use std::time::Duration;

use async_nats::jetstream::consumer::AckPolicy;
use async_nats::jetstream::consumer::pull::Config as PullConfig;
use async_nats::jetstream::consumer::push::Config as PushConfig;
use async_nats::jetstream::consumer::push::Messages;
use futures_util::StreamExt;
use serde::de::DeserializeOwned;

use crate::error::{AppError, AppResult};

use super::NatsQueue;

pub struct NatsMessage {
    inner: async_nats::jetstream::Message,
}

impl NatsMessage {
    pub fn subject(&self) -> &str {
        self.inner.message.subject.as_str()
    }

    pub fn payload(&self) -> &[u8] {
        &self.inner.message.payload
    }

    pub fn payload_json<T: DeserializeOwned>(&self) -> AppResult<T> {
        serde_json::from_slice(&self.inner.message.payload).map_err(AppError::from)
    }

    pub fn headers(&self) -> Option<&async_nats::HeaderMap> {
        self.inner.message.headers.as_ref()
    }

    pub async fn ack(self) -> AppResult<()> {
        self.inner
            .ack()
            .await
            .map_err(|e| AppError::Config(format!("ack failed: {e}")))
    }

    pub async fn nack(self) -> AppResult<()> {
        self.inner
            .ack_with(async_nats::jetstream::AckKind::Nak(None))
            .await
            .map_err(|e| AppError::Config(format!("nack failed: {e}")))
    }

    pub async fn nack_with_delay(self, delay: Duration) -> AppResult<()> {
        self.inner
            .ack_with(async_nats::jetstream::AckKind::Nak(Some(delay)))
            .await
            .map_err(|e| AppError::Config(format!("nack with delay failed: {e}")))
    }

    pub async fn ack_in_progress(&self) -> AppResult<()> {
        self.inner
            .ack_with(async_nats::jetstream::AckKind::Progress)
            .await
            .map_err(|e| AppError::Config(format!("ack in progress failed: {e}")))
    }

    pub async fn term(self) -> AppResult<()> {
        self.inner
            .ack_with(async_nats::jetstream::AckKind::Term)
            .await
            .map_err(|e| AppError::Config(format!("term failed: {e}")))
    }
}

pub struct PullSubscription {
    stream: async_nats::jetstream::stream::Stream,
    consumer_name: String,
}

impl NatsQueue {
    pub async fn subscribe_broadcast(
        &self,
        stream_name: &str,
        consumer_name: &str,
        filter_subject: Option<&str>,
    ) -> AppResult<Messages> {
        let full_stream = self.stream_name(stream_name);
        let stream = self
            .inner
            .js
            .get_stream(&full_stream)
            .await
            .map_err(|e| AppError::Config(format!("get stream {full_stream} failed: {e}")))?;

        let deliver_subject = format!(
            "deliver.{}.{}.{}",
            self.inner.stream_prefix, stream_name, consumer_name
        );

        let config = PushConfig {
            durable_name: Some(consumer_name.to_string()),
            deliver_subject,
            deliver_group: Some(consumer_name.to_string()),
            ack_policy: AckPolicy::Explicit,
            ack_wait: self.inner.ack_wait,
            max_deliver: self.inner.max_deliver,
            filter_subject: filter_subject.unwrap_or(">").to_string(),
            ..Default::default()
        };

        let consumer = stream
            .get_or_create_consumer(consumer_name, config)
            .await
            .map_err(|e| {
                AppError::Config(format!("create push consumer {consumer_name} failed: {e}"))
            })?;

        let messages = consumer.messages().await.map_err(|e| {
            AppError::Config(format!("subscribe broadcast {consumer_name} failed: {e}"))
        })?;

        Ok(messages)
    }

    pub async fn create_pull_consumer(
        &self,
        stream_name: &str,
        consumer_name: &str,
        filter_subject: Option<&str>,
        max_batch: usize,
    ) -> AppResult<PullSubscription> {
        let full_stream = self.stream_name(stream_name);
        let stream = self
            .inner
            .js
            .get_stream(&full_stream)
            .await
            .map_err(|e| AppError::Config(format!("get stream {full_stream} failed: {e}")))?;

        let mut config = PullConfig {
            durable_name: Some(consumer_name.to_string()),
            ack_policy: AckPolicy::Explicit,
            ack_wait: self.inner.ack_wait,
            max_deliver: self.inner.max_deliver,
            max_ack_pending: max_batch as i64,
            ..Default::default()
        };

        if let Some(subject) = filter_subject {
            config.filter_subject = subject.to_string();
        }

        stream
            .get_or_create_consumer(consumer_name, config)
            .await
            .map_err(|e| {
                AppError::Config(format!("create pull consumer {consumer_name} failed: {e}"))
            })?;

        Ok(PullSubscription {
            stream,
            consumer_name: consumer_name.to_string(),
        })
    }

    pub async fn fetch(
        &self,
        subscription: &PullSubscription,
        batch_size: usize,
    ) -> AppResult<Vec<NatsMessage>> {
        let consumer = subscription
            .stream
            .get_consumer(&subscription.consumer_name)
            .await
            .map_err(|e| AppError::Config(format!("get consumer failed: {e}")))?;

        let mut messages = consumer
            .fetch()
            .max_messages(batch_size)
            .messages()
            .await
            .map_err(|e| AppError::Config(format!("fetch failed: {e}")))?;

        let mut result = Vec::with_capacity(batch_size);
        while let Some(msg) = messages.next().await {
            match msg {
                Ok(m) => result.push(NatsMessage { inner: m }),
                Err(e) => {
                    tracing::warn!(error = %e, "fetch message error");
                    break;
                }
            }
        }
        Ok(result)
    }

    pub async fn subscribe_ephemeral(&self, subject: String) -> AppResult<async_nats::Subscriber> {
        let sub = self
            .inner
            .client
            .subscribe(subject.clone())
            .await
            .map_err(|e| AppError::Config(format!("subscribe ephemeral {subject} failed: {e}")))?;
        Ok(sub)
    }
}