const std = @import("std");

fn resolveHeaderRoot(allocator: std.mem.Allocator, source_dir: []const u8) ![]const u8 {
    const include_sdl3 = try std.fs.path.join(allocator, &.{ source_dir, "include", "SDL3" });
    defer allocator.free(include_sdl3);
    if (std.fs.cwd().access(include_sdl3, .{})) {
        return try allocator.dupe(u8, "include/SDL3");
    } else |_| {}

    const sdl3_dir = try std.fs.path.join(allocator, &.{ source_dir, "SDL3" });
    defer allocator.free(sdl3_dir);
    if (std.fs.cwd().access(sdl3_dir, .{})) {
        return try allocator.dupe(u8, "SDL3");
    } else |_| {}

    return try allocator.dupe(u8, ".");
}

fn addFetchSdlStep(b: *std.Build) *std.Build.Step {
    const default_sdl_url = "git@github.com:castholm/SDL.git";
    const official_sdl_url = "git@github.com:libsdl-org/SDL.git";
    const sdl_url_option = b.option([]const u8, "sdl-url", "URL to fetch SDL3 from (use 'official' for libsdl-org/SDL)") orelse default_sdl_url;

    const sdl_url = if (std.mem.eql(u8, sdl_url_option, "official") or
        b.option(bool, "official", "use the official sdl path of git@github.com:libsdl-org/SDL.git (same as setting -Dsdl-url=official)") != null)
        official_sdl_url
    else
        sdl_url_option;

    const clean_sdl = b.option(bool, "clean", "Delete sdl3/ directory before fetching") orelse false;

    const sdl_checkout = b.option([]const u8, "ref", "the git ref to check out after fetching sdl, this can be tag, commit, branch...");

    const fetch_step = b.step("fetch-sdl", "Fetch SDL3 source from git");

    const sdl_exists = if (std.fs.cwd().access("sdl3", .{})) true else |_| false;

    var end_step: *std.Build.Step = undefined;
    if (clean_sdl) {
        const remove_dir = b.addRemoveDirTree(b.path("sdl3"));
        const fetch_sdl = b.addSystemCommand(&.{ "git", "clone", sdl_url, "sdl3" });
        fetch_sdl.step.dependOn(&remove_dir.step);
        end_step = &fetch_sdl.step;
        // fetch_step.dependOn(&fetch_sdl.step);
    } else if (sdl_exists) {
        const echo_msg = b.addSystemCommand(&.{ "echo", "sdl already fetched" });
        end_step = &echo_msg.step;
        // fetch_step.dependOn(&echo_msg.step);
    } else {
        const fetch_sdl = b.addSystemCommand(&.{ "git", "clone", sdl_url, "sdl3" });
        end_step = &fetch_sdl.step;
    }

    const checkout_step = if (sdl_checkout) |ref| &b.addSystemCommand(&.{ "git", "-C", "sdl3", "checkout", ref }).step else end_step;

    if (sdl_checkout != null) {
        checkout_step.dependOn(end_step);
    }

    fetch_step.dependOn(checkout_step);
    return fetch_step;
}

const ArchiveStep = struct {
    step: std.Build.Step,
    base_dir: ?[]const u8,

    pub fn create(b: *std.Build, base_dir: ?[]const u8) *std.Build.Step {
        const self = b.allocator.create(ArchiveStep) catch @panic("OOM");
        self.* = .{
            .step = std.Build.Step.init(.{
                .id = .custom,
                .name = "archive generate outputs",
                .owner = b,
                .makeFn = make,
            }),
            .base_dir = base_dir,
        };
        return &self.step;
    }

    fn make(step: *std.Build.Step, options: std.Build.Step.MakeOptions) !void {
        _ = options;

        const self: *ArchiveStep = @fieldParentPtr("step", step);

        const cwd = std.fs.cwd();
        const json_path = if (self.base_dir) |base_dir|
            try std.fs.path.join(step.owner.allocator, &.{ base_dir, "json" })
        else
            try step.owner.allocator.dupe(u8, "json");
        defer step.owner.allocator.free(json_path);

