mod client;
pub mod file_event;
mod file_operations;
pub mod jsonrpc;
mod transport;

use arc_swap::ArcSwap;
pub use client::Client;
pub use futures_executor::block_on;
pub use helix_lsp_types as lsp;
pub use jsonrpc::Call;
use log::warn;
pub use lsp::{Position, Url};

use futures_util::stream::select_all::SelectAll;
use helix_core::syntax::config::{
    LanguageConfiguration, LanguageServerConfiguration, LanguageServerFeatures, RootMarkers,
};
use helix_stdx::path;
use slotmap::SlotMap;
use tokio::sync::mpsc::UnboundedReceiver;

use std::{
    collections::HashMap,
    fs,
    path::{Path, PathBuf},
    sync::Arc,
};

use thiserror::Error;
use tokio_stream::wrappers::UnboundedReceiverStream;

pub type Result<T, E = Error> = core::result::Result<T, E>;
pub type LanguageServerName = String;
pub use helix_core::diagnostic::LanguageServerId;

#[derive(Error, Debug)]
pub enum Error {
    #[error("protocol error: {0}")]
    Rpc(#[from] jsonrpc::Error),
    #[error("failed to parse: {0}")]
    Parse(Box<dyn std::error::Error + Send + Sync>),
    #[error("IO Error: {0}")]
    IO(#[from] std::io::Error),
    #[error("request {0} timed out")]
    Timeout(jsonrpc::Id),
    #[error("server closed the stream")]
    StreamClosed,
    #[error("Unhandled")]
    Unhandled,
    #[error(transparent)]
    ExecutableNotFound(#[from] helix_stdx::env::ExecutableNotFoundError),
    #[error(transparent)]
    Other(#[from] anyhow::Error),
}

impl From<serde_json::Error> for Error {
    fn from(value: serde_json::Error) -> Self {
        Self::Parse(Box::new(value))
    }
}

impl From<sonic_rs::Error> for Error {
    fn from(value: sonic_rs::Error) -> Self {
        Self::Parse(Box::new(value))
    }
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum OffsetEncoding {
    /// UTF-8 code units aka bytes
    Utf8,
    /// UTF-32 code units aka chars
    Utf32,
    /// UTF-16 code units
    #[default]
    Utf16,
}

pub mod util {
    use super::*;
    use helix_core::line_ending::{line_end_byte_index, line_end_char_index};
    use helix_core::snippets::{RenderedSnippet, Snippet, SnippetRenderCtx};
    use helix_core::{chars, RopeSlice};
    use helix_core::{diagnostic::NumberOrString, Range, Rope, Selection, Tendril, Transaction};

    /// Converts a diagnostic in the document to [`lsp::Diagnostic`].
    ///
    /// Panics when [`pos_to_lsp_pos`] would for an invalid range on the diagnostic.
    pub fn diagnostic_to_lsp_diagnostic(
        doc: &Rope,
        diag: &helix_core::diagnostic::Diagnostic,
        offset_encoding: OffsetEncoding,
    ) -> lsp::Diagnostic {
        use helix_core::diagnostic::Severity::*;

        let range = Range::new(diag.range.start, diag.range.end);
        let severity = diag.severity.map(|s| match s {
            Hint => lsp::DiagnosticSeverity::HINT,
            Info => lsp::DiagnosticSeverity::INFORMATION,
            Warning => lsp::DiagnosticSeverity::WARNING,
            Error => lsp::DiagnosticSeverity::ERROR,
        });

        let code = match diag.code.clone() {
            Some(x) => match x {
                NumberOrString::Number(x) => Some(lsp::NumberOrString::Number(x)),
                NumberOrString::String(x) => Some(lsp::NumberOrString::String(x)),
            },
            None => None,
        };

        let new_tags: Vec<_> = diag
            .tags
            .iter()
            .map(|tag| match tag {
                helix_core::diagnostic::DiagnosticTag::Unnecessary => {
                    lsp::DiagnosticTag::UNNECESSARY
                }
                helix_core::diagnostic::DiagnosticTag::Deprecated => lsp::DiagnosticTag::DEPRECATED,
            })
            .collect();

        let tags = if !new_tags.is_empty() {
            Some(new_tags)
        } else {
            None
        };

        lsp::Diagnostic {
            range: range_to_lsp_range(doc, range, offset_encoding),
            severity,
            code,
            source: diag.source.clone(),
            message: diag.message.to_owned(),
            related_information: None,
            tags,
            data: diag.data.to_owned(),
            ..Default::default()
        }
    }

    /// Converts [`lsp::Position`] to a position in the document.
    ///
    /// Returns `None` if position.line is out of bounds or an overflow occurs
    pub fn lsp_pos_to_pos(
        doc: &Rope,
        pos: lsp::Position,
        offset_encoding: OffsetEncoding,
    ) -> Option<usize> {
        let pos_line = pos.line as usize;
        if pos_line > doc.len_lines() - 1 {
            // If it extends past the end, truncate it to the end. This is because the
            // way the LSP describes the range including the last newline is by
            // specifying a line number after what we would call the last line.
            log::warn!("LSP position {pos:?} out of range assuming EOF");
            return Some(doc.len_chars());
        }

