use std::{fs, path::Path, sync::Arc};

use axum::{
    extract::State,
    http::{HeaderMap, StatusCode},
};
use base64::{Engine as _, engine::general_purpose::STANDARD as BASE64_STANDARD};
use bytes::Bytes;
use ring::{
    aead,
    rand::{SecureRandom, SystemRandom},
    signature,
};
use serde::{Deserialize, Serialize};
use serde_json::{Value, json};
use sha2::{Digest, Sha256};
use shared_contracts::runtime::WechatMiniProgramPayParamsResponse;
use shared_kernel::offset_datetime_to_unix_micros;
use time::OffsetDateTime;
use tracing::{info, warn};

use crate::{http_error::AppError, state::AppState};

const WECHAT_PAY_PROVIDER_MOCK: &str = "mock";
const WECHAT_PAY_PROVIDER_REAL: &str = "real";
const WECHAT_PAY_BODY_SIGNATURE_METHOD: &str = "WECHATPAY2-SHA256-RSA2048";
const WECHAT_PAY_PAY_SIGN_TYPE: &str = "RSA";
const WECHAT_PAY_NOTIFY_SUCCESS: &str = "<xml><return_code><![CDATA[SUCCESS]]></return_code></xml>";
const WECHAT_PAY_APP_ID_MAX_CHARS: usize = 32;
const WECHAT_PAY_MCH_ID_MAX_CHARS: usize = 32;
const WECHAT_PAY_DESCRIPTION_MAX_CHARS: usize = 127;
const WECHAT_PAY_OUT_TRADE_NO_MAX_CHARS: usize = 32;
const WECHAT_PAY_NOTIFY_URL_MAX_CHARS: usize = 255;
const WECHAT_PAY_OPENID_MAX_CHARS: usize = 128;

#[derive(Clone, Debug)]
pub enum WechatPayClient {
    Disabled,
    Mock,
    Real(Arc<RealWechatPayClient>),
}

#[derive(Clone, Debug)]
pub struct RealWechatPayClient {
    client: reqwest::Client,
    app_id: String,
    mch_id: String,
    merchant_serial_no: String,
    private_key: Arc<signature::RsaKeyPair>,
    platform_public_key_der: Vec<u8>,
    platform_serial_no: String,
    api_v3_key: String,
    notify_url: String,
    jsapi_endpoint: String,
}

#[derive(Clone, Debug)]
pub struct WechatMiniProgramOrderRequest {
    pub order_id: String,
    pub description: String,
    pub amount_cents: u64,
    pub payer_openid: String,
}

#[derive(Clone, Debug)]
pub struct WechatPayNotifyOrder {
    pub out_trade_no: String,
    pub transaction_id: Option<String>,
    pub trade_state: String,
    pub success_time: Option<String>,
}

#[derive(Debug)]
pub enum WechatPayError {
    Disabled,
    InvalidConfig(String),
    InvalidRequest(String),
    RequestFailed(String),
    Upstream(String),
    Deserialize(String),
    Crypto(String),
    InvalidSignature,
}

#[derive(Serialize)]
struct WechatJsapiOrderRequest<'a> {
    appid: &'a str,
    mchid: &'a str,
    description: &'a str,
    out_trade_no: &'a str,
    notify_url: &'a str,
    amount: WechatJsapiAmount,
    payer: WechatJsapiPayer<'a>,
}

#[derive(Serialize)]
struct WechatJsapiAmount {
    total: i64,
    currency: &'static str,
}

#[derive(Serialize)]
struct WechatJsapiPayer<'a> {
    openid: &'a str,
}

#[derive(Deserialize)]
struct WechatJsapiOrderResponse {
    prepay_id: Option<String>,
    code: Option<String>,
    message: Option<String>,
}

#[derive(Deserialize)]
struct WechatPayNotifyBody {
    #[serde(default)]
    resource: Option<WechatPayNotifyResource>,
}

#[derive(Deserialize)]
struct WechatPayNotifyResource {
    ciphertext: String,
    nonce: String,
    #[serde(default)]
    associated_data: Option<String>,
}

