diff --git a/.gitignore b/.gitignore
index 750baeb..db515d2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
+out
+
+# Nix
 result
 result-*
diff --git a/main.py b/main.py
index 7004567..0c56a44 100755
--- a/main.py
+++ b/main.py
@@ -1,7 +1,12 @@
 #!/usr/bin/env python3
 
+from __future__ import annotations
+from typing import Any
+
 import argparse
 import json
+from collections import Counter
+from dataclasses import dataclass
 from pathlib import Path
 
 
@@ -13,40 +18,134 @@ def main():
         "passwd_file",
         type=Path,
         help="Path to the passwd file.",
+        metavar="PASSWD_FILE",
     )
     parser.add_argument(
         "group_file",
         type=Path,
         help="Path to the group file.",
+        metavar="GROUP_FILE",
     )
     parser.add_argument(
         "shadow_file",
         type=Path,
         help="Path to the shadow file.",
+        metavar="SHADOW_FILE",
     )
+
     parser.add_argument(
-        "output_dir",
+        "--output_dir",
         type=Path,
         help="Path to a directory to store json user records.",
+        metavar="OUTPUT_DIR",
+        default="out",
     )
+
+    parser.add_argument(
+        "--email-domain",
+        type=str,
+        required=False,
+        metavar="DOMAIN",
+    )
+
+    parser.add_argument(
+        "--ignore-user-file",
+        type=Path,
+        required=False,
+        metavar="IGNORE_USER_FILE",
+    )
+
+    parser.add_argument(
+        "--ignore-group-file",
+        type=Path,
+        required=False,
+        metavar="IGNORE_GROUP_FILE",
+    )
+
     args = parser.parse_args()
 
-    parsed_users = parse_passwd_file(args.passwd_file)
-    parsed_groups = parse_group_file(args.group_file)
-    parsed_shadow = parse_shadow_file(args.shadow_file)
+    users = parse_passwd_file(args.passwd_file)
+    groups = parse_group_file(args.group_file)
+    shadow = parse_shadow_file(args.shadow_file)
 
-    for user in parsed_users:
-        print(json.dumps(user, indent=2))
+    ignore_users_from_file(args.ignore_user_file, users)
+    ignore_groups_from_file(args.ignore_group_file, groups)
 
-    for group in parsed_groups:
-        print(json.dumps(group, indent=2))
+    ensure_no_overlapping_uids(users)
+    ensure_no_overlapping_gids(groups)
 
-    for shadow_entry in parsed_shadow:
-        print(json.dumps(shadow_entry, indent=2))
+    if args.email_domain:
+        for user in users.values():
+            user.email = f"{user.name}@{args.email_domain}"
+
+    if not args.output_dir.exists():
+        args.output_dir.mkdir(parents=True)
+    user_dir = args.output_dir / "users"
+    user_dir.mkdir(exist_ok=True)
+    group_dir = args.output_dir / "groups"
+    group_dir.mkdir(exist_ok=True)
+
+    # print_group_stats(groups, users)
+
+    for user in users.values():
+        user.fix_full_name()
+        user.set_is_admin(groups)
+        user.set_member_of(groups)
+        if user.name in shadow:
+            user.set_shadow_entry(shadow[user.name])
+
+        with open(args.output_dir / "users" / f"{user.name}.json", "w") as f:
+            json.dump(user.to_systemd_user_record(), f, indent=2)
+
+    for group in groups.values():
+        with open(args.output_dir / "groups" / f"{group.name}.json", "w") as f:
+            json.dump(group.to_systemd_group_record(), f, indent=2)
 