        const api_path = if (self.base_dir) |base_dir|
            try std.fs.path.join(step.owner.allocator, &.{ base_dir, "api" })
        else
            try step.owner.allocator.dupe(u8, "api");
        defer step.owner.allocator.free(api_path);

        const archive_root = if (self.base_dir) |base_dir|
            try std.fs.path.join(step.owner.allocator, &.{ base_dir, "archive", "generate" })
        else
            try step.owner.allocator.dupe(u8, "archive/generate");
        defer step.owner.allocator.free(archive_root);

        const json_exists = if (cwd.access(json_path, .{})) true else |_| false;
        const api_exists = if (cwd.access(api_path, .{})) true else |_| false;

        if (!json_exists and !api_exists) return;

        const timestamp = std.time.timestamp();
        const timestamp_dir = try std.fmt.allocPrint(step.owner.allocator, "{d}", .{timestamp});
        defer step.owner.allocator.free(timestamp_dir);
        const archive_path = try std.fs.path.join(step.owner.allocator, &.{ archive_root, timestamp_dir });
        defer step.owner.allocator.free(archive_path);

        try cwd.makePath(archive_path);

        if (json_exists) {
            const json_dest = try std.fs.path.join(step.owner.allocator, &.{ archive_path, "json" });
            defer step.owner.allocator.free(json_dest);
            try cwd.rename(json_path, json_dest);
        }

        if (api_exists) {
            const api_dest = try std.fs.path.join(step.owner.allocator, &.{ archive_path, "api" });
            defer step.owner.allocator.free(api_dest);
            try cwd.rename(api_path, api_dest);
        }
    }
};

const MakeDirStep = struct {
    step: std.Build.Step,
    dir_path: []const u8,

    pub fn create(b: *std.Build, dir_path: []const u8) *std.Build.Step {
        const self = b.allocator.create(MakeDirStep) catch @panic("OOM");
        self.* = .{
            .step = std.Build.Step.init(.{
                .id = .custom,
                .name = b.fmt("mkdir {s}", .{dir_path}),
                .owner = b,
                .makeFn = make,
            }),
            .dir_path = dir_path,
        };
        return &self.step;
    }

    fn make(step: *std.Build.Step, options: std.Build.Step.MakeOptions) !void {
        _ = options;
        const self: *MakeDirStep = @fieldParentPtr("step", step);
        try std.fs.cwd().makePath(self.dir_path);
    }
};

pub fn generateApi(b: *std.Build, parser_exe: *std.Build.Step.Compile, fetch_sdl_step: *std.Build.Step) void {
    const source_dir = b.option([]const u8, "sourceDir", "Parse SDL headers from an existing local directory instead of fetching git");
    const output_dir = b.option([]const u8, "outputDir", "Directory where generated api/ and json/ folders should be written");
    const basedir = b.option([]const u8, "basedir", "Working directory for the parser to execute in");
    const effective_output_dir = output_dir orelse source_dir;
    const header_root_suffix = if (source_dir) |dir| resolveHeaderRoot(b.allocator, dir) catch @panic("OOM") else null;

    // Archive existing json/ and api/ directories before regenerating
    const archive_step = ArchiveStep.create(b, effective_output_dir);

    const generation_root = if (source_dir != null) archive_step else fetch_sdl_step;
    if (source_dir == null) {
        fetch_sdl_step.dependOn(archive_step);
    }

    // Write a build marker file after the source selection step to enable caching
    const timestamp = std.time.timestamp();
    const wf = b.addWriteFiles();
    const marker_file = wf.add(".buildmarker", b.fmt("{d}", .{timestamp}));
    _ = marker_file;
    wf.step.dependOn(generation_root);

    var path_prep_step: *std.Build.Step = &wf.step;
    if (effective_output_dir) |dir| {
        const output_dir_step = MakeDirStep.create(b, dir);
        output_dir_step.dependOn(path_prep_step);
        path_prep_step = output_dir_step;
    }
    if (basedir) |dir| {
        const basedir_step = MakeDirStep.create(b, dir);
        basedir_step.dependOn(path_prep_step);
        path_prep_step = basedir_step;
    }

