"""
Quality Filter Helper - Data Access Layer

Provides consistent quality filtering across all activity queries.
Issue: #31
"""
from typing import Optional, Dict


def get_quality_filter_sql(profile: Dict, table_alias: str = "") -> str:
    """
    Returns SQL WHERE clause fragment for quality filtering.

    Args:
        profile: User profile dict with quality_filter_level
        table_alias: Optional table alias (e.g., "a." for "a.quality_label")

    Returns:
        SQL fragment (e.g., "AND quality_label IN (...)") or empty string

    Examples:
        >>> get_quality_filter_sql({'quality_filter_level': 'all'})
        ''
        >>> get_quality_filter_sql({'quality_filter_level': 'quality'})
        "AND quality_label IN ('excellent', 'good', 'acceptable')"
        >>> get_quality_filter_sql({'quality_filter_level': 'excellent'}, 'a.')
        "AND a.quality_label = 'excellent'"
    """
    level = profile.get('quality_filter_level', 'all')
    prefix = table_alias if table_alias else ""

    if level == 'all':
        return ''  # No filter
    elif level == 'quality':
        return f"AND {prefix}quality_label IN ('excellent', 'good', 'acceptable')"
    elif level == 'very_good':
        return f"AND {prefix}quality_label IN ('excellent', 'good')"
    elif level == 'excellent':
        return f"AND {prefix}quality_label = 'excellent'"
    else:
        # Unknown level → no filter (safe fallback)
        return ''


def get_quality_filter_tuple(profile: Dict) -> tuple:
    """
    Returns tuple of allowed quality labels for Python filtering.

    Args:
        profile: User profile dict with quality_filter_level

    Returns:
        Tuple of allowed quality labels or None (no filter)

    Examples:
        >>> get_quality_filter_tuple({'quality_filter_level': 'all'})
        None
        >>> get_quality_filter_tuple({'quality_filter_level': 'quality'})
        ('excellent', 'good', 'acceptable')
    """
    level = profile.get('quality_filter_level', 'all')

    if level == 'all':
        return None  # No filter
    elif level == 'quality':
        return ('excellent', 'good', 'acceptable')
    elif level == 'very_good':
        return ('excellent', 'good')
    elif level == 'excellent':
        return ('excellent',)
    else:
        return None  # Unknown level → no filter


def filter_activities_by_quality(activities: list, profile: Dict) -> list:
    """
    Filters a list of activity dicts by quality_label.

    Useful for post-query filtering (e.g., when data already loaded).

    Args:
        activities: List of activity dicts with quality_label field
        profile: User profile dict with quality_filter_level

    Returns:
        Filtered list of activities
    """
    allowed_labels = get_quality_filter_tuple(profile)

    if allowed_labels is None:
        return activities  # No filter

    return [
        act for act in activities
        if act.get('quality_label') in allowed_labels
    ]


# Constants for frontend/documentation
QUALITY_LEVELS = {
    'all': {
        'label': 'Alle',
        'icon': '📊',
        'description': 'Alle Activities (kein Filter)',
        'includes': None
    },
    'quality': {
        'label': 'Hochwertig',
        'icon': '✓',
        'description': 'Hochwertige Activities',
        'includes': ['excellent', 'good', 'acceptable']
    },
    'very_good': {
        'label': 'Sehr gut',
        'icon': '✓✓',
        'description': 'Sehr gute Activities',
        'includes': ['excellent', 'good']
    },
    'excellent': {
        'label': 'Exzellent',
        'icon': '⭐',
        'description': 'Nur exzellente Activities',
        'includes': ['excellent']
    }
}