const std = @import("std");

pub const Backend = enum {
    no_backend,
    glfw_wgpu,
    win32_dx12,
    glfw_opengl3,
    sdl2_opengl3,
};

pub const Options = struct {
    backend: Backend,
    shared: bool = false,
};

pub const Package = struct {
    options: Options,
    zgui: *std.Build.Module,
    zgui_options: *std.Build.Module,
    zgui_c_cpp: *std.Build.CompileStep,

    pub fn link(pkg: Package, exe: *std.Build.CompileStep) void {
        exe.linkLibrary(pkg.zgui_c_cpp);
        exe.addModule("zgui", pkg.zgui);
    }
};

pub fn package(
    b: *std.Build,
    target: std.zig.CrossTarget,
    optimize: std.builtin.Mode,
    args: struct {
        options: Options,
    },
) Package {
    const step = b.addOptions();
    step.addOption(Backend, "backend", args.options.backend);
    step.addOption(bool, "shared", args.options.shared);

    const zgui_options = step.createModule();

    const zgui = b.createModule(.{
        .source_file = .{ .path = thisDir() ++ "/src/main.zig" },
        .dependencies = &.{
            .{ .name = "zgui_options", .module = zgui_options },
        },
    });

    const zgui_c_cpp = if (args.options.shared) blk: {
        const lib = b.addSharedLibrary(.{
            .name = "zgui",
            .target = target,
            .optimize = optimize,
        });

        lib.install();
        if (target.isWindows()) {
            lib.defineCMacro("IMGUI_API", "__declspec(dllexport)");
            lib.defineCMacro("IMPLOT_API", "__declspec(dllexport)");
            lib.defineCMacro("ZGUI_API", "__declspec(dllexport)");
        }

        break :blk lib;
    } else b.addStaticLibrary(.{
        .name = "zgui",
        .target = target,
        .optimize = optimize,
    });

    zgui_c_cpp.addIncludePath(thisDir() ++ "/libs");
    zgui_c_cpp.addIncludePath(thisDir() ++ "/libs/imgui");

    zgui_c_cpp.linkLibC();
    zgui_c_cpp.linkLibCpp();

    const cflags = &.{"-fno-sanitize=undefined"};

    zgui_c_cpp.addCSourceFile(thisDir() ++ "/src/zgui.cpp", cflags);

    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/imgui.cpp", cflags);
    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/imgui_widgets.cpp", cflags);
    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/imgui_tables.cpp", cflags);
    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/imgui_draw.cpp", cflags);
    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/imgui_demo.cpp", cflags);

    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/implot_demo.cpp", cflags);
    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/implot.cpp", cflags);
    zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/implot_items.cpp", cflags);

    switch (args.options.backend) {
        .glfw_wgpu => {
            zgui_c_cpp.addIncludePath(thisDir() ++ "/../zglfw/libs/glfw/include");
            zgui_c_cpp.addIncludePath(thisDir() ++ "/../zgpu/libs/dawn/include");
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_glfw.cpp", cflags);
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_wgpu.cpp", cflags);
        },
        .glfw_opengl3 => {
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_glfw.cpp", cflags);
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_opengl3.cpp", cflags);
        },
        .win32_dx12 => {
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_win32.cpp", cflags);
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_dx12.cpp", cflags);
            zgui_c_cpp.linkSystemLibraryName("d3dcompiler_47");
            zgui_c_cpp.linkSystemLibraryName("dwmapi");
        },
        .sdl2_opengl3 => {
            if (target.isWindows()) blk: {
                // see: https://github.com/MasterQ32/SDL.zig/blob/37f4ba9e31bea895fa19ef8b90d1f51111e52e67/Sdk.zig#L182-L199

                zgui_c_cpp.addVcpkgPaths(if (args.options.shared) .dynamic else .static);
                const path = zgui_c_cpp.vcpkg_bin_path orelse break :blk;

                const src_path = std.fs.path.join(b.allocator, &.{ path, "SDL2.dll" }) catch @panic("out of memory");

                std.fs.cwd().access(src_path, .{}) catch break :blk;

                // we found SDL2.dll
                zgui_c_cpp.linkSystemLibrary("SDL2");
                b.installBinFile(src_path, "SDL2.dll");
            } else zgui_c_cpp.linkSystemLibrary("SDL2");

            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_sdl.cpp", cflags);
            zgui_c_cpp.addCSourceFile(thisDir() ++ "/libs/imgui/backends/imgui_impl_opengl3.cpp", cflags);
        },
        .no_backend => {},
    }

    return .{
        .options = args.options,
        .zgui = zgui,
        .zgui_options = zgui_options,
        .zgui_c_cpp = zgui_c_cpp,
    };
}

pub fn build(_: *std.Build) void {}

inline fn thisDir() []const u8 {
    return comptime std.fs.path.dirname(@src().file) orelse ".";
}