//! Independent regression probe of the stock native TypeScript API contract,
//! speaking framed JSON-RPC directly to the backend instead of reusing the
//! adapter under test. Set AVRIL_TEST_TYPESCRIPT to the backend's absolute
//! path; the probe is skipped otherwise.

use std::cell::RefCell;
use std::collections::{BTreeMap, HashMap};
use std::io::{BufRead, BufReader, Write};
use std::path::{Path, PathBuf};
use std::process::{Child, ChildStdin, Command, Stdio};
use std::rc::Rc;
use std::sync::Mutex;
use std::sync::mpsc::{Receiver, channel};
use std::time::{Duration, Instant};

use serde_json::{Value, json};

fn backend() -> Option<PathBuf> {
    let path = std::env::var_os("AVRIL_TEST_TYPESCRIPT")?;
    if path.is_empty() {
        return None;
    }
    Some(PathBuf::from(path))
}

fn write_frame(writer: &mut impl Write, message: &Value) -> std::io::Result<()> {
    let body = serde_json::to_vec(message).unwrap();
    write!(writer, "Content-Length: {}\r\n\r\n", body.len())?;
    writer.write_all(&body)?;
    writer.flush()
}

fn read_frame(reader: &mut impl BufRead) -> std::io::Result<Option<Value>> {
    let mut length = None;
    loop {
        let mut line = String::new();
        if reader.read_line(&mut line)? == 0 {
            return Ok(None);
        }
        let line = line.trim_end_matches(['\r', '\n']);
        if line.is_empty() {
            break;
        }
        if let Some((name, value)) = line.split_once(':')
            && name.trim().eq_ignore_ascii_case("Content-Length")
        {
            length = Some(value.trim().parse::<usize>().unwrap());
        }
    }
    let mut body = vec![0; length.unwrap()];
    reader.read_exact(&mut body)?;
    Ok(Some(serde_json::from_slice(&body).unwrap()))
}

#[derive(Debug)]
enum CallError {
    Rpc { code: i64, message: String },
    Failed(String),
}

impl std::fmt::Display for CallError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            CallError::Rpc { code, message } => write!(f, "RPC {code}: {message}"),
            CallError::Failed(message) => write!(f, "{message}"),
        }
    }
}

type Callback = Box<dyn FnMut(&Value) -> Result<Value, String>>;

struct ApiServer {
    child: Child,
    stdin: Option<Mutex<ChildStdin>>,
    messages: Receiver<Value>,
    callbacks: HashMap<String, Callback>,
    next_id: u64,
    failed: Option<String>,
}

impl ApiServer {
    fn start(binary: &Path, callbacks: &[&str]) -> ApiServer {
        let mut child = Command::new(binary)
            .env_clear()
            .args([
                "--api",
                "--async",
                "--cwd",
                "/avril-lsp",
                "--callbacks",
                &callbacks.join(","),
            ])
            .stdin(Stdio::piped())
            .stdout(Stdio::piped())
            .stderr(Stdio::inherit())
            .spawn()
            .unwrap();
        let stdin = Some(Mutex::new(child.stdin.take().unwrap()));
        let mut stdout = BufReader::new(child.stdout.take().unwrap());
        let (tx, messages) = channel();
        std::thread::spawn(move || {
            while let Ok(Some(message)) = read_frame(&mut stdout) {
                if tx.send(message).is_err() {
                    return;
                }
            }
        });
        ApiServer {
            child,
            stdin,
            messages,
            callbacks: HashMap::new(),
            next_id: 0,
            failed: None,
        }
    }

    fn send(&self, message: &Value) {
        write_frame(&mut *self.stdin.as_ref().unwrap().lock().unwrap(), message).unwrap();
    }

