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

const Script = enum {
    none,
    Adlam,
    Ahom,
    Anatolian_Hieroglyphs,
    Arabic,
    Armenian,
    Avestan,
    Balinese,
    Bamum,
    Bassa_Vah,
    Batak,
    Bengali,
    Bhaiksuki,
    Bopomofo,
    Brahmi,
    Braille,
    Buginese,
    Buhid,
    Canadian_Aboriginal,
    Carian,
    Caucasian_Albanian,
    Chakma,
    Cham,
    Cherokee,
    Chorasmian,
    Common,
    Coptic,
    Cuneiform,
    Cypriot,
    Cypro_Minoan,
    Cyrillic,
    Deseret,
    Devanagari,
    Dives_Akuru,
    Dogra,
    Duployan,
    Egyptian_Hieroglyphs,
    Elbasan,
    Elymaic,
    Ethiopic,
    Georgian,
    Glagolitic,
    Gothic,
    Grantha,
    Greek,
    Gujarati,
    Gunjala_Gondi,
    Gurmukhi,
    Han,
    Hangul,
    Hanifi_Rohingya,
    Hanunoo,
    Hatran,
    Hebrew,
    Hiragana,
    Imperial_Aramaic,
    Inherited,
    Inscriptional_Pahlavi,
    Inscriptional_Parthian,
    Javanese,
    Kaithi,
    Kannada,
    Katakana,
    Kawi,
    Kayah_Li,
    Kharoshthi,
    Khitan_Small_Script,
    Khmer,
    Khojki,
    Khudawadi,
    Lao,
    Latin,
    Lepcha,
    Limbu,
    Linear_A,
    Linear_B,
    Lisu,
    Lycian,
    Lydian,
    Mahajani,
    Makasar,
    Malayalam,
    Mandaic,
    Manichaean,
    Marchen,
    Masaram_Gondi,
    Medefaidrin,
    Meetei_Mayek,
    Mende_Kikakui,
    Meroitic_Cursive,
    Meroitic_Hieroglyphs,
    Miao,
    Modi,
    Mongolian,
    Mro,
    Multani,
    Myanmar,
    Nabataean,
    Nag_Mundari,
    Nandinagari,
    New_Tai_Lue,
    Newa,
    Nko,
    Nushu,
    Nyiakeng_Puachue_Hmong,
    Ogham,
    Ol_Chiki,
    Old_Hungarian,
    Old_Italic,
    Old_North_Arabian,
    Old_Permic,
    Old_Persian,
    Old_Sogdian,
    Old_South_Arabian,
    Old_Turkic,
    Old_Uyghur,
    Oriya,
    Osage,
    Osmanya,
    Pahawh_Hmong,
    Palmyrene,
    Pau_Cin_Hau,
    Phags_Pa,
    Phoenician,
    Psalter_Pahlavi,
    Rejang,
    Runic,
    Samaritan,
    Saurashtra,
    Sharada,
    Shavian,
    Siddham,
    SignWriting,
    Sinhala,
    Sogdian,
    Sora_Sompeng,
    Soyombo,
    Sundanese,
    Syloti_Nagri,
    Syriac,
    Tagalog,
    Tagbanwa,
    Tai_Le,
    Tai_Tham,
    Tai_Viet,
    Takri,
    Tamil,
    Tangsa,
    Tangut,
    Telugu,
    Thaana,
    Thai,
    Tibetan,
    Tifinagh,
    Tirhuta,
    Toto,
    Ugaritic,
    Vai,
    Vithkuqi,
    Wancho,
    Warang_Citi,
    Yezidi,
    Yi,
    Zanabazar_Square,
};

const block_size = 256;
const Block = [block_size]u8;

const BlockMap = std.HashMap(
    Block,
    u16,
    struct {
        pub fn hash(_: @This(), k: Block) u64 {
            var hasher = std.hash.Wyhash.init(0);
            std.hash.autoHashStrat(&hasher, k, .DeepRecursive);
            return hasher.final();
        }

        pub fn eql(_: @This(), a: Block, b: Block) bool {
            return std.mem.eql(u8, &a, &b);
        }
    },
    std.hash_map.default_max_load_percentage,
);

pub fn main() !void {
    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer arena.deinit();
    const allocator = arena.allocator();

    var flat_map = std.AutoHashMap(u21, u8).init(allocator);
    defer flat_map.deinit();

    var line_buf: [4096]u8 = undefined;

