use std::cmp::Ordering;
use std::collections::{HashMap, HashSet};
use std::hash::{Hash, Hasher};
use std::time::Duration;

use account::Account;
use anyhow::{anyhow, Error};
use common::display::RenderedProfile;
use common::event::EventUtils;
use gpui::{App, AppContext, Context, EventEmitter, SharedString, SharedUri, Task};
use nostr_sdk::prelude::*;
use person::PersonRegistry;
use states::{app_state, SignerKind, SEND_RETRY};

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct SendOptions {
    pub backup: bool,
    pub signer_kind: SignerKind,
}

impl SendOptions {
    pub fn new() -> Self {
        Self {
            backup: true,
            signer_kind: SignerKind::default(),
        }
    }

    pub fn backup(&self) -> bool {
        self.backup
    }
}

impl Default for SendOptions {
    fn default() -> Self {
        Self::new()
    }
}

#[derive(Debug, Clone)]
pub struct SendReport {
    pub receiver: PublicKey,
    pub status: Option<Output<EventId>>,
    pub error: Option<SharedString>,
    pub on_hold: Option<Event>,
    pub encryption: bool,
    pub relays_not_found: bool,
    pub device_not_found: bool,
}

impl SendReport {
    pub fn new(receiver: PublicKey) -> Self {
        Self {
            receiver,
            status: None,
            error: None,
            on_hold: None,
            encryption: false,
            relays_not_found: false,
            device_not_found: false,
        }
    }

    pub fn status(mut self, output: Output<EventId>) -> Self {
        self.status = Some(output);
        self
    }

    pub fn error(mut self, error: impl Into<SharedString>) -> Self {
        self.error = Some(error.into());
        self
    }

    pub fn on_hold(mut self, event: Event) -> Self {
        self.on_hold = Some(event);
        self
    }

    pub fn encryption(mut self) -> Self {
        self.encryption = true;
        self
    }

    pub fn relays_not_found(mut self) -> Self {
        self.relays_not_found = true;
        self
    }

    pub fn device_not_found(mut self) -> Self {
        self.device_not_found = true;
        self
    }

    pub fn is_relay_error(&self) -> bool {
        self.error.is_some() || self.relays_not_found
    }

    pub fn is_sent_success(&self) -> bool {
        if let Some(output) = self.status.as_ref() {
            !output.success.is_empty()
        } else {
            false
        }
    }
}

#[derive(Debug, Clone)]
pub enum RoomSignal {
    NewMessage((EventId, UnsignedEvent)),
    Refresh,
}

#[derive(Clone, Copy, Hash, Debug, PartialEq, Eq, PartialOrd, Ord, Default)]
pub enum RoomKind {
    Ongoing,
    #[default]
    Request,
}

#[derive(Debug)]
pub struct Room {
    /// Conversation ID
    pub id: u64,
    /// The timestamp of the last message in the room
    pub created_at: Timestamp,
    /// Subject of the room
    pub subject: Option<SharedString>,
    /// All members of the room
    pub members: Vec<PublicKey>,
    /// Kind
    pub kind: RoomKind,
}

impl Ord for Room {
    fn cmp(&self, other: &Self) -> Ordering {
        self.created_at.cmp(&other.created_at)
    }
}

impl PartialOrd for Room {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl PartialEq for Room {
    fn eq(&self, other: &Self) -> bool {
        self.id == other.id
    }
}

impl Hash for Room {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.id.hash(state);
    }
}

impl Eq for Room {}

impl EventEmitter<RoomSignal> for Room {}

impl From<&Event> for Room {
    fn from(val: &Event) -> Self {
        let id = val.uniq_id();
        let created_at = val.created_at;

        // Get the members from the event's tags and event's pubkey
        let members = val.all_pubkeys();

        // Get subject from tags
        let subject = val
            .tags
            .find(TagKind::Subject)
            .and_then(|tag| tag.content().map(|s| s.to_owned().into()));