    fn call(&mut self, method: &str, params: Value) -> Result<Value, CallError> {
        if let Some(error) = &self.failed {
            return Err(CallError::Failed(error.clone()));
        }
        self.next_id += 1;
        let id = self.next_id;
        self.send(&json!({"id": id, "method": method, "params": params}));
        let deadline = Instant::now() + Duration::from_secs(30);
        loop {
            let remaining = deadline.saturating_duration_since(Instant::now());
            if remaining.is_zero() {
                self.failed = Some(format!("Timed out waiting for {method}"));
                return Err(CallError::Failed(self.failed.clone().unwrap()));
            }
            match self.messages.recv_timeout(remaining) {
                Ok(message) => {
                    if let Some(callback_method) = message["method"].as_str() {
                        // Callbacks may arrive while a request is in flight;
                        // answering them inline keeps the reader progressing.
                        let callback_id = message["id"].clone();
                        let response = match self.callbacks.get_mut(callback_method) {
                            Some(callback) => match callback(&message["params"]) {
                                Ok(result) => json!({"id": callback_id, "result": result}),
                                Err(error) => json!({
                                    "id": callback_id,
                                    "error": {"code": -32603, "message": error}
                                }),
                            },
                            None => json!({
                                "id": callback_id,
                                "error": {
                                    "code": -32603,
                                    "message": format!("Unknown callback: {callback_method}")
                                }
                            }),
                        };
                        self.send(&response);
                    } else if message["id"].as_u64() == Some(id) {
                        if let Some(error) = message.get("error") {
                            return Err(CallError::Rpc {
                                code: error["code"].as_i64().unwrap_or_default(),
                                message: error["message"].as_str().unwrap_or_default().to_owned(),
                            });
                        }
                        return Ok(message["result"].clone());
                    }
                }
                Err(_) => {
                    self.failed = Some("API server closed stdout".into());
                    return Err(CallError::Failed(self.failed.clone().unwrap()));
                }
            }
        }
    }

    fn close(mut self) {
        drop(self.stdin.take());
        let deadline = Instant::now() + Duration::from_secs(2);
        loop {
            match self.child.try_wait().unwrap() {
                Some(status) => {
                    assert!(status.success(), "API server exited with {status}");
                    return;
                }
                None if Instant::now() >= deadline => {
                    self.child.kill().unwrap();
                    self.child.wait().unwrap();
                    panic!("API server did not exit");
                }
                None => std::thread::sleep(Duration::from_millis(10)),
            }
        }
    }
}

impl Drop for ApiServer {
    fn drop(&mut self) {
        let _ = self.child.kill();
        let _ = self.child.wait();
    }
}

fn version(binary: &Path) -> String {
    let output = Command::new(binary).arg("--version").output().unwrap();
    assert!(output.status.success(), "Cannot run backend");
    String::from_utf8(output.stdout).unwrap().trim().to_owned()
}

#[test]
fn capabilities() {
    let Some(binary) = backend() else {
        eprintln!("skipping: AVRIL_TEST_TYPESCRIPT is not set");
        return;
    };
    println!("{}", version(&binary));
    let mut api = ApiServer::start(&binary, &[]);
    println!("initialize: {}", api.call("initialize", json!({})).unwrap());
    match api.call("createModuleResolver", json!({"compilerOptions": {}})) {
        Ok(resolver) => {
            api.call("releaseModuleResolver", json!({"resolver": resolver}))
                .unwrap();
            println!("Custom module-resolution API: available");
        }
        Err(CallError::Rpc { message, .. }) => {
            assert!(
                message.contains("unknown API method \"createModuleResolver\""),
                "Unexpected capability failure: {message}"
            );
            println!("Custom module-resolution API: unavailable");
        }
        Err(error) => panic!("Unexpected capability failure: {error}"),
    }
    api.close();
}

struct Fixture {
    original_to_file: BTreeMap<String, String>,
    directory_to_original: BTreeMap<String, String>,
    files: BTreeMap<String, String>,
}

impl Fixture {
    fn add(&mut self, original: &str, source: &str) -> String {
        let extension = if original.ends_with(".d.ts") {
            ".d.ts"
        } else if original.ends_with(".tsx") {
            ".tsx"
        } else {
            ".ts"
        };
        let directory = format!("/avril-lsp/modules/{}", self.original_to_file.len());
        let file = format!("{directory}/source{extension}");
        self.original_to_file
            .insert(original.to_owned(), file.clone());
        self.directory_to_original
            .insert(directory, original.to_owned());
        self.files.insert(file.clone(), source.to_owned());
        file
    }
}

fn utf16_index(line: &str, byte_index: usize) -> usize {
    line[..byte_index].encode_utf16().count()
}

fn layer(files: Vec<(String, String)>) -> Value {
    let mut map = serde_json::Map::new();
    for (name, text) in files {
        map.insert(name, json!(text));
    }
    Value::Object(map)
}

