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

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

    const assets_dir = "assets";
    const asset_files = [_][]const u8{
        "sokoban/sokoban_tilesheet.png",
        "roboto-font/Roboto-Regular.ttf",
        "tiled/map.tmx",
        "tiled/tileset.tsx"
    };

    const asset_dir_realpath = try b.build_root.join(b.graph.arena, &.{ assets_dir });

    const is_wasm = target.result.cpu.arch.isWasm();
    const is_debug = (optimize == .Debug);

    const has_imgui = b.option(bool, "imgui", "ImGui integration") orelse is_debug;
    const assets_from_filesystem = b.option(bool, "assets-filesystem", "Allow reading assets from filesystem") orelse is_debug;

    var has_tracy = false;
    if (!is_wasm) {
        has_tracy = b.option(bool, "tracy", "Tracy integration") orelse is_debug;
    }

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

    const build_options = b.addOptions();
    build_options.addOption(bool, "has_imgui", has_imgui);
    build_options.addOption(?[]const u8, "assets_dir", if (assets_from_filesystem) asset_dir_realpath else null);
    exe_mod.addOptions("build_options", build_options);

    exe_mod.addImport("embedded_assets", try createEmbeddedAssets(b, assets_dir, &asset_files));

    const math_mod = b.createModule(.{
        .root_source_file = b.path("src/math.zig")
    });
    exe_mod.addImport("math", math_mod);

    const dep_tiled = b.dependency("tiled", .{});
    exe_mod.addImport("tiled", dep_tiled.module("tiled"));

    const dep_sokol = b.dependency("sokol", .{
        .target = target,
        .optimize = optimize,
        .with_sokol_imgui = has_imgui
    });
    const mod_sokol = dep_sokol.module("sokol");
    exe_mod.linkLibrary(dep_sokol.artifact("sokol_clib"));
    exe_mod.addImport("sokol", mod_sokol);

    const dep_shdc = dep_sokol.builder.dependency("shdc", .{});

    var slang = sokol.shdc.Slang{};
    if (is_wasm) {
        slang.wgsl = true;
    } else {
        slang.glsl410 = true;
        slang.hlsl4 = true;
        slang.metal_macos = true;
        slang.glsl300es = true;
    }
    const mod_shader = try sokol.shdc.createModule(b, "shader", mod_sokol, .{
        .shdc_dep = dep_shdc,
        .input = "src/shader.glsl",
        .output = "src/shader.zig",
        .slang = slang
    });
    mod_shader.addImport("math", math_mod);
    exe_mod.addImport("shader", mod_shader);

    if (has_imgui) {
        if (b.lazyDependency("cimgui", .{
            .target = target,
            .optimize = optimize,
        })) |dep_cimgui| {
            const cimgui = b.lazyImport(@This(), "cimgui").?;
            const cimgui_conf = cimgui.getConfig(true);
            exe_mod.addImport("cimgui", dep_cimgui.module(cimgui_conf.module_name));
            dep_sokol.artifact("sokol_clib").root_module.addIncludePath(dep_cimgui.path(cimgui_conf.include_dir));
        }
    }

    const dep_stb = b.dependency("stb", .{});
    exe_mod.addImport("stb_image", dep_stb.module("stb_image"));
    exe_mod.addImport("stb_vorbis", dep_stb.module("stb_vorbis"));
    exe_mod.addImport("stb_rect_pack", dep_stb.module("stb_rect_pack"));
    exe_mod.addImport("stb_truetype", dep_stb.module("stb_truetype"));

    const dep_tracy = b.dependency("tracy", .{
        .target = target,
        .optimize = optimize,
        .tracy_enable = has_tracy,
        .tracy_only_localhost = true
    });
    if (has_tracy) {
        exe_mod.linkLibrary(dep_tracy.artifact("tracy"));
    }
    exe_mod.addImport("tracy", dep_tracy.module("tracy"));

    var run_cmd_step: *std.Build.Step = undefined;
    if (is_wasm) {
        if (true) {
            @panic("TODO: test in 0.17");
        }

        const build_step = buildWasm(b, .{
            .name = "index",
            .root_module = exe_mod,
            .dep_sokol = dep_sokol,
        });
        b.getInstallStep().dependOn(build_step);

        const dep_emsdk = dep_sokol.builder.dependency("emsdk", .{});
        const emrun_step = sokol.emRunStep(b, .{ .name = "index", .emsdk = dep_emsdk });
        emrun_step.step.dependOn(build_step);
        run_cmd_step = &emrun_step.step;

