import XCTest
import CryptoKit
@testable import LChatCore

// Native half of the inclusion-proof + bind-MAC wire format (#573). The leaf,
// root, and audit-path vectors here are the SAME frozen values checkpoint.go
// (TestGenVectors) and integrity.test.mjs pin: if any of the three platforms
// drifts, they disagree about a valid proof. Fix the code, not the vector.
final class InclusionProofTests: XCTestCase {

    // MARK: Merkle inclusion proofs

    func testLeafHashMatchesVector() {
        // journalLeafHash({seq:1, ts:1700000000, kind:"msg", msg_id:42, thread_id:"th", blob_hash:"ab"})
        let got = Checkpoint.leafHashHex(seq: 1, ts: 1_700_000_000, kind: "msg", msgID: 42, blobHash: "ab", threadID: "th")
        XCTAssertEqual(got, "e88f7b9ea2a1fdec4ce59c21467efcef2c1b7227b9618d5581c0923328143b15")
    }

    // The real 3-leaf tree from checkpoint.go's vector generator; proof for index 1.
    private let ROOT = "2d87c04aa784c70ba78cfae713e3434cbd4bea6da2644246b81e5e89240f02dd"
    private let AUDIT = [
        "9da3202f6b64da0ed851e92377b58188b5928facc765337938adb1bb32639e3e",
        "7a734103ada2f12e8d051e1c894fbf5f3a0a8049c26b4bc598b49c2c4da19189",
    ]
    private func goodProof() -> InclusionProof {
        InclusionProof(seq: 2, ts: 1_700_000_001, kind: "msg", msg_id: 11, thread_id: "t", blob_hash: "h2",
                       checkpoint_id: 1, root: ROOT, leaf_index: 1, tree_size: 3, audit_path: AUDIT)
    }

    func testVerifyInclusionReproducesGoRoot() {
        let (ok, root) = Checkpoint.verifyInclusion(goodProof())
        XCTAssertTrue(ok)
        XCTAssertEqual(root, ROOT)
    }

    func testTamperedProofDoesNotVerify() {
        var p = goodProof()
        // Wrong content (blob_hash) → different leaf → root won't match.
        p = InclusionProof(seq: p.seq, ts: p.ts, kind: p.kind, msg_id: p.msg_id, thread_id: p.thread_id,
                           blob_hash: "hX", checkpoint_id: p.checkpoint_id, root: p.root,
                           leaf_index: p.leaf_index, tree_size: p.tree_size, audit_path: p.audit_path)
        XCTAssertFalse(Checkpoint.verifyInclusion(p).ok)
        // Corrupted sibling.
        let corrupt = InclusionProof(seq: 2, ts: 1_700_000_001, kind: "msg", msg_id: 11, thread_id: "t", blob_hash: "h2",
                                     checkpoint_id: 1, root: ROOT, leaf_index: 1, tree_size: 3,
                                     audit_path: [String(repeating: "00", count: 32), AUDIT[1]])
        XCTAssertFalse(Checkpoint.verifyInclusion(corrupt).ok)
        // Wrong path length for the tree size → nil root.
        XCTAssertNil(Checkpoint.rootFromAuditPath(leafHex: String(repeating: "ab", count: 32), m: 1, n: 3, pathHex: [AUDIT[0]]))
    }

    func testAuditPathReproducesRootForEveryShape() {
        // A self-contained sweep (like the Go test): build n leaves, prove each.
        for n in 1...17 {
            var leaves: [String] = []
            for i in 0..<n {
                leaves.append(Checkpoint.leafHashHex(seq: Int64(i), ts: Int64(n), kind: "k", msgID: Int64(i), blobHash: "b\(i)", threadID: "t"))
            }
            let root = merkleRootHex(leaves)
            for m in 0..<n {
                let path = auditPathHex(leaves, m)
                let got = Checkpoint.rootFromAuditPath(leafHex: leaves[m], m: m, n: n, pathHex: path)
                XCTAssertEqual(got, root, "n=\(n) m=\(m)")
            }
        }
    }

    // Local reference Merkle (RFC 6962) to cross-check rootFromAuditPath — mirrors
    // checkpoint.go merkleRoot/merkleAuditPath, independent of the code under test.
    private func nodeHex(_ l: String, _ r: String) -> String {
        var d = Data("lchat-ckpt-node\n".utf8)
        d.append(Data(hexBytes(l))); d.append(Data(hexBytes(r)))
        return SHA256.hash(data: d).map { String(format: "%02x", $0) }.joined()
    }
    private func merkleRootHex(_ leaves: [String]) -> String {
        if leaves.count == 1 { return leaves[0] }
        var k = 1; while k * 2 < leaves.count { k *= 2 }
        return nodeHex(merkleRootHex(Array(leaves[0..<k])), merkleRootHex(Array(leaves[k...])))
    }
    private func auditPathHex(_ leaves: [String], _ m: Int) -> [String] {
        let n = leaves.count
        if n <= 1 { return [] }
        var k = 1; while k * 2 < n { k *= 2 }
        if m < k { return auditPathHex(Array(leaves[0..<k]), m) + [merkleRootHex(Array(leaves[k...]))] }
        return auditPathHex(Array(leaves[k...]), m - k) + [merkleRootHex(Array(leaves[0..<k]))]
    }
    private func hexBytes(_ s: String) -> [UInt8] {
        var out = [UInt8](); var i = s.startIndex
        while i < s.endIndex { let j = s.index(i, offsetBy: 2); out.append(UInt8(s[i..<j], radix: 16)!); i = j }
        return out
    }

