//! Application-level "miscellaneous" state: scroll, input buffer,
//! overlay stack, toasts, editor, and autocomplete.
use std::path::PathBuf;
use std::sync::Arc;
use tokio::sync::RwLock;
use super::types::Overlay;

/// A shared, async-writable cache of directory entries, used to avoid
/// re-reading a directory every render frame.
#[derive(Clone)]
pub struct DirCache {
    entries: Arc<RwLock<Vec<PathBuf>>>,
}

impl DirCache {
    /// Create an empty `DirCache`.
    pub fn new() -> Self {
        DirCache {
            entries: Arc::new(RwLock::new(Vec::new())),
        }
    }

    /// Replace the cached entries (async write).
    pub async fn set(&self, paths: Vec<PathBuf>) {
        let mut w = self.entries.write().await;
        *w = paths;
    }
}

/// Manages the viewport scroll offset.
#[derive(Debug, Clone)]
pub struct ScrollState {
    pub offset: usize,
    pub max_visible: usize,
}

impl ScrollState {
    /// Create a `ScrollState` with zero offset and 30 rows visible.
    pub fn new() -> Self {
        ScrollState {
            offset: 0,
            max_visible: 30,
        }
    }

    /// Scroll the viewport up by `amount` lines (increasing the offset).
    /// Scroll the viewport up by `amount` lines (increasing the offset).
    pub fn scroll_up(&mut self, amount: usize) {
        self.offset = self.offset.saturating_add(amount);
    }

    /// Scroll the viewport down by `amount` lines (decreasing the offset).
    pub fn scroll_down(&mut self, amount: usize) {
        self.offset = self.offset.saturating_sub(amount);
    }

    /// Update the maximum number of visible lines.
    pub fn set_max_visible(&mut self, max: usize) {
        self.max_visible = max;
    }
}

/// The user's input buffer, cursor position, history, and autocomplete
/// state for the chat prompt.
#[derive(Debug, Clone)]
pub struct InputState {
    pub buffer: String,
    pub cursor: usize,
    pub history: Vec<String>,
    pub history_idx: Option<usize>,
    pub autocomplete_prefix: String,
    pub autocomplete_candidates: Vec<String>,
    pub autocomplete_idx: usize,
    pub autocomplete_visible: bool,
    pub history_file: Option<PathBuf>,
}

const COMMANDS: &[&str] = &[
    "/help",
    "/quit",
    "/clear",
    "/lesson",
    "/login",
    "/login zen",
    "/login openai",
    "/edit",
    "/mcp add",
    "/model",
    "/model ls",
    "/model add",
    "/workflow",
    "/workflow run",
    "/todo",
    "/usage",
    "/compact",
];

impl InputState {
    /// Create an empty input state with no buffer, no history, and no
    /// autocomplete.
    pub fn new() -> Self {
        InputState {
            buffer: String::new(),
            cursor: 0,
            history: Vec::new(),
            history_idx: None,
            autocomplete_prefix: String::new(),
            autocomplete_candidates: Vec::new(),
            autocomplete_idx: 0,
            autocomplete_visible: false,
            history_file: None,
        }
    }

    /// Hide the autocomplete dropdown and clear its state.
    pub fn close_autocomplete(&mut self) {
        self.autocomplete_visible = false;
        self.autocomplete_candidates.clear();
        self.autocomplete_prefix.clear();
        self.autocomplete_idx = 0;
    }

    /// Open or refresh the autocomplete dropdown by filtering `COMMANDS`
    /// against the current buffer prefix.
    ///
    /// Flow: if buffer is empty or doesn't start with `/`, close and return
    /// → filter `COMMANDS` by prefix match → store candidates → set
    /// `autocomplete_visible` if any candidates found.
    pub fn open_autocomplete(&mut self) {
        let trimmed = self.buffer.trim().to_string();
        if trimmed.is_empty() || !trimmed.starts_with('/') {
            self.close_autocomplete();
            return;
        }

        let prefix = trimmed.to_lowercase();
        self.autocomplete_candidates = COMMANDS
            .iter()
            .filter(|c| c.starts_with(&prefix))
            .map(std::string::ToString::to_string)
            .collect();
        self.autocomplete_prefix = prefix;
        self.autocomplete_idx = 0;
        self.autocomplete_visible = !self.autocomplete_candidates.is_empty();
    }

    /// Move the autocomplete selection up (forward=false) or down (forward=true).
    /// Wraps around at the boundaries.
    pub fn cycle_autocomplete(&mut self, forward: bool) {
        let n = self.autocomplete_candidates.len();
        if n == 0 { return; }
        if forward {
            self.autocomplete_idx = (self.autocomplete_idx + 1) % n;
        } else {
            self.autocomplete_idx = if self.autocomplete_idx == 0 { n - 1 } else { self.autocomplete_idx - 1 };
        }
    }