        // We need to be careful here to fully comply ith the LSP spec.
        // Two relevant quotes from the spec:
        //
        // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#position
        // > If the character value is greater than the line length it defaults back
        // >  to the line length.
        //
        // https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocuments
        // > To ensure that both client and server split the string into the same
        // > line representation the protocol specifies the following end-of-line sequences:
        // > ‘\n’, ‘\r\n’ and ‘\r’. Positions are line end character agnostic.
        // > So you can not specify a position that denotes \r|\n or \n| where | represents the character offset.
        //
        // This means that while the line must be in bounds the `character`
        // must be capped to the end of the line.
        // Note that the end of the line here is **before** the line terminator
        // so we must use `line_end_char_index` instead of `doc.line_to_char(pos_line + 1)`
        //
        // FIXME: Helix does not fully comply with the LSP spec for line terminators.
        // The LSP standard requires that line terminators are ['\n', '\r\n', '\r'].
        // Without the unicode-linebreak feature disabled, the `\r` terminator is not handled by helix.
        // With the unicode-linebreak feature, helix recognizes multiple extra line break chars
        // which means that positions will be decoded/encoded incorrectly in their presence

        let line = match offset_encoding {
            OffsetEncoding::Utf8 => {
                let line_start = doc.line_to_byte(pos_line);
                let line_end = line_end_byte_index(&doc.slice(..), pos_line);
                line_start..line_end
            }
            OffsetEncoding::Utf16 => {
                // TODO directly translate line index to char-idx
                // ropey can do this just as easily as utf-8 byte translation
                // but the functions are just missing.
                // Translate to char first and then utf-16 as a workaround
                let line_start = doc.line_to_char(pos_line);
                let line_end = line_end_char_index(&doc.slice(..), pos_line);
                doc.char_to_utf16_cu(line_start)..doc.char_to_utf16_cu(line_end)
            }
            OffsetEncoding::Utf32 => {
                let line_start = doc.line_to_char(pos_line);
                let line_end = line_end_char_index(&doc.slice(..), pos_line);
                line_start..line_end
            }
        };

        // The LSP spec demands that the offset is capped to the end of the line
        let pos = line
            .start
            .checked_add(pos.character as usize)
            .unwrap_or(line.end)
            .min(line.end);

        match offset_encoding {
            OffsetEncoding::Utf8 => doc.try_byte_to_char(pos).ok(),
            OffsetEncoding::Utf16 => doc.try_utf16_cu_to_char(pos).ok(),
            OffsetEncoding::Utf32 => Some(pos),
        }
    }

    /// Converts position in the document to [`lsp::Position`].
    ///
    /// Panics when `pos` is out of `doc` bounds or operation overflows.
    pub fn pos_to_lsp_pos(
        doc: &Rope,
        pos: usize,
        offset_encoding: OffsetEncoding,
    ) -> lsp::Position {
        match offset_encoding {
            OffsetEncoding::Utf8 => {
                let line = doc.char_to_line(pos);
                let line_start = doc.line_to_byte(line);
                let col = doc.char_to_byte(pos) - line_start;

                lsp::Position::new(line as u32, col as u32)
            }
            OffsetEncoding::Utf16 => {
                let line = doc.char_to_line(pos);
                let line_start = doc.char_to_utf16_cu(doc.line_to_char(line));
                let col = doc.char_to_utf16_cu(pos) - line_start;

                lsp::Position::new(line as u32, col as u32)
            }
            OffsetEncoding::Utf32 => {
                let line = doc.char_to_line(pos);
                let line_start = doc.line_to_char(line);
                let col = pos - line_start;

                lsp::Position::new(line as u32, col as u32)
            }
        }
    }

    /// Converts a range in the document to [`lsp::Range`].
    pub fn range_to_lsp_range(
        doc: &Rope,
        range: Range,
        offset_encoding: OffsetEncoding,
    ) -> lsp::Range {
        let start = pos_to_lsp_pos(doc, range.from(), offset_encoding);
        let end = pos_to_lsp_pos(doc, range.to(), offset_encoding);

        lsp::Range::new(start, end)
    }

    pub fn lsp_range_to_range(
        doc: &Rope,
        mut range: lsp::Range,
        offset_encoding: OffsetEncoding,
    ) -> Option<Range> {
        // This is sort of an edgecase. It's not clear from the spec how to deal with
        // ranges where end < start. They don't make much sense but vscode simply caps start to end
        // and because it's not specified quite a few LS rely on this as a result (for example the TS server)
        if range.start > range.end {
            log::error!(
                "Invalid LSP range start {:?} > end {:?}, using an empty range at the end instead",
                range.start,
                range.end
            );
            range.start = range.end;
        }
        let start = lsp_pos_to_pos(doc, range.start, offset_encoding)?;
        let end = lsp_pos_to_pos(doc, range.end, offset_encoding)?;

