engine/build.zig

const std = @import("std");
const Build = std.Build;
const Step = Build.Step;
const GenerateAssetManifest = @import("tools/GenerateAssetManifest.zig");

// Although this function looks imperative, note that its job is to
// declaratively construct a build graph that will be executed by an external
// runner.
pub fn build(b: *Build) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});
    // Standard optimization options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
    // set a preferred release mode, allowing the user to decide how to optimize.
    const optimize = b.standardOptimizeOption(.{});

    const buildOptimize = b.option(
        std.builtin.OptimizeMode,
        "boptimize",
        "Prioritize performance, safety, or binary size for build time tools",
    ) orelse .Debug;

    const zalgebra_dep = b.dependency("zalgebra", .{});

    const assets_mod = b.addModule("assets", .{ .root_source_file = .{ .path = "src/assets/root.zig" } });
    const asset_manifest_mod = b.addModule("asset_manifest", .{ .root_source_file = .{ .path = "src/gen/asset_manifest.zig" } });
    asset_manifest_mod.addImport("assets", assets_mod);

    const assets_step = b.step("assets", "Build and install assets");
    b.getInstallStep().dependOn(assets_step);

    const assetc = buildAssetCompiler(b, buildOptimize);

    const install_assetc_step = b.addInstallArtifact(assetc, .{ .dest_dir = .{ .override = .prefix } });
    assets_step.dependOn(&install_assetc_step.step);

    assetc.root_module.addImport("assets", assets_mod);

    const gen_asset_manifest = buildAssets(b, &install_assetc_step.step, assets_step, assetc, "assets") catch |err| {
        std.log.err("Failed to build assets {}\n", .{err});
        @panic("buildAssets");
    };
    const gen_asset_manifest_mod = b.createModule(.{ .root_source_file = gen_asset_manifest });
    gen_asset_manifest_mod.addImport("assets", assets_mod);
    asset_manifest_mod.addImport("asset_manifest_gen", gen_asset_manifest_mod);

    const lib = b.addSharedLibrary(.{
        .name = "learnopengl",
        .root_source_file = .{ .path = "src/game.zig" },
        .target = target,
        .optimize = optimize,
    });
    const lib_unit_tests = b.addTest(.{
        .root_source_file = .{ .path = "src/game.zig" },
        .target = target,
        .optimize = optimize,
    });
    const lib_compiles = [_]*Step.Compile{ lib, lib_unit_tests };

    inline for (lib_compiles) |l| {
        l.root_module.addImport("zalgebra", zalgebra_dep.module("zalgebra"));
        l.root_module.addImport("assets", assets_mod);
        l.root_module.addImport("asset_manifest", asset_manifest_mod);
    }

    const install_lib = b.addInstallArtifact(lib, .{ .dest_dir = .{ .override = .prefix } });
    b.getInstallStep().dependOn(&install_lib.step);

    const exe = b.addExecutable(.{
        .name = "learnopengl",
        // In this case the main source file is merely a path, however, in more
        // complicated build scripts, this could be a generated file.
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    });

    if (b.systemIntegrationOption("SDL2", .{ .default = b.host.result.os.tag != .windows })) {
        exe.linkSystemLibrary("SDL2");
        inline for (lib_compiles) |l| {
            l.linkSystemLibrary("SDL2");
        }
    } else {
        const sdl_dep = b.dependency("SDL", .{
            .target = target,
            .optimize = .ReleaseSafe,
        });

        const sdl2 = sdl_dep.artifact("SDL2");
        b.getInstallStep().dependOn(&b.addInstallArtifact(sdl2, .{ .dest_dir = .{ .override = .prefix } }).step);
        exe.linkLibrary(sdl2);

        inline for (lib_compiles) |l| {
            l.linkLibrary(sdl2);
        }
    }

    // This declares intent for the executable to be installed into the
    // standard location when the user invokes the "install" step (the default
    // step when running `zig build`).
    const install_exe = b.addInstallArtifact(exe, .{ .dest_dir = .{ .override = .prefix } });
    b.getInstallStep().dependOn(&install_exe.step);

    // This *creates* a Run step in the build graph, to be executed when another
    // step is evaluated that depends on it. The next line below will establish
    // such a dependency.
    const run_cmd = b.addRunArtifact(exe);

    // By making the run step depend on the install step, it will be run from the
    // installation directory rather than directly from within the cache directory.
    // This is not necessary, however, if the application depends on other installed
    // files, this ensures they will be present and in the expected location.
    run_cmd.step.dependOn(b.getInstallStep());

    // This allows the user to pass arguments to the application in the build
    // command itself, like this: `zig build run -- arg1 arg2 etc`
    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    // This creates a build step. It will be visible in the `zig build --help` menu,
    // and can be selected like this: `zig build run`
    // This will evaluate the `run` step rather than the default, which is "install".
    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);

