mod data;
pub(super) mod migrations;
mod preview;
mod remote;
mod tests;
mod thumbnail;

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

use async_trait::async_trait;
use base64::{engine::general_purpose, Engine as _};
use conduit::{
	debug, debug_error, debug_info, debug_warn, err, error, trace,
	utils::{self, MutexMap},
	warn, Err, Result, Server,
};
use ruma::{http_headers::ContentDisposition, Mxc, OwnedMxcUri, UserId};
use tokio::{
	fs,
	io::{AsyncReadExt, AsyncWriteExt, BufReader},
};

use self::data::{Data, Metadata};
pub use self::thumbnail::Dim;
use crate::{client, globals, sending, Dep};

#[derive(Debug)]
pub struct FileMeta {
	pub content: Option<Vec<u8>>,
	pub content_type: Option<String>,
	pub content_disposition: Option<ContentDisposition>,
}

pub struct Service {
	url_preview_mutex: MutexMap<String, ()>,
	pub(super) db: Data,
	services: Services,
}

struct Services {
	server: Arc<Server>,
	client: Dep<client::Service>,
	globals: Dep<globals::Service>,
	sending: Dep<sending::Service>,
}

/// generated MXC ID (`media-id`) length
pub const MXC_LENGTH: usize = 32;

/// Cache control for immutable objects.
pub const CACHE_CONTROL_IMMUTABLE: &str = "public,max-age=31536000,immutable";

/// Default cross-origin resource policy.
pub const CORP_CROSS_ORIGIN: &str = "cross-origin";

#[async_trait]
impl crate::Service for Service {
	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
		Ok(Arc::new(Self {
			url_preview_mutex: MutexMap::new(),
			db: Data::new(args.db),
			services: Services {
				server: args.server.clone(),
				client: args.depend::<client::Service>("client"),
				globals: args.depend::<globals::Service>("globals"),
				sending: args.depend::<sending::Service>("sending"),
			},
		}))
	}

	async fn worker(self: Arc<Self>) -> Result<()> {
		self.create_media_dir().await?;

		Ok(())
	}

	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
}

impl Service {
	/// Uploads a file.
	pub async fn create(
		&self, mxc: &Mxc<'_>, user: Option<&UserId>, content_disposition: Option<&ContentDisposition>,
		content_type: Option<&str>, file: &[u8],
	) -> Result<()> {
		// Width, Height = 0 if it's not a thumbnail
		let key = self
			.db
			.create_file_metadata(mxc, user, &Dim::default(), content_disposition, content_type)?;

		//TODO: Dangling metadata in database if creation fails
		let mut f = self.create_media_file(&key).await?;
		f.write_all(file).await?;

		Ok(())
	}

	/// Deletes a file in the database and from the media directory via an MXC
	pub async fn delete(&self, mxc: &Mxc<'_>) -> Result<()> {
		if let Ok(keys) = self.db.search_mxc_metadata_prefix(mxc) {
			for key in keys {
				trace!(?mxc, "MXC Key: {key:?}");
				debug_info!(?mxc, "Deleting from filesystem");

				if let Err(e) = self.remove_media_file(&key).await {
					debug_error!(?mxc, "Failed to remove media file: {e}");
				}

				debug_info!(?mxc, "Deleting from database");
				_ = self.db.delete_file_mxc(mxc);
			}

			Ok(())
		} else {
			Err!(Database(error!("Failed to find any media keys for MXC {mxc} in our database.")))
		}
	}

	/// Deletes all media by the specified user
	///
	/// currently, this is only practical for local users
	pub async fn delete_from_user(&self, user: &UserId) -> Result<usize> {
		let mxcs = self.db.get_all_user_mxcs(user);
		let mut deletion_count: usize = 0;

		for mxc in mxcs {
			let Ok(mxc) = mxc.as_str().try_into().inspect_err(|e| {
				debug_error!(?mxc, "Failed to parse MXC URI from database: {e}");
			}) else {
				continue;
			};

			debug_info!(%deletion_count, "Deleting MXC {mxc} by user {user} from database and filesystem");
			match self.delete(&mxc).await {
				Ok(()) => {
					deletion_count = deletion_count.saturating_add(1);
				},
				Err(e) => {
					debug_error!(%deletion_count, "Failed to delete {mxc} from user {user}, ignoring error: {e}");
				},
			}
		}

