// =============================================================================
// DSL

type TestTree = TestGroup | Test;
type TestGroup = { name: string, children: TestTree[] };
type Test = { name: string, test: (TestController) => void };

export class TestRegistrar {
    #suites: TestGroup[];

    constructor() {
        this.#suites = [];
    }

    suite(name: string, children: TestTree[]) {
        checkDuplicates(name, children)
        this.#suites.push({ name, children });
    }

    run(reporter: Reporter) {
        reporter.register(this.#suites);
        for (const suite of this.#suites) {
            for (const c of suite.children) runTests(reporter, [suite.name], c);
        }
        reporter.finalize();
    }
}

export let TESTS = new TestRegistrar();

// Register a suite in the global registrar.
export function suite(name: string, children: TestTree[]) {
    TESTS.suite(name, children);
}

export function context(name: string, children: TestTree[]): TestTree {
    checkDuplicates(name, children);
    return { name, children };
}
export const group = context;

export function test(name: string, test: (TestController) => void): TestTree {
    return { name, test };
}

function checkDuplicates(parent: string, names: { name: string }[]) {
    let seen = new Set<string>();
    for (const { name } of names) {
        if (seen.has(name)) {
            throw new RangeError(`duplicate name '${name}' in '${parent}'`);
        }
        seen.add(name);
    }
}

export type TestState = "success" | "failure" | "skip";

class AbortSentinel {}

export class TestController {
    #state: TestState;
    logs: string[];

    constructor() {
        this.#state = "success";
        this.logs = [];
    }

    getState(): TestState {
        return this.#state;
    }

    fail() {
        this.#state = "failure";
    }

    failed(): boolean {
        return this.#state === "failure";
    }

    failNow(): never {
        this.fail();
        throw new AbortSentinel();
    }

    skip(message?: string): never {
        if (message != null) this.log(message);
        if (this.#state !== "failure") this.#state = "skip";
        throw new AbortSentinel();
    }

    skipped(): boolean {
        return this.#state === "skip";
    }

    log(message: string) {
        this.logs.push(message);
    }

    error(message: string) {
        this.log(message);
        this.fail();
    }

    fatal(message: string): never {
        this.log(message);
        this.failNow();
    }
}

// =============================================================================
// Execution

export interface TestResult {
    state: TestState;
    logs: string[];
}

function runTests(reporter: Reporter, parents: string[], node: TestTree) {
    const path = [...parents, node.name];
    if ("children" in node) {
        for (const c of node.children) runTests(reporter, path, c);
        return;
    }
    let controller = new TestController();
    try {
        node.test(controller);
    } catch (e) {
        if (!(e instanceof AbortSentinel)) {
            controller.error(extractExceptionString(e));
        }
    }
    reporter.update(path, { state: controller.getState(), logs: controller.logs });
}

function extractExceptionString(e: any): string {
    // String() instead of .toString() as null and undefined don't have
    // properties.
    const s = String(e);
    if (!(e instanceof Error && "stack" in e)) return s;
    // v8 (Chromium, NodeJS) include the error message, while Firefox and WebKit
    // do not.
    if (e.stack.startsWith(s)) return e.stack;
    return `${s}\n${e.stack}`;
}

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

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

export class NoOpReporter implements Reporter {
    suites: TestGroup[];
    results: ({ path: string[] } & TestResult)[];
    finalized: boolean;

    constructor() {
        this.suites = [];
        this.results = [];
        this.finalized = false;
    }

    register(suites: TestGroup[]) {
        this.suites = suites;
    }

    update(path: string[], result: TestResult) {
        this.results.push({ path, ...result });
    }

    finalize() {
        this.finalized = true;
    }
}

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

const SEP = " ❯ ";

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

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

    register(suites: TestGroup[]) {}

    update(path: string[], result: TestResult) {
        if (path.length === 0) throw new RangeError("path is empty");
        const pathStr = path.join(SEP);
        switch (result.state) {
        case "success":
            this.#successes.push({ path, ...result });
            if (this.verbose) this.stream.writeln(`✅️ ${pathStr}`);
            break;
        case "failure":
            this.#failures.push({ path, ...result });
            this.stream.writeln(`⚠️ ${pathStr}`);
            break;
        case "skip":
            this.#skips.push({ path, ...result });
            this.stream.writeln(`⏭️ ${pathStr}`);
            break;
        }
    }

    finalize() {
        if (this.verbose) this.#displaySection("successes", this.#successes, true);
        this.#displaySection("failures", this.#failures);
        this.#displaySection("skips", this.#skips);
        this.stream.writeln("");
        this.stream.writeln(
            `${this.#successes.length} succeeded, ${this.#failures.length} failed`
            + (this.#skips.length ? `, ${this.#skips.length} skipped` : "")
        );
    }

    #displaySection(name: string, data: ({ path: string[] } & TestResult)[], ignoreEmpty: boolean = false) {
        if (!data.length) return;

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

        this.stream.writeln("");
        this.stream.writeln(name.toUpperCase());
        this.stream.writeln("=".repeat(name.length));

        for (let [path, tests] of pathMap) {
            if (ignoreEmpty) tests = tests.filter((t) => t.logs.length);
            if (tests.length === 0) continue;
            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);
            }
        }
    }

    #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}`);
    }
}

export class DOMReporter implements Reporter {
    register(suites: TestGroup[]) {}

    update(path: string[], result: TestResult) {
        if (path.length === 0) throw new RangeError("path is empty");
        if (result.state === "skip") {
            document.getElementById("skip-counter-text").classList.remove("hidden");
        }
        const counter = document.getElementById(`${result.state}-counter`);
        counter.innerText = (Number(counter.innerText) + 1).toString();
        let parent = document.getElementById("root");
        for (const node of path) {
            let child = null;
            outer: for (const d of parent.children) {
                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 === null) {
                child = document.createElement("details");
                child.className = "test-node";
                const summary = document.createElement("summary");
                summary.appendChild(document.createTextNode(node));
                child.appendChild(summary);
                parent.appendChild(child);
            }
            if (result.state === "failure") child.open = true;
            if (!child.classList.contains("failure") &&
                (result.state !== "success" || !child.classList.contains("skip"))) {
                child.classList.add(result.state);
            }
            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() {}
}

interface GoNode {
    name: string;
    subtests?: GoNode[];
}

// Used to display results via `go test`, via some glue code from the Go side.
export class GoTestReporter implements Reporter {
    // Convert a test tree into the one expected by the Go code.
    static serialize(node: TestTree): GoNode {
        return {
            name: node.name,
            subtests: "children" in node ? node.children.map(GoTestReporter.serialize) : null,
        };
    }

    register(suites: TestGroup[]) {
        console.log(JSON.stringify(suites.map(GoTestReporter.serialize)));
    }

    update(path: string[], result: TestResult) {
        console.log(JSON.stringify({ path: path, ...result }));
    }

    finalize() {
        console.log("null");
    }
}