export interface TestResult {
    success: boolean;
    output: string;
}

// =============================================================================
// Reporting

export interface Reporter {
    update(path: string[], result: TestResult): void;
}

export interface Stream {
    writeln(s: string): void;
}

export class StreamReporter implements Reporter {
    stream: Stream;
    verbose: boolean;
    #failures: ({ path: string[] } & TestResult)[];
    counts: { successes: number, failures: number };

    constructor(stream: Stream, verbose: boolean = false) {
        this.stream = stream;
        this.verbose = verbose;
        this.#failures = [];
        this.counts = { successes: 0, failures: 0 };
    }

    update(path: string[], result: TestResult) {
        if (path.length === 0) throw new RangeError("path is empty");
        const pathStr = path.join(" ❯ ");
        if (result.success) {
            this.counts.successes++;
            if (this.verbose) this.stream.writeln(`✅️ ${pathStr}`);
        } else {
            this.counts.failures++;
            this.stream.writeln(`⚠️ ${pathStr}`);
            this.#failures.push({ path, ...result });
        }
    }

    display() {
        // Transform [{ path: ["a", "b", "c"] }, { path: ["a", "b", "d"] }]
        // into { "a ❯ b": ["c", "d"] }.
        let pathMap = new Map<string, ({ name: string } & TestResult)[]>();
        for (const f of this.#failures) {
            const key = f.path.slice(0, -1).join(" ❯ ");
            if (!pathMap.has(key)) pathMap.set(key, []);
            pathMap.get(key).push({ name: f.path.at(-1), ...f });
        }

        this.stream.writeln("");
        this.stream.writeln("FAILURES");
        this.stream.writeln("========");

        for (const [path, tests] of pathMap) {
            if (tests.length === 1) {
                const t = tests[0];
                const pathStr = path ? `${path} ❯ ` : "";
                const output = t.output ? `: ${t.output}` : "";
                this.stream.writeln(`${pathStr}${t.name}${output}`);
            } else {
                this.stream.writeln(path);
                for (const t of tests) {
                    const output = t.output ? `: ${t.output}` : "";
                    this.stream.writeln(`  - ${t.name}${output}`);
                }
            }
        }

        this.stream.writeln("");
        const { successes, failures } = this.counts;
        this.stream.writeln(`${successes} succeeded, ${failures} failed`);
    }
}

const r = new StreamReporter({ writeln: console.log }, true);
r.update(["alien", "can walk"], { success: false, output: "assertion failed" });
r.update(["alien", "can speak"], { success: false, output: "Uncaught ReferenceError: larynx is not defined" });
r.update(["alien", "sleep"], { success: true, output: "" });
r.update(["Tetromino", "generate", "tessellates"], { success: false, output: "assertion failed: 1 != 2" });
r.update(["Tetromino", "solve", "works"], { success: true, output: "" });
r.update(["discombobulate"], { success: false, output: "hippopotamonstrosesquippedaliophobia" });
r.update(["recombobulate"], { success: true, output: "" });
r.display();