#[test]
fn native_api_contract() {
    let Some(binary) = backend() else {
        eprintln!("skipping: AVRIL_TEST_TYPESCRIPT is not set");
        return;
    };
    println!("{}", version(&binary));
    let lib_directory = binary.parent().unwrap().to_path_buf();
    let fs_callbacks = [
        "readFile",
        "fileExists",
        "directoryExists",
        "getAccessibleEntries",
    ];
    let mut callback_names: Vec<String> = fs_callbacks.iter().map(ToString::to_string).collect();
    callback_names.extend(
        [
            "realpath:identity",
            "stat:fakeStat",
            "writeFile:error",
            "removeFile:error",
        ]
        .iter()
        .map(ToString::to_string),
    );
    let callback_refs: Vec<&str> = callback_names.iter().map(String::as_str).collect();
    let mut api = ApiServer::start(&binary, &callback_refs);

    let fs_calls = Rc::new(RefCell::new(Vec::<(String, String, bool)>::new()));
    for method in fs_callbacks {
        let fs_calls = fs_calls.clone();
        let lib_directory = lib_directory.clone();
        api.callbacks.insert(
            method.to_owned(),
            Box::new(move |params| {
                let path = params
                    .as_str()
                    .ok_or_else(|| format!("Unexpected filesystem callback: {method}"))?;
                let library_name = path
                    .strip_prefix(&format!("{}/", lib_directory.display()))
                    .filter(|name| {
                        name.starts_with("lib.")
                            && name.ends_with(".d.ts")
                            && name
                                .bytes()
                                .all(|b| b.is_ascii_alphanumeric() || matches!(b, b'.' | b'-'))
                    });
                let allowed = library_name.is_some()
                    || Path::new(path) == lib_directory
                    || path.starts_with("bundled:///libs/")
                    || path == "bundled:///libs";
                fs_calls
                    .borrow_mut()
                    .push((method.to_owned(), path.to_owned(), allowed));
                if allowed {
                    return Ok(json!({"kind": "useOS"}));
                }
                if method == "readFile" {
                    return Ok(json!({"kind": "missing"}));
                }
                Ok(json!({
                    "kind": "value",
                    "value": if method == "getAccessibleEntries" {
                        json!({"files": [], "directories": []})
                    } else {
                        json!(false)
                    }
                }))
            }),
        );
    }

    let mut snapshots: Vec<u64> = Vec::new();
    let mut resolvers: Vec<u64> = Vec::new();
    let mut passed: Vec<String> = Vec::new();
    let pass = |passed: &mut Vec<String>, message: &str| {
        passed.push(message.to_owned());
        println!("PASS {message}");
    };

    println!("initialize: {}", api.call("initialize", json!({})).unwrap());
    let raw_options = json!({
        "strict": true, "noEmit": true, "skipLibCheck": true, "target": "esnext",
        "module": "esnext", "moduleResolution": "bundler",
        "allowImportingTsExtensions": true, "jsx": "react-jsx",
        "jsxImportSource": "@fixture/ui", "types": []
    });
    let mut fixture = Fixture {
        original_to_file: BTreeMap::new(),
        directory_to_original: BTreeMap::new(),
        files: BTreeMap::new(),
    };
    let main_uri = "file:///workspace/app/main.tsx";
    let main_source = [
        "import { process } from \"avril:std\";",
        "import { answer } from \"jsr:@fixture/data\";",
        "import { label } from \"./local.ts\";",
        "const emoji = \"😀\"; const wrong: number = \"bad\";",
        "const view = <panel count=\"wrong\" />;",
        "process.args.push(\"x\");",
        "export const result = { answer, label, view };",
    ]
    .join("\n");
    let main = fixture.add(main_uri, &main_source);
    let a_uri = "file:///workspace/app/a.ts";
    let b_uri = "file:///workspace/app/b.ts";
    let a = fixture.add(
        a_uri,
        "import { value } from \"scoped\"; export const result: \"A\" = value;",
    );
    let b = fixture.add(
        b_uri,
        "import { value } from \"scoped\"; export const result: \"B\" = value;",
    );
    let completion_source = "import { process } from \"avril:std\"; process.args;";
    let completion = fixture.add("file:///workspace/app/completion.ts", completion_source);
    fixture.add(
        "file:///workspace/deps/a.ts",
        "export const value = \"A\" as const;",
    );
    fixture.add(
        "file:///workspace/deps/b.ts",
        "export const value = \"B\" as const;",
    );
    fixture.add(
        "file:///workspace/app/local.ts",
        "export const label = \"local\";",
    );
    fixture.add(
        "https://jsr.io/@fixture/data/1.0.0/mod.d.ts",
        "export declare const answer: 42;",
    );
    fixture.add(
        "file:///workspace/ui/jsx-runtime.d.ts",
        "\nexport namespace JSX {\n  interface Element {}\n  interface IntrinsicElements { panel: { count: number } }\n}\nexport declare function jsx(...args: unknown[]): JSX.Element;\nexport declare const jsxs: typeof jsx;\nexport declare const Fragment: unique symbol;\n",
    );

