//#![warn(clippy::unwrap_used)]
use crate::database::{filter_post, ErrorKind, Result, Settings, Storage, StorageError};
use async_trait::async_trait;
use futures::{stream, StreamExt, TryStreamExt};
use serde_json::json;
use std::collections::HashMap;
use std::io::ErrorKind as IOErrorKind;
use std::path::{Path, PathBuf};
use tokio::fs::{File, OpenOptions};
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::task::spawn_blocking;
use tracing::debug;

impl From<std::io::Error> for StorageError {
    fn from(source: std::io::Error) -> Self {
        Self::with_source(
            match source.kind() {
                IOErrorKind::NotFound => ErrorKind::NotFound,
                IOErrorKind::AlreadyExists => ErrorKind::Conflict,
                _ => ErrorKind::Backend,
            },
            "file I/O error",
            Box::new(source),
        )
    }
}

impl From<tokio::time::error::Elapsed> for StorageError {
    fn from(source: tokio::time::error::Elapsed) -> Self {
        Self::with_source(
            ErrorKind::Backend,
            "timeout on I/O operation",
            Box::new(source),
        )
    }
}

// Copied from https://stackoverflow.com/questions/39340924
// This routine is adapted from the *old* Path's `path_relative_from`
// function, which works differently from the new `relative_from` function.
// In particular, this handles the case on unix where both paths are
// absolute but with only the root as the common directory.
fn path_relative_from(path: &Path, base: &Path) -> Option<PathBuf> {
    use std::path::Component;

    if path.is_absolute() != base.is_absolute() {
        if path.is_absolute() {
            Some(PathBuf::from(path))
        } else {
            None
        }
    } else {
        let mut ita = path.components();
        let mut itb = base.components();
        let mut comps: Vec<Component> = vec![];
        loop {
            match (ita.next(), itb.next()) {
                (None, None) => break,
                (Some(a), None) => {
                    comps.push(a);
                    comps.extend(ita.by_ref());
                    break;
                }
                (None, _) => comps.push(Component::ParentDir),
                (Some(a), Some(b)) if comps.is_empty() && a == b => (),
                (Some(a), Some(b)) if b == Component::CurDir => comps.push(a),
                (Some(_), Some(b)) if b == Component::ParentDir => return None,
                (Some(a), Some(_)) => {
                    comps.push(Component::ParentDir);
                    for _ in itb {
                        comps.push(Component::ParentDir);
                    }
                    comps.push(a);
                    comps.extend(ita.by_ref());
                    break;
                }
            }
        }
        Some(comps.iter().map(|c| c.as_os_str()).collect())
    }
}

#[allow(clippy::unwrap_used, clippy::expect_used)]
#[cfg(test)]
mod tests {
    #[test]
    fn test_relative_path_resolving() {
        let path1 = std::path::Path::new("/home/vika/Projects/kittybox");
        let path2 = std::path::Path::new("/home/vika/Projects/nixpkgs");
        let relative_path = super::path_relative_from(path2, path1).unwrap();

        assert_eq!(relative_path, std::path::Path::new("../nixpkgs"))
    }
}

// TODO: Check that the path ACTUALLY IS INSIDE THE ROOT FOLDER
// This could be checked by completely resolving the path
// and checking if it has a common prefix
fn url_to_path(root: &Path, url: &str) -> PathBuf {
    let path = url_to_relative_path(url).to_logical_path(root);
    if !path.starts_with(root) {
        // TODO: handle more gracefully
        panic!("Security error: {:?} is not a prefix of {:?}", path, root)
    } else {
        path
    }
}

fn url_to_relative_path(url: &str) -> relative_path::RelativePathBuf {
    let url = axum::http::Uri::try_from(url).expect("Couldn't parse a URL");
    let mut path = relative_path::RelativePathBuf::new();
    path.push(url.authority().unwrap().to_string() + url.path() + ".json");

    path
}

fn modify_post(post: &serde_json::Value, update: &serde_json::Value) -> Result<serde_json::Value> {
    let mut add_keys: HashMap<String, Vec<serde_json::Value>> = HashMap::new();
    let mut remove_keys: Vec<String> = vec![];
    let mut remove_values: HashMap<String, Vec<serde_json::Value>> = HashMap::new();
    let mut post = post.clone();

