import os
import re
import secrets
import shutil
import sqlite3
import subprocess
from functools import wraps

import bcrypt as bc
import requests as http_client
import yaml
from flask import (
    Flask,
    flash,
    redirect,
    render_template,
    request,
    session,
    url_for,
)

app = Flask(__name__)
app.secret_key = os.environ.get("SECRET_KEY", "default-secret-key")

ADMIN_USER = os.environ.get("ADMIN_USER", "admin")
ADMIN_PASSWORD = os.environ.get("ADMIN_PASSWORD", "changeme")
DB_PATH = os.environ.get("DB_PATH", "/data/users.db")
HTPASSWD_PATH = os.environ.get("HTPASSWD_PATH", "/auth/htpasswd")
GC_CONFIG = os.environ.get("GC_CONFIG", "/app/registry-gc-config.yml")
REGISTRY_DATA = os.environ.get("REGISTRY_DATA", "/var/lib/registry")
REGISTRY_URL = os.environ.get("REGISTRY_URL", "http://registry:5000")
# Host:Port ohne Schema, fuer skopeo-Ziel (z. B. "registry:5000")
REGISTRY_HOST = REGISTRY_URL.split("://", 1)[-1]

# Internal service account for registry API queries (not stored in SQLite)
_SERVICE_USER = "_service"
_SERVICE_PASSWORD = secrets.token_hex(16)
_SERVICE_PASSWORD_HASH = None


def get_db():
    conn = sqlite3.connect(DB_PATH)
    conn.row_factory = sqlite3.Row
    return conn


def init_db():
    os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)
    os.makedirs(os.path.dirname(HTPASSWD_PATH), exist_ok=True)
    conn = get_db()
    conn.execute(
        """
        CREATE TABLE IF NOT EXISTS users (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            username TEXT UNIQUE NOT NULL,
            password_hash TEXT NOT NULL,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        )
        """
    )
    conn.commit()
    conn.close()


def hash_password(password):
    """Hash password with bcrypt, using $2y$ identifier for htpasswd compatibility."""
    hashed = bc.hashpw(password.encode("utf-8"), bc.gensalt(rounds=12))
    return hashed.decode("utf-8").replace("$2b$", "$2y$", 1)


def sync_htpasswd():
    """Regenerate htpasswd file from all users in SQLite + internal service user."""
    conn = get_db()
    users = conn.execute("SELECT username, password_hash FROM users").fetchall()
    conn.close()
    with open(HTPASSWD_PATH, "w") as f:
        for user in users:
            f.write(f"{user['username']}:{user['password_hash']}\n")
        f.write(f"{_SERVICE_USER}:{_SERVICE_PASSWORD_HASH}\n")


def query_registry(path):
    """Query the registry API using the internal service account."""
    try:
        resp = http_client.get(
            f"{REGISTRY_URL}{path}",
            auth=(_SERVICE_USER, _SERVICE_PASSWORD),
            timeout=5,
        )
        if resp.ok:
            return resp.json()
    except http_client.RequestException:
        pass
    return None


# Erlaubte Zeichen in einer Image-Referenz (verhindert Shell-/Argument-Injection)
_IMAGE_REF_RE = re.compile(r"^[A-Za-z0-9][A-Za-z0-9._:/@-]*$")


def strip_registry_host(ref):
    """Entfernt einen optionalen Registry-Host (z. B. docker.io/, ghcr.io:443/)."""
    if "/" in ref:
        first, rest = ref.split("/", 1)
        if "." in first or ":" in first or first == "localhost":
            return rest
    return ref


def derive_dest(source):
    """Leitet den Ziel-Namen in unserer Registry aus der Quell-Referenz ab.

    Beispiele:
        nginx                  -> nginx:latest
        bitnami/redis:7        -> bitnami/redis:7
        ghcr.io/owner/app:v1   -> owner/app:v1
    """
    dest = strip_registry_host(source)
    last_segment = dest.rsplit("/", 1)[-1]
    if ":" not in last_segment and "@" not in last_segment:
        dest += ":latest"
    return dest


def split_dest(dest):
    """Teilt einen Ziel-Namen "repo:tag" in (repo, tag). dest hat immer einen Tag."""
    repo, _, tag = dest.rpartition(":")
    return repo, tag


# Loest ${VAR:-default} und ${VAR-default} zum Default-Wert auf.
# ${VAR}, ${VAR:?...} usw. (ohne Default) werden NICHT aufgeloest.
_VAR_DEFAULT_RE = re.compile(r"\$\{[A-Za-z_][A-Za-z0-9_]*:?-([^}]*)\}")


def resolve_compose_image(image):
    """Ersetzt Compose-Variablen mit Default (${VAR:-default}) durch den Default."""
    return _VAR_DEFAULT_RE.sub(lambda m: m.group(1), image)


def extract_compose_images(content):
    """Liest alle 'image:'-Eintraege aus den Services einer docker-compose.