    // The production catalog includes both handwritten and generated declarations.
    let mut roots = vec![main.clone(), a.clone(), b.clone(), completion.clone()];
    for (name, text) in avril_runtime::stdlib::declarations() {
        roots.push(fixture.add(&format!("avril:///lib/{name}"), text));
    }

    let fixture = Rc::new(RefCell::new(fixture));
    let calls = Rc::new(RefCell::new(Vec::<Value>::new()));
    let parse_options = |api: &mut ApiServer, compiler_options: &Value, roots: &[String]| {
        // The wire protocol wants normalized enum values, not tsconfig spellings.
        let parsed = api
            .call(
                "parseJsonConfigFileContent",
                json!({
                    "json": {"compilerOptions": compiler_options, "files": roots},
                    "configDirectory": "/avril-lsp"
                }),
            )
            .unwrap();
        assert!(
            parsed["errors"].as_array().unwrap().is_empty(),
            "Invalid compiler options: {}",
            parsed["errors"]
        );
        parsed["options"].clone()
    };
    let options = parse_options(&mut api, &raw_options, &roots);

    // Resolution policy is pinned to the resolver, including for older snapshots.
    let register_resolver = |api: &mut ApiServer,
                             resolvers: &mut Vec<u64>,
                             calls: &Rc<RefCell<Vec<Value>>>,
                             fixture: &Rc<RefCell<Fixture>>,
                             compiler_options: &Value,
                             swap_scopes: bool|
     -> u64 {
        let callback = format!("avril/resolve/{}", resolvers.len());
        let calls = calls.clone();
        let fixture = fixture.clone();
        api.callbacks.insert(
            callback.clone(),
            Box::new(move |params| {
                calls.borrow_mut().push(params.clone());
                let fixture = fixture.borrow();
                let original = fixture
                    .directory_to_original
                    .get(params["containingDirectory"].as_str().unwrap());
                let resolved = match params["moduleName"].as_str().unwrap() {
                    "scoped" => {
                        let (dep_a, dep_b) = (
                            &fixture.original_to_file["file:///workspace/deps/a.ts"],
                            &fixture.original_to_file["file:///workspace/deps/b.ts"],
                        );
                        match (original.map(String::as_str), swap_scopes) {
                            (Some("file:///workspace/app/a.ts"), false) => Some(dep_a),
                            (Some("file:///workspace/app/a.ts"), true) => Some(dep_b),
                            (Some("file:///workspace/app/b.ts"), false) => Some(dep_b),
                            (Some("file:///workspace/app/b.ts"), true) => Some(dep_a),
                            _ => None,
                        }
                    }
                    "jsr:@fixture/data" => Some(
                        &fixture.original_to_file["https://jsr.io/@fixture/data/1.0.0/mod.d.ts"],
                    ),
                    "@fixture/ui/jsx-runtime" => {
                        Some(&fixture.original_to_file["file:///workspace/ui/jsx-runtime.d.ts"])
                    }
                    "./local.ts"
                        if original.map(String::as_str)
                            == Some("file:///workspace/app/main.tsx") =>
                    {
                        Some(&fixture.original_to_file["file:///workspace/app/local.ts"])
                    }
                    _ => None,
                };
                Ok(match resolved {
                    Some(file) => json!({"resolvedFileName": file}),
                    None => Value::Null,
                })
            }),
        );
        let id = api
            .call(
                "createModuleResolver",
                json!({
                    "compilerOptions": compiler_options,
                    "resolveModuleNameCallback": callback
                }),
            )
            .unwrap()
            .as_u64()
            .unwrap();
        resolvers.push(id);
        id
    };

