"""Ранги, редкость и журнал опыта навыков сотрудников."""

from __future__ import annotations

from datetime import timedelta

from django.db import transaction
from django.db.models import Count, Q, Sum
from django.utils import timezone

from employees.models import (
    Department,
    Employee,
    EmployeeDepartment,
    EmployeeSkillProgress,
    RoleAssignment,
    Skill,
    SkillExperienceEvent,
)


SKILL_RANKS = (
    {"code": "none", "label": "Без ранга", "threshold": 0},
    {"code": "bronze", "label": "Бронза", "threshold": 100},
    {"code": "silver", "label": "Серебро", "threshold": 300},
    {"code": "gold", "label": "Золото", "threshold": 800},
    {"code": "ruby", "label": "Рубин", "threshold": 1800},
    {"code": "diamond", "label": "Бриллиант", "threshold": 4000},
)

ENDORSEMENT_COOLDOWN_DAYS = 90
TASK_SKILL_EXPERIENCE = 25


def skill_queryset_with_rarity(queryset=None):
    queryset = queryset if queryset is not None else Skill.objects.all()
    return queryset.annotate(
        confirmed_holders=Count(
            "employee_progresses",
            filter=Q(
                employee_progresses__is_active=True,
                employee_progresses__experience__gte=100,
                employee_progresses__employee__is_active=True,
                employee_progresses__employee__is_hidden_in_ui=False,
            ),
            distinct=True,
        )
    )


def rank_payload(experience: int) -> dict:
    experience = max(int(experience or 0), 0)
    current = SKILL_RANKS[0]
    next_rank = None
    for index, rank in enumerate(SKILL_RANKS):
        if experience >= rank["threshold"]:
            current = rank
            next_rank = SKILL_RANKS[index + 1] if index + 1 < len(SKILL_RANKS) else None
        else:
            break

    current_threshold = int(current["threshold"])
    next_threshold = int(next_rank["threshold"]) if next_rank else None
    if next_threshold is None:
        percent = 100
        remaining = 0
    else:
        span = max(next_threshold - current_threshold, 1)
        percent = round(min(max((experience - current_threshold) / span, 0), 1) * 100)
        remaining = max(next_threshold - experience, 0)

    return {
        "rank": current["code"],
        "rank_display": current["label"],
        "rank_threshold": current_threshold,
        "next_rank": next_rank["code"] if next_rank else None,
        "next_rank_display": next_rank["label"] if next_rank else None,
        "next_rank_experience": next_threshold,
        "experience_to_next_rank": remaining,
        "rank_progress_percent": percent,
    }


def rarity_payload(confirmed_holders: int) -> dict:
    count = max(int(confirmed_holders or 0), 0)
    if count == 0:
        code, label = "unrated", "Не определена"
    elif count == 1:
        code, label = "legendary", "Легендарный"
    elif count <= 3:
        code, label = "epic", "Эпический"
    elif count <= 9:
        code, label = "rare", "Редкий"
    elif count <= 24:
        code, label = "uncommon", "Необычный"
    else:
        code, label = "common", "Обычный"
    return {
        "confirmed_holders": count,
        "rarity": code,
        "rarity_display": label,
    }


def confirmed_holder_count(skill: Skill) -> int:
    return (
        EmployeeSkillProgress.objects.filter(
            skill=skill,
            is_active=True,
            experience__gte=100,
            employee__is_active=True,
            employee__is_hidden_in_ui=False,
            employee__skills=skill,
        )
        .distinct()
        .count()
    )


def ensure_skill_progress(
    employee: Employee,
    skill: Skill,
    *,
    created_by: Employee | None = None,
) -> EmployeeSkillProgress:
    progress, created = EmployeeSkillProgress.objects.get_or_create(
        employee=employee,
        skill=skill,
        defaults={"created_by": created_by, "is_active": True},
    )
    update_fields = []
    if not progress.is_active:
        progress.is_active = True
        update_fields.append("is_active")
    if created_by and progress.created_by_id is None:
        progress.created_by = created_by
        update_fields.append("created_by")
    if update_fields:
        update_fields.append("updated_at")
        progress.save(update_fields=update_fields)
    if created:
        employee.skills.add(skill)
    return progress