		Ok(deletion_count)
	}

	/// Downloads a file.
	pub async fn get(&self, mxc: &Mxc<'_>) -> Result<Option<FileMeta>> {
		if let Ok(Metadata {
			content_disposition,
			content_type,
			key,
		}) = self.db.search_file_metadata(mxc, &Dim::default())
		{
			let mut content = Vec::new();
			let path = self.get_media_file(&key);
			BufReader::new(fs::File::open(path).await?)
				.read_to_end(&mut content)
				.await?;

			Ok(Some(FileMeta {
				content: Some(content),
				content_type,
				content_disposition,
			}))
		} else {
			Ok(None)
		}
	}

	/// Gets all the MXC URIs in our media database
	pub async fn get_all_mxcs(&self) -> Result<Vec<OwnedMxcUri>> {
		let all_keys = self.db.get_all_media_keys();

		let mut mxcs = Vec::with_capacity(all_keys.len());

		for key in all_keys {
			trace!("Full MXC key from database: {key:?}");

			let mut parts = key.split(|&b| b == 0xFF);
			let mxc = parts
				.next()
				.map(|bytes| {
					utils::string_from_bytes(bytes)
						.map_err(|e| err!(Database(error!("Failed to parse MXC unicode bytes from our database: {e}"))))
				})
				.transpose()?;

			let Some(mxc_s) = mxc else {
				debug_warn!(?mxc, "Parsed MXC URL unicode bytes from database but is still invalid");
				continue;
			};

			trace!("Parsed MXC key to URL: {mxc_s}");
			let mxc = OwnedMxcUri::from(mxc_s);

			if mxc.is_valid() {
				mxcs.push(mxc);
			} else {
				debug_warn!("{mxc:?} from database was found to not be valid");
			}
		}

		Ok(mxcs)
	}

	/// Deletes all remote only media files in the given at or after
	/// time/duration. Returns a usize with the amount of media files deleted.
	pub async fn delete_all_remote_media_at_after_time(
		&self, time: SystemTime, before: bool, after: bool, yes_i_want_to_delete_local_media: bool,
	) -> Result<usize> {
		let all_keys = self.db.get_all_media_keys();
		let mut remote_mxcs = Vec::with_capacity(all_keys.len());

		for key in all_keys {
			trace!("Full MXC key from database: {key:?}");
			let mut parts = key.split(|&b| b == 0xFF);
			let mxc = parts
				.next()
				.map(|bytes| {
					utils::string_from_bytes(bytes)
						.map_err(|e| err!(Database(error!("Failed to parse MXC unicode bytes from our database: {e}"))))
				})
				.transpose()?;

			let Some(mxc_s) = mxc else {
				debug_warn!(?mxc, "Parsed MXC URL unicode bytes from database but is still invalid");
				continue;
			};

			trace!("Parsed MXC key to URL: {mxc_s}");
			let mxc = OwnedMxcUri::from(mxc_s);
			if (mxc.server_name() == Ok(self.services.globals.server_name()) && !yes_i_want_to_delete_local_media)
				|| !mxc.is_valid()
			{
				debug!("Ignoring local or broken media MXC: {mxc}");
				continue;
			}

			let path = self.get_media_file(&key);

			let file_metadata = match fs::metadata(path.clone()).await {
				Ok(file_metadata) => file_metadata,
				Err(e) => {
					error!("Failed to obtain file metadata for MXC {mxc} at file path \"{path:?}\", skipping: {e}");
					continue;
				},
			};

			trace!(%mxc, ?path, "File metadata: {file_metadata:?}");

			let file_created_at = match file_metadata.created() {
				Ok(value) => value,
				Err(err) if err.kind() == std::io::ErrorKind::Unsupported => {
					debug!("btime is unsupported, using mtime instead");
					file_metadata.modified()?
				},
				Err(err) => {
					error!("Could not delete MXC {mxc} at path {path:?}: {err:?}. Skipping...");
					continue;
				},
			};

			debug!("File created at: {file_created_at:?}");

