#![warn(missing_docs)]
use std::borrow::Cow;

use async_trait::async_trait;

mod file;
pub use crate::database::file::FileStorage;
use crate::micropub::MicropubUpdate;
#[cfg(test)]
mod memory;
#[cfg(test)]
pub use crate::database::memory::MemoryStorage;

pub use kittybox_util::MicropubChannel;

use self::settings::Setting;

/// Enum representing different errors that might occur during the database query.
#[derive(Debug, Clone, Copy)]
pub enum ErrorKind {
    /// Backend error (e.g. database connection error)
    Backend,
    /// Error due to insufficient contextual permissions for the query
    PermissionDenied,
    /// Error due to the database being unable to parse JSON returned from the backing storage.
    /// Usually indicative of someone fiddling with the database manually instead of using proper tools.
    JsonParsing,
    ///  - ErrorKind::NotFound - equivalent to a 404 error. Note, some requests return an Option,
    ///    in which case None is also equivalent to a 404.
    NotFound,
    /// The user's query or request to the database was malformed. Used whenever the database processes
    /// the user's query directly, such as when editing posts inside of the database (e.g. Redis backend)
    BadRequest,
    /// the user's query collided with an in-flight request and needs to be retried
    Conflict,
    ///  - ErrorKind::Other - when something so weird happens that it becomes undescribable.
    Other,
}

/// Settings that can be stored in the database.
pub mod settings {
    mod private {
        pub trait Sealed {}
    }

    /// A trait for various settings that should be contained here.
    ///
    /// **Note**: this trait is sealed to prevent external
    /// implementations, as it wouldn't make sense to add new settings
    /// that aren't used by Kittybox itself.
    pub trait Setting<'de>: private::Sealed + std::fmt::Debug + Default + Clone + serde::Serialize + serde::de::DeserializeOwned + /*From<Settings> +*/ Send + Sync {
        type Data: std::fmt::Debug + Send + Sync;
        const ID: &'static str;

        /// Unwrap the setting type, returning owned data contained within.
        fn into_inner(self) -> Self::Data;
        /// Create a new instance of this type containing certain data.
        fn new(data: Self::Data) -> Self;
    }

    /// A website's title, shown in the header.
    #[derive(Debug, serde::Deserialize, serde::Serialize, Clone, PartialEq, Eq)]
    pub struct SiteName(String);
    impl Default for SiteName {
        fn default() -> Self {
            Self("Kittybox".to_string())
        }
    }
    impl AsRef<str> for SiteName {
        fn as_ref(&self) -> &str {
            self.0.as_str()
        }
    }
    impl private::Sealed for SiteName {}
    impl Setting<'_> for SiteName {
        type Data = String;
        const ID: &'static str = "site_name";

        fn into_inner(self) -> String {
            self.0
        }
        fn new(data: Self::Data) -> Self {
            Self(data)
        }
    }
    impl SiteName {
        fn from_str(data: &str) -> Self {
            Self(data.to_owned())
        }
    }

    /// Participation status in the IndieWeb Webring: https://🕸💍.ws/dashboard
    #[derive(Debug, Default, serde::Deserialize, serde::Serialize, Clone, Copy, PartialEq, Eq)]
    pub struct Webring(bool);
    impl private::Sealed for Webring {}
    impl Setting<'_> for Webring {
        type Data = bool;
        const ID: &'static str = "webring";

        fn into_inner(self) -> Self::Data {
            self.0
        }

        fn new(data: Self::Data) -> Self {
            Self(data)
        }
    }
}

/// Error signalled from the database.
#[derive(Debug)]
pub struct StorageError {
    msg: std::borrow::Cow<'static, str>,
    source: Option<Box<dyn std::error::Error + Send + Sync>>,
    kind: ErrorKind,
}