        Some(Range::new(start, end))
    }

    /// If the LS did not provide a range for the completion or the range of the
    /// primary cursor can not be used for the secondary cursor, this function
    /// can be used to find the completion range for a cursor
    fn find_completion_range(text: RopeSlice, replace_mode: bool, cursor: usize) -> (usize, usize) {
        let start = cursor
            - text
                .chars_at(cursor)
                .reversed()
                .take_while(|ch| chars::char_is_word(*ch))
                .count();
        let mut end = cursor;
        if replace_mode {
            end += text
                .chars_at(cursor)
                .take_while(|ch| chars::char_is_word(*ch))
                .count();
        }
        (start, end)
    }
    fn completion_range(
        text: RopeSlice,
        edit_offset: Option<(i128, i128)>,
        replace_mode: bool,
        cursor: usize,
    ) -> Option<(usize, usize)> {
        let res = match edit_offset {
            Some((start_offset, end_offset)) => {
                let start_offset = cursor as i128 + start_offset;
                if start_offset < 0 {
                    return None;
                }
                let end_offset = cursor as i128 + end_offset;
                if end_offset > text.len_chars() as i128 {
                    return None;
                }
                (start_offset as usize, end_offset as usize)
            }
            None => find_completion_range(text, replace_mode, cursor),
        };
        Some(res)
    }

    /// Creates a [Transaction] from the [lsp::TextEdit] in a completion response.
    /// The transaction applies the edit to all cursors.
    pub fn generate_transaction_from_completion_edit(
        doc: &Rope,
        selection: &Selection,
        edit_offset: Option<(i128, i128)>,
        replace_mode: bool,
        new_text: String,
    ) -> Transaction {
        let replacement: Option<Tendril> = if new_text.is_empty() {
            None
        } else {
            Some(new_text.into())
        };

        let text = doc.slice(..);
        let (removed_start, removed_end) = completion_range(
            text,
            edit_offset,
            replace_mode,
            selection.primary().cursor(text),
        )
        .expect("transaction must be valid for primary selection");
        let removed_text = text.slice(removed_start..removed_end);

        let (transaction, mut selection) = Transaction::change_by_selection_ignore_overlapping(
            doc,
            selection,
            |range| {
                let cursor = range.cursor(text);
                completion_range(text, edit_offset, replace_mode, cursor)
                    .filter(|(start, end)| text.slice(start..end) == removed_text)
                    .unwrap_or_else(|| find_completion_range(text, replace_mode, cursor))
            },
            |_, _| replacement.clone(),
        );
        if transaction.changes().is_empty() {
            return transaction;
        }
        selection = selection.map(transaction.changes());
        transaction.with_selection(selection)
    }

    /// Creates a [Transaction] from the [Snippet] in a completion response.
    /// The transaction applies the edit to all cursors.
    pub fn generate_transaction_from_snippet(
        doc: &Rope,
        selection: &Selection,
        edit_offset: Option<(i128, i128)>,
        replace_mode: bool,
        snippet: Snippet,
        cx: &mut SnippetRenderCtx,
    ) -> (Transaction, RenderedSnippet) {
        let text = doc.slice(..);
        let (removed_start, removed_end) = completion_range(
            text,
            edit_offset,
            replace_mode,
            selection.primary().cursor(text),
        )
        .expect("transaction must be valid for primary selection");
        let removed_text = text.slice(removed_start..removed_end);
        let (transaction, mapped_selection, snippet) = snippet.render(
            doc,
            selection,
            |range| {
                let cursor = range.cursor(text);
                completion_range(text, edit_offset, replace_mode, cursor)
                    .filter(|(start, end)| text.slice(start..end) == removed_text)
                    .unwrap_or_else(|| find_completion_range(text, replace_mode, cursor))
            },
            cx,
        );
        let transaction = transaction.with_selection(snippet.first_selection(
            // we keep the direction of the old primary selection in case it changed during mapping
            // but use the primary idx from the mapped selection in case ranges had to be merged
            selection.primary().direction(),
            mapped_selection.primary_index(),
        ));
        (transaction, snippet)
    }

    pub fn generate_transaction_from_edits(
        doc: &Rope,
        mut edits: Vec<lsp::TextEdit>,
        offset_encoding: OffsetEncoding,
    ) -> Transaction {
        // Sort edits by start range, since some LSPs (Omnisharp) send them
        // in reverse order.
        edits.sort_by_key(|edit| edit.range.start);

        // Generate a diff if the edit is a full document replacement.
        #[allow(clippy::collapsible_if)]
        if edits.len() == 1 {
            let is_document_replacement = edits.first().and_then(|edit| {
                let start = lsp_pos_to_pos(doc, edit.range.start, offset_encoding)?;
                let end = lsp_pos_to_pos(doc, edit.range.end, offset_encoding)?;
                Some(start..end)
            }) == Some(0..doc.len_chars());
            if is_document_replacement {
                let new_text = Rope::from(edits.pop().unwrap().new_text);
                return helix_core::diff::compare_ropes(doc, &new_text);
            }
        }

