import hmac
import logging
import os
import re
import uuid
from functools import wraps

from flask import (
    Blueprint, abort, current_app, flash, jsonify, redirect, render_template,
    request, session, url_for,
)
from werkzeug.security import check_password_hash

from app import db, log_action, sanitize_html, AuditLog, Section, Topic

admin_bp = Blueprint("admin", __name__, url_prefix="/admin")

auth_log = logging.getLogger("jqc.auth")

MEDIA_TYPES = ("none", "image", "video", "embed")

# In-body image uploads (rich-text editor). Extension allowlist plus a
# magic-byte sniff so a renamed file can't slip a non-image through. SVG is
# deliberately excluded (it can carry script). 8 MB cap.
ALLOWED_IMAGE_EXT = {"png", "jpg", "jpeg", "gif", "webp"}
MAX_UPLOAD_BYTES = 8 * 1024 * 1024


def _sniff_image(head):
    """Return a canonical extension if `head` (first bytes of a file) looks like
    a supported image, else None."""
    if head[:8] == b"\x89PNG\r\n\x1a\n":
        return "png"
    if head[:3] == b"\xff\xd8\xff":
        return "jpg"
    if head[:6] in (b"GIF87a", b"GIF89a"):
        return "gif"
    if head[:4] == b"RIFF" and head[8:12] == b"WEBP":
        return "webp"
    return None


# ------------------------------------------------------------------ auth
def login_required(view):
    @wraps(view)
    def wrapped(*args, **kwargs):
        if not session.get("admin"):
            return redirect(url_for("admin.login", next=request.path))
        return view(*args, **kwargs)
    return wrapped


@admin_bp.route("/login", methods=["GET", "POST"])
def login():
    if session.get("admin"):
        return redirect(url_for("admin.dashboard"))

    if request.method == "POST":
        username = request.form.get("username", "")
        password = request.form.get("password", "")
        cfg = current_app.config
        expected_user = cfg.get("ADMIN_USERNAME", "")
        pw_hash = cfg.get("ADMIN_PASSWORD_HASH", "")

        user_ok = hmac.compare_digest(username, expected_user)
        pass_ok = bool(pw_hash) and check_password_hash(pw_hash, password)

        # Sanitize the attacker-controlled username before logging: collapse all
        # whitespace (kills CR/LF log-injection) and cap length. The real client
        # IP is logged LAST so a crafted username can't spoof the '... from <ip>'
        # token the fail2ban filter anchors on at end-of-line.
        safe_user = re.sub(r"\s+", " ", username).strip()[:64] or "-"
        client_ip = request.remote_addr or "-"

        if user_ok and pass_ok:
            session.clear()
            session["admin"] = username
            auth_log.info("LOGIN OK user=%s from %s", safe_user, client_ip)
            dest = request.args.get("next", "")
            # only allow local admin redirects
            if not dest.startswith("/admin"):
                dest = url_for("admin.dashboard")
            return redirect(dest)
        auth_log.warning("FAILED LOGIN user=%s from %s", safe_user, client_ip)
        flash("Incorrect username or password.", "error")

    return render_template("admin/login.html")


@admin_bp.route("/logout", methods=["POST"])
def logout():
    session.clear()
    flash("Signed out.", "ok")
    return redirect(url_for("admin.login"))


# ------------------------------------------------------------------ helpers
def _slugify(value):
    value = (value or "").strip().lower()
    value = re.sub(r"[^\w\s-]", "", value)
    value = re.sub(r"[\s_]+", "-", value).strip("-")
    return value or "topic"


def _unique_slug(base, exclude_id=None):
    slug = base
    n = 2
    while True:
        q = Topic.query.filter_by(slug=slug)
        if exclude_id is not None:
            q = q.filter(Topic.id != exclude_id)
        if not q.first():
            return slug
        slug = f"{base}-{n}"
        n += 1


def _int(value, default=0):
    try:
        return int(value)
    except (TypeError, ValueError):
        return default


# ------------------------------------------------------------------ dashboard
@admin_bp.route("/")
@login_required
def dashboard():
    sections = Section.query.order_by(Section.sort_order, Section.num).all()
    return render_template("admin/dashboard.html", sections=sections)


