use std::cell::RefCell;
use std::collections::{HashMap, HashSet};
use std::rc::Rc;
use std::time::Duration;

use anyhow::{Error, anyhow};
use common::EventUtils;
use gpui::{App, AppContext, Context, Entity, Global, Task, Window};
use nostr_sdk::prelude::*;
use smallvec::{SmallVec, smallvec};
use state::{Announcement, BOOTSTRAP_RELAYS, NostrRegistry, TIMEOUT};

mod person;

pub use person::*;

pub fn init(window: &mut Window, cx: &mut App) {
    PersonRegistry::set_global(cx.new(|cx| PersonRegistry::new(window, cx)), cx);
}

struct GlobalPersonRegistry(Entity<PersonRegistry>);

impl Global for GlobalPersonRegistry {}

#[derive(Debug, Clone)]
enum Dispatch {
    Person(Box<Person>),
    Announcement(Box<Event>),
    Relays(Box<Event>),
}

/// Person Registry
#[derive(Debug)]
pub struct PersonRegistry {
    /// Collection of all persons (user profiles)
    persons: HashMap<PublicKey, Entity<Person>>,

    /// Set of public keys that have been seen
    seens: Rc<RefCell<HashSet<PublicKey>>>,

    /// Sender for requesting metadata
    sender: flume::Sender<PublicKey>,

    /// Tasks for asynchronous operations
    tasks: SmallVec<[Task<()>; 4]>,
}

impl PersonRegistry {
    /// Retrieve the global person registry
    pub fn global(cx: &App) -> Entity<Self> {
        cx.global::<GlobalPersonRegistry>().0.clone()
    }

    /// Set the global person registry instance
    fn set_global(state: Entity<Self>, cx: &mut App) {
        cx.set_global(GlobalPersonRegistry(state));
    }

    /// Create a new person registry instance
    fn new(window: &mut Window, cx: &mut Context<Self>) -> Self {
        let nostr = NostrRegistry::global(cx);
        let client = nostr.read(cx).client();

        // Channel for communication between nostr and gpui
        let (tx, rx) = flume::bounded::<Dispatch>(100);
        let (mta_tx, mta_rx) = flume::unbounded::<PublicKey>();

        let mut tasks = smallvec![];

        tasks.push(
            // Handle nostr notifications
            cx.background_spawn({
                let client = client.clone();

                async move {
                    Self::handle_notifications(&client, &tx).await;
                }
            }),
        );

        tasks.push(
            // Handle metadata requests
            cx.background_spawn({
                let client = client.clone();

                async move {
                    Self::handle_requests(&client, &mta_rx).await;
                }
            }),
        );

        tasks.push(
            // Update GPUI state
            cx.spawn(async move |this, cx| {
                while let Ok(event) = rx.recv_async().await {
                    this.update(cx, |this, cx| {
                        match event {
                            Dispatch::Person(person) => {
                                this.insert(*person, cx);
                            }
                            Dispatch::Announcement(event) => {
                                this.set_announcement(&event, cx);
                            }
                            Dispatch::Relays(event) => {
                                this.set_messaging_relays(&event, cx);
                            }
                        };
                    })
                    .ok();
                }
            }),
        );

        // Load all user profiles from the database
        cx.defer_in(window, |this, _window, cx| {
            this.load(cx);
        });

        Self {
            persons: HashMap::new(),
            seens: Rc::new(RefCell::new(HashSet::new())),
            sender: mta_tx,
            tasks,
        }
    }

    /// Handle nostr notifications
    async fn handle_notifications(client: &Client, tx: &flume::Sender<Dispatch>) {
        let mut notifications = client.notifications();
        let mut processed: HashSet<EventId> = HashSet::new();

        while let Some(notification) = notifications.next().await {
            let ClientNotification::Message { message, .. } = notification else {
                // Skip if the notification is not a message
                continue;
            };

            if let RelayMessage::Event { event, .. } = message {
                // Skip if the event has already been processed
                if !processed.insert(event.id) {
                    continue;
                }

                match event.kind {
                    Kind::Metadata => {
                        let metadata = Metadata::from_json(&event.content).unwrap_or_default();
                        let person = Person::new(event.pubkey, metadata);
                        let val = Box::new(person);
                        // Send
                        tx.send_async(Dispatch::Person(val)).await.ok();
                    }
                    Kind::ContactList => {
                        let public_keys = event.extract_public_keys();
                        // Get metadata for all public keys
                        get_metadata(client, public_keys).await.ok();
                    }
                    Kind::InboxRelays => {
                        let val = Box::new(event.into_owned());
                        // Send
                        tx.send_async(Dispatch::Relays(val)).await.ok();
                    }
                    Kind::Custom(10044) => {
                        let val = Box::new(event.into_owned());
                        // Send
                        tx.send_async(Dispatch::Announcement(val)).await.ok();
                    }
                    _ => {}
                }
            }
        }
    }