        // `ChangeSet::from_changes` requires its changes to be sorted and
        // non-overlapping (it does `retain(from - last)`, which underflows when
        // `from < last`). The sort above handles ordering, but the LSP spec
        // already forbids overlapping edits and some servers violate that. So
        // resolve the edits here and drop any that overlap an earlier one (or
        // fail to map), instead of feeding an overlap into `from_changes` and
        // panicking. This matches the overlap policy of `Transaction::delete`.
        // See issue #15514 / AUDIT-044/045.
        let mut last_end = 0;
        let mut changes: Vec<(usize, usize, Option<helix_core::Tendril>)> =
            Vec::with_capacity(edits.len());
        for edit in edits {
            let Some(start) = lsp_pos_to_pos(doc, edit.range.start, offset_encoding) else {
                continue;
            };
            let Some(end) = lsp_pos_to_pos(doc, edit.range.end, offset_encoding) else {
                continue;
            };

            if start > end {
                log::error!("Invalid LSP text edit start {start:?} > end {end:?}, discarding");
                continue;
            }

            if start < last_end {
                log::error!(
                    "Overlapping LSP text edit {start}..{end} (after {last_end}), discarding"
                );
                continue;
            }
            last_end = end;

            // simplify "" into None for cleaner changesets
            let replacement = if edit.new_text.is_empty() {
                None
            } else {
                Some(edit.new_text.into())
            };

            changes.push((start, end, replacement));
        }

        Transaction::change(doc, changes.into_iter())
    }
}

#[derive(Debug, PartialEq, Clone)]
pub enum MethodCall {
    WorkDoneProgressCreate(lsp::WorkDoneProgressCreateParams),
    ApplyWorkspaceEdit(lsp::ApplyWorkspaceEditParams),
    WorkspaceFolders,
    WorkspaceConfiguration(lsp::ConfigurationParams),
    RegisterCapability(lsp::RegistrationParams),
    UnregisterCapability(lsp::UnregistrationParams),
    ShowDocument(lsp::ShowDocumentParams),
    WorkspaceDiagnosticRefresh,
    ShowMessageRequest(lsp::ShowMessageRequestParams),
}

impl MethodCall {
    pub fn parse(method: &str, params: jsonrpc::Params) -> Result<MethodCall> {
        use lsp::request::Request;
        let request = match method {
            lsp::request::WorkDoneProgressCreate::METHOD => {
                let params: lsp::WorkDoneProgressCreateParams = params.parse()?;
                Self::WorkDoneProgressCreate(params)
            }
            lsp::request::ApplyWorkspaceEdit::METHOD => {
                let params: lsp::ApplyWorkspaceEditParams = params.parse()?;
                Self::ApplyWorkspaceEdit(params)
            }
            lsp::request::WorkspaceFoldersRequest::METHOD => Self::WorkspaceFolders,
            lsp::request::WorkspaceConfiguration::METHOD => {
                let params: lsp::ConfigurationParams = params.parse()?;
                Self::WorkspaceConfiguration(params)
            }
            lsp::request::RegisterCapability::METHOD => {
                let params: lsp::RegistrationParams = params.parse()?;
                Self::RegisterCapability(params)
            }
            lsp::request::UnregisterCapability::METHOD => {
                let params: lsp::UnregistrationParams = params.parse()?;
                Self::UnregisterCapability(params)
            }
            lsp::request::ShowDocument::METHOD => {
                let params: lsp::ShowDocumentParams = params.parse()?;
                Self::ShowDocument(params)
            }
            lsp::request::WorkspaceDiagnosticRefresh::METHOD => Self::WorkspaceDiagnosticRefresh,
            lsp::request::ShowMessageRequest::METHOD => {
                let params: lsp::ShowMessageRequestParams = params.parse()?;
                Self::ShowMessageRequest(params)
            }
            _ => {
                return Err(Error::Unhandled);
            }
        };
        Ok(request)
    }
}

