const std = @import("std");
const builtin = @import("builtin");

comptime {
    if (builtin.zig_version.major != 0 or builtin.zig_version.minor != 16) {
        @compileError("nxdns requires Zig 0.16.x, found " ++ builtin.zig_version_string);
    }
}

const cross_targets = [_][]const u8{
    "x86_64-linux-musl",
    "aarch64-linux-musl",
};

pub fn build(b: *std.Build) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    const integration = b.option(bool, "integration", "Run hermetic integration tests (loopback sockets only)") orelse false;
    const live = b.option(bool, "live", "Run tests that reach external network hosts") orelse false;
    const fuzz = b.option(bool, "fuzz", "Build the fuzz targets with the LLVM backend (required for --fuzz)") orelse false;
    const version_string = b.option([]const u8, "version-string", "Version reported by `nxdns version`") orelse "0.1.0-dev";
    const git_commit = b.option([]const u8, "git-commit", "Git commit reported by `nxdns version`") orelse "unknown";
    const web_dist = b.option(
        []const u8,
        "web-dist",
        "Built web UI directory to embed (default: the placeholder page). " ++
            "Only the exact value `web/dist` gets the freshness check; " ++
            "the placeholder and any other path skip it.",
    ) orelse "web/dist-placeholder";

    // `b.path` panics on absolute paths, and a CI artifact directory is one.
    const web_dist_path: std.Build.LazyPath = if (std.fs.path.isAbsolute(web_dist))
        .{ .cwd_relative = web_dist }
    else
        b.path(web_dist);

    // A stale `web/dist` shipped a crashing settings page once (milestone-15
    // ruling 5). The stamp is checked only for the real dist tree: the
    // placeholder has no sources to be stale against, and an explicit path is a
    // CI artifact that was built elsewhere.
    const web_dist_check: ?*std.Build.Step = if (std.mem.eql(u8, web_dist, "web/dist")) check: {
        const run_check = b.addSystemCommand(&.{"node"});
        // The script path goes through `b.path` so it resolves against the
        // build root: `zig build` run from any other directory would not find
        // a cwd-relative one.
        run_check.addFileArg(b.path("web/scripts/stamp-dist.mjs"));
        run_check.addArg("--check");
        break :check &run_check.step;
    } else null;
    const web_assets = webAssetsIndex(b, web_dist_path, web_dist_check);

    const options = b.addOptions();
    options.addOption(bool, "integration", integration);
    options.addOption(bool, "live", live);
    options.addOption([]const u8, "version_string", version_string);
    options.addOption([]const u8, "git_commit", git_commit);
    options.addOption([]const u8, "zig_version_string", builtin.zig_version_string);

    const exe = addExecutable(b, target, optimize, options, web_assets);
    b.installArtifact(exe);

    const run = b.addRunArtifact(exe);
    run.step.dependOn(b.getInstallStep());
    if (b.args) |args| run.addArgs(args);
    b.step("run", "Run nxdns").dependOn(&run.step);

    // Zig collects tests only from the root module, so a file missing from
    // src/tests.zig silently contributes no tests. The list stays hand-written
    // (generating it from a staged copy would point diagnostics at cache
    // paths); this makes it complete by construction instead.
    checkTestImports(b);

