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

/// Slack channel — polls conversations.history via Web API
pub struct SlackChannel {
    bot_token: String,
    channel_id: Option<String>,
    allowed_users: Vec<String>,
    client: reqwest::Client,
}

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

    /// Check if a Slack user ID is in the allowlist.
    /// Empty list means deny everyone until explicitly configured.
    /// `"*"` means allow everyone.
    fn is_user_allowed(&self, user_id: &str) -> bool {
        self.allowed_users.iter().any(|u| u == "*" || u == user_id)
    }

    /// Get the bot's own user ID so we can ignore our own messages
    async fn get_bot_user_id(&self) -> Option<String> {
        let resp: serde_json::Value = self
            .client
            .get("https://slack.com/api/auth.test")
            .bearer_auth(&self.bot_token)
            .send()
            .await
            .ok()?
            .json()
            .await
            .ok()?;

        resp.get("user_id")
            .and_then(|u| u.as_str())
            .map(String::from)
    }
}

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

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

        let resp = self
            .client
            .post("https://slack.com/api/chat.postMessage")
            .bearer_auth(&self.bot_token)
            .json(&body)
            .send()
            .await?;

        let status = resp.status();
        let body = resp
            .text()
            .await
            .unwrap_or_else(|e| format!("<failed to read response body: {e}>"));

        if !status.is_success() {
            anyhow::bail!("Slack chat.postMessage failed ({status}): {body}");
        }

        // Slack returns 200 for most app-level errors; check JSON "ok" field
        let parsed: serde_json::Value = serde_json::from_str(&body).unwrap_or_default();
        if parsed.get("ok") == Some(&serde_json::Value::Bool(false)) {
            let err = parsed
                .get("error")
                .and_then(|e| e.as_str())
                .unwrap_or("unknown");
            anyhow::bail!("Slack chat.postMessage failed: {err}");
        }

        Ok(())
    }

    async fn listen(&self, tx: tokio::sync::mpsc::Sender<ChannelMessage>) -> anyhow::Result<()> {
        let channel_id = self
            .channel_id
            .clone()
            .ok_or_else(|| anyhow::anyhow!("Slack channel_id required for listening"))?;

        let bot_user_id = self.get_bot_user_id().await.unwrap_or_default();
        let mut last_ts = String::new();

        tracing::info!("Slack channel listening on #{channel_id}...");

        loop {
            tokio::time::sleep(std::time::Duration::from_secs(3)).await;

            let mut params = vec![("channel", channel_id.clone()), ("limit", "10".to_string())];
            if !last_ts.is_empty() {
                params.push(("oldest", last_ts.clone()));
            }

            let resp = match self
                .client
                .get("https://slack.com/api/conversations.history")
                .bearer_auth(&self.bot_token)
                .query(&params)
                .send()
                .await
            {
                Ok(r) => r,
                Err(e) => {
                    tracing::warn!("Slack poll error: {e}");
                    continue;
                }
            };

            let data: serde_json::Value = match resp.json().await {
                Ok(d) => d,
                Err(e) => {
                    tracing::warn!("Slack parse error: {e}");
                    continue;
                }
            };

            if let Some(messages) = data.get("messages").and_then(|m| m.as_array()) {
                // Messages come newest-first, reverse to process oldest first
                for msg in messages.iter().rev() {
                    let ts = msg.get("ts").and_then(|t| t.as_str()).unwrap_or("");
                    let user = msg
                        .get("user")
                        .and_then(|u| u.as_str())
                        .unwrap_or("unknown");
                    let text = msg.get("text").and_then(|t| t.as_str()).unwrap_or("");

                    // Skip bot's own messages
                    if user == bot_user_id {
                        continue;
                    }

                    // Sender validation
                    if !self.is_user_allowed(user) {
                        tracing::warn!("Slack: ignoring message from unauthorized user: {user}");
                        continue;
                    }

                    // Skip empty or already-seen
                    if text.is_empty() || ts <= last_ts.as_str() {
                        continue;
                    }

                    last_ts = ts.to_string();

                    let channel_msg = ChannelMessage {
                        id: format!("slack_{channel_id}_{ts}"),
                        sender: user.to_string(),
                        reply_target: channel_id.clone(),
                        content: text.to_string(),
                        channel: "slack".to_string(),
                        timestamp: std::time::SystemTime::now()
                            .duration_since(std::time::UNIX_EPOCH)
                            .unwrap_or_default()
                            .as_secs(),
                    };

