//! Per-process mount tables, reserved self files, and the live process namespace.
use crate::Host;
use sausage_vfs::{
    Entry, File, Generated, Layer, Memory, Mounts, Open, Process, Result, Stat, async_trait,
};
use std::{io, sync::Arc};

fn denied<T>() -> Result<T> {
    Err(io::ErrorKind::ReadOnlyFilesystem.into())
}
fn missing<T>() -> Result<T> {
    Err(io::ErrorKind::NotFound.into())
}
fn directory() -> Stat {
    Stat {
        directory: true,
        symlink: false,
        size: 0,
        accessed: None,
        modified: None,
    }
}
fn entry(name: String, directory: bool) -> Entry {
    Entry {
        name,
        directory,
        symlink: false,
    }
}
fn reserved(path: &str) -> bool {
    matches!(
        path.trim_start_matches('/').split('/').next(),
        Some("info.json" | "log" | "fs")
    )
}

impl Host {
    /// Create a console filesystem view without adding a process. Its `/self` is private and ephemeral.
    pub async fn filesystem(&self) -> anyhow::Result<Mounts> {
        self.mounts(None, Memory::default(), Process::default())
            .await
    }
    pub(crate) async fn mounts(
        &self,
        pid: Option<String>,
        memory: Memory,
        tracker: Process,
    ) -> anyhow::Result<Mounts> {
        let root = self.0.world.root.clone();
        let operations = tracker.clone();
        let host = tracker
            .clone()
            .blocking(move || sausage_vfs::Host::new(root, tracker))
            .await?;
        let mut mounts = Mounts::default();
        mounts.mount(
            "/",
            self.0
                .observer
                .layer(Arc::new(host), "/", operations.clone()),
            false,
        );
        mounts.mount("/proc", Arc::new(Proc(self.clone())), true);
        mounts.mount(
            "/self",
            self.0.observer.layer(
                Arc::new(SelfFolder {
                    host: self.clone(),
                    pid: pid.clone(),
                    memory,
                }),
                &format!("/proc/{}", pid.as_deref().unwrap_or("console")),
                operations.clone(),
            ),
            false,
        );
        mounts.mount(
            "/run",
            self.0
                .observer
                .layer(Arc::new(self.0.run.clone()), "/run", operations),
            false,
        );
        Ok(mounts)
    }
    fn core_files(&self) -> Generated {
        let mut files = Generated::default();
        files.insert(
            "/discover.json",
            || Ok(include_bytes!("core.json").to_vec()),
        );
        let protocol = include_bytes!("../../PROTOCOL.md");
        files.insert("/PROTOCOL.md", move || Ok(protocol.to_vec()));
        let graph = self.graph_json();
        files.insert("/graph.json", move || Ok(graph.clone()));
        let dot = self.graph_dot();
        files.insert("/graph.dot", move || Ok(dot.clone()));
        let locks = {
            let state = self.0.state.lock().unwrap();
            let locks: std::collections::BTreeMap<_, _> = state
                .locks
                .iter()
                .map(|(path, lock)| {
                    let waiting: Vec<_> = lock.queue.iter().map(|(pid, _)| pid).collect();
                    let info = serde_json::json!({
                        "owner": lock.owner,
                        "waiting": waiting,
                    });
                    (path.clone(), info)
                })
                .collect();
            serde_json::to_vec(&locks).unwrap()
        };
        files.insert("/locks.json", move || Ok(locks.clone()));
        for name in self.discovered_plugins() {
            if let Some(doc) = self.discover_document(&name) {
                let bytes = serde_json::to_vec(&doc).unwrap();
                files.insert(&format!("/plugins/{name}/discover.json"), move || {
                    Ok(bytes.clone())
                });
                files.insert(&format!("/plugins/{name}/client.rs"), move || {
                    sausage_interface::client_rs(&name, &doc)
                        .map(String::into_bytes)
                        .map_err(io::Error::other)
                });
            }
        }
        files
    }
}
struct Proc(Host);
impl Proc {
    fn folder(&self, path: &str) -> Result<(SelfFolder, String)> {
        let (pid, rest) = path
            .trim_start_matches('/')
            .split_once('/')
            .unwrap_or((path.trim_start_matches('/'), ""));
        let memory = self
            .0
            .0
            .state
            .lock()
            .unwrap()
            .processes
            .get(pid)
            .map(|p| p.memory.clone())
            .ok_or(io::ErrorKind::NotFound)?;
        Ok((
            SelfFolder {
                host: self.0.clone(),
                pid: Some(pid.into()),
                memory,
            },
            format!("/{rest}"),
        ))
    }
}
#[async_trait]
impl Layer for Proc {
    async fn stat(&self, path: &str, follow: bool) -> Result<Stat> {
        let path = path.trim_end_matches('/');
        let path = if path.is_empty() { "/" } else { path };
        if matches!(path.trim_end_matches('/'), "" | "/core" | "/core/plugins") {
            return Ok(directory());
        }
        if let Some(path) = path.strip_prefix("/core/") {
            return self.0.core_files().stat(&format!("/{path}"), follow).await;
        }
        let (folder, path) = self.folder(path)?;
