from flask import Blueprint, request, jsonify, render_template, session
from app.models import db, Goal, StudentGoal, GoalRelation, StudentGoalEvaluation
from app.routes.auth import login_required_json, admin_required, login_required
from app.routes import main_bp

goals_bp = Blueprint("goals", __name__)

# 目标管理页面路由
@main_bp.route("/goals")
@login_required
def goals_page():
    """目标管理页面"""
    return render_template("goals.html", active_nav="goals")

@goals_bp.route("/api/goals", methods=["GET"])
@login_required_json
def get_goals():
    goals = Goal.query.order_by(Goal.created_at.desc()).all()
    return jsonify([g.to_dict() for g in goals])

@goals_bp.route("/api/goals", methods=["POST"])
@login_required_json
def create_goal():
    data = request.get_json()
    goal = Goal(
        name=data["name"],
        content=data.get("content", ""),
        level=data.get("level", "入门"),
        category=data.get("category", "综合")
    )
    db.session.add(goal)
    db.session.commit()
    return jsonify(goal.to_dict()), 201

@goals_bp.route("/api/goals/<int:goal_id>", methods=["GET"])
@login_required_json
def get_goal(goal_id):
    goal = Goal.query.get_or_404(goal_id)
    return jsonify(goal.to_dict())

@goals_bp.route("/api/goals/<int:goal_id>", methods=["PUT"])
@login_required_json
def update_goal(goal_id):
    goal = Goal.query.get_or_404(goal_id)
    data = request.get_json()
    if "name" in data:
        goal.name = data["name"]
    if "content" in data:
        goal.content = data["content"]
    if "level" in data:
        goal.level = data["level"]
    if "category" in data:
        goal.category = data["category"]
    db.session.commit()
    return jsonify(goal.to_dict())

@goals_bp.route("/api/goals/<int:goal_id>", methods=["DELETE"])
@login_required_json
def delete_goal(goal_id):
    """删除目标模板（仅管理员，需检查依赖）"""
    from app.models import User
    user = User.query.get(session.get("user_id"))
    if not user or user.role != "admin":
        return jsonify({"error": "权限不足，仅管理员可操作"}), 403

    goal = Goal.query.get_or_404(goal_id)

    # 检查依赖关系
    deps = []

    # 1. 检查是否有学员分配了此目标
    student_goal_count = StudentGoal.query.filter_by(goal_id=goal_id).count()
    if student_goal_count > 0:
        deps.append(f"已被 {student_goal_count} 名学员分配")

    # 2. 检查是否有目标关联（作为父目标或子目标）
    as_parent = GoalRelation.query.filter_by(parent_goal_id=goal_id).count()
    as_child = GoalRelation.query.filter_by(child_goal_id=goal_id).count()
    if as_parent > 0:
        deps.append(f"有 {as_parent} 个子目标关联")
    if as_child > 0:
        deps.append(f"作为子目标被 {as_child} 个目标引用")

    if deps:
        return jsonify({"error": f"无法删除：{', '.join(deps)}"}), 400

    db.session.delete(goal)
    db.session.commit()
    return jsonify({"message": "删除成功"})

# ===== 以下是 Task 3 的循环检测和关联 API =====

def _has_cycle(parent_id, child_id):
    """检测添加 child_id 作为 parent_id 的子目标是否会形成循环"""
    visited = set()
    stack = [child_id]
    while stack:
        current = stack.pop()
        if current == parent_id:
            return True
        if current in visited:
            continue
        visited.add(current)
        from app.models import GoalRelation
        for rel in GoalRelation.query.filter_by(parent_goal_id=current).all():
            stack.append(rel.child_goal_id)
    return False

@goals_bp.route("/api/goals/<int:goal_id>/children", methods=["GET"])
@login_required_json
def get_goal_children(goal_id):
    from app.models import GoalRelation
    relations = GoalRelation.query.filter_by(parent_goal_id=goal_id).all()
    child_ids = [r.child_goal_id for r in relations]
    children = Goal.query.filter(Goal.id.in_(child_ids)).all() if child_ids else []
    return jsonify([c.to_dict() for c in children])

@goals_bp.route("/api/goals/<int:goal_id>/parents", methods=["GET"])
@login_required_json
def get_goal_parents(goal_id):
    from app.models import GoalRelation
    relations = GoalRelation.query.filter_by(child_goal_id=goal_id).all()
    parent_ids = [r.parent_goal_id for r in relations]
    parents = Goal.query.filter(Goal.id.in_(parent_ids)).all() if parent_ids else []
    return jsonify([p.to_dict() for p in parents])

@goals_bp.route("/api/goals/<int:goal_id>/children", methods=["POST"])
@login_required_json
def add_goal_child(goal_id):
    from app.models import GoalRelation
    data = request.get_json()
    child_id = data["child_goal_id"]

    if goal_id == child_id:
        return jsonify({"error": "不能将目标关联到自身"}), 400

    if _has_cycle(goal_id, child_id):
        return jsonify({"error": "添加此关联会形成循环引用"}), 400

    existing = GoalRelation.query.filter_by(parent_goal_id=goal_id, child_goal_id=child_id).first()
    if existing:
        return jsonify({"error": "关联已存在"}), 400

    relation = GoalRelation(parent_goal_id=goal_id, child_goal_id=child_id)
    db.session.add(relation)
    db.session.commit()
    return jsonify({"message": "添加成功"})

@goals_bp.route("/api/goals/<int:goal_id>/children/<int:child_id>", methods=["DELETE"])
@login_required_json
def remove_goal_child(goal_id, child_id):
    from app.models import GoalRelation
    relation = GoalRelation.query.filter_by(parent_goal_id=goal_id, child_goal_id=child_id).first()
    if relation:
        db.session.delete(relation)
        db.session.commit()
    return jsonify({"message": "移除成功"})