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

    async fn health_check(&self) -> bool {
        self.client
            .get("https://slack.com/api/auth.test")
            .bearer_auth(&self.bot_token)
            .send()
            .await
            .map(|r| r.status().is_success())
            .unwrap_or(false)
    }
}

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

    #[test]
    fn slack_channel_name() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec![]);
        assert_eq!(ch.name(), "slack");
    }

    #[test]
    fn slack_channel_with_channel_id() {
        let ch = SlackChannel::new("xoxb-fake".into(), Some("C12345".into()), vec![]);
        assert_eq!(ch.channel_id, Some("C12345".to_string()));
    }

    #[test]
    fn empty_allowlist_denies_everyone() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec![]);
        assert!(!ch.is_user_allowed("U12345"));
        assert!(!ch.is_user_allowed("anyone"));
    }

    #[test]
    fn wildcard_allows_everyone() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec!["*".into()]);
        assert!(ch.is_user_allowed("U12345"));
    }

    #[test]
    fn specific_allowlist_filters() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec!["U111".into(), "U222".into()]);
        assert!(ch.is_user_allowed("U111"));
        assert!(ch.is_user_allowed("U222"));
        assert!(!ch.is_user_allowed("U333"));
    }

    #[test]
    fn allowlist_exact_match_not_substring() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec!["U111".into()]);
        assert!(!ch.is_user_allowed("U1111"));
        assert!(!ch.is_user_allowed("U11"));
    }

    #[test]
    fn allowlist_empty_user_id() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec!["U111".into()]);
        assert!(!ch.is_user_allowed(""));
    }

    #[test]
    fn allowlist_case_sensitive() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec!["U111".into()]);
        assert!(ch.is_user_allowed("U111"));
        assert!(!ch.is_user_allowed("u111"));
    }

    #[test]
    fn allowlist_wildcard_and_specific() {
        let ch = SlackChannel::new("xoxb-fake".into(), None, vec!["U111".into(), "*".into()]);
        assert!(ch.is_user_allowed("U111"));
        assert!(ch.is_user_allowed("anyone"));
    }

    // ── Message ID edge cases ─────────────────────────────────────

    #[test]
    fn slack_message_id_format_includes_channel_and_ts() {
        // Verify that message IDs follow the format: slack_{channel_id}_{ts}
        let ts = "1234567890.123456";
        let channel_id = "C12345";
        let expected_id = format!("slack_{channel_id}_{ts}");
        assert_eq!(expected_id, "slack_C12345_1234567890.123456");
    }

    #[test]
    fn slack_message_id_is_deterministic() {
        // Same channel_id + same ts = same ID (prevents duplicates after restart)
        let ts = "1234567890.123456";
        let channel_id = "C12345";
        let id1 = format!("slack_{channel_id}_{ts}");
        let id2 = format!("slack_{channel_id}_{ts}");
        assert_eq!(id1, id2);
    }

    #[test]
    fn slack_message_id_different_ts_different_id() {
        // Different timestamps produce different IDs
        let channel_id = "C12345";
        let id1 = format!("slack_{channel_id}_1234567890.123456");
        let id2 = format!("slack_{channel_id}_1234567890.123457");
        assert_ne!(id1, id2);
    }

    #[test]
    fn slack_message_id_different_channel_different_id() {
        // Different channels produce different IDs even with same ts
        let ts = "1234567890.123456";
        let id1 = format!("slack_C12345_{ts}");
        let id2 = format!("slack_C67890_{ts}");
        assert_ne!(id1, id2);
    }

    #[test]
    fn slack_message_id_no_uuid_randomness() {
        // Verify format doesn't contain random UUID components
        let ts = "1234567890.123456";
        let channel_id = "C12345";
        let id = format!("slack_{channel_id}_{ts}");
        assert!(!id.contains('-')); // No UUID dashes
        assert!(id.starts_with("slack_"));
    }
}