use axum::Json;
use axum::extract::{Extension, Path, State};
use uuid::Uuid;

use crate::auth::resolve_user_id;
use crate::dto::*;
use crate::error::ApiError;
use crate::state::AppState;

use pinakes_core::model::MediaId;
use pinakes_core::playlists::Playlist;
use pinakes_core::users::UserId;

/// Check whether a user has access to a playlist.
///
/// * `require_write` – when `true` only the playlist owner is allowed (for
///   mutations such as update, delete, add/remove/reorder items).  When `false`
///   the playlist must either be public or owned by the requesting user.
async fn check_playlist_access(
    storage: &pinakes_core::storage::DynStorageBackend,
    playlist_id: Uuid,
    user_id: UserId,
    require_write: bool,
) -> Result<Playlist, ApiError> {
    let playlist = storage.get_playlist(playlist_id).await.map_err(ApiError)?;
    if require_write {
        // Write operations require ownership
        if playlist.owner_id != user_id {
            return Err(ApiError(pinakes_core::error::PinakesError::Authorization(
                "only the playlist owner can modify this playlist".into(),
            )));
        }
    } else {
        // Read operations: allow if public or owner
        if !playlist.is_public && playlist.owner_id != user_id {
            return Err(ApiError(pinakes_core::error::PinakesError::Authorization(
                "playlist is private".into(),
            )));
        }
    }
    Ok(playlist)
}

pub async fn create_playlist(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Json(req): Json<CreatePlaylistRequest>,
) -> Result<Json<PlaylistResponse>, ApiError> {
    if req.name.is_empty() || req.name.chars().count() > 255 {
        return Err(ApiError(
            pinakes_core::error::PinakesError::InvalidOperation(
                "playlist name must be 1-255 characters".into(),
            ),
        ));
    }
    let owner_id = resolve_user_id(&state.storage, &username).await?;
    let playlist = state
        .storage
        .create_playlist(
            owner_id,
            &req.name,
            req.description.as_deref(),
            req.is_public.unwrap_or(false),
            req.is_smart.unwrap_or(false),
            req.filter_query.as_deref(),
        )
        .await?;
    Ok(Json(PlaylistResponse::from(playlist)))
}

pub async fn list_playlists(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
) -> Result<Json<Vec<PlaylistResponse>>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    // Fetch all playlists and filter to only public ones plus the user's own
    let playlists = state.storage.list_playlists(None).await?;
    let visible: Vec<PlaylistResponse> = playlists
        .into_iter()
        .filter(|p| p.is_public || p.owner_id == user_id)
        .map(PlaylistResponse::from)
        .collect();
    Ok(Json(visible))
}

pub async fn get_playlist(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
) -> Result<Json<PlaylistResponse>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    let playlist = check_playlist_access(&state.storage, id, user_id, false).await?;
    Ok(Json(PlaylistResponse::from(playlist)))
}

pub async fn update_playlist(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
    Json(req): Json<UpdatePlaylistRequest>,
) -> Result<Json<PlaylistResponse>, ApiError> {
    if let Some(ref name) = req.name
        && (name.is_empty() || name.chars().count() > 255)
    {
        return Err(ApiError(
            pinakes_core::error::PinakesError::InvalidOperation(
                "playlist name must be 1-255 characters".into(),
            ),
        ));
    }
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, true).await?;
    let playlist = state
        .storage
        .update_playlist(
            id,
            req.name.as_deref(),
            req.description.as_deref(),
            req.is_public,
        )
        .await?;
    Ok(Json(PlaylistResponse::from(playlist)))
}

pub async fn delete_playlist(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, true).await?;
    state.storage.delete_playlist(id).await?;
    Ok(Json(serde_json::json!({"deleted": true})))
}

pub async fn add_item(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
    Json(req): Json<PlaylistItemRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, true).await?;
    let position = match req.position {
        Some(p) => p,
        None => {
            let items = state.storage.get_playlist_items(id).await?;
            items.len() as i32
        }
    };
    state
        .storage
        .add_to_playlist(id, MediaId(req.media_id), position)
        .await?;
    Ok(Json(serde_json::json!({"added": true})))
}

pub async fn remove_item(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path((id, media_id)): Path<(Uuid, Uuid)>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, true).await?;
    state
        .storage
        .remove_from_playlist(id, MediaId(media_id))
        .await?;
    Ok(Json(serde_json::json!({"removed": true})))
}

pub async fn list_items(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
) -> Result<Json<Vec<MediaResponse>>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, false).await?;
    let items = state.storage.get_playlist_items(id).await?;
    Ok(Json(items.into_iter().map(MediaResponse::from).collect()))
}

pub async fn reorder_item(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
    Json(req): Json<ReorderPlaylistRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, true).await?;
    state
        .storage
        .reorder_playlist(id, MediaId(req.media_id), req.new_position)
        .await?;
    Ok(Json(serde_json::json!({"reordered": true})))
}

pub async fn shuffle_playlist(
    State(state): State<AppState>,
    Extension(username): Extension<String>,
    Path(id): Path<Uuid>,
) -> Result<Json<Vec<MediaResponse>>, ApiError> {
    let user_id = resolve_user_id(&state.storage, &username).await?;
    check_playlist_access(&state.storage, id, user_id, false).await?;
    use rand::seq::SliceRandom;
    let mut items = state.storage.get_playlist_items(id).await?;
    items.shuffle(&mut rand::rng());
    Ok(Json(items.into_iter().map(MediaResponse::from).collect()))
}