        Room {
            id,
            created_at,
            subject,
            members,
            kind: RoomKind::default(),
        }
    }
}

impl From<&UnsignedEvent> for Room {
    fn from(val: &UnsignedEvent) -> Self {
        let id = val.uniq_id();
        let created_at = val.created_at;

        // Get the members from the event's tags and event's pubkey
        let members = val.all_pubkeys();

        // Get subject from tags
        let subject = val
            .tags
            .find(TagKind::Subject)
            .and_then(|tag| tag.content().map(|s| s.to_owned().into()));

        Room {
            id,
            created_at,
            subject,
            members,
            kind: RoomKind::default(),
        }
    }
}

impl Room {
    /// Constructs a new room with the given receiver and tags.
    pub async fn new(subject: Option<String>, receivers: Vec<PublicKey>) -> Result<Self, Error> {
        let client = app_state().client();
        let signer = client.signer().await?;
        let public_key = signer.get_public_key().await?;

        if receivers.is_empty() {
            return Err(anyhow!("You need to add at least one receiver"));
        };

        // Convert receiver's public keys into tags
        let mut tags: Tags = Tags::from_list(
            receivers
                .iter()
                .map(|pubkey| Tag::public_key(pubkey.to_owned()))
                .collect(),
        );

        // Add subject if it is present
        if let Some(subject) = subject {
            tags.push(Tag::from_standardized_without_cell(TagStandard::Subject(
                subject,
            )));
        }

        let mut event = EventBuilder::new(Kind::PrivateDirectMessage, "")
            .tags(tags)
            .build(public_key);

        // Generate event ID
        event.ensure_id();

        Ok(Room::from(&event))
    }

    /// Sets the kind of the room and returns the modified room
    pub fn kind(mut self, kind: RoomKind) -> Self {
        self.kind = kind;
        self
    }

    /// Sets this room is ongoing conversation
    pub fn set_ongoing(&mut self, cx: &mut Context<Self>) {
        if self.kind != RoomKind::Ongoing {
            self.kind = RoomKind::Ongoing;
            cx.notify();
        }
    }

    /// Updates the creation timestamp of the room
    pub fn set_created_at(&mut self, created_at: impl Into<Timestamp>, cx: &mut Context<Self>) {
        self.created_at = created_at.into();
        cx.notify();
    }

    /// Updates the subject of the room
    pub fn set_subject<T>(&mut self, subject: T, cx: &mut Context<Self>)
    where
        T: Into<SharedString>,
    {
        self.subject = Some(subject.into());
        cx.notify();
    }

    /// Returns the members of the room
    pub fn members(&self) -> Vec<PublicKey> {
        self.members.clone()
    }

    /// Checks if the room has more than two members (group)
    pub fn is_group(&self) -> bool {
        self.members.len() > 2
    }

    /// Gets the display name for the room
    pub fn display_name(&self, cx: &App) -> SharedString {
        if let Some(value) = self.subject.clone() {
            value
        } else {
            self.merged_name(cx)
        }
    }

    /// Gets the display image for the room
    pub fn display_image(&self, proxy: bool, cx: &App) -> SharedUri {
        if !self.is_group() {
            self.display_member(cx).avatar(proxy)
        } else {
            SharedUri::from("brand/group.png")
        }
    }

    /// Get a member to represent the room
    ///
    /// Display member is always different from the current user.
    pub fn display_member(&self, cx: &App) -> Profile {
        let persons = PersonRegistry::global(cx);
        let account = Account::global(cx);
        let public_key = account.read(cx).public_key();

        let target_member = self
            .members
            .iter()
            .find(|&member| member != &public_key)
            .or_else(|| self.members.first())
            .expect("Room should have at least one member");

        persons.read(cx).get_person(target_member, cx)
    }

    /// Merge the names of the first two members of the room.
    fn merged_name(&self, cx: &App) -> SharedString {
        let persons = PersonRegistry::global(cx);

        if self.is_group() {
            let profiles: Vec<Profile> = self
                .members
                .iter()
                .map(|public_key| persons.read(cx).get_person(public_key, cx))
                .collect();

            let mut name = profiles
                .iter()
                .take(2)
                .map(|p| p.name())
                .collect::<Vec<_>>()
                .join(", ");

            if profiles.len() > 2 {
                name = format!("{}, +{}", name, profiles.len() - 2);
            }

