const std = @import("std");

pub fn build(b: *std.Build) void {
    // Default to ReleaseSafe because Debug pulls Zig's
    // UBSan runtime and other sanitization, which needs
    // f128/SSE ops, which i don't provide.
    const optimize = b.option(std.builtin.OptimizeMode, "optimize", "optimize mode") orelse .ReleaseSafe;

    // The kernel must NOT touch SSE/MMX/AVX until it has
    // enabled them itself, so I strip those features and
    // let the compiler use a soft-float ABI
    // `code_model = .kernel` keeps relocations valid for
    // the higher-half load address in boot/linker.ld.
    //
    // In other words. Going raw baby
    var query: std.Target.Query = .{
        .cpu_arch = .x86_64,
        .os_tag = .freestanding,
        .abi = .none,
    };
    const Feature = std.Target.x86.Feature;
    query.cpu_features_sub.addFeature(@intFromEnum(Feature.mmx));
    query.cpu_features_sub.addFeature(@intFromEnum(Feature.sse));
    query.cpu_features_sub.addFeature(@intFromEnum(Feature.sse2));
    query.cpu_features_sub.addFeature(@intFromEnum(Feature.avx));
    query.cpu_features_sub.addFeature(@intFromEnum(Feature.avx2));
    query.cpu_features_add.addFeature(@intFromEnum(Feature.soft_float));

    const target = b.resolveTargetQuery(query);

    const kernel = b.addExecutable(.{
        .name = "revel",
        .root_module = b.createModule(.{
            .root_source_file = b.path("boot/boot.zig"),
            .target = target,
            .optimize = optimize,
            .code_model = .kernel,
            .red_zone = false,
            .single_threaded = true,
            .link_libc = false,
        }),
    });
    kernel.entry = .{ .symbol_name = "_start" };
    kernel.pie = false;
    kernel.setLinkerScript(b.path("boot/linker.ld"));

    // the big guns
    const revo_dep = b.dependency("revo", .{ .target = target, .optimize = optimize });
    const revo_mod = revo_dep.module("revo");

    var visited: std.AutoHashMap(*std.Build.Module, void) = .init(b.allocator);
    defer visited.deinit();
    kernelize(revo_mod, &visited);

    // the thin guns
    const bridge_mod = b.createModule(.{
        .root_source_file = b.path("bridge/bridge.zig"),
        .target = target,
        .optimize = optimize,
        .code_model = .kernel,
        .red_zone = false,
        .single_threaded = true,
        .link_libc = false,
    });
    bridge_mod.addImport("revo", revo_mod);
    // the OS source lives in kernel/*.rv; @embedFile("kernel_main") in the bridge
    // pulls it in at build time (an anonymous import lets it cross the module dir)
    bridge_mod.addAnonymousImport("kernel_main", .{ .root_source_file = b.path("kernel/main.rv") });

    kernel.root_module.addImport("bridge", bridge_mod);

    b.installArtifact(kernel);
}

// force a module and everything it imports to the kernel's codegen settings
fn kernelize(mod: *std.Build.Module, visited: *std.AutoHashMap(*std.Build.Module, void)) void {
    if (visited.contains(mod)) return;
    visited.put(mod, {}) catch @panic("OOM building module graph");

    mod.code_model = .kernel;
    mod.red_zone = false;
    mod.single_threaded = true;

    var it = mod.import_table.iterator();
    while (it.next()) |entry| kernelize(entry.value_ptr.*, visited);
}