use std::collections::HashMap;
use std::ops::{Deref, DerefMut};
use std::path::PathBuf;
use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
use std::sync::Arc;
use std::time::{SystemTime, UNIX_EPOCH};

use ratatui::layout::Direction;
use tokio::sync::{mpsc, Notify};

use crate::events::AppEvent;
use crate::layout::PaneId;
#[cfg(test)]
use crate::layout::TileLayout;
use crate::pane::{PaneRuntime, PaneState};

mod aggregate;
mod git;
mod tab;

use self::git::git_ahead_behind;
pub use self::{
    git::{derive_label_from_cwd, git_branch},
    tab::Tab,
};

static NEXT_WORKSPACE_ID: AtomicU64 = AtomicU64::new(1);

pub(crate) fn generate_workspace_id() -> String {
    let micros = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|duration| duration.as_micros())
        .unwrap_or(0);
    let counter = NEXT_WORKSPACE_ID.fetch_add(1, Ordering::Relaxed);
    format!("w{micros:x}{counter:x}")
}

/// A named workspace containing tabs.
pub struct Workspace {
    /// Stable public workspace identity, independent of display order.
    pub id: String,
    /// User-provided override. If set, auto-derived identity stops updating.
    pub custom_name: Option<String>,
    /// Fallback workspace identity source for tests, old snapshots, or missing runtimes.
    pub identity_cwd: PathBuf,
    /// Cached current git branch for the workspace repo.
    pub(crate) cached_git_branch: Option<String>,
    /// Cached ahead/behind counts for the workspace repo's current branch upstream.
    pub(crate) cached_git_ahead_behind: Option<(usize, usize)>,
    /// Stable-ish public pane numbers within this workspace.
    /// New panes append at the end; closing a pane compacts higher numbers down.
    pub public_pane_numbers: HashMap<PaneId, usize>,
    pub(crate) next_public_pane_number: usize,
    pub tabs: Vec<Tab>,
    pub active_tab: usize,
}

impl Deref for Workspace {
    type Target = Tab;

    fn deref(&self) -> &Self::Target {
        self.active_tab()
            .expect("workspace must always have at least one active tab")
    }
}

impl DerefMut for Workspace {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.active_tab_mut()
            .expect("workspace must always have at least one active tab")
    }
}

impl Workspace {
    pub fn new(
        initial_cwd: PathBuf,
        rows: u16,
        cols: u16,
        scrollback_limit_bytes: usize,
        host_terminal_theme: crate::terminal_theme::TerminalTheme,
        events: mpsc::Sender<AppEvent>,
        render_notify: Arc<Notify>,
        render_dirty: Arc<AtomicBool>,
    ) -> std::io::Result<Self> {
        let tab = Tab::new(
            1,
            initial_cwd.clone(),
            rows,
            cols,
            scrollback_limit_bytes,
            host_terminal_theme,
            events,
            render_notify,
            render_dirty,
        )?;
        let mut public_pane_numbers = HashMap::new();
        public_pane_numbers.insert(tab.root_pane, 1);
        Ok(Self {
            id: generate_workspace_id(),
            custom_name: None,
            identity_cwd: initial_cwd.clone(),
            cached_git_branch: git_branch(&initial_cwd),
            cached_git_ahead_behind: None,
            public_pane_numbers,
            next_public_pane_number: 2,
            tabs: vec![tab],
            active_tab: 0,
        })
    }

    pub fn active_tab(&self) -> Option<&Tab> {
        self.tabs.get(self.active_tab)
    }

    pub fn active_tab_index(&self) -> usize {
        self.active_tab
    }

    pub fn active_tab_mut(&mut self) -> Option<&mut Tab> {
        self.tabs.get_mut(self.active_tab)
    }

    pub fn active_tab_display_name(&self) -> Option<String> {
        self.active_tab().map(Tab::display_name)
    }

    pub fn switch_tab(&mut self, idx: usize) {
        if idx < self.tabs.len() {
            self.active_tab = idx;
            if let Some(tab) = self.tabs.get_mut(idx) {
                for pane in tab.panes.values_mut() {
                    pane.seen = true;
                }
            }
        }
    }

