const std = @import("std");
const ascii = std.ascii;

const ErrCtx = @import("ErrCtx.zig");

pub fn downCast(comptime T: type, n: u64) error{InvalidRecord}!T {
    return std.math.cast(T, n) orelse return error.InvalidRecord;
}

pub fn utf8(s: []const u8) error{InvalidRecord}!void {
    if (!std.unicode.utf8ValidateSlice(s)) {
        return error.InvalidRecord;
    }
}

// # adduser žmogus
// adduser: To avoid problems, the username should consist only of letters,
// digits, underscores, periods, at signs and dashes, and not start with a dash
// (as defined by IEEE Std 1003.1-2001). For compatibility with Samba machine
// accounts $ is also supported at the end of the username
pub fn name(s: []const u8, err: *ErrCtx) error{InvalidRecord}!void {
    if (s.len == 0)
        return err.returnf("cannot be empty", .{}, error.InvalidRecord);

    const c0 = s[0];
    if (!(ascii.isAlNum(c0) or c0 == '_' or c0 == '.' or c0 == '@'))
        return err.returnf("invalid character at position 0", .{}, error.InvalidRecord);

    for (s[1..]) |c, i| {
        if (!(ascii.isAlNum(c) or c == '_' or c == '.' or c == '@' or c == '-'))
            return err.returnf(
                "invalid character at position {d}",
                .{i + 2},
                error.InvalidRecord,
            );
    }
}

const testing = std.testing;

test "validate name" {
    const examples = [_]struct {
        name: []const u8,
        wantErr: ?[]const u8 = null,
    }{
        .{
            .name = "all-good",
        },
        .{
            .name = "...",
        },
        .{
            .name = "",
            .wantErr = "cannot be empty",
        },
        .{
            .name = "-no-start-dash",
            .wantErr = "invalid character at position 0",
        },
        .{
            .name = "Herbasž",
            .wantErr = "invalid character at position 7",
        },
    };
    for (examples) |tt| {
        var err = ErrCtx{};

        if (tt.wantErr) |wantErr| {
            try testing.expectError(error.InvalidRecord, name(tt.name, &err));
            try testing.expectEqualStrings(wantErr, err.unwrap().constSlice());
        } else {
            try name(tt.name, &err);
            try testing.expectEqualStrings("", err.unwrap().constSlice());
        }
    }
}