zlay / src / validator.zig

//! relay frame validator — DID key resolution + real signature verification
//!
//! validates firehose commit frames by verifying the commit signature against
//! the pre-resolved signing key for the DID. accepts pre-decoded CBOR payload
//! from the subscriber (decoded via zat SDK). on cache miss, skips validation
//! and queues background resolution. no frame is ever blocked on network I/O.

const std = @import("std");
const zat = @import("zat");
const broadcaster = @import("broadcaster.zig");
const event_log_mod = @import("event_log.zig");
const lru = @import("lru.zig");

const Allocator = std.mem.Allocator;
const log = std.log.scoped(.relay);

/// decoded and cached signing key for a DID
const CachedKey = struct {
    key_type: zat.multicodec.KeyType,
    raw: [33]u8, // compressed public key (secp256k1 or p256)
    len: u8,
    resolve_time: i64 = 0, // epoch seconds when resolved
};

pub const ValidationResult = struct {
    valid: bool,
    skipped: bool,
    data_cid: ?[]const u8 = null, // MST root CID from verified commit
    commit_rev: ?[]const u8 = null, // rev from verified commit
};

/// configuration for commit validation checks
pub const ValidatorConfig = struct {
    /// verify MST structure during signature verification
    verify_mst: bool = false, // off by default for relay throughput
    /// verify commit diffs via MST inversion (sync 1.1)
    verify_commit_diff: bool = false,
    /// max allowed operations per commit
    max_ops: usize = 200,
    /// max clock skew for rev timestamps (seconds)
    rev_clock_skew: i64 = 300, // 5 minutes
};

pub const Validator = struct {
    allocator: Allocator,
    stats: *broadcaster.Stats,
    config: ValidatorConfig,
    persist: ?*event_log_mod.DiskPersist = null,
    // DID → signing key cache (decoded, ready for verification)
    cache: lru.LruCache(CachedKey),
    // background resolve queue
    queue: std.ArrayListUnmanaged([]const u8) = .{},
    // in-flight set — prevents duplicate DID entries in the queue
    queued_set: std.StringHashMapUnmanaged(void) = .{},
    queue_mutex: std.Thread.Mutex = .{},
    queue_cond: std.Thread.Condition = .{},
    resolver_threads: [max_resolver_threads]?std.Thread = .{null} ** max_resolver_threads,
    alive: std.atomic.Value(bool) = .{ .raw = true },
    max_cache_size: u32 = 250_000,

    const max_resolver_threads = 8;
    const default_resolver_threads = 4;
    const max_queue_size: usize = 100_000;

    pub fn init(allocator: Allocator, stats: *broadcaster.Stats) Validator {
        return initWithConfig(allocator, stats, .{});
    }

    pub fn initWithConfig(allocator: Allocator, stats: *broadcaster.Stats, config: ValidatorConfig) Validator {
        return .{
            .allocator = allocator,
            .stats = stats,
            .config = config,
            .cache = lru.LruCache(CachedKey).init(allocator, 250_000),
        };
    }

    pub fn deinit(self: *Validator) void {
        self.alive.store(false, .release);
        self.queue_cond.broadcast();
        for (&self.resolver_threads) |*t| {
            if (t.*) |thread| {
                thread.join();
                t.* = null;
            }
        }

        self.cache.deinit();

        // free queued DIDs
        for (self.queue.items) |did| {
            self.allocator.free(did);
        }
        self.queue.deinit(self.allocator);
        self.queued_set.deinit(self.allocator);
    }

    /// start background resolver threads
    pub fn start(self: *Validator) !void {
        self.max_cache_size = parseEnvInt(u32, "VALIDATOR_CACHE_SIZE", self.max_cache_size);
        self.cache.capacity = self.max_cache_size;
        const n = parseEnvInt(u8, "RESOLVER_THREADS", default_resolver_threads);
        const count = @min(n, max_resolver_threads);
        for (self.resolver_threads[0..count]) |*t| {
            t.* = try std.Thread.spawn(.{ .stack_size = @import("main.zig").default_stack_size }, resolveLoop, .{self});
        }
    }

