use anyhow::{Context as _, Result};
use futures::{
    AsyncBufReadExt as _, StreamExt as _,
    channel::mpsc::{self},
    io::BufReader,
};
use gpui::{App, Entity, EntityId, Task, Window};
use jupyter_protocol::{
    ExecutionState, JupyterKernelspec, JupyterMessage, KernelInfoReply,
    connection_info::{ConnectionInfo, Transport},
};
use project::Fs;
use runtimelib::dirs;
use smol::net::TcpListener;
use std::{
    env,
    fmt::Debug,
    net::{IpAddr, Ipv4Addr, SocketAddr},
    path::PathBuf,
    sync::Arc,
};

use uuid::Uuid;

use super::{KernelSession, RunningKernel, start_kernel_tasks};

#[derive(Debug, Clone)]
pub struct LocalKernelSpecification {
    pub name: String,
    pub path: PathBuf,
    pub kernelspec: JupyterKernelspec,
}

impl PartialEq for LocalKernelSpecification {
    fn eq(&self, other: &Self) -> bool {
        self.name == other.name && self.path == other.path
    }
}

impl Eq for LocalKernelSpecification {}

impl LocalKernelSpecification {
    #[must_use]
    fn command(&self, connection_path: &PathBuf) -> Result<std::process::Command> {
        let argv = &self.kernelspec.argv;

        anyhow::ensure!(!argv.is_empty(), "Empty argv in kernelspec {}", self.name);
        anyhow::ensure!(argv.len() >= 2, "Invalid argv in kernelspec {}", self.name);
        anyhow::ensure!(
            argv.iter().any(|arg| arg == "{connection_file}"),
            "Missing 'connection_file' in argv in kernelspec {}",
            self.name
        );

        let mut cmd = util::command::new_std_command(&argv[0]);

        for arg in &argv[1..] {
            if arg == "{connection_file}" {
                cmd.arg(connection_path);
            } else {
                cmd.arg(arg);
            }
        }

        if let Some(env) = &self.kernelspec.env {
            log::info!(
                "LocalKernelSpecification: applying env to command: {:?}",
                env.keys()
            );
            cmd.envs(env);
        } else {
            log::info!("LocalKernelSpecification: no env in kernelspec");
        }

        Ok(cmd)
    }
}

// Find a set of open ports. This creates a listener with port set to 0. The listener will be closed at the end when it goes out of scope.
// There's a race condition between closing the ports and usage by a kernel, but it's inherent to the Jupyter protocol.
async fn peek_ports(ip: IpAddr) -> Result<[u16; 5]> {
    let mut addr_zeroport: SocketAddr = SocketAddr::new(ip, 0);
    addr_zeroport.set_port(0);
    let mut ports: [u16; 5] = [0; 5];
    for i in 0..5 {
        let listener = TcpListener::bind(addr_zeroport).await?;
        let addr = listener.local_addr()?;
        ports[i] = addr.port();
    }
    Ok(ports)
}

pub struct NativeRunningKernel {
    pub process: util::process::Child,
    connection_path: PathBuf,
    _process_status_task: Option<Task<()>>,
    pub working_directory: PathBuf,
    pub request_tx: mpsc::Sender<JupyterMessage>,
    pub stdin_tx: mpsc::Sender<JupyterMessage>,
    pub execution_state: ExecutionState,
    pub kernel_info: Option<KernelInfoReply>,
}

impl Debug for NativeRunningKernel {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("RunningKernel")
            .field("process", &*self.process)
            .finish()
    }
}

impl NativeRunningKernel {
    pub fn new<S: KernelSession + 'static>(
        kernel_specification: LocalKernelSpecification,
        entity_id: EntityId,
        working_directory: PathBuf,
        fs: Arc<dyn Fs>,
        // todo: convert to weak view
        session: Entity<S>,
        window: &mut Window,
        cx: &mut App,
    ) -> Task<Result<Box<dyn RunningKernel>>> {
        window.spawn(cx, async move |cx| {
            let ip = IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1));
            let ports = peek_ports(ip).await?;

            let connection_info = ConnectionInfo {
                transport: Transport::TCP,
                ip: ip.to_string(),
                stdin_port: ports[0],
                control_port: ports[1],
                hb_port: ports[2],
                shell_port: ports[3],
                iopub_port: ports[4],
                signature_scheme: "hmac-sha256".to_string(),
                key: uuid::Uuid::new_v4().to_string(),
                kernel_name: Some(format!("zed-{}", kernel_specification.name)),
            };