    if let Some(delete) = update["delete"].as_array() {
        remove_keys.extend(
            delete
                .iter()
                .filter_map(|v| v.as_str())
                .map(|v| v.to_string()),
        );
    } else if let Some(delete) = update["delete"].as_object() {
        for (k, v) in delete {
            if let Some(v) = v.as_array() {
                remove_values
                    .entry(k.to_string())
                    .or_default()
                    .extend(v.clone());
            } else {
                return Err(StorageError::new(
                    ErrorKind::BadRequest,
                    "Malformed update object",
                ));
            }
        }
    }
    if let Some(add) = update["add"].as_object() {
        for (k, v) in add {
            if let Some(v) = v.as_array() {
                add_keys.insert(k.to_string(), v.clone());
            } else {
                return Err(StorageError::new(
                    ErrorKind::BadRequest,
                    "Malformed update object",
                ));
            }
        }
    }
    if let Some(replace) = update["replace"].as_object() {
        for (k, v) in replace {
            remove_keys.push(k.to_string());
            if let Some(v) = v.as_array() {
                add_keys.insert(k.to_string(), v.clone());
            } else {
                return Err(StorageError::new(
                    ErrorKind::BadRequest,
                    "Malformed update object",
                ));
            }
        }
    }

    if let Some(props) = post["properties"].as_object_mut() {
        for k in remove_keys {
            props.remove(&k);
        }
    }
    for (k, v) in remove_values {
        let k = &k;
        let props = if k == "children" {
            &mut post
        } else {
            &mut post["properties"]
        };
        v.iter().for_each(|v| {
            if let Some(vec) = props[k].as_array_mut() {
                if let Some(index) = vec.iter().position(|w| w == v) {
                    vec.remove(index);
                }
            }
        });
    }
    for (k, v) in add_keys {
        let props = if k == "children" {
            &mut post
        } else {
            &mut post["properties"]
        };
        let k = &k;
        if let Some(prop) = props[k].as_array_mut() {
            if k == "children" {
                v.into_iter().rev().for_each(|v| prop.insert(0, v));
            } else {
                prop.extend(v.into_iter());
            }
        } else {
            post["properties"][k] = serde_json::Value::Array(v)
        }
    }
    Ok(post)
}

#[derive(Clone, Debug)]
/// A backend using a folder with JSON files as a backing store.
/// Uses symbolic links to represent a many-to-one mapping of URLs to a post.
pub struct FileStorage {
    root_dir: PathBuf,
}

impl FileStorage {
    /// Create a new storage wrapping a folder specified by root_dir.
    pub async fn new(root_dir: PathBuf) -> Result<Self> {
        // TODO check if the dir is writable
        Ok(Self { root_dir })
    }
}

async fn hydrate_author<S: Storage>(
    feed: &mut serde_json::Value,
    user: &'_ Option<String>,
    storage: &S,
) {
    let url = feed["properties"]["uid"][0]
        .as_str()
        .expect("MF2 value should have a UID set! Check if you used normalize_mf2 before recording the post!");
    if let Some(author) = feed["properties"]["author"].as_array().cloned() {
        if !feed["type"]
            .as_array()
            .expect("MF2 value should have a type set!")
            .iter()
            .any(|i| i == "h-card")
        {
            let author_list: Vec<serde_json::Value> = stream::iter(author.iter())
                .then(|i| async move {
                    if let Some(i) = i.as_str() {
                        match storage.get_post(i).await {
                            Ok(post) => match post {
                                Some(post) => match filter_post(post, user) {
                                    Some(author) => author,
                                    None => json!(i),
                                },
                                None => json!(i),
                            },
                            Err(e) => {
                                log::error!("Error while hydrating post {}: {}", url, e);
                                json!(i)
                            }
                        }
                    } else {
                        i.clone()
                    }
                })
                .collect::<Vec<_>>()
                .await;
            if let Some(props) = feed["properties"].as_object_mut() {
                props["author"] = json!(author_list);
            } else {
                feed["properties"] = json!({ "author": author_list });
            }
        }
    }
}