			if file_created_at >= time && before {
				debug!("File is within (before) user duration, pushing to list of file paths and keys to delete.");
				remote_mxcs.push(mxc.to_string());
			} else if file_created_at <= time && after {
				debug!("File is not within (after) user duration, pushing to list of file paths and keys to delete.");
				remote_mxcs.push(mxc.to_string());
			}
		}

		if remote_mxcs.is_empty() {
			return Err!(Database("Did not found any eligible MXCs to delete."));
		}

		debug_info!("Deleting media now in the past {time:?}");

		let mut deletion_count: usize = 0;

		for mxc in remote_mxcs {
			let Ok(mxc) = mxc.as_str().try_into() else {
				debug_warn!("Invalid MXC in database, skipping");
				continue;
			};

			debug_info!("Deleting MXC {mxc} from database and filesystem");

			match self.delete(&mxc).await {
				Ok(()) => {
					deletion_count = deletion_count.saturating_add(1);
				},
				Err(e) => {
					warn!("Failed to delete {mxc}, ignoring error and skipping: {e}");
					continue;
				},
			}
		}

		Ok(deletion_count)
	}

	pub async fn create_media_dir(&self) -> Result<()> {
		let dir = self.get_media_dir();
		Ok(fs::create_dir_all(dir).await?)
	}

	async fn remove_media_file(&self, key: &[u8]) -> Result<()> {
		let path = self.get_media_file(key);
		let legacy = self.get_media_file_b64(key);
		debug!(?key, ?path, ?legacy, "Removing media file");

		let file_rm = fs::remove_file(&path);
		let legacy_rm = fs::remove_file(&legacy);
		let (file_rm, legacy_rm) = tokio::join!(file_rm, legacy_rm);
		if let Err(e) = legacy_rm {
			if self.services.server.config.media_compat_file_link {
				debug_error!(?key, ?legacy, "Failed to remove legacy media symlink: {e}");
			}
		}

		Ok(file_rm?)
	}

	async fn create_media_file(&self, key: &[u8]) -> Result<fs::File> {
		let path = self.get_media_file(key);
		debug!(?key, ?path, "Creating media file");

		let file = fs::File::create(&path).await?;
		if self.services.server.config.media_compat_file_link {
			let legacy = self.get_media_file_b64(key);
			if let Err(e) = fs::symlink(&path, &legacy).await {
				debug_error!(
					key = ?encode_key(key), ?path, ?legacy,
					"Failed to create legacy media symlink: {e}"
				);
			}
		}

		Ok(file)
	}

	#[inline]
	pub fn get_metadata(&self, mxc: &Mxc<'_>) -> Option<FileMeta> {
		self.db
			.search_file_metadata(mxc, &Dim::default())
			.map(|metadata| FileMeta {
				content_disposition: metadata.content_disposition,
				content_type: metadata.content_type,
				content: None,
			})
			.ok()
	}

	#[inline]
	#[must_use]
	pub fn get_media_file(&self, key: &[u8]) -> PathBuf { self.get_media_file_sha256(key) }

	/// new SHA256 file name media function. requires database migrated. uses
	/// SHA256 hash of the base64 key as the file name
	#[must_use]
	pub fn get_media_file_sha256(&self, key: &[u8]) -> PathBuf {
		let mut r = self.get_media_dir();
		// Using the hash of the base64 key as the filename
		// This is to prevent the total length of the path from exceeding the maximum
		// length in most filesystems
		let digest = <sha2::Sha256 as sha2::Digest>::digest(key);
		let encoded = encode_key(&digest);
		r.push(encoded);
		r
	}

	/// old base64 file name media function
	/// This is the old version of `get_media_file` that uses the full base64
	/// key as the filename.
	#[must_use]
	pub fn get_media_file_b64(&self, key: &[u8]) -> PathBuf {
		let mut r = self.get_media_dir();
		let encoded = encode_key(key);
		r.push(encoded);
		r
	}

	#[must_use]
	pub fn get_media_dir(&self) -> PathBuf {
		let mut r = PathBuf::new();
		r.push(self.services.server.config.database_path.clone());
		r.push("media");
		r
	}
}

#[inline]
#[must_use]
pub fn encode_key(key: &[u8]) -> String { general_purpose::URL_SAFE_NO_PAD.encode(key) }