    /// Handle request for metadata
    async fn handle_requests(client: &Client, rx: &flume::Receiver<PublicKey>) {
        let mut batch: HashSet<PublicKey> = HashSet::new();

        loop {
            match flume::Selector::new()
                .recv(rx, |result| result.ok())
                .wait_timeout(Duration::from_secs(TIMEOUT))
            {
                Ok(Some(public_key)) => {
                    batch.insert(public_key);
                    // Process the batch if it's full
                    if batch.len() >= 20 {
                        get_metadata(client, std::mem::take(&mut batch)).await.ok();
                    }
                }
                _ => {
                    if !batch.is_empty() {
                        get_metadata(client, std::mem::take(&mut batch)).await.ok();
                    }
                }
            }
        }
    }

    /// Load all user profiles from the database
    fn load(&mut self, cx: &mut Context<Self>) {
        let nostr = NostrRegistry::global(cx);
        let client = nostr.read(cx).client();

        let task: Task<Result<Vec<Person>, Error>> = cx.background_spawn(async move {
            let filter = Filter::new().kind(Kind::Metadata).limit(200);
            let events = client.database().query(filter).await?;
            let persons = events
                .into_iter()
                .map(|event| {
                    let metadata = Metadata::from_json(event.content).unwrap_or_default();
                    Person::new(event.pubkey, metadata)
                })
                .collect();

            Ok(persons)
        });

        self.tasks.push(cx.spawn(async move |this, cx| {
            if let Ok(persons) = task.await {
                this.update(cx, |this, cx| {
                    this.bulk_inserts(persons, cx);
                })
                .ok();
            }
        }));
    }

    /// Set profile encryption keys announcement
    fn set_announcement(&mut self, event: &Event, cx: &mut App) {
        let announcement = Announcement::from(event);

        if let Some(person) = self.persons.get(&event.pubkey) {
            person.update(cx, |person, cx| {
                person.set_announcement(announcement);
                cx.notify();
            });
        } else {
            let person =
                Person::new(event.pubkey, Metadata::default()).with_announcement(announcement);
            self.insert(person, cx);
        }
    }

    /// Set messaging relays for a person
    fn set_messaging_relays(&mut self, event: &Event, cx: &mut App) {
        let urls: Vec<RelayUrl> = nip17::extract_relay_list(event).cloned().collect();

        if let Some(person) = self.persons.get(&event.pubkey) {
            person.update(cx, |person, cx| {
                person.set_messaging_relays(urls);
                cx.notify();
            });
        } else {
            let person = Person::new(event.pubkey, Metadata::default()).with_messaging_relays(urls);
            self.insert(person, cx);
        }
    }

    /// Insert batch of persons
    fn bulk_inserts(&mut self, persons: Vec<Person>, cx: &mut Context<Self>) {
        for person in persons.into_iter() {
            let public_key = person.public_key();
            self.persons
                .entry(public_key)
                .or_insert_with(|| cx.new(|_| person));
        }
        cx.notify();
    }

    /// Insert or update a person
    pub fn insert(&mut self, person: Person, cx: &mut App) {
        let public_key = person.public_key();

        match self.persons.get(&public_key) {
            Some(this) => {
                this.update(cx, |this, cx| {
                    this.set_metadata(person.metadata());
                    cx.notify();
                });
            }
            None => {
                self.persons.insert(public_key, cx.new(|_| person));
            }
        }
    }

    /// Get single person by public key
    pub fn get(&self, public_key: &PublicKey, cx: &App) -> Person {
        if let Some(person) = self.persons.get(public_key) {
            return person.read(cx).clone();
        }

        let public_key = *public_key;
        let mut seen = self.seens.borrow_mut();

        if seen.insert(public_key) {
            let sender = self.sender.clone();

            // Spawn background task to request metadata
            cx.background_spawn(async move {
                if let Err(e) = sender.send_async(public_key).await {
                    log::warn!("Failed to send public key for metadata request: {}", e);
                }
            })
            .detach();
        }

        // Return a temporary profile with default metadata
        Person::new(public_key, Metadata::default())
    }
}

/// Get metadata for all public keys in a event
async fn get_metadata<I>(client: &Client, public_keys: I) -> Result<(), Error>
where
    I: IntoIterator<Item = PublicKey>,
{
    let authors: Vec<PublicKey> = public_keys.into_iter().collect();
    let limit = authors.len();

    if authors.is_empty() {
        return Err(anyhow!("You need at least one public key"));
    }

    // Construct the subscription option
    let opts = SubscribeAutoCloseOptions::default()
        .exit_policy(ReqExitPolicy::ExitOnEOSE)
        .timeout(Some(Duration::from_secs(TIMEOUT)));

    // Construct the filter for metadata
    let filter = Filter::new()
        .kind(Kind::Metadata)
        .authors(authors)
        .limit(limit);

    // Construct target for subscription
    let target: HashMap<&str, Vec<Filter>> = BOOTSTRAP_RELAYS
        .into_iter()
        .map(|relay| (relay, vec![filter.clone()]))
        .collect();

    client.subscribe(target).close_on(opts).await?;

    Ok(())
}