    /// validate a #sync frame: signature verification only (no ops, no MST).
    /// #sync resets a repo to a new commit state — used for recovery from broken streams.
    /// on cache miss, queues background resolution and skips.
    pub fn validateSync(self: *Validator, payload: zat.cbor.Value) ValidationResult {
        const did = payload.getString("did") orelse {
            _ = self.stats.skipped.fetchAdd(1, .monotonic);
            return .{ .valid = true, .skipped = true };
        };

        if (zat.Did.parse(did) == null) {
            _ = self.stats.failed.fetchAdd(1, .monotonic);
            _ = self.stats.failed_bad_did.fetchAdd(1, .monotonic);
            return .{ .valid = false, .skipped = false };
        }

        // check rev is valid TID (if present)
        if (payload.getString("rev")) |rev| {
            if (zat.Tid.parse(rev) == null) {
                _ = self.stats.failed.fetchAdd(1, .monotonic);
                _ = self.stats.failed_bad_rev.fetchAdd(1, .monotonic);
                return .{ .valid = false, .skipped = false };
            }
        }

        const blocks = payload.getBytes("blocks") orelse {
            _ = self.stats.failed.fetchAdd(1, .monotonic);
            _ = self.stats.failed_missing_blocks.fetchAdd(1, .monotonic);
            return .{ .valid = false, .skipped = false };
        };

        // #sync CAR should be small (just the signed commit block)
        // lexicon maxLength: 10000
        if (blocks.len > 10_000) {
            _ = self.stats.failed.fetchAdd(1, .monotonic);
            _ = self.stats.failed_oversized_blocks.fetchAdd(1, .monotonic);
            return .{ .valid = false, .skipped = false };
        }

        // cache lookup
        const cached_key: ?CachedKey = self.cache.get(did);

        if (cached_key == null) {
            _ = self.stats.cache_misses.fetchAdd(1, .monotonic);
            _ = self.stats.skipped.fetchAdd(1, .monotonic);
            self.queueResolve(did);
            return .{ .valid = true, .skipped = true };
        }

        _ = self.stats.cache_hits.fetchAdd(1, .monotonic);

        // verify signature (no MST, no ops)
        const public_key = zat.multicodec.PublicKey{
            .key_type = cached_key.?.key_type,
            .raw = cached_key.?.raw[0..cached_key.?.len],
        };

        var arena = std.heap.ArenaAllocator.init(self.allocator);
        defer arena.deinit();

        const result = zat.verifyCommitCar(arena.allocator(), blocks, public_key, .{
            .verify_mst = false,
            .expected_did = did,
            .max_car_size = 10 * 1024,
        }) catch |err| {
            log.debug("sync verification failed for {s}: {s}", .{ did, @errorName(err) });
            // sync spec: on signature failure, key may have rotated.
            // evict cached key and queue re-resolution. skip this frame.
            self.evictKey(did);
            self.queueResolve(did);
            _ = self.stats.skipped.fetchAdd(1, .monotonic);
            return .{ .valid = true, .skipped = true };
        };

        _ = self.stats.validated.fetchAdd(1, .monotonic);
        return .{
            .valid = true,
            .skipped = false,
            .data_cid = result.commit_cid,
            .commit_rev = result.commit_rev,
        };
    }

    /// validate a commit frame using a pre-decoded CBOR payload (from SDK decoder).
    /// on cache miss, queues background resolution and skips.
    pub fn validateCommit(self: *Validator, payload: zat.cbor.Value) ValidationResult {
        // extract DID from decoded payload
        const did = payload.getString("repo") orelse {
            _ = self.stats.skipped.fetchAdd(1, .monotonic);
            return .{ .valid = true, .skipped = true };
        };

        // check cache for pre-resolved signing key
        const cached_key: ?CachedKey = self.cache.get(did);

        if (cached_key == null) {
            // cache miss — queue for background resolution, skip validation
            _ = self.stats.cache_misses.fetchAdd(1, .monotonic);
            _ = self.stats.skipped.fetchAdd(1, .monotonic);
            self.queueResolve(did);
            return .{ .valid = true, .skipped = true };
        }

        _ = self.stats.cache_hits.fetchAdd(1, .monotonic);