    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);

    const exe_unit_tests = b.addTest(.{
        .root_source_file = .{ .path = "src/main.zig" },
        .target = target,
        .optimize = optimize,
    });

    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);

    // Similar to creating the run step earlier, this exposes a `test` step to
    // the `zig build --help` menu, providing a way for the user to request
    // running the unit tests.
    const test_step = b.step("test", "Run unit tests");
    test_step.dependOn(&run_lib_unit_tests.step);
    test_step.dependOn(&run_exe_unit_tests.step);
}

const asset_extensions = [_][]const u8{
    "obj",
    "glsl",
    "prog",
    "png",
    "jpg",
    "exr",
};

// Find all assets and cook them using assetc
fn buildAssets(b: *std.Build, install_assetc_step: *Step, step: *Step, assetc: *Step.Compile, path: []const u8) !Build.LazyPath {
    const assetsPath = b.pathFromRoot(path);
    defer b.allocator.free(assetsPath);
    var assetsDir = try std.fs.openDirAbsolute(assetsPath, .{ .iterate = true });
    defer assetsDir.close();

    const gen_asset_manifest = GenerateAssetManifest.create(b);
    const asset_manifest_file = gen_asset_manifest.getAssetManifest();

    var walker = try assetsDir.walk(b.allocator);
    defer walker.deinit();

    while (try walker.next()) |entry| {
        const ext_with_dot = std.fs.path.extension(entry.basename);
        if (ext_with_dot.len == 0) continue;

        const ext = ext_with_dot[1..];

        var is_known_ext = false;
        for (asset_extensions) |known_ext| {
            if (std.mem.eql(u8, known_ext, ext)) {
                is_known_ext = true;
                break;
            }
        }
        if (!is_known_ext) continue;

        const run_assetc = b.addRunArtifact(assetc);
        gen_asset_manifest.addAssetListFile(run_assetc.captureStdOut());
        run_assetc.step.dependOn(install_assetc_step);

        run_assetc.addPathDir(b.pathFromRoot("libs/ispc_texcomp/lib"));

        // First argument, input path relative to base assets dir
        run_assetc.addArg(b.dupe(entry.path));
        // Absolute input file arg, this will add it to step deps, cache and all that good stuff
        run_assetc.addFileArg(.{ .path = b.pathJoin(&.{ path, entry.path }) });

        // Generated output dir. Output asset(s) will be placed there at the same relative path as input
        const result_dir = run_assetc.addOutputFileArg("assets");

        const install_assets = b.addInstallDirectory(.{
            .source_dir = result_dir,
            .install_dir = .prefix,
            .install_subdir = path,
        });
        step.dependOn(&install_assets.step);
    }

    return asset_manifest_file;
}

fn buildAssetCompiler(b: *Build, optimize: std.builtin.OptimizeMode) *Step.Compile {
    const assimp_dep = b.dependency("zig-assimp", .{
        .target = b.host,
        .optimize = optimize,
        //.formats = @as([]const u8, "3DS,3MF,AC,AMF,ASE,Assbin,Assjson,Assxml,B3D,Blender,BVH,C4D,COB,Collada,CSM,DXF,FBX,glTF,glTF2,HMP,IFC,Irr,LWO,LWS,M3D,MD2,MD3,MD5,MDC,MDL,MMD,MS3D,NDO,NFF,Obj,OFF,Ogre,OpenGEX,Ply,Q3BSP,Q3D,Raw,SIB,SMD,Step,STEPParser,STL,Terragen,Unreal,X,X3D,XGL"),
        .formats = @as([]const u8, "Obj"),
    });

    const assimp_lib = assimp_dep.artifact("assimp");

    const assetc = b.addExecutable(.{
        .name = "assetc",
        .target = b.host,
        .root_source_file = .{ .path = "tools/asset_compiler.zig" },
        .optimize = optimize,
    });
    assetc.linkLibC();

    b.installFile("libs/ispc_texcomp/lib/ispc_texcomp.dll", "ispc_texcomp.dll");
    b.installFile("libs/ispc_texcomp/lib/ispc_texcomp.pdb", "ispc_texcomp.pdb");
    assetc.addLibraryPath(.{ .path = "libs/ispc_texcomp/lib" });
    assetc.addIncludePath(.{ .path = "libs/ispc_texcomp/include" });
    assetc.linkSystemLibrary("ispc_texcomp");

    assetc.root_module.addAnonymousImport("formats", .{ .root_source_file = .{ .path = "src/formats.zig" } });

    assetc.linkLibrary(assimp_lib);
    assetc.linkLibC();
    assetc.linkLibCpp();

    assetc.addCSourceFile(.{ .file = .{ .path = "libs/stb/stb_image.c" }, .flags = &.{"-std=c99"} });
    assetc.addIncludePath(.{ .path = "libs/stb" });

    return assetc;
}