    // A successful `zig build test` still prints `failed command: .../test
    // ... --listen=-` as its last line. This is an upstream zig 0.16.0
    // build-runner labelling defect, not a failure here, and not something
    // this build script can suppress without hiding real failures.
    //
    // Mechanism, verified against the 0.16.0 sources on 2026-08-07:
    //   - std/Build/Step/Run.zig:1540 sets `result_failed_command` for every
    //     spawn, unconditionally ("if an error occurs, it's caused by this
    //     command"). Nothing clears it when the child succeeds.
    //   - compiler/build_runner.zig:1381 prints a step's diagnostics whenever
    //     `result_stderr` is non-empty, explicitly "no matter the result".
    //   - compiler/build_runner.zig:1515, reached from there, emits the
    //     `failed command: ` line because `result_failed_command` is non-null.
    // So any Run step that both succeeds and writes one byte to stderr gets
    // the label. Our suite writes plenty: the tests that exercise the warning
    // paths log through the real sink.
    //
    // Minimal reproducer, no mbedTLS and no C: one passing test whose body is
    // `std.debug.print` plus `try expect(true)`, in a build.zig with nothing
    // but `addTest` + `addRunArtifact`. It prints the label and reports
    // "3/3 steps succeeded; 1/1 tests passed". Deleting the print removes the
    // label. The test child does not crash and does not abort in teardown.
    // (Running the cached test binary by hand with `--listen=-` does abort,
    // but only because stdin is then closed and the IPC runner panics on
    // `EndOfStream`; that is an artifact of the manual invocation.)
    //
    // No upstream issue matched a search of ziglang/zig for this behaviour;
    // the reference is the 0.16.0 source lines above. See AGENTS.md.
    const tests = b.addTest(.{
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/tests.zig"),
            .target = target,
            .optimize = optimize,
            .link_libc = true,
        }),
    });
    tests.root_module.addOptions("build_options", options);
    tests.root_module.linkLibrary(sqliteLibrary(b, target, optimize));
    tests.root_module.linkLibrary(mbedtlsLibrary(b, target, optimize));
    tests.root_module.addCSourceFile(.{ .file = b.path("src/platform/mbedtls_shim.c") });
    addMbedtlsThreadingMacros(tests.root_module);
    tests.root_module.addAnonymousImport("test_fixtures", .{
        .root_source_file = b.path("tests/fixtures/fixtures.zig"),
    });
    tests.root_module.addAnonymousImport("docs_files", .{
        .root_source_file = b.path("docs/docs.zig"),
    });
    tests.root_module.addAnonymousImport("web_assets", .{ .root_source_file = web_assets });
    const test_step = b.step("test", "Run the test suite");
    test_step.dependOn(&b.addRunArtifact(tests).step);

    // Fuzz targets compile as a second test artifact with `dns` as a named module
    // (a file belongs to one module per compilation; the aggregator keeps owning
    // the in-file tests). `-Dfuzz` opts into the LLVM backend, which `--fuzz`
    // needs for sanitizer coverage; stock 0.16.0 also requires a patched
    // test_runner.zig for fuzz mode — see specs/milestone-2.md.
    const dns_mod = b.createModule(.{
        .root_source_file = b.path("src/dns/dns.zig"),
        .target = target,
        .optimize = optimize,
    });
    const fuzz_mod = b.createModule(.{
        .root_source_file = b.path("tests/fuzz/dns_fuzz.zig"),
        .target = target,
        .optimize = optimize,
    });
    fuzz_mod.addImport("dns", dns_mod);
    const fuzz_tests = b.addTest(.{
        .name = "fuzz",
        .use_llvm = if (fuzz) true else null,
        .root_module = fuzz_mod,
    });
    test_step.dependOn(&b.addRunArtifact(fuzz_tests).step);

    const parsers_mod = b.createModule(.{
        .root_source_file = b.path("src/filter/parsers.zig"),
        .target = target,
        .optimize = optimize,
    });
    const blocklist_fuzz_mod = b.createModule(.{
        .root_source_file = b.path("tests/fuzz/blocklist_fuzz.zig"),
        .target = target,
        .optimize = optimize,
    });
    blocklist_fuzz_mod.addImport("parsers", parsers_mod);
    const blocklist_fuzz_tests = b.addTest(.{
        .name = "blocklist-fuzz",
        .use_llvm = if (fuzz) true else null,
        .root_module = blocklist_fuzz_mod,
    });
    test_step.dependOn(&b.addRunArtifact(blocklist_fuzz_tests).step);

    // `src/web/http_util.zig` imports only std, so its fuzz module roots
    // directly at the file — no aggregator needed (milestone-15 ruling 6c).
    const http_util_mod = b.createModule(.{
        .root_source_file = b.path("src/web/http_util.zig"),
        .target = target,
        .optimize = optimize,
    });
    const http_util_fuzz_mod = b.createModule(.{
        .root_source_file = b.path("tests/fuzz/http_util_fuzz.zig"),
        .target = target,
        .optimize = optimize,
    });
    http_util_fuzz_mod.addImport("http_util", http_util_mod);
    const http_util_fuzz_tests = b.addTest(.{
        .name = "http-util-fuzz",
        .use_llvm = if (fuzz) true else null,
        .root_module = http_util_fuzz_mod,
    });
    test_step.dependOn(&b.addRunArtifact(http_util_fuzz_tests).step);