        // cache hit — do structure checks + signature verification
        if (self.verifyCommit(payload, did, cached_key.?)) |vr| {
            _ = self.stats.validated.fetchAdd(1, .monotonic);
            return vr;
        } else |err| {
            log.debug("commit verification failed for {s}: {s}", .{ did, @errorName(err) });
            // sync spec: on signature failure, key may have rotated.
            // evict cached key and queue re-resolution. skip this frame
            // (treat as cache miss). next commit will use the refreshed key.
            self.evictKey(did);
            self.queueResolve(did);
            _ = self.stats.skipped.fetchAdd(1, .monotonic);
            return .{ .valid = true, .skipped = true };
        }
    }

    fn verifyCommit(self: *Validator, payload: zat.cbor.Value, expected_did: []const u8, cached_key: CachedKey) !ValidationResult {
        // commit structure checks first (cheap, no allocation)
        self.checkCommitStructure(payload) catch {
            _ = self.stats.failed_bad_structure.fetchAdd(1, .monotonic);
            return error.InvalidFrame;
        };

        // extract blocks (raw CAR bytes) from the pre-decoded payload
        const blocks = payload.getBytes("blocks") orelse return error.InvalidFrame;

        // blocks size check — lexicon maxLength: 2000000
        if (blocks.len > 2_000_000) return error.InvalidFrame;

        // build public key for verification
        const public_key = zat.multicodec.PublicKey{
            .key_type = cached_key.key_type,
            .raw = cached_key.raw[0..cached_key.len],
        };

        // run real signature verification (needs its own arena for CAR/MST temporaries)
        var arena = std.heap.ArenaAllocator.init(self.allocator);
        defer arena.deinit();
        const alloc = arena.allocator();

        // try sync 1.1 path: extract ops and use verifyCommitDiff
        if (self.config.verify_commit_diff) {
            if (self.extractOps(alloc, payload)) |msg_ops| {
                // get stored prev_data from payload
                const prev_data: ?[]const u8 = if (payload.get("prevData")) |pd| switch (pd) {
                    .cid => |c| c.raw,
                    .null => null,
                    else => null,
                } else null;

                const diff_result = zat.verifyCommitDiff(alloc, blocks, msg_ops, prev_data, public_key, .{
                    .expected_did = expected_did,
                    .skip_inversion = prev_data == null,
                }) catch |err| {
                    return err;
                };

                return .{
                    .valid = true,
                    .skipped = false,
                    .data_cid = diff_result.data_cid,
                    .commit_rev = diff_result.commit_rev,
                };
            }
        }

        // fallback: legacy verification (signature + optional MST walk)
        const result = zat.verifyCommitCar(alloc, blocks, public_key, .{
            .verify_mst = self.config.verify_mst,
            .expected_did = expected_did,
        }) catch |err| {
            return err;
        };

        return .{
            .valid = true,
            .skipped = false,
            .data_cid = result.commit_cid,
            .commit_rev = result.commit_rev,
        };
    }

    /// extract ops from payload and convert to mst.Operation array.
    /// the firehose format uses a single "path" field ("collection/rkey"),
    /// not separate "collection"/"rkey" fields.
    fn extractOps(self: *Validator, alloc: Allocator, payload: zat.cbor.Value) ?[]const zat.MstOperation {
        _ = self;
        const ops_array = payload.getArray("ops") orelse return null;
        var ops: std.ArrayListUnmanaged(zat.MstOperation) = .{};
        for (ops_array) |op| {
            const action = op.getString("action") orelse continue;
            const path = op.getString("path") orelse continue;

            // validate path contains "/" (collection/rkey)
            if (std.mem.indexOfScalar(u8, path, '/') == null) continue;