            let runtime_dir = dirs::runtime_dir();
            fs.create_dir(&runtime_dir)
                .await
                .with_context(|| format!("Failed to create jupyter runtime dir {runtime_dir:?}"))?;
            let connection_path = runtime_dir.join(format!("kernel-zed-{entity_id}.json"));
            let content = serde_json::to_string(&connection_info)?;
            fs.atomic_write(connection_path.clone(), content).await?;

            let mut cmd = kernel_specification.command(&connection_path)?;
            cmd.current_dir(&working_directory);

            let mut process = util::process::Child::spawn(
                cmd,
                std::process::Stdio::piped(),
                std::process::Stdio::piped(),
                std::process::Stdio::piped(),
            )?;

            let session_id = Uuid::new_v4().to_string();

            let iopub_socket =
                runtimelib::create_client_iopub_connection(&connection_info, "", &session_id)
                    .await?;
            let control_socket =
                runtimelib::create_client_control_connection(&connection_info, &session_id).await?;

            let peer_identity = runtimelib::peer_identity_for_session(&session_id)?;
            let shell_socket = runtimelib::create_client_shell_connection_with_identity(
                &connection_info,
                &session_id,
                peer_identity.clone(),
            )
            .await?;
            let stdin_socket = runtimelib::create_client_stdin_connection_with_identity(
                &connection_info,
                &session_id,
                peer_identity,
            )
            .await?;

            let (request_tx, stdin_tx) = start_kernel_tasks(
                session.clone(),
                iopub_socket,
                shell_socket,
                control_socket,
                stdin_socket,
                cx,
            );

            let stderr = process.stderr.take();
            let stdout = process.stdout.take();

            cx.spawn(async move |_cx| {
                use futures::future::Either;

                let stderr_lines = match stderr {
                    Some(s) => Either::Left(
                        BufReader::new(s)
                            .lines()
                            .map(|line| (log::Level::Error, line)),
                    ),
                    None => Either::Right(futures::stream::empty()),
                };
                let stdout_lines = match stdout {
                    Some(s) => Either::Left(
                        BufReader::new(s)
                            .lines()
                            .map(|line| (log::Level::Info, line)),
                    ),
                    None => Either::Right(futures::stream::empty()),
                };
                let mut lines = futures::stream::select(stderr_lines, stdout_lines);
                while let Some((level, Ok(line))) = lines.next().await {
                    log::log!(level, "kernel: {}", line);
                }
            })
            .detach();

            let status = process.status();

            let process_status_task = cx.spawn(async move |cx| {
                let error_message = match status.await {
                    Ok(status) => {
                        if status.success() {
                            log::info!("kernel process exited successfully");
                            return;
                        }

                        format!("kernel process exited with status: {:?}", status)
                    }
                    Err(err) => {
                        format!("kernel process exited with error: {:?}", err)
                    }
                };

                log::error!("{}", error_message);

                session.update(cx, |session, cx| {
                    session.kernel_errored(error_message, cx);

                    cx.notify();
                });
            });

            anyhow::Ok(Box::new(Self {
                process,
                request_tx,
                stdin_tx,
                working_directory,
                _process_status_task: Some(process_status_task),
                connection_path,
                execution_state: ExecutionState::Idle,
                kernel_info: None,
            }) as Box<dyn RunningKernel>)
        })
    }
}

impl RunningKernel for NativeRunningKernel {
    fn request_tx(&self) -> mpsc::Sender<JupyterMessage> {
        self.request_tx.clone()
    }

    fn stdin_tx(&self) -> mpsc::Sender<JupyterMessage> {
        self.stdin_tx.clone()
    }

    fn working_directory(&self) -> &PathBuf {
        &self.working_directory
    }

    fn execution_state(&self) -> &ExecutionState {
        &self.execution_state
    }

    fn set_execution_state(&mut self, state: ExecutionState) {
        self.execution_state = state;
    }

    fn kernel_info(&self) -> Option<&KernelInfoReply> {
        self.kernel_info.as_ref()
    }

    fn set_kernel_info(&mut self, info: KernelInfoReply) {
        self.kernel_info = Some(info);
    }

    fn force_shutdown(&mut self, _window: &mut Window, _cx: &mut App) -> Task<anyhow::Result<()>> {
        self.kill();
        Task::ready(Ok(()))
    }

    fn kill(&mut self) {
        self._process_status_task.take();
        self.request_tx.close_channel();
        self.stdin_tx.close_channel();
        self.process.kill().ok();
    }
}

impl Drop for NativeRunningKernel {
    fn drop(&mut self) {
        std::fs::remove_file(&self.connection_path).ok();
        self.kill();
    }
}

async fn read_kernelspec_at(
    // Path should be a directory to a jupyter kernelspec, as in
    // /usr/local/share/jupyter/kernels/python3
    kernel_dir: PathBuf,
    fs: &dyn Fs,
) -> Result<LocalKernelSpecification> {
    let path = kernel_dir;
    let kernel_name = if let Some(kernel_name) = path.file_name() {
        kernel_name.to_string_lossy().into_owned()
    } else {
        anyhow::bail!("Invalid kernelspec directory: {path:?}");
    };

    if !fs.is_dir(path.as_path()).await {
        anyhow::bail!("Not a directory: {path:?}");
    }

    let expected_kernel_json = path.join("kernel.json");
    let spec = fs.load(expected_kernel_json.as_path()).await?;
    let spec = serde_json::from_str::<JupyterKernelspec>(&spec)?;

