//! What the API needs to answer a request: one HTTP client and the addresses
//! of the three upstreams the service cannot work without (DESIGN.md §3).

use std::sync::Arc;
use std::time::Duration;

use arr_db::Db;
use tokio::sync::mpsc;

/// The TMDB API root. Not a bootstrap setting (DESIGN.md §10) — only the key
/// is configurable, so this is a constant that tests point elsewhere.
pub const DEFAULT_TMDB_URL: &str = "https://api.themoviedb.org/3";

/// How long an upstream has to answer a probe before it counts as
/// unreachable. Health is polled by a human waiting on a page.
const PROBE_TIMEOUT: Duration = Duration::from_secs(3);

/// Where the upstreams live, and the keys for the two that need one.
#[derive(Debug, Clone)]
pub struct Upstreams {
    pub prowlarr_url: String,
    pub prowlarr_api_key: Option<String>,
    pub transmission_url: String,
    pub tmdb_url: String,
    pub tmdb_api_key: Option<String>,
}

impl Upstreams {
    /// Every upstream at its documented default, no keys.
    #[must_use]
    pub fn new(prowlarr_url: String, transmission_url: String) -> Self {
        Self {
            prowlarr_url,
            prowlarr_api_key: None,
            transmission_url,
            tmdb_url: DEFAULT_TMDB_URL.to_string(),
            tmdb_api_key: None,
        }
    }

    /// Set the Prowlarr API key.
    #[must_use]
    pub fn with_prowlarr_api_key(mut self, key: Option<String>) -> Self {
        self.prowlarr_api_key = key;
        self
    }

    /// Set the TMDB API key.
    #[must_use]
    pub fn with_tmdb_api_key(mut self, key: Option<String>) -> Self {
        self.tmdb_api_key = key;
        self
    }

    /// Point TMDB somewhere other than the real API. Tests and the
    /// `ARR_TMDB_URL` e2e seam only.
    #[must_use]
    pub fn with_tmdb_url(mut self, url: String) -> Self {
        self.tmdb_url = url;
        self
    }
}

/// Shared handler state. Cheap to clone: the client pools internally and the
/// upstream addresses are behind an [`Arc`].
#[derive(Debug, Clone)]
pub struct AppState {
    http: reqwest::Client,
    upstreams: Arc<Upstreams>,
    database: Option<Db>,
    movie_commands: mpsc::Sender<MovieCommand>,
    pending_movie_commands: Arc<tokio::sync::Mutex<mpsc::Receiver<MovieCommand>>>,
    episode_commands: mpsc::Sender<EpisodeCommand>,
    pending_episode_commands: Arc<tokio::sync::Mutex<mpsc::Receiver<EpisodeCommand>>>,
    season_commands: mpsc::Sender<SeasonCommand>,
    pending_season_commands: Arc<tokio::sync::Mutex<mpsc::Receiver<SeasonCommand>>>,
    metadata_commands: mpsc::Sender<MetadataCommand>,
    pending_metadata_commands: Arc<tokio::sync::Mutex<mpsc::Receiver<MetadataCommand>>>,
}

/// Work explicitly requested through the movie API.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MovieCommand {
    Search { movie_id: i64 },
    Grab { movie_id: i64, release_id: i64 },
}

/// Work explicitly requested through the series API.
///
/// Intent lives at the leaf (`DESIGN.md` §4.1), so a manual action names an
/// episode even when the release that satisfies it is a season pack.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EpisodeCommand {
    Search { episode_id: i64 },
    Grab { episode_id: i64, release_id: i64 },
}

/// Work explicitly requested through the season deck API (issue #125).
///
/// A season pack is one torrent for the whole season and the grab targets
/// `target_kind = 'season'`, so the manual action names a season — unlike
/// [`EpisodeCommand`], where intent lives at the leaf.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SeasonCommand {
    Search { season_id: i64 },
    Grab { season_id: i64, release_id: i64 },
}