            // extract CID values
            const cid_value: ?[]const u8 = if (op.get("cid")) |v| switch (v) {
                .cid => |c| c.raw,
                else => null,
            } else null;

            var value: ?[]const u8 = null;
            var prev: ?[]const u8 = null;

            if (std.mem.eql(u8, action, "create")) {
                value = cid_value;
            } else if (std.mem.eql(u8, action, "update")) {
                value = cid_value;
                prev = if (op.get("prev")) |v| switch (v) {
                    .cid => |c| c.raw,
                    else => null,
                } else null;
            } else if (std.mem.eql(u8, action, "delete")) {
                prev = if (op.get("prev")) |v| switch (v) {
                    .cid => |c| c.raw,
                    else => null,
                } else null;
            } else continue;

            ops.append(alloc, .{
                .path = path,
                .value = value,
                .prev = prev,
            }) catch return null;
        }

        if (ops.items.len == 0) return null;
        return ops.items;
    }

    fn checkCommitStructure(self: *Validator, payload: zat.cbor.Value) !void {
        // check repo field is a valid DID
        const repo = payload.getString("repo") orelse return error.InvalidFrame;
        if (zat.Did.parse(repo) == null) return error.InvalidFrame;

        // check rev is a valid TID
        if (payload.getString("rev")) |rev| {
            if (zat.Tid.parse(rev) == null) return error.InvalidFrame;
        }

        // check ops count
        if (payload.get("ops")) |ops_value| {
            switch (ops_value) {
                .array => |ops| {
                    if (ops.len > self.config.max_ops) return error.InvalidFrame;
                    // validate each op has valid path (collection/rkey)
                    for (ops) |op| {
                        if (op.getString("path")) |path| {
                            if (std.mem.indexOfScalar(u8, path, '/')) |sep| {
                                const collection = path[0..sep];
                                const rkey = path[sep + 1 ..];
                                if (zat.Nsid.parse(collection) == null) return error.InvalidFrame;
                                if (rkey.len > 0) {
                                    if (zat.Rkey.parse(rkey) == null) return error.InvalidFrame;
                                }
                            } else return error.InvalidFrame; // path must contain '/'
                        }
                    }
                },
                else => return error.InvalidFrame,
            }
        }
    }

    fn queueResolve(self: *Validator, did: []const u8) void {
        // check if already cached (race between validate and resolver)
        if (self.cache.contains(did)) return;

        const duped = self.allocator.dupe(u8, did) catch return;

        self.queue_mutex.lock();
        defer self.queue_mutex.unlock();

        // skip if already queued (prevents unbounded queue growth)
        if (self.queued_set.contains(duped)) {
            self.allocator.free(duped);
            return;
        }

        // cap queue size — drop DID without adding to queued_set so it can be re-queued later
        if (self.queue.items.len >= max_queue_size) {
            self.allocator.free(duped);
            return;
        }

        self.queue.append(self.allocator, duped) catch {
            self.allocator.free(duped);
            return;
        };
        self.queued_set.put(self.allocator, duped, {}) catch {};
        self.queue_cond.signal();
    }

    fn resolveLoop(self: *Validator) void {
        var resolver = zat.DidResolver.initWithOptions(self.allocator, .{ .keep_alive = true });
        defer resolver.deinit();

        while (self.alive.load(.acquire)) {
            var did: ?[]const u8 = null;
            {
                self.queue_mutex.lock();
                defer self.queue_mutex.unlock();
                while (self.queue.items.len == 0 and self.alive.load(.acquire)) {
                    self.queue_cond.timedWait(&self.queue_mutex, 1 * std.time.ns_per_s) catch {};
                }
                if (self.queue.items.len > 0) {
                    did = self.queue.orderedRemove(0);
                    _ = self.queued_set.remove(did.?);
                }
            }

            const d = did orelse continue;
            defer self.allocator.free(d);

            // skip if already cached (resolved while queued)
            if (self.cache.contains(d)) continue;

            // resolve DID → signing key
            const parsed = zat.Did.parse(d) orelse continue;
            var doc = resolver.resolve(parsed) catch |err| {
                log.debug("DID resolve failed for {s}: {s}", .{ d, @errorName(err) });
                continue;
            };
            defer doc.deinit();

            // extract and decode signing key
            const vm = doc.signingKey() orelse continue;
            const key_bytes = zat.multibase.decode(self.allocator, vm.public_key_multibase) catch continue;
            defer self.allocator.free(key_bytes);
            const public_key = zat.multicodec.parsePublicKey(key_bytes) catch continue;