#[derive(Debug, PartialEq, Clone)]
pub enum Notification {
    // we inject this notification to signal the LSP is ready
    Initialized,
    // and this notification to signal that the LSP exited
    Exit,
    PublishDiagnostics(lsp::PublishDiagnosticsParams),
    ShowMessage(lsp::ShowMessageParams),
    LogMessage(lsp::LogMessageParams),
    ProgressMessage(lsp::ProgressParams),
}

impl Notification {
    pub fn parse(method: &str, params: jsonrpc::Params) -> Result<Notification> {
        use lsp::notification::Notification as _;

        let notification = match method {
            lsp::notification::Initialized::METHOD => Self::Initialized,
            lsp::notification::Exit::METHOD => Self::Exit,
            lsp::notification::PublishDiagnostics::METHOD => {
                let params: lsp::PublishDiagnosticsParams = params.parse()?;
                Self::PublishDiagnostics(params)
            }

            lsp::notification::ShowMessage::METHOD => {
                let params: lsp::ShowMessageParams = params.parse()?;
                Self::ShowMessage(params)
            }
            lsp::notification::LogMessage::METHOD => {
                let params: lsp::LogMessageParams = params.parse()?;
                Self::LogMessage(params)
            }
            lsp::notification::Progress::METHOD => {
                let params: lsp::ProgressParams = params.parse()?;
                Self::ProgressMessage(params)
            }
            _ => {
                return Err(Error::Unhandled);
            }
        };

        Ok(notification)
    }
}

#[derive(Debug)]
pub struct Registry {
    inner: SlotMap<LanguageServerId, Arc<Client>>,
    inner_by_name: HashMap<LanguageServerName, Vec<Arc<Client>>>,
    syn_loader: Arc<ArcSwap<helix_core::syntax::Loader>>,
    pub incoming: SelectAll<UnboundedReceiverStream<(LanguageServerId, Call)>>,
    pub file_event_handler: file_event::Handler,
}

impl Registry {
    pub fn new(syn_loader: Arc<ArcSwap<helix_core::syntax::Loader>>) -> Self {
        Self {
            inner: SlotMap::with_key(),
            inner_by_name: HashMap::new(),
            syn_loader,
            incoming: SelectAll::new(),
            file_event_handler: file_event::Handler::new(),
        }
    }

    pub fn get_by_id(&self, id: LanguageServerId) -> Option<&Arc<Client>> {
        self.inner.get(id)
    }

    pub fn remove_by_id(&mut self, id: LanguageServerId) {
        let Some(client) = self.inner.remove(id) else {
            log::debug!("client was already removed");
            return;
        };
        self.file_event_handler.remove_client(id);
        let instances = self
            .inner_by_name
            .get_mut(client.name())
            .expect("inner and inner_by_name must be synced");
        instances.retain(|ls| id != ls.id());
        if instances.is_empty() {
            self.inner_by_name.remove(client.name());
        }
    }

    fn start_client(
        &mut self,
        name: String,
        ls_config: &LanguageConfiguration,
        doc_path: Option<&std::path::Path>,
        root_dirs: &[PathBuf],
        enable_snippets: bool,
    ) -> Result<Arc<Client>, StartupError> {
        let syn_loader = self.syn_loader.load();
        let config = syn_loader
            .language_server_configs()
            .get(&name)
            .ok_or_else(|| anyhow::anyhow!("Language server '{name}' not defined"))?;
        let id = self.inner.try_insert_with_key(|id| {
            start_client(
                id,
                name,
                ls_config,
                config,
                doc_path,
                root_dirs,
                enable_snippets,
            )
            .map(|client| {
                self.incoming.push(UnboundedReceiverStream::new(client.1));
                client.0
            })
        })?;
        Ok(self.inner[id].clone())
    }

    /// If this method is called, all documents that have a reference to the language server have to refresh their language servers,
    /// See helix_view::editor::Editor::refresh_language_servers
    pub fn restart_server(
        &mut self,
        name: &str,
        language_config: &LanguageConfiguration,
        doc_path: Option<&std::path::Path>,
        root_dirs: &[PathBuf],
        enable_snippets: bool,
    ) -> Option<Result<Arc<Client>>> {
        if let Some(old_clients) = self.inner_by_name.remove(name) {
            if old_clients.is_empty() {
                log::info!("restarting client for '{name}' which was manually stopped");
            } else {
                log::info!("stopping existing clients for '{name}'");
            }
            for old_client in old_clients {
                self.file_event_handler.remove_client(old_client.id());
                self.inner.remove(old_client.id());
                old_client.force_shutdown();
            }
        }
        let client = match self.start_client(
            name.to_string(),
            language_config,
            doc_path,
            root_dirs,
            enable_snippets,
        ) {
            Ok(client) => client,
            Err(StartupError::NoRequiredRootFound) => return None,
            Err(StartupError::Error(err)) => return Some(Err(err)),
        };
        self.inner_by_name
            .insert(name.to_owned(), vec![client.clone()]);