    let (main_f, a_f, b_f) = (main.clone(), a.clone(), b.clone());
    let files_snapshot = fixture.borrow().files.clone();
    let mut resolver_id =
        register_resolver(&mut api, &mut resolvers, &calls, &fixture, &options, false);
    let _ = resolver_id;
    let mut snapshot = api
        .call(
            "createSnapshot",
            json!({
                "fileSystem": {"kind": "layer", "files": files_snapshot},
                "createPrograms": [{
                    "rootFiles": roots.clone(), "compilerOptions": options,
                    "options": {"moduleResolver": resolver_id}
                }]
            }),
        )
        .unwrap();
    snapshots.push(snapshot["snapshot"].as_u64().unwrap());
    let project = snapshot["operation"]["createdPrograms"][0]
        .as_str()
        .unwrap()
        .to_owned();
    assert!(
        snapshot["projects"][0]["parsedCommandLine"]["errors"]
            .as_array()
            .unwrap()
            .is_empty(),
        "Invalid compiler options"
    );
    let initial = snapshot.clone();

    // Helper closures over the API.
    macro_rules! diagnostics {
        ($snapshot:expr, $selected:expr) => {
            api.call(
                "getSemanticDiagnostics",
                json!({
                    "snapshot": $snapshot["snapshot"], "project": project,
                    "files": $selected
                }),
            )
            .unwrap()
        };
    }

    let first = diagnostics!(snapshot, [main_f.clone(), a_f.clone(), b_f.clone()]);
    let first = first.as_array().unwrap();
    assert_eq!(first.len(), 3, "Expected exactly three intentional errors");
    assert_eq!(
        first.iter().filter(|d| d["code"] == json!(2322)).count(),
        2,
        "Missing assignment/JSX diagnostics"
    );
    assert!(
        first.iter().any(|d| d["code"] == json!(2339)),
        "Actual avril declarations did not enforce readonly process.args"
    );
    assert!(
        first.iter().all(|d| d["fileName"] == json!(main_f)),
        "Scoped resolution or declarations failed"
    );
    pass(
        &mut passed,
        "unsaved TSX + actual avril declarations + local/JSR-shaped fixture imports",
    );
    {
        let calls = calls.borrow();
        let fixture = fixture.borrow();
        assert!(
            calls
                .iter()
                .any(|c| c["moduleName"] == json!("@fixture/ui/jsx-runtime")),
            "JSX implicit import bypassed resolver"
        );
        for uri in [a_uri, b_uri] {
            assert!(
                calls.iter().any(|c| {
                    fixture
                        .directory_to_original
                        .get(c["containingDirectory"].as_str().unwrap())
                        .map(String::as_str)
                        == Some(uri)
                        && c["moduleName"] == json!("scoped")
                }),
                "No {uri} callback"
            );
        }
    }
    pass(
        &mut passed,
        "per-file scopes via compiler-only directories; original source unmodified",
    );
    let unicode = first
        .iter()
        .find(|d| d["startPosition"]["line"] == json!(3))
        .unwrap();
    let line = main_source.lines().nth(3).unwrap();
    assert_eq!(
        unicode["startPosition"]["character"].as_u64().unwrap() as usize,
        utf16_index(line, line.find("wrong").unwrap()),
        "Diagnostic position is not UTF-16"
    );
    pass(
        &mut passed,
        "diagnostic UTF-16 positions after an astral character",
    );

    let completions = api
        .call(
            "getCompletionsAtPosition",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "file": fixture.borrow().original_to_file["file:///workspace/app/completion.ts"],
                "position": completion_source.rfind("process.").unwrap() + "process.".len()
            }),
        )
        .unwrap();
    let names: Vec<&str> = completions["entries"]
        .as_array()
        .unwrap()
        .iter()
        .map(|entry| entry["name"].as_str().unwrap())
        .collect();
    assert!(names.contains(&"args"), "Missing process.args completion");
    assert!(names.contains(&"cwd"), "Missing process.cwd completion");
    pass(&mut passed, "member completion from real avril types");

    let position = utf16_index(&main_source, main_source.rfind("answer").unwrap());
    let ty = api
        .call(
            "getTypeAtPosition",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "file": main_f, "position": position
            }),
        )
        .unwrap();
    let type_text = api
        .call(
            "typeToString",
            json!({
                "snapshot": snapshot["snapshot"], "project": project, "type": ty["id"]
            }),
        )
        .unwrap();
    assert_eq!(type_text, json!("42"), "Unexpected type text: {type_text}");
    let symbol = api
        .call(
            "getSymbolAtPosition",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "file": main_f, "position": position
            }),
        )
        .unwrap();
    assert!(
        !symbol["declarations"].as_array().unwrap().is_empty(),
        "Missing symbol declaration handles"
    );
    pass(
        &mut passed,
        "hover building blocks: type text and symbol/declaration handles",
    );

