use std::{collections::BTreeMap, error::Error, fmt};

use reqwest::Client;
use serde::{Deserialize, Serialize};
use serde_json::json;
use tracing::warn;
use url::Url;

pub const DEFAULT_WECHAT_STABLE_ACCESS_TOKEN_ENDPOINT: &str =
    "https://api.weixin.qq.com/cgi-bin/stable_token";
pub const DEFAULT_WECHAT_SUBSCRIBE_MESSAGE_ENDPOINT: &str =
    "https://api.weixin.qq.com/cgi-bin/message/subscribe/send";

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WechatConfig {
    pub app_id: Option<String>,
    pub app_secret: Option<String>,
    pub stable_access_token_endpoint: String,
    pub subscribe_message_endpoint: String,
}

#[derive(Clone, Debug)]
pub struct WechatClient {
    client: Client,
    config: WechatConfig,
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct WechatSubscribeMessageRequest {
    pub touser: String,
    pub template_id: String,
    pub page: Option<String>,
    pub miniprogram_state: Option<String>,
    pub lang: Option<String>,
    pub data: BTreeMap<String, String>,
}

#[derive(Debug, PartialEq, Eq)]
pub enum WechatError {
    InvalidConfig(String),
    RequestFailed(String),
    DeserializeFailed(String),
    Upstream(String),
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum WechatErrorKind {
    InvalidConfig,
    RequestFailed,
    DeserializeFailed,
    Upstream,
}

#[derive(Debug, Deserialize)]
struct WechatStableAccessTokenResponse {
    access_token: Option<String>,
    errcode: Option<i64>,
    errmsg: Option<String>,
}

#[derive(Debug, Deserialize)]
struct WechatSubscribeMessageResponse {
    errcode: i64,
    errmsg: Option<String>,
}

#[derive(Debug, Serialize)]
struct WechatTemplateDataValue {
    value: String,
}

impl WechatClient {
    pub fn new(config: WechatConfig) -> Self {
        Self {
            client: Client::new(),
            config,
        }
    }

    pub async fn send_subscribe_message(
        &self,
        request: WechatSubscribeMessageRequest,
    ) -> Result<(), WechatError> {
        let app_id = self
            .config
            .app_id
            .as_deref()
            .and_then(non_empty)
            .ok_or_else(|| WechatError::InvalidConfig("微信小程序 AppID 未配置".to_string()))?;
        let app_secret = self
            .config
            .app_secret
            .as_deref()
            .and_then(non_empty)
            .ok_or_else(|| WechatError::InvalidConfig("微信小程序 AppSecret 未配置".to_string()))?;

        let access_token = self.request_access_token(app_id, app_secret).await?;
        let mut send_url =
            Url::parse(&self.config.subscribe_message_endpoint).map_err(|error| {
                WechatError::InvalidConfig(format!("微信订阅消息发送地址非法：{error}"))
            })?;
        send_url
            .query_pairs_mut()
            .append_pair("access_token", &access_token);

        let data = request
            .data
            .into_iter()
            .map(|(key, value)| (key, WechatTemplateDataValue { value }))
            .collect::<BTreeMap<_, _>>();
        let payload = json!({
            "touser": request.touser,
            "template_id": request.template_id,
            "page": request.page,
            "miniprogram_state": request.miniprogram_state,
            "lang": request.lang.unwrap_or_else(|| "zh_CN".to_string()),
            "data": data,
        });
        let response = self
            .client
            .post(send_url.as_str())
            .json(&payload)
            .send()
            .await
            .map_err(|error| {
                warn!(error = %error, "微信订阅消息请求失败");
                WechatError::RequestFailed("微信订阅消息请求失败".to_string())
            })?
            .json::<WechatSubscribeMessageResponse>()
            .await
            .map_err(|error| {
                warn!(error = %error, "微信订阅消息响应解析失败");
                WechatError::DeserializeFailed("微信订阅消息响应非法".to_string())
            })?;

        if response.errcode != 0 {
            return Err(WechatError::Upstream(format!(
                "微信订阅消息发送失败：{}",
                response.errmsg.unwrap_or_else(|| format!(
                    "subscribeMessage.send 返回错误 {}",
                    response.errcode
                ))
            )));
        }

        Ok(())
    }

    async fn request_access_token(
        &self,
        app_id: &str,
        app_secret: &str,
    ) -> Result<String, WechatError> {
        let url = Url::parse(&self.config.stable_access_token_endpoint).map_err(|error| {
            WechatError::InvalidConfig(format!("微信 stable_token 地址非法：{error}"))
        })?;
        let payload = self
            .client
            .post(url.as_str())
            .json(&json!({
                "grant_type": "client_credential",
                "appid": app_id,
                "secret": app_secret,
                "force_refresh": false,
            }))
            .send()
            .await
            .map_err(|error| {
                warn!(error = %error, "微信 stable_token 请求失败");
                WechatError::RequestFailed("微信 stable_token 请求失败".to_string())
            })?
            .json::<WechatStableAccessTokenResponse>()
            .await
            .map_err(|error| {
                warn!(error = %error, "微信 stable_token 响应解析失败");
                WechatError::DeserializeFailed("微信 stable_token 响应非法".to_string())
            })?;

        if let Some(errcode) = payload.errcode.filter(|value| *value != 0) {
            return Err(WechatError::Upstream(format!(
                "微信 stable_token 返回错误：{}",
                payload
                    .errmsg
                    .unwrap_or_else(|| format!("errcode={errcode}"))
            )));
        }

        payload
            .access_token
            .and_then(|value| non_empty_owned(value))
            .ok_or_else(|| WechatError::Upstream("微信 stable_token 缺少 access_token".to_string()))
    }
}

impl WechatError {
    pub fn kind(&self) -> WechatErrorKind {
        match self {
            Self::InvalidConfig(_) => WechatErrorKind::InvalidConfig,
            Self::RequestFailed(_) => WechatErrorKind::RequestFailed,
            Self::DeserializeFailed(_) => WechatErrorKind::DeserializeFailed,
            Self::Upstream(_) => WechatErrorKind::Upstream,
        }
    }
}

impl fmt::Display for WechatError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::InvalidConfig(message)
            | Self::RequestFailed(message)
            | Self::DeserializeFailed(message)
            | Self::Upstream(message) => f.write_str(message),
        }
    }
}

impl Error for WechatError {}

fn non_empty(value: &str) -> Option<&str> {
    let trimmed = value.trim();
    if trimmed.is_empty() {
        None
    } else {
        Some(trimmed)
    }
}

fn non_empty_owned(value: String) -> Option<String> {
    if value.trim().is_empty() {
        None
    } else {
        Some(value)
    }
}