/// A title whose TMDB metadata should be refreshed now rather than on the
/// daily lane's next tick (issue #176).
///
/// Sent when a title is added: a new series has no seasons at all until a
/// refresh reveals them, and a new movie has no digital release date, so
/// waiting up to a day is the difference between a usable page and an empty
/// one. Unlike the other three commands this is not an operator action, so a
/// full channel is dropped rather than reported — the scheduled sweep still
/// owns the title, because a title that was never refreshed keeps
/// `metadata_refreshed_at` NULL.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MetadataCommand {
    Series { series_id: i64 },
    Movie { movie_id: i64 },
}

impl AppState {
    /// Build the state, including the shared HTTP client.
    ///
    /// # Errors
    ///
    /// If the TLS backend cannot be initialised.
    pub fn new(upstreams: Upstreams) -> Result<Self, reqwest::Error> {
        let http = reqwest::Client::builder().timeout(PROBE_TIMEOUT).build()?;
        let (movie_commands, pending_movie_commands) = mpsc::channel(64);
        let (episode_commands, pending_episode_commands) = mpsc::channel(64);
        let (season_commands, pending_season_commands) = mpsc::channel(64);
        let (metadata_commands, pending_metadata_commands) = mpsc::channel(64);
        Ok(Self {
            http,
            upstreams: Arc::new(upstreams),
            database: None,
            movie_commands,
            pending_movie_commands: Arc::new(tokio::sync::Mutex::new(pending_movie_commands)),
            episode_commands,
            pending_episode_commands: Arc::new(tokio::sync::Mutex::new(pending_episode_commands)),
            season_commands,
            pending_season_commands: Arc::new(tokio::sync::Mutex::new(pending_season_commands)),
            metadata_commands,
            pending_metadata_commands: Arc::new(tokio::sync::Mutex::new(pending_metadata_commands)),
        })
    }

    /// Attach the migrated application database.
    #[must_use]
    pub fn with_database(mut self, database: Db) -> Self {
        self.database = Some(database);
        self
    }

    /// Wait for the next manual movie action in the daemon's reconcile loop.
    ///
    /// # Errors
    ///
    /// If every sender has been dropped.
    pub async fn next_movie_command(&self) -> Option<MovieCommand> {
        self.pending_movie_commands.lock().await.recv().await
    }

    /// Wait for the next manual episode action in the daemon's reconcile loop.
    ///
    /// # Errors
    ///
    /// If every sender has been dropped.
    pub async fn next_episode_command(&self) -> Option<EpisodeCommand> {
        self.pending_episode_commands.lock().await.recv().await
    }

    /// Wait for the next manual season action in the daemon's reconcile loop.
    ///
    /// # Errors
    ///
    /// If every sender has been dropped.
    pub async fn next_season_command(&self) -> Option<SeasonCommand> {
        self.pending_season_commands.lock().await.recv().await
    }

    /// Wait for the next on-demand metadata refresh in the daemon's metadata
    /// lane.
    ///
    /// # Errors
    ///
    /// If every sender has been dropped.
    pub async fn next_metadata_command(&self) -> Option<MetadataCommand> {
        self.pending_metadata_commands.lock().await.recv().await
    }

    pub(crate) fn http(&self) -> &reqwest::Client {
        &self.http
    }

    pub(crate) fn upstreams(&self) -> &Upstreams {
        &self.upstreams
    }

    pub(crate) fn database(&self) -> Option<&Db> {
        self.database.as_ref()
    }

    pub(crate) fn send_movie_command(
        &self,
        command: MovieCommand,
    ) -> Result<(), mpsc::error::TrySendError<MovieCommand>> {
        self.movie_commands.try_send(command)
    }

    pub(crate) fn send_episode_command(
        &self,
        command: EpisodeCommand,
    ) -> Result<(), mpsc::error::TrySendError<EpisodeCommand>> {
        self.episode_commands.try_send(command)
    }

    pub(crate) fn send_season_command(
        &self,
        command: SeasonCommand,
    ) -> Result<(), mpsc::error::TrySendError<SeasonCommand>> {
        self.season_commands.try_send(command)
    }

    /// Ask the metadata lane to refresh one title now. Best effort by
    /// design: an add must not fail because the channel is full or because
    /// nothing is draining it, so the caller logs and carries on.
    pub(crate) fn send_metadata_command(
        &self,
        command: MetadataCommand,
    ) -> Result<(), mpsc::error::TrySendError<MetadataCommand>> {
        self.metadata_commands.try_send(command)
    }
}