            // store decoded key in cache (fixed-size, no pointer chasing)
            var cached = CachedKey{
                .key_type = public_key.key_type,
                .raw = undefined,
                .len = @intCast(public_key.raw.len),
                .resolve_time = std.time.timestamp(),
            };
            @memcpy(cached.raw[0..public_key.raw.len], public_key.raw);

            self.cache.put(d, cached) catch continue;

            // --- host validation (merged from migration queue) ---
            // while we have the DID doc, check PDS endpoint and update host if needed.
            // best-effort: failures don't prevent signing key caching.
            if (self.persist) |persist| {
                if (doc.pdsEndpoint()) |pds_endpoint| {
                    if (extractHostFromUrl(pds_endpoint)) |pds_host| {
                        const pds_host_id = (persist.getHostIdForHostname(pds_host) catch null) orelse continue;
                        const uid = persist.uidForDid(d) catch continue;
                        const current_host = persist.getAccountHostId(uid) catch continue;
                        if (current_host != 0 and current_host != pds_host_id) {
                            persist.setAccountHostId(uid, pds_host_id) catch {};
                            log.info("host updated via DID doc: {s} -> host {d}", .{ d, pds_host_id });
                        }
                    }
                }
            }
        }
    }

    /// evict a DID's cached signing key (e.g. on #identity event).
    /// the next commit from this DID will trigger a fresh resolution.
    pub fn evictKey(self: *Validator, did: []const u8) void {
        _ = self.cache.remove(did);
    }

    /// cache size (for diagnostics)
    pub fn cacheSize(self: *Validator) u32 {
        return self.cache.count();
    }

    /// resolve queue length (for diagnostics — non-blocking)
    pub fn resolveQueueLen(self: *Validator) usize {
        if (!self.queue_mutex.tryLock()) return 0;
        defer self.queue_mutex.unlock();
        return self.queue.items.len;
    }

    /// resolve dedup set size (for diagnostics — non-blocking)
    pub fn resolveQueuedSetCount(self: *Validator) u32 {
        if (!self.queue_mutex.tryLock()) return 0;
        defer self.queue_mutex.unlock();
        return self.queued_set.count();
    }

    /// signing key cache hashmap backing capacity (for memory attribution)
    pub fn cacheMapCapacity(self: *Validator) u32 {
        return self.cache.mapCapacity();
    }

    /// resolver dedup set hashmap backing capacity (for memory attribution — non-blocking)
    pub fn resolveQueuedSetCapacity(self: *Validator) u32 {
        if (!self.queue_mutex.tryLock()) return 0;
        defer self.queue_mutex.unlock();
        return self.queued_set.capacity();
    }

    pub const HostAuthority = enum { accept, migrate, reject };

    /// synchronous host authority check. called on first-seen DIDs (is_new)
    /// and host migrations (host_changed). resolves the DID doc to verify the
    /// PDS endpoint matches the incoming host. retries once on failure to
    /// handle transient network errors.
    ///
    /// returns:
    ///   .accept  — should not happen (caller should only call on new/mismatch)
    ///   .migrate — DID doc confirms this host, caller should update host_id
    ///   .reject  — DID doc does not confirm, caller should drop the event
    pub fn resolveHostAuthority(self: *Validator, did: []const u8, incoming_host_id: u64) HostAuthority {
        const persist = self.persist orelse return .migrate; // no DB — can't check

        var resolver = zat.DidResolver.initWithOptions(self.allocator, .{});
        defer resolver.deinit();

        const parsed = zat.Did.parse(did) orelse return .reject;

        // first resolve attempt
        var doc = resolver.resolve(parsed) catch {
            // retry once on network failure
            var doc2 = resolver.resolve(parsed) catch return .reject;
            defer doc2.deinit();
            return self.checkPdsHost(&doc2, persist, incoming_host_id);
        };
        defer doc.deinit();
        return self.checkPdsHost(&doc, persist, incoming_host_id);
    }

    fn checkPdsHost(self: *Validator, doc: *zat.DidDocument, persist: *event_log_mod.DiskPersist, incoming_host_id: u64) HostAuthority {
        _ = self;
        const pds_endpoint = doc.pdsEndpoint() orelse return .reject;
        const pds_host = extractHostFromUrl(pds_endpoint) orelse return .reject;
        const pds_host_id = (persist.getHostIdForHostname(pds_host) catch null) orelse return .reject;
        if (pds_host_id == incoming_host_id) return .migrate;
        return .reject;
    }
};