    // All public SDL3 API headers (53 total)
    // Skipped: assert, thread, hidapi, mutex, tray (not core APIs or problematic)
    const headers_to_generate = [_]struct { header: []const u8, output: []const u8 }{
        // .{ .header = "SDL_asyncio.h", .output = "asyncio" },
        // .{ .header = "SDL_atomic.h", .output = "atomic" },
        .{ .header = "SDL_audio.h", .output = "audio" },
        .{ .header = "SDL_blendmode.h", .output = "blendmode" },
        .{ .header = "SDL_camera.h", .output = "camera" },
        .{ .header = "SDL_clipboard.h", .output = "clipboard" },
        // .{ .header = "SDL_cpuinfo.h", .output = "cpuinfo" },
        .{ .header = "SDL_dialog.h", .output = "dialog" },
        .{ .header = "SDL_endian.h", .output = "endian" },
        .{ .header = "SDL_error.h", .output = "error" },
        .{ .header = "SDL_events.h", .output = "events" },
        .{ .header = "SDL_filesystem.h", .output = "filesystem" },
        .{ .header = "SDL_gamepad.h", .output = "gamepad" },
        .{ .header = "SDL_gpu.h", .output = "gpu" },
        // .{ .header = "SDL_guid.h", .output = "guid" },
        .{ .header = "SDL_haptic.h", .output = "haptic" },
        // .{ .header = "SDL_hidapi.h", .output = "hidapi" }, // Skipped: not core API
        .{ .header = "SDL_hints.h", .output = "hints" },
        .{ .header = "SDL_init.h", .output = "init" },
        // .{ .header = "SDL_iostream.h", .output = "iostream" }, // Skipped: complex I/O API
        .{ .header = "SDL_joystick.h", .output = "joystick" },
        // .{ .header = "SDL_keyboard.h", .output = "keyboard" },
        .{ .header = "SDL_keycode.h", .output = "keycode" },
        .{ .header = "SDL_loadso.h", .output = "loadso" },
        // .{ .header = "SDL_locale.h", .output = "locale" },
        // .{ .header = "SDL_log.h", .output = "log" },
        .{ .header = "SDL_messagebox.h", .output = "messagebox" },
        // .{ .header = "SDL_metal.h", .output = "metal" },
        .{ .header = "SDL_misc.h", .output = "misc" },
        .{ .header = "SDL_mouse.h", .output = "mouse" },
        // .{ .header = "SDL_mutex.h", .output = "mutex" }, // Skipped: not core API
        // .{ .header = "SDL_opengl.h", .output = "opengl" },
        // .{ .header = "SDL_pen.h", .output = "pen" },
        .{ .header = "SDL_pixels.h", .output = "pixels" },
        // .{ .header = "SDL_power.h", .output = "power" },
        // .{ .header = "SDL_process.h", .output = "process" },
        .{ .header = "SDL_properties.h", .output = "properties" },
        .{ .header = "SDL_rect.h", .output = "rect" },
        .{ .header = "SDL_render.h", .output = "render" },
        // .{ .header = "SDL_scancode.h", .output = "scancode" },
        .{ .header = "SDL_sensor.h", .output = "sensor" },
        .{ .header = "SDL_storage.h", .output = "storage" },
        .{ .header = "SDL_surface.h", .output = "surface" },
        .{ .header = "SDL_system.h", .output = "system" },
        // .{ .header = "SDL_thread.h", .output = "thread" }, // Skipped: not core API
        .{ .header = "SDL_time.h", .output = "time" },
        .{ .header = "SDL_timer.h", .output = "timer" },
        .{ .header = "SDL_touch.h", .output = "touch" },
        // .{ .header = "SDL_tray.h", .output = "tray" }, // Skipped: not core API
        .{ .header = "SDL_version.h", .output = "version" },
        .{ .header = "SDL_video.h", .output = "video" },
        // .{ .header = "SDL_vulkan.h", .output = "vulkan" }, // Skipped: Vulkan interop
    };