    Ok(LocalKernelSpecification {
        name: kernel_name,
        path,
        kernelspec: spec,
    })
}

/// Read a directory of kernelspec directories
async fn read_kernels_dir(path: PathBuf, fs: &dyn Fs) -> Result<Vec<LocalKernelSpecification>> {
    let mut kernelspec_dirs = fs.read_dir(&path).await?;

    let mut valid_kernelspecs = Vec::new();
    while let Some(path) = kernelspec_dirs.next().await {
        match path {
            Ok(path) => {
                if fs.is_dir(path.as_path()).await
                    && let Ok(kernelspec) = read_kernelspec_at(path, fs).await
                {
                    valid_kernelspecs.push(kernelspec);
                }
            }
            Err(err) => log::warn!("Error reading kernelspec directory: {err:?}"),
        }
    }

    Ok(valid_kernelspecs)
}

pub async fn local_kernel_specifications(fs: Arc<dyn Fs>) -> Result<Vec<LocalKernelSpecification>> {
    let mut data_dirs = dirs::data_dirs();

    // Pick up any kernels from conda or conda environment
    if let Ok(conda_prefix) = env::var("CONDA_PREFIX") {
        let conda_prefix = PathBuf::from(conda_prefix);
        let conda_data_dir = conda_prefix.join("share").join("jupyter");
        data_dirs.push(conda_data_dir);
    }

    // Search for kernels inside the base python environment
    let command = util::command::new_command("python")
        .arg("-c")
        .arg("import sys; print(sys.prefix)")
        .output()
        .await;

    if let Ok(command) = command
        && command.status.success()
    {
        let python_prefix = String::from_utf8(command.stdout);
        if let Ok(python_prefix) = python_prefix {
            let python_prefix = PathBuf::from(python_prefix.trim());
            let python_data_dir = python_prefix.join("share").join("jupyter");
            data_dirs.push(python_data_dir);
        }
    }

    let kernel_dirs = data_dirs
        .iter()
        .map(|dir| dir.join("kernels"))
        .map(|path| read_kernels_dir(path, fs.as_ref()))
        .collect::<Vec<_>>();

    let kernel_dirs = futures::future::join_all(kernel_dirs).await;
    let kernel_dirs = kernel_dirs
        .into_iter()
        .filter_map(Result::ok)
        .flatten()
        .collect::<Vec<_>>();

    Ok(kernel_dirs)
}

#[cfg(test)]
mod test {
    use super::*;
    use std::path::PathBuf;

    use gpui::TestAppContext;
    use project::FakeFs;
    use serde_json::json;

    #[gpui::test]
    async fn test_get_kernelspecs(cx: &mut TestAppContext) {
        let fs = FakeFs::new(cx.executor());
        fs.insert_tree(
            "/jupyter",
            json!({
                ".zed": {
                    "settings.json": r#"{ "tab_size": 8 }"#,
                    "tasks.json": r#"[{
                        "label": "cargo check",
                        "command": "cargo",
                        "args": ["check", "--all"]
                    },]"#,
                },
                "kernels": {
                    "python": {
                        "kernel.json": r#"{
                            "display_name": "Python 3",
                            "language": "python",
                            "argv": ["python3", "-m", "ipykernel_launcher", "-f", "{connection_file}"],
                            "env": {}
                        }"#
                    },
                    "deno": {
                        "kernel.json": r#"{
                            "display_name": "Deno",
                            "language": "typescript",
                            "argv": ["deno", "run", "--unstable", "--allow-net", "--allow-read", "https://deno.land/std/http/file_server.ts", "{connection_file}"],
                            "env": {}
                        }"#
                    }
                },
            }),
        )
        .await;

        let mut kernels = read_kernels_dir(PathBuf::from("/jupyter/kernels"), fs.as_ref())
            .await
            .unwrap();

        kernels.sort_by(|a, b| a.name.cmp(&b.name));

        assert_eq!(
            kernels.iter().map(|c| c.name.clone()).collect::<Vec<_>>(),
            vec!["deno", "python"]
        );
    }
}