/// extract hostname from a URL like "https://pds.example.com" or "https://pds.example.com:443/path"
pub fn extractHostFromUrl(url: []const u8) ?[]const u8 {
    // strip scheme
    var rest = url;
    if (std.mem.startsWith(u8, rest, "https://")) {
        rest = rest["https://".len..];
    } else if (std.mem.startsWith(u8, rest, "http://")) {
        rest = rest["http://".len..];
    }
    // strip path
    if (std.mem.indexOfScalar(u8, rest, '/')) |i| {
        rest = rest[0..i];
    }
    // strip port
    if (std.mem.indexOfScalar(u8, rest, ':')) |i| {
        rest = rest[0..i];
    }
    if (rest.len == 0) return null;
    return rest;
}

fn parseEnvInt(comptime T: type, key: []const u8, default: T) T {
    const val = std.posix.getenv(key) orelse return default;
    return std.fmt.parseInt(T, val, 10) catch default;
}

// --- tests ---

test "validateCommit skips on cache miss" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    // build a commit payload using SDK
    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "seq", .value = .{ .unsigned = 42 } },
        .{ .key = "rev", .value = .{ .text = "3k2abc000000" } },
        .{ .key = "time", .value = .{ .text = "2024-01-15T10:30:00Z" } },
    } };

    const result = v.validateCommit(payload);
    try std.testing.expect(result.valid);
    try std.testing.expect(result.skipped);
    try std.testing.expectEqual(@as(u64, 1), stats.cache_misses.load(.acquire));
}

test "validateCommit skips when no repo field" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    // payload without "repo" field
    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "seq", .value = .{ .unsigned = 42 } },
    } };

    const result = v.validateCommit(payload);
    try std.testing.expect(result.valid);
    try std.testing.expect(result.skipped);
    try std.testing.expectEqual(@as(u64, 1), stats.skipped.load(.acquire));
}

test "checkCommitStructure rejects invalid DID" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "not-a-did" } },
    } };

    try std.testing.expectError(error.InvalidFrame, v.checkCommitStructure(payload));
}

test "checkCommitStructure accepts valid commit" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
    } };

    try v.checkCommitStructure(payload);
}

test "validateSync skips on cache miss" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "did", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "seq", .value = .{ .unsigned = 42 } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
        .{ .key = "blocks", .value = .{ .bytes = "deadbeef" } },
    } };

    const result = v.validateSync(payload);
    try std.testing.expect(result.valid);
    try std.testing.expect(result.skipped);
    try std.testing.expectEqual(@as(u64, 1), stats.cache_misses.load(.acquire));
}

test "validateSync rejects invalid DID" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "did", .value = .{ .text = "not-a-did" } },
        .{ .key = "blocks", .value = .{ .bytes = "deadbeef" } },
    } };

    const result = v.validateSync(payload);
    try std.testing.expect(!result.valid);
    try std.testing.expect(!result.skipped);
    try std.testing.expectEqual(@as(u64, 1), stats.failed.load(.acquire));
}

test "validateSync rejects missing blocks" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "did", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
    } };

    const result = v.validateSync(payload);
    try std.testing.expect(!result.valid);
    try std.testing.expect(!result.skipped);
    try std.testing.expectEqual(@as(u64, 1), stats.failed.load(.acquire));
}

test "validateSync skips when no did field" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "seq", .value = .{ .unsigned = 42 } },
    } };

    const result = v.validateSync(payload);
    try std.testing.expect(result.valid);
    try std.testing.expect(result.skipped);
    try std.testing.expectEqual(@as(u64, 1), stats.skipped.load(.acquire));
}

test "LRU cache evicts least recently used" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    v.cache.capacity = 3;
    defer v.deinit();

    const mk = CachedKey{ .key_type = .p256, .raw = .{0} ** 33, .len = 33 };

    try v.cache.put("did:plc:aaa", mk);
    try v.cache.put("did:plc:bbb", mk);
    try v.cache.put("did:plc:ccc", mk);