#[async_trait]
impl Storage for FileStorage {
    #[tracing::instrument(skip(self))]
    async fn post_exists(&self, url: &str) -> Result<bool> {
        let path = url_to_path(&self.root_dir, url);
        debug!("Checking if {:?} exists...", path);
        /*let result = match tokio::fs::metadata(path).await {
            Ok(metadata) => {
                Ok(true)
            },
            Err(err) => {
                if err.kind() == IOErrorKind::NotFound {
                    Ok(false)
                } else {
                    Err(err.into())
                }
            }
        };*/
        #[allow(clippy::unwrap_used)] // JoinHandle captures panics, this closure shouldn't panic
        Ok(spawn_blocking(move || path.is_file()).await.unwrap())
    }

    #[tracing::instrument(skip(self))]
    async fn get_post(&self, url: &str) -> Result<Option<serde_json::Value>> {
        let path = url_to_path(&self.root_dir, url);
        // TODO: check that the path actually belongs to the dir of user who requested it
        // it's not like you CAN access someone else's private posts with it
        // so it's not exactly a security issue, but it's still not good
        debug!("Opening {:?}", path);

        match File::open(&path).await {
            Ok(mut file) => {
                let mut content = String::new();
                // Typechecks because OS magic acts on references
                // to FDs as if they were behind a mutex
                AsyncReadExt::read_to_string(&mut file, &mut content).await?;
                debug!(
                    "Read {} bytes successfully from {:?}",
                    content.as_bytes().len(),
                    &path
                );
                Ok(Some(serde_json::from_str(&content)?))
            }
            Err(err) => {
                if err.kind() == IOErrorKind::NotFound {
                    Ok(None)
                } else {
                    Err(err.into())
                }
            }
        }
    }

    #[tracing::instrument(skip(self))]
    async fn put_post(&self, post: &'_ serde_json::Value, user: &'_ str) -> Result<()> {
        let key = post["properties"]["uid"][0]
            .as_str()
            .expect("Tried to save a post without UID");
        let path = url_to_path(&self.root_dir, key);
        let tempfile = (&path).with_extension("tmp");
        debug!("Creating {:?}", path);

        let parent = path
            .parent()
            .expect("Parent for this directory should always exist")
            .to_owned();
        if !parent.is_dir() {
            tokio::fs::create_dir_all(parent).await?;
        }

        let mut file = tokio::fs::OpenOptions::new()
            .write(true)
            .create_new(true)
            .open(&tempfile)
            .await?;

        file.write_all(post.to_string().as_bytes()).await?;
        file.flush().await?;
        drop(file);
        tokio::fs::rename(&tempfile, &path).await?;

        if let Some(urls) = post["properties"]["url"].as_array() {
            for url in urls.iter().map(|i| i.as_str().unwrap()) {
                if url != key && url.starts_with(user) {
                    let link = url_to_path(&self.root_dir, url);
                    debug!("Creating a symlink at {:?}", link);
                    let orig = path.clone();
                    // We're supposed to have a parent here.
                    let basedir = link.parent().ok_or_else(|| {
                        StorageError::new(
                            ErrorKind::Backend,
                            "Failed to calculate parent directory when creating a symlink",
                        )
                    })?;
                    let relative = path_relative_from(&orig, basedir).unwrap();
                    println!("{:?} - {:?} = {:?}", &orig, &basedir, &relative);
                    tokio::fs::symlink(relative, link).await?;
                }
            }
        }

        if post["type"]
            .as_array()
            .unwrap()
            .iter()
            .any(|s| s.as_str() == Some("h-feed"))
        {
            println!("Adding to channel list...");
            // Add the h-feed to the channel list
            let mut path = relative_path::RelativePathBuf::new();
            path.push(
                axum::http::Uri::try_from(user.to_string())
                    .unwrap()
                    .authority()
                    .unwrap()
                    .to_string(),
            );
            path.push("channels");

            let path = path.to_path(&self.root_dir);
            let tempfilename = (&path).with_extension("tmp");
            let channel_name = post["properties"]["name"][0]
                .as_str()
                .map(|s| s.to_string())
                .unwrap_or_else(String::default);
            let key = key.to_string();