 
-def parse_passwd_file(passwd_file: Path) -> list[dict]:
-    users = []
+def ensure_no_overlapping_uids(users: dict[str, User]):
+    uid_counts = Counter(user.uid for user in users.values())
+    overlapping_uids = {uid: count for uid, count in uid_counts.items() if count > 1}
+    if overlapping_uids:
+        print("Error: Found overlapping UIDs:")
+        for uid, count in overlapping_uids.items():
+            print(f"  UID {uid} is used by {count} users")
+        raise ValueError("Overlapping UIDs found")
+
+
+def ensure_no_overlapping_gids(groups: dict[str, Group]):
+    gid_counts = Counter(group.gid for group in groups.values())
+    overlapping_gids = {gid: count for gid, count in gid_counts.items() if count > 1}
+    if overlapping_gids:
+        print("Error: Found overlapping GIDs:")
+        for gid, count in overlapping_gids.items():
+            print(f"  GID {gid} is used by {count} groups")
+        raise ValueError("Overlapping GIDs found")
+
+
+def ignore_users_from_file(ignore_user_file: Path | None, users: dict[str, User]):
+    if ignore_user_file:
+        with ignore_user_file.open("r") as f:
+            for line in f:
+                if line.startswith("#") or not line.strip():
+                    continue
+                username = line.strip()
+                if username in users:
+                    del users[username]
+
+
+def ignore_groups_from_file(ignore_group_file: Path | None, groups: dict[str, Group]):
+    if ignore_group_file:
+        with ignore_group_file.open("r") as f:
+            for line in f:
+                if line.startswith("#") or not line.strip():
+                    continue
+                groupname = line.strip()
+                if groupname in groups:
+                    del groups[groupname]
+
+
+def parse_passwd_file(passwd_file: Path) -> dict[str, User]:
+    users = {}
     with passwd_file.open("r") as f:
         for line in f:
             if line.startswith("#") or not line.strip():
@@ -55,31 +154,28 @@ def parse_passwd_file(passwd_file: Path) -> list[dict]:
             if len(parts) < 7:
                 print(f"Warning: Skipping malformed line: {line.strip()}")
                 continue
-            user = {
-                "name": parts[0],
-                "uid": int(parts[2]),
-                "gid": int(parts[3]),
-                "gecos": parse_passwd_gecos(parts[4]),
-                "home": parts[5],
-                "shell": parts[6],
-            }
-            users.append(user)
+
+            gecos = parts[4].split(",")
+
+            user = User(
+                name=parts[0],
+                uid=int(parts[2]),
+                gid=int(parts[3]),
+                home=parts[5],
+                shell=parts[6],
+                full_name=gecos[0] if len(gecos) > 0 else None,
+                location=gecos[1] if len(gecos) > 1 else None,
+                work_phone=gecos[2] if len(gecos) > 2 else None,
+                home_phone=gecos[3] if len(gecos) > 3 else None,
+                other=gecos[4] if len(gecos) > 4 else None,
+            )
+
+            users[user.name] = user
     return users
 
 
-def parse_passwd_gecos(gecos: str) -> dict:
-    parts = gecos.split(",")
-    return {
-        "full_name": parts[0] if len(parts) > 0 else "",
-        "room_number": parts[1] if len(parts) > 1 else "",
-        "work_phone": parts[2] if len(parts) > 2 else "",
-        "home_phone": parts[3] if len(parts) > 3 else "",
-        "other": parts[4] if len(parts) > 4 else "",
-    }
-
-
-def parse_group_file(group_file: Path) -> list[dict]:
-    groups = []
+def parse_group_file(group_file: Path) -> dict[str, Group]:
+    groups = {}
     with group_file.open("r") as f:
         for line in f:
             if line.startswith("#") or not line.strip():
@@ -88,17 +184,17 @@ def parse_group_file(group_file: Path) -> list[dict]:
             if len(parts) < 4:
                 print(f"Warning: Skipping malformed line: {line.strip()}")
                 continue
-            group = {
-                "name": parts[0],
-                "gid": int(parts[2]),
-                "members": parts[3].split(",") if parts[3] else [],
-            }
-            groups.append(group)
+            group = Group(
+                name=parts[0],
+                gid=int(parts[2]),
+                members=parts[3].split(",") if parts[3] else [],
+            )
+            groups[group.name] = group
     return groups
 
 
-def parse_shadow_file(shadow_file: Path) -> list[dict]:
-    shadow_entries = []
+def parse_shadow_file(shadow_file: Path) -> dict[str, dict]:
+    shadow_entries = {}
     with shadow_file.open("r") as f:
         for line in f:
             if line.startswith("#") or not line.strip():
@@ -109,7 +205,7 @@ def parse_shadow_file(shadow_file: Path) -> list[dict]:
                 continue
             shadow_entry = {
                 "name": parts[0],
-                "password": parts[1],
+                "password": parts[1] if parts[1] not in {"!", "!*", "*K*"} else None,
                 "last_change": int(parts[2]) if parts[2].isdigit() else None,
                 "min_days": int(parts[3]) if parts[3].isdigit() else None,
                 "max_days": int(parts[4]) if parts[4].isdigit() else None,
@@ -118,9 +214,164 @@ def parse_shadow_file(shadow_file: Path) -> list[dict]:
                 "expire_date": int(parts[7]) if parts[7].isdigit() else None,
                 "reserved": parts[8],
             }
-            shadow_entries.append(shadow_entry)
+            shadow_entries[shadow_entry["name"]] = shadow_entry
     return shadow_entries
 