@transaction.atomic
def record_skill_experience(
    *,
    employee: Employee,
    skill: Skill,
    points: int,
    source_type: str,
    actor: Employee | None,
    reason: str,
    source_id: str = "",
    idempotency_key: str = "",
    metadata: dict | None = None,
) -> tuple[EmployeeSkillProgress, SkillExperienceEvent, bool]:
    points = int(points)
    if points <= 0:
        raise ValueError("Баллы опыта должны быть положительным числом")

    progress = ensure_skill_progress(employee, skill, created_by=actor)
    progress = EmployeeSkillProgress.objects.select_for_update().get(pk=progress.pk)

    existing = None
    if idempotency_key:
        existing = SkillExperienceEvent.objects.filter(
            idempotency_key=idempotency_key
        ).first()
    if existing:
        if existing.revoked_at is not None:
            existing.revoked_at = None
            existing.revoked_by = None
            existing.save(update_fields=["revoked_at", "revoked_by"])
            progress.experience += existing.points
            progress.save(update_fields=["experience", "updated_at"])
        return progress, existing, False

    event = SkillExperienceEvent.objects.create(
        progress=progress,
        points=points,
        source_type=source_type,
        source_id=str(source_id or ""),
        actor=actor,
        reason=reason,
        metadata=metadata or {},
        idempotency_key=idempotency_key,
    )
    progress.experience += points
    progress.save(update_fields=["experience", "updated_at"])
    return progress, event, True


@transaction.atomic
def revoke_skill_experience_event(
    event: SkillExperienceEvent,
    *,
    actor: Employee | None = None,
) -> EmployeeSkillProgress:
    event = SkillExperienceEvent.objects.select_for_update().get(pk=event.pk)
    progress = EmployeeSkillProgress.objects.select_for_update().get(
        pk=event.progress_id
    )
    if event.revoked_at is not None:
        return progress
    event.revoked_at = timezone.now()
    event.revoked_by = actor
    event.save(update_fields=["revoked_at", "revoked_by"])
    progress.experience = max(progress.experience - event.points, 0)
    progress.save(update_fields=["experience", "updated_at"])
    return progress


def recalculate_skill_progress(progress: EmployeeSkillProgress) -> int:
    total = (
        progress.experience_events.filter(revoked_at__isnull=True).aggregate(
            total=Sum("points")
        )["total"]
        or 0
    )
    if progress.experience != total:
        progress.experience = total
        progress.save(update_fields=["experience", "updated_at"])
    return total


def endorsement_weight(actor: Employee, target: Employee) -> tuple[int, str]:
    target_department_ids = EmployeeDepartment.objects.filter(
        employee=target,
        is_active=True,
    ).values_list("department_id", flat=True)
    if Department.objects.filter(
        id__in=target_department_ids,
        head=actor,
    ).exists():
        return 15, "Руководитель отдела"
    if RoleAssignment.objects.filter(
        employee=actor,
        role__department_id__in=target_department_ids,
        is_active=True,
    ).exists():
        return 10, "Роль в отделе"
    return 5, "Коллега"


def endorsement_available_at(
    *,
    progress: EmployeeSkillProgress,
    actor: Employee,
):
    latest = (
        progress.experience_events.filter(
            source_type=SkillExperienceEvent.Source.ENDORSEMENT,
            actor=actor,
            revoked_at__isnull=True,
        )
        .order_by("-created_at")
        .first()
    )
    if latest is None:
        return None
    available_at = latest.created_at + timedelta(days=ENDORSEMENT_COOLDOWN_DAYS)
    return available_at if available_at > timezone.now() else None


def award_task_skill_experience(task_id: int) -> int:
    """Начисляет опыт исполнителю и участникам завершённой задачи.

    Баллы получают только сотрудники, у которых навык уже добавлен в профиль.
    Идемпотентный ключ исключает повторное начисление после повторного save().
    """

    from tasks.models import Task

    task = (
        Task.objects.select_related("assignee")
        .prefetch_related("participants", "skills")
        .filter(pk=task_id, completed_at__isnull=False)
        .first()
    )
    if task is None:
        return 0

    employee_ids = set(task.participants.values_list("id", flat=True))
    if task.assignee_id:
        employee_ids.add(task.assignee_id)
    if not employee_ids:
        return 0

    awarded = 0
    for skill in task.skills.all():
        recipients = Employee.objects.filter(
            id__in=employee_ids,
            is_active=True,
            skills=skill,
        ).distinct()
        for employee in recipients:
            _, _, created = record_skill_experience(
                employee=employee,
                skill=skill,
                points=TASK_SKILL_EXPERIENCE,
                source_type=SkillExperienceEvent.Source.TASK,
                actor=task.created_by,
                source_id=str(task.id),
                reason=f"Завершена задача «{task.title}»",
                idempotency_key=(
                    f"task:{task.id}:employee:{employee.id}:skill:{skill.id}"
                ),
                metadata={"task_id": task.id, "task_title": task.title},
            )
            awarded += int(created)
    return awarded


def revoke_task_skill_experience(task_id: int, *, actor: Employee | None = None) -> int:
    events = SkillExperienceEvent.objects.filter(
        source_type=SkillExperienceEvent.Source.TASK,
        source_id=str(task_id),
        revoked_at__isnull=True,
    )
    revoked = 0
    for event in events:
        revoke_skill_experience_event(event, actor=actor)
        revoked += 1
    return revoked