#[derive(Deserialize)]
struct WechatPayTransactionResource {
    out_trade_no: String,
    #[serde(default)]
    transaction_id: Option<String>,
    trade_state: String,
    #[serde(default)]
    success_time: Option<String>,
}

impl WechatPayClient {
    pub fn from_config(config: &crate::config::AppConfig) -> Result<Self, WechatPayError> {
        if !config.wechat_pay_enabled {
            return Ok(Self::Disabled);
        }

        if config
            .wechat_pay_provider
            .trim()
            .eq_ignore_ascii_case(WECHAT_PAY_PROVIDER_MOCK)
        {
            return Ok(Self::Mock);
        }

        if !config
            .wechat_pay_provider
            .trim()
            .eq_ignore_ascii_case(WECHAT_PAY_PROVIDER_REAL)
        {
            return Err(WechatPayError::InvalidConfig(
                "WECHAT_PAY_PROVIDER 仅支持 mock 或 real".to_string(),
            ));
        }

        let app_id = config
            .wechat_mini_program_app_id
            .as_ref()
            .or(config.wechat_app_id.as_ref())
            .map(|value| value.trim())
            .filter(|value| !value.is_empty())
            .ok_or_else(|| WechatPayError::InvalidConfig("微信支付缺少小程序 AppID".to_string()))?
            .to_string();
        let mch_id = required_config(config.wechat_pay_mch_id.as_deref(), "WECHAT_PAY_MCH_ID")?;
        let merchant_serial_no = required_config(
            config.wechat_pay_merchant_serial_no.as_deref(),
            "WECHAT_PAY_MERCHANT_SERIAL_NO",
        )?;
        let private_key_pem = read_private_key_pem(
            config.wechat_pay_private_key_pem.as_deref(),
            config.wechat_pay_private_key_path.as_deref(),
        )?;
        let private_key = Arc::new(parse_rsa_private_key(&private_key_pem)?);
        let platform_public_key_pem = read_pem(
            config.wechat_pay_platform_public_key_pem.as_deref(),
            config.wechat_pay_platform_public_key_path.as_deref(),
            "WECHAT_PAY_PLATFORM_PUBLIC_KEY_PEM 或 WECHAT_PAY_PLATFORM_PUBLIC_KEY_PATH 未配置",
            "读取微信支付平台公钥失败",
        )?;
        let platform_public_key_der = parse_public_key_pem(&platform_public_key_pem)?;
        let platform_serial_no = required_config(
            config.wechat_pay_platform_serial_no.as_deref(),
            "WECHAT_PAY_PLATFORM_SERIAL_NO",
        )?;
        let api_v3_key = required_config(
            config.wechat_pay_api_v3_key.as_deref(),
            "WECHAT_PAY_API_V3_KEY",
        )?;
        if api_v3_key.as_bytes().len() != 32 {
            return Err(WechatPayError::InvalidConfig(
                "WECHAT_PAY_API_V3_KEY 必须是 32 字节字符串".to_string(),
            ));
        }
        let notify_url = required_config(
            config.wechat_pay_notify_url.as_deref(),
            "WECHAT_PAY_NOTIFY_URL",
        )?;
        validate_notify_url(&notify_url, "WECHAT_PAY_NOTIFY_URL")?;
        let jsapi_endpoint = normalize_required_url(
            &config.wechat_pay_jsapi_endpoint,
            "WECHAT_PAY_JSAPI_ENDPOINT",
        )?;

        Ok(Self::Real(Arc::new(RealWechatPayClient {
            client: reqwest::Client::new(),
            app_id,
            mch_id,
            merchant_serial_no,
            private_key,
            platform_public_key_der,
            platform_serial_no,
            api_v3_key,
            notify_url,
            jsapi_endpoint,
        })))
    }

    pub async fn create_mini_program_order(
        &self,
        request: WechatMiniProgramOrderRequest,
    ) -> Result<WechatMiniProgramPayParamsResponse, WechatPayError> {
        match self {
            Self::Disabled => Err(WechatPayError::Disabled),
            Self::Mock => Ok(build_mock_pay_params(&request.order_id)),
            Self::Real(client) => client.create_mini_program_order(request).await,
        }
    }

    pub fn parse_notify(
        &self,
        headers: &HeaderMap,
        body: &[u8],
    ) -> Result<WechatPayNotifyOrder, WechatPayError> {
        match self {
            Self::Disabled => Err(WechatPayError::Disabled),
            Self::Mock => parse_mock_notify(body),
            Self::Real(client) => client.parse_notify(headers, body),
        }
    }
}