        // TODO: Create a zip archive of all of the files. Would be useful for easier itch.io upload
    } else {
        const exe = buildNative(b, .{
            .name = "sokol_template_v2",
            .root_module = exe_mod
        });
        b.installArtifact(exe);

        {
            const run_cmd = b.addRunArtifact(exe);
            if (b.args) |args| {
                run_cmd.addArgs(args);
            }
            run_cmd_step = &run_cmd.step;
        }

        {
            const exe_tests = b.addTest(.{ .root_module = exe_mod, });
            const run_exe_tests = b.addRunArtifact(exe_tests);

            const test_step = b.step("test", "Run tests");
            test_step.dependOn(&run_exe_tests.step);
        }
    }

    const run_step = b.step("run", "Run game");
    run_step.dependOn(run_cmd_step);
}

fn createEmbeddedAssets(
    b: *std.Build,
    assets_dir: []const u8,
    asset_files: []const []const u8
) !*std.Build.Module {
    const write_files = b.addWriteFiles();

    var embedded_assets: std.ArrayList(u8) = .empty;
    defer embedded_assets.deinit(b.allocator);

    try embedded_assets.appendSlice(b.allocator, "pub const files = .{\n");
    const mod_embedded_assets = b.createModule(.{});
    for (asset_files) |asset_file| {
        mod_embedded_assets.addAnonymousImport(asset_file, .{
            .root_source_file = b.path(b.pathJoin(&.{ assets_dir, asset_file }))
        });

        try embedded_assets.appendSlice(b.allocator, "    .{ ");

        try embedded_assets.appendSlice(b.allocator, ".name = \"");
        try embedded_assets.appendSlice(b.allocator, asset_file);
        try embedded_assets.appendSlice(b.allocator, "\"");

        try embedded_assets.appendSlice(b.allocator, ", ");

        try embedded_assets.appendSlice(b.allocator, ".contents = @embedFile(\"");
        try embedded_assets.appendSlice(b.allocator, asset_file);
        try embedded_assets.appendSlice(b.allocator, "\")");

        try embedded_assets.appendSlice(b.allocator, " },\n");
    }
    try embedded_assets.appendSlice(b.allocator, "};\n");
    mod_embedded_assets.root_source_file = write_files.add("embedded_assets.zig", embedded_assets.items);

    return mod_embedded_assets;
}

const BuildNativeOptions = struct {
    name: []const u8,
    root_module: *std.Build.Module,
    win32_has_console: ?bool = null,
    win32_png_icon: ?std.Build.LazyPath = null
};

fn buildNative(
    b: *std.Build,
    opts: BuildNativeOptions,
) *std.Build.Step.Compile {
    const exe = b.addExecutable(.{
        .name = opts.name,
        .root_module = opts.root_module,
    });

    const target = opts.root_module.resolved_target.?;
    if (target.result.os.tag == .windows) {
        const optimize = opts.root_module.optimize.?;
        const has_console = opts.win32_has_console orelse (optimize == .Debug);
        exe.subsystem = if (has_console) .Console else .Windows;

        if (opts.win32_png_icon) |win32_png_icon| {
            const png_to_icon_tool = buildPngToIconTool(b, b.graph.host, .ReleaseSafe);

            const png_to_icon_step = b.addRunArtifact(png_to_icon_tool);
            png_to_icon_step.addFileArg(win32_png_icon);
            const icon_file = png_to_icon_step.addOutputFileArg("icon.ico");

            const add_icon_step = AddExecutableIcon.init(exe, icon_file);
            exe.step.dependOn(&add_icon_step.step);
        }
    }

    return exe;
}

fn buildPngToIconTool(
    b: *std.Build,
    target: std.Build.ResolvedTarget,
    optimize: std.builtin.OptimizeMode,
) *std.Build.Step.Compile {
    const mod = b.createModule(.{
        .target = target,
        .optimize = optimize,
        .root_source_file = b.path("tools/png-to-icon.zig"),
    });

    const dep_stb = b.dependency("stb", .{});
    mod.addImport("stb_image", dep_stb.module("stb_image"));

    return b.addExecutable(.{
        .name = "png-to-icon",
        .root_module = mod,
    });
}

const AddExecutableIcon = struct {
    obj: *std.Build.Step.Compile,
    step: std.Build.Step,
    icon_file: std.Build.LazyPath,
    resource_file: std.Build.LazyPath,