        Some(Ok(client))
    }

    pub fn stop(&mut self, name: &str) {
        if let Some(clients) = self.inner_by_name.get_mut(name) {
            // Drain the clients vec so that the entry in `inner_by_name` remains
            // empty. We use the empty vec as a "tombstone" to mean that a server
            // has been manually stopped with :lsp-stop and shouldn't be automatically
            // restarted by `get`. :lsp-restart can be used to restart the server
            // manually.
            for client in clients.drain(..) {
                self.file_event_handler.remove_client(client.id());
                self.inner.remove(client.id());
                client.force_shutdown();
            }
        }
    }

    pub fn get<'a>(
        &'a mut self,
        language_config: &'a LanguageConfiguration,
        doc_path: Option<&'a std::path::Path>,
        root_dirs: &'a [PathBuf],
        enable_snippets: bool,
    ) -> impl Iterator<Item = (LanguageServerName, Result<Arc<Client>>)> + 'a {
        language_config.language_servers.iter().filter_map(
            move |LanguageServerFeatures { name, .. }| {
                if let Some(clients) = self.inner_by_name.get(name) {
                    // If the clients vec is empty, do not automatically start a client
                    // for this server. The empty vec is a tombstone left to mean that a
                    // server has been manually stopped and shouldn't be started automatically.
                    // See `stop`.
                    if clients.is_empty() {
                        return None;
                    }

                    if let Some((_, client)) = clients.iter().enumerate().find(|(i, client)| {
                        let manual_roots = language_config
                            .workspace_lsp_roots
                            .as_deref()
                            .unwrap_or(root_dirs);
                        client.try_add_doc(&language_config.roots, manual_roots, doc_path, *i == 0)
                    }) {
                        return Some((name.to_owned(), Ok(client.clone())));
                    }
                }
                match self.start_client(
                    name.clone(),
                    language_config,
                    doc_path,
                    root_dirs,
                    enable_snippets,
                ) {
                    Ok(client) => {
                        self.inner_by_name
                            .entry(name.to_owned())
                            .or_default()
                            .push(client.clone());
                        Some((name.clone(), Ok(client)))
                    }
                    Err(StartupError::NoRequiredRootFound) => None,
                    Err(StartupError::Error(err)) => Some((name.to_owned(), Err(err))),
                }
            },
        )
    }

    pub fn iter_clients(&self) -> impl Iterator<Item = &Arc<Client>> {
        self.inner.values()
    }
}

#[derive(Debug)]
pub enum ProgressStatus {
    Created,
    Started {
        title: String,
        progress: lsp::WorkDoneProgress,
    },
}

impl ProgressStatus {
    pub fn progress(&self) -> Option<&lsp::WorkDoneProgress> {
        match &self {
            ProgressStatus::Created => None,
            ProgressStatus::Started { title: _, progress } => Some(progress),
        }
    }
}

#[derive(Default, Debug)]
/// Acts as a container for progress reported by language servers. Each server
/// has a unique id assigned at creation through [`Registry`]. This id is then used
/// to store the progress in this map.
pub struct LspProgressMap(HashMap<LanguageServerId, HashMap<lsp::ProgressToken, ProgressStatus>>);

impl LspProgressMap {
    pub fn new() -> Self {
        Self::default()
    }

    /// Returns a map of all tokens corresponding to the language server with `id`.
    pub fn progress_map(
        &self,
        id: LanguageServerId,
    ) -> Option<&HashMap<lsp::ProgressToken, ProgressStatus>> {
        self.0.get(&id)
    }

    pub fn is_progressing(&self, id: LanguageServerId) -> bool {
        self.0.get(&id).map(|it| !it.is_empty()).unwrap_or_default()
    }

    /// Returns last progress status for a given server with `id` and `token`.
    pub fn progress(
        &self,
        id: LanguageServerId,
        token: &lsp::ProgressToken,
    ) -> Option<&ProgressStatus> {
        self.0.get(&id).and_then(|values| values.get(token))
    }

    pub fn title(&self, id: LanguageServerId, token: &lsp::ProgressToken) -> Option<&String> {
        self.progress(id, token).and_then(|p| match p {
            ProgressStatus::Created => None,
            ProgressStatus::Started { title, .. } => Some(title),
        })
    }

    /// Checks if progress `token` for server with `id` is created.
    pub fn is_created(&mut self, id: LanguageServerId, token: &lsp::ProgressToken) -> bool {
        self.0
            .get(&id)
            .map(|values| values.get(token).is_some())
            .unwrap_or_default()
    }

    pub fn create(&mut self, id: LanguageServerId, token: lsp::ProgressToken) {
        self.0
            .entry(id)
            .or_default()
            .insert(token, ProgressStatus::Created);
    }

    /// Ends the progress by removing the `token` from server with `id`, if removed returns the value.
    pub fn end_progress(
        &mut self,
        id: LanguageServerId,
        token: &lsp::ProgressToken,
    ) -> Option<ProgressStatus> {
        self.0.get_mut(&id).and_then(|vals| vals.remove(token))
    }

    /// Updates the progress of `token` for server with `id` to begin state `status`
    pub fn begin(
        &mut self,
        id: LanguageServerId,
        token: lsp::ProgressToken,
        status: lsp::WorkDoneProgressBegin,
    ) {
        self.0.entry(id).or_default().insert(
            token,
            ProgressStatus::Started {
                title: status.title.clone(),
                progress: lsp::WorkDoneProgress::Begin(status),
            },
        );
    }

