use super::traits::{Channel, ChannelMessage};
use async_trait::async_trait;
use uuid::Uuid;

/// Telegram channel — long-polls the Bot API for updates
pub struct TelegramChannel {
    bot_token: String,
    allowed_users: Vec<String>,
    client: reqwest::Client,
}

impl TelegramChannel {
    pub fn new(bot_token: String, allowed_users: Vec<String>) -> Self {
        Self {
            bot_token,
            allowed_users,
            client: reqwest::Client::new(),
        }
    }

    fn api_url(&self, method: &str) -> String {
        format!("https://api.telegram.org/bot{}/{method}", self.bot_token)
    }

    fn is_user_allowed(&self, username: &str) -> bool {
        self.allowed_users.iter().any(|u| u == "*" || u == username)
    }
}

#[async_trait]
impl Channel for TelegramChannel {
    fn name(&self) -> &str {
        "telegram"
    }

    async fn send(&self, message: &str, chat_id: &str) -> anyhow::Result<()> {
        let body = serde_json::json!({
            "chat_id": chat_id,
            "text": message,
            "parse_mode": "Markdown"
        });

        self.client
            .post(self.api_url("sendMessage"))
            .json(&body)
            .send()
            .await?;

        Ok(())
    }

    async fn listen(&self, tx: tokio::sync::mpsc::Sender<ChannelMessage>) -> anyhow::Result<()> {
        let mut offset: i64 = 0;

        tracing::info!("Telegram channel listening for messages...");

        loop {
            let url = self.api_url("getUpdates");
            let body = serde_json::json!({
                "offset": offset,
                "timeout": 30,
                "allowed_updates": ["message"]
            });

            let resp = match self.client.post(&url).json(&body).send().await {
                Ok(r) => r,
                Err(e) => {
                    tracing::warn!("Telegram poll error: {e}");
                    tokio::time::sleep(std::time::Duration::from_secs(5)).await;
                    continue;
                }
            };

            let data: serde_json::Value = match resp.json().await {
                Ok(d) => d,
                Err(e) => {
                    tracing::warn!("Telegram parse error: {e}");
                    tokio::time::sleep(std::time::Duration::from_secs(5)).await;
                    continue;
                }
            };

            if let Some(results) = data.get("result").and_then(serde_json::Value::as_array) {
                for update in results {
                    // Advance offset past this update
                    if let Some(uid) = update.get("update_id").and_then(serde_json::Value::as_i64) {
                        offset = uid + 1;
                    }

                    let Some(message) = update.get("message") else {
                        continue;
                    };

                    let Some(text) = message.get("text").and_then(serde_json::Value::as_str) else {
                        continue;
                    };

                    let username = message
                        .get("from")
                        .and_then(|f| f.get("username"))
                        .and_then(|u| u.as_str())
                        .unwrap_or("unknown");

                    if !self.is_user_allowed(username) {
                        tracing::warn!(
                            "Telegram: ignoring message from unauthorized user: {username}"
                        );
                        continue;
                    }

                    let chat_id = message
                        .get("chat")
                        .and_then(|c| c.get("id"))
                        .and_then(serde_json::Value::as_i64)
                        .map(|id| id.to_string())
                        .unwrap_or_default();

                    let msg = ChannelMessage {
                        id: Uuid::new_v4().to_string(),
                        sender: chat_id,
                        content: text.to_string(),
                        channel: "telegram".to_string(),
                        timestamp: std::time::SystemTime::now()
                            .duration_since(std::time::UNIX_EPOCH)
                            .unwrap_or_default()
                            .as_secs(),
                    };

                    if tx.send(msg).await.is_err() {
                        return Ok(());
                    }
                }
            }
        }
    }

    async fn health_check(&self) -> bool {
        self.client
            .get(self.api_url("getMe"))
            .send()
            .await
            .map(|r| r.status().is_success())
            .unwrap_or(false)
    }
}

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

    #[test]
    fn telegram_channel_name() {
        let ch = TelegramChannel::new("fake-token".into(), vec!["*".into()]);
        assert_eq!(ch.name(), "telegram");
    }

    #[test]
    fn telegram_api_url() {
        let ch = TelegramChannel::new("123:ABC".into(), vec![]);
        assert_eq!(
            ch.api_url("getMe"),
            "https://api.telegram.org/bot123:ABC/getMe"
        );
    }

    #[test]
    fn telegram_user_allowed_wildcard() {
        let ch = TelegramChannel::new("t".into(), vec!["*".into()]);
        assert!(ch.is_user_allowed("anyone"));
    }

    #[test]
    fn telegram_user_allowed_specific() {
        let ch = TelegramChannel::new("t".into(), vec!["alice".into(), "bob".into()]);
        assert!(ch.is_user_allowed("alice"));
        assert!(!ch.is_user_allowed("eve"));
    }

    #[test]
    fn telegram_user_denied_empty() {
        let ch = TelegramChannel::new("t".into(), vec![]);
        assert!(!ch.is_user_allowed("anyone"));
    }

    #[test]
    fn telegram_user_exact_match_not_substring() {
        let ch = TelegramChannel::new("t".into(), vec!["alice".into()]);
        assert!(!ch.is_user_allowed("alice_bot"));
        assert!(!ch.is_user_allowed("alic"));
        assert!(!ch.is_user_allowed("malice"));
    }

    #[test]
    fn telegram_user_empty_string_denied() {
        let ch = TelegramChannel::new("t".into(), vec!["alice".into()]);
        assert!(!ch.is_user_allowed(""));
    }

    #[test]
    fn telegram_user_case_sensitive() {
        let ch = TelegramChannel::new("t".into(), vec!["Alice".into()]);
        assert!(ch.is_user_allowed("Alice"));
        assert!(!ch.is_user_allowed("alice"));
        assert!(!ch.is_user_allowed("ALICE"));
    }

    #[test]
    fn telegram_wildcard_with_specific_users() {
        let ch = TelegramChannel::new("t".into(), vec!["alice".into(), "*".into()]);
        assert!(ch.is_user_allowed("alice"));
        assert!(ch.is_user_allowed("bob"));
        assert!(ch.is_user_allowed("anyone"));
    }
}