    const regenerate_step = b.step("generate", "Regenerate bindings from SDL headers");
    const header_root = if (source_dir) |dir|
        b.fmt("{s}/{s}", .{ dir, header_root_suffix.? })
    else
        "sdl3/include/SDL3";
    const output_root = if (effective_output_dir) |dir| b.fmt("{s}/api", .{dir}) else "api";
    const json_root = if (effective_output_dir) |dir| b.fmt("{s}/json", .{dir}) else "json";

    const timestamp_arg = b.fmt("--timestamp={d}", .{timestamp});

    for (headers_to_generate) |header_info| {
        const regenerate = b.addRunArtifact(parser_exe);
        regenerate.addArg(b.fmt("{s}/{s}", .{ header_root, header_info.header }));
        regenerate.addArg(b.fmt("--output={s}/{s}.zig", .{ output_root, header_info.output }));
        regenerate.addArg(timestamp_arg);
        if (basedir) |dir| {
            regenerate.addArg(b.fmt("--basedir={s}", .{dir}));
        }
        // regenerate.addArg(b.fmt("--output=api/{s}.zig --mocks=mocks/{s}.c", .{ header_info.output, header_info.output }));
        regenerate.step.dependOn(path_prep_step);
        regenerate_step.dependOn(&regenerate.step);

        const regenerateJson = b.addRunArtifact(parser_exe);
        regenerateJson.addArg(b.fmt("{s}/{s}", .{ header_root, header_info.header }));
        regenerateJson.addArg(b.fmt("--generate-json={s}/{s}.json", .{ json_root, header_info.output }));
        regenerateJson.addArg(timestamp_arg);
        if (basedir) |dir| {
            regenerateJson.addArg(b.fmt("--basedir={s}", .{dir}));
        }
        regenerateJson.step.dependOn(path_prep_step);
        regenerate_step.dependOn(&regenerateJson.step);
    }
}

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

    const fetch_sdl_step = addFetchSdlStep(b);

    // Parser executable
    const parser_exe = b.addExecutable(.{
        .name = "sdl-parser",
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/parser.zig"),
            .target = target,
            .optimize = optimize,
        }),
    });

    b.installArtifact(parser_exe);

    generateApi(b, parser_exe, fetch_sdl_step);

    // Run command
    const run_cmd = b.addRunArtifact(parser_exe);
    run_cmd.step.dependOn(b.getInstallStep());

    if (b.args) |args| {
        run_cmd.addArgs(args);
    }

    const run_step = b.step("run", "Run the SDL3 header parser");
    run_step.dependOn(&run_cmd.step);

    // Test mocks generation target
    const test_mocks_cmd = b.addRunArtifact(parser_exe);
    test_mocks_cmd.step.dependOn(b.getInstallStep());

    const test_header_path = b.path("test_small.h");
    const test_output = b.path("zig-out/test_small.zig");
    const test_mocks = b.path("zig-out/test_small_mock.c");

    test_mocks_cmd.addArg(test_header_path.getPath(b));
    test_mocks_cmd.addArg(b.fmt("--output={s}", .{test_output.getPath(b)}));
    test_mocks_cmd.addArg(b.fmt("--mocks={s}", .{test_mocks.getPath(b)}));

    const test_mocks_step = b.step("test-mocks", "Test mock generation with test_small.h");
    test_mocks_step.dependOn(&test_mocks_cmd.step);

    // Tests
    const parser_tests = b.addTest(.{
        .root_module = b.createModule(.{
            .root_source_file = b.path("src/parser.zig"),
            .target = target,
            .optimize = optimize,
        }),
    });

    const run_tests = b.addRunArtifact(parser_tests);

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