            let mut tempfile = OpenOptions::new()
                .write(true)
                .create_new(true)
                .open(&tempfilename)
                .await?;
            let mut file = OpenOptions::new()
                .read(true)
                .write(true)
                .truncate(false)
                .create(true)
                .open(&path)
                .await?;

            let mut content = String::new();
            file.read_to_string(&mut content).await?;
            drop(file);
            let mut channels: Vec<super::MicropubChannel> = if !content.is_empty() {
                serde_json::from_str(&content)?
            } else {
                Vec::default()
            };

            channels.push(super::MicropubChannel {
                uid: key.to_string(),
                name: channel_name,
            });

            tempfile
                .write_all(serde_json::to_string(&channels)?.as_bytes())
                .await?;
            tempfile.flush().await?;
            drop(tempfile);
            tokio::fs::rename(tempfilename, path).await?;
        }
        Ok(())
    }

    #[tracing::instrument(skip(self))]
    async fn update_post(&self, url: &'_ str, update: serde_json::Value) -> Result<()> {
        let path = url_to_path(&self.root_dir, url);
        let tempfilename = path.with_extension("tmp");
        #[allow(unused_variables)]
        let (old_json, new_json) = {
            let mut temp = OpenOptions::new()
                .write(true)
                .create_new(true)
                .open(&tempfilename)
                .await?;
            let mut file = OpenOptions::new().read(true).open(&path).await?;

            let mut content = String::new();
            file.read_to_string(&mut content).await?;
            let json: serde_json::Value = serde_json::from_str(&content)?;
            drop(file);
            // Apply the editing algorithms
            let new_json = modify_post(&json, &update)?;

            temp.write_all(new_json.to_string().as_bytes()).await?;
            temp.flush().await?;
            drop(temp);
            tokio::fs::rename(tempfilename, path).await?;

            (json, new_json)
        };
        // TODO check if URLs changed between old and new JSON
        Ok(())
    }

    #[tracing::instrument(skip(self))]
    async fn get_channels(&self, user: &'_ str) -> Result<Vec<super::MicropubChannel>> {
        let mut path = relative_path::RelativePathBuf::new();
        path.push(
            axum::http::Uri::try_from(user.to_string())
                .unwrap()
                .authority()
                .unwrap()
                .to_string(),
        );
        path.push("channels");

        let path = path.to_path(&self.root_dir);
        match File::open(&path).await {
            Ok(mut f) => {
                let mut content = String::new();
                f.read_to_string(&mut content).await?;
                // This should not happen, but if it does, handle it gracefully
                if content.is_empty() {
                    return Ok(vec![]);
                }
                let channels: Vec<super::MicropubChannel> = serde_json::from_str(&content)?;
                Ok(channels)
            }
            Err(e) => {
                if e.kind() == IOErrorKind::NotFound {
                    Ok(vec![])
                } else {
                    Err(e.into())
                }
            }
        }
    }

    #[tracing::instrument(skip(self))]
    async fn read_feed_with_limit(
        &self,
        url: &'_ str,
        after: &'_ Option<String>,
        limit: usize,
        user: &'_ Option<String>,
    ) -> Result<Option<serde_json::Value>> {
        if let Some(feed) = self.get_post(url).await? {
            if let Some(mut feed) = filter_post(feed, user) {
                if feed["children"].is_array() {
                    // Take this out of the MF2-JSON document to save memory
                    //
                    // This uses a clever match with enum destructuring
                    // to extract the underlying Vec without cloning it
                    let children: Vec<serde_json::Value> = match feed["children"].take() {
                        serde_json::Value::Array(children) => children,
                        // We've already checked it's an array
                        _ => unreachable!()
                    };