    pub fn create_tab(
        &mut self,
        rows: u16,
        cols: u16,
        cwd: PathBuf,
        scrollback_limit_bytes: usize,
        host_terminal_theme: crate::terminal_theme::TerminalTheme,
    ) -> std::io::Result<usize> {
        let number = self.tabs.len() + 1;
        let events = self
            .active_tab()
            .map(|tab| tab.events.clone())
            .expect("workspace must always have at least one tab");
        let render_notify = self
            .active_tab()
            .map(|tab| tab.render_notify.clone())
            .expect("workspace must always have at least one tab");
        let render_dirty = self
            .active_tab()
            .map(|tab| tab.render_dirty.clone())
            .expect("workspace must always have at least one tab");

        let tab = Tab::new(
            number,
            cwd,
            rows,
            cols,
            scrollback_limit_bytes,
            host_terminal_theme,
            events,
            render_notify,
            render_dirty,
        )?;
        self.register_new_pane(tab.root_pane);
        self.tabs.push(tab);
        Ok(self.tabs.len() - 1)
    }

    pub fn close_tab(&mut self, idx: usize) -> bool {
        if self.tabs.len() <= 1 || idx >= self.tabs.len() {
            return false;
        }
        let tab = self.tabs.remove(idx);
        for pane_id in tab.panes.keys() {
            self.unregister_pane(*pane_id);
        }
        self.renumber_tabs();
        if self.active_tab >= self.tabs.len() {
            self.active_tab = self.tabs.len() - 1;
        } else if idx <= self.active_tab && self.active_tab > 0 {
            self.active_tab -= 1;
        }
        true
    }

    pub fn move_tab(&mut self, source_idx: usize, insert_idx: usize) -> bool {
        if source_idx >= self.tabs.len() || insert_idx > self.tabs.len() {
            return false;
        }

        let target_idx = if source_idx < insert_idx {
            insert_idx.saturating_sub(1)
        } else {
            insert_idx
        }
        .min(self.tabs.len().saturating_sub(1));

        if source_idx == target_idx {
            return false;
        }

        let active_root_pane = self.tabs.get(self.active_tab).map(|tab| tab.root_pane);
        let tab = self.tabs.remove(source_idx);
        self.tabs.insert(target_idx, tab);
        self.renumber_tabs();
        self.active_tab = active_root_pane
            .and_then(|root_pane| self.tabs.iter().position(|tab| tab.root_pane == root_pane))
            .unwrap_or(target_idx);
        true
    }

    pub fn close_active_tab(&mut self) -> bool {
        self.close_tab(self.active_tab)
    }

    pub fn split_focused(
        &mut self,
        direction: Direction,
        rows: u16,
        cols: u16,
        cwd: Option<PathBuf>,
        scrollback_limit_bytes: usize,
        host_terminal_theme: crate::terminal_theme::TerminalTheme,
    ) -> std::io::Result<PaneId> {
        let new_id = self
            .active_tab_mut()
            .expect("workspace must always have at least one tab")
            .split_focused(
                direction,
                rows,
                cols,
                cwd,
                scrollback_limit_bytes,
                host_terminal_theme,
            )?;
        self.register_new_pane(new_id);
        Ok(new_id)
    }

    /// Close the focused pane. Returns true if the workspace should close.
    pub fn close_focused(&mut self) -> bool {
        let pane_count = self
            .active_tab()
            .map(|tab| tab.layout.pane_count())
            .unwrap_or(0);
        let tab_count = self.tabs.len();
        if pane_count <= 1 {
            return tab_count <= 1 || self.close_active_tab_and_report();
        }

        if let Some((removed, runtime)) = self.active_tab_mut().and_then(Tab::close_focused) {
            self.unregister_pane(removed);
            if let Some(runtime) = runtime {
                runtime.shutdown(removed);
            }
        }
        false
    }

    /// Remove a specific pane from this workspace without terminating its runtime.
    /// Returns true if the workspace should close.
    pub fn remove_pane(&mut self, pane_id: PaneId) -> bool {
        let Some(tab_idx) = self.find_tab_index_for_pane(pane_id) else {
            return false;
        };
        let pane_count = self.tabs[tab_idx].layout.pane_count();
        let tab_count = self.tabs.len();
        if pane_count <= 1 {
            if tab_count <= 1 {
                return true;
            }
            self.tabs.remove(tab_idx);
            self.unregister_pane(pane_id);
            self.renumber_tabs();
            if self.active_tab >= self.tabs.len() {
                self.active_tab = self.tabs.len() - 1;
            } else if tab_idx <= self.active_tab && self.active_tab > 0 {
                self.active_tab -= 1;
            }
            return false;
        }

