//! A world directory and the one virtual root that host code and guests share.
//!
//! Layout of a world directory:
//! - `world/`: the virtual root `/` that every guest sees. Agents change everything in it.
//! - `host/`: host state outside the sandbox (harness storage, later the vault). No guest sees it.
use anyhow::Context;
use sausage_vfs::{Device, Generated, Host, Layer, Memory, Mounts, Process};
use std::{
    os::unix::fs::PermissionsExt,
    path::{Path, PathBuf},
    sync::Arc,
};

/// An open world. `root` is the filesystem every guest sees as `/`; host code (the harness's file
/// tools) reads and writes through the same layer, so both always see the same files.
pub struct World {
    pub root: Arc<dyn Layer>,
    /// The host state folder, `<dir>/host`.
    pub host_dir: PathBuf,
    /// Live process metadata shared with the process table.
    pub processes: crate::process::Processes,
}

fn copy_tree(source: &Path, destination: &Path) -> std::io::Result<()> {
    std::fs::create_dir_all(destination)?;
    let mut permissions = std::fs::metadata(destination)?.permissions();
    permissions.set_mode(permissions.mode() | 0o200);
    std::fs::set_permissions(destination, permissions)?;
    for entry in std::fs::read_dir(source)? {
        let entry = entry?;
        let target = destination.join(entry.file_name());
        if entry.file_type()?.is_symlink() {
            std::os::unix::fs::symlink(std::fs::read_link(entry.path())?, &target)?;
        } else if entry.file_type()?.is_dir() {
            copy_tree(&entry.path(), &target)?;
        } else {
            std::fs::copy(entry.path(), &target)?;
            let mut permissions = std::fs::metadata(&target)?.permissions();
            permissions.set_mode(permissions.mode() | 0o200);
            std::fs::set_permissions(&target, permissions)?;
        }
    }
    Ok(())
}

impl World {
    /// Initialize a fresh world and commit its plain bundled source on main.
    pub async fn init(dir: &Path, bundle: &Path) -> anyhow::Result<Self> {
        Self::init_with_progress(dir, bundle, |_| {}).await
    }

    /// Initialize a world and report each step without changing normal startup output.
    pub async fn init_with_progress(
        dir: &Path,
        bundle: &Path,
        mut progress: impl FnMut(&str) + Send,
    ) -> anyhow::Result<Self> {
        anyhow::ensure!(
            !dir.join("world").exists(),
            "Create world folder failed: World already exists: {}",
            dir.display()
        );
        let world = Self::open_with_progress(dir, Some(bundle), &mut progress)
            .context("Create world folder and seed files failed")?;
        progress("Create the first commit in /src/sausage");
        let exec = crate::process::exec(Self {
            root: world.root.clone(),
            host_dir: world.host_dir.clone(),
            processes: world.processes.clone(),
        })
        .context("Create source repository failed")?;
        for args in [
            vec!["init", "-b", "main"],
            vec!["add", "."],
            vec!["commit", "--no-gpg-sign", "-m", "Initial world source"],
        ] {
            let argv = [
                vec!["/bin/git.wasm".to_owned()],
                args.into_iter().map(str::to_owned).collect(),
            ]
            .concat();
            let mut output = Vec::new();
            let code = exec
                .exec(
                    crate::exec::Command::Argv(argv),
                    crate::exec::Options {
                        cwd: "/src/sausage".into(),
                        ..Default::default()
                    },
                    &mut |_, bytes| output.extend_from_slice(bytes),
                )
                .await
                .context("Create source repository failed")?;
            anyhow::ensure!(
                code == 0,
                "Cannot initialize source repository: {}",
                String::from_utf8_lossy(&output)
            );
        }
        Ok(world)
    }

    /// Open (and create if missing) the world directory `dir`, including `/proc` and `/run` mounts.
    pub fn open(dir: &Path) -> anyhow::Result<Self> {
        Self::open_with_userland(dir, None)
    }

    /// Copy an optional bundle into a new world. Existing worlds retain their programs.
    /// Ensure `/tmp`, `/run`, and `/var/tmp` exist on every startup.
    /// Each `.wasm` tool keeps its independent file and gains a relative `/bin/<name>` symlink.
    /// `/dev` exposes generated null, zero, and random byte devices in every world.
    /// Missing `/etc/gitconfig` defaults to Sausage <sausage@localhost>. Local repository config overrides it.
    pub fn open_with_userland(dir: &Path, userland: Option<&Path>) -> anyhow::Result<Self> {
        Self::open_with_progress(dir, userland, &mut |_| {})
    }