    Gibt (images, ignored) zurueck. images ist None bei ungueltigem YAML.
    Variablen mit Default (${VAR:-wert}) werden aufgeloest. Eintraege mit
    nicht aufloesbaren Variablen oder auf die eigene Registry landen in ignored.
    """
    try:
        data = yaml.safe_load(content)
    except yaml.YAMLError:
        return None, []
    if not isinstance(data, dict):
        return None, []
    services = data.get("services")
    if not isinstance(services, dict):
        return [], []

    images, ignored = [], []
    for svc in services.values():
        if not isinstance(svc, dict):
            continue
        raw = svc.get("image")
        if not isinstance(raw, str) or not raw.strip():
            continue
        raw = raw.strip()
        image = resolve_compose_image(raw)
        host = image.split("/", 1)[0] if "/" in image else ""
        if not image or "$" in image or "{" in image or "}" in image:
            ignored.append(raw)  # Variable ohne Default - nicht aufloesbar
        elif host and host in (REGISTRY_HOST, request.host):
            ignored.append(image)  # zeigt bereits auf unsere Registry
        elif not _IMAGE_REF_RE.match(image):
            ignored.append(image)
        elif image not in images:
            images.append(image)
    return images, ignored


_MANIFEST_ACCEPT = ", ".join(
    [
        "application/vnd.docker.distribution.manifest.v2+json",
        "application/vnd.docker.distribution.manifest.list.v2+json",
        "application/vnd.oci.image.manifest.v1+json",
        "application/vnd.oci.image.index.v1+json",
    ]
)


def get_manifest_digest(name, reference):
    """Liefert den Manifest-Digest eines Tags (fuer das Loeschen benoetigt)."""
    try:
        resp = http_client.get(
            f"{REGISTRY_URL}/v2/{name}/manifests/{reference}",
            auth=(_SERVICE_USER, _SERVICE_PASSWORD),
            headers={"Accept": _MANIFEST_ACCEPT},
            timeout=5,
        )
        if resp.ok:
            return resp.headers.get("Docker-Content-Digest")
    except http_client.RequestException:
        pass
    return None


def delete_manifest(name, digest):
    """Loescht ein Manifest per Digest aus der Registry."""
    try:
        resp = http_client.delete(
            f"{REGISTRY_URL}/v2/{name}/manifests/{digest}",
            auth=(_SERVICE_USER, _SERVICE_PASSWORD),
            timeout=5,
        )
        return resp.status_code in (200, 202)
    except http_client.RequestException:
        return False


def repo_has_tags(name):
    """True, wenn das Repository noch mindestens einen Tag hat."""
    data = query_registry(f"/v2/{name}/tags/list")
    return bool(data and data.get("tags"))


def _repositories_base():
    return os.path.realpath(
        os.path.join(REGISTRY_DATA, "docker", "registry", "v2", "repositories")
    )


def _safe_repo_path(*parts):
    """Absoluter Pfad innerhalb des repositories-Verzeichnisses oder None (Schutz vor ../)."""
    base = _repositories_base()
    target = os.path.realpath(os.path.join(base, *parts))
    if target != base and not target.startswith(base + os.sep):
        return None
    return target


def remove_repository_storage(name):
    """Entfernt das leere Repository-Verzeichnis aus dem Registry-Speicher.

    Die Registry-API kennt kein "Repository loeschen"; nach dem Loeschen des
    letzten Tags bleibt sonst ein leerer Eintrag im Katalog stehen.
    """
    target = _safe_repo_path(*name.split("/"))
    if not target or not os.path.isdir(target):
        return False
    shutil.rmtree(target, ignore_errors=True)
    # Leere Eltern-Verzeichnisse (z. B. "bitnami" nach "bitnami/redis") aufraeumen
    base = _repositories_base()
    parent = os.path.dirname(target)
    while parent != base and os.path.isdir(parent) and not os.listdir(parent):
        try:
            os.rmdir(parent)
        except OSError:
            break
        parent = os.path.dirname(parent)
    return True


def remove_tag_storage(name, tag):
    """Entfernt den Tag-Verweis direkt aus dem Speicher.