impl std::error::Error for StorageError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.source
            .as_ref()
            .map(|e| e.as_ref() as &dyn std::error::Error)
    }
}
impl From<serde_json::Error> for StorageError {
    fn from(err: serde_json::Error) -> Self {
        Self {
            msg: std::borrow::Cow::Owned(format!("{}", err)),
            source: Some(Box::new(err)),
            kind: ErrorKind::JsonParsing,
        }
    }
}
impl std::fmt::Display for StorageError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}: {}",
            match self.kind {
                ErrorKind::Backend => "backend error",
                ErrorKind::JsonParsing => "JSON parsing error",
                ErrorKind::PermissionDenied => "permission denied",
                ErrorKind::NotFound => "not found",
                ErrorKind::BadRequest => "bad request",
                ErrorKind::Conflict => "conflict with an in-flight request or existing data",
                ErrorKind::Other => "generic storage layer error",
            },
            self.msg
        )
    }
}
impl serde::Serialize for StorageError {
    fn serialize<S: serde::Serializer>(
        &self,
        serializer: S,
    ) -> std::result::Result<S::Ok, S::Error> {
        serializer.serialize_str(&self.to_string())
    }
}
impl StorageError {
    /// Create a new StorageError of an ErrorKind with a message.
    pub fn new(kind: ErrorKind, msg: String) -> Self {
        Self {
            msg: Cow::Owned(msg),
            source: None,
            kind,
        }
    }
    /// Create a new StorageError of an ErrorKind with a message from
    /// a static string.
    ///
    /// This saves an allocation for a new string and is the preferred
    /// way in case the error message doesn't change.
    pub fn from_static(kind: ErrorKind, msg: &'static str) -> Self {
        Self {
            msg: Cow::Borrowed(msg),
            source: None,
            kind
        }
    }
    /// Create a StorageError using another arbitrary Error as a source.
    pub fn with_source(
        kind: ErrorKind,
        msg: std::borrow::Cow<'static, str>,
        source: Box<dyn std::error::Error + Send + Sync>,
    ) -> Self {
        Self {
            msg,
            source: Some(source),
            kind,
        }
    }
    /// Get the kind of an error.
    pub fn kind(&self) -> ErrorKind {
        self.kind
    }
    /// Get the message as a string slice.
    pub fn msg(&self) -> &str {
        &self.msg
    }
}

/// A special Result type for the Micropub backing storage.
pub type Result<T> = std::result::Result<T, StorageError>;

/// A storage backend for the Micropub server.
///
/// Implementations should note that all methods listed on this trait MUST be fully atomic
/// or lock the database so that write conflicts or reading half-written data should not occur.
#[async_trait]
pub trait Storage: std::fmt::Debug + Clone + Send + Sync {
    /// Check if a post exists in the database.
    async fn post_exists(&self, url: &str) -> Result<bool>;

    /// Load a post from the database in MF2-JSON format, deserialized from JSON.
    async fn get_post(&self, url: &str) -> Result<Option<serde_json::Value>>;

    /// Save a post to the database as an MF2-JSON structure.
    ///
    /// Note that the `post` object MUST have `post["properties"]["uid"][0]` defined.
    async fn put_post(&self, post: &'_ serde_json::Value, user: &'_ str) -> Result<()>;

    /// Add post to feed. Some database implementations might have optimized ways to do this.
    #[tracing::instrument(skip(self))]
    async fn add_to_feed(&self, feed: &'_ str, post: &'_ str) -> Result<()> {
        tracing::debug!("Inserting {} into {} using `update_post`", post, feed);
        self.update_post(feed, serde_json::from_value(
            serde_json::json!({"add": {"children": [post]}})).unwrap()
        ).await
    }
    /// Remove post from feed. Some database implementations might have optimized ways to do this.
    #[tracing::instrument(skip(self))]
    async fn remove_from_feed(&self, feed: &'_ str, post: &'_ str) -> Result<()> {
        tracing::debug!("Removing {} into {} using `update_post`", post, feed);
        self.update_post(feed, serde_json::from_value(
            serde_json::json!({"delete": {"children": [post]}})).unwrap()
        ).await
    }