 
+@dataclass
+class User:
+    name: str
+    uid: int
+    gid: int
+    home: str
+    shell: str
+
+    full_name: str | None = None
+    location: str | None = None
+    work_phone: str | None = None
+    home_phone: str | None = None
+    other: str | None = None
+
+    memberOf: list[str] | None = None
+    email: str | None = None
+    is_admin: bool = False
+
+    password: str | None = None
+    password_last_change: int | None = None
+    password_min_days: int | None = None
+    password_max_days: int | None = None
+    password_warn_days: int | None = None
+    password_inactive_days: int | None = None
+    password_expire_date: int | None = None
+    password_reserved: str | None = None
+
+    def fix_full_name(self):
+        if self.full_name is None:
+            return
+        self.full_name = (
+            self.full_name.strip()
+            .replace("{", "æ")
+            .replace("[", "æ")
+            .replace("|", "ø")
+            .replace("\\", "Ø")
+            .replace("}", "å")
+            .replace("]", "Å")
+        )
+
+    def set_is_admin(self, groups: dict[str, Group]) -> bool:
+        if self.gid == 0:
+            self.is_admin = True
+
+        if (
+            self.name
+            in groups.get("wheel", Group(name="wheel", gid=0, members=[])).members
+        ):
+            self.is_admin = True
+
+        self.is_admin = False
+
+        return self.is_admin
+
+    def set_member_of(self, groups: dict[str, Group]) -> list[str]:
+        self.memberOf = []
+        for group in groups.values():
+            if self.name in group.members:
+                self.memberOf.append(group.name)
+        return self.memberOf
+
+    def set_shadow_entry(self, shadow_entry: dict):
+        self.password = shadow_entry.get("password")
+        self.password_last_change = shadow_entry.get("last_change")
+        self.password_min_days = shadow_entry.get("min_days")
+        self.password_max_days = shadow_entry.get("max_days")
+        self.password_warn_days = shadow_entry.get("warn_days")
+        self.password_inactive_days = shadow_entry.get("inactive_days")
+        self.password_expire_date = shadow_entry.get("expire_date")
+        self.password_reserved = shadow_entry.get("reserved")
+
+    def get_disposition(self) -> str:
+        if self.uid == 0:
+            return "intrinsic"
+        if self.uid < 1000:
+            return "system"
+        return "regular"
+
+    def get_locked(self) -> bool:
+        return self.shell in [
+            # PVV specific
+            "/bin/sperret",
+            "/bin/msgsh",
+        ]
+
+    def to_systemd_user_record(self) -> dict[str, Any]:
+        result: dict[str, Any] = {
+            "userName": self.name,
+            "realName": self.full_name,
+            "disposition": self.get_disposition(),
+            "shell": self.shell,
+            "umask": "0022",
+            "locked": self.get_locked(),
+            "storage": "classic",
+            "uid": self.uid,
+            "gid": self.gid,
+            "homeDirectory": self.home,
+            # "mountNoDevices": True,
+            # "mountNoSuid": True,
+            # "mountNoExecute": False,
+        }
+
+        if self.email:
+            result["emailAddress"] = self.email
+        if self.location:
+            result["location"] = self.location
+        if self.memberOf:
+            result["memberOf"] = self.memberOf
+
+        if self.password is not None:
+            result["privileged"] = {
+                "hashedPassword": self.password,
+            }
+
+        return result
+
+
+@dataclass
+class Group:
+    name: str
+    gid: int
+    members: list[str]
+
+    def to_systemd_group_record(self) -> dict[str, Any]:
+        return {
+            "groupName": self.name,
+            "gid": self.gid,
+            "members": self.members,
+        }
+
+
+def print_group_stats(
+    groups: dict[str, Group],
+    users: dict[str, User],
+):
+    group_counter = Counter()
+    for user in users.values():
+        group_counter[user.gid] += 1
+
+    print("| Group Name    | GID     | Member Count |")
+    print("|---------------|---------|--------------|")
+    for gid, count in sorted(
+        group_counter.items(), key=lambda x: (x[1], x[0]), reverse=True
+    ):
+        group = next((g for g in groups.values() if g.gid == gid), None)
+        if group:
+            print(
+                f"| {group.name.ljust(13)} | {str(gid).ljust(7)} | {str(count).ljust(12)} |"
+            )
+            if count < 20:
+                print(
+                    f"  Members: {', '.join(u.name + (' (locked)' if u.get_locked() else '') for u in users.values() if u.gid == gid)}"
+                )
+
+
 if __name__ == "__main__":
     main()