    /// Updates the progress of `token` for server with `id` to report state `status`.
    pub fn update(
        &mut self,
        id: LanguageServerId,
        token: lsp::ProgressToken,
        status: lsp::WorkDoneProgressReport,
    ) {
        self.0
            .entry(id)
            .or_default()
            .entry(token)
            .and_modify(|e| match e {
                ProgressStatus::Created => (),
                ProgressStatus::Started { progress, .. } => {
                    *progress = lsp::WorkDoneProgress::Report(status)
                }
            });
    }
}

struct NewClient(Arc<Client>, UnboundedReceiver<(LanguageServerId, Call)>);

enum StartupError {
    NoRequiredRootFound,
    Error(Error),
}

impl<T: Into<Error>> From<T> for StartupError {
    fn from(value: T) -> Self {
        StartupError::Error(value.into())
    }
}

/// start_client takes both a LanguageConfiguration and a LanguageServerConfiguration to ensure that
/// it is only called when it makes sense.
fn start_client(
    id: LanguageServerId,
    name: String,
    config: &LanguageConfiguration,
    ls_config: &LanguageServerConfiguration,
    doc_path: Option<&std::path::Path>,
    root_dirs: &[PathBuf],
    enable_snippets: bool,
) -> Result<NewClient, StartupError> {
    let (workspace, workspace_is_cwd) = helix_loader::find_workspace();
    let workspace = path::normalize(workspace);
    let root = find_lsp_workspace(
        doc_path
            .and_then(|x| x.parent().and_then(|x| x.to_str()))
            .unwrap_or("."),
        &config.roots,
        config.workspace_lsp_roots.as_deref().unwrap_or(root_dirs),
        &workspace,
        workspace_is_cwd,
    );

    // `root_uri` and `workspace_folder` can be empty in case there is no workspace
    // `root_url` can not, use `workspace` as a fallback
    let root_path = root.clone().unwrap_or_else(|| workspace.clone());
    let root_uri = root.and_then(|root| lsp::Url::from_file_path(root).ok());

    if let Some(globset) = &ls_config.required_root_patterns {
        if !root_path
            .read_dir()?
            .flatten()
            .map(|entry| entry.file_name())
            .any(|entry| globset.is_match(entry))
        {
            // TODO: also show the globset that should be matched: https://github.com/BurntSushi/ripgrep/issues/3274
            warn!("The lsp {name:?} tried to start at {root_path:?} but failed to match it's 'required_root_patterns'");
            return Err(StartupError::NoRequiredRootFound);
        }
    }

    let (client, incoming, initialize_notify) = Client::start(
        &ls_config.command,
        &ls_config.args,
        ls_config.config.clone(),
        &ls_config.environment,
        root_path,
        root_uri,
        id,
        name,
        ls_config.timeout,
    )?;

    let client = Arc::new(client);

    // Initialize the client asynchronously
    let _client = client.clone();
    tokio::spawn(async move {
        use futures_util::TryFutureExt;
        let value = _client
            .capabilities
            .get_or_try_init(|| {
                _client
                    .initialize(enable_snippets)
                    .map_ok(|response| response.capabilities)
            })
            .await;

        if let Err(e) = value {
            log::error!("failed to initialize language server: {}", e);
            return;
        }

        // next up, notify<initialized>
        _client.notify::<lsp::notification::Initialized>(lsp::InitializedParams {});

        initialize_notify.notify_one();
    });

    Ok(NewClient(client, incoming))
}

/// Find an LSP workspace of a file using the following mechanism:
/// * if the file is outside `workspace` return `None`
/// * start at `file` and search the file tree upward
/// * stop the search at the first `root_dirs` entry that contains `file`
/// * if no `root_dirs` matches `file` stop at workspace
/// * Returns the top most directory that contains a `root_marker`
/// * If no root marker and we stopped at a `root_dirs` entry, return the directory we stopped at
/// * If we stopped at `workspace` instead and `workspace_is_cwd == false` return `None`
/// * If we stopped at `workspace` instead and `workspace_is_cwd == true` return `workspace`
pub fn find_lsp_workspace(
    file: &str,
    root_markers: &RootMarkers,
    root_dirs: &[PathBuf],
    workspace: &Path,
    workspace_is_cwd: bool,
) -> Option<PathBuf> {
    let file = std::path::Path::new(file);
    let mut file = if file.is_absolute() {
        file.to_path_buf()
    } else {
        let current_dir = helix_stdx::env::current_working_dir();
        current_dir.join(file)
    };
    file = path::normalize(&file);

    if !file.starts_with(workspace) {
        return None;
    }

    let mut top_marker = None;
    for ancestor in file.ancestors() {
        let Ok(mut dir) = fs::read_dir(ancestor) else {
            continue;
        };

        if dir.any(|entry| {
            if let Ok(entry) = entry {
                return root_markers.is_match(entry.file_name());
            }
            false
        }) {
            top_marker = Some(ancestor);
        }

        if root_dirs
            .iter()
            .any(|root_dir| path::normalize(workspace.join(root_dir)) == ancestor)
        {
            // if the worskapce is the cwd do not search any higher for workspaces
            // but specify
            return Some(top_marker.unwrap_or(workspace).to_owned());
        }
        if ancestor == workspace {
            // if the workspace is the CWD, let the LSP decide what the workspace
            // is
            return top_marker
                .or_else(|| (!workspace_is_cwd).then_some(workspace))
                .map(Path::to_owned);
        }
    }

    debug_assert!(false, "workspace must be an ancestor of <file>");
    None
}

#[cfg(test)]
mod tests {
    use super::{lsp, util::*, OffsetEncoding};
    use helix_core::Rope;