    let alias = api
        .call(
            "getSymbolAtPosition",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "file": main_f, "position": main_source.find("answer").unwrap()
            }),
        )
        .unwrap();
    let target = api
        .call(
            "getAliasedSymbol",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "symbol": alias["reference"]
            }),
        )
        .unwrap();
    let remote_file =
        fixture.borrow().original_to_file["https://jsr.io/@fixture/data/1.0.0/mod.d.ts"].clone();
    assert!(
        target["declarations"]
            .as_array()
            .unwrap()
            .iter()
            .any(|handle| handle
                .as_str()
                .unwrap()
                .ends_with(&format!(".{remote_file}"))),
        "Import alias did not lead to remote declaration"
    );
    let local_references = api
        .call(
            "getReferencesToSymbolInFile",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "file": main_f, "symbol": alias["reference"]
            }),
        )
        .unwrap();
    let local_references = local_references.as_array().unwrap();
    assert!(
        local_references.len() >= 2,
        "Missing import/use reference handles"
    );
    let references = api
        .call(
            "getReferencedSymbolsForNode",
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "node": local_references[0],
                "position": main_source.find("answer").unwrap()
            }),
        )
        .unwrap();
    let mut handles: Vec<String> = Vec::new();
    for entry in references.as_array().unwrap() {
        handles.push(entry["definition"].as_str().unwrap().to_owned());
        handles.extend(
            entry["references"]
                .as_array()
                .unwrap()
                .iter()
                .map(|h| h.as_str().unwrap().to_owned()),
        );
    }
    let handle_original = |handle: &str| -> String {
        let mut parts = handle.splitn(3, '.');
        parts.next().unwrap();
        parts.next().unwrap();
        let file = parts.next().unwrap();
        fixture
            .borrow()
            .original_to_file
            .iter()
            .find(|(_, candidate)| *candidate == file)
            .map(|(original, _)| original.clone())
            .unwrap_or_else(|| panic!("Unknown compiler file: {file}"))
    };
    let reference_originals: Vec<String> = handles.iter().map(|h| handle_original(h)).collect();
    assert!(reference_originals.iter().any(|u| u == main_uri));
    assert!(
        reference_originals
            .iter()
            .any(|u| u == "https://jsr.io/@fixture/data/1.0.0/mod.d.ts")
    );
    pass(
        &mut passed,
        "cross-file definition/reference handles map back to original module URIs",
    );

    let fixed = main_source
        .replace("number = \"bad\"", "number = 1")
        .replace("count=\"wrong\"", "count={1}")
        .replace("process.args.push(\"x\")", "process.args.includes(\"x\")");
    snapshot = api
        .call(
            "updateSnapshot",
            json!({
                "snapshot": snapshot["snapshot"],
                "changes": {
                    "fileSystem": {"kind": "layer", "files": layer(vec![(main_f.clone(), fixed)])},
                    "ensurePrograms": [project]
                }
            }),
        )
        .unwrap();
    snapshots.push(snapshot["snapshot"].as_u64().unwrap());
    assert_eq!(
        diagnostics!(snapshot, [main_f.clone(), a_f.clone(), b_f.clone()])
            .as_array()
            .unwrap()
            .len(),
        0,
        "Unsaved fixes did not clear diagnostics"
    );
    assert_eq!(
        diagnostics!(initial, [main_f.clone(), a_f.clone(), b_f.clone()])
            .as_array()
            .unwrap()
            .len(),
        3,
        "Old snapshot changed after edit"
    );
    pass(
        &mut passed,
        "incremental unsaved edits; old snapshot remains queryable and unchanged",
    );

