from __future__ import annotations

from collections import defaultdict
from datetime import date, timedelta

from ..models import BadgeDefinition, TaskInstance


def _max_day_streak(days: set[date]) -> int:
    if not days:
        return 0
    streak = 1
    best = 1
    ordered = sorted(days)
    for previous, current in zip(ordered, ordered[1:]):
        if current == previous + timedelta(days=1):
            streak += 1
        else:
            streak = 1
        best = max(best, streak)
    return best


def compute_badge_awards(definitions: list[BadgeDefinition], completed_tasks: list[TaskInstance]) -> list[dict]:
    by_type: dict[str, int] = defaultdict(int)
    completion_days: set[date] = set()

    for task in completed_tasks:
        if not task.completed_at:
            continue
        completion_day = task.completed_at.date()
        completion_days.add(completion_day)
        by_type["monthly_task_count"] += 1
        if task.due_date and completion_day < task.due_date:
            by_type["early_finisher_count"] += 1
        if task.due_date and completion_day <= task.due_date:
            by_type["on_time_count"] += 1

    by_type["streak_days"] = _max_day_streak(completion_days)

    awards = []
    for definition in definitions:
        metric_value = by_type.get(definition.trigger_type, 0)
        if definition.active and metric_value >= definition.threshold:
            awards.append(
                {
                    "definition": definition,
                    "metric_value": metric_value,
                    "bonus_points": definition.bonus_points,
                }
            )
    return awards