"""
app/routes/ui.py
----------------
Web portal design switch and the pages the modern sidebar links to (MT-16).

Routes
    POST /ui/theme          switch_theme()   — flip users.ui_theme classic ↔ modern
    GET  /ui/about          about()          — About Us page
    GET  /ui/support-center support_center() — support hub of how-to cards
    GET  /ui/theme-votes    theme_votes()    — admin tally of design choices

Nothing here changes existing behaviour: the theme flag only selects which
layout shell base.html extends. Every page template is untouched.

Multi-tenant note
-----------------
`users` is a per-tenant table, so every query in this module is automatically
scoped to the caller's tenant by the routing session — the vote tally shows one
tenant's users, never the estate. There is deliberately no cross-tenant rollup
here; that belongs in the control plane if it is ever wanted.
"""

import logging

from flask import (Blueprint, render_template, redirect, request,
                   url_for, flash, current_app)
from flask_login import login_required, current_user
from sqlalchemy import func

from app import db
from app.models.user import User, ROLE_LABELS
from app.utils.audit import log_action, ACTION_UPDATE

bp = Blueprint('ui', __name__, url_prefix='/ui')

logger = logging.getLogger(__name__)

VALID_THEMES = ('classic', 'modern')


def _default_theme():
    """Fallback design for accounts that have never chosen one."""
    default = (current_app.config.get('DEFAULT_UI_THEME') or 'classic').lower()
    return default if default in VALID_THEMES else 'classic'


def _safe_next(target):
    """Only allow same-site relative redirects (open-redirect guard).

    A protocol-relative URL ('//evil.com') is a valid redirect target to the
    browser but points off-site, so the leading-slash test alone is not enough.
    """
    if not target:
        return url_for('dashboard.index')
    if target.startswith('/') and not target.startswith('//'):
        return target
    return url_for('dashboard.index')


# ── Design switch ────────────────────────────────────────────────────────────

@bp.route('/theme', methods=['POST'])
@login_required
def switch_theme():
    """Persist the user's design choice, then return them to the same page."""
    theme = (request.form.get('theme') or '').strip().lower()
    if theme not in VALID_THEMES:
        flash('Unknown design option.', 'warning')
        return redirect(_safe_next(request.form.get('next')))

    previous = current_user.ui_theme or _default_theme()
    if previous != theme:
        current_user.ui_theme = theme
        db.session.commit()

        # log_action() commits internally — always AFTER the business commit.
        log_action(
            action       = ACTION_UPDATE,
            entity_type  = 'User',
            entity_id    = current_user.id,
            entity_label = current_user.username,
            details      = f'ui_theme={previous}→{theme}',
        )
        logger.info('UI | theme switch | user=%s | %s -> %s',
                    current_user.username, previous, theme)
        flash('Now showing the {} design. You can switch back any time from '
              'the account menu.'.format('new' if theme == 'modern' else 'classic'),
              'info')

    return redirect(_safe_next(request.form.get('next')))


# ── New pages (linked from the modern sidebar) ───────────────────────────────

@bp.route('/about')
@login_required
def about():
    return render_template('ui/about.html')


@bp.route('/support-center')
@login_required
def support_center():
    return render_template('ui/support_center.html')


# ── Admin: which design are people actually keeping? ─────────────────────────

@bp.route('/theme-votes')
@login_required
def theme_votes():
    if current_user.role != 'admin':
        flash('You do not have permission to view the design vote tally.', 'danger')
        return redirect(url_for('dashboard.index'))

    default = _default_theme()

    rows = (db.session.query(User.ui_theme, func.count(User.id))
            .filter(User.active == True)          # noqa: E712 — SQL boolean
            .group_by(User.ui_theme)
            .all())
    tally = {t: 0 for t in VALID_THEMES}
    for theme, count in rows:
        key = theme if theme in VALID_THEMES else default
        tally[key] = tally.get(key, 0) + count
    total = sum(tally.values())

    by_role = (db.session.query(User.role, User.ui_theme, func.count(User.id))
               .filter(User.active == True)       # noqa: E712
               .group_by(User.role, User.ui_theme)
               .order_by(User.role)
               .all())

    return render_template('ui/theme_votes.html',
                           tally=tally, total=total, by_role=by_role,
                           default_theme=default,
                           # by_role yields raw role strings from a group_by,
                           # so hand the template the same label source the
                           # User.role_label property uses (MT-15).
                           role_labels=ROLE_LABELS)