from datetime import datetime
import re
import os

def extract_date_from_string(string_with_date):
    # grab X.Y.Z where X,Y,Z are 1–4 digits
    m = re.search(r'(\d{1,4}\.\d{1,2}\.\d{1,4})', string_with_date)
    if not m:
        return None

    date_str = m.group(1)
    parts = date_str.split('.')
    
    # 1) Unambiguous “last group = YYYY”
    if len(parts) == 3 and len(parts[2]) == 4:
        fmt = '%d.%m.%Y'

    # 2) Unambiguous “first group = YYYY”
    elif len(parts) == 3 and len(parts[0]) == 4:
        fmt = '%Y.%m.%d'

    # 3) Ambiguous “XX.XX.XX” → prefer DD.MM.YY, fallback to YY.MM.DD
    elif len(parts) == 3 and all(len(p) == 2 for p in parts):
        # try last-group-as-year first
        try:
            dt = datetime.strptime(date_str, '%d.%m.%y')
            return dt.strftime('%Y-%m-%d')
        except ValueError:
            # fallback to first-group-as-year
            fmt = '%y.%m.%d'

    else:
        # optional: handle ISO with dashes
        if '-' in date_str:
            try:
                dt = datetime.strptime(date_str, '%Y-%m-%d')
                return dt.strftime('%Y-%m-%d')
            except ValueError:
                return None
        return None

    # parse with whichever fmt we settled on
    try:
        dt = datetime.strptime(date_str, fmt)
        return dt.strftime('%Y-%m-%d')
    except ValueError:
        return None


def extract_structure_from_string(input_string):
    # extract category and titel from filename
    filename_ext = os.path.splitext(input_string)[0]
    left_side, right_side = filename_ext.split('-', 1) if '-' in filename_ext else (filename_ext, None)
    try:
        int(left_side.strip())
        # first part is only a number
        previous_right_side = right_side
        left_side, right_side = previous_right_side.split('-', 1) if '-' in previous_right_side else (previous_right_side, None)
    except:
        # first part not a number
        pass
    
    if 'predig' in left_side.lower():
        category = 'Predigt'
    elif 'wort' in left_side.lower() or 'einladung' in left_side.lower():
        category = 'Vorwort'
    elif 'chor' in left_side.lower():
        category = 'Chor'
    elif 'orchester' in left_side.lower():
        category = 'Orchester'
    elif 'gruppenlied' in left_side.lower() or 'jugendlied' in left_side.lower():
        category = 'Gruppenlied'
    elif 'gemeinsam' in left_side.lower() or 'gesang' in left_side.lower() or 'lied' in left_side.lower():
        category = 'Gemeinsamer Gesang'
    elif 'gedicht' in left_side.lower():
        category = 'Gedicht'
    elif 'instrumental' in left_side.lower() or 'musikstück' in left_side.lower():
        category = 'Instrumental'
    else:
        category = None

    if right_side:
        titel, name = right_side.split('-', 1) if '-' in right_side else (right_side, None)
        if category == 'Predigt' or category == 'Vorwort' or category == 'Gedicht':
            if not name: # kein Titel, nur Name
                name = titel
                titel = None
    else:
        titel = None
        name = None

    return category, titel, name