//! The context or environment in which the language server functions. In our
//! server implementation this is know as the `WorldState`.
//!
//! Each tick provides an immutable snapshot of the state as `WorldSnapshot`.

use std::{sync::Arc, time::Instant};

use crossbeam_channel::{unbounded, Receiver, Sender};
use flycheck::FlycheckHandle;
use ide::{Analysis, AnalysisHost, Cancellable, Change, FileId};
use ide_db::base_db::{CrateId, FileLoader, SourceDatabase};
use lsp_types::{SemanticTokens, Url};
use parking_lot::{Mutex, RwLock};
use proc_macro_api::ProcMacroServer;
use project_model::{CargoWorkspace, ProjectWorkspace, Target, WorkspaceBuildScripts};
use rustc_hash::FxHashMap;
use stdx::hash::NoHashHashMap;
use vfs::AnchoredPathBuf;

use crate::{
    config::Config,
    diagnostics::{CheckFixes, DiagnosticCollection},
    from_proto,
    line_index::{LineEndings, LineIndex},
    lsp_ext,
    main_loop::Task,
    mem_docs::MemDocs,
    op_queue::OpQueue,
    reload::{self, SourceRootConfig},
    task_pool::TaskPool,
    to_proto::url_from_abs_path,
    Result,
};

// Enforces drop order
pub(crate) struct Handle<H, C> {
    pub(crate) handle: H,
    pub(crate) receiver: C,
}

pub(crate) type ReqHandler = fn(&mut GlobalState, lsp_server::Response);
pub(crate) type ReqQueue = lsp_server::ReqQueue<(String, Instant), ReqHandler>;

/// `GlobalState` is the primary mutable state of the language server
///
/// The most interesting components are `vfs`, which stores a consistent
/// snapshot of the file systems, and `analysis_host`, which stores our
/// incremental salsa database.
///
/// Note that this struct has more than one impl in various modules!
pub(crate) struct GlobalState {
    sender: Sender<lsp_server::Message>,
    req_queue: ReqQueue,
    pub(crate) task_pool: Handle<TaskPool<Task>, Receiver<Task>>,
    pub(crate) loader: Handle<Box<dyn vfs::loader::Handle>, Receiver<vfs::loader::Message>>,
    pub(crate) config: Arc<Config>,
    pub(crate) analysis_host: AnalysisHost,
    pub(crate) diagnostics: DiagnosticCollection,
    pub(crate) mem_docs: MemDocs,
    pub(crate) semantic_tokens_cache: Arc<Mutex<FxHashMap<Url, SemanticTokens>>>,
    pub(crate) shutdown_requested: bool,
    pub(crate) proc_macro_changed: bool,
    pub(crate) last_reported_status: Option<lsp_ext::ServerStatusParams>,
    pub(crate) source_root_config: SourceRootConfig,
    pub(crate) proc_macro_clients: Vec<Result<ProcMacroServer, String>>,

    pub(crate) flycheck: Arc<[FlycheckHandle]>,
    pub(crate) flycheck_sender: Sender<flycheck::Message>,
    pub(crate) flycheck_receiver: Receiver<flycheck::Message>,

    pub(crate) vfs: Arc<RwLock<(vfs::Vfs, NoHashHashMap<FileId, LineEndings>)>>,
    pub(crate) vfs_config_version: u32,
    pub(crate) vfs_progress_config_version: u32,
    pub(crate) vfs_progress_n_total: usize,
    pub(crate) vfs_progress_n_done: usize,

    /// `workspaces` field stores the data we actually use, while the `OpQueue`
    /// stores the result of the last fetch.
    ///
    /// If the fetch (partially) fails, we do not update the current value.
    ///
    /// The handling of build data is subtle. We fetch workspace in two phases:
    ///
    /// *First*, we run `cargo metadata`, which gives us fast results for
    /// initial analysis.
    ///
    /// *Second*, we run `cargo check` which runs build scripts and compiles
    /// proc macros.
    ///
    /// We need both for the precise analysis, but we want rust-analyzer to be
    /// at least partially available just after the first phase. That's because
    /// first phase is much faster, and is much less likely to fail.
    ///
    /// This creates a complication -- by the time the second phase completes,
    /// the results of the fist phase could be invalid. That is, while we run
    /// `cargo check`, the user edits `Cargo.toml`, we notice this, and the new
    /// `cargo metadata` completes before `cargo check`.
    ///
    /// An additional complication is that we want to avoid needless work. When
    /// the user just adds comments or whitespace to Cargo.toml, we do not want
    /// to invalidate any salsa caches.
    pub(crate) workspaces: Arc<Vec<ProjectWorkspace>>,
    pub(crate) fetch_workspaces_queue: OpQueue<Option<Vec<anyhow::Result<ProjectWorkspace>>>>,
    pub(crate) fetch_build_data_queue:
        OpQueue<(Arc<Vec<ProjectWorkspace>>, Vec<anyhow::Result<WorkspaceBuildScripts>>)>,