            SharedString::from(name)
        } else {
            self.display_member(cx).display_name()
        }
    }

    /// Emits a new message signal to the current room
    pub fn emit_message(&self, id: EventId, event: UnsignedEvent, cx: &mut Context<Self>) {
        cx.emit(RoomSignal::NewMessage((id, event)));
    }

    /// Emits a signal to refresh the current room's messages.
    pub fn emit_refresh(&mut self, cx: &mut Context<Self>) {
        cx.emit(RoomSignal::Refresh);
    }

    /// Get messaging relays and encryption keys announcement for each member
    pub fn connect(&self, cx: &App) -> Task<Result<(), Error>> {
        let members = self.members();

        cx.background_spawn(async move {
            let client = app_state().client();
            let signer = client.signer().await?;
            let public_key = signer.get_public_key().await?;
            let opts = SubscribeAutoCloseOptions::default().exit_policy(ReqExitPolicy::ExitOnEOSE);

            for member in members.into_iter() {
                if member == public_key {
                    continue;
                };

                // Construct a filter for messaging relays
                let filter = Filter::new()
                    .kind(Kind::InboxRelays)
                    .author(member)
                    .limit(1);

                // Subscribe to get members messaging relays
                client.subscribe(filter, Some(opts)).await?;

                // Construct a filter for encryption keys announcement
                let filter = Filter::new()
                    .kind(Kind::Custom(10044))
                    .author(member)
                    .limit(1);

                // Subscribe to get members encryption keys announcement
                client.subscribe(filter, Some(opts)).await?;
            }

            Ok(())
        })
    }

    /// Get all messages belonging to the room
    pub fn get_messages(&self, cx: &App) -> Task<Result<Vec<UnsignedEvent>, Error>> {
        let conversation_id = self.id.to_string();

        cx.background_spawn(async move {
            let client = app_state().client();
            let filter = Filter::new()
                .kind(Kind::ApplicationSpecificData)
                .custom_tag(SingleLetterTag::lowercase(Alphabet::C), conversation_id);

            let stored = client.database().query(filter).await?;

            let mut messages: Vec<UnsignedEvent> = stored
                .into_iter()
                .filter_map(|event| UnsignedEvent::from_json(&event.content).ok())
                .collect();

            messages.sort_by_key(|message| message.created_at);

            Ok(messages)
        })
    }

    /// Create a new message event (unsigned)
    pub fn create_message(&self, content: &str, replies: &[EventId], cx: &App) -> UnsignedEvent {
        // Get the app state
        let state = app_state();
        let relay_cache = state.relay_cache.read_blocking();

        // Get current user
        let account = Account::global(cx);
        let public_key = account.read(cx).public_key();

        // Get room's subject
        let subject = self.subject.clone();

        let mut tags = vec![];

        // Add receivers
        //
        // NOTE: current user will be removed from the list of receivers
        for member in self.members.iter() {
            // Get relay hint if available
            let relay_url = relay_cache
                .get(member)
                .and_then(|urls| urls.iter().nth(0).cloned());

            // Construct a public key tag with relay hint
            let tag = TagStandard::PublicKey {
                public_key: member.to_owned(),
                relay_url,
                alias: None,
                uppercase: false,
            };

            tags.push(Tag::from_standardized_without_cell(tag));
        }

        // Add subject tag if it's present
        if let Some(value) = subject {
            tags.push(Tag::from_standardized_without_cell(TagStandard::Subject(
                value.to_string(),
            )));
        }