    fn open_with_progress(
        dir: &Path,
        userland: Option<&Path>,
        progress: &mut dyn FnMut(&str),
    ) -> anyhow::Result<Self> {
        progress(&format!("Create world folder: {}", dir.display()));
        let root_dir = dir.join("world");
        let host_dir = dir.join("host");
        let fresh = !root_dir.exists();
        std::fs::create_dir_all(root_dir.join("usr/local/bin"))
            .context("Create world folder failed")?;
        for path in ["tmp", "run", "var/tmp"] {
            std::fs::create_dir_all(root_dir.join(path)).context("Create world folder failed")?;
        }
        if fresh && let Some(bundle) = userland {
            let tools = std::fs::read_dir(bundle.join("bin"))
                .context("Copy tools failed")?
                .collect::<Result<Vec<_>, _>>()
                .context("Copy tools failed")?
                .iter()
                .filter(|entry| entry.path().extension().is_some_and(|ext| ext == "wasm"))
                .count();
            progress(&format!("Copy tools: {tools}"));
            copy_tree(&bundle.join("bin"), &root_dir.join("bin")).context("Copy tools failed")?;
            progress("Create /src/sausage");
            copy_tree(&bundle.join("src"), &root_dir.join("src"))
                .context("Create /src/sausage failed")?;
            progress("Seed /etc and /srv/www");
            if bundle.join("srv").is_dir() {
                copy_tree(&bundle.join("srv"), &root_dir.join("srv"))
                    .context("Seed /srv/www failed")?;
            }
            if bundle.join("etc").is_dir() {
                progress(&format!(
                    "Write config: {}",
                    root_dir.join("etc/sausage/config.yaml").display()
                ));
                copy_tree(&bundle.join("etc"), &root_dir.join("etc"))
                    .context("Seed /etc and write config failed")?;
            }
            // Keep independent .wasm files and expose conventional executable names.
            for entry in std::fs::read_dir(root_dir.join("bin"))? {
                let path = entry?.path();
                if path.extension().is_some_and(|ext| ext == "wasm") {
                    let alias = path.with_extension("");
                    if std::fs::symlink_metadata(&alias).is_err() {
                        std::os::unix::fs::symlink(path.file_name().unwrap(), alias)?;
                    }
                }
            }
        }
        let gitconfig = root_dir.join("etc/gitconfig");
        if !gitconfig.try_exists()? {
            std::fs::create_dir_all(root_dir.join("etc"))?;
            std::fs::write(
                gitconfig,
                "[user]\n\tname = Sausage\n\temail = sausage@localhost\n",
            )?;
        }
        std::fs::create_dir_all(&host_dir)?;
        let mut mounts = Mounts::default();
        mounts.mount(
            "/",
            Arc::new(Host::new(&root_dir, Process::default())?),
            false,
        );
        let processes: crate::process::Processes =
            Arc::new(std::sync::Mutex::new(Default::default()));
        let snapshot = processes.clone();
        let mut proc = Generated::default();
        let extensions = crate::harness::loader::status(&host_dir);
        proc.insert("/extensions", move || {
            Ok(extensions.lock().unwrap().as_bytes().to_vec())
        });
        proc.insert("/processes", move || {
            let mut text = String::from("PID\tPPID\tSTATE\tCWD\tCONVERSATION\tARGV\n");
            for (pid, info) in snapshot.lock().unwrap().iter() {
                text.push_str(&format!(
                    "{pid}\t{}\t{}\t{}\t{}\t{}\n",
                    info.parent,
                    info.state,
                    info.cwd,
                    info.conversation.as_deref().unwrap_or("-"),
                    info.argv.join(" ")
                ));
            }
            Ok(text.into_bytes())
        });
        mounts.mount("/proc", Arc::new(proc), true);
        mounts.mount("/run", Arc::new(Memory::default()), false);
        let mut devices = Generated::default();
        devices.insert_device("/null", Device::Null);
        devices.insert_device("/zero", Device::Zero);
        devices.insert_device("/urandom", Device::Random);
        mounts.mount("/dev", Arc::new(devices), false);
        let journal =
            sausage_vfs::journal::Journal::open(&host_dir.join("undo"), Arc::new(mounts))?;
        let root = journal.layer(sausage_vfs::journal::Tag::process(
            std::process::id(),
            "/host".into(),
            Vec::new(),
        )?);
        Ok(World {
            root,
            host_dir,
            processes,
        })
    }
}

#[cfg(test)]
#[test]
fn readonly_bundle_copies_are_writable() -> std::io::Result<()> {
    use std::fs;
    let bundle = tempfile::tempdir()?;
    let world = tempfile::tempdir()?;
    for (name, mode) in [("bin/tool.wasm", 0o555), ("src/lib.rs", 0o444)] {
        let path = bundle.path().join(name);
        fs::create_dir_all(path.parent().unwrap())?;
        fs::write(&path, b"original")?;
        fs::set_permissions(path, fs::Permissions::from_mode(mode))?;
    }
    for path in [
        bundle.path().join("bin"),
        bundle.path().join("src"),
        bundle.path().to_owned(),
        world.path().to_owned(),
    ] {
        fs::set_permissions(path, fs::Permissions::from_mode(0o555))?;
    }
    let result = copy_tree(bundle.path(), world.path());
    // Restore source directories so the temporary directory can remove its files.
    for path in [
        bundle.path(),
        &bundle.path().join("bin"),
        &bundle.path().join("src"),
    ] {
        fs::set_permissions(path, fs::Permissions::from_mode(0o755))?;
    }
    result?;
    assert_eq!(
        fs::metadata(world.path())?.permissions().mode() & 0o777,
        0o755
    );
    for (name, mode) in [("bin/tool.wasm", 0o555), ("src/lib.rs", 0o444)] {
        let source = bundle.path().join(name);
        let target = world.path().join(name);
        assert_eq!(fs::metadata(&source)?.permissions().mode() & 0o777, mode);
        assert_eq!(
            fs::metadata(&target)?.permissions().mode() & 0o777,
            mode | 0o200
        );
        fs::write(&target, b"changed")?;
        assert_eq!(fs::read(source)?, b"original");
    }
    fs::write(world.path().join("bin/added.wasm"), b"new")?;
    fs::write(world.path().join("src/added.rs"), b"new")?;
    Ok(())
}