// vs code client for the zc language server. the server is the real compiler
// running in check mode, so diagnostics, hints and highlighting follow what the
// compiler does, including syntax a program adds to itself with parse words.
//
// everything the client does is written to the output channel "ZC Language
// Server" (View > Output, then pick it from the list). zc.trace.server picks how
// much: "off" logs only problems, "messages" (the default) logs each request and
// response with its time, and "verbose" also logs the bodies. the command
// "zc: show language server log" opens the channel and "zc: restart language
// server" starts the server again.

const vscode = require('vscode');
const cp = require('child_process');
const path = require('path');
const fs = require('fs');
const { convertCodeActions } = require('./codeactions');
const { vmProcess } = require('./vmproc');
const { wasmProcess } = require('./wasmproc');
const { DiagCache, diagKey, fileStamp, sha256 } = require('./diagcache');
const { hoverContents } = require('./hover');
const { createSourceProvider } = require('./sourceprovider');

const CHANNEL = 'ZC Language Server';
const SLOW_MS = 2000;		// a request that takes longer than this is logged as slow
const INIT_WAIT_MS = 15000;	// no answer to initialize by then is logged as a stall
const CACHE_STATE = 'zc.diagnosticCache';	// the globalState entry the diagnostics cache is saved in

let out = null;
let trace = 'messages';
let proc = null;
let generation = 0;		// each spawned server has its own; a stale exit is ignored
let stopping = false;		// set while the server is being shut down on purpose
let ready = false;
let diagnostics = null;
let nextId = 1;
let nextDocVersion = 1;		// unique across close and reopen, even when the editor resets its version
let restarts = 0;
const pending = new Map();
// the diagnostics cache (client/diagcache.js). the server is asked only when a
// document's key is not in the cache, and the state below says what it holds
let store = null;			// the extension's globalState, where the cache is saved
let cache = new DiagCache(null);
let serverStamp = 'none';		// identifies the server build; it is part of every key
const docKeys = new Map();		// uri -> key of the document as it is now (null: not cacheable)
const docFiles = new Map();		// uri -> the texts of the files the document includes, sent to the server before it checks the document
const sentFiles = new Map();	// path -> the text the server was last sent for it
const docDeps = new Map();		// uri -> the files the document reads, for checking it again when one changes
const serverKeys = new Map();		// uri -> key of the text the server holds
const sentKeys = new Map();		// uri -> keys sent to the server whose diagnostics have not come back
const docVersions = new Map();		// uri -> the last revision sent, including uncacheable documents
const opened = new Set();		// uris the server has open
let saveTimer = null;
let initTimer = null;
let inbox = Buffer.alloc(0);
let stats = { requests: 0, tokens: 0, hovers: 0, diagnostics: 0, errors: 0, cacheHits: 0, cacheMisses: 0 };
const changed = new vscode.EventEmitter();

// the server's legend, in its order
const types = ['keyword', 'type', 'function', 'variable', 'string', 'number', 'operator', 'comment', 'parameter', 'property', 'macro', 'enumMember'];
const legend = new vscode.SemanticTokensLegend(types, []);

function stamp() {
    const d = new Date();
    return d.toTimeString().slice(0, 8) + '.' + String(d.getMilliseconds()).padStart(3, '0');
}

// writes one line to the channel. level is 'problem' (always shown), 'message'
// (the default) or 'verbose'
function log(level, text) {
    if (!out) return;
    const rank = { off: 0, messages: 1, verbose: 2 };
    const want = { problem: 0, message: 1, verbose: 2 }[level];
    if (want > (rank[trace] ?? 1) && level !== 'problem') return;
    out.appendLine(stamp() + ' ' + (level === 'problem' ? 'problem ' : '') + text);
}

function short(s, n) {
    s = String(s);
    return s.length > n ? s.slice(0, n) + '...(' + s.length + ' bytes)' : s;
}