    Noetig fuer verwaiste Tags, die noch im Katalog stehen, deren Manifest
    aber nicht mehr abrufbar ist (Loeschen ueber die API schlaegt dann fehl).
    """
    target = _safe_repo_path(*name.split("/"), "_manifests", "tags", tag)
    if not target or not os.path.isdir(target):
        return False
    shutil.rmtree(target, ignore_errors=True)
    return True


def prune_empty_repositories():
    """Entfernt alle Repositories ohne Tags aus dem Speicher. Gibt Anzahl zurueck."""
    data = query_registry("/v2/_catalog")
    if not data:
        return 0
    removed = 0
    for name in data.get("repositories", []):
        if not repo_has_tags(name) and remove_repository_storage(name):
            removed += 1
    return removed


def remote_digest(source, src_creds=None, src_token=None):
    """Liefert den Manifest-Digest eines Quell-Images, ohne es herunterzuladen."""
    cmd = ["skopeo", "inspect", "--format", "{{.Digest}}", f"docker://{source}"]
    if src_token:
        cmd += ["--registry-token", src_token]
    elif src_creds:
        cmd += ["--creds", src_creds]
    try:
        result = subprocess.run(cmd, capture_output=True, text=True, timeout=120)
        if result.returncode == 0:
            return result.stdout.strip()
    except (subprocess.SubprocessError, OSError):
        pass
    return None


def copy_image(source, src_creds=None, src_token=None):
    """Kopiert ein Image in unsere Registry.

    Gibt (status, info) zurueck:
        ("pulled", dest)   - kopiert
        ("skipped", dest)  - bereits mit gleichem Digest vorhanden
        ("error", grund)   - fehlgeschlagen
    """
    if not _IMAGE_REF_RE.match(source):
        return ("error", f"{source}: ungueltige Image-Referenz")

    dest = derive_dest(source)
    dest_name, dest_tag = split_dest(dest)

    # Doppel-Upload vermeiden: gleicher Digest schon vorhanden? (z. B. bei "latest")
    digest = remote_digest(source, src_creds, src_token)
    if digest and get_manifest_digest(dest_name, dest_tag) == digest:
        return ("skipped", dest)

    # --all kopiert alle Architekturen und erhaelt die Manifest-Liste,
    # damit der Digest mit der Quelle uebereinstimmt.
    cmd = [
        "skopeo",
        "copy",
        "--all",
        "--dest-tls-verify=false",
        f"docker://{source}",
        f"docker://{REGISTRY_HOST}/{dest}",
        "--dest-creds",
        f"{_SERVICE_USER}:{_SERVICE_PASSWORD}",
    ]
    if src_token:
        cmd += ["--src-registry-token", src_token]
    elif src_creds:
        cmd += ["--src-creds", src_creds]

    try:
        result = subprocess.run(cmd, capture_output=True, text=True, timeout=1800)
        if result.returncode == 0:
            return ("pulled", dest)
        detail = (result.stderr or result.stdout).strip().splitlines()
        return ("error", f"{source}: {detail[-1] if detail else 'Unbekannter Fehler'}")
    except subprocess.TimeoutExpired:
        return ("error", f"{source}: Zeitueberschreitung")
    except FileNotFoundError:
        return ("error", "skopeo ist nicht installiert")


def login_required(f):
    @wraps(f)
    def decorated(*args, **kwargs):
        if not session.get("logged_in"):
            return redirect(url_for("login"))
        return f(*args, **kwargs)

    return decorated


@app.route("/login", methods=["GET", "POST"])
def login():
    if request.method == "POST":
        username = request.form.get("username", "")
        password = request.form.get("password", "")
        if username == ADMIN_USER and password == ADMIN_PASSWORD:
            session["logged_in"] = True
            return redirect(url_for("users"))
        flash("Ungueltige Anmeldedaten.", "error")
    return render_template("login.html")


@app.route("/logout")
def logout():
    session.pop("logged_in", None)
    return redirect(url_for("login"))


@app.route("/")
@login_required
def users():
    conn = get_db()
    user_list = conn.execute(
        "SELECT id, username, created_at FROM users ORDER BY username"
    ).fetchall()
    conn.close()
    return render_template("users.html", users=user_list)


@app.route("/images")
@login_required
def images():
    repos = []
    data = query_registry("/v2/_catalog")
    if data:
        for name in sorted(data.get("repositories", [])):
            tags_data = query_registry(f"/v2/{name}/tags/list")
            tags = sorted(tags_data.get("tags", [])) if tags_data and tags_data.get("tags") else []
            repos.append({"name": name, "tags": tags})
    return render_template("images.html", repos=repos)