    pub(crate) prime_caches_queue: OpQueue<()>,
}

/// An immutable snapshot of the world's state at a point in time.
pub(crate) struct GlobalStateSnapshot {
    pub(crate) config: Arc<Config>,
    pub(crate) analysis: Analysis,
    pub(crate) check_fixes: CheckFixes,
    mem_docs: MemDocs,
    pub(crate) semantic_tokens_cache: Arc<Mutex<FxHashMap<Url, SemanticTokens>>>,
    vfs: Arc<RwLock<(vfs::Vfs, NoHashHashMap<FileId, LineEndings>)>>,
    pub(crate) workspaces: Arc<Vec<ProjectWorkspace>>,
    pub(crate) proc_macros_loaded: bool,
    pub(crate) flycheck: Arc<[FlycheckHandle]>,
}

impl std::panic::UnwindSafe for GlobalStateSnapshot {}

impl GlobalState {
    pub(crate) fn new(sender: Sender<lsp_server::Message>, config: Config) -> GlobalState {
        let loader = {
            let (sender, receiver) = unbounded::<vfs::loader::Message>();
            let handle: vfs_notify::NotifyHandle =
                vfs::loader::Handle::spawn(Box::new(move |msg| sender.send(msg).unwrap()));
            let handle = Box::new(handle) as Box<dyn vfs::loader::Handle>;
            Handle { handle, receiver }
        };

        let task_pool = {
            let (sender, receiver) = unbounded();
            let handle = TaskPool::new_with_threads(sender, config.main_loop_num_threads());
            Handle { handle, receiver }
        };

        let analysis_host = AnalysisHost::new(config.lru_capacity());
        let (flycheck_sender, flycheck_receiver) = unbounded();
        let mut this = GlobalState {
            sender,
            req_queue: ReqQueue::default(),
            task_pool,
            loader,
            config: Arc::new(config.clone()),
            analysis_host,
            diagnostics: Default::default(),
            mem_docs: MemDocs::default(),
            semantic_tokens_cache: Arc::new(Default::default()),
            shutdown_requested: false,
            proc_macro_changed: false,
            last_reported_status: None,
            source_root_config: SourceRootConfig::default(),
            proc_macro_clients: vec![],

            flycheck: Arc::new([]),
            flycheck_sender,
            flycheck_receiver,

            vfs: Arc::new(RwLock::new((vfs::Vfs::default(), NoHashHashMap::default()))),
            vfs_config_version: 0,
            vfs_progress_config_version: 0,
            vfs_progress_n_total: 0,
            vfs_progress_n_done: 0,

            workspaces: Arc::new(Vec::new()),
            fetch_workspaces_queue: OpQueue::default(),
            prime_caches_queue: OpQueue::default(),

            fetch_build_data_queue: OpQueue::default(),
        };
        // Apply any required database inputs from the config.
        this.update_configuration(config);
        this
    }

    pub(crate) fn process_changes(&mut self) -> bool {
        let _p = profile::span("GlobalState::process_changes");
        let mut workspace_structure_change = None;

        let mut file_changes = FxHashMap::default();
        let (change, changed_files) = {
            let mut change = Change::new();
            let (vfs, line_endings_map) = &mut *self.vfs.write();
            let mut changed_files = vfs.take_changes();
            if changed_files.is_empty() {
                return false;
            }