    // Process DerivedGeneralCategory.txt
    var in_file = try std.fs.cwd().openFile("data/unicode/Scripts.txt", .{});
    defer in_file.close();
    var in_buf = std.io.bufferedReader(in_file.reader());
    const in_reader = in_buf.reader();

    while (try in_reader.readUntilDelimiterOrEof(&line_buf, '\n')) |line| {
        if (line.len == 0 or line[0] == '#') continue;

        const no_comment = if (std.mem.indexOfScalar(u8, line, '#')) |octo| line[0..octo] else line;

        var field_iter = std.mem.tokenizeAny(u8, no_comment, "; ");
        var current_code: [2]u21 = undefined;

        var i: usize = 0;
        while (field_iter.next()) |field| : (i += 1) {
            switch (i) {
                0 => {
                    // Code point(s)
                    if (std.mem.indexOf(u8, field, "..")) |dots| {
                        current_code = .{
                            try std.fmt.parseInt(u21, field[0..dots], 16),
                            try std.fmt.parseInt(u21, field[dots + 2 ..], 16),
                        };
                    } else {
                        const code = try std.fmt.parseInt(u21, field, 16);
                        current_code = .{ code, code };
                    }
                },
                1 => {
                    // Script
                    const script = std.meta.stringToEnum(Script, field) orelse {
                        std.debug.print("Unknown script: {s}\n", .{field});
                        return error.UnknownScript;
                    };
                    for (current_code[0]..current_code[1] + 1) |cp| try flat_map.put(@intCast(cp), @intFromEnum(script));
                },
                else => {},
            }
        }
    }

    var blocks_map = BlockMap.init(allocator);
    defer blocks_map.deinit();

    var stage1 = std.ArrayList(u16).init(allocator);
    defer stage1.deinit();

    var stage2 = std.ArrayList(u8).init(allocator);
    defer stage2.deinit();

    var stage3 = std.ArrayList(u8).init(allocator);
    defer stage3.deinit();

    var block: Block = [_]u8{0} ** block_size;
    var block_len: u16 = 0;

    for (0..0x110000) |i| {
        const cp: u21 = @intCast(i);
        const script = flat_map.get(cp) orelse 0;

        const stage3_idx = blk: {
            for (stage3.items, 0..) |script_i, j| {
                if (script == script_i) break :blk j;
            }
            try stage3.append(script);
            break :blk stage3.items.len - 1;
        };

        // Process block
        block[block_len] = @intCast(stage3_idx);
        block_len += 1;

        if (block_len < block_size and cp != 0x10ffff) continue;

        const gop = try blocks_map.getOrPut(block);
        if (!gop.found_existing) {
            gop.value_ptr.* = @intCast(stage2.items.len);
            try stage2.appendSlice(&block);
        }

        try stage1.append(gop.value_ptr.*);
        block_len = 0;
    }

    var args_iter = try std.process.argsWithAllocator(allocator);
    defer args_iter.deinit();
    _ = args_iter.skip();
    const output_path = args_iter.next() orelse @panic("No output file arg!");

    const compressor = std.compress.flate.deflate.compressor;
    var out_file = try std.fs.cwd().createFile(output_path, .{});
    defer out_file.close();
    var out_comp = try compressor(.raw, out_file.writer(), .{ .level = .best });
    const writer = out_comp.writer();

    const endian = builtin.cpu.arch.endian();
    try writer.writeInt(u16, @intCast(stage1.items.len), endian);
    for (stage1.items) |i| try writer.writeInt(u16, i, endian);

    try writer.writeInt(u16, @intCast(stage2.items.len), endian);
    for (stage2.items) |i| try writer.writeInt(u8, i, endian);

    try writer.writeInt(u8, @intCast(stage3.items.len), endian);
    for (stage3.items) |i| try writer.writeInt(u8, i, endian);

    try out_comp.flush();
}