use crate::app::{get_unknown_note_ids, UnknownId};
use crate::error::Error;
use crate::note::NoteRef;
use crate::notecache::CachedNote;
use crate::{Damus, Result};

use crate::route::Route;

use egui_virtual_list::VirtualList;
use enostr::Filter;
use nostrdb::{Note, Subscription, Transaction};
use std::cell::RefCell;
use std::collections::HashSet;
use std::rc::Rc;

use tracing::debug;

#[derive(Debug, Copy, Clone)]
pub enum TimelineSource<'a> {
    Column { ind: usize },
    Thread(&'a [u8; 32]),
}

impl<'a> TimelineSource<'a> {
    pub fn column(ind: usize) -> Self {
        TimelineSource::Column { ind }
    }

    pub fn view<'b>(
        self,
        app: &'b mut Damus,
        txn: &Transaction,
        filter: ViewFilter,
    ) -> &'b mut TimelineTab {
        match self {
            TimelineSource::Column { ind, .. } => app.timelines[ind].view_mut(filter),
            TimelineSource::Thread(root_id) => {
                // TODO: replace all this with the raw entry api eventually

                let thread = if app.threads.root_id_to_thread.contains_key(root_id) {
                    app.threads.thread_expected_mut(root_id)
                } else {
                    app.threads.thread_mut(&app.ndb, txn, root_id).get_ptr()
                };

                &mut thread.view
            }
        }
    }

    pub fn sub<'b>(self, app: &'b mut Damus, txn: &Transaction) -> Option<&'b Subscription> {
        match self {
            TimelineSource::Column { ind, .. } => app.timelines[ind].subscription.as_ref(),
            TimelineSource::Thread(root_id) => {
                // TODO: replace all this with the raw entry api eventually

                let thread = if app.threads.root_id_to_thread.contains_key(root_id) {
                    app.threads.thread_expected_mut(root_id)
                } else {
                    app.threads.thread_mut(&app.ndb, txn, root_id).get_ptr()
                };

                thread.subscription()
            }
        }
    }

    pub fn poll_notes_into_view(
        &self,
        app: &mut Damus,
        txn: &'a Transaction,
        ids: &mut HashSet<UnknownId<'a>>,
    ) -> Result<()> {
        let sub_id = if let Some(sub_id) = self.sub(app, txn).map(|s| s.id) {
            sub_id
        } else {
            return Err(Error::no_active_sub());
        };

        //
        // TODO(BUG!): poll for these before the txn, otherwise we can hit
        // a race condition where we hit the "no note??" expect below. This may
        // require some refactoring due to the missing ids logic
        //
        let new_note_ids = app.ndb.poll_for_notes(sub_id, 100);
        if new_note_ids.is_empty() {
            return Ok(());
        } else {
            debug!("{} new notes! {:?}", new_note_ids.len(), new_note_ids);
        }

        let new_refs: Vec<(Note, NoteRef)> = new_note_ids
            .iter()
            .map(|key| {
                let note = app.ndb.get_note_by_key(txn, *key).expect("no note??");
                let cached_note = app
                    .note_cache_mut()
                    .cached_note_or_insert(*key, &note)
                    .clone();
                let _ = get_unknown_note_ids(&app.ndb, &cached_note, txn, &note, *key, ids);

                let created_at = note.created_at();
                (
                    note,
                    NoteRef {
                        key: *key,
                        created_at,
                    },
                )
            })
            .collect();

        // ViewFilter::NotesAndReplies
        {
            let refs: Vec<NoteRef> = new_refs.iter().map(|(_note, nr)| *nr).collect();

            self.view(app, txn, ViewFilter::NotesAndReplies)
                .insert(&refs);
        }

        //
        // handle the filtered case (ViewFilter::Notes, no replies)
        //
        // TODO(jb55): this is mostly just copied from above, let's just use a loop
        //             I initially tried this but ran into borrow checker issues
        {
            let mut filtered_refs = Vec::with_capacity(new_refs.len());
            for (note, nr) in &new_refs {
                let cached_note = app.note_cache_mut().cached_note_or_insert(nr.key, note);

                if ViewFilter::filter_notes(cached_note, note) {
                    filtered_refs.push(*nr);
                }
            }

            self.view(app, txn, ViewFilter::Notes)
                .insert(&filtered_refs);
        }

        Ok(())
    }
}

#[derive(Copy, Clone, Eq, PartialEq, Debug, Default)]
pub enum ViewFilter {
    Notes,

    #[default]
    NotesAndReplies,
}

impl ViewFilter {
    pub fn name(&self) -> &'static str {
        match self {
            ViewFilter::Notes => "Notes",
            ViewFilter::NotesAndReplies => "Notes & Replies",
        }
    }

    pub fn index(&self) -> usize {
        match self {
            ViewFilter::Notes => 0,
            ViewFilter::NotesAndReplies => 1,
        }
    }

    pub fn filter_notes(cache: &CachedNote, note: &Note) -> bool {
        !cache.reply.borrow(note.tags()).is_reply()
    }

    fn identity(_cache: &CachedNote, _note: &Note) -> bool {
        true
    }

    pub fn filter(&self) -> fn(&CachedNote, &Note) -> bool {
        match self {
            ViewFilter::Notes => ViewFilter::filter_notes,
            ViewFilter::NotesAndReplies => ViewFilter::identity,
        }
    }
}

