import * as lc from "vscode-languageclient";
import * as fs from "fs";
import * as vscode from "vscode";
import { strict as nativeAssert } from "assert";
import { spawnSync } from "child_process";
import { inspect } from "util";

export function assert(condition: boolean, explanation: string): asserts condition {
    try {
        nativeAssert(condition, explanation);
    } catch (err) {
        log.error(`Assertion failed:`, explanation);
        throw err;
    }
}

export const log = new class {
    private enabled = true;
    private readonly output = vscode.window.createOutputChannel("Rust Analyzer Client");

    setEnabled(yes: boolean): void {
        log.enabled = yes;
    }

    // Hint: the type [T, ...T[]] means a non-empty array
    debug(...msg: [unknown, ...unknown[]]): void {
        if (!log.enabled) return;
        log.write("DEBUG", ...msg);
        log.output.toString();
    }

    info(...msg: [unknown, ...unknown[]]): void {
        log.write("INFO", ...msg);
    }

    warn(...msg: [unknown, ...unknown[]]): void {
        debugger;
        log.write("WARN", ...msg);
    }

    error(...msg: [unknown, ...unknown[]]): void {
        debugger;
        log.write("ERROR", ...msg);
        log.output.show(true);
    }

    private write(label: string, ...messageParts: unknown[]): void {
        const message = messageParts.map(log.stringify).join(" ");
        const dateTime = new Date().toLocaleString();
        log.output.appendLine(`${label} [${dateTime}]: ${message}`);
    }

    private stringify(val: unknown): string {
        if (typeof val === "string") return val;
        return inspect(val, {
            colors: false,
            depth: 6, // heuristic
        });
    }
};

export async function sendRequestWithRetry<TParam, TRet>(
    client: lc.LanguageClient,
    reqType: lc.RequestType<TParam, TRet, unknown>,
    param: TParam,
    token?: vscode.CancellationToken,
): Promise<TRet> {
    for (const delay of [2, 4, 6, 8, 10, null]) {
        try {
            return await (token
                ? client.sendRequest(reqType, param, token)
                : client.sendRequest(reqType, param)
            );
        } catch (error) {
            if (delay === null) {
                log.warn("LSP request timed out", { method: reqType.method, param, error });
                throw error;
            }

            if (error.code === lc.ErrorCodes.RequestCancelled) {
                throw error;
            }

            if (error.code !== lc.ErrorCodes.ContentModified) {
                log.warn("LSP request failed", { method: reqType.method, param, error });
                throw error;
            }

            await sleep(10 * (1 << delay));
        }
    }
    throw 'unreachable';
}

export function sleep(ms: number) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

export type RustDocument = vscode.TextDocument & { languageId: "rust" };
export type RustEditor = vscode.TextEditor & { document: RustDocument };

export function isRustDocument(document: vscode.TextDocument): document is RustDocument {
    // Prevent corrupted text (particularly via inlay hints) in diff views
    // by allowing only `file` schemes
    // unfortunately extensions that use diff views not always set this
    // to something different than 'file' (see ongoing bug: #4608)
    return document.languageId === 'rust' && document.uri.scheme === 'file';
}

export function isRustEditor(editor: vscode.TextEditor): editor is RustEditor {
    return isRustDocument(editor.document);
}

export function isValidExecutable(path: string): boolean {
    log.debug("Checking availability of a binary at", path);

    if (!fs.existsSync(path)) return false;

    const res = spawnSync(path, ["--version"], { encoding: 'utf8' });

    const isSuccess = res.status === 0;
    const printOutput = isSuccess ? log.debug : log.warn;
    printOutput(path, "--version:", res);

    return isSuccess;
}

/** Sets ['when'](https://code.visualstudio.com/docs/getstarted/keybindings#_when-clause-contexts) clause contexts */
export function setContextValue(key: string, value: any): Thenable<void> {
    return vscode.commands.executeCommand('setContext', key, value);
}

/**
 * Returns a higher-order function that caches the results of invoking the
 * underlying function.
 */
export function memoize<Ret, TThis, Param extends string>(func: (this: TThis, arg: Param) => Ret) {
    const cache = new Map<string, Ret>();

    return function(this: TThis, arg: Param) {
        const cached = cache.get(arg);
        if (cached) return cached;

        const result = func.call(this, arg);
        cache.set(arg, result);

        return result;
    };
}