impl RealWechatPayClient {
    async fn create_mini_program_order(
        &self,
        request: WechatMiniProgramOrderRequest,
    ) -> Result<WechatMiniProgramPayParamsResponse, WechatPayError> {
        validate_jsapi_order_request(self, &request)?;
        let amount_total = i64::try_from(request.amount_cents)
            .map_err(|_| WechatPayError::InvalidRequest("微信支付金额超出 i64 范围".to_string()))?;
        let body = serde_json::to_string(&WechatJsapiOrderRequest {
            appid: &self.app_id,
            mchid: &self.mch_id,
            description: &request.description,
            out_trade_no: &request.order_id,
            notify_url: &self.notify_url,
            amount: WechatJsapiAmount {
                total: amount_total,
                currency: "CNY",
            },
            payer: WechatJsapiPayer {
                openid: &request.payer_openid,
            },
        })
        .map_err(|error| WechatPayError::Deserialize(format!("微信支付请求序列化失败：{error}")))?;
        let timestamp = OffsetDateTime::now_utc().unix_timestamp().to_string();
        let nonce = create_nonce()?;
        let authorization = self.build_authorization(
            "POST",
            "/v3/pay/transactions/jsapi",
            &timestamp,
            &nonce,
            &body,
        )?;
        let response = self
            .client
            .post(&self.jsapi_endpoint)
            .header("Authorization", authorization)
            .header("Accept", "application/json")
            .header("Content-Type", "application/json")
            .body(body)
            .send()
            .await
            .map_err(|error| {
                WechatPayError::RequestFailed(format!("微信支付 JSAPI 下单请求失败：{error}"))
            })?;
        let status = response.status();
        let response_text = response.text().await.map_err(|error| {
            WechatPayError::Deserialize(format!("微信支付 JSAPI 下单响应读取失败：{error}"))
        })?;
        let payload =
            serde_json::from_str::<WechatJsapiOrderResponse>(&response_text).map_err(|error| {
                WechatPayError::Deserialize(format!("微信支付 JSAPI 下单响应解析失败：{error}"))
            })?;

        if !status.is_success() {
            return Err(WechatPayError::Upstream(format!(
                "微信支付 JSAPI 下单失败：{}",
                payload
                    .message
                    .or(payload.code)
                    .unwrap_or_else(|| format!("HTTP {status}"))
            )));
        }

        let prepay_id = payload
            .prepay_id
            .map(|value| value.trim().to_string())
            .filter(|value| !value.is_empty())
            .ok_or_else(|| WechatPayError::Upstream("微信支付未返回 prepay_id".to_string()))?;
        self.build_pay_params(&prepay_id)
    }

    fn build_authorization(
        &self,
        method: &str,
        canonical_url: &str,
        timestamp: &str,
        nonce: &str,
        body: &str,
    ) -> Result<String, WechatPayError> {
        let message = format!("{method}\n{canonical_url}\n{timestamp}\n{nonce}\n{body}\n");
        let signature = self.sign_message(&message)?;
        Ok(format!(
            "{WECHAT_PAY_BODY_SIGNATURE_METHOD} mchid=\"{}\",nonce_str=\"{}\",timestamp=\"{}\",serial_no=\"{}\",signature=\"{}\"",
            self.mch_id, nonce, timestamp, self.merchant_serial_no, signature
        ))
    }

    fn build_pay_params(
        &self,
        prepay_id: &str,
    ) -> Result<WechatMiniProgramPayParamsResponse, WechatPayError> {
        let time_stamp = OffsetDateTime::now_utc().unix_timestamp().to_string();
        let nonce_str = create_nonce()?;
        let package = format!("prepay_id={prepay_id}");
        let message = format!(
            "{}\n{}\n{}\n{}\n",
            self.app_id, time_stamp, nonce_str, package
        );
        let pay_sign = self.sign_message(&message)?;

