export interface TestResult {
    success: boolean;
    logs: string[];
}

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

export interface Reporter {
    // While we could simply call a function with a tree representing all
    // results, which would indeed greatly simplify implementation of reporters,
    // simply registering a path and allowing the reporter to—either implicitly
    // or explicitly—construct a tree themselves allows for results to be
    // *incrementally reported*, instead of a great deal of silence until all
    // tests finish.
    update(path: string[], result: TestResult): void;
    // With just update(), the reporter never knows when all tests have
    // completed. The simplest possible use for this is to notify the user, but
    // its intent is actually more tailored to the StreamReporter scenario:
    // while destructively updated report rendering (as with a tree of DOM nodes
    // which are mutated) always displays the results in a structured manner
    // matching that of the tests, “rerendering” or otherwise destructively
    // updating the rendered output might be infeasible in some paradigms, such
    // as command-line applications—all existing implementations of such
    // rendering both mess up the scrollback position and necessarily crop out
    // some of the data at the bottom (since the top of the tree is forced to be
    // at the top of the screen, as one cannot unscroll portably). Explicitly
    // signaling to the reporter that no more results will be received permits
    // it to simply display live test progress linearly, while building up
    // a tree and displaying it once it's known the tree is complete.
    finalize(): void;
}

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

const SEP = " ❯ ";

// A simple reporter that outputs to some stream; suitable for CLIs.
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(SEP);
        if (result.success) {
            this.counts.successes++;
            // NOTE: emojis are used instead of colored Unicode symbols as
            // coloring isn't possible through all streams, which would make
            // this terminal-specific, and even in terminals and emulators
            // thereof, it's very tedious to correctly detect whether one should
            // use colors (https://no-color.org, https://bixense.com/clicolors,
            // https://force-color.org), ensure reasonable contrast is retained
            // on every possible theme (using reverse video is often the only
            // way), and be immediately noticeable. Emojis have an upper hand in
            // that they're more common than obscure Unicode characters—which
            // also means you're more likely to have an emoji font but not
            // a font with those symbols—and that they're double-width.
            if (this.verbose) this.stream.writeln(`✅️ ${pathStr}`);
        } else {
            this.counts.failures++;
            this.stream.writeln(`⚠️ ${pathStr}`);
            this.#failures.push({ path, ...result });
        }
    }

    finalize() {
        // Transform [{ path: ["a", "b", "c"] }, { path: ["a", "b", "d"] }] into
        // { "a ❯ b": ["c", "d"] }. NOTE: intermediate nodes are collapsed as
        // excessive nesting is difficult to convey clearly in a text-only
        // environment.
        let pathMap = new Map<string, ({ name: string } & TestResult)[]>();
        for (const f of this.#failures) {
            if (f.path.length === 0) throw new RangeError("path is empty");
            const key = f.path.slice(0, -1).join(SEP);
            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) {
                this.#writeOutput(tests[0], path ? `${path}${SEP}` : "", false);
            } else {
                this.stream.writeln(path);
                for (const t of tests) this.#writeOutput(t, "  - ", true);
            }
        }

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

    #writeOutput(test: { name: string } & TestResult, prefix: string, nested: boolean) {
        let output = "";
        if (test.logs.length) {
            // Individual logs might span multiple lines, so join them together
            // then split it again.
            const logStr = test.logs.join("\n");
            const lines = logStr.split("\n");
            if (lines.length <= 1) {
                output = `: ${logStr}`;
            } else {
                const padding = nested ? "      " : "  ";
                output = ":\n" + lines.map((line) => padding + line).join("\n");
            }
        }
        this.stream.writeln(`${prefix}${test.name}${output}`);
    }
}

function assertGetElementById(id: string): HTMLElement {
    let elem = document.getElementById(id);
    if (elem == null) throw new ReferenceError(`element with ID '${id}' missing from DOM`);
    return elem;
}

// A reporter that directly translates a tree of results into a tree of
// collapsible elements in the DOM.
export class DOMReporter implements Reporter {
    update(path: string[], result: TestResult) {
        if (path.length === 0) throw new RangeError("path is empty");
        const counter = assertGetElementById(result.success ? "successes" : "failures");
        counter.innerText = (Number(counter.innerText) + 1).toString();
        let parent = assertGetElementById("root");
        for (const node of path) {
            let child: HTMLDetailsElement | null = null;
            let d: Element;
            outer: for (d of parent.children) {
                if (!(d instanceof HTMLDetailsElement)) continue;
                for (const s of d.children) {
                    if (!(s instanceof HTMLElement)) continue;
                    if (!(s.tagName === "SUMMARY" && s.innerText === node)) continue;
                    child = d;
                    break outer;
                }
            }
            if (!child) {
                child = document.createElement("details");
                child.className = "test-node";
                child.ariaRoleDescription = "test";
                const summary = document.createElement("summary");
                summary.appendChild(document.createTextNode(node));
                summary.ariaRoleDescription = "test name";
                child.appendChild(summary);
                parent.appendChild(child);
            }
            if (!result.success) {
                // Minimize successes by default, by only expanding failures.
                child.open = true;
                child.classList.add("failure");
            }
            parent = child;
        }
        const p = document.createElement("p");
        p.classList.add("test-desc");
        if (result.logs.length) {
            const pre = document.createElement("pre");
            pre.appendChild(document.createTextNode(result.logs.join("\n")));
            p.appendChild(pre);
        } else {
            p.classList.add("italic");
            p.appendChild(document.createTextNode("No output."));
        }
        parent.appendChild(p);
    }

    finalize() {}
}

let r = globalThis.document ? new DOMReporter() : new StreamReporter({ writeln: console.log });
r.update(["alien", "can walk"], { success: false, logs: ["assertion failed"] });
r.update(["alien", "can speak"], { success: false, logs: ["Uncaught ReferenceError: larynx is not defined"] });
r.update(["alien", "sleep"], { success: true, logs: [] });
r.update(["Tetromino", "generate", "tessellates"], { success: false, logs: ["assertion failed: 1 != 2"] });
r.update(["Tetromino", "solve", "works"], { success: true, logs: [] });
r.update(["discombobulate", "english"], { success: false, logs: ["hippopotomonstrosesquipedaliophobia\npneumonoultramicroscopicsilicovolcanoconiosis", "supercalifragilisticexpialidocious"] });
r.update(["discombobulate", "geography"], { success: false, logs: ["Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu"] });
r.update(["recombobulate"], { success: true, logs: [] });
r.finalize();