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

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

    // Process UnicodeData.txt
    var write_buf: [4096]u8 = undefined;

    var in_reader = std.io.Reader.fixed(@embedFile("UnicodeData.txt"));
    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!");

    var out_file = try std.fs.cwd().createFile(output_path, .{});
    defer out_file.close();
    var writer = out_file.writer(&write_buf);

    const endian = builtin.cpu.arch.endian();

    lines: while (in_reader.takeDelimiterInclusive('\n')) |took| {
        const line = std.mem.trimRight(u8, took, "\n");
        if (line.len == 0) continue;

        var field_iter = std.mem.splitScalar(u8, line, ';');
        var cps: [19]u24 = undefined;
        var len: u8 = 1;

        var i: usize = 0;
        while (field_iter.next()) |field| : (i += 1) {
            switch (i) {
                0 => cps[0] = try std.fmt.parseInt(u24, field, 16),

                5 => {
                    // Not compatibility.
                    if (field.len == 0 or field[0] != '<') continue :lines;
                    var cp_iter = std.mem.tokenizeScalar(u8, field, ' ');
                    _ = cp_iter.next(); // <compat type>

                    while (cp_iter.next()) |cp_str| : (len += 1) {
                        cps[len] = try std.fmt.parseInt(u24, cp_str, 16);
                    }
                },

                2 => if (line[0] == '<') continue :lines,

                else => {},
            }
        }

        try writer.interface.writeInt(u8, @intCast(len), endian);
        for (cps[0..len]) |cp| try writer.interface.writeInt(u24, cp, endian);
    } else |err| switch (err) {
        error.EndOfStream => {},
        else => {
            return err;
        },
    }

    try writer.interface.writeInt(u16, 0, endian);
    try writer.interface.flush();
}