# ------------------------------------------------------------------ audit log
@admin_bp.route("/audit")
@login_required
def audit():
    page = _int(request.args.get("page"), 1)
    if page < 1:
        page = 1
    action = request.args.get("action", "")
    entity = request.args.get("entity", "")

    q = AuditLog.query
    if action in ("create", "update", "delete"):
        q = q.filter(AuditLog.action == action)
    if entity in ("section", "topic"):
        q = q.filter(AuditLog.entity == entity)

    pagination = (
        q.order_by(AuditLog.created_at.desc(), AuditLog.id.desc())
        .paginate(page=page, per_page=50, error_out=False)
    )
    return render_template(
        "admin/audit.html",
        pagination=pagination,
        entries=pagination.items,
        action=action,
        entity=entity,
    )


# ------------------------------------------------------------------ topics
@admin_bp.route("/topic/new", methods=["GET", "POST"])
@admin_bp.route("/topic/<int:topic_id>", methods=["GET", "POST"])
@login_required
def topic_form(topic_id=None):
    topic = Topic.query.get_or_404(topic_id) if topic_id else None
    sections = Section.query.order_by(Section.sort_order, Section.num).all()

    if request.method == "POST":
        f = request.form
        title = f.get("title", "").strip()
        section_id = _int(f.get("section_id"))
        if not title or not section_id:
            flash("Title and section are required.", "error")
            return render_template(
                "admin/topic_form.html", topic=topic, sections=sections,
                media_types=MEDIA_TYPES, form=f,
            )

        media_type = f.get("media_type", "none")
        if media_type not in MEDIA_TYPES:
            media_type = "none"

        slug_input = f.get("slug", "").strip()
        base_slug = _slugify(slug_input or title)
        slug = _unique_slug(base_slug, exclude_id=topic.id if topic else None)

        is_new = topic is None
        if is_new:
            topic = Topic()

        topic.section_id = section_id
        topic.slug = slug
        topic.title = title
        topic.body_html = sanitize_html(f.get("body_html", ""))
        topic.link_url = f.get("link_url", "").strip() or None
        topic.link_label = f.get("link_label", "").strip() or None
        topic.media_type = media_type
        topic.media_url = f.get("media_url", "").strip() or None
        topic.media_caption = f.get("media_caption", "").strip() or None
        topic.sort_order = _int(f.get("sort_order"), 0)
        topic.is_published = f.get("is_published") == "1"

        if is_new:
            db.session.add(topic)
        db.session.commit()
        log_action(
            session.get("admin"), "create" if is_new else "update",
            "topic", topic.id, topic.title,
        )
        flash(f"Topic '{topic.title}' saved.", "ok")
        return redirect(url_for("admin.dashboard"))

    return render_template(
        "admin/topic_form.html", topic=topic, sections=sections,
        media_types=MEDIA_TYPES, form=None,
    )


@admin_bp.route("/topic/<int:topic_id>/delete", methods=["POST"])
@login_required
def topic_delete(topic_id):
    topic = Topic.query.get_or_404(topic_id)
    title, tid = topic.title, topic.id
    db.session.delete(topic)
    db.session.commit()
    log_action(session.get("admin"), "delete", "topic", tid, title)
    flash(f"Topic '{title}' deleted.", "ok")
    return redirect(url_for("admin.dashboard"))


@admin_bp.route("/topic/<int:topic_id>/toggle", methods=["POST"])
@login_required
def topic_toggle(topic_id):
    topic = Topic.query.get_or_404(topic_id)
    topic.is_published = not topic.is_published
    db.session.commit()
    state = "published" if topic.is_published else "unpublished (draft)"
    log_action(session.get("admin"), "update", "topic", topic.id,
               f"{state}: {topic.title}")
    flash(f"'{topic.title}' is now {state}.", "ok")
    return redirect(url_for("admin.dashboard"))