                    let mut posts_iter = children
                        .into_iter()
                        .map(|s: serde_json::Value| s.as_str().unwrap().to_string());
                    // Note: we can't actually use `skip_while` here because we end up emitting `after`.
                    // This imperative snippet consumes after instead of emitting it, allowing the
                    // stream of posts to return only those items that truly come *after* that one.
                    // If I would implement an Iter combinator like this, I would call it `skip_until`
                    if let Some(after) = after {
                        for s in posts_iter.by_ref() {
                            if &s == after {
                                break;
                            }
                        }
                    };
                    let posts = stream::iter(posts_iter)
                        .map(|url: String| async move { self.get_post(&url).await })
                        .buffered(std::cmp::min(3, limit))
                        // Hack to unwrap the Option and sieve out broken links
                        // Broken links return None, and Stream::filter_map skips Nones.
                        .try_filter_map(|post: Option<serde_json::Value>| async move { Ok(post) })
                        .try_filter_map(|post| async move { Ok(filter_post(post, user)) })
                        .and_then(|mut post| async move {
                            hydrate_author(&mut post, user, self).await;
                            Ok(post)
                        })
                        .take(limit);

                    match posts.try_collect::<Vec<serde_json::Value>>().await {
                        Ok(posts) => feed["children"] = serde_json::json!(posts),
                        Err(err) => {
                            return Err(StorageError::with_source(
                                ErrorKind::Other,
                                "Feed assembly error",
                                Box::new(err),
                            ));
                        }
                    }
                }
                hydrate_author(&mut feed, user, self).await;
                Ok(Some(feed))
            } else {
                Err(StorageError::new(
                    ErrorKind::PermissionDenied,
                    "specified user cannot access this post",
                ))
            }
        } else {
            Ok(None)
        }
    }

    #[tracing::instrument(skip(self))]
    async fn delete_post(&self, url: &'_ str) -> Result<()> {
        let path = url_to_path(&self.root_dir, url);
        if let Err(e) = tokio::fs::remove_file(path).await {
            Err(e.into())
        } else {
            // TODO check for dangling references in the channel list
            Ok(())
        }
    }

    #[tracing::instrument(skip(self))]
    async fn get_setting(&self, setting: Settings, user: &'_ str) -> Result<String> {
        log::debug!("User for getting settings: {}", user);
        let url = axum::http::Uri::try_from(user).expect("Couldn't parse a URL");
        let mut path = relative_path::RelativePathBuf::new();
        path.push(url.authority().unwrap().to_string());
        path.push("settings");

        let path = path.to_path(&self.root_dir);
        log::debug!("Getting settings from {:?}", &path);
        let setting = setting.to_string();
        let mut file = File::open(path).await?;
        let mut content = String::new();
        file.read_to_string(&mut content).await?;

        let settings: HashMap<String, String> = serde_json::from_str(&content)?;
        // XXX consider returning string slices instead of cloning a string every time
        // it might come with a performance hit and/or memory usage inflation
        settings
            .get(&setting)
            .cloned()
            .ok_or_else(|| StorageError::new(ErrorKind::Backend, "Setting not set"))
    }

    #[tracing::instrument(skip(self))]
    async fn set_setting(&self, setting: Settings, user: &'_ str, value: &'_ str) -> Result<()> {
        let url = axum::http::Uri::try_from(user).expect("Couldn't parse a URL");
        let mut path = relative_path::RelativePathBuf::new();
        path.push(url.authority().unwrap().to_string());
        path.push("settings");

        let path = path.to_path(&self.root_dir);
        let temppath = path.with_extension("tmp");

        let parent = path.parent().unwrap().to_owned();
        if !spawn_blocking(move || parent.is_dir()).await.unwrap() {
            tokio::fs::create_dir_all(path.parent().unwrap()).await?;
        }

        let (setting, value) = (setting.to_string(), value.to_string());

        let mut tempfile = OpenOptions::new()
            .write(true)
            .create_new(true)
            .open(&temppath)
            .await?;

        let mut settings: HashMap<String, String> = match File::open(&path).await {
            Ok(mut f) => {
                let mut content = String::new();
                f.read_to_string(&mut content).await?;
                if content.is_empty() {
                    HashMap::default()
                } else {
                    serde_json::from_str(&content)?
                }
            }
            Err(err) => {
                if err.kind() == IOErrorKind::NotFound {
                    HashMap::default()
                } else {
                    return Err(err.into());
                }
            }
        };
        settings.insert(setting, value);
        tempfile
            .write_all(serde_json::to_string(&settings)?.as_bytes())
            .await?;
        drop(tempfile);
        tokio::fs::rename(temppath, path).await?;
        Ok(())
    }
}