        folder.stat(&path, follow).await
    }
    async fn list(&self, path: &str) -> Result<Vec<Entry>> {
        let path = path.trim_end_matches('/');
        let path = if path.is_empty() { "/" } else { path };
        if path == "/" {
            let mut entries = vec![entry("core".into(), true)];
            entries.extend(self.0.processes().into_keys().map(|pid| entry(pid, true)));
            entries.sort_by(|a, b| a.name.cmp(&b.name));
            return Ok(entries);
        }
        if path.trim_end_matches('/') == "/core/plugins" {
            return Ok(self
                .0
                .discovered_plugins()
                .into_iter()
                .filter(|name| self.0.discover_document(name).is_some())
                .map(|name| entry(name, true))
                .collect());
        }
        if path.trim_end_matches('/') == "/core" {
            let mut entries = self.0.core_files().list("/").await?;
            if !entries.iter().any(|e| e.name == "plugins") {
                entries.push(entry("plugins".into(), true));
            }
            return Ok(entries);
        }
        if let Some(path) = path.strip_prefix("/core/") {
            return self.0.core_files().list(&format!("/{path}")).await;
        }
        let (folder, path) = self.folder(path)?;
        folder.list(&path).await
    }
    async fn open(&self, path: &str, options: Open) -> Result<Arc<dyn File>> {
        let path = path.trim_end_matches('/');
        let path = if path.is_empty() { "/" } else { path };
        if options.write || options.create || options.truncate {
            return denied();
        }
        if matches!(path.trim_end_matches('/'), "" | "/core" | "/core/plugins") {
            return Memory::default().open("/", options).await;
        }
        if let Some(path) = path.strip_prefix("/core/") {
            return self.0.core_files().open(&format!("/{path}"), options).await;
        }
        let (folder, path) = self.folder(path)?;
        folder.open(&path, options).await
    }
    async fn mkdir(&self, _: &str) -> Result<()> {
        denied()
    }
    async fn remove_file(&self, _: &str) -> Result<()> {
        denied()
    }
    async fn remove_dir(&self, _: &str) -> Result<()> {
        denied()
    }
    async fn rename(&self, _: &str, _: &str) -> Result<()> {
        denied()
    }
}
struct SelfFolder {
    host: Host,
    pid: Option<String>,
    memory: Memory,
}
impl SelfFolder {
    async fn generated(&self, path: &str) -> Result<Generated> {
        let pid = self.pid.as_ref().ok_or(io::ErrorKind::NotFound)?;
        let bytes = match path {
            "/info.json" => {
                let info = self
                    .host
                    .0
                    .state
                    .lock()
                    .unwrap()
                    .processes
                    .get(pid)
                    .map(|p| p.info.clone())
                    .ok_or(io::ErrorKind::NotFound)?;
                serde_json::to_vec(&info).unwrap()
            }
            "/log" => {
                let lines = self
                    .host
                    .0
                    .journal
                    .query(serde_json::json!({"pid":pid,"limit":i64::MAX}))
                    .await;
                let mut bytes = Vec::new();
                for line in lines.as_array().unwrap() {
                    serde_json::to_writer(&mut bytes, line).unwrap();
                    bytes.push(b'\n');
                }
                bytes
            }
            _ => return missing(),
        };
        let mut files = Generated::default();
        files.insert(path, move || Ok(bytes.clone()));
        Ok(files)
    }
}
#[async_trait]
impl Layer for SelfFolder {
    async fn stat(&self, path: &str, follow: bool) -> Result<Stat> {
        if reserved(path) {
            self.generated(path).await?.stat(path, follow).await
        } else {
            self.memory.stat(path, follow).await
        }
    }
    async fn list(&self, path: &str) -> Result<Vec<Entry>> {
        let mut entries = self.memory.list(path).await?;
        if path == "/" && self.pid.is_some() {
            entries.extend([entry("info.json".into(), false), entry("log".into(), false)]);
        }
        Ok(entries)
    }
    async fn open(&self, path: &str, options: Open) -> Result<Arc<dyn File>> {
        if reserved(path) {
            if options.write || options.create || options.truncate {
                return denied();
            }
            self.generated(path).await?.open(path, options).await
        } else {
            self.memory.open(path, options).await
        }
    }
    async fn mkdir(&self, path: &str) -> Result<()> {
        if reserved(path) {
            denied()
        } else {
            self.memory.mkdir(path).await
        }
    }
    async fn remove_file(&self, path: &str) -> Result<()> {
        if reserved(path) {
            denied()
        } else {
            self.memory.remove_file(path).await
        }
    }
    async fn remove_dir(&self, path: &str) -> Result<()> {
        if reserved(path) || path == "/" {
            denied()
        } else {
            self.memory.remove_dir(path).await
        }
    }
    async fn rename(&self, from: &str, to: &str) -> Result<()> {
        if reserved(from) || reserved(to) || from == "/" || to == "/" {
            denied()
        } else {
            self.memory.rename(from, to).await
        }
    }
}