/// A timeline view is a filtered view of notes in a timeline. Two standard views
/// are "Notes" and "Notes & Replies". A timeline is associated with a Filter,
/// but a TimelineTab is a further filtered view of this Filter that can't
/// be captured by a Filter itself.
#[derive(Default)]
pub struct TimelineTab {
    pub notes: Vec<NoteRef>,
    pub selection: i32,
    pub filter: ViewFilter,
    pub list: Rc<RefCell<VirtualList>>,
}

impl TimelineTab {
    pub fn new(filter: ViewFilter) -> Self {
        TimelineTab::new_with_capacity(filter, 1000)
    }

    pub fn new_with_capacity(filter: ViewFilter, cap: usize) -> Self {
        let selection = 0i32;
        let mut list = VirtualList::new();
        list.hide_on_resize(None);
        let list = Rc::new(RefCell::new(list));
        let notes: Vec<NoteRef> = Vec::with_capacity(cap);

        TimelineTab {
            notes,
            selection,
            filter,
            list,
        }
    }

    pub fn insert(&mut self, new_refs: &[NoteRef]) {
        if new_refs.is_empty() {
            return;
        }
        let num_prev_items = self.notes.len();
        let (notes, merge_kind) = crate::timeline::merge_sorted_vecs(&self.notes, new_refs);

        self.notes = notes;
        let new_items = self.notes.len() - num_prev_items;

        // TODO: technically items could have been added inbetween
        if new_items > 0 {
            let mut list = self.list.borrow_mut();

            match merge_kind {
                // TODO: update egui_virtual_list to support spliced inserts
                MergeKind::Spliced => list.reset(),
                MergeKind::FrontInsert => list.items_inserted_at_start(new_items),
            }
        }
    }

    pub fn select_down(&mut self) {
        debug!("select_down {}", self.selection + 1);
        if self.selection + 1 > self.notes.len() as i32 {
            return;
        }

        self.selection += 1;
    }

    pub fn select_up(&mut self) {
        debug!("select_up {}", self.selection - 1);
        if self.selection - 1 < 0 {
            return;
        }

        self.selection -= 1;
    }
}

pub struct Timeline {
    pub filter: Vec<Filter>,
    pub views: Vec<TimelineTab>,
    pub selected_view: i32,
    pub routes: Vec<Route>,
    pub navigating: bool,
    pub returning: bool,

    /// Our nostrdb subscription
    pub subscription: Option<Subscription>,
}

impl Timeline {
    pub fn new(filter: Vec<Filter>) -> Self {
        let subscription: Option<Subscription> = None;
        let notes = TimelineTab::new(ViewFilter::Notes);
        let replies = TimelineTab::new(ViewFilter::NotesAndReplies);
        let views = vec![notes, replies];
        let selected_view = 0;
        let routes = vec![Route::Timeline("Timeline".to_string())];
        let navigating = false;
        let returning = false;

        Timeline {
            navigating,
            returning,
            filter,
            views,
            subscription,
            selected_view,
            routes,
        }
    }

    pub fn current_view(&self) -> &TimelineTab {
        &self.views[self.selected_view as usize]
    }

    pub fn current_view_mut(&mut self) -> &mut TimelineTab {
        &mut self.views[self.selected_view as usize]
    }

    pub fn notes(&self, view: ViewFilter) -> &[NoteRef] {
        &self.views[view.index()].notes
    }

    pub fn view(&self, view: ViewFilter) -> &TimelineTab {
        &self.views[view.index()]
    }

    pub fn view_mut(&mut self, view: ViewFilter) -> &mut TimelineTab {
        &mut self.views[view.index()]
    }
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum MergeKind {
    FrontInsert,
    Spliced,
}

pub fn merge_sorted_vecs<T: Ord + Copy>(vec1: &[T], vec2: &[T]) -> (Vec<T>, MergeKind) {
    let mut merged = Vec::with_capacity(vec1.len() + vec2.len());
    let mut i = 0;
    let mut j = 0;
    let mut result: Option<MergeKind> = None;

    while i < vec1.len() && j < vec2.len() {
        if vec1[i] <= vec2[j] {
            if result.is_none() && j < vec2.len() {
                // if we're pushing from our large list and still have
                // some left in vec2, then this is a splice
                result = Some(MergeKind::Spliced);
            }
            merged.push(vec1[i]);
            i += 1;
        } else {
            merged.push(vec2[j]);
            j += 1;
        }
    }

    // Append any remaining elements from either vector
    if i < vec1.len() {
        merged.extend_from_slice(&vec1[i..]);
    }
    if j < vec2.len() {
        merged.extend_from_slice(&vec2[j..]);
    }

    (merged, result.unwrap_or(MergeKind::FrontInsert))
}