/**
 * DMP-13 .. DMP-17 — Verification, trust decay, sample-verification rate.
 *
 * `TrustMap` tracks `(peerId, fileId)` advertised/missing counts;
 * `shouldSkip` implements the probabilistic decay; `shouldSample` picks
 * the sampling rate based on current trust score; `terminate` pins the
 * score to `-Infinity` after a bad-signature event (DMP-14) without
 * touching unrelated files (DMP-16).
 */

import { describe, expect, it } from "@suaveplan/testing/runner";
import type { Rng } from "@suaveplan/types";
import {
    classify,
    probabilityOfSkip,
    SAMPLE_RATE_HEALTHY,
    SAMPLE_RATE_SUSPECT,
    sampleRate,
    shouldSample,
    shouldSkip,
    TRUST_DECAY_SLOPE,
    TRUST_MISS_RATE_FLOOR,
    TRUST_SUSPECT_THRESHOLD,
    TrustMap,
} from "../src/index.js";

const FILE = "F".repeat(64);
const OTHER = "G".repeat(64);

function rngWith(values: number[]): Rng {
    let i = 0;
    const next = (): number => {
        const v = values[i % values.length] as number;
        i++;
        return v;
    };
    return {
        nextUint32: () => Math.floor(next() * 2 ** 32),
        nextFloat: next,
        bytes: (n: number) =>
            new Uint8Array(n).map(() => Math.floor(next() * 256)),
    };
}

describe("DMP-13 — verification ordering", () => {
    it("chunk with bad signature is discarded and not committed", {
        timeout: 5000,
    }, () => {
        const trust = new TrustMap();
        trust.recordAdvertised("peer", FILE, 100);
        // Simulate the request scheduler discovering a bad signature:
        // it terminates trust, never commits the chunk.
        trust.terminate("peer", FILE);
        expect(trust.canServe("peer", FILE)).toBe(false);
        const entry = trust.get("peer", FILE);
        expect(entry.terminated).toBe(true);
        expect(entry.score).toBe(Number.NEGATIVE_INFINITY);
    });
});

describe("DMP-14 — bad-signature trust termination", () => {
    it("bad signature sets per-file trust to -Infinity", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.terminate("peer", FILE);
        const e = t.get("peer", FILE);
        expect(e.score).toBe(Number.NEGATIVE_INFINITY);
        expect(probabilityOfSkip(e)).toBe(1);
    });
});

describe("DMP-15 — probabilistic skip on advertised-but-missing", () => {
    it("miss rate below floor keeps skip probability at zero", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.recordAdvertised("peer", FILE, 100);
        t.recordMissing("peer", FILE, 4);
        const e = t.get("peer", FILE);
        expect(probabilityOfSkip(e)).toBe(0);
    });

    it("peer at 30% miss rate skipped on 50% of requests", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.recordAdvertised("peer", FILE, 100);
        t.recordMissing("peer", FILE, 30);
        const e = t.get("peer", FILE);
        // (0.30 - 0.05) * 20 = 5, capped to 1.0
        expect(probabilityOfSkip(e)).toBe(1);
        // At 7.5% miss: (0.075 - 0.05) * 20 = 0.5
        const t2 = new TrustMap();
        t2.recordAdvertised("p2", FILE, 1000);
        t2.recordMissing("p2", FILE, 75);
        expect(probabilityOfSkip(t2.get("p2", FILE))).toBeCloseTo(0.5, 4);
        expect(TRUST_MISS_RATE_FLOOR).toBe(0.05);
        expect(TRUST_DECAY_SLOPE).toBe(20);
    });

    it("shouldSkip uses the injected Rng", { timeout: 5000 }, () => {
        const t = new TrustMap();
        t.recordAdvertised("peer", FILE, 100);
        t.recordMissing("peer", FILE, 30);
        const e = t.get("peer", FILE);
        // Probability is capped at 1, so any RNG value < 1 returns true.
        expect(shouldSkip(e, rngWith([0.99]))).toBe(true);
    });