# ------------------------------------------------------------------ reorder
@admin_bp.route("/reorder", methods=["POST"])
@login_required
def reorder():
    """Persist drag-and-drop order. JSON body:
       {"type":"topic","section_id":N,"order":[id,...]}  reorder within a section
       {"type":"section","order":[id,...]}               reorder sections
    Sort values are rewritten to 10,20,30,... in the given order."""
    data = request.get_json(silent=True) or {}
    kind = data.get("type")
    order = data.get("order") or []
    if kind not in ("topic", "section") or not isinstance(order, list):
        abort(400)

    ids = []
    for v in order:
        iv = _int(v, None)
        if iv is None:
            abort(400)
        ids.append(iv)

    if kind == "topic":
        section_id = _int(data.get("section_id"), None)
        if section_id is None:
            abort(400)
        # Only reorder topics that actually belong to this section.
        rows = {t.id: t for t in Topic.query.filter(
            Topic.section_id == section_id, Topic.id.in_(ids)
        ).all()}
        for i, tid in enumerate(ids):
            if tid in rows:
                rows[tid].sort_order = (i + 1) * 10
        detail = f"reordered {len(rows)} topics in section {section_id}"
        entity = "topic"
    else:
        rows = {s.id: s for s in Section.query.filter(Section.id.in_(ids)).all()}
        for i, sid in enumerate(ids):
            if sid in rows:
                rows[sid].sort_order = (i + 1) * 10
        detail = f"reordered {len(rows)} sections"
        entity = "section"

    db.session.commit()
    log_action(session.get("admin"), "update", entity, None, detail)
    return jsonify(ok=True)


# ------------------------------------------------------------------ uploads
@admin_bp.route("/upload", methods=["POST"])
@login_required
def upload():
    """Store an image dropped/picked in the rich-text editor and return its
    public URL as JSON: {"url": "/static/uploads/<name>"}. CSRF is enforced by
    the global CSRFProtect via the X-CSRFToken header the editor sends."""
    file = request.files.get("file")
    if file is None or not file.filename:
        return jsonify(error="No file provided."), 400

    if request.content_length and request.content_length > MAX_UPLOAD_BYTES:
        return jsonify(error="File too large (max 8 MB)."), 413

    ext = file.filename.rsplit(".", 1)[-1].lower() if "." in file.filename else ""
    if ext not in ALLOWED_IMAGE_EXT:
        return jsonify(error="Unsupported file type."), 400

    # Verify the bytes actually look like an image, not just the name.
    head = file.stream.read(12)
    file.stream.seek(0)
    sniffed = _sniff_image(head)
    if sniffed is None:
        return jsonify(error="File is not a valid image."), 400

    upload_dir = os.path.join(current_app.static_folder, "uploads")
    os.makedirs(upload_dir, exist_ok=True)
    name = f"{uuid.uuid4().hex}.{sniffed}"
    file.save(os.path.join(upload_dir, name))

    log_action(session.get("admin"), "create", "upload", None, name)
    return jsonify(url=url_for("static", filename=f"uploads/{name}"))


# ------------------------------------------------------------------ sections
@admin_bp.route("/section/new", methods=["GET", "POST"])
@admin_bp.route("/section/<int:section_id>", methods=["GET", "POST"])
@login_required
def section_form(section_id=None):
    section = Section.query.get_or_404(section_id) if section_id else None

    if request.method == "POST":
        f = request.form
        title = f.get("title", "").strip()
        num = _int(f.get("num"))
        if not title or not num:
            flash("Number and title are required.", "error")
            return render_template("admin/section_form.html", section=section, form=f)

        # enforce unique num
        clash = Section.query.filter(Section.num == num)
        if section:
            clash = clash.filter(Section.id != section.id)
        if clash.first():
            flash(f"Section number {num} is already in use.", "error")
            return render_template("admin/section_form.html", section=section, form=f)

        is_new = section is None
        if is_new:
            section = Section()
        section.num = num
        section.title = title
        section.subtitle = f.get("subtitle", "").strip() or None
        section.sort_order = _int(f.get("sort_order"), num * 10)

        if is_new:
            db.session.add(section)
        db.session.commit()
        log_action(
            session.get("admin"), "create" if is_new else "update",
            "section", section.id, section.title,
        )
        flash(f"Section '{section.title}' saved.", "ok")
        return redirect(url_for("admin.dashboard"))

    return render_template("admin/section_form.html", section=section, form=None)


@admin_bp.route("/section/<int:section_id>/delete", methods=["POST"])
@login_required
def section_delete(section_id):
    section = Section.query.get_or_404(section_id)
    title, sid = section.title, section.id
    db.session.delete(section)  # cascades to its topics
    db.session.commit()
    log_action(session.get("admin"), "delete", "section", sid, title)
    flash(f"Section '{title}' and its topics deleted.", "ok")
    return redirect(url_for("admin.dashboard"))