    let b_edited = format!(
        "{}\nimport {{ result as bypass }} from \"{}\"; void bypass;",
        fixture.borrow().files[&b_f],
        a_f
    );
    let denied = api
        .call(
            "updateSnapshot",
            json!({
                "snapshot": snapshot["snapshot"],
                "changes": {
                    "fileSystem": {"kind": "layer", "files": layer(vec![(b_f.clone(), b_edited)])},
                    "ensurePrograms": [project]
                }
            }),
        )
        .unwrap();
    snapshots.push(denied["snapshot"].as_u64().unwrap());
    let denied_diagnostics = diagnostics!(denied, [main_f.clone(), a_f.clone(), b_f.clone()]);
    let denied_diagnostics = denied_diagnostics.as_array().unwrap();
    assert_eq!(
        denied_diagnostics.len(),
        1,
        "Null resolver result fell back to an existing compiler file"
    );
    assert_eq!(denied_diagnostics[0]["code"], json!(2307));
    assert_eq!(
        diagnostics!(snapshot, [main_f.clone(), a_f.clone(), b_f.clone()])
            .as_array()
            .unwrap()
            .len(),
        0,
        "Branch snapshot modified its parent"
    );
    pass(
        &mut passed,
        "unmapped imports stay unresolved even when the target exists in the virtual filesystem",
    );

    resolver_id = register_resolver(&mut api, &mut resolvers, &calls, &fixture, &options, true);
    snapshot = api
        .call(
            "updateSnapshot",
            json!({
                "snapshot": snapshot["snapshot"],
                "changes": {
                    "reconfigurePrograms": [{
                        "id": project, "rootFiles": roots, "compilerOptions": options,
                        "options": {"moduleResolver": resolver_id}
                    }]
                }
            }),
        )
        .unwrap();
    snapshots.push(snapshot["snapshot"].as_u64().unwrap());
    let remapped = diagnostics!(snapshot, [main_f.clone(), a_f.clone(), b_f.clone()]);
    let remapped = remapped.as_array().unwrap();
    assert_eq!(
        remapped.len(),
        2,
        "Resolver replacement did not invalidate scoped imports"
    );
    assert!(
        remapped.iter().all(|d| {
            d["code"] == json!(2322) && (d["fileName"] == json!(a_f) || d["fileName"] == json!(b_f))
        }),
        "Resolver replacement did not invalidate scoped imports"
    );
    assert_eq!(
        diagnostics!(initial, [main_f.clone(), a_f.clone(), b_f.clone()])
            .as_array()
            .unwrap()
            .len(),
        3,
        "Resolver replacement affected the old snapshot"
    );
    pass(
        &mut passed,
        "import-map change: new resolver + reconfiguration invalidates cached resolutions",
    );

    let raw_options_dev = json!({
        "strict": true, "noEmit": true, "skipLibCheck": true, "target": "esnext",
        "module": "esnext", "moduleResolution": "bundler",
        "allowImportingTsExtensions": true, "jsx": "react-jsxdev",
        "jsxImportSource": "@fixture/dev-ui", "types": []
    });
    let development_options = parse_options(&mut api, &raw_options_dev, &roots);
    resolver_id = register_resolver(
        &mut api,
        &mut resolvers,
        &calls,
        &fixture,
        &development_options,
        true,
    );
    snapshot = api
        .call(
            "updateSnapshot",
            json!({
                "snapshot": snapshot["snapshot"],
                "changes": {
                    "reconfigurePrograms": [{
                        "id": project, "rootFiles": roots,
                        "compilerOptions": development_options,
                        "options": {"moduleResolver": resolver_id}
                    }]
                }
            }),
        )
        .unwrap();
    snapshots.push(snapshot["snapshot"].as_u64().unwrap());
    let jsx_diagnostics = diagnostics!(snapshot, [main_f.clone(), a_f.clone(), b_f.clone()]);
    {
        let calls = calls.borrow();
        assert!(
            calls
                .iter()
                .any(|c| c["moduleName"] == json!("@fixture/dev-ui/jsx-dev-runtime")),
            "JSX settings did not update implicit resolution"
        );
    }
    assert!(
        jsx_diagnostics.as_array().unwrap().iter().any(|d| {
            d["fileName"] == json!(main_f)
                && d["text"].as_str().unwrap().contains("jsx-dev-runtime")
        }),
        "Missing runtime was not diagnosed"
    );
    pass(
        &mut passed,
        "JSX configuration change re-resolves the generated runtime import",
    );