    /// Modify a post using an update object as defined in the
    /// Micropub spec.
    ///
    /// Note to implementors: the update operation MUST be atomic and
    /// SHOULD lock the database to prevent two clients overwriting
    /// each other's changes or simply corrupting something. Rejecting
    /// is allowed in case of concurrent updates if waiting for a lock
    /// cannot be done.
    async fn update_post(&self, url: &str, update: MicropubUpdate) -> Result<()>;

    /// Get a list of channels available for the user represented by
    /// the `user` domain to write to.
    async fn get_channels(&self, user: &'_ str) -> Result<Vec<MicropubChannel>>;

    /// Fetch a feed at `url` and return a an h-feed object containing
    /// `limit` posts after a post by url `after`, filtering the content
    /// in context of a user specified by `user` (or an anonymous user).
    ///
    /// This method MUST hydrate the `author` property with an h-card
    /// from the database by replacing URLs with corresponding h-cards.
    ///
    /// When encountering posts which the `user` is not authorized to
    /// access, this method MUST elide such posts (as an optimization
    /// for the frontend) and not return them, but still return up to
    /// `limit` posts (to not reveal the hidden posts' presence).
    ///
    /// Note for implementors: if you use streams to fetch posts in
    /// parallel from the database, preferably make this method use a
    /// connection pool to reduce overhead of creating a database
    /// connection per post for parallel fetching.
    async fn read_feed_with_limit(
        &self,
        url: &'_ str,
        after: &'_ Option<String>,
        limit: usize,
        user: &'_ Option<String>,
    ) -> Result<Option<serde_json::Value>>;

    async fn read_feed_with_cursor(
        &self,
        url: &'_ str,
        cursor: Option<&'_ str>,
        limit: usize,
        user: Option<&'_ str>
    ) -> Result<Option<(serde_json::Value, Option<String>)>>;

    /// Deletes a post from the database irreversibly. Must be idempotent.
    async fn delete_post(&self, url: &'_ str) -> Result<()>;

    /// Gets a setting from the setting store and passes the result.
    async fn get_setting<S: Setting<'a>, 'a>(&'_ self, user: &'_ str) -> Result<S>;

    /// Commits a setting to the setting store.
    async fn set_setting<S: Setting<'a> + 'a, 'a>(&self, user: &'a str, value: S::Data) -> Result<()>;
}

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

    use super::{MicropubChannel, Storage};
    use serde_json::json;

    async fn test_basic_operations<Backend: Storage>(backend: Backend) {
        let post: serde_json::Value = json!({
            "type": ["h-entry"],
            "properties": {
                "content": ["Test content"],
                "author": ["https://fireburn.ru/"],
                "uid": ["https://fireburn.ru/posts/hello"],
                "url": ["https://fireburn.ru/posts/hello", "https://fireburn.ru/posts/test"]
            }
        });
        let key = post["properties"]["uid"][0].as_str().unwrap().to_string();
        let alt_url = post["properties"]["url"][1].as_str().unwrap().to_string();

        // Reading and writing
        backend
            .put_post(&post, "fireburn.ru")
            .await
            .unwrap();
        if let Some(returned_post) = backend.get_post(&key).await.unwrap() {
            assert!(returned_post.is_object());
            assert_eq!(
                returned_post["type"].as_array().unwrap().len(),
                post["type"].as_array().unwrap().len()
            );
            assert_eq!(
                returned_post["type"].as_array().unwrap(),
                post["type"].as_array().unwrap()
            );
            let props: &serde_json::Map<String, serde_json::Value> =
                post["properties"].as_object().unwrap();
            for key in props.keys() {
                assert_eq!(
                    returned_post["properties"][key].as_array().unwrap(),
                    post["properties"][key].as_array().unwrap()
                )
            }
        } else {
            panic!("For some reason the backend did not return the post.")
        }
        // Check the alternative URL - it should return the same post
        if let Ok(Some(returned_post)) = backend.get_post(&alt_url).await {
            assert!(returned_post.is_object());
            assert_eq!(
                returned_post["type"].as_array().unwrap().len(),
                post["type"].as_array().unwrap().len()
            );
            assert_eq!(
                returned_post["type"].as_array().unwrap(),
                post["type"].as_array().unwrap()
            );
            let props: &serde_json::Map<String, serde_json::Value> =
                post["properties"].as_object().unwrap();
            for key in props.keys() {
                assert_eq!(
                    returned_post["properties"][key].as_array().unwrap(),
                    post["properties"][key].as_array().unwrap()
                )
            }
        } else {
            panic!("For some reason the backend did not return the post.")
        }
    }