    // MARK: sampleAndVerify (monitor)

    private final class MemStore: IntegrityStore {
        var data: Data?
        func loadIntegrity() -> Data? { data }
        func saveIntegrity(_ d: Data) { data = d }
    }

    @MainActor
    func testSampleAndVerifyConfirmsAndFlags() async {
        let store = MemStore()
        // Pre-seed a verified root (as a poll would) via the internal state.
        var seed = IntegrityState()
        seed.roots = [ROOT]
        store.saveIntegrity(try! JSONEncoder().encode(seed))
        let mon = IntegrityMonitor(store: store)

        let r = await mon.sampleAndVerify([(msgID: 11, blobHash: "h2")]) { _ in
            CheckpointProofResponse(proofs: [self.goodProof()], committed_to: 5)
        }
        XCTAssertEqual(r.verified, 1)
        XCTAssertEqual(mon.unresolvedAlerts().count, 0)

        // A forged proof against the trusted root → bad-proof alert.
        let forged = InclusionProof(seq: 2, ts: 1_700_000_001, kind: "msg", msg_id: 11, thread_id: "t", blob_hash: "h2",
                                    checkpoint_id: 1, root: ROOT, leaf_index: 1, tree_size: 3,
                                    audit_path: [String(repeating: "00", count: 32), AUDIT[1]])
        _ = await mon.sampleAndVerify([(msgID: 11, blobHash: "h2")]) { _ in
            CheckpointProofResponse(proofs: [forged], committed_to: 5)
        }
        XCTAssertTrue(mon.unresolvedAlerts().contains { $0.kind == "bad-proof" })
    }

    @MainActor
    func testSampleWithNoTrustedRootsIsSilent() async {
        let mon = IntegrityMonitor(store: MemStore()) // no roots verified yet
        let r = await mon.sampleAndVerify([(msgID: 11, blobHash: "h2")]) { _ in
            CheckpointProofResponse(proofs: [self.goodProof()], committed_to: 5)
        }
        XCTAssertEqual(r.checked, 0)
        XCTAssertEqual(mon.unresolvedAlerts().count, 0)
    }

    // MARK: bind-MAC (key transparency)

    func testBindKeyDeterministicAndDomainSeparated() throws {
        let t = InviteCrypto.randomSecret()
        let a = try InviteCrypto.derive(t)
        let b = try InviteCrypto.derive(t)
        XCTAssertEqual(a.bindKey, b.bindKey)
        XCTAssertNotEqual(a.bindKey, a.claimSecret) // domain separation
        let c = try InviteCrypto.derive(InviteCrypto.randomSecret())
        XCTAssertNotEqual(a.bindKey, c.bindKey)
    }

    func testBindMacVerifiesAndRejectsSubstitution() throws {
        let d = try InviteCrypto.derive(InviteCrypto.randomSecret())
        let kp = ECIES.generateUserKeypair()
        let mac = InviteCrypto.bindMac(bindKeyB64: d.bindKey, pubB64: kp.pub)
        XCTAssertNotNil(mac)
        XCTAssertTrue(InviteCrypto.verifyBindMac(bindKeyB64: d.bindKey, pubB64: kp.pub, macB64: mac!))
        // A substituted key must not verify — the whole point.
        let evil = ECIES.generateUserKeypair()
        XCTAssertFalse(InviteCrypto.verifyBindMac(bindKeyB64: d.bindKey, pubB64: evil.pub, macB64: mac!))
        // Wrong bind key rejected.
        let other = try InviteCrypto.derive(InviteCrypto.randomSecret())
        XCTAssertFalse(InviteCrypto.verifyBindMac(bindKeyB64: other.bindKey, pubB64: kp.pub, macB64: mac!))
        // Malformed never throws → false.
        XCTAssertFalse(InviteCrypto.verifyBindMac(bindKeyB64: d.bindKey, pubB64: kp.pub, macB64: "not base64!!"))
        XCTAssertFalse(InviteCrypto.verifyBindMac(bindKeyB64: "", pubB64: kp.pub, macB64: mac!))
    }

    // The web/Swift bind-MAC must interoperate: a MAC one produces the other
    // verifies. Cross-check against a value the JS test could reproduce (MAC
    // over decoded key bytes) via a fixed key + pub.
    func testBindMacIsOverDecodedBytesNotString() throws {
        let d = try InviteCrypto.derive(InviteCrypto.randomSecret())
        let kp = ECIES.generateUserKeypair()
        let mac = InviteCrypto.bindMac(bindKeyB64: d.bindKey, pubB64: kp.pub)!
        // Re-encode the SAME key bytes with '=' padding — a server re-encoding
        // trick that must NOT break verification (bind is over bytes, not string).
        let padded = kp.pub + "="
        XCTAssertTrue(InviteCrypto.verifyBindMac(bindKeyB64: d.bindKey, pubB64: padded, macB64: mac))
    }
}