        // Add reply/quote tag
        if replies.len() == 1 {
            tags.push(Tag::event(replies[0]))
        } else {
            for id in replies {
                let tag = TagStandard::Quote {
                    event_id: id.to_owned(),
                    relay_url: None,
                    public_key: None,
                };
                tags.push(Tag::from_standardized_without_cell(tag))
            }
        }

        // Construct a direct message event
        //
        // WARNING: never send this event to relays
        let mut event = EventBuilder::new(Kind::PrivateDirectMessage, content)
            .tags(tags)
            .build(public_key);

        // Generate event ID
        event.ensure_id();

        event
    }

    /// Create a task to send a message to all room members
    pub fn send_message(
        &self,
        rumor: &UnsignedEvent,
        opts: &SendOptions,
        cx: &App,
    ) -> Task<Result<Vec<SendReport>, Error>> {
        let rumor = rumor.to_owned();
        let opts = opts.to_owned();

        // Get all members
        let mut members = self.members();

        cx.background_spawn(async move {
            let state = app_state();
            let client = state.client();
            let signer_kind = opts.signer_kind;

            let relay_cache = state.relay_cache.read().await;
            let announcement_cache = state.announcement_cache.read().await;

            let encryption = state.device.read().await.encryption.clone();
            // Get the encryption public key
            let encryption_pubkey = if let Some(signer) = encryption.as_ref() {
                signer.get_public_key().await.ok()
            } else {
                None
            };

            let user_signer = client.signer().await?;
            let user_pubkey = user_signer.get_public_key().await?;

            // Remove the current user's public key from the list of receivers
            // the current user will be handled separately
            members.retain(|&pk| pk != user_pubkey);

            // Determine the signer will be used based on the provided options
            let signer = Self::select_signer(&opts.signer_kind, user_signer, encryption)?;

            // Collect the send reports
            let mut reports: Vec<SendReport> = vec![];

            for member in members.into_iter() {
                // Get user's messaging relays
                let urls = relay_cache.get(&member).cloned().unwrap_or_default();

                // Check if there are any relays to send the message to
                if urls.is_empty() {
                    reports.push(SendReport::new(member).relays_not_found());
                    continue;
                }

                // Get user's encryption public key if available
                let encryption = announcement_cache
                    .get(&member)
                    .and_then(|a| a.to_owned().map(|a| a.public_key()));

                // Skip sending if using encryption signer but receiver's encryption keys not found
                if encryption.is_none() && matches!(signer_kind, SignerKind::Encryption) {
                    reports.push(SendReport::new(member).device_not_found());
                    continue;
                }

                let receiver = Self::select_receiver(&signer_kind, member, encryption)?;
                let rumor = rumor.clone();
                let tags = vec![Tag::public_key(member)];

                // Construct the gift wrap event
                let event = EventBuilder::gift_wrap(&signer, &receiver, rumor, tags).await?;

                // Send the gift wrap event to the messaging relays
                match client.send_event_to(urls, &event).await {
                    Ok(output) => {
                        let id = output.id().to_owned();
                        let auth = output.failed.iter().any(|(_, s)| s.starts_with("auth-"));
                        let report = SendReport::new(receiver).status(output);

                        if auth {
                            // Wait for authenticated and resent event successfully
                            for attempt in 0..=SEND_RETRY {
                                let retry_manager = state.tracker().read().await;
                                let ids = retry_manager.resent_ids();

                                // Check if event was successfully resent
                                if let Some(output) = ids.iter().find(|e| e.id() == &id).cloned() {
                                    let output = SendReport::new(receiver).status(output);
                                    reports.push(output);
                                    break;
                                }

                                // Check if retry limit exceeded
                                if attempt == SEND_RETRY {
                                    reports.push(report);
                                    break;
                                }