    /// Note: this is merely a smoke check and is in no way comprehensive.
    // TODO updates for feeds must update children using special logic
    async fn test_update<Backend: Storage>(backend: Backend) {
        let post: serde_json::Value = json!({
            "type": ["h-entry"],
            "properties": {
                "content": ["Test content"],
                "author": ["https://fireburn.ru/"],
                "uid": ["https://fireburn.ru/posts/hello"],
                "url": ["https://fireburn.ru/posts/hello", "https://fireburn.ru/posts/test"]
            }
        });
        let key = post["properties"]["uid"][0].as_str().unwrap().to_string();

        // Reading and writing
        backend
            .put_post(&post, "fireburn.ru")
            .await
            .unwrap();

        backend
            .update_post(
                &key,
                serde_json::from_value(json!({
                    "url": &key,
                    "add": {
                        "category": ["testing"],
                    },
                    "replace": {
                        "content": ["Different test content"]
                    }
                })).unwrap(),
            )
            .await
            .unwrap();

        match backend.get_post(&key).await {
            Ok(Some(returned_post)) => {
                assert!(returned_post.is_object());
                assert_eq!(
                    returned_post["type"].as_array().unwrap().len(),
                    post["type"].as_array().unwrap().len()
                );
                assert_eq!(
                    returned_post["type"].as_array().unwrap(),
                    post["type"].as_array().unwrap()
                );
                assert_eq!(
                    returned_post["properties"]["content"][0].as_str().unwrap(),
                    "Different test content"
                );
                assert_eq!(
                    returned_post["properties"]["category"].as_array().unwrap(),
                    &vec![json!("testing")]
                );
            }
            something_else => {
                something_else
                    .expect("Shouldn't error")
                    .expect("Should have the post");
            }
        }
    }

    async fn test_get_channel_list<Backend: Storage>(backend: Backend) {
        let feed = json!({
            "type": ["h-feed"],
            "properties": {
                "name": ["Main Page"],
                "author": ["https://fireburn.ru/"],
                "uid": ["https://fireburn.ru/feeds/main"]
            },
            "children": []
        });
        backend
            .put_post(&feed, "fireburn.ru")
            .await
            .unwrap();
        let chans = backend.get_channels("fireburn.ru").await.unwrap();
        assert_eq!(chans.len(), 1);
        assert_eq!(
            chans[0],
            MicropubChannel {
                uid: "https://fireburn.ru/feeds/main".to_string(),
                name: "Main Page".to_string()
            }
        );
    }

    async fn test_settings<Backend: Storage>(backend: Backend) {
        backend
            .set_setting::<settings::SiteName>(
                "https://fireburn.ru/",
                "Vika's Hideout".to_owned()
            )
            .await
            .unwrap();
        assert_eq!(
            backend
            .get_setting::<settings::SiteName>("https://fireburn.ru/")
            .await
            .unwrap()
            .as_ref(),
            "Vika's Hideout"
        );
    }

    fn gen_random_post(domain: &str) -> serde_json::Value {
        use faker_rand::lorem::{Paragraphs, Word};

        let uid = format!(
            "https://{domain}/posts/{}-{}-{}",
            rand::random::<Word>(),
            rand::random::<Word>(),
            rand::random::<Word>()
        );

        let time = chrono::Local::now().to_rfc3339();
        let post = json!({
            "type": ["h-entry"],
            "properties": {
                "content": [rand::random::<Paragraphs>().to_string()],
                "uid": [&uid],
                "url": [&uid],
                "published": [&time]
            }
        });

        post
    }

    async fn test_feed_pagination<Backend: Storage>(backend: Backend) {
        let posts = {
            let mut posts = std::iter::from_fn(
                || Some(gen_random_post("fireburn.ru"))
            )
            .take(40)
            .collect::<Vec<serde_json::Value>>();