        Ok(WechatMiniProgramPayParamsResponse {
            time_stamp,
            nonce_str,
            package,
            sign_type: WECHAT_PAY_PAY_SIGN_TYPE.to_string(),
            pay_sign,
        })
    }

    fn parse_notify(
        &self,
        headers: &HeaderMap,
        body: &[u8],
    ) -> Result<WechatPayNotifyOrder, WechatPayError> {
        self.verify_notify_signature(headers, body)?;
        let notify = serde_json::from_slice::<WechatPayNotifyBody>(body).map_err(|error| {
            WechatPayError::Deserialize(format!("微信支付通知解析失败：{error}"))
        })?;
        let resource = notify.resource.ok_or_else(|| {
            WechatPayError::InvalidRequest("微信支付通知缺少 resource".to_string())
        })?;
        let plain_text = decrypt_aes_256_gcm(
            self.api_v3_key.as_bytes(),
            resource.nonce.as_bytes(),
            resource.associated_data.as_deref().unwrap_or("").as_bytes(),
            resource.ciphertext.as_str(),
        )?;
        let transaction = serde_json::from_slice::<WechatPayTransactionResource>(&plain_text)
            .map_err(|error| {
                WechatPayError::Deserialize(format!("微信支付通知资源解析失败：{error}"))
            })?;

        Ok(WechatPayNotifyOrder {
            out_trade_no: transaction.out_trade_no,
            transaction_id: transaction
                .transaction_id
                .map(|value| value.trim().to_string())
                .filter(|value| !value.is_empty()),
            trade_state: transaction.trade_state,
            success_time: transaction.success_time,
        })
    }

    fn verify_notify_signature(
        &self,
        headers: &HeaderMap,
        body: &[u8],
    ) -> Result<(), WechatPayError> {
        let timestamp = read_required_header(headers, "Wechatpay-Timestamp")?;
        let nonce = read_required_header(headers, "Wechatpay-Nonce")?;
        let signature = read_required_header(headers, "Wechatpay-Signature")?;
        let serial = read_required_header(headers, "Wechatpay-Serial")?;
        if serial != self.platform_serial_no {
            return Err(WechatPayError::InvalidSignature);
        }

        let message = format!(
            "{}\n{}\n{}\n",
            timestamp,
            nonce,
            String::from_utf8_lossy(body)
        );
        let signature_bytes = BASE64_STANDARD
            .decode(signature)
            .map_err(|_| WechatPayError::InvalidSignature)?;
        let public_key = signature::UnparsedPublicKey::new(
            &signature::RSA_PKCS1_2048_8192_SHA256,
            &self.platform_public_key_der,
        );
        public_key
            .verify(message.as_bytes(), &signature_bytes)
            .map_err(|_| WechatPayError::InvalidSignature)
    }

    fn sign_message(&self, message: &str) -> Result<String, WechatPayError> {
        let rng = SystemRandom::new();
        let mut signature = vec![0_u8; self.private_key.public().modulus_len()];
        self.private_key
            .sign(
                &signature::RSA_PKCS1_SHA256,
                &rng,
                message.as_bytes(),
                &mut signature,
            )
            .map_err(|_| WechatPayError::Crypto("微信支付签名失败".to_string()))?;
        Ok(BASE64_STANDARD.encode(signature))
    }
}

pub async fn handle_wechat_pay_notify(
    State(state): State<AppState>,
    headers: HeaderMap,
    body: Bytes,
) -> Result<&'static str, AppError> {
    let notify = state
        .wechat_pay_client()
        .parse_notify(&headers, &body)
        .map_err(map_wechat_pay_notify_error)?;
    if notify.trade_state != "SUCCESS" {
        info!(
            order_id = notify.out_trade_no.as_str(),
            trade_state = notify.trade_state.as_str(),
            "收到非成功微信支付通知"
        );
        return Ok(WECHAT_PAY_NOTIFY_SUCCESS);
    }

    let paid_at_micros = notify
        .success_time
        .as_deref()
        .and_then(|value| shared_kernel::parse_rfc3339(value).ok())
        .map(offset_datetime_to_unix_micros)
        .unwrap_or_else(current_unix_micros);

    state
        .spacetime_client()
        .mark_profile_recharge_order_paid(
            notify.out_trade_no.clone(),
            paid_at_micros,
            notify.transaction_id.clone(),
        )
        .await
        .map_err(|error| {
            AppError::from_status(StatusCode::BAD_GATEWAY)
                .with_message(format!("确认微信支付订单失败：{error}"))
        })?;
    info!(
        order_id = notify.out_trade_no.as_str(),
        "微信支付通知已确认订单入账"
    );

