import { readFileSync } from "node:fs";
import { strictEqual, ok } from "node:assert";
import { describe, it } from "node:test";
import { parseNodeSection } from "../src/bundle.js";
import {
  verifyNodeHashes,
  verifyClosure,
  verifyRootClosure,
  deserializePayload,
  computeNodeHash,
} from "../src/merkle.js";

describe("merkle — deserializePayload", () => {
  it("Leaf (0x00)", () => {
    const result = deserializePayload(Buffer.from([0x00]));
    strictEqual(result.type, "leaf");
  });

  it("Stem (0x01 + 32 bytes)", () => {
    const childHash = Buffer.alloc(32, 0xab);
    const payload = Buffer.concat([Buffer.from([0x01]), childHash]);
    const result = deserializePayload(payload);
    strictEqual(result.type, "stem");
    strictEqual(result.childHash, "ab".repeat(32));
  });

  it("Fork (0x02 + 64 bytes)", () => {
    const left = Buffer.alloc(32, 0x01);
    const right = Buffer.alloc(32, 0x02);
    const payload = Buffer.concat([Buffer.from([0x02]), left, right]);
    const result = deserializePayload(payload);
    strictEqual(result.type, "fork");
    strictEqual(result.leftHash, "01".repeat(32));
    strictEqual(result.rightHash, "02".repeat(32));
  });

  it("Leaf with extra bytes fails", () => {
    throws(() => deserializePayload(Buffer.from([0x00, 0x00])), /invalid leaf/);
  });

  it("Unknown type fails", () => {
    throws(() => deserializePayload(Buffer.from([0xff])), /unknown type/);
  });
});

describe("merkle — computeNodeHash", () => {
  it("Leaf hash is correct length", () => {
    const leaf = { type: "leaf" };
    const hash = computeNodeHash(leaf);
    strictEqual(hash.length, 64);
  });
});

describe("merkle — node section parsing", () => {
  const fixtureDir = "test/fixtures";

  it("parses id.tri.bundle with correct node count", () => {
    const data = parseNodeSection(
      readFileSync(`${fixtureDir}/id.tri.bundle`)
    );
    const { nodeMap } = parseNodes(data);
    strictEqual(nodeMap.size, 4);
  });

  it("parses true.tri.bundle with correct node count", () => {
    const data = parseNodeSection(
      readFileSync(`${fixtureDir}/true.tri.bundle`)
    );
    const { nodeMap } = parseNodes(data);
    strictEqual(nodeMap.size, 2);
  });
});

describe("merkle — hash verification", () => {
  const fixtureDir = "test/fixtures";

  it("id.tri.bundle nodes all verify", () => {
    const data = parseNodeSection(
      readFileSync(`${fixtureDir}/id.tri.bundle`)
    );
    const { nodeMap } = parseNodes(data);
    const { verified, mismatches } = verifyNodeHashes(nodeMap);
    ok(verified, "id.tri.bundle node hashes should verify");
    strictEqual(mismatches.length, 0);
  });

  it("corrupted node payload fails hash verification", () => {
    const data = parseNodeSection(
      readFileSync(`${fixtureDir}/id.tri.bundle`)
    );
    const { nodeMap } = parseNodes(data);
    // Find a stem node to corrupt
    let stemKey = null;
    for (const [key, node] of nodeMap) {
      if (node.type === "stem") { stemKey = key; break; }
    }
    ok(stemKey, "should find a stem node to corrupt");
    const stem = nodeMap.get(stemKey);
    // Corrupt the child hash so serializeNode produces a different payload
    const corrupted = {
      ...stem,
      childHash: "00".repeat(32),
      payload: Buffer.concat([Buffer.from([0x01]), Buffer.alloc(32, 0x00)]),
    };
    nodeMap.set(stemKey, corrupted);
    const { verified, mismatches } = verifyNodeHashes(nodeMap);
    ok(!verified, "corrupted stem should fail hash verification");
    ok(mismatches.length > 0, "should have mismatches");
  });
});

describe("merkle — closure verification", () => {
  const fixtureDir = "test/fixtures";

  it("id.tri.bundle has complete closure", () => {
    const data = parseNodeSection(
      readFileSync(`${fixtureDir}/id.tri.bundle`)
    );
    const { nodeMap } = parseNodes(data);
    const { complete, missing } = verifyClosure(nodeMap);
    ok(complete, "id.tri.bundle should have complete closure");
    strictEqual(missing.length, 0);
  });

  it("verifyRootClosure checks transitive reachability", () => {
    const data = parseNodeSection(
      readFileSync(`${fixtureDir}/id.tri.bundle`)
    );
    const { nodeMap } = parseNodes(data);
    const rootHash = "039cc9aacf5be78ec1975713e6ad154a36988e3f3df18589b0d0c801d0825d78";
    const { complete, missingRoots } = verifyRootClosure(nodeMap, rootHash);
    ok(complete, "root should be reachable");
    strictEqual(missingRoots.length, 0);
  });
});

// Helper import
import { parseNodeSection as parseNodes } from "../src/merkle.js";

// Helper for throws
function throws(fn, expected) {
  try {
    fn();
    return false;
  } catch (e) {
    return expected.test(e.message);
  }
}