@app.route("/pull", methods=["POST"])
@login_required
def pull_image():
    source = request.form.get("source", "").strip()
    use_creds = request.form.get("use_creds") == "on"
    use_token = request.form.get("use_token") == "on"
    src_user = request.form.get("src_username", "").strip()
    src_pass = request.form.get("src_password", "")
    src_token = request.form.get("src_token", "").strip()

    if not source:
        flash("Bitte ein Quell-Image angeben.", "error")
        return redirect(url_for("images"))

    # Quell-Zugangsdaten nur anwenden, wenn die jeweilige Checkbox aktiviert ist.
    creds = f"{src_user}:{src_pass}" if (use_creds and src_user) else None
    token = src_token if (use_token and src_token) else None

    status, info = copy_image(source, creds, token)
    if status == "pulled":
        flash(f'Image "{source}" wurde als "{info}" geholt.', "success")
    elif status == "skipped":
        flash(
            f'Image "{info}" ist bereits mit gleichem Digest vorhanden - uebersprungen.',
            "success",
        )
    else:
        flash(f"Fehler beim Holen: {info}", "error")

    return redirect(url_for("images"))


@app.route("/pull-compose", methods=["POST"])
@login_required
def pull_compose():
    content = request.form.get("compose", "")
    uploaded = request.files.get("compose_file")
    if uploaded and uploaded.filename:
        try:
            content = uploaded.read().decode("utf-8")
        except UnicodeDecodeError:
            flash("Die hochgeladene Datei ist keine gueltige Textdatei.", "error")
            return redirect(url_for("images"))

    if not content.strip():
        flash("Bitte eine docker-compose einfuegen oder hochladen.", "error")
        return redirect(url_for("images"))

    images_list, ignored = extract_compose_images(content)
    if images_list is None:
        flash("Die docker-compose konnte nicht gelesen werden (ungueltiges YAML).", "error")
        return redirect(url_for("images"))
    if not images_list:
        flash("Keine verwertbaren Images in der docker-compose gefunden.", "error")
        return redirect(url_for("images"))

    use_creds = request.form.get("bulk_use_creds") == "on"
    use_token = request.form.get("bulk_use_token") == "on"
    src_user = request.form.get("bulk_src_username", "").strip()
    src_pass = request.form.get("bulk_src_password", "")
    src_token = request.form.get("bulk_src_token", "").strip()
    creds = f"{src_user}:{src_pass}" if (use_creds and src_user) else None
    token = src_token if (use_token and src_token) else None

    pulled, skipped, errors = [], [], []
    for image in images_list:
        status, info = copy_image(image, creds, token)
        if status == "pulled":
            pulled.append(info)
        elif status == "skipped":
            skipped.append(info)
        else:
            errors.append(info)

    if pulled:
        flash(f"{len(pulled)} Image(s) geholt: " + ", ".join(pulled), "success")
    if skipped:
        flash(
            f"{len(skipped)} bereits vorhanden (gleicher Digest), uebersprungen: "
            + ", ".join(skipped),
            "success",
        )
    if ignored:
        flash(
            f"{len(ignored)} Eintrag/Eintraege ignoriert (Variable oder eigene Registry): "
            + ", ".join(ignored),
            "error",
        )
    for err in errors:
        flash(f"Fehler: {err}", "error")

    return redirect(url_for("images"))


@app.route("/images/delete", methods=["POST"])
@login_required
def delete_image():
    name = request.form.get("name", "").strip()
    tag = request.form.get("tag", "").strip()

    if not name or not tag:
        flash("Image und Tag sind erforderlich.", "error")
        return redirect(url_for("images"))

    digest = get_manifest_digest(name, tag)
    # Normalfall: Manifest per Digest loeschen. Faellt der API-Lookup aus
    # (verwaister Tag: im Katalog gelistet, Manifest aber nicht abrufbar),
    # den Tag-Verweis direkt aus dem Speicher entfernen.
    manifest_deleted = delete_manifest(name, digest) if digest else False
    tag_removed = remove_tag_storage(name, tag)

    if not manifest_deleted and not tag_removed:
        flash(f'Tag "{tag}" von "{name}" wurde nicht gefunden.', "error")
        return redirect(url_for("images"))

