from __future__ import annotations

import uuid

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.api_endpoint_permission import ApiEndpointPermission
from app.models.study import Study
from app.core.api_permissions import API_ENDPOINT_PERMISSIONS, OPERATION_PREREQUISITES, PROJECT_PERMISSION_ROLES
from app.core.permission_cache import get_permission_cache


async def _get_project_permission_overrides(
    db: AsyncSession,
    study_id: uuid.UUID,
) -> dict[str, dict[str, bool]]:
    cache = get_permission_cache()
    cached_permissions = cache.get_project_permissions(study_id)
    from app.core.permission_monitor import get_permission_monitor

    monitor = get_permission_monitor()
    if cached_permissions is not None:
        monitor.record_cache_hit()
        return cached_permissions

    monitor.record_cache_miss()
    result = await db.execute(
        select(ApiEndpointPermission).where(
            ApiEndpointPermission.study_id == study_id,
        )
    )
    rows = result.scalars().all()

    permissions: dict[str, dict[str, bool]] = {}
    for row in rows:
        permissions.setdefault(row.role, {})[row.endpoint_key] = row.allowed

    cache.set_project_permissions(study_id, permissions)
    return permissions


async def role_has_api_permission(
    db: AsyncSession,
    study_id: uuid.UUID,
    role: str | None,
    endpoint_key: str,
    check_prerequisites: bool = True,
) -> bool:
    """检查角色是否有权访问特定接口"""
    if endpoint_key not in API_ENDPOINT_PERMISSIONS:
        return False

    if role == "ADMIN":
        return True

    permissions = await _get_project_permission_overrides(db, study_id)

    if role == "PM":
        override = permissions.get("PM", {}).get(endpoint_key)
        if override is not None:
            return override
        return True

    allowed = permissions.get(role or "", {}).get(endpoint_key)
    if allowed is None:
        config = API_ENDPOINT_PERMISSIONS.get(endpoint_key)
        allowed = bool(config and role in config.get("default_roles", []))

    if not allowed:
        return False

    if check_prerequisites:
        prerequisites = OPERATION_PREREQUISITES.get(endpoint_key, [])
        for prereq_endpoint in prerequisites:
            has_prereq = await role_has_api_permission(
                db, study_id, role, prereq_endpoint, check_prerequisites=False
            )
            if not has_prereq:
                return False

    return True


async def get_missing_prerequisites(
    db: AsyncSession,
    study_id: uuid.UUID,
    role: str | None,
    endpoint_key: str,
) -> list[str]:
    """获取缺失的前置权限列表"""
    if role == "ADMIN":
        return []

    missing = []
    prerequisites = OPERATION_PREREQUISITES.get(endpoint_key, [])
    for prereq_endpoint in prerequisites:
        has_prereq = await role_has_api_permission(
            db, study_id, role, prereq_endpoint, check_prerequisites=False
        )
        if not has_prereq:
            missing.append(prereq_endpoint)

    return missing


async def get_api_endpoint_permissions(
    db: AsyncSession,
    study_id: uuid.UUID,
) -> dict[str, dict[str, dict[str, bool]]]:
    """获取项目的接口级权限矩阵

    返回格式: {role: {endpoint_key: {allowed: bool}}}
    """
    overrides = await _get_project_permission_overrides(db, study_id)

    study_result = await db.execute(select(Study).where(Study.id == study_id))
    study = study_result.scalar_one_or_none()
    active_roles = [role for role in (study.active_roles if study else []) if isinstance(role, str) and role.strip()]
    roles = list(dict.fromkeys([*PROJECT_PERMISSION_ROLES, *active_roles, *overrides.keys()]))
    matrix: dict[str, dict[str, dict[str, bool]]] = {}
    for role in roles:
        matrix[role] = {}
        for endpoint_key, config in API_ENDPOINT_PERMISSIONS.items():
            if role == "PM":
                matrix[role][endpoint_key] = {"allowed": True}
            else:
                default_allowed = role in config.get("default_roles", [])
                matrix[role][endpoint_key] = {"allowed": default_allowed}

    for role, endpoints in overrides.items():
        if role not in matrix:
            matrix[role] = {}
        for endpoint_key, allowed in endpoints.items():
            if endpoint_key not in API_ENDPOINT_PERMISSIONS:
                continue
            matrix[role][endpoint_key] = {"allowed": allowed}

    return matrix


async def replace_api_endpoint_permissions(
    db: AsyncSession,
    study_id: uuid.UUID,
    payload: dict[str, dict[str, bool]],
) -> dict[str, dict[str, dict[str, bool]]]:
    """更新 payload 中指定的角色权限项。未提交的权限项保持不变。

    ADMIN 与 PM 权限不会被持久化：ADMIN 始终拥有全部权限，PM 默认拥有
    全部项目权限，应当通过专门的渠道而不是项目权限矩阵调整。
    """
    for role, endpoints in payload.items():
        if role in ("ADMIN", "PM"):
            continue
        for endpoint_key, allowed in endpoints.items():
            if endpoint_key not in API_ENDPOINT_PERMISSIONS:
                continue
            result = await db.execute(
                select(ApiEndpointPermission).where(
                    ApiEndpointPermission.study_id == study_id,
                    ApiEndpointPermission.role == role,
                    ApiEndpointPermission.endpoint_key == endpoint_key,
                )
            )
            existing = result.scalar_one_or_none()
            if existing:
                existing.allowed = allowed
            else:
                db.add(
                    ApiEndpointPermission(
                        study_id=study_id,
                        role=role,
                        endpoint_key=endpoint_key,
                        allowed=allowed,
                    )
                )

    await db.commit()

    cache = get_permission_cache()
    cache.invalidate_project_permissions(study_id)
    cache.invalidate_all_member_roles(study_id)
    from app.core.permission_monitor import get_permission_monitor

    get_permission_monitor().record_cache_invalidation()

    return await get_api_endpoint_permissions(db, study_id)