    // The bench harness (milestone-12 ruling 1). The measured roots
    // (matcher.zig, dns_cache.zig, compiler.zig) share files in their relative
    // import closures (model.zig, types.zig, ...), and a file may belong to
    // only one module per compilation — separate modules per root cannot link
    // into one executable. So one staged module: a copy of src/ plus a
    // generated aggregator root, imported by the bench as `core`. No sqlite,
    // no mbedTLS: the closure is pure Zig.
    //
    // The compiler fuzz target reuses the same staged tree (milestone-15
    // ruling 6b): `compiler.zig` imports `../dns/`, so a module rooted under
    // `src/filter/` fails with ImportOutsideModulePath.
    const bench_stage = b.addWriteFiles();
    _ = bench_stage.addCopyDirectory(b.path("src"), "src", .{});
    const bench_core = bench_stage.add("bench_core.zig",
        \\pub const matcher = @import("src/filter/matcher.zig");
        \\pub const dns_cache = @import("src/cache/dns_cache.zig");
        \\pub const compiler = @import("src/filter/compiler.zig");
        \\pub const model = @import("src/config/model.zig");
        \\pub const dns_name = @import("src/dns/name.zig");
        \\pub const dns_types = @import("src/dns/types.zig");
        \\pub const packet = @import("src/dns/packet.zig");
        \\
    );
    const bench_core_mod = b.createModule(.{
        .root_source_file = bench_core,
        .target = target,
        .optimize = optimize,
    });
    const compiler_fuzz_mod = b.createModule(.{
        .root_source_file = b.path("tests/fuzz/compiler_fuzz.zig"),
        .target = target,
        .optimize = optimize,
    });
    compiler_fuzz_mod.addImport("core", bench_core_mod);
    const compiler_fuzz_tests = b.addTest(.{
        .name = "compiler-fuzz",
        .use_llvm = if (fuzz) true else null,
        .root_module = compiler_fuzz_mod,
    });
    test_step.dependOn(&b.addRunArtifact(compiler_fuzz_tests).step);

    const bench_mod = b.createModule(.{
        .root_source_file = b.path("tools/bench.zig"),
        .target = target,
        .optimize = optimize,
    });
    bench_mod.addImport("core", bench_core_mod);
    const bench_exe = b.addExecutable(.{ .name = "bench", .root_module = bench_mod });
    const bench_run = b.addRunArtifact(bench_exe);
    if (b.args) |args| bench_run.addArgs(args);
    b.step("bench", "Run the performance benchmarks (PLAN §18)").dependOn(&bench_run.step);

    // aarch64 test execution (milestone-12 ruling 6): the plain suite
    // cross-built for the deploy target and run under qemu-user
    // (`zig build test-aarch64 -fqemu`). Fuzz artifacts stay native-only, and
    // -Dintegration stays out (ruling 7): qemu-user's slowdown makes the
    // wall-clock-budgeted loopback TLS tests a flake source.
    const aarch64_target = b.resolveTargetQuery(
        std.Target.Query.parse(.{ .arch_os_abi = "aarch64-linux-musl" }) catch unreachable,
    );
    const aarch64_tests = b.addTest(.{
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/tests.zig"),
            .target = aarch64_target,
            .optimize = optimize,
            .link_libc = true,
        }),
    });
    aarch64_tests.linkage = .static;
    aarch64_tests.root_module.addOptions("build_options", options);
    aarch64_tests.root_module.linkLibrary(sqliteLibrary(b, aarch64_target, optimize));
    aarch64_tests.root_module.linkLibrary(mbedtlsLibrary(b, aarch64_target, optimize));
    aarch64_tests.root_module.addCSourceFile(.{ .file = b.path("src/platform/mbedtls_shim.c") });
    addMbedtlsThreadingMacros(aarch64_tests.root_module);
    aarch64_tests.root_module.addAnonymousImport("test_fixtures", .{
        .root_source_file = b.path("tests/fixtures/fixtures.zig"),
    });
    aarch64_tests.root_module.addAnonymousImport("docs_files", .{
        .root_source_file = b.path("docs/docs.zig"),
    });
    aarch64_tests.root_module.addAnonymousImport("web_assets", .{ .root_source_file = web_assets });
    const aarch64_run = b.addRunArtifact(aarch64_tests);
    aarch64_run.skip_foreign_checks = true;
    b.step("test-aarch64", "Run the test suite for aarch64-linux-musl (use -fqemu)")
        .dependOn(&aarch64_run.step);