// the native server when zc.lsp.serverPath names one; otherwise null, and the
// server runs in the extension's own vm (server/ holds it and its image)
function findServer() {
    const configured = vscode.workspace.getConfiguration('zc').get('lsp.serverPath');
    if (configured && fs.existsSync(configured)) return configured;
    if (configured) {
        log('problem', 'zc.lsp.serverPath does not exist: ' + configured + '; using the built-in server');
        vscode.window.showWarningMessage('zc: zc.lsp.serverPath does not exist; running the server in the extension instead');
    }
    return null;
}

function send(msg) {
    if (!proc || !proc.stdin.writable) {
        log('problem', 'dropped ' + (msg.method || 'a reply') + ': no running server');
        return;
    }
    const body = Buffer.from(JSON.stringify(msg), 'utf8');
    if (msg.method) {
        if (trace === 'verbose') log('verbose', '-> ' + msg.method + ' ' + short(JSON.stringify(msg.params), 300));
        else log('message', '-> ' + msg.method + (msg.id !== undefined ? ' #' + msg.id : ''));
    }
    proc.stdin.write(Buffer.concat([Buffer.from('Content-Length: ' + body.length + '\r\n\r\n'), body]));
}

function request(method, params) {
    return new Promise((resolve, reject) => {
        if (!proc || !proc.stdin.writable) { reject({ message: 'server unavailable' }); return; }
        const id = nextId++;
        const t0 = Date.now();
        stats.requests++;
        pending.set(id, { resolve, reject, method, t0 });
        send({ jsonrpc: '2.0', id, method, params });
    });
}

function rejectPending(message) {
    for (const p of pending.values()) p.reject({ message });
    pending.clear();
}

// lengths are in bytes, so the buffer stays bytes until a whole message is in
function onData(chunk) {
    inbox = Buffer.concat([inbox, chunk]);
    while (true) {
        const end = inbox.indexOf('\r\n\r\n');
        if (end < 0) return;
        const m = /Content-Length:\s*(\d+)/i.exec(inbox.slice(0, end).toString('ascii'));
        if (!m) {
            log('problem', 'server sent bytes without a Content-Length header: ' + short(inbox.slice(0, end).toString('utf8'), 200));
            inbox = inbox.slice(end + 4);
            continue;
        }
        const start = end + 4, n = parseInt(m[1], 10);
        if (inbox.length < start + n) return;
        const body = inbox.slice(start, start + n).toString('utf8');
        inbox = inbox.slice(start + n);
        try {
            onMessage(JSON.parse(body));
        } catch (e) {
            stats.errors++;
            log('problem', 'bad message from server (' + e.message + '): ' + short(body, 300));
        }
    }
}

function onMessage(msg) {
    if (msg.id !== undefined && pending.has(msg.id)) {
        const p = pending.get(msg.id);
        pending.delete(msg.id);
        const ms = Date.now() - p.t0;
        if (msg.error) {
            stats.errors++;
            log('problem', p.method + ' #' + msg.id + ' failed after ' + ms + ' ms: ' + short(JSON.stringify(msg.error), 300));
            p.reject(msg.error);
            return;
        }
        if (ms > SLOW_MS) log('problem', p.method + ' #' + msg.id + ' was slow: ' + ms + ' ms');
        else log('message', '<- ' + p.method + ' #' + msg.id + ' in ' + ms + ' ms');
        if (trace === 'verbose') log('verbose', '<- result ' + short(JSON.stringify(msg.result), 300));
        p.resolve(msg.result);
        return;
    }
    if (msg.method === 'textDocument/publishDiagnostics' && msg.params) {
        onPublish(msg.params.uri, msg.params.diagnostics || [], msg.params.version);
        return;
    }
    if (msg.method) log('message', '<- notification ' + msg.method + (msg.method.startsWith('window/') ? ' ' + short(JSON.stringify(msg.params), 200) : ''));
}

const isZc = doc => doc.languageId === 'zc';

function workspaceDir() {
    const f = vscode.workspace.workspaceFolders;
    return f && f[0] ? f[0].uri.fsPath : null;
}

function shortKey(key) {
    return key ? key.slice(0, 12) : 'none';
}

// the server build the cache keys are for: the native server's file, or the
// built-in server's files
function serverStampFor(bin) {
    if (bin) return fileStamp(bin);
    const dir = path.join(__dirname, '..', 'server');
    return sha256(['lsp.wasm', 'lsp.json', 'lsp.bin', 'tinyvm.js'].map(f => fileStamp(path.join(dir, f))).join(','));
}