            // We need to fix up the changed events a bit. If we have a create or modify for a file
            // id that is followed by a delete we actually skip observing the file text from the
            // earlier event, to avoid problems later on.
            for changed_file in &changed_files {
                use vfs::ChangeKind::*;

                file_changes
                    .entry(changed_file.file_id)
                    .and_modify(|(change, just_created)| {
                        // None -> Delete => keep
                        // Create -> Delete => collapse
                        //
                        match (change, just_created, changed_file.change_kind) {
                            // latter `Delete` wins
                            (change, _, Delete) => *change = Delete,
                            // merge `Create` with `Create` or `Modify`
                            (Create, _, Create | Modify) => {}
                            // collapse identical `Modify`es
                            (Modify, _, Modify) => {}
                            // equivalent to `Modify`
                            (change @ Delete, just_created, Create) => {
                                *change = Modify;
                                *just_created = true;
                            }
                            // shouldn't occur, but collapse into `Create`
                            (change @ Delete, just_created, Modify) => {
                                *change = Create;
                                *just_created = true;
                            }
                            // shouldn't occur, but collapse into `Modify`
                            (Modify, _, Create) => {}
                        }
                    })
                    .or_insert((
                        changed_file.change_kind,
                        matches!(changed_file.change_kind, Create),
                    ));
            }

            changed_files.extend(
                file_changes
                    .into_iter()
                    .filter(|(_, (change_kind, just_created))| {
                        !matches!((change_kind, just_created), (vfs::ChangeKind::Delete, true))
                    })
                    .map(|(file_id, (change_kind, _))| vfs::ChangedFile { file_id, change_kind }),
            );

            // A file was added or deleted
            let mut has_structure_changes = false;
            for file in &changed_files {
                if let Some(path) = vfs.file_path(file.file_id).as_path() {
                    let path = path.to_path_buf();
                    if reload::should_refresh_for_change(&path, file.change_kind) {
                        workspace_structure_change = Some(path);
                    }
                    if file.is_created_or_deleted() {
                        has_structure_changes = true;
                    }
                }

                // Clear native diagnostics when their file gets deleted
                if !file.exists() {
                    self.diagnostics.clear_native_for(file.file_id);
                }

                let text = if file.exists() {
                    let bytes = vfs.file_contents(file.file_id).to_vec();
                    String::from_utf8(bytes).ok().and_then(|text| {
                        let (text, line_endings) = LineEndings::normalize(text);
                        line_endings_map.insert(file.file_id, line_endings);
                        Some(Arc::new(text))
                    })
                } else {
                    None
                };
                change.change_file(file.file_id, text);
            }
            if has_structure_changes {
                let roots = self.source_root_config.partition(vfs);
                change.set_roots(roots);
            }
            (change, changed_files)
        };

        self.analysis_host.apply_change(change);

        {
            let raw_database = self.analysis_host.raw_database();
            // FIXME: ideally we should only trigger a workspace fetch for non-library changes
            // but somethings going wrong with the source root business when we add a new local
            // crate see https://github.com/rust-lang/rust-analyzer/issues/13029
            if let Some(path) = workspace_structure_change {
                self.fetch_workspaces_queue
                    .request_op(format!("workspace vfs file change: {}", path.display()));
            }
            self.proc_macro_changed =
                changed_files.iter().filter(|file| !file.is_created_or_deleted()).any(|file| {
                    let crates = raw_database.relevant_crates(file.file_id);
                    let crate_graph = raw_database.crate_graph();

                    crates.iter().any(|&krate| crate_graph[krate].is_proc_macro)
                });
        }

        true
    }

    pub(crate) fn snapshot(&self) -> GlobalStateSnapshot {
        GlobalStateSnapshot {
            config: Arc::clone(&self.config),
            workspaces: Arc::clone(&self.workspaces),
            analysis: self.analysis_host.analysis(),
            vfs: Arc::clone(&self.vfs),
            check_fixes: Arc::clone(&self.diagnostics.check_fixes),
            mem_docs: self.mem_docs.clone(),
            semantic_tokens_cache: Arc::clone(&self.semantic_tokens_cache),
            proc_macros_loaded: !self.fetch_build_data_queue.last_op_result().0.is_empty(),
            flycheck: self.flycheck.clone(),
        }
    }

    pub(crate) fn send_request<R: lsp_types::request::Request>(
        &mut self,
        params: R::Params,
        handler: ReqHandler,
    ) {
        let request = self.req_queue.outgoing.register(R::METHOD.to_string(), params, handler);
        self.send(request.into());
    }

