from __future__ import annotations

import logging
import time
import uuid
from collections.abc import Iterable, Mapping
from contextvars import ContextVar
from contextlib import asynccontextmanager
from dataclasses import asdict, is_dataclass
from functools import wraps
from inspect import isawaitable
from typing import Any

from fastapi import FastAPI, Request
from fastapi.dependencies.utils import (
    _should_embed_body_fields,
    get_body_field,
    get_dependant,
    get_flat_dependant,
    get_parameterless_sub_dependant,
)
from fastapi.exceptions import RequestValidationError
from fastapi.middleware.cors import CORSMiddleware
from fastapi.routing import APIRoute
from fastapi.routing import request_response
from fastapi.responses import JSONResponse
from pydantic import BaseModel
from starlette.responses import Response
from sqlalchemy.exc import SQLAlchemyError

from iti.auth.permissions import StaticPermissionProvider
from iti.audit import init_audit
from iti.cache import CacheManager
from iti.config import BaseConfig, get_config
from iti.db import configure_db
from iti.exceptions import ItiError
from iti.health import router as health_router
from iti.limiter import SimpleLimiter
from iti.logging_config import configure_logging, log_extra
from iti.modules import init_modules
from iti.responses.auto import is_envelope_payload, is_raw_response_request
from iti.responses import fail
from iti.service_client import init_service_clients
from iti.tasks import init_task_runner

logger = logging.getLogger("iti")
error_logger = logging.getLogger("iti.error")
_current_request: ContextVar[Request | None] = ContextVar("iti_current_request", default=None)


def create_app(
    config_name: str | None = None,
    *,
    modules: Iterable[Any] | None = None,
    config_mapping: Mapping[str, type[BaseConfig] | BaseConfig] | type[BaseConfig] | BaseConfig | None = None,
    permission_provider: Any | None = None,
) -> FastAPI:
    config = _resolve_config(config_name, config_mapping)
    configure_logging(config)

    @asynccontextmanager
    async def lifespan(app: FastAPI):
        runner = getattr(app.state, "iti_task_runner", None)
        audit_dispatcher = getattr(app.state, "audit_dispatcher", None)
        if audit_dispatcher:
            audit_dispatcher.start()
        if runner and config.tasks_enabled:
            runner.start()
        yield
        if runner:
            runner.stop()
        if audit_dispatcher:
            audit_dispatcher.stop()
        for client in getattr(app.state, "iti_service_clients", {}).values():
            client.close()

    app = FastAPI(
        title=config.app_name,
        debug=config.debug,
        lifespan=lifespan,
    )
    app.state.config = config
    app.state.cache = CacheManager(default_timeout=config.cache_default_timeout)
    app.state.limiter = SimpleLimiter(enabled=config.ratelimit_enabled)
    app.state.permission_provider = permission_provider or StaticPermissionProvider()

    init_middlewares(app)

    if config.cors_origins:
        app.add_middleware(
            CORSMiddleware,
            allow_origins=config.cors_origins,
            allow_credentials=True,
            allow_methods=["*"],
            allow_headers=["*"],
        )

    engine, sessionmaker = configure_db(
        config.database_url,
        echo=config.sqlalchemy_echo,
        pool_pre_ping=config.sqlalchemy_pool_pre_ping,
    )
    app.state.db_engine = engine
    app.state.db_sessionmaker = sessionmaker

    init_error_handlers(app)
    init_service_clients(app, config.services)
    init_task_runner(app)
    init_audit(app)
    module_registry = init_modules(app, modules)
    app.state.iti_modules = module_registry
    if config.health_enabled:
        app.include_router(health_router)
    module_registry.run_phase("register_routes", app)
    module_registry.run_phase("register_permissions", app)
    module_registry.run_phase("register_menu_seed", app)
    install_auto_envelope(app)
    return app


def init_middlewares(app: FastAPI) -> None:
    @app.middleware("http")
    async def request_context_middleware(request: Request, call_next):
        token = _current_request.set(request)
        trace_id = request.headers.get("X-Trace-Id") or uuid.uuid4().hex
        request_id = request.headers.get("X-Request-Id") or uuid.uuid4().hex
        request.state.trace_id = trace_id
        request.state.request_id = request_id
        started_at = time.perf_counter()
        response: Response | None
        try:
            response = await call_next(request)
        except Exception:
            request.state.response_code = getattr(request.state, "response_code", 500)
            _log_request(request, started_at, 500)
            _current_request.reset(token)
            raise
        response.headers.setdefault("X-Trace-Id", trace_id)
        response.headers.setdefault("X-Request-Id", request_id)
        _log_request(request, started_at, response.status_code)
        _current_request.reset(token)
        return response


def _log_request(request: Request, started_at: float, status_code: int) -> None:
    duration_ms = round((time.perf_counter() - started_at) * 1000, 2)
    logger.info(
        "request method=%s path=%s status=%s code=%s durationMs=%s ip=%s",
        request.method,
        request.url.path,
        status_code,
        getattr(request.state, "response_code", "-"),
        duration_ms,
        request.client.host if request.client else "-",
        extra=log_extra(request),
    )


