use std::{path::PathBuf, sync::Arc};

use async_trait::async_trait;
use chrono::Datelike;
use futures::stream::StreamExt;
use libertas_core::{
    authz,
    config::Config,
    error::{CoreError, CoreResult},
    models::Media,
    repositories::{AlbumShareRepository, MediaRepository, UserRepository},
    schema::{ListMediaOptions, UploadMediaData},
    services::MediaService,
};
use serde_json::json;
use sha2::{Digest, Sha256};
use tokio::{fs, io::AsyncWriteExt};
use uuid::Uuid;

pub struct MediaServiceImpl {
    repo: Arc<dyn MediaRepository>,
    user_repo: Arc<dyn UserRepository>,
    album_share_repo: Arc<dyn AlbumShareRepository>,
    config: Config,
    nats_client: async_nats::Client,
}

impl MediaServiceImpl {
    pub fn new(
        repo: Arc<dyn MediaRepository>,
        user_repo: Arc<dyn UserRepository>,
        album_share_repo: Arc<dyn AlbumShareRepository>,
        config: Config,
        nats_client: async_nats::Client,
    ) -> Self {
        Self {
            repo,
            user_repo,
            album_share_repo,
            config,
            nats_client,
        }
    }
}

#[async_trait]
impl MediaService for MediaServiceImpl {
    async fn upload_media(&self, mut data: UploadMediaData<'_>) -> CoreResult<Media> {
        let (file_bytes, hash, file_size) = self.hash_and_buffer_stream(&mut data).await?;

        let owner_id = data.owner_id;
        let filename = data.filename;
        let mime_type = data.mime_type;

        self.check_upload_prerequisites(owner_id, file_size, &hash)
            .await?;

        let storage_path = self.persist_media_file(&file_bytes, &filename).await?;

        let media = self
            .persist_media_metadata(owner_id, filename, mime_type, storage_path, hash, file_size)
            .await?;

        self.publish_new_media_job(media.id).await?;

        Ok(media)
    }

    async fn get_media_details(&self, id: Uuid, user_id: Uuid) -> CoreResult<Media> {
        let media = self
            .repo
            .find_by_id(id)
            .await?
            .ok_or(CoreError::NotFound("Media".to_string(), id))?;

        let user = self
            .user_repo
            .find_by_id(user_id)
            .await?
            .ok_or(CoreError::NotFound("User".to_string(), user_id))?;

        if authz::is_owner(user_id, &media) || authz::is_admin(&user) {
            return Ok(media);
        }

        let is_shared = self
            .album_share_repo
            .is_media_in_shared_album(id, user_id)
            .await?;

        if is_shared {
            return Ok(media);
        }

        Err(CoreError::Auth("Access denied".to_string()))
    }

    async fn list_user_media(&self, user_id: Uuid, options: ListMediaOptions) -> CoreResult<Vec<Media>> {
        self.repo.list_by_user(user_id, &options).await
    }

    async fn get_media_filepath(&self, id: Uuid, user_id: Uuid) -> CoreResult<String> {
        let media = self
            .repo
            .find_by_id(id)
            .await?
            .ok_or(CoreError::NotFound("Media".to_string(), id))?;

        let user = self
            .user_repo
            .find_by_id(user_id)
            .await?
            .ok_or(CoreError::NotFound("User".to_string(), user_id))?;

        if authz::is_owner(user_id, &media) || authz::is_admin(&user) {
            return Ok(media.storage_path);
        }

        let is_shared = self
            .album_share_repo
            .is_media_in_shared_album(id, user_id)
            .await?;

        if is_shared {
            return Ok(media.storage_path);
        }

        Err(CoreError::Auth("Access denied".to_string()))
    }

    async fn delete_media(&self, id: Uuid, user_id: Uuid) -> CoreResult<()> {
        let media = self
            .repo
            .find_by_id(id)
            .await?
            .ok_or(CoreError::NotFound("Media".to_string(), id))?;

        let user = self
            .user_repo
            .find_by_id(user_id)
            .await?
            .ok_or(CoreError::NotFound("User".to_string(), user_id))?;