            // Reverse the array so it's in reverse-chronological order
            posts.reverse();

            posts
        };

        let feed = json!({
            "type": ["h-feed"],
            "properties": {
                "name": ["Main Page"],
                "author": ["https://fireburn.ru/"],
                "uid": ["https://fireburn.ru/feeds/main"]
            },
        });
        let key = feed["properties"]["uid"][0].as_str().unwrap();

        backend
            .put_post(&feed, "fireburn.ru")
            .await
            .unwrap();

        for (i, post) in posts.iter().rev().enumerate() {
            backend
                .put_post(post, "fireburn.ru")
                .await
                .unwrap();
            backend.add_to_feed(key, post["properties"]["uid"][0].as_str().unwrap()).await.unwrap();
        }

        let limit: usize = 10;

        tracing::debug!("Starting feed reading...");
        let (result, cursor) = backend
            .read_feed_with_cursor(key, None, limit, None)
            .await
            .unwrap()
            .unwrap();

        assert_eq!(result["children"].as_array().unwrap().len(), limit);
        assert_eq!(
            result["children"]
                .as_array()
                .unwrap()
                .iter()
                .map(|post| post["properties"]["uid"][0].as_str().unwrap())
                .collect::<Vec<_>>()
                [0..10],
            posts
                .iter()
                .map(|post| post["properties"]["uid"][0].as_str().unwrap())
                .collect::<Vec<_>>()
                [0..10]
        );

        tracing::debug!("Continuing with cursor: {:?}", cursor);
        let (result2, cursor2) = backend
            .read_feed_with_cursor(
                key,
                cursor.as_deref(),
                limit,
                None,
            )
            .await
            .unwrap()
            .unwrap();

        assert_eq!(
            result2["children"].as_array().unwrap()[0..10],
            posts[10..20]
        );

        tracing::debug!("Continuing with cursor: {:?}", cursor);
        let (result3, cursor3) = backend
            .read_feed_with_cursor(
                key,
                cursor2.as_deref(),
                limit,
                None,
            )
            .await
            .unwrap()
            .unwrap();

        assert_eq!(
            result3["children"].as_array().unwrap()[0..10],
            posts[20..30]
        );

        tracing::debug!("Continuing with cursor: {:?}", cursor);
        let (result4, cursor4) = backend
            .read_feed_with_cursor(
                key,
                cursor3.as_deref(),
                limit,
                None,
            )
            .await
            .unwrap()
            .unwrap();

        assert_eq!(
            result4["children"].as_array().unwrap()[0..10],
            posts[30..40]
        );

        // Regression test for #4
        //
        // Results for a bogus cursor are undefined, so we aren't
        // checking them. But the function at least shouldn't hang.
        let nonsense_after = Some("1010101010");
        let result_bogus = tokio::time::timeout(tokio::time::Duration::from_secs(10), async move {
            backend
                .read_feed_with_cursor(key, nonsense_after, limit, None)
                .await
        })
        .await
        .expect("Operation should not hang: see https://gitlab.com/kittybox/kittybox/-/issues/4");
    }

    /// Automatically generates a test suite for
    macro_rules! test_all {
        ($func_name:ident, $mod_name:ident) => {
            mod $mod_name {
                $func_name!(test_basic_operations);
                $func_name!(test_get_channel_list);
                $func_name!(test_settings);
                $func_name!(test_update);
                $func_name!(test_feed_pagination);
            }
        };
    }
    macro_rules! file_test {
        ($func_name:ident) => {
            #[tokio::test]
            #[tracing_test::traced_test]
            async fn $func_name() {
                let tempdir = tempfile::tempdir().expect("Failed to create tempdir");
                let backend = super::super::FileStorage::new(
                    tempdir.path().to_path_buf()
                )
                    .await
                    .unwrap();
                super::$func_name(backend).await
            }
        };
    }

    test_all!(file_test, file);
}