// the key of a document as it is now, and what it reads (for checking it again when one of those changes)
function keyOf(doc) {
    const uri = doc.uri.toString();
    const r = diagKey(serverStamp, doc.getText(), doc.uri.fsPath, workspaceDir());
    docKeys.set(uri, r.key);
    docDeps.set(uri, r.deps);
    docFiles.set(uri, r.texts);
    return r.key;
}

function showDiags(uri, raw) {
    const list = raw.map(d => {
        const r = d.range;
        const sev = d.severity === 4 ? vscode.DiagnosticSeverity.Hint
            : d.severity === 3 ? vscode.DiagnosticSeverity.Information
            : d.severity === 2 ? vscode.DiagnosticSeverity.Warning
            : vscode.DiagnosticSeverity.Error;
        const diag = new vscode.Diagnostic(new vscode.Range(r.start.line, r.start.character, r.end.line, r.end.character), d.message, sev);
        diag.source = d.source || 'zc';
        // a borrow error names its owner: where it ended and where it was declared
        if (Array.isArray(d.relatedInformation)) {
            diag.relatedInformation = d.relatedInformation.filter(ri => ri && ri.location && ri.location.range).map(ri => {
                const lr = ri.location.range;
                return new vscode.DiagnosticRelatedInformation(new vscode.Location(vscode.Uri.parse(ri.location.uri || uri), new vscode.Range(lr.start.line, lr.start.character, lr.end.line, lr.end.character)), ri.message || '');
            });
        }
        return diag;
    });
    stats.diagnostics += list.length;
    log('message', 'diagnostics for ' + uri + ': ' + list.length);
    diagnostics.set(vscode.Uri.parse(uri), list);
    changed.fire();
}

// the server's answer for a text it was sent. it is cached under the key that text had,
// and shown only when that is still the document's key
function onPublish(uri, raw, version) {
    if (!opened.has(uri)) return;
    const q = sentKeys.get(uri);
    const index = q ? (version === undefined ? 0 : q.findIndex(entry => entry.version === version)) : -1;
    if (!q || !q.length || index < 0) {
        log('message', 'unrequested diagnostics for ' + uri + ': ignored');
        return;
    }
    const { key, version: sentVersion } = q.splice(index, 1)[0];
    if (key && cache.put(key, raw)) saveCacheSoon();
    if (docKeys.get(uri) === key && (key || docVersions.get(uri) === sentVersion)) showDiags(uri, raw);
    else log('message', 'diagnostics for ' + uri + ' under an old key: not shown');
}

// shows the cached diagnostics for doc when its key is in the cache; true when it did
function showCached(doc) {
    const uri = doc.uri.toString();
    const key = keyOf(doc);
    const hit = cache.get(key);
    if (!hit) return false;
    stats.cacheHits++;
    log('message', 'diagnostics for ' + uri + ' from the cache (' + shortKey(key) + ')');
    showDiags(uri, hit);
    return true;
}

// the server of this extension has no files of its own: it is sent the text of every file a document
// includes, keyed by its full path, and looks an include up there. only what changed is sent again.
function sendIncludes(uri) {
    const texts = docFiles.get(uri);
    if (!texts) return;
    for (const [p, text] of texts) {
        if (sentFiles.get(p) === text) continue;
        sentFiles.set(p, text);
        send({ jsonrpc: '2.0', method: 'zc/file', params: { path: p.split(path.sep).join('/'), text } });
    }
}
// sends doc's text to the server: didOpen the first time, didChange after that
function sendDoc(doc, key) {
    if (!proc || !proc.stdin.writable || !ready) return false;
    const uri = doc.uri.toString();
    const q = sentKeys.get(uri) || [];
    const version = nextDocVersion++;
    docVersions.set(uri, version);
    q.push({ key, version });
    sentKeys.set(uri, q);
    serverKeys.set(uri, key);
    sendIncludes(uri);
    if (!opened.has(uri)) {
        opened.add(uri);
        send({ jsonrpc: '2.0', method: 'textDocument/didOpen', params: { textDocument: { uri, languageId: 'zc', version, text: doc.getText() } } });
    } else {
        send({ jsonrpc: '2.0', method: 'textDocument/didChange', params: { textDocument: { uri, version }, contentChanges: [{ text: doc.getText() }] } });
    }
    return true;
}

// brings doc's diagnostics up to date. a key in the cache answers without the server, which
// then only hears the text when something asks it about the document (see ensureServer).
// otherwise the server gets the text and its answer is cached under the key
function syncDoc(doc) {
    if (!isZc(doc)) return;
    const uri = doc.uri.toString();
    if (showCached(doc)) return;
    const key = docKeys.get(uri);
    if (key !== null && key !== undefined && serverKeys.get(uri) === key && opened.has(uri)) return;
    if (!ready) { log('message', 'not sending ' + uri + ' yet: server not ready'); return; }
    stats.cacheMisses++;
    sendDoc(doc, key === undefined ? keyOf(doc) : key);
}