    // access "aaa" to promote it
    _ = v.cache.get("did:plc:aaa");

    // insert "ddd" — should evict "bbb" (LRU)
    try v.cache.put("did:plc:ddd", mk);

    try std.testing.expect(v.cache.get("did:plc:bbb") == null);
    try std.testing.expect(v.cache.get("did:plc:aaa") != null);
    try std.testing.expect(v.cache.get("did:plc:ccc") != null);
    try std.testing.expect(v.cache.get("did:plc:ddd") != null);
    try std.testing.expectEqual(@as(u32, 3), v.cache.count());
}

test "checkCommitStructure rejects too many ops" {
    var stats = broadcaster.Stats{};
    var v = Validator.initWithConfig(std.testing.allocator, &stats, .{ .max_ops = 2 });
    defer v.deinit();

    // build ops array with 3 items (over limit of 2)
    const ops = [_]zat.cbor.Value{
        .{ .map = &.{.{ .key = "action", .value = .{ .text = "create" } }} },
        .{ .map = &.{.{ .key = "action", .value = .{ .text = "create" } }} },
        .{ .map = &.{.{ .key = "action", .value = .{ .text = "create" } }} },
    };

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "ops", .value = .{ .array = &ops } },
    } };

    try std.testing.expectError(error.InvalidFrame, v.checkCommitStructure(payload));
}

// --- spec conformance tests ---

test "spec: #commit blocks > 2,000,000 bytes rejected" {
    // lexicon maxLength for #commit blocks: 2,000,000
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    // insert a fake cached key so we reach the blocks size check
    const did = "did:plc:test123";
    try v.cache.put(did, .{
        .key_type = .p256,
        .raw = .{0} ** 33,
        .len = 33,
        .resolve_time = 100,
    });

    // blocks with 2,000,001 bytes (1 byte over limit)
    const oversized_blocks = try std.testing.allocator.alloc(u8, 2_000_001);
    defer std.testing.allocator.free(oversized_blocks);
    @memset(oversized_blocks, 0);

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = did } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
        .{ .key = "blocks", .value = .{ .bytes = oversized_blocks } },
    } };

    const result = v.validateCommit(payload);
    try std.testing.expect(!result.valid or result.skipped);
}

test "spec: #commit blocks = 2,000,000 bytes accepted (boundary)" {
    // lexicon maxLength for #commit blocks: 2,000,000 — exactly at limit should pass size check
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const did = "did:plc:test123";
    try v.cache.put(did, .{
        .key_type = .p256,
        .raw = .{0} ** 33,
        .len = 33,
        .resolve_time = 100,
    });

    // exactly 2,000,000 bytes — should pass size check (may fail signature verify, that's ok)
    const exact_blocks = try std.testing.allocator.alloc(u8, 2_000_000);
    defer std.testing.allocator.free(exact_blocks);
    @memset(exact_blocks, 0);

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = did } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
        .{ .key = "blocks", .value = .{ .bytes = exact_blocks } },
    } };

    const result = v.validateCommit(payload);
    // should not be rejected for size — may fail signature verification (that's fine,
    // it means we passed the size check). with P1.1c, sig failure → skipped=true.
    try std.testing.expect(result.valid or result.skipped);
}

test "spec: #sync blocks > 10,000 bytes rejected" {
    // lexicon maxLength for #sync blocks: 10,000
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "did", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
        .{ .key = "blocks", .value = .{ .bytes = &([_]u8{0} ** 10_001) } },
    } };

    const result = v.validateSync(payload);
    try std.testing.expect(!result.valid);
    try std.testing.expect(!result.skipped);
}

test "spec: #sync blocks = 10,000 bytes accepted (boundary)" {
    // lexicon maxLength for #sync blocks: 10,000 — exactly at limit should pass size check
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "did", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "rev", .value = .{ .text = "3k2abcdefghij" } },
        .{ .key = "blocks", .value = .{ .bytes = &([_]u8{0} ** 10_000) } },
    } };

    const result = v.validateSync(payload);
    // should pass size check — will be a cache miss → skipped (no cached key)
    try std.testing.expect(result.valid);
    try std.testing.expect(result.skipped);
}

test "extractOps reads path field from firehose format" {
    var stats = broadcaster.Stats{};
    var v = Validator.initWithConfig(std.testing.allocator, &stats, .{ .verify_commit_diff = true });
    defer v.deinit();

