from flask import Blueprint, request, jsonify
from datetime import datetime, timedelta
from util.logger import logger
from auth.token import verify_token

cron_blueprint = Blueprint('cron_tool', __name__)

MONTH_NAMES = {
    '1': 'Januar', '2': 'Februar', '3': 'März', '4': 'April',
    '5': 'Mai', '6': 'Juni', '7': 'Juli', '8': 'August',
    '9': 'September', '10': 'Oktober', '11': 'November', '12': 'Dezember',
}
WEEKDAY_NAMES = {
    '0': 'Sonntag', '1': 'Montag', '2': 'Dienstag', '3': 'Mittwoch',
    '4': 'Donnerstag', '5': 'Freitag', '6': 'Samstag', '7': 'Sonntag',
}


def parse_field(field, min_val, max_val):
    values = set()
    for part in field.split(','):
        part = part.strip()
        if part == '*':
            values.update(range(min_val, max_val + 1))
        elif '/' in part:
            base, step = part.split('/', 1)
            step = int(step)
            if base == '*':
                start, end = min_val, max_val
            elif '-' in base:
                s, e = base.split('-')
                start, end = int(s), int(e)
            else:
                start, end = int(base), max_val
            values.update(range(start, end + 1, step))
        elif '-' in part:
            s, e = part.split('-')
            values.update(range(int(s), int(e) + 1))
        else:
            values.add(int(part))
    return sorted(v for v in values if min_val <= v <= max_val)


def explain_field_text(field, unit, plural, labels=None):
    if field == '*':
        return f"Jede(n) {unit}"
    parts = field.split(',')
    described = []
    for p in parts:
        if p.startswith('*/'):
            described.append(f"alle {p[2:]} {plural}")
        elif '-' in p and '/' not in p:
            a, b = p.split('-', 1)
            a_l = labels.get(a, a) if labels else a
            b_l = labels.get(b, b) if labels else b
            described.append(f"{a_l} bis {b_l}")
        elif '/' in p:
            base, step = p.split('/', 1)
            if '-' in base:
                a, b = base.split('-', 1)
                described.append(f"{a}–{b} alle {step}")
            else:
                described.append(f"ab {base} alle {step}")
        else:
            described.append(labels.get(p, p) if labels else p)
    return ', '.join(described)


def build_summary(minute, hour, day, month, weekday):
    parts = []

    if minute == '*' and hour == '*':
        parts.append("Jede Minute")
    elif minute.startswith('*/') and hour == '*':
        parts.append(f"Alle {minute[2:]} Minuten")
    elif hour != '*' and minute == '0':
        h = explain_field_text(hour, 'Stunde', 'Stunden')
        parts.append(f"Um {h}:00 Uhr")
    else:
        parts.append(f"Minute: {minute}, Stunde: {hour}")

    if weekday != '*' and day == '*':
        wd = explain_field_text(weekday, 'Wochentag', 'Wochentage', WEEKDAY_NAMES)
        parts.append(f"jeden {wd}")
    elif day != '*' and weekday == '*':
        parts.append(f"am {day}. des Monats")
    elif day != '*' and weekday != '*':
        wd = explain_field_text(weekday, 'Wochentag', 'Wochentage', WEEKDAY_NAMES)
        parts.append(f"am {day}. oder {wd}")

    if month != '*':
        m = explain_field_text(month, 'Monat', 'Monate', MONTH_NAMES)
        parts.append(f"im {m}")

    return ', '.join(parts)


def get_next_runs(minute_vals, hour_vals, day_vals, month_vals, weekday_vals):
    # cron weekday 0=Sun..6=Sat,7=Sun -> python weekday 0=Mon..6=Sun
    py_weekdays = set((wd + 6) % 7 for wd in weekday_vals)
    minute_set = set(minute_vals)
    hour_set = set(hour_vals)
    day_set = set(day_vals)
    month_set = set(month_vals)

    now = datetime.now().replace(second=0, microsecond=0) + timedelta(minutes=1)
    results = []
    current = now

    for _ in range(2 * 366 * 24 * 60):
        if len(results) >= 5:
            break
        if (current.month in month_set and
                current.day in day_set and
                current.weekday() in py_weekdays and
                current.hour in hour_set and
                current.minute in minute_set):
            results.append(current.isoformat())
        current += timedelta(minutes=1)

    return results


@cron_blueprint.route('/api/cron/explain', methods=['POST'])
def explain_cron():
    user = verify_token()
    if not user:
        return jsonify({"message": "Nicht autorisiert"}), 401
    try:
        data = request.get_json() or {}
        expression = data.get("expression", "").strip()

        fields = expression.split()
        if len(fields) != 5:
            return jsonify({"error": "Cron-Ausdruck muss genau 5 Felder haben (Minute Stunde Tag Monat Wochentag)"}), 400

        minute_f, hour_f, day_f, month_f, weekday_f = fields

        try:
            minute_vals = parse_field(minute_f, 0, 59)
            hour_vals = parse_field(hour_f, 0, 23)
            day_vals = parse_field(day_f, 1, 31)
            month_vals = parse_field(month_f, 1, 12)
            weekday_vals = parse_field(weekday_f, 0, 7)
        except (ValueError, ZeroDivisionError) as e:
            return jsonify({"error": f"Ungültiger Cron-Ausdruck: {e}"}), 400

        field_descriptions = {
            "minute": explain_field_text(minute_f, 'Minute', 'Minuten'),
            "hour": explain_field_text(hour_f, 'Stunde', 'Stunden'),
            "day": explain_field_text(day_f, 'Tag', 'Tage'),
            "month": explain_field_text(month_f, 'Monat', 'Monate', MONTH_NAMES),
            "weekday": explain_field_text(weekday_f, 'Wochentag', 'Wochentage', WEEKDAY_NAMES),
        }

        next_runs = get_next_runs(minute_vals, hour_vals, day_vals, month_vals, weekday_vals)

        return jsonify({
            "explanation": build_summary(minute_f, hour_f, day_f, month_f, weekday_f),
            "fields": field_descriptions,
            "next_runs": next_runs,
        })

    except Exception as e:
        logger.error(f"Fehler cron explain: {e}")
        return jsonify({"error": "Fehler beim Verarbeiten des Ausdrucks"}), 500