// the server must hold doc's current text before a request about it (hover, tokens)
function ensureServer(doc) {
    if (!isZc(doc) || !ready) return false;
    const uri = doc.uri.toString();
    const key = keyOf(doc);
    if (key !== null && serverKeys.get(uri) === key && opened.has(uri)) return true;
    return sendDoc(doc, key);
}

// a file another open document reads changed on disk: that document is checked again
function resyncDependents(fsPath) {
    for (const doc of vscode.workspace.textDocuments) {
        if (!isZc(doc) || doc.uri.fsPath === fsPath) continue;
        const deps = docDeps.get(doc.uri.toString());
        if (deps && deps.includes(fsPath)) {
            log('message', 'included file changed: checking ' + doc.uri.toString() + ' again');
            syncDoc(doc);
        }
    }
}

// the cache is written after a short pause, so typing does not write it on every key
function saveCacheSoon() {
    if (!store) return;
    if (saveTimer) clearTimeout(saveTimer);
    saveTimer = setTimeout(() => {
        saveTimer = null;
        try {
            Promise.resolve(store.update(CACHE_STATE, cache.toJSON())).catch(e => log('problem', 'could not save the diagnostics cache: ' + e.message));
        } catch (e) {
            log('problem', 'could not save the diagnostics cache: ' + e.message);
        }
    }, 500);
}

// the server's answer to initialize is the first sign it works; without one the
// log says so, and the usual cause is a server that is still loading
// a native server that does not answer is stopped and the built-in server runs
// instead. a built-in server that does not answer is only logged
function watchInit(gen, native) {
    if (initTimer) clearTimeout(initTimer);
    initTimer = setTimeout(() => {
        initTimer = null;
        if (gen !== generation || ready || stopping || !proc) return;
        if (native) {
            log('problem', 'the native server at ' + zcServerPath() + ' did not answer initialize after ' + (INIT_WAIT_MS / 1000) + ' s; using the built-in server. clear zc.lsp.serverPath to stop seeing this');
            forceBuiltin = true;
            generation++;
            if (proc) { try { proc.kill(); } catch (e) { /* already gone */ } }
            proc = null;
            rejectPending('server replaced after initialize timeout');
            startServer();
        } else {
            log('problem', 'no answer to initialize after ' + (INIT_WAIT_MS / 1000) + ' s; the server is still starting or has stalled');
        }
    }, INIT_WAIT_MS);
}

function zcServerPath() {
    return vscode.workspace.getConfiguration('zc').get('lsp.serverPath') || '';
}

// forceBuiltin is set when a native server did not answer: the built-in one runs instead
let forceBuiltin = false;