    Ok(WECHAT_PAY_NOTIFY_SUCCESS)
}

pub fn map_wechat_pay_error(error: WechatPayError) -> AppError {
    match error {
        WechatPayError::Disabled => AppError::from_status(StatusCode::BAD_REQUEST)
            .with_message("微信支付暂未启用")
            .with_details(json!({ "provider": "wechat_pay" })),
        WechatPayError::InvalidConfig(message) => {
            AppError::from_status(StatusCode::SERVICE_UNAVAILABLE)
                .with_message(message)
                .with_details(json!({ "provider": "wechat_pay" }))
        }
        WechatPayError::InvalidRequest(message) => AppError::from_status(StatusCode::BAD_REQUEST)
            .with_message(message)
            .with_details(json!({ "provider": "wechat_pay" })),
        WechatPayError::RequestFailed(message)
        | WechatPayError::Upstream(message)
        | WechatPayError::Deserialize(message)
        | WechatPayError::Crypto(message) => AppError::from_status(StatusCode::BAD_GATEWAY)
            .with_message(message)
            .with_details(json!({ "provider": "wechat_pay" })),
        WechatPayError::InvalidSignature => AppError::from_status(StatusCode::UNAUTHORIZED)
            .with_message("微信支付通知签名无效")
            .with_details(json!({ "provider": "wechat_pay" })),
    }
}

pub fn map_wechat_pay_init_error(error: WechatPayError) -> crate::state::AppStateInitError {
    crate::state::AppStateInitError::WechatPay(error.to_string())
}

pub fn build_wechat_payment_request(
    order_id: String,
    product_title: String,
    amount_cents: u64,
    payer_openid: String,
) -> WechatMiniProgramOrderRequest {
    WechatMiniProgramOrderRequest {
        order_id,
        description: format!("陶泥儿 - {product_title}"),
        amount_cents,
        payer_openid,
    }
}

pub fn current_unix_micros() -> i64 {
    let value = OffsetDateTime::now_utc().unix_timestamp_nanos() / 1_000;
    i64::try_from(value).unwrap_or(i64::MAX)
}

fn map_wechat_pay_notify_error(error: WechatPayError) -> AppError {
    warn!(error = %error, "微信支付通知处理失败");
    map_wechat_pay_error(error)
}

fn build_mock_pay_params(order_id: &str) -> WechatMiniProgramPayParamsResponse {
    let time_stamp = OffsetDateTime::now_utc().unix_timestamp().to_string();
    let nonce_str = "mock-nonce".to_string();
    let package = format!("prepay_id=mock-{order_id}");
    let pay_sign = hex_sha256(format!("{time_stamp}\n{nonce_str}\n{package}\n").as_bytes());

    WechatMiniProgramPayParamsResponse {
        time_stamp,
        nonce_str,
        package,
        sign_type: WECHAT_PAY_PAY_SIGN_TYPE.to_string(),
        pay_sign,
    }
}

fn parse_mock_notify(body: &[u8]) -> Result<WechatPayNotifyOrder, WechatPayError> {
    let value = serde_json::from_slice::<Value>(body).map_err(|error| {
        WechatPayError::Deserialize(format!("mock 微信支付通知解析失败：{error}"))
    })?;
    Ok(WechatPayNotifyOrder {
        out_trade_no: value
            .get("outTradeNo")
            .or_else(|| value.get("out_trade_no"))
            .and_then(Value::as_str)
            .map(str::trim)
            .filter(|value| !value.is_empty())
            .ok_or_else(|| {
                WechatPayError::InvalidRequest("mock 微信支付通知缺少 outTradeNo".to_string())
            })?
            .to_string(),
        transaction_id: value
            .get("transactionId")
            .or_else(|| value.get("transaction_id"))
            .and_then(Value::as_str)
            .map(str::trim)
            .filter(|value| !value.is_empty())
            .map(ToOwned::to_owned),
        trade_state: value
            .get("tradeState")
            .or_else(|| value.get("trade_state"))
            .and_then(Value::as_str)
            .unwrap_or("SUCCESS")
            .to_string(),
        success_time: value
            .get("successTime")
            .or_else(|| value.get("success_time"))
            .and_then(Value::as_str)
            .map(ToOwned::to_owned),
    })
}

fn required_config(value: Option<&str>, key: &str) -> Result<String, WechatPayError> {
    value
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .map(ToOwned::to_owned)
        .ok_or_else(|| WechatPayError::InvalidConfig(format!("{key} 未配置")))
}

fn normalize_required_url(value: &str, key: &str) -> Result<String, WechatPayError> {
    let value = value.trim();
    if value.starts_with("https://") {
        return Ok(value.to_string());
    }

