const std = @import("std");
const builtin = @import("builtin");
const fmt = std.fmt;
const mem = std.mem;

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

    // Process DerivedCoreProperties.txt
    var cp_file = try std.fs.cwd().openFile("data/unicode/DerivedCoreProperties.txt", .{});
    defer cp_file.close();
    var cp_buf = std.io.bufferedReader(cp_file.reader());
    const cp_reader = cp_buf.reader();

    var cp_map = std.AutoHashMap(u21, void).init(allocator);
    defer cp_map.deinit();

    var line_buf: [4096]u8 = undefined;

    cp_lines: while (try cp_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 => {
                    // Core property
                    if (!mem.eql(u8, field, "Changes_When_Casefolded")) continue :cp_lines;
                    for (current_code[0]..current_code[1] + 1) |cp| try cp_map.put(@intCast(cp), {});
                },
                else => {},
            }
        }
    }

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

    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.deflate.compressor;
    var out_file = try std.fs.cwd().createFile(output_path, .{});
    defer out_file.close();
    var out_comp = try compressor(allocator, out_file.writer(), .{ .level = .best_compression });
    defer out_comp.deinit();
    const writer = out_comp.writer();

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

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

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

        var field_iter = mem.tokenizeSequence(u8, no_comment, "; ");
        var cps: [4]u24 = undefined;
        var len: usize = 2;

        var i: usize = 0;
        while (field_iter.next()) |field| : (i += 1) {
            switch (i) {
                0 => {
                    var cp = try fmt.parseInt(u21, field, 16);
                    cp <<= 1;
                    if (cp_map.contains(cp)) cp |= 1;
                    cps[0] = cp;
                },

                1 => {
                    if (!mem.eql(u8, field, "C") and !mem.eql(u8, field, "F")) continue :lines;
                    if (mem.eql(u8, field, "F")) len = 3;
                },

                2 => {
                    if (len == 3) {
                        // Full case fold
                        // std.debug.print("-->{s} {s}\n", .{ line, field });
                        var cp_iter = mem.tokenizeScalar(u8, field, ' ');
                        len = 1;
                        while (cp_iter.next()) |cp_str| : (len += 1) {
                            cps[len] = try fmt.parseInt(u24, cp_str, 16);
                        }
                    } else {
                        // Common case fold
                        cps[1] = try fmt.parseInt(u24, field, 16);
                    }
                },

                else => {},
            }
        }

        try writer.writeInt(u8, @intCast(len), endian);
        for (cps[0..len]) |cp| try writer.writeInt(u24, cp, endian);
    }

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