function startServer() {
    const gen = ++generation;
    stopping = false;
    const bin = forceBuiltin ? null : findServer();
    ready = false;
    inbox = Buffer.alloc(0);
    // a new server holds no documents and has answered nothing yet
    opened.clear();
    serverKeys.clear();
    sentKeys.clear();
    sentFiles.clear();
    docVersions.clear();
    serverStamp = serverStampFor(bin);
    const t0 = Date.now();
    try {
        if (bin) {
            log('message', 'starting the native server: ' + bin);
            proc = cp.spawn(bin, [], { cwd: vscode.workspace.workspaceFolders ? vscode.workspace.workspaceFolders[0].uri.fsPath : undefined, stdio: ['pipe', 'pipe', 'pipe'] });
        } else {
            const dir = path.join(__dirname, '..', 'server');
            const wasm = path.join(dir, 'lsp.wasm');
            // the wasm server is the fast one; the javascript vm is kept for a build without it
            if (fs.existsSync(wasm)) {
                log('message', 'starting the built-in server (wasm) from ' + wasm);
                proc = wasmProcess(wasm, { log: (level, text) => log(level, 'wasm: ' + text) });
            } else {
                log('message', 'starting the built-in server (javascript vm) from ' + dir);
                proc = vmProcess(dir, { log: (level, text) => log(level, 'vm: ' + text) });
            }
            log('message', 'built-in server started in ' + (Date.now() - t0) + ' ms');
        }
    } catch (e) {
        log('problem', 'could not start the server: ' + e.stack);
        vscode.window.showErrorMessage('zc: could not start the language server: ' + e.message + ' (see the ZC Language Server output)');
        return;
    }
    proc.stdout.on('data', data => { if (gen === generation) onData(data); });
    proc.stderr.on('data', d => log('problem', 'server stderr: ' + short(d.toString(), 500)));
    proc.on('error', err => {
        if (gen !== generation) return;
        ready = false;
        rejectPending('server process error: ' + err.message);
        log('problem', 'server process error: ' + err.stack);
        vscode.window.showErrorMessage('zc: could not launch the language server: ' + err.message + ' (see the ZC Language Server output)');
    });
    proc.on('exit', (code, signal) => {
        if (gen !== generation) return;
        if (initTimer) { clearTimeout(initTimer); initTimer = null; }
        if (stopping) { log('message', 'server stopped (code ' + code + ')'); ready = false; proc = null; rejectPending('server stopped'); return; }
        log('problem', 'server exited with code ' + code + (signal ? ' signal ' + signal : '') + ' after ' + (Date.now() - t0) + ' ms');
        ready = false;
        proc = null;
        rejectPending('server exited');
        // a crash restarts the server, and the open documents are sent again once it is up
        if (restarts < 5) {
            restarts++;
            log('problem', 'restarting the server (' + restarts + ' of 5)');
            setTimeout(() => { if (gen === generation) startServer(); }, 300);
        } else {
            log('problem', 'giving up after 5 restarts; use "zc: restart language server" to try again');
        }
    });
    watchInit(gen, !!bin);
    request('initialize', { processId: process.pid, rootUri: workspaceDir() ? vscode.Uri.file(workspaceDir()).toString() : null, capabilities: {} }).then(res => {
        if (gen !== generation || stopping || !proc) return;
        if (initTimer) { clearTimeout(initTimer); initTimer = null; }
        const caps = res && res.capabilities ? Object.keys(res.capabilities) : [];
        log('message', 'server ready: capabilities ' + caps.join(', ') + ' (initialized in ' + (Date.now() - t0) + ' ms)');
        send({ jsonrpc: '2.0', method: 'initialized', params: {} });
        ready = true;
        const docs = vscode.workspace.textDocuments;
        log('message', 'syncing ' + docs.filter(isZc).length + ' open zc document(s)');
        docs.forEach(syncDoc);
    }).catch(err => log('problem', 'initialize failed: ' + short(JSON.stringify(err), 300)));
}

function stopServer() {
    if (initTimer) { clearTimeout(initTimer); initTimer = null; }
    if (!proc) { rejectPending('server stopped'); return; }
    const p = proc;
    log('message', 'stopping the server');
    stopping = true;
    ready = false;
    rejectPending('server stopping');
    request('shutdown', null).catch(() => {});
    send({ jsonrpc: '2.0', method: 'exit' });
    setTimeout(() => { if (proc === p) { proc.kill(); proc = null; ready = false; rejectPending('server stopped'); } }, 500);
}

function activate(context) {
    out = vscode.window.createOutputChannel(CHANNEL);
    context.subscriptions.push(out);
    trace = vscode.workspace.getConfiguration('zc').get('trace.server') || 'messages';
    log('message', 'extension activated; trace level ' + trace);

    diagnostics = vscode.languages.createDiagnosticCollection('zc');
    context.subscriptions.push(diagnostics);
    store = context.globalState;
    cache = new DiagCache(store ? store.get(CACHE_STATE) : null);
    // the stamp is taken without findServer, which would warn about a missing server path a second time
    const configured = vscode.workspace.getConfiguration('zc').get('lsp.serverPath');
    serverStamp = serverStampFor(configured && fs.existsSync(configured) ? configured : null);
    // the open documents whose diagnostics are cached show them before the server starts
    vscode.workspace.textDocuments.forEach(d => { if (isZc(d)) showCached(d); });
    startServer();