        if !authz::is_owner(user_id, &media) && !authz::is_admin(&user) {
            return Err(CoreError::Auth("Access denied".to_string()));
        }

        let full_path = PathBuf::from(&self.config.media_library_path).join(&media.storage_path);
        self.repo.delete(id).await?;

        let file_size = match fs::metadata(&full_path).await {
            Ok(metadata) => metadata.len() as i64,
            Err(_) => 0,
        };

        if let Err(e) = fs::remove_file(full_path).await {
            tracing::error!("Failed to delete media file from disk: {}", e);
        }

        self.user_repo
            .update_storage_used(user.id, -file_size)
            .await?;

        let job_payload = json!({ "storage_path": media.storage_path });
        self.nats_client
            .publish("media.deleted".to_string(), job_payload.to_string().into())
            .await
            .map_err(|e| CoreError::Unknown(format!("Failed to publish NATS job: {}", e)))?;

        Ok(())
    }
}

impl MediaServiceImpl {
    async fn hash_and_buffer_stream(
        &self,
        stream: &mut UploadMediaData<'_>,
    ) -> CoreResult<(Vec<u8>, String, i64)> {
        let mut hasher = Sha256::new();
        let mut file_bytes = Vec::new();
        while let Some(chunk_result) = stream.stream.next().await {
            let chunk = chunk_result.map_err(|e| CoreError::Io(e))?;
            hasher.update(&chunk);
            file_bytes.extend_from_slice(&chunk);
        }
        let file_size = file_bytes.len() as i64;
        let hash = format!("{:x}", hasher.finalize());
        Ok((file_bytes, hash, file_size))
    }

    async fn check_upload_prerequisites(
        &self,
        user_id: Uuid,
        file_size: i64,
        hash: &str,
    ) -> CoreResult<()> {
        let user = self
            .user_repo
            .find_by_id(user_id)
            .await?
            .ok_or(CoreError::NotFound("User".to_string(), user_id))?;

        if user.storage_used + file_size > user.storage_quota {
            return Err(CoreError::Auth(format!(
                "Storage quota exceeded. Used: {}, Quota: {}",
                user.storage_used, user.storage_quota
            )));
        }

        if self.repo.find_by_hash(hash).await?.is_some() {
            return Err(CoreError::Duplicate(
                "A file with this content already exists".to_string(),
            ));
        }

        Ok(())
    }

    async fn persist_media_file(&self, file_bytes: &[u8], filename: &str) -> CoreResult<String> {
        let now = chrono::Utc::now();
        let year = now.year().to_string();
        let month = format!("{:02}", now.month());
        let mut dest_path = PathBuf::from(&self.config.media_library_path);
        dest_path.push(year.clone());
        dest_path.push(month.clone());

        fs::create_dir_all(&dest_path).await?;
        dest_path.push(filename);

        let storage_path_str = PathBuf::from(&year)
            .join(&month)
            .join(filename)
            .to_string_lossy()
            .to_string();

        let mut file = fs::File::create(&dest_path).await?;
        file.write_all(&file_bytes).await?;

        Ok(storage_path_str)
    }

    async fn persist_media_metadata(
        &self,
        owner_id: Uuid,
        filename: String,
        mime_type: String,
        storage_path: String,
        hash: String,
        file_size: i64,
    ) -> CoreResult<Media> {
        let media_model = Media {
            id: Uuid::new_v4(),
            owner_id,
            storage_path,
            original_filename: filename,
            mime_type,
            hash,
            created_at: chrono::Utc::now(),
            thumbnail_path: None,
        };

        self.repo.create(&media_model).await?;
        self.user_repo
            .update_storage_used(owner_id, file_size)
            .await?;

        Ok(media_model)
    }

    async fn publish_new_media_job(&self, media_id: Uuid) -> CoreResult<()> {
        let job_payload = json!({ "media_id": media_id });
        self.nats_client
            .publish("media.new".to_string(), job_payload.to_string().into())
            .await
            .map_err(|e| CoreError::Unknown(format!("Failed to publish NATS job: {}", e)))
    }
}