    Err(WechatPayError::InvalidConfig(format!(
        "{key} 必须是 https 地址"
    )))
}

fn validate_notify_url(value: &str, key: &str) -> Result<(), WechatPayError> {
    if value.chars().count() > WECHAT_PAY_NOTIFY_URL_MAX_CHARS {
        return Err(WechatPayError::InvalidConfig(format!(
            "{key} 不能超过 {WECHAT_PAY_NOTIFY_URL_MAX_CHARS} 字符"
        )));
    }
    if value.contains('?') || value.contains('#') {
        return Err(WechatPayError::InvalidConfig(format!(
            "{key} 不能包含 query 或 fragment"
        )));
    }
    Ok(())
}

fn validate_jsapi_order_request(
    client: &RealWechatPayClient,
    request: &WechatMiniProgramOrderRequest,
) -> Result<(), WechatPayError> {
    validate_non_empty_max_chars(
        &client.app_id,
        WECHAT_PAY_APP_ID_MAX_CHARS,
        "微信支付 appid",
    )?;
    if !client.app_id.starts_with("wx") {
        return Err(WechatPayError::InvalidConfig(
            "微信支付 appid 必须使用小程序 AppID".to_string(),
        ));
    }
    validate_non_empty_max_chars(
        &client.mch_id,
        WECHAT_PAY_MCH_ID_MAX_CHARS,
        "微信支付 mchid",
    )?;
    if !client.mch_id.chars().all(|ch| ch.is_ascii_digit()) {
        return Err(WechatPayError::InvalidConfig(
            "微信支付 mchid 必须是数字字符串".to_string(),
        ));
    }

    validate_non_empty_max_chars(
        &request.description,
        WECHAT_PAY_DESCRIPTION_MAX_CHARS,
        "微信支付商品描述",
    )?;
    validate_out_trade_no(&request.order_id)?;
    if request.amount_cents == 0 {
        return Err(WechatPayError::InvalidRequest(
            "微信支付金额必须大于 0 分".to_string(),
        ));
    }
    validate_non_empty_max_chars(
        &request.payer_openid,
        WECHAT_PAY_OPENID_MAX_CHARS,
        "微信支付 payer.openid",
    )?;
    Ok(())
}

fn validate_non_empty_max_chars(
    value: &str,
    max_chars: usize,
    field_name: &str,
) -> Result<(), WechatPayError> {
    let value = value.trim();
    if value.is_empty() {
        return Err(WechatPayError::InvalidRequest(format!(
            "{field_name} 不能为空"
        )));
    }
    if value.chars().count() > max_chars {
        return Err(WechatPayError::InvalidRequest(format!(
            "{field_name} 不能超过 {max_chars} 字符"
        )));
    }
    Ok(())
}

fn validate_out_trade_no(value: &str) -> Result<(), WechatPayError> {
    validate_non_empty_max_chars(
        value,
        WECHAT_PAY_OUT_TRADE_NO_MAX_CHARS,
        "微信支付 out_trade_no",
    )?;
    if value.chars().count() < 6 {
        return Err(WechatPayError::InvalidRequest(
            "微信支付 out_trade_no 不能少于 6 字符".to_string(),
        ));
    }
    if !value
        .chars()
        .all(|ch| ch.is_ascii_alphanumeric() || matches!(ch, '_' | '-' | '|' | '*'))
    {
        return Err(WechatPayError::InvalidRequest(
            "微信支付 out_trade_no 只能包含数字、大小写字母、_、-、|、*".to_string(),
        ));
    }
    Ok(())
}

fn read_private_key_pem(
    inline_pem: Option<&str>,
    path: Option<&Path>,
) -> Result<String, WechatPayError> {
    read_pem(
        inline_pem,
        path,
        "WECHAT_PAY_PRIVATE_KEY_PEM 或 WECHAT_PAY_PRIVATE_KEY_PATH 未配置",
        "读取微信支付私钥失败",
    )
}