    const cross = b.step("cross", "Build static musl executables for every deploy target");
    for (cross_targets) |triple| {
        const query = std.Target.Query.parse(.{ .arch_os_abi = triple }) catch |err| {
            std.debug.panic("invalid cross target '{s}': {t}", .{ triple, err });
        };
        const cross_exe = addExecutable(b, b.resolveTargetQuery(query), optimize, options, web_assets);
        cross_exe.linkage = .static;
        const install = b.addInstallArtifact(cross_exe, .{
            .dest_dir = .{ .override = .{ .custom = b.fmt("cross/{s}", .{triple}) } },
        });
        cross.dependOn(&install.step);
    }
}

/// Milestone-15 ruling 4: every `*.zig` under `src/` must appear in
/// `src/tests.zig` as a line that trims to exactly `_ = @import("<path>");`,
/// where `<path>` is relative to `src/`. Whole-line equality, not a substring
/// search: a commented-out import trims to a line starting with `//` and does
/// not match, and `db.zig` cannot satisfy the requirement for `db2.zig`.
/// Duplicate lines are an error too — they hide a botched merge. No allowlist:
/// a file with no tests still gets imported, because the import is free and an
/// exception is the thing that lets a real gap through.
fn checkTestImports(b: *std.Build) void {
    const gpa = b.allocator;
    const io = b.graph.io;
    const root = b.build_root.handle;

    const tests_src = root.readFileAlloc(io, "src/tests.zig", gpa, .limited(4 << 20)) catch |err| {
        std.process.fatal("cannot read src/tests.zig: {t}", .{err});
    };

    var src_dir = root.openDir(io, "src", .{ .iterate = true }) catch |err| {
        std.process.fatal("cannot open src/: {t}", .{err});
    };
    defer src_dir.close(io);

    var walker = src_dir.walk(gpa) catch @panic("OOM");
    defer walker.deinit();

    while (walker.next(io) catch |err| {
        std.process.fatal("cannot walk src/: {t}", .{err});
    }) |entry| {
        if (entry.kind != .file) continue;
        if (!std.mem.endsWith(u8, entry.path, ".zig")) continue;
        if (std.mem.eql(u8, entry.path, "tests.zig")) continue;

        const needle = b.fmt("_ = @import(\"{s}\");", .{entry.path});
        var matches: usize = 0;
        var lines = std.mem.splitScalar(u8, tests_src, '\n');
        while (lines.next()) |line| {
            if (std.mem.eql(u8, std.mem.trim(u8, line, " \t\r"), needle)) matches += 1;
        }
        if (matches == 0) {
            std.process.fatal("src/tests.zig is missing `{s}`", .{needle});
        }
        if (matches > 1) {
            std.process.fatal("src/tests.zig repeats `{s}` {d} times", .{ needle, matches });
        }
    }
}

fn addExecutable(
    b: *std.Build,
    target: std.Build.ResolvedTarget,
    optimize: std.builtin.OptimizeMode,
    options: *std.Build.Step.Options,
    web_assets: std.Build.LazyPath,
) *std.Build.Step.Compile {
    const exe = b.addExecutable(.{
        .name = "nxdns",
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/main.zig"),
            .target = target,
            .optimize = optimize,
            .link_libc = true,
        }),
    });
    exe.root_module.addOptions("build_options", options);
    exe.root_module.addAnonymousImport("web_assets", .{ .root_source_file = web_assets });
    exe.root_module.linkLibrary(sqliteLibrary(b, target, optimize));
    exe.root_module.linkLibrary(mbedtlsLibrary(b, target, optimize));
    exe.root_module.addCSourceFile(.{ .file = b.path("src/platform/mbedtls_shim.c") });
    addMbedtlsThreadingMacros(exe.root_module);
    return exe;
}