    # War das der letzte Tag? Dann das leere Repository entfernen, damit
    # es nicht weiter (ohne Tags) im Katalog stehen bleibt.
    if not repo_has_tags(name) and remove_repository_storage(name):
        flash(
            f'Image "{name}:{tag}" geloescht - Repository "{name}" entfernt '
            "(keine Tags mehr).",
            "success",
        )
    else:
        flash(f'Image "{name}:{tag}" wurde geloescht.', "success")

    return redirect(url_for("images"))


@app.route("/images/gc", methods=["POST"])
@login_required
def garbage_collect():
    # Entfernt Blobs/Layer, die von keinem Manifest mehr referenziert werden
    # (z. B. nach dem Loeschen von Tags). Nutzt die registry-Binary direkt auf
    # dem gemounteten Speicher - kein Docker-Socket noetig.
    #
    # WICHTIG: KEIN --delete-untagged! Dieses Flag loescht bei Multi-Arch-Images
    # die per-Architektur-Manifeste (die nur ueber die Manifest-Liste referenziert
    # sind) und macht die Images damit unbrauchbar ("manifest unknown" beim Pull).
    try:
        result = subprocess.run(
            ["registry", "garbage-collect", GC_CONFIG],
            capture_output=True,
            text=True,
            timeout=600,
        )
        if result.returncode == 0:
            freed = sum(
                1
                for line in result.stdout.splitlines()
                if line.startswith("blob eligible for deletion")
            )
            pruned = prune_empty_repositories()
            extra = f" {pruned} leere(s) Repository entfernt." if pruned else ""
            flash(
                "Garbage Collection abgeschlossen. "
                f"{freed} nicht mehr benoetigte Blob(s) wurden entfernt.{extra}",
                "success",
            )
        else:
            detail = (result.stderr or result.stdout).strip().splitlines()
            reason = detail[-1] if detail else "Unbekannter Fehler"
            # Frische, leere Registry: nichts zu tun
            if "Path not found" in reason and "repositories" in reason:
                flash("Garbage Collection: keine Images vorhanden, nichts zu tun.", "success")
            else:
                flash(f"Fehler bei der Garbage Collection: {reason}", "error")
    except subprocess.TimeoutExpired:
        flash("Zeitueberschreitung bei der Garbage Collection.", "error")
    except FileNotFoundError:
        flash("registry-Binary ist nicht verfuegbar.", "error")

    return redirect(url_for("images"))


@app.route("/help")
@login_required
def help_page():
    return render_template("help.html", domain=request.host)


@app.route("/add", methods=["POST"])
@login_required
def add_user():
    username = request.form.get("username", "").strip()
    password = request.form.get("password", "")

    if not username or not password:
        flash("Benutzername und Passwort sind erforderlich.", "error")
        return redirect(url_for("users"))

    if len(password) < 6:
        flash("Passwort muss mindestens 6 Zeichen lang sein.", "error")
        return redirect(url_for("users"))

    password_h = hash_password(password)

    conn = get_db()
    try:
        conn.execute(
            "INSERT INTO users (username, password_hash) VALUES (?, ?)",
            (username, password_h),
        )
        conn.commit()
        sync_htpasswd()
        flash(f'Benutzer "{username}" wurde erstellt.', "success")
    except sqlite3.IntegrityError:
        flash(f'Benutzer "{username}" existiert bereits.', "error")
    finally:
        conn.close()

    return redirect(url_for("users"))


@app.route("/password/<int:user_id>", methods=["POST"])
@login_required
def change_password(user_id):
    password = request.form.get("password", "")

    if not password or len(password) < 6:
        flash("Passwort muss mindestens 6 Zeichen lang sein.", "error")
        return redirect(url_for("users"))

    password_h = hash_password(password)

    conn = get_db()
    conn.execute(
        "UPDATE users SET password_hash = ? WHERE id = ?",
        (password_h, user_id),
    )
    conn.commit()
    conn.close()
    sync_htpasswd()
    flash("Passwort wurde geaendert.", "success")
    return redirect(url_for("users"))


@app.route("/delete/<int:user_id>", methods=["POST"])
@login_required
def delete_user(user_id):
    conn = get_db()
    user = conn.execute(
        "SELECT username FROM users WHERE id = ?", (user_id,)
    ).fetchone()
    if user:
        conn.execute("DELETE FROM users WHERE id = ?", (user_id,))
        conn.commit()
        sync_htpasswd()
        flash(f'Benutzer "{user["username"]}" wurde geloescht.', "success")
    conn.close()
    return redirect(url_for("users"))


# Initialize database and htpasswd on startup
init_db()
_SERVICE_PASSWORD_HASH = hash_password(_SERVICE_PASSWORD)
sync_htpasswd()