fn read_pem(
    inline_pem: Option<&str>,
    path: Option<&Path>,
    missing_message: &str,
    read_error_prefix: &str,
) -> Result<String, WechatPayError> {
    if let Some(value) = inline_pem.map(str::trim).filter(|value| !value.is_empty()) {
        return Ok(value.replace("\\n", "\n"));
    }
    let Some(path) = path else {
        return Err(WechatPayError::InvalidConfig(missing_message.to_string()));
    };
    fs::read_to_string(path).map_err(|error| {
        WechatPayError::InvalidConfig(format!("{read_error_prefix}：{}：{error}", path.display()))
    })
}

fn parse_rsa_private_key(pem: &str) -> Result<signature::RsaKeyPair, WechatPayError> {
    let (label, der) = parse_single_pem_block(pem)?;
    match label.as_str() {
        "PRIVATE KEY" => signature::RsaKeyPair::from_pkcs8(&der),
        "RSA PRIVATE KEY" => signature::RsaKeyPair::from_der(&der),
        _ => {
            return Err(WechatPayError::InvalidConfig(
                "微信支付私钥必须是 PRIVATE KEY 或 RSA PRIVATE KEY PEM".to_string(),
            ));
        }
    }
    .map_err(|error| WechatPayError::InvalidConfig(format!("微信支付私钥解析失败：{error}")))
}

fn parse_public_key_pem(pem: &str) -> Result<Vec<u8>, WechatPayError> {
    let (label, der) = parse_single_pem_block(pem)?;
    if label != "PUBLIC KEY" {
        return Err(WechatPayError::InvalidConfig(
            "微信支付平台公钥必须是 PUBLIC KEY PEM".to_string(),
        ));
    }
    Ok(der)
}

fn parse_single_pem_block(pem: &str) -> Result<(String, Vec<u8>), WechatPayError> {
    let mut label: Option<String> = None;
    let mut content = String::new();
    for line in pem.lines().map(str::trim).filter(|line| !line.is_empty()) {
        if let Some(raw_label) = line
            .strip_prefix("-----BEGIN ")
            .and_then(|value| value.strip_suffix("-----"))
        {
            label = Some(raw_label.trim().to_string());
            continue;
        }
        if line.starts_with("-----END ") {
            break;
        }
        if label.is_some() {
            content.push_str(line);
        }
    }
    let label = label
        .ok_or_else(|| WechatPayError::InvalidConfig("微信支付 PEM 缺少 BEGIN 标记".to_string()))?;
    let der = BASE64_STANDARD
        .decode(content)
        .map_err(|_| WechatPayError::InvalidConfig("微信支付 PEM base64 无效".to_string()))?;
    if der.is_empty() {
        return Err(WechatPayError::InvalidConfig(
            "微信支付 PEM 内容为空".to_string(),
        ));
    }
    Ok((label, der))
}

fn create_nonce() -> Result<String, WechatPayError> {
    let mut bytes = [0_u8; 16];
    SystemRandom::new()
        .fill(&mut bytes)
        .map_err(|_| WechatPayError::Crypto("生成微信支付 nonce 失败".to_string()))?;
    Ok(hex_encode(&bytes))
}

fn decrypt_aes_256_gcm(
    key: &[u8],
    nonce: &[u8],
    associated_data: &[u8],
    ciphertext_base64: &str,
) -> Result<Vec<u8>, WechatPayError> {
    let mut ciphertext = BASE64_STANDARD
        .decode(ciphertext_base64)
        .map_err(|_| WechatPayError::Crypto("微信支付通知密文 base64 无效".to_string()))?;
    if ciphertext.len() < aead::AES_256_GCM.tag_len() {
        return Err(WechatPayError::Crypto(
            "微信支付通知密文长度无效".to_string(),
        ));
    }
    let nonce = aead::Nonce::try_assume_unique_for_key(nonce)
        .map_err(|_| WechatPayError::Crypto("微信支付通知 nonce 长度无效".to_string()))?;
    let key = aead::UnboundKey::new(&aead::AES_256_GCM, key)
        .map_err(|_| WechatPayError::Crypto("微信支付通知解密 key 无效".to_string()))?;
    let plain_text = aead::LessSafeKey::new(key)
        .open_in_place(
            nonce,
            aead::Aad::from(associated_data),
            ciphertext.as_mut_slice(),
        )
        .map_err(|_| WechatPayError::Crypto("微信支付通知认证或解密失败".to_string()))?;
    Ok(plain_text.to_vec())
}

