const std = @import("std");
const mem = std.mem;
const Allocator = mem.Allocator;

const User = @This();

uid: u32,
gid: u32,
name: []const u8,
gecos: []const u8,
home: []const u8,
shell: []const u8,

// deep-clones a User record with a given Allocator.
pub fn clone(
    self: *const User,
    allocator: Allocator,
) error{OutOfMemory}!User {
    const stringdata = try allocator.alloc(u8, self.strlen());
    const gecos_start = self.name.len;
    const home_start = gecos_start + self.gecos.len;
    const shell_start = home_start + self.home.len;
    mem.copy(u8, stringdata[0..self.name.len], self.name);
    mem.copy(u8, stringdata[gecos_start..], self.gecos);
    mem.copy(u8, stringdata[home_start..], self.home);
    mem.copy(u8, stringdata[shell_start..], self.shell);

    return User{
        .uid = self.uid,
        .gid = self.gid,
        .name = stringdata[0..self.name.len],
        .gecos = stringdata[gecos_start .. gecos_start + self.gecos.len],
        .home = stringdata[home_start .. home_start + self.home.len],
        .shell = stringdata[shell_start .. shell_start + self.shell.len],
    };
}

fn strlen(self: *const User) usize {
    return self.name.len +
        self.gecos.len +
        self.home.len +
        self.shell.len;
}

pub fn deinit(self: *User, allocator: Allocator) void {
    const slice = self.home.ptr[0..self.strlen()];
    allocator.free(slice);
    self.* = undefined;
}

const testing = std.testing;

test "User.clone" {
    var allocator = testing.allocator;
    const user = User{
        .uid = 1000,
        .gid = 1000,
        .name = "vidmantas",
        .gecos = "Vidmantas Kaminskas",
        .home = "/home/vidmantas",
        .shell = "/bin/bash",
    };
    var user2 = try user.clone(allocator);
    defer user2.deinit(allocator);

    try testing.expectEqualStrings(user.shell, "/bin/bash");
}