"""
Step 树 RESTful API

提供 Trace 和 Step 的查询接口，支持懒加载和 compact/full 视图
"""

from typing import List, Optional, Dict, Any
from fastapi import APIRouter, HTTPException, Query
from fastapi.responses import PlainTextResponse
from pydantic import BaseModel

from agent.execution.protocols import TraceStore


router = APIRouter(prefix="/api/traces", tags=["traces"])


# ===== Response 模型 =====


class TraceListResponse(BaseModel):
    """Trace 列表响应"""
    traces: List[Dict[str, Any]]


class TraceResponse(BaseModel):
    """Trace 元数据响应"""
    trace_id: str
    mode: str
    task: Optional[str] = None
    agent_type: Optional[str] = None
    status: str
    total_steps: int
    total_tokens: int
    total_cost: float
    created_at: str
    completed_at: Optional[str] = None


class StepNode(BaseModel):
    """Step 节点（递归结构）"""
    step_id: str
    step_type: str
    status: str
    description: str
    sequence: int
    parent_id: Optional[str] = None
    data: Optional[Dict[str, Any]] = None
    summary: Optional[str] = None
    duration_ms: Optional[int] = None
    tokens: Optional[int] = None
    cost: Optional[float] = None
    created_at: str
    children: List["StepNode"] = []


class TreeResponse(BaseModel):
    """完整树响应"""
    trace_id: str
    root_steps: List[StepNode]


class NodeResponse(BaseModel):
    """节点响应"""
    step_id: Optional[str]
    step_type: Optional[str]
    description: Optional[str]
    children: List[StepNode]


# ===== 全局 TraceStore（由 api_server.py 注入）=====


_trace_store: Optional[TraceStore] = None


def set_trace_store(store: TraceStore):
    """设置 TraceStore 实例"""
    global _trace_store
    _trace_store = store


def get_trace_store() -> TraceStore:
    """获取 TraceStore 实例"""
    if _trace_store is None:
        raise RuntimeError("TraceStore not initialized")
    return _trace_store


# ===== 路由 =====


@router.get("", response_model=TraceListResponse)
async def list_traces(
    mode: Optional[str] = None,
    agent_type: Optional[str] = None,
    uid: Optional[str] = None,
    status: Optional[str] = None,
    limit: int = Query(20, le=100)
):
    """
    列出 Traces

    Args:
        mode: 模式过滤（call/agent）
        agent_type: Agent 类型过滤
        uid: 用户 ID 过滤
        status: 状态过滤（running/completed/failed）
        limit: 最大返回数量
    """
    store = get_trace_store()
    traces = await store.list_traces(
        mode=mode,
        agent_type=agent_type,
        uid=uid,
        status=status,
        limit=limit
    )
    return TraceListResponse(
        traces=[t.to_dict() for t in traces]
    )


@router.get("/{trace_id}", response_model=TraceResponse)
async def get_trace(trace_id: str):
    """
    获取 Trace 元数据

    Args:
        trace_id: Trace ID
    """
    store = get_trace_store()
    trace = await store.get_trace(trace_id)
    if not trace:
        raise HTTPException(status_code=404, detail="Trace not found")

    return TraceResponse(**trace.to_dict())


@router.get("/{trace_id}/tree", response_model=TreeResponse)
async def get_full_tree(
    trace_id: str,
    view: str = Query("compact", regex="^(compact|full)$"),
    max_depth: int = Query(999, ge=1, le=999)
):
    """
    获取完整 Step 树（小型 Trace 推荐）

    Args:
        trace_id: Trace ID
        view: compact（默认，不含 blob）| full（含 blob）
        max_depth: 最大深度
    """
    store = get_trace_store()

    # 验证 Trace 存在
    trace = await store.get_trace(trace_id)
    if not trace:
        raise HTTPException(status_code=404, detail="Trace not found")

    # 获取所有 Steps
    steps = await store.get_trace_steps(trace_id)

    # 构建树结构
    root_nodes = await _build_tree(store, trace_id, None, view=view, expand=True, max_depth=max_depth)

    return TreeResponse(
        trace_id=trace_id,
        root_steps=root_nodes
    )


@router.get("/{trace_id}/node/{step_id}", response_model=NodeResponse)
async def get_node(
    trace_id: str,
    step_id: str,
    view: str = Query("compact", regex="^(compact|full)$"),
    expand: bool = Query(False, description="是否加载子节点"),
    max_depth: int = Query(1, ge=1, le=10, description="递归深度")
):
    """
    懒加载节点 + 子节点（大型 Trace 推荐）