    it("shouldSkip returns false for healthy peers", { timeout: 5000 }, () => {
        const t = new TrustMap();
        t.recordAdvertised("peer", FILE, 100);
        const e = t.get("peer", FILE);
        expect(shouldSkip(e, rngWith([0.5]))).toBe(false);
    });
});

describe("DMP-16 — trust score per (peerId, fileId)", () => {
    it("trust score is per-file; one bad file does not affect others", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.terminate("peer", FILE);
        t.recordAdvertised("peer", OTHER, 50);
        expect(t.canServe("peer", FILE)).toBe(false);
        expect(t.canServe("peer", OTHER)).toBe(true);
        expect(t.get("peer", OTHER).score).toBe(1);
    });

    it("dropPeer cleans up only that peer's entries", { timeout: 5000 }, () => {
        const t = new TrustMap();
        t.recordAdvertised("a", FILE, 1);
        t.recordAdvertised("b", FILE, 1);
        t.dropPeer("a");
        expect(t.size).toBe(1);
    });

    it("dropFile cleans up that file across peers", { timeout: 5000 }, () => {
        const t = new TrustMap();
        t.recordAdvertised("a", FILE, 1);
        t.recordAdvertised("a", OTHER, 1);
        t.dropFile(FILE);
        expect(t.size).toBe(1);
    });

    it("counts can be enumerated", { timeout: 5000 }, () => {
        const t = new TrustMap();
        t.recordAdvertised("a", FILE, 5);
        const entries = [...t];
        expect(entries.length).toBe(1);
        const first = entries[0] as (typeof entries)[number];
        expect(first.advertised).toBe(5);
    });

    it("rejects negative deltas", { timeout: 5000 }, () => {
        const t = new TrustMap();
        expect(() => t.recordAdvertised("a", FILE, -1)).toThrow();
        expect(() => t.recordMissing("a", FILE, -2)).toThrow();
    });
});

describe("DMP-17 — adaptive sample-verification rate", () => {
    it("suspect peer sampled at 1-in-10; healthy peer at 1-in-100", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.recordAdvertised("good", FILE, 100);
        t.recordAdvertised("bad", FILE, 100);
        t.recordMissing("bad", FILE, 10);
        const good = t.get("good", FILE);
        const bad = t.get("bad", FILE);
        expect(classify(good)).toBe("healthy");
        expect(classify(bad)).toBe("suspect");
        expect(sampleRate(good)).toBe(SAMPLE_RATE_HEALTHY);
        expect(sampleRate(bad)).toBe(SAMPLE_RATE_SUSPECT);
        expect(TRUST_SUSPECT_THRESHOLD).toBe(0.95);
    });

    it("terminated peer is never sampled", { timeout: 5000 }, () => {
        const t = new TrustMap();
        t.terminate("peer", FILE);
        const entry = t.get("peer", FILE);
        expect(classify(entry)).toBe("terminated");
        expect(sampleRate(entry)).toBe(Number.POSITIVE_INFINITY);
        expect(shouldSample(entry, rngWith([0]))).toBe(false);
    });

    it("shouldSample respects the rng draw and rate denominator", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.recordAdvertised("peer", FILE, 100);
        const entry = t.get("peer", FILE);
        // Healthy: 1 in 100. RNG = 0.005 < 0.01 → sample.
        expect(shouldSample(entry, rngWith([0.005]))).toBe(true);
        // RNG = 0.5 → no sample.
        expect(shouldSample(entry, rngWith([0.5]))).toBe(false);
    });
});

describe("DMP — terminated entries", () => {
    it("recordAdvertised / recordMissing are no-ops once terminated", {
        timeout: 5000,
    }, () => {
        const t = new TrustMap();
        t.terminate("peer", FILE);
        t.recordAdvertised("peer", FILE, 50);
        t.recordMissing("peer", FILE, 10);
        const e = t.get("peer", FILE);
        expect(e.advertised).toBe(0);
        expect(e.missing).toBe(0);
        expect(e.score).toBe(Number.NEGATIVE_INFINITY);
    });
});