    fn init(obj: *std.Build.Step.Compile, icon_file: std.Build.LazyPath) *AddExecutableIcon {
        const b = obj.step.owner;
        const self = b.allocator.create(AddExecutableIcon) catch @panic("OOM");

        self.obj = obj;
        self.step = std.Build.Step.init(.{
            .id = .custom,
            .name = "add executable icon",
            .owner = b,
            .makeFn = make
        });

        self.icon_file = icon_file;
        icon_file.addStepDependencies(&self.step);

        const write_files = b.addWriteFiles();
        self.resource_file = write_files.add("resource-file.rc", "");
        self.step.dependOn(&write_files.step);

        self.obj.root_module.addWin32ResourceFile(.{
            .file = self.resource_file,
        });

        return self;
    }

    fn make(step: *std.Build.Step, _: std.Build.Step.MakeOptions) !void {
        const b = step.owner;
        const self: *AddExecutableIcon = @fieldParentPtr("step", step);

        const relative_icon_path = try std.fs.path.relative(
            b.allocator,
            "",
            null,
            self.resource_file.dirname().getPath(b),
            self.icon_file.getPath(b)
        );
        std.mem.replaceScalar(u8, relative_icon_path, '\\', '/');

        {
            const cwd = std.Io.Dir.cwd();
            const resource_file = try cwd.createFile(b.graph.io, self.resource_file.getPath(b), .{ });
            defer resource_file.close(b.graph.io);

            var buff: [4*4096]u8 = undefined;
            var file_writer = resource_file.writer(b.graph.io, &buff);
            const w = &file_writer.interface;

            try w.writeAll("IDI_ICON ICON \"");
            try w.writeAll(relative_icon_path);
            try w.writeAll("\"");
        }
    }
};

const BuildWasmOptions = struct {
    name: []const u8,
    root_module: *std.Build.Module,
    dep_sokol: *std.Build.Dependency,
};

fn buildWasm(b: *std.Build, opts: BuildWasmOptions) *std.Build.Step {
    opts.root_module.sanitize_c = .off;

    // build the main file into a library, this is because the WASM 'exe'
    // needs to be linked in a separate build step with the Emscripten linker
    const main_lib = b.addLibrary(.{
        .name = opts.name,
        .root_module = opts.root_module,
    });

    const dep_sokol = opts.dep_sokol;
    const dep_emsdk = dep_sokol.builder.dependency("emsdk", .{});

    // TODO:
    // const emsdk_install_step = sokol.emSdkInstallStep(b, dep_emsdk, .{});
    // main_lib.step.dependOn(emsdk_install_step);

    patchWasmIncludeDirs(
        opts.root_module,
        dep_emsdk.path("upstream/emscripten/cache/sysroot/include"),
        &(dep_sokol.artifact("sokol_clib").step)
    );

    const link_step = sokol.emLinkStep(b, .{
        .lib_main = main_lib,
        .target = opts.root_module.resolved_target.?,
        .optimize = opts.root_module.optimize.?,
        .emsdk = dep_emsdk,
        .use_webgl2 = true,
        .use_emmalloc = true,
        .use_filesystem = false,
        .shell_file_path = b.path("src/engine/shell.html"),
    }) catch unreachable;

    return &link_step.step;
}

fn patchWasmIncludeDirs(
    module: *std.Build.Module,
    path: std.Build.LazyPath,
    depend_step: *std.Build.Step
) void {
    if (module.link_libc != null and module.link_libc.?) {
        // need to inject the Emscripten system header include path into
        // the cimgui C library otherwise the C/C++ code won't find
        // C stdlib headers
        module.addSystemIncludePath(path);
    }

    for (module.import_table.values()) |imported_module| {
        patchWasmIncludeDirs(imported_module, path, depend_step);
    }

    for (module.link_objects.items) |link_object| {
        if (link_object != .other_step) {
            continue;
        }
        const lib = link_object.other_step;
        if (&lib.step == depend_step) {
            continue;
        }

        if (lib.root_module.link_libc != null and lib.root_module.link_libc.?) {
            // need to inject the Emscripten system header include path into
            // the cimgui C library otherwise the C/C++ code won't find
            // C stdlib headers
            lib.root_module.addSystemIncludePath(path);

            // all C libraries need to depend on the sokol library, when building for
            // WASM this makes sure that the Emscripten SDK has been setup before
            // C compilation is attempted (since the sokol C library depends on the
            // Emscripten SDK setup step)
            lib.step.dependOn(depend_step);
        }
        patchWasmIncludeDirs(lib.root_module, path, depend_step);
    }
}