    #[test]
    fn converts_lsp_pos_to_pos() {
        macro_rules! test_case {
            ($doc:expr, ($x:expr, $y:expr) => $want:expr) => {
                let doc = Rope::from($doc);
                let pos = lsp::Position::new($x, $y);
                assert_eq!($want, lsp_pos_to_pos(&doc, pos, OffsetEncoding::Utf16));
                assert_eq!($want, lsp_pos_to_pos(&doc, pos, OffsetEncoding::Utf8))
            };
        }

        test_case!("", (0, 0) => Some(0));
        test_case!("", (0, 1) => Some(0));
        test_case!("", (1, 0) => Some(0));
        test_case!("\n\n", (0, 0) => Some(0));
        test_case!("\n\n", (1, 0) => Some(1));
        test_case!("\n\n", (1, 1) => Some(1));
        test_case!("\n\n", (2, 0) => Some(2));
        test_case!("\n\n", (3, 0) => Some(2));
        test_case!("test\n\n\n\ncase", (4, 3) => Some(11));
        test_case!("test\n\n\n\ncase", (4, 4) => Some(12));
        test_case!("test\n\n\n\ncase", (4, 5) => Some(12));
        test_case!("", (u32::MAX, u32::MAX) => Some(0));
    }

    #[test]
    fn emoji_format_gh_4791() {
        use lsp::{Position, Range, TextEdit};

        let edits = vec![
            TextEdit {
                range: Range {
                    start: Position {
                        line: 0,
                        character: 1,
                    },
                    end: Position {
                        line: 1,
                        character: 0,
                    },
                },
                new_text: "\n  ".to_string(),
            },
            TextEdit {
                range: Range {
                    start: Position {
                        line: 1,
                        character: 7,
                    },
                    end: Position {
                        line: 2,
                        character: 0,
                    },
                },
                new_text: "\n  ".to_string(),
            },
        ];

        let mut source = Rope::from_str("[\n\"🇺🇸\",\n\"🎄\",\n]");

        let transaction = generate_transaction_from_edits(&source, edits, OffsetEncoding::Utf16);
        assert!(transaction.apply(&mut source));
        assert_eq!(source, "[\n  \"🇺🇸\",\n  \"🎄\",\n]");
    }

    #[test]
    fn overlapping_edits_are_dropped() {
        // Regression for issue #15514: a language server may send overlapping text edits.
        // Feeding overlapping ranges to `ChangeSet::from_changes` violates its sorted/non-overlapping
        // precondition and underflows `retain(from - last)`. The overlapping edit must be discarded here
        use lsp::{Position, Range, TextEdit};

        let edit = |sc, ec, text: &str| TextEdit {
            range: Range {
                start: Position::new(0, sc),
                end: Position::new(0, ec),
            },
            new_text: text.to_string(),
        };

        // Edits are given out of order and the second overlaps the first
        // (0..3 vs 2..4); after sorting, 2..4 starts before 0..3 ends.
        let edits = vec![edit(4, 5, "Z"), edit(0, 3, "X"), edit(2, 4, "Y")];

        let mut source = Rope::from_str("abcdef");
        let transaction = generate_transaction_from_edits(&source, edits, OffsetEncoding::Utf16);
        // Must not panic. The overlapping 2..4 edit is dropped; 0..3 -> "X",
        // retain "d" (idx 3), 4..5 -> "Z", retain "f": "abcdef" -> "XdZf".
        assert!(transaction.apply(&mut source));
        assert_eq!(source, "XdZf");
    }

    #[test]
    fn unsorted_edits_are_applied() {
        // Out-of-order (but non-overlapping) edits must all land; the sort keeps
        // every edit rather than dropping the earlier-positioned one.
        use lsp::{Position, Range, TextEdit};

        let edit = |sc, ec, text: &str| TextEdit {
            range: Range {
                start: Position::new(0, sc),
                end: Position::new(0, ec),
            },
            new_text: text.to_string(),
        };

        let edits = vec![edit(4, 5, "Y"), edit(0, 1, "X")];

        let mut source = Rope::from_str("abcdef");
        let transaction = generate_transaction_from_edits(&source, edits, OffsetEncoding::Utf16);
        assert!(transaction.apply(&mut source));
        assert_eq!(source, "XbcdYf");
    }
}
