const std = @import("std");
const Build = std.Build;

const basisu_root = sdkPath("/upstream/basisu");

var _module: ?*std.build.Module = null;

pub fn module(b: *std.Build) *std.build.Module {
    if (_module) |m| return m;
    _module = b.createModule(.{
        .source = .{
            .path = "src/main.zig",
        },
    });
    return _module.?;
}

pub const Options = struct {
    encoder: ?EncoderOptions,
    transcoder: ?TranscoderOptions,
};

pub const EncoderOptions = struct {
    install_libs: bool = false,
};

pub const TranscoderOptions = struct {
    install_libs: bool = false,
};

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

    const test_step = b.step("test", "Run library tests");
    test_step.dependOn(&testStep(b, optimize, target).step);
}

pub fn testStep(b: *Build, optimize: std.builtin.OptimizeMode, target: std.zig.CrossTarget) *std.build.RunStep {
    const main_tests = b.addTest(.{
        .name = "basisu-tests",
        .root_source_file = .{ .path = sdkPath("/src/main.zig") },
        .target = target,
        .optimize = optimize,
    });
    main_tests.main_pkg_path = sdkPath("/");
    link(b, main_tests, target, optimize, .{
        .encoder = .{},
        .transcoder = .{},
    });
    main_tests.install();
    return main_tests.run();
}

pub fn link(b: *Build, step: *std.build.CompileStep, target: std.zig.CrossTarget, optimize: std.builtin.OptimizeMode, options: Options) void {
    if (options.encoder) |encoder_options| {
        step.linkLibrary(buildEncoder(b, target, optimize, encoder_options));
        step.addCSourceFile(sdkPath("/src/encoder/wrapper.cpp"), &.{});
        step.addIncludePath(basisu_root ++ "/encoder");
    }
    if (options.transcoder) |transcoder_options| {
        step.linkLibrary(buildTranscoder(b, target, optimize, transcoder_options));
        step.addCSourceFile(sdkPath("/src/transcoder/wrapper.cpp"), &.{});
        step.addIncludePath(basisu_root ++ "/transcoder");
    }
}

pub fn buildEncoder(b: *Build, target: std.zig.CrossTarget, optimize: std.builtin.OptimizeMode, options: EncoderOptions) *std.build.CompileStep {
    // TODO(build-system): https://github.com/hexops/mach/issues/229#issuecomment-1100958939
    ensureDependencySubmodule(b.allocator, "upstream") catch unreachable;

    const encoder = b.addStaticLibrary(.{
        .name = "basisu-encoder",
        .target = target,
        .optimize = optimize,
    });
    encoder.linkLibCpp();
    encoder.addCSourceFiles(
        encoder_sources,
        &.{},
    );
    encoder.defineCMacro("BASISU_FORCE_DEVEL_MESSAGES", "0");
    encoder.defineCMacro("BASISD_SUPPORT_KTX2_ZSTD", "0");

    if (options.install_libs)
        encoder.install();
    return encoder;
}

pub fn buildTranscoder(b: *Build, target: std.zig.CrossTarget, optimize: std.builtin.OptimizeMode, options: TranscoderOptions) *std.build.CompileStep {
    // TODO(build-system): https://github.com/hexops/mach/issues/229#issuecomment-1100958939
    ensureDependencySubmodule(b.allocator, "upstream") catch unreachable;

    const transcoder = b.addStaticLibrary(.{
        .name = "basisu-transcoder",
        .target = target,
        .optimize = optimize,
    });
    transcoder.linkLibCpp();
    transcoder.addCSourceFiles(transcoder_sources, &.{
        "-Wno-deprecated-builtins",
        "-Wno-deprecated-declarations",
        "-Wno-array-bounds",
    });
    transcoder.defineCMacro("BASISU_FORCE_DEVEL_MESSAGES", "0");
    transcoder.defineCMacro("BASISD_SUPPORT_KTX2_ZSTD", "0");

    if (options.install_libs)
        transcoder.install();
    return transcoder;
}

fn ensureDependencySubmodule(allocator: std.mem.Allocator, path: []const u8) !void {
    if (std.process.getEnvVarOwned(allocator, "NO_ENSURE_SUBMODULES")) |no_ensure_submodules| {
        defer allocator.free(no_ensure_submodules);
        if (std.mem.eql(u8, no_ensure_submodules, "true")) return;
    } else |_| {}
    var child = std.ChildProcess.init(&.{ "git", "submodule", "update", "--init", path }, allocator);
    child.cwd = sdkPath("/");
    child.stderr = std.io.getStdErr();
    child.stdout = std.io.getStdOut();

    _ = try child.spawnAndWait();
}

fn sdkPath(comptime suffix: []const u8) []const u8 {
    if (suffix[0] != '/') @compileError("suffix must be an absolute path");
    return comptime blk: {
        const root_dir = std.fs.path.dirname(@src().file) orelse ".";
        break :blk root_dir ++ suffix;
    };
}

const transcoder_sources = &[_][]const u8{
    basisu_root ++ "/transcoder/basisu_transcoder.cpp",
};

const encoder_sources = &[_][]const u8{
    basisu_root ++ "/encoder/basisu_backend.cpp",
    basisu_root ++ "/encoder/basisu_basis_file.cpp",
    basisu_root ++ "/encoder/basisu_bc7enc.cpp",
    basisu_root ++ "/encoder/basisu_comp.cpp",
    basisu_root ++ "/encoder/basisu_enc.cpp",
    basisu_root ++ "/encoder/basisu_etc.cpp",
    basisu_root ++ "/encoder/basisu_frontend.cpp",
    basisu_root ++ "/encoder/basisu_gpu_texture.cpp",
    basisu_root ++ "/encoder/basisu_kernels_sse.cpp",
    basisu_root ++ "/encoder/basisu_opencl.cpp",
    basisu_root ++ "/encoder/basisu_pvrtc1_4.cpp",
    basisu_root ++ "/encoder/basisu_resample_filters.cpp",
    basisu_root ++ "/encoder/basisu_resampler.cpp",
    basisu_root ++ "/encoder/basisu_ssim.cpp",
    basisu_root ++ "/encoder/basisu_uastc_enc.cpp",
    basisu_root ++ "/encoder/jpgd.cpp",
    basisu_root ++ "/encoder/pvpngreader.cpp",
};