    // a .zc file changed on disk (saved elsewhere, checked out, deleted): the open documents that include it are checked again
    const watcher = vscode.workspace.createFileSystemWatcher('**/*.zc');
    const recheck = uri => resyncDependents(uri.fsPath);
    context.subscriptions.push(watcher, watcher.onDidChange(recheck), watcher.onDidCreate(recheck), watcher.onDidDelete(recheck));

    context.subscriptions.push(
        vscode.workspace.onDidChangeConfiguration(e => {
            if (e.affectsConfiguration('zc.trace.server')) {
                trace = vscode.workspace.getConfiguration('zc').get('trace.server') || 'messages';
                log('message', 'trace level is now ' + trace);
            }
        }),
        vscode.workspace.onDidOpenTextDocument(syncDoc),
        vscode.workspace.onDidChangeTextDocument(e => syncDoc(e.document)),
        vscode.workspace.onDidSaveTextDocument(doc => {
            if (!isZc(doc)) return;
            syncDoc(doc);
            resyncDependents(doc.uri.fsPath);
        }),
        vscode.workspace.onDidCloseTextDocument(doc => {
            if (!isZc(doc)) return;
            const uri = doc.uri.toString();
            diagnostics.delete(doc.uri);
            docKeys.delete(uri);
            docDeps.delete(uri);
            serverKeys.delete(uri);
            sentKeys.delete(uri);
            docVersions.delete(uri);
            if (opened.delete(uri) && ready) send({ jsonrpc: '2.0', method: 'textDocument/didClose', params: { textDocument: { uri } } });
        }),
        vscode.commands.registerCommand('zc.showLog', () => out.show(true)),
        vscode.commands.registerCommand('zc.restart', () => {
            log('message', 'restarting the server by request');
            restarts = 0;
            stopServer();
            setTimeout(startServer, 600);
        })
    );

    // highlighting: the server's tokens, on top of the grammar in syntaxes/
    const tokens = {
        onDidChangeSemanticTokens: changed.event,
        async provideDocumentSemanticTokens(doc) {
            if (!isZc(doc)) return null;
            if (!ready) { log('message', 'no semantic tokens for ' + doc.uri.toString() + ': server not ready'); return null; }
            const t0 = Date.now();
            ensureServer(doc);
            try {
                const res = await request('textDocument/semanticTokens/full', { textDocument: { uri: doc.uri.toString() } });
                if (!res || !res.data) { log('message', 'semantic tokens: none for ' + doc.uri.toString()); return null; }
                const builder = new vscode.SemanticTokensBuilder(legend);
                let line = 0, col = 0, count = 0;
                for (let i = 0; i < res.data.length; i += 5) {
                    line += res.data[i];
                    col = res.data[i] === 0 ? col + res.data[i + 1] : res.data[i + 1];
                    builder.push(line, col, res.data[i + 2], res.data[i + 3], res.data[i + 4]);
                    count++;
                }
                stats.tokens += count;
                log('message', 'semantic tokens: ' + count + ' for ' + doc.uri.toString() + ' in ' + (Date.now() - t0) + ' ms');
                return builder.build();
            } catch (err) {
                log('problem', 'semantic tokens failed for ' + doc.uri.toString() + ': ' + short(JSON.stringify(err), 300));
                return null;
            }
        }
    };
    context.subscriptions.push(vscode.languages.registerDocumentSemanticTokensProvider({ language: 'zc' }, tokens, legend));

    // hover: the docs the compiler stores for a name (docs in the image)
    const hover = {
        async provideHover(doc, position) {
            if (!isZc(doc) || !ready) return null;
            ensureServer(doc);
            try {
                const res = await request('textDocument/hover', { textDocument: { uri: doc.uri.toString() }, position: { line: position.line, character: position.character } });
                stats.hovers++;
                const contents = hoverContents(vscode, res && res.contents);
                log('message', 'hover at ' + position.line + ':' + position.character + ': ' + (contents.length ? 'text' : 'nothing'));
                return contents.length ? new vscode.Hover(contents) : null;
            } catch (err) {
                return null;
            }
        }
    };
    context.subscriptions.push(vscode.languages.registerHoverProvider({ language: 'zc' }, hover));

    // the sources the server carries (the runtime, compiler, standard library and icon module): shown read only at tinyvm:/NAME.zc
    // when go to definition lands on a built-in. the text comes from the server, so it is the code the editor's checks run on
    context.subscriptions.push(vscode.workspace.registerTextDocumentContentProvider('tinyvm', createSourceProvider(request, () => ready)));

