eval ".into(), action: "__prompt:/eval ".into(), separator: false },
        ]),
        // ── View ────────────────────────────────────────────────────
        MenuBarEntry::new("View", vec![
            MI { label: "Toggle Winlist\t/winlist".into(), action: "/winlist".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Jump to Window…\t__prompt:/jump ".into(), action: "__prompt:/jump ".into(), separator: false },
            MI { label: "Jump Back\t/jumpback".into(), action: "/jumpback".into(), separator: false },
            MI { label: "Next Unread\tCtrl-N".into(), action: "__internal:ctrl_n".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Redraw Screen\tCtrl-L".into(), action: "__internal:ctrl_l".into(), separator: false },
        ]),
        // ── Connect ─────────────────────────────────────────────────
        // NOTE: BitChat menu entry removed in 0.10.2. See NOTICES.md.
        MenuBarEntry::new("Connect", vec![
            MI { label: "IRC…\t__prompt:/connect irc ".into(), action: "__prompt:/connect irc ".into(), separator: false },
            MI { label: "Matrix…\t__prompt:/connect matrix ".into(), action: "__prompt:/connect matrix ".into(), separator: false },
            MI { label: "ADC/DC++…\t__prompt:/connect adc ".into(), action: "__prompt:/connect adc ".into(), separator: false },
            MI { label: "Discord…\t__prompt:/connect discord ".into(), action: "__prompt:/connect discord ".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Server List\t__server_list".into(), action: "__server_list".into(), separator: false },
            MI { label: "Disconnect All\t/disconnect".into(), action: "/disconnect".into(), separator: false },
        ]),
        // ── Help ────────────────────────────────────────────────────
        MenuBarEntry::new("Help", vec![
            MI { label: "Help\t/help".into(), action: "/help".into(), separator: false },
            MI { label: "Version\t/version".into(), action: "/version".into(), separator: false },
            MI { label: "Client Info\t/info".into(), action: "/info".into(), separator: false },
            MI { label: String::new(), action: String::new(), separator: true },
            MI { label: "Transfers\t/transfers".into(), action: "/transfers".into(), separator: false },
            MI { label: "Commands\t/help".into(), action: "/help".into(), separator: false },
        ]),
    ]
}