        if let Some((removed, _)) = self.tabs[tab_idx].remove_pane(pane_id) {
            self.unregister_pane(removed);
        }
        false
    }

    pub fn public_pane_number(&self, pane_id: PaneId) -> Option<usize> {
        self.public_pane_numbers.get(&pane_id).copied()
    }

    pub fn set_custom_name(&mut self, name: String) {
        self.custom_name = Some(name);
    }

    pub fn resolved_identity_cwd(&self) -> Option<PathBuf> {
        self.tabs
            .first()
            .and_then(Tab::root_cwd)
            .or_else(|| Some(self.identity_cwd.clone()))
    }

    pub fn display_name(&self) -> String {
        if let Some(name) = &self.custom_name {
            return name.clone();
        }

        self.resolved_identity_cwd()
            .map(|cwd| derive_label_from_cwd(&cwd))
            .unwrap_or_else(|| "workspace".into())
    }

    pub fn branch(&self) -> Option<String> {
        self.cached_git_branch.clone()
    }

    pub fn git_ahead_behind(&self) -> Option<(usize, usize)> {
        self.cached_git_ahead_behind
    }

    pub fn refresh_git_ahead_behind(&mut self) {
        let cwd = self.resolved_identity_cwd();
        self.cached_git_branch = cwd.as_deref().and_then(git_branch);
        self.cached_git_ahead_behind = cwd.as_deref().and_then(git_ahead_behind);
    }

    pub fn focused_runtime(&self) -> Option<&PaneRuntime> {
        self.active_tab().and_then(Tab::focused_runtime)
    }

    pub fn find_tab_index_for_pane(&self, pane_id: PaneId) -> Option<usize> {
        self.tabs
            .iter()
            .position(|tab| tab.panes.contains_key(&pane_id))
    }

    pub fn pane_state(&self, pane_id: PaneId) -> Option<&PaneState> {
        self.tabs.iter().find_map(|tab| tab.panes.get(&pane_id))
    }

    pub fn runtime(&self, pane_id: PaneId) -> Option<&PaneRuntime> {
        self.tabs.iter().find_map(|tab| tab.runtimes.get(&pane_id))
    }

    pub fn focused_pane_id(&self) -> Option<PaneId> {
        self.active_tab().map(|tab| tab.layout.focused())
    }

    pub fn close_pane(&mut self, pane_id: PaneId) -> bool {
        let tab_idx = match self.find_tab_index_for_pane(pane_id) {
            Some(idx) => idx,
            None => return false,
        };
        let pane_count = self.tabs[tab_idx].layout.pane_count();
        let tab_count = self.tabs.len();
        if pane_count <= 1 {
            if tab_count <= 1 {
                return true;
            }
            self.tabs.remove(tab_idx);
            self.unregister_pane(pane_id);
            self.renumber_tabs();
            if self.active_tab >= self.tabs.len() {
                self.active_tab = self.tabs.len() - 1;
            } else if tab_idx <= self.active_tab && self.active_tab > 0 {
                self.active_tab -= 1;
            }
            return false;
        }

        if let Some((removed, runtime)) = self.tabs[tab_idx].close_pane(pane_id) {
            self.unregister_pane(removed);
            if let Some(runtime) = runtime {
                runtime.shutdown(removed);
            }
        }
        false
    }

    fn register_new_pane(&mut self, pane_id: PaneId) {
        self.public_pane_numbers
            .insert(pane_id, self.next_public_pane_number);
        self.next_public_pane_number += 1;
    }

    fn unregister_pane(&mut self, pane_id: PaneId) {
        if let Some(removed_number) = self.public_pane_numbers.remove(&pane_id) {
            for number in self.public_pane_numbers.values_mut() {
                if *number > removed_number {
                    *number -= 1;
                }
            }
            self.next_public_pane_number = self.public_pane_numbers.len() + 1;
        }
    }

    fn renumber_tabs(&mut self) {
        for (idx, tab) in self.tabs.iter_mut().enumerate() {
            tab.number = idx + 1;
        }
    }

    fn close_active_tab_and_report(&mut self) -> bool {
        if self.tabs.len() <= 1 {
            return true;
        }
        self.close_active_tab();
        false
    }
}