    // completions refresh as the prefix changes; deprecated lifetime entries stay visible at the end.
    context.subscriptions.push(vscode.languages.registerCompletionItemProvider({ language: 'zc' }, {
        async provideCompletionItems(doc, position, token) {
            if (!isZc(doc) || !ready || token.isCancellationRequested) return null;
            ensureServer(doc);
            const version = doc.version;
            try {
                const res = await request('textDocument/completion', { textDocument: { uri: doc.uri.toString() }, position: { line: position.line, character: position.character } });
                if (!res || token.isCancellationRequested || doc.version !== version) return null;
                const items = (res.items || []).map(c => {
                    const item = new vscode.CompletionItem(c.label, c.kind ? c.kind - 1 : vscode.CompletionItemKind.Variable);
                    item.detail = c.detail;
                    item.sortText = c.sortText;
                    item.filterText = c.filterText;
                    if (c.tags && c.tags.includes(1)) item.tags = [vscode.CompletionItemTag.Deprecated];
                    if (c.documentation) {
                        item.documentation = new vscode.MarkdownString(c.documentation.value || c.documentation);
                        item.documentation.isTrusted = false;
                    }
                    if (c.textEdit) {
                        const r = c.textEdit.range;
                        item.range = new vscode.Range(r.start.line, r.start.character, r.end.line, r.end.character);
                        item.insertText = c.textEdit.newText;
                    }
                    return item;
                });
                return new vscode.CompletionList(items, !!res.isIncomplete);
            } catch (err) { return null; }
        }
    }, '.', '>'));

    // compiler-backed import fixes use the same document version as their diagnostics.
    if (vscode.languages.registerCodeActionsProvider) context.subscriptions.push(vscode.languages.registerCodeActionsProvider({ language: 'zc' }, {
        async provideCodeActions(doc, range, actionContext, token) {
            if (!isZc(doc) || !ready || token.isCancellationRequested) return [];
            ensureServer(doc);
            const version = doc.version;
            const serverVersion = docVersions.get(doc.uri.toString());
            try {
                const results = await request('textDocument/codeAction', {
                    textDocument: { uri: doc.uri.toString() },
                    range: { start: { line: range.start.line, character: range.start.character }, end: { line: range.end.line, character: range.end.character } },
                    context: { diagnostics: [] }
                });
                if (token.isCancellationRequested || doc.version !== version || docVersions.get(doc.uri.toString()) !== serverVersion) return [];
                return convertCodeActions(vscode, results, doc, serverVersion);
            } catch (err) { return []; }
        }
    }, { providedCodeActionKinds: [vscode.CodeActionKind.QuickFix] }));

    // go to definition and find references: the compiler's own records, including names from included files
    const locations = (res) => (Array.isArray(res) ? res : []).map(l => new vscode.Location(vscode.Uri.parse(l.uri),
        new vscode.Range(l.range.start.line, l.range.start.character, l.range.end.line, l.range.end.character)));
    context.subscriptions.push(vscode.languages.registerDefinitionProvider({ language: 'zc' }, {
        async provideDefinition(doc, position) {
            if (!isZc(doc) || !ready) return null;
            ensureServer(doc);
            try {
                return locations(await request('textDocument/definition', { textDocument: { uri: doc.uri.toString() }, position: { line: position.line, character: position.character } }));
            } catch (err) { return null; }
        }
    }));
    // formatting: the server's pretty-printer, with the editor's tab settings (a .zcformat file overrides them)
    context.subscriptions.push(vscode.languages.registerDocumentFormattingEditProvider({ language: 'zc' }, {
        async provideDocumentFormattingEdits(doc, options) {
            if (!isZc(doc) || !ready) return [];
            ensureServer(doc);
            try {
                const res = await request('textDocument/formatting', { textDocument: { uri: doc.uri.toString() }, options: { tabSize: options.tabSize, insertSpaces: options.insertSpaces } });
                return (Array.isArray(res) ? res : []).map(e => vscode.TextEdit.replace(
                    new vscode.Range(e.range.start.line, e.range.start.character, e.range.end.line, e.range.end.character), e.newText));
            } catch (err) { return []; }
        }
    }));
    context.subscriptions.push(vscode.languages.registerReferenceProvider({ language: 'zc' }, {
        async provideReferences(doc, position, refContext) {
            if (!isZc(doc) || !ready) return null;
            ensureServer(doc);
            try {
                return locations(await request('textDocument/references', { textDocument: { uri: doc.uri.toString() }, position: { line: position.line, character: position.character }, context: { includeDeclaration: !!refContext.includeDeclaration } }));
            } catch (err) { return null; }
        }
    }));
}

function deactivate() {
    log('message', 'extension deactivated: ' + JSON.stringify(stats));
    stopServer();
}

module.exports = { activate, deactivate };