                                smol::Timer::after(Duration::from_millis(1200)).await;
                            }
                        } else {
                            reports.push(report);
                        }
                    }
                    Err(e) => {
                        reports.push(SendReport::new(receiver).error(e.to_string()));
                    }
                }
            }

            let receiver = Self::select_receiver(&signer_kind, user_pubkey, encryption_pubkey)?;
            let rumor = rumor.clone();
            let tags = vec![Tag::public_key(user_pubkey)];

            // Construct the gift-wrapped event
            let event = EventBuilder::gift_wrap(&signer, &receiver, rumor, tags).await?;

            // Only send a backup message to current user if sent successfully to others
            if opts.backup() && reports.iter().all(|r| r.is_sent_success()) {
                let urls = relay_cache.get(&user_pubkey).cloned().unwrap_or_default();

                // Check if there are any relays to send the event to
                if urls.is_empty() {
                    reports.push(SendReport::new(user_pubkey).relays_not_found());
                } else {
                    // Send the event to the messaging relays
                    match client.send_event_to(urls, &event).await {
                        Ok(output) => {
                            reports.push(SendReport::new(user_pubkey).status(output));
                        }
                        Err(e) => {
                            reports.push(SendReport::new(user_pubkey).error(e.to_string()));
                        }
                    }
                }
            } else {
                reports.push(SendReport::new(user_pubkey).on_hold(event));
            }

            Ok(reports)
        })
    }

    /// Create a task to resend a failed message
    pub fn resend_message(
        &self,
        reports: Vec<SendReport>,
        cx: &App,
    ) -> Task<Result<Vec<SendReport>, Error>> {
        cx.background_spawn(async move {
            let states = app_state();
            let client = states.client();
            let mut resend_reports = vec![];

            for report in reports.into_iter() {
                let receiver = report.receiver;

                // Process failed events
                if let Some(output) = report.status {
                    let id = output.id();
                    let urls: Vec<&RelayUrl> = output.failed.keys().collect();

                    if let Some(event) = client.database().event_by_id(id).await? {
                        for url in urls.into_iter() {
                            let relay = client.pool().relay(url).await?;
                            let id = relay.send_event(&event).await?;

                            let resent: Output<EventId> = Output {
                                val: id,
                                success: HashSet::from([url.to_owned()]),
                                failed: HashMap::new(),
                            };

                            resend_reports.push(SendReport::new(receiver).status(resent));
                        }
                    }
                }

                // Process the on hold event if it exists
                if let Some(event) = report.on_hold {
                    let urls = states.messaging_relays(receiver).await;

                    // Check if there are any relays to send the event to
                    if urls.is_empty() {
                        resend_reports.push(SendReport::new(receiver).relays_not_found());
                    } else {
                        // Send the event to the messaging relays
                        match client.send_event_to(urls, &event).await {
                            Ok(output) => {
                                resend_reports.push(SendReport::new(receiver).status(output));
                            }
                            Err(e) => {
                                resend_reports.push(SendReport::new(receiver).error(e.to_string()));
                            }
                        }
                    }
                }
            }

            Ok(resend_reports)
        })
    }

    fn select_signer<T>(kind: &SignerKind, user: T, encryption: Option<T>) -> Result<T, Error>
    where
        T: NostrSigner,
    {
        match kind {
            SignerKind::Encryption => {
                Ok(encryption.ok_or_else(|| anyhow!("No encryption key found"))?)
            }
            SignerKind::User => Ok(user),
            SignerKind::Auto => Ok(encryption.unwrap_or(user)),
        }
    }

    fn select_receiver(
        kind: &SignerKind,
        user: PublicKey,
        encryption: Option<PublicKey>,
    ) -> Result<PublicKey, Error> {
        match kind {
            SignerKind::Encryption => {
                Ok(encryption.ok_or_else(|| anyhow!("Receiver's encryption key not found"))?)
            }
            SignerKind::User => Ok(user),
            SignerKind::Auto => Ok(encryption.unwrap_or(user)),
        }
    }
}