#[cfg(test)]
impl Workspace {
    pub(crate) fn test_new(name: &str) -> Self {
        let (events, _) = mpsc::channel(64);
        let render_notify = Arc::new(Notify::new());
        let render_dirty = Arc::new(AtomicBool::new(false));
        let identity_cwd = std::env::current_dir().unwrap_or_else(|_| "/".into());
        let (layout, root_id) = TileLayout::new();
        let mut panes = HashMap::new();
        panes.insert(root_id, PaneState::new());
        let mut pane_cwds = HashMap::new();
        pane_cwds.insert(root_id, identity_cwd.clone());
        let tab = Tab {
            custom_name: None,
            number: 1,
            root_pane: root_id,
            layout,
            panes,
            pane_cwds,
            runtimes: HashMap::new(),
            zoomed: false,
            events,
            render_notify,
            render_dirty,
        };
        let mut public_pane_numbers = HashMap::new();
        public_pane_numbers.insert(tab.root_pane, 1);
        Self {
            id: generate_workspace_id(),
            custom_name: Some(name.to_string()),
            identity_cwd: identity_cwd.clone(),
            cached_git_branch: git_branch(&identity_cwd),
            cached_git_ahead_behind: None,
            public_pane_numbers,
            next_public_pane_number: 2,
            tabs: vec![tab],
            active_tab: 0,
        }
    }

    pub(crate) fn test_split(&mut self, direction: Direction) -> PaneId {
        let tab = self.active_tab_mut().expect("workspace must have tab");
        let new_id = tab.layout.split_focused(direction);
        tab.panes.insert(new_id, PaneState::new());
        let cwd = std::env::current_dir().unwrap_or_else(|_| "/".into());
        tab.pane_cwds.insert(new_id, cwd);
        self.register_new_pane(new_id);
        new_id
    }

    pub(crate) fn test_add_tab(&mut self, name: Option<&str>) -> usize {
        let (events, _) = mpsc::channel(64);
        let render_notify = Arc::new(Notify::new());
        let render_dirty = Arc::new(AtomicBool::new(false));
        let (layout, root_id) = TileLayout::new();
        let mut panes = HashMap::new();
        panes.insert(root_id, PaneState::new());
        let cwd = std::env::current_dir().unwrap_or_else(|_| "/".into());
        let mut pane_cwds = HashMap::new();
        pane_cwds.insert(root_id, cwd);
        let tab = Tab {
            custom_name: name.map(str::to_string),
            number: self.tabs.len() + 1,
            root_pane: root_id,
            layout,
            panes,
            pane_cwds,
            runtimes: HashMap::new(),
            zoomed: false,
            events,
            render_notify,
            render_dirty,
        };
        self.register_new_pane(root_id);
        self.tabs.push(tab);
        self.tabs.len() - 1
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn workspace_identity_follows_first_tab_root_pane_cwd() {
        let mut ws = Workspace::test_new("ignored");
        ws.custom_name = None;
        let root_pane = ws.tabs[0].root_pane;
        ws.tabs[0]
            .pane_cwds
            .insert(root_pane, PathBuf::from("/tmp/pion"));

        assert_eq!(ws.display_name(), "pion");
        assert_eq!(ws.resolved_identity_cwd(), Some(PathBuf::from("/tmp/pion")));
    }

    #[test]
    fn moving_tab_keeps_active_identity_and_renumbers_auto_tabs() {
        let mut ws = Workspace::test_new("test");
        let moved_root = ws.tabs[0].root_pane;
        ws.test_add_tab(Some("foo"));
        let final_auto_idx = ws.test_add_tab(None);
        let active_root = ws.tabs[final_auto_idx].root_pane;
        ws.switch_tab(final_auto_idx);

        assert!(ws.move_tab(0, ws.tabs.len()));

        let labels: Vec<_> = ws.tabs.iter().map(|tab| tab.display_name()).collect();
        assert_eq!(labels, vec!["foo", "2", "3"]);
        assert_eq!(ws.tabs[0].custom_name.as_deref(), Some("foo"));
        assert!(ws.tabs[1].custom_name.is_none());
        assert!(ws.tabs[2].custom_name.is_none());
        assert_eq!(ws.tabs[2].root_pane, moved_root);
        assert_eq!(ws.tabs[ws.active_tab].root_pane, active_root);
    }
}