/// The embedded web UI (milestone-8 ruling 24): the dist directory plus the
/// generated `assets.zig` index and build-time gzip siblings, merged into one
/// WriteFiles directory so every `@embedFile` path resolves inside the module
/// root. Returns the index file, the root of the `web_assets` module.
///
/// The dist is staged through its own WriteFiles step before it reaches the
/// tool because a Run step hashes only the resolved path string of a directory
/// argument, not its contents; the staged copy lives at a content-hashed path,
/// so editing an asset re-runs the tool instead of replaying a stale cache.
fn webAssetsIndex(
    b: *std.Build,
    dist: std.Build.LazyPath,
    freshness_check: ?*std.Build.Step,
) std.Build.LazyPath {
    const stage = b.addWriteFiles();
    if (freshness_check) |check| stage.step.dependOn(check);
    const staged = stage.addCopyDirectory(dist, ".", .{});

    const tool = b.addExecutable(.{
        .name = "gen_web_assets",
        .root_module = b.createModule(.{
            .root_source_file = b.path("tools/gen_web_assets.zig"),
            .target = b.graph.host,
            .optimize = .ReleaseSafe,
        }),
    });

    const run = b.addRunArtifact(tool);
    run.addDirectoryArg(staged);
    const generated = run.addOutputDirectoryArg("web_assets");

    const merged = b.addWriteFiles();
    _ = merged.addCopyDirectory(staged, ".", .{});
    _ = merged.addCopyDirectory(generated, ".", .{});
    return merged.getDirectory().path(b, "assets.zig");
}

/// SQLite 3.53.4 amalgamation (see build.zig.zon for the pinned URL and hash).
fn sqliteLibrary(
    b: *std.Build,
    target: std.Build.ResolvedTarget,
    optimize: std.builtin.OptimizeMode,
) *std.Build.Step.Compile {
    const dep = b.dependency("sqlite", .{});
    const lib = b.addLibrary(.{
        .name = "sqlite3",
        .linkage = .static,
        .root_module = b.createModule(.{
            .target = target,
            .optimize = optimize,
            .link_libc = true,
        }),
    });
    lib.root_module.addIncludePath(dep.path(""));
    lib.root_module.addCSourceFile(.{
        .file = dep.path("sqlite3.c"),
        .flags = &.{
            "-DSQLITE_ENABLE_FTS5",
            "-DSQLITE_THREADSAFE=1",
            "-DSQLITE_DEFAULT_WAL_SYNCHRONOUS=1",
            "-DSQLITE_OMIT_LOAD_EXTENSION",
        },
    });
    return lib;
}

/// Mbed TLS 3.6.7 LTS, stock `mbedtls_config.h` (see build.zig.zon for the pinned URL and hash).
fn mbedtlsLibrary(
    b: *std.Build,
    target: std.Build.ResolvedTarget,
    optimize: std.builtin.OptimizeMode,
) *std.Build.Step.Compile {
    const dep = b.dependency("mbedtls", .{});
    const lib = b.addLibrary(.{
        .name = "mbedtls",
        .linkage = .static,
        .root_module = b.createModule(.{
            .target = target,
            .optimize = optimize,
            .link_libc = true,
        }),
    });

    addMbedtlsThreadingMacros(lib.root_module);

    for ([_][]const u8{
        "include",
        "library",
        "3rdparty/everest/include",
        "3rdparty/everest/include/everest",
        "3rdparty/everest/include/everest/kremlib",
        "3rdparty/p256-m/p256-m/include",
        "3rdparty/p256-m/p256-m_driver_interface",
    }) |include_dir| {
        lib.root_module.addIncludePath(dep.path(include_dir));
    }

    lib.root_module.addCSourceFiles(.{
        .root = dep.path("library"),
        .files = &mbedtls_library_sources,
    });
    lib.root_module.addCSourceFiles(.{
        .root = dep.path("3rdparty"),
        .files = &mbedtls_3rdparty_sources,
    });
    lib.installHeadersDirectory(dep.path("include/mbedtls"), "mbedtls", .{});
    lib.installHeadersDirectory(dep.path("include/psa"), "psa", .{});
    return lib;
}