    // Negative control: same-directory filenames lose per-file scope identity.
    let raw_calls = Rc::new(RefCell::new(Vec::<Value>::new()));
    {
        let raw_calls = raw_calls.clone();
        let dep_a = fixture.borrow().original_to_file["file:///workspace/deps/a.ts"].clone();
        api.callbacks.insert(
            "avril/directory-control".to_owned(),
            Box::new(move |params| {
                if params["moduleName"] != json!("scoped") {
                    return Ok(Value::Null);
                }
                raw_calls.borrow_mut().push(params.clone());
                Ok(json!({"resolvedFileName": dep_a}))
            }),
        );
    }
    let control_resolver = api
        .call(
            "createModuleResolver",
            json!({
                "compilerOptions": options,
                "resolveModuleNameCallback": "avril/directory-control"
            }),
        )
        .unwrap()
        .as_u64()
        .unwrap();
    resolvers.push(control_resolver);
    let raw_a = "/avril-lsp/unmapped/a.ts";
    let raw_b = "/avril-lsp/unmapped/b.ts";
    let (a_source, b_source, dep_a_source) = {
        let fixture = fixture.borrow();
        (
            fixture.files[&a_f].clone(),
            fixture.files[&b_f].clone(),
            fixture.files[&fixture.original_to_file["file:///workspace/deps/a.ts"]].clone(),
        )
    };
    let dep_a_file = fixture.borrow().original_to_file["file:///workspace/deps/a.ts"].clone();
    let control = api
        .call(
            "createSnapshot",
            json!({
                "fileSystem": {"kind": "layer", "files": layer(vec![
                    (raw_a.to_owned(), a_source),
                    (raw_b.to_owned(), b_source),
                    (dep_a_file.clone(), dep_a_source),
                ])},
                "createPrograms": [{
                    "rootFiles": [raw_a, raw_b], "compilerOptions": options,
                    "options": {"moduleResolver": control_resolver}
                }]
            }),
        )
        .unwrap();
    snapshots.push(control["snapshot"].as_u64().unwrap());
    let control_diagnostics = api
        .call(
            "getSemanticDiagnostics",
            json!({
                "snapshot": control["snapshot"],
                "project": control["operation"]["createdPrograms"][0]
            }),
        )
        .unwrap();
    let control_diagnostics = control_diagnostics.as_array().unwrap();
    assert_eq!(
        control_diagnostics.len(),
        1,
        "Directory-only control did not reproduce the scope collision"
    );
    assert_eq!(control_diagnostics[0]["code"], json!(2322));
    assert_eq!(control_diagnostics[0]["fileName"], json!(raw_b));
    {
        let raw_calls = raw_calls.borrow();
        assert!(!raw_calls.is_empty());
        assert!(
            raw_calls.iter().all(|call| {
                call["containingDirectory"] == json!("/avril-lsp/unmapped")
                    && call.get("containingFile").is_none()
            }),
            "Callback now exposes a full referrer; reassess virtual directories"
        );
    }
    pass(
        &mut passed,
        "negative control: original same-directory filenames lose per-file scope identity",
    );
    {
        let fs_calls = fs_calls.borrow();
        assert!(
            fs_calls
                .iter()
                .any(|(method, _, allowed)| method == "readFile" && *allowed),
            "No standard library reads observed"
        );
        assert!(
            fs_calls.iter().any(|(_, _, allowed)| !allowed),
            "No out-of-library probes observed"
        );
    }
    pass(
        &mut passed,
        "filesystem callbacks serve standard libraries and deny other host-file probes",
    );

    for method in [
        "getQuickInfoAtPosition",
        "getDefinitionAtPosition",
        "findRenameLocations",
        "textDocument/hover",
        "textDocument/definition",
        "textDocument/rename",
    ] {
        match api.call(
            method,
            json!({
                "snapshot": snapshot["snapshot"], "project": project,
                "file": main_f, "position": position
            }),
        ) {
            Err(CallError::Rpc { message, .. }) => {
                assert!(
                    message.contains("unknown API method"),
                    "Unexpected failure probing {method}: {message}"
                );
                println!("GAP {method}: not exposed by the API server");
            }
            other => panic!("Unexpectedly supported {method}: {other:?}"),
        }
    }
    pass(
        &mut passed,
        "feature-gap probes distinguish absent methods from project/type errors",
    );
    println!(
        "\n{} checks passed; {} resolver callbacks, {} retained snapshots.",
        passed.len(),
        calls.borrow().len(),
        snapshots.len()
    );

    for snapshot_id in snapshots.iter().rev() {
        api.call("release", json!({"snapshot": snapshot_id}))
            .unwrap();
    }
    for resolver in &resolvers {
        api.call("releaseModuleResolver", json!({"resolver": resolver}))
            .unwrap();
    }
    api.close();
}