fn read_required_header<'a>(
    headers: &'a HeaderMap,
    name: &'static str,
) -> Result<&'a str, WechatPayError> {
    headers
        .get(name)
        .and_then(|value| value.to_str().ok())
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .ok_or(WechatPayError::InvalidSignature)
}

fn hex_sha256(content: &[u8]) -> String {
    let mut hasher = Sha256::new();
    hasher.update(content);
    hex_encode(&hasher.finalize())
}

fn hex_encode(bytes: &[u8]) -> String {
    bytes.iter().map(|byte| format!("{byte:02x}")).collect()
}

impl std::fmt::Display for WechatPayError {
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Disabled => formatter.write_str("微信支付暂未启用"),
            Self::InvalidConfig(message)
            | Self::InvalidRequest(message)
            | Self::RequestFailed(message)
            | Self::Upstream(message)
            | Self::Deserialize(message)
            | Self::Crypto(message) => formatter.write_str(message),
            Self::InvalidSignature => formatter.write_str("微信支付通知签名无效"),
        }
    }
}

impl std::error::Error for WechatPayError {}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn mock_pay_params_use_request_payment_shape() {
        let params = build_mock_pay_params("recharge:user:1:points_60");

        assert!(!params.time_stamp.is_empty());
        assert_eq!(params.sign_type, "RSA");
        assert!(params.package.starts_with("prepay_id=mock-"));
        assert!(!params.pay_sign.is_empty());
    }

    #[test]
    fn jsapi_order_request_uses_wechat_v3_snake_case_fields() {
        let body = serde_json::to_value(WechatJsapiOrderRequest {
            appid: "wx-test-app",
            mchid: "1900000001",
            description: "陶泥儿 - 60泥点",
            out_trade_no: "rcgtest001",
            notify_url: "https://api.example.com/api/profile/recharge/wechat/notify",
            amount: WechatJsapiAmount {
                total: 600,
                currency: "CNY",
            },
            payer: WechatJsapiPayer {
                openid: "openid-test",
            },
        })
        .expect("JSAPI order request should serialize");

        assert_eq!(body["out_trade_no"], "rcgtest001");
        assert_eq!(
            body["notify_url"],
            "https://api.example.com/api/profile/recharge/wechat/notify"
        );
        assert!(body.get("outTradeNo").is_none());
        assert!(body.get("notifyUrl").is_none());
    }

    #[test]
    fn jsapi_order_request_rejects_provider_field_limit_violations() {
        assert!(validate_out_trade_no("abc12").is_err());
        assert!(validate_out_trade_no("abc123").is_ok());
        assert!(validate_out_trade_no("abc123_-|*").is_ok());
        assert!(validate_out_trade_no("abc123中文").is_err());
        assert!(validate_out_trade_no("a".repeat(33).as_str()).is_err());

        assert!(validate_notify_url("https://api.example.com/pay/notify", "notify").is_ok());
        assert!(validate_notify_url("https://api.example.com/pay/notify?x=1", "notify").is_err());
        assert!(validate_notify_url(&format!("https://{}", "a".repeat(248)), "notify").is_err());

        validate_non_empty_max_chars("陶泥儿 - 60泥点", WECHAT_PAY_DESCRIPTION_MAX_CHARS, "描述")
            .expect("short description should pass");
        assert!(
            validate_non_empty_max_chars(
                &"泥".repeat(128),
                WECHAT_PAY_DESCRIPTION_MAX_CHARS,
                "描述"
            )
            .is_err()
        );
        validate_non_empty_max_chars("openid-test", WECHAT_PAY_OPENID_MAX_CHARS, "openid")
            .expect("short openid should pass");
        assert!(
            validate_non_empty_max_chars(&"o".repeat(129), WECHAT_PAY_OPENID_MAX_CHARS, "openid")
                .is_err()
        );
    }

    #[test]
    fn parse_mock_notify_defaults_success_state() {
        let notify =
            parse_mock_notify(br#"{"outTradeNo":"order-1"}"#).expect("mock notify should parse");

        assert_eq!(notify.out_trade_no, "order-1");
        assert_eq!(notify.transaction_id, None);
        assert_eq!(notify.trade_state, "SUCCESS");
    }
}