/// Context sizes change with threading enabled, so every compilation unit that
/// includes mbedTLS headers (the library itself and `mbedtls_shim.c`) must see
/// the same macros. Concurrent handshakes share `ssl_config`, the CTR-DRBG, and
/// global PSA state; without MBEDTLS_THREADING_C those race.
fn addMbedtlsThreadingMacros(m: *std.Build.Module) void {
    m.addCMacro("MBEDTLS_THREADING_C", "1");
    m.addCMacro("MBEDTLS_THREADING_PTHREAD", "1");
}

/// Every `library/*.c` of the release, matching `library/Makefile`.
const mbedtls_library_sources = [_][]const u8{
    "aes.c",                        "aesce.c",
    "aesni.c",                      "aria.c",
    "asn1parse.c",                  "asn1write.c",
    "base64.c",                     "bignum.c",
    "bignum_core.c",                "bignum_mod.c",
    "bignum_mod_raw.c",             "block_cipher.c",
    "camellia.c",                   "ccm.c",
    "chacha20.c",                   "chachapoly.c",
    "cipher.c",                     "cipher_wrap.c",
    "cmac.c",                       "constant_time.c",
    "ctr_drbg.c",                   "debug.c",
    "des.c",                        "dhm.c",
    "ecdh.c",                       "ecdsa.c",
    "ecjpake.c",                    "ecp.c",
    "ecp_curves.c",                 "ecp_curves_new.c",
    "entropy.c",                    "entropy_poll.c",
    "error.c",                      "gcm.c",
    "hkdf.c",                       "hmac_drbg.c",
    "lmots.c",                      "lms.c",
    "md.c",                         "md5.c",
    "memory_buffer_alloc.c",        "mps_reader.c",
    "mps_trace.c",                  "net_sockets.c",
    "nist_kw.c",                    "oid.c",
    "padlock.c",                    "pem.c",
    "pk.c",                         "pk_ecc.c",
    "pk_wrap.c",                    "pkcs12.c",
    "pkcs5.c",                      "pkcs7.c",
    "pkparse.c",                    "pkwrite.c",
    "platform.c",                   "platform_util.c",
    "poly1305.c",                   "psa_crypto.c",
    "psa_crypto_aead.c",            "psa_crypto_cipher.c",
    "psa_crypto_client.c",          "psa_crypto_driver_wrappers_no_static.c",
    "psa_crypto_ecp.c",             "psa_crypto_ffdh.c",
    "psa_crypto_hash.c",            "psa_crypto_mac.c",
    "psa_crypto_pake.c",            "psa_crypto_random.c",
    "psa_crypto_rsa.c",             "psa_crypto_se.c",
    "psa_crypto_slot_management.c", "psa_crypto_storage.c",
    "psa_its_file.c",               "psa_util.c",
    "ripemd160.c",                  "rsa.c",
    "rsa_alt_helpers.c",            "sha1.c",
    "sha256.c",                     "sha3.c",
    "sha512.c",                     "ssl_cache.c",
    "ssl_ciphersuites.c",           "ssl_client.c",
    "ssl_cookie.c",                 "ssl_debug_helpers_generated.c",
    "ssl_msg.c",                    "ssl_ticket.c",
    "ssl_tls.c",                    "ssl_tls12_client.c",
    "ssl_tls12_server.c",           "ssl_tls13_client.c",
    "ssl_tls13_generic.c",          "ssl_tls13_keys.c",
    "ssl_tls13_server.c",           "threading.c",
    "timing.c",                     "version.c",
    "version_features.c",           "x509.c",
    "x509_create.c",                "x509_crl.c",
    "x509_crt.c",                   "x509_csr.c",
    "x509write.c",                  "x509write_crt.c",
    "x509write_csr.c",
};

/// The object lists of `3rdparty/everest/Makefile.inc` and `3rdparty/p256-m/Makefile.inc`.
/// The stock config enables neither driver, so these compile to empty objects.
const mbedtls_3rdparty_sources = [_][]const u8{
    "everest/library/everest.c",
    "everest/library/x25519.c",
    "everest/library/Hacl_Curve25519_joined.c",
    "p256-m/p256-m_driver_entrypoints.c",
    "p256-m/p256-m/p256-m.c",
};