use crate::domain::dto::reaction::ReactionGroupResponse;
use crate::domain::events::message::{MessageReactionAddedEvent, MessageReactionRemovedEvent};
use crate::http::error::HTTPError;
use crate::models::{emoji, message_reaction};
use crate::services::ServicesContext;
use event_bus::Scope;
use sea_orm::{ColumnTrait, EntityTrait, QueryFilter, Set};
use std::collections::HashMap;
use std::sync::Arc;
use std::time::Instant;
use uuid::Uuid;

#[derive(Debug, Clone)]
pub struct MessageReactionService {
    context: Arc<ServicesContext>,
}

impl MessageReactionService {
    pub fn new(context: Arc<ServicesContext>) -> Self {
        Self { context }
    }

    fn normalize_skin_tone(skin_tone: Option<u8>) -> Result<i32, HTTPError> {
        match skin_tone {
            None => Ok(0),
            Some(tone @ 1..=5) => Ok(tone as i32),
            Some(_) => Err(HTTPError::BadRequest(
                "skin_tone must be between 1 and 5".into(),
            )),
        }
    }

    async fn validate(
        &self,
        message_id: Uuid,
        emoji_id: Uuid,
        skin_tone: Option<u8>,
    ) -> Result<
        (
            crate::models::message::Model,
            emoji::Model,
            i32,
            Option<Uuid>,
        ),
        HTTPError,
    > {
        let message = self
            .context
            .repositories
            .message
            .get_by_id(message_id)
            .await?
            .ok_or(HTTPError::NotFound)?;
        let channel = self
            .context
            .repositories
            .channel
            .get_by_id(message.channel_id)
            .await?
            .ok_or(HTTPError::NotFound)?;
        let emoji = self
            .context
            .repositories
            .emoji
            .get_by_id(emoji_id)
            .await?
            .ok_or_else(|| HTTPError::BadRequest("Emoji not found".into()))?;

        if emoji.server_id.is_some() && emoji.server_id != channel.server_id {
            return Err(HTTPError::BadRequest(
                "Emoji is not available in this message scope".into(),
            ));
        }

        let normalized_tone = Self::normalize_skin_tone(skin_tone)?;
        if normalized_tone != 0 && (emoji.emoji_type != "unicode" || !emoji.supports_skin_tone) {
            return Err(HTTPError::BadRequest(
                "This emoji does not support skin tones".into(),
            ));
        }

        Ok((message, emoji, normalized_tone, channel.server_id))
    }

    pub async fn add(
        &self,
        message_id: Uuid,
        user_id: Uuid,
        emoji_id: Uuid,
        skin_tone: Option<u8>,
    ) -> Result<(message_reaction::Model, bool), HTTPError> {
        let started_at = Instant::now();
        let (message, _, skin_tone, server_id) =
            self.validate(message_id, emoji_id, skin_tone).await?;

        if let Some(existing) = self
            .context
            .repositories
            .message_reaction
            .find(message_id, user_id, emoji_id, skin_tone)
            .await?
        {
            return Ok((existing, false));
        }

        let reaction = self
            .context
            .repositories
            .message_reaction
            .create(message_reaction::ActiveModel {
                id: Set(Uuid::now_v7()),
                message_id: Set(message_id),
                user_id: Set(user_id),
                emoji_id: Set(emoji_id),
                skin_tone: Set(skin_tone),
                ..Default::default()
            })
            .await?;

        let mut scopes = vec![Scope::uuid("channel", message.channel_id)];
        if let Some(server_id) = server_id {
            scopes.push(Scope::uuid("server", server_id));
        }
        self.context.event_bus.emit_scoped(
            "message_reaction_added",
            scopes,
            MessageReactionAddedEvent {
                server_id,
                channel_id: message.channel_id,
                reaction: reaction.clone(),
            },
        );

        Ok((reaction, true))
    }

    pub async fn remove(
        &self,
        message_id: Uuid,
        user_id: Uuid,
        emoji_id: Uuid,
        skin_tone: Option<u8>,
    ) -> Result<message_reaction::Model, HTTPError> {
        let (message, _, skin_tone, server_id) =
            self.validate(message_id, emoji_id, skin_tone).await?;
        let reaction = self
            .context
            .repositories
            .message_reaction
            .delete(message_id, user_id, emoji_id, skin_tone)
            .await?
            .ok_or(HTTPError::NotFound)?;

        let mut scopes = vec![Scope::uuid("channel", message.channel_id)];
        if let Some(server_id) = server_id {
            scopes.push(Scope::uuid("server", server_id));
        }
        self.context.event_bus.emit_scoped(
            "message_reaction_removed",
            scopes,
            MessageReactionRemovedEvent {
                server_id,
                channel_id: message.channel_id,
                reaction: reaction.clone(),
            },
        );

        Ok(reaction)
    }

    pub async fn grouped_for_messages(
        &self,
        message_ids: &[Uuid],
    ) -> Result<HashMap<Uuid, Vec<ReactionGroupResponse>>, HTTPError> {
        let reactions = self
            .context
            .repositories
            .message_reaction
            .list_by_message_ids(message_ids)
            .await?;
        if reactions.is_empty() {
            return Ok(HashMap::new());
        }
        let emoji_ids: Vec<_> = reactions.iter().map(|reaction| reaction.emoji_id).collect();
        let emojis: HashMap<_, _> = emoji::Entity::find()
            .filter(emoji::Column::Id.is_in(emoji_ids))
            .all(&self.context.repositories.emoji.context.db)
            .await?
            .into_iter()
            .map(|emoji| (emoji.id, emoji))
            .collect();

        let mut grouped: HashMap<Uuid, HashMap<(Uuid, i32), ReactionGroupResponse>> =
            HashMap::new();
        for reaction in reactions {
            let Some(emoji) = emojis.get(&reaction.emoji_id) else {
                continue;
            };
            let groups = grouped.entry(reaction.message_id).or_default();
            let group = groups
                .entry((reaction.emoji_id, reaction.skin_tone))
                .or_insert_with(|| ReactionGroupResponse {
                    emoji_id: emoji.id,
                    name: emoji.name.clone(),
                    unicode_sequence: emoji.unicode_sequence.clone(),
                    asset_url: emoji
                        .file_path
                        .as_ref()
                        .map(|_| format!("/api/emojis/{}/asset", emoji.id)),
                    skin_tone: (reaction.skin_tone != 0).then_some(reaction.skin_tone as u8),
                    count: 0,
                    user_ids: Vec::new(),
                });
            group.count += 1;
            group.user_ids.push(reaction.user_id);
        }

        Ok(grouped
            .into_iter()
            .map(|(message_id, groups)| {
                let mut groups: Vec<_> = groups.into_values().collect();
                for group in &mut groups {
                    group.user_ids.sort_unstable();
                }
                groups.sort_by(|left, right| {
                    left.name
                        .cmp(&right.name)
                        .then(left.skin_tone.cmp(&right.skin_tone))
                });
                (message_id, groups)
            })
            .collect())
    }
}

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

    #[test]
    fn skin_tone_validation_accepts_only_the_supported_range() {
        assert_eq!(
            MessageReactionService::normalize_skin_tone(None).unwrap(),
            0
        );
        for tone in 1..=5 {
            assert_eq!(
                MessageReactionService::normalize_skin_tone(Some(tone)).unwrap(),
                tone as i32
            );
        }
        assert!(MessageReactionService::normalize_skin_tone(Some(0)).is_err());
        assert!(MessageReactionService::normalize_skin_tone(Some(6)).is_err());
    }
}