    Args:
        trace_id: Trace ID
        step_id: Step ID（"null" 表示根节点）
        view: compact | full
        expand: 是否加载子节点
        max_depth: 递归深度
    """
    store = get_trace_store()

    # 验证 Trace 存在
    trace = await store.get_trace(trace_id)
    if not trace:
        raise HTTPException(status_code=404, detail="Trace not found")

    # step_id = "null" 表示根节点
    actual_step_id = None if step_id == "null" else step_id

    # 验证 Step 存在（非根节点）
    if actual_step_id:
        step = await store.get_step(actual_step_id)
        if not step or step.trace_id != trace_id:
            raise HTTPException(status_code=404, detail="Step not found")

    # 构建节点树
    children = await _build_tree(store, trace_id, actual_step_id, view=view, expand=expand, max_depth=max_depth)

    # 如果是根节点，返回所有根 Steps
    if actual_step_id is None:
        return NodeResponse(
            step_id=None,
            step_type=None,
            description=None,
            children=children
        )

    # 否则返回当前节点 + 子节点
    step = await store.get_step(actual_step_id)
    return NodeResponse(
        step_id=step.step_id,
        step_type=step.step_type,
        description=step.description,
        children=children
    )


@router.get("/{trace_id}/node/{step_id}/children")
async def get_children_paginated(
    trace_id: str,
    step_id: str,
    cursor: Optional[int] = Query(None, description="上次最后的 sequence"),
    limit: int = Query(20, ge=1, le=100),
    view: str = Query("compact", regex="^(compact|full)$")
):
    """
    分页获取子节点（基于 sequence 游标）

    Args:
        trace_id: Trace ID
        step_id: Step ID
        cursor: 上次最后的 sequence（None 表示从头开始）
        limit: 每页数量
        view: compact | full

    Returns:
        {
            "children": [...],
            "next_cursor": 123,  # 下一页游标（None 表示没有更多）
            "has_more": true
        }
    """
    store = get_trace_store()

    # 验证 trace 存在
    trace = await store.get_trace(trace_id)
    if not trace:
        raise HTTPException(status_code=404, detail="Trace not found")

    # 验证 step 存在
    step = await store.get_step(step_id)
    if not step or step.trace_id != trace_id:
        raise HTTPException(status_code=404, detail="Step not found")

    # 获取所有子节点
    children = await store.get_step_children(step_id)

    # 过滤 cursor 之后的节点
    if cursor is not None:
        children = [s for s in children if s.sequence > cursor]

    # 分页
    has_more = len(children) > limit
    page = children[:limit]
    next_cursor = page[-1].sequence if page and has_more else None

    # 序列化
    children_dicts = [s.to_dict(view=view) for s in page]

    return {
        "children": children_dicts,
        "next_cursor": next_cursor,
        "has_more": has_more
    }


# ===== 核心算法：懒加载树构建 =====


async def _build_tree(
    store: TraceStore,
    trace_id: str,
    step_id: Optional[str],
    view: str = "compact",  # 新增参数
    expand: bool = False,
    max_depth: int = 1,
    current_depth: int = 0
) -> List[StepNode]:
    """
    懒加载核心逻辑（简洁版本）

    没有"批次计算"、没有"同层完整性检查"
    只有简单的递归遍历

    Args:
        store: TraceStore 实例
        trace_id: Trace ID
        step_id: 当前 Step ID（None 表示根节点）
        view: "compact" | "full"
        expand: 是否展开子节点
        max_depth: 最大递归深度
        current_depth: 当前递归深度

    Returns:
        List[StepNode]: 节点列表
    """
    # 1. 获取当前层节点
    if step_id is None:
        # 根节点：获取所有 parent_id=None 的 Steps
        steps = await store.get_trace_steps(trace_id)
        current_nodes = [s for s in steps if s.parent_id is None]
    else:
        # 非根节点：获取子节点
        current_nodes = await store.get_step_children(step_id)

    # 2. 构建响应
    result_nodes = []
    for step in current_nodes:
        node_dict = step.to_dict(view=view)  # 使用 view 参数
        node_dict["children"] = []

        # 3. 递归加载子节点（可选）
        if expand and current_depth < max_depth:
            children = await store.get_step_children(step.step_id)
            if children:
                node_dict["children"] = await _build_tree(
                    store, trace_id, step.step_id,
                    view=view, expand=True, max_depth=max_depth,
                    current_depth=current_depth + 1
                )

        result_nodes.append(StepNode(**node_dict))

    return result_nodes