    // use arena since extractOps allocates an ArrayList internally
    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
    defer arena.deinit();

    const ops = [_]zat.cbor.Value{
        .{ .map = &.{
            .{ .key = "action", .value = .{ .text = "create" } },
            .{ .key = "path", .value = .{ .text = "app.bsky.feed.post/3k2abc000000" } },
            .{ .key = "cid", .value = .{ .cid = .{ .raw = "fakecid12345" } } },
        } },
        .{ .map = &.{
            .{ .key = "action", .value = .{ .text = "delete" } },
            .{ .key = "path", .value = .{ .text = "app.bsky.feed.like/3k2def000000" } },
        } },
    };

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "ops", .value = .{ .array = &ops } },
    } };

    const result = v.extractOps(arena.allocator(), payload);
    try std.testing.expect(result != null);
    try std.testing.expectEqual(@as(usize, 2), result.?.len);
    try std.testing.expectEqualStrings("app.bsky.feed.post/3k2abc000000", result.?[0].path);
    try std.testing.expectEqualStrings("app.bsky.feed.like/3k2def000000", result.?[1].path);
    try std.testing.expect(result.?[0].value != null); // create has cid
    try std.testing.expect(result.?[1].value == null); // delete has no cid
}

test "extractOps rejects malformed path without slash" {
    var stats = broadcaster.Stats{};
    var v = Validator.initWithConfig(std.testing.allocator, &stats, .{ .verify_commit_diff = true });
    defer v.deinit();

    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
    defer arena.deinit();

    const ops = [_]zat.cbor.Value{
        .{ .map = &.{
            .{ .key = "action", .value = .{ .text = "create" } },
            .{ .key = "path", .value = .{ .text = "noslash" } },
            .{ .key = "cid", .value = .{ .cid = .{ .raw = "fakecid12345" } } },
        } },
    };

    const payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "ops", .value = .{ .array = &ops } },
    } };

    // malformed path (no slash) → all ops skipped → returns null
    const result = v.extractOps(arena.allocator(), payload);
    try std.testing.expect(result == null);
}

test "checkCommitStructure validates path field" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    // valid path
    const valid_ops = [_]zat.cbor.Value{
        .{ .map = &.{
            .{ .key = "action", .value = .{ .text = "create" } },
            .{ .key = "path", .value = .{ .text = "app.bsky.feed.post/3k2abc000000" } },
        } },
    };

    const valid_payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "ops", .value = .{ .array = &valid_ops } },
    } };

    try v.checkCommitStructure(valid_payload);

    // invalid collection in path
    const invalid_ops = [_]zat.cbor.Value{
        .{ .map = &.{
            .{ .key = "action", .value = .{ .text = "create" } },
            .{ .key = "path", .value = .{ .text = "not-an-nsid/3k2abc000000" } },
        } },
    };

    const invalid_payload: zat.cbor.Value = .{ .map = &.{
        .{ .key = "repo", .value = .{ .text = "did:plc:test123" } },
        .{ .key = "ops", .value = .{ .array = &invalid_ops } },
    } };

    try std.testing.expectError(error.InvalidFrame, v.checkCommitStructure(invalid_payload));
}

test "queueResolve deduplicates repeated DIDs" {
    var stats = broadcaster.Stats{};
    var v = Validator.init(std.testing.allocator, &stats);
    defer v.deinit();

    // queue the same DID 100 times
    for (0..100) |_| {
        v.queueResolve("did:plc:duplicate");
    }

    // should have exactly 1 entry, not 100
    try std.testing.expectEqual(@as(usize, 1), v.queue.items.len);
    try std.testing.expectEqual(@as(u32, 1), v.queued_set.count());
}