    pub(crate) fn complete_request(&mut self, response: lsp_server::Response) {
        let handler = self
            .req_queue
            .outgoing
            .complete(response.id.clone())
            .expect("received response for unknown request");
        handler(self, response)
    }

    pub(crate) fn send_notification<N: lsp_types::notification::Notification>(
        &mut self,
        params: N::Params,
    ) {
        let not = lsp_server::Notification::new(N::METHOD.to_string(), params);
        self.send(not.into());
    }

    pub(crate) fn register_request(
        &mut self,
        request: &lsp_server::Request,
        request_received: Instant,
    ) {
        self.req_queue
            .incoming
            .register(request.id.clone(), (request.method.clone(), request_received));
    }

    pub(crate) fn respond(&mut self, response: lsp_server::Response) {
        if let Some((method, start)) = self.req_queue.incoming.complete(response.id.clone()) {
            if let Some(err) = &response.error {
                if err.message.starts_with("server panicked") {
                    self.poke_rust_analyzer_developer(format!("{}, check the log", err.message))
                }
            }

            let duration = start.elapsed();
            tracing::debug!("handled {} - ({}) in {:0.2?}", method, response.id, duration);
            self.send(response.into());
        }
    }

    pub(crate) fn cancel(&mut self, request_id: lsp_server::RequestId) {
        if let Some(response) = self.req_queue.incoming.cancel(request_id) {
            self.send(response.into());
        }
    }

    pub(crate) fn is_completed(&self, request: &lsp_server::Request) -> bool {
        self.req_queue.incoming.is_completed(&request.id)
    }

    fn send(&mut self, message: lsp_server::Message) {
        self.sender.send(message).unwrap()
    }
}

impl Drop for GlobalState {
    fn drop(&mut self) {
        self.analysis_host.request_cancellation();
    }
}

impl GlobalStateSnapshot {
    pub(crate) fn url_to_file_id(&self, url: &Url) -> Result<FileId> {
        url_to_file_id(&self.vfs.read().0, url)
    }

    pub(crate) fn file_id_to_url(&self, id: FileId) -> Url {
        file_id_to_url(&self.vfs.read().0, id)
    }

    pub(crate) fn file_line_index(&self, file_id: FileId) -> Cancellable<LineIndex> {
        let endings = self.vfs.read().1[&file_id];
        let index = self.analysis.file_line_index(file_id)?;
        let res = LineIndex { index, endings, encoding: self.config.position_encoding() };
        Ok(res)
    }

    pub(crate) fn url_file_version(&self, url: &Url) -> Option<i32> {
        let path = from_proto::vfs_path(url).ok()?;
        Some(self.mem_docs.get(&path)?.version)
    }

    pub(crate) fn anchored_path(&self, path: &AnchoredPathBuf) -> Url {
        let mut base = self.vfs.read().0.file_path(path.anchor);
        base.pop();
        let path = base.join(&path.path).unwrap();
        let path = path.as_path().unwrap();
        url_from_abs_path(path)
    }

    pub(crate) fn file_id_to_file_path(&self, file_id: FileId) -> vfs::VfsPath {
        self.vfs.read().0.file_path(file_id)
    }

    pub(crate) fn cargo_target_for_crate_root(
        &self,
        crate_id: CrateId,
    ) -> Option<(&CargoWorkspace, Target)> {
        let file_id = self.analysis.crate_root(crate_id).ok()?;
        let path = self.vfs.read().0.file_path(file_id);
        let path = path.as_path()?;
        self.workspaces.iter().find_map(|ws| match ws {
            ProjectWorkspace::Cargo { cargo, .. } => {
                cargo.target_by_root(path).map(|it| (cargo, it))
            }
            ProjectWorkspace::Json { .. } => None,
            ProjectWorkspace::DetachedFiles { .. } => None,
        })
    }
}

pub(crate) fn file_id_to_url(vfs: &vfs::Vfs, id: FileId) -> Url {
    let path = vfs.file_path(id);
    let path = path.as_path().unwrap();
    url_from_abs_path(path)
}

pub(crate) fn url_to_file_id(vfs: &vfs::Vfs, url: &Url) -> Result<FileId> {
    let path = from_proto::vfs_path(url)?;
    let res = vfs.file_id(&path).ok_or_else(|| format!("file not found: {path}"))?;
    Ok(res)
}