    /// Accept the currently selected autocomplete candidate, placing it
    /// in the buffer and closing the dropdown.
    ///
    /// Return: `true` if a candidate was selected, `false` if none existed.
    pub fn select_autocomplete(&mut self) -> bool {
        if let Some(candidate) = self.autocomplete_candidates.get(self.autocomplete_idx) {
            self.buffer = candidate.clone();
            self.cursor = self.buffer.len();
            self.close_autocomplete();
            true
        } else {
            false
        }
    }

    /// Legacy inline tab-complete — opens the dropdown on first Tab press,
    /// then cycles forward on subsequent presses.
    pub fn tab_complete(&mut self) {
        // Legacy inline tab-complete — used as a fallback when the dropdown
        // isn't visible yet. Opens the dropdown on the first Tab press.
        if self.autocomplete_visible {
            self.cycle_autocomplete(true);
        } else {
            self.open_autocomplete();
        }
    }

    /// Move the cursor left by one character (if not at the start).
    pub fn char_left(&mut self) {
        if self.cursor > 0 {
            self.cursor -= 1;
        }
    }

    /// Move the cursor right by one character (if not at the end).
    pub fn char_right(&mut self) {
        if self.cursor < self.buffer.len() {
            self.cursor += 1;
        }
    }

    /// Insert a character at the cursor position.
    pub fn insert(&mut self, c: char) {
        self.buffer.insert(self.cursor, c);
        self.cursor += 1;
    }

    /// Delete the character to the left of the cursor (backspace).
    pub fn delete_left(&mut self) {
        if self.cursor > 0 {
            self.cursor -= 1;
            self.buffer.remove(self.cursor);
        }
    }

    /// Delete the character at the cursor position (forward delete).
    pub fn delete_right(&mut self) {
        if self.cursor < self.buffer.len() {
            self.buffer.remove(self.cursor);
        }
    }

    pub fn submit(&mut self) -> String {
        let result = self.buffer.clone();
        if !result.is_empty() {
            if self.history.last() != Some(&result) {
                self.history.push(result.clone());
                if let Some(ref path) = self.history_file {
                    if let Ok(mut file) = std::fs::OpenOptions::new()
                        .create(true)
                        .append(true)
                        .open(path)
                    {
                        use std::io::Write;
                        let _ = writeln!(file, "{result}");
                    }
                }
            }
            self.history_idx = None;
        }
        self.buffer.clear();
        self.cursor = 0;
        result
    }

    /// Navigate backward through input history.
    pub fn history_up(&mut self) {
        if self.history.is_empty() {
            return;
        }
        let idx = match self.history_idx {
            Some(i) if i > 0 => i - 1,
            None => self.history.len() - 1,
            Some(_) => return,
        };
        self.history_idx = Some(idx);
        self.buffer = self.history[idx].clone();
        self.cursor = self.buffer.len();
    }

    /// Navigate forward through input history (back toward the newest entry).
    pub fn history_down(&mut self) {
        match self.history_idx {
            Some(i) if i < self.history.len() - 1 => {
                let idx = i + 1;
                self.history_idx = Some(idx);
                self.buffer = self.history[idx].clone();
                self.cursor = self.buffer.len();
            }
            Some(_) => {
                self.history_idx = None;
                self.buffer.clear();
                self.cursor = 0;
            }
            None => {}
        }
    }
}

/// The "miscellaneous" slice of app state: which overlay is showing,
/// toasts, thinking/connected flags, effort level, editor state, and tick.
#[derive(Debug, Clone)]
pub struct MiscState {
    pub overlay: Overlay,
    pub toasts: Vec<super::types::Toast>,
    pub last_staleness_sweep_ms: i64,
    pub thinking: bool,
    pub effort_level: usize,
    pub selected_index: usize,
    pub editor: Option<super::super::mode::editor::EditorState>,
    pub api_connected: bool,
    #[allow(dead_code)]
    pub api_context_length: Option<u32>,
    pub tick_count: u64,
    pub todo_content: String,
}

impl MiscState {
    /// Create a fresh `MiscState` with no overlay, no toasts, and default
    /// effort level 1.
    pub fn new() -> Self {
        MiscState {
            overlay: Overlay::None,
            toasts: Vec::new(),
            last_staleness_sweep_ms: 0,
            thinking: false,
            effort_level: 1,
            selected_index: 0,
            editor: None,
            api_connected: false,
            api_context_length: None,
            tick_count: 0,
            todo_content: String::new(),
        }
    }

    pub fn push_toast(&mut self, toast: super::types::Toast) {
        self.toasts.push(toast);
    }

    /// Remove and return all toasts whose lifetime has expired at `now_ms`.
    ///
    /// Return: the expired toasts (after removal).
    pub fn drain_expired_toasts(&mut self, now_ms: i64) -> Vec<super::types::Toast> {
        let expired: Vec<_> = self.toasts.iter().filter(|t| t.expired(now_ms)).cloned().collect();
        self.toasts.retain(|t| !t.expired(now_ms));
        expired
    }
}