def _resolve_config(
    config_name: str | None,
    config_mapping: Mapping[str, type[BaseConfig] | BaseConfig] | type[BaseConfig] | BaseConfig | None,
) -> BaseConfig:
    if config_mapping is None:
        return get_config(config_name)
    if isinstance(config_mapping, Mapping):
        env_name = config_name or "dev"
        value = config_mapping.get(env_name, config_mapping.get("default"))
        if value is None:
            return get_config(config_name)
        return value() if isinstance(value, type) else value
    return config_mapping() if isinstance(config_mapping, type) else config_mapping


def init_error_handlers(app: FastAPI) -> None:
    @app.exception_handler(ItiError)
    async def handle_iti_error(request: Request, exc: ItiError):
        request.state.response_code = exc.code
        return JSONResponse(
            status_code=request.app.state.config.response_envelope_http_status,
            content=fail(exc.message, code=exc.code, data=exc.data),
        )

    @app.exception_handler(RequestValidationError)
    async def handle_validation_error(request: Request, exc: RequestValidationError):
        request.state.response_code = 422
        return JSONResponse(
            status_code=request.app.state.config.response_envelope_http_status,
            content=fail("参数验证错误", code=422, data=exc.errors()),
        )

    @app.exception_handler(SQLAlchemyError)
    async def handle_db_error(request: Request, exc: SQLAlchemyError):
        request.state.response_code = 500
        error_logger.exception("database error", extra=log_extra(request))
        return JSONResponse(
            status_code=request.app.state.config.response_envelope_http_status,
            content=fail("数据库错误", code=500, data=str(exc)),
        )

    @app.exception_handler(Exception)
    async def handle_exception(request: Request, exc: Exception):
        request.state.response_code = 500
        error_logger.exception("server error", extra=log_extra(request))
        return JSONResponse(
            status_code=request.app.state.config.response_envelope_http_status,
            content=fail("服务器错误", code=500, data=str(exc)),
        )


def to_plain_data(value: Any) -> Any:
    if is_dataclass(value):
        return asdict(value)
    return value


def install_auto_envelope(app: FastAPI) -> None:
    config = app.state.config
    if not config.response_envelope_enabled:
        return
    raw_paths = tuple(config.raw_response_paths)
    for route in app.routes:
        if not isinstance(route, APIRoute):
            continue
        if getattr(route, "__iti_envelope_installed__", False):
            continue
        if _is_route_raw(route, raw_paths):
            continue
        original_call = route.dependant.call
        if original_call is None:
            continue
        route.endpoint = _wrap_endpoint_with_envelope(original_call)
        _rebuild_route_dependant(route)
        setattr(route, "__iti_envelope_installed__", True)


def _is_route_raw(route: APIRoute, raw_paths: Iterable[str]) -> bool:
    endpoint = route.endpoint
    if getattr(endpoint, "__iti_raw_response__", False):
        return True
    for path in route.path_format, route.path:
        request = _PathOnlyRequest(path)
        if is_raw_response_request(request, raw_paths):
            return True
    return False


def _wrap_endpoint_with_envelope(func):
    @wraps(func)
    async def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        if isawaitable(result):
            result = await result
        if isinstance(result, Response):
            return result
        payload = _to_jsonable(result)
        if is_envelope_payload(payload):
            _mark_response_code(args, kwargs, payload["code"])
            return payload
        _mark_response_code(args, kwargs, 200)
        return {"data": payload, "code": 200, "message": "成功"}

    return wrapper


def _to_jsonable(value: Any) -> Any:
    if value is None:
        return None
    if isinstance(value, BaseModel):
        return value.model_dump(by_alias=True)
    if is_dataclass(value):
        return asdict(value)
    return value


def _mark_response_code(args: tuple[Any, ...], kwargs: dict[str, Any], code: int) -> None:
    request = _request_from_call(args, kwargs) or _current_request.get()
    if request is not None:
        request.state.response_code = code


def _request_from_call(args: tuple[Any, ...], kwargs: dict[str, Any]) -> Request | None:
    for value in list(args) + list(kwargs.values()):
        if isinstance(value, Request):
            return value
    return None


def _rebuild_route_dependant(route: APIRoute) -> None:
    route.dependant = get_dependant(
        path=route.path_format,
        call=route.endpoint,
        scope="function",
    )
    for depends in route.dependencies[::-1]:
        route.dependant.dependencies.insert(
            0,
            get_parameterless_sub_dependant(depends=depends, path=route.path_format),
        )
    route._flat_dependant = get_flat_dependant(route.dependant)
    route._embed_body_fields = _should_embed_body_fields(route._flat_dependant.body_params)
    route.body_field = get_body_field(
        flat_dependant=route._flat_dependant,
        name=route.unique_id,
        embed_body_fields=route._embed_body_fields,
    )
    route.app = request_response(route.get_route_handler())


class _PathOnlyRequest:
    def __init__(self, path: str) -> None:
        self.url = type("URL", (), {"path": path})()
        self.scope = {"endpoint": None}