use std::time::Duration;

use futures_util::StreamExt;
use lapin::{
    options::{
        BasicAckOptions, BasicConsumeOptions, BasicNackOptions, BasicPublishOptions, BasicQosOptions,
        ConfirmSelectOptions, ExchangeDeclareOptions, QueueBindOptions, QueueDeclareOptions, BasicCancelOptions,
    },
    types::{AMQPValue, FieldTable, LongString, ShortString},
    BasicProperties, Channel, Connection, ConnectionProperties, Consumer,
};
use miette::{IntoDiagnostic as _, Result};
use tracing::{debug, error, info, instrument, warn};
use tracing::Instrument;

use crate::messages::JobRequest;

#[derive(Clone, Debug)]
pub struct MqConfig {
    pub url: String,
    pub exchange: String,
    pub routing_key: String,
    pub queue: String,
    pub dlx: String,
    pub dlq: String,
    pub prefetch: u16,
}

impl Default for MqConfig {
    fn default() -> Self {
        Self {
            url: std::env::var("AMQP_URL").unwrap_or_else(|_| "amqp://127.0.0.1:5672/%2f".into()),
            exchange: std::env::var("AMQP_EXCHANGE").unwrap_or_else(|_| "solstice.jobs".into()),
            routing_key: std::env::var("AMQP_ROUTING_KEY").unwrap_or_else(|_| "jobrequest.v1".into()),
            queue: std::env::var("AMQP_QUEUE").unwrap_or_else(|_| "solstice.jobs.v1".into()),
            dlx: std::env::var("AMQP_DLX").unwrap_or_else(|_| "solstice.dlx".into()),
            dlq: std::env::var("AMQP_DLQ").unwrap_or_else(|_| "solstice.jobs.v1.dlq".into()),
            prefetch: std::env::var("AMQP_PREFETCH").ok().and_then(|s| s.parse().ok()).unwrap_or(64),
        }
    }
}

#[instrument(skip(cfg))]
pub async fn connect(cfg: &MqConfig) -> Result<Connection> {
    Connection::connect(&cfg.url, ConnectionProperties::default())
        .await
        .into_diagnostic()
}

#[instrument(skip(channel, cfg))]
pub async fn declare_topology(channel: &Channel, cfg: &MqConfig) -> Result<()> {
    // Declare main exchange (durable direct)
    channel
        .exchange_declare(
            &cfg.exchange,
            lapin::ExchangeKind::Direct,
            ExchangeDeclareOptions {
                durable: true,
                auto_delete: false,
                internal: false,
                nowait: false,
                passive: false,
            },
            FieldTable::default(),
        )
        .await
        .into_diagnostic()?;

    // Declare DLX
    channel
        .exchange_declare(
            &cfg.dlx,
            lapin::ExchangeKind::Fanout,
            ExchangeDeclareOptions { durable: true, auto_delete: false, internal: false, nowait: false, passive: false },
            FieldTable::default(),
        )
        .await
        .into_diagnostic()?;

    // Declare DLQ with dead-lettering from main queue
    let mut dlq_args = FieldTable::default();
    dlq_args.insert(
        ShortString::from("x-dead-letter-exchange"),
        AMQPValue::LongString(LongString::from(cfg.exchange.clone())),
    );
    channel
        .queue_declare(
            &cfg.dlq,
            QueueDeclareOptions { durable: true, auto_delete: false, exclusive: false, nowait: false, passive: false },
            dlq_args,
        )
        .await
        .into_diagnostic()?;

    // Bind DLQ to DLX (fanout)
    channel
        .queue_bind(
            &cfg.dlq,
            &cfg.dlx,
            "",
            QueueBindOptions { nowait: false },
            FieldTable::default(),
        )
        .await
        .into_diagnostic()?;

    // Declare main queue with DLX
    let mut q_args = FieldTable::default();
    q_args.insert(
        ShortString::from("x-dead-letter-exchange"),
        AMQPValue::LongString(LongString::from(cfg.dlx.clone())),
    );
    channel
        .queue_declare(
            &cfg.queue,
            QueueDeclareOptions { durable: true, auto_delete: false, exclusive: false, nowait: false, passive: false },
            q_args,
        )
        .await
        .into_diagnostic()?;

    // Bind queue
    channel
        .queue_bind(
            &cfg.queue,
            &cfg.exchange,
            &cfg.routing_key,
            QueueBindOptions { nowait: false },
            FieldTable::default(),
        )
        .await
        .into_diagnostic()?;

    Ok(())
}

#[instrument(skip(cfg, job))]
pub async fn publish_job(cfg: &MqConfig, job: &JobRequest) -> Result<()> {
    let conn = connect(cfg).await?;
    let channel = conn.create_channel().await.into_diagnostic()?;

    declare_topology(&channel, cfg).await?;

    // Enable publisher confirms
    channel
        .confirm_select(ConfirmSelectOptions::default())
        .await
        .into_diagnostic()?;

    let payload = serde_json::to_vec(job).into_diagnostic()?;

    let props = BasicProperties::default()
        .with_content_type("application/json".into())
        .with_content_encoding("utf-8".into())
        .with_type(ShortString::from(job.schema_version.clone()))
        .with_delivery_mode(2u8.into()); // persistent

    let confirm = channel
        .basic_publish(
            &cfg.exchange,
            &cfg.routing_key,
            BasicPublishOptions { mandatory: true, ..Default::default() },
            &payload,
            props,
        )
        .await
        .into_diagnostic()?;

    // Wait for broker confirm
    confirm.await.into_diagnostic()?;
    Ok(())
}

pub struct DeliveryMeta {
    pub delivery_tag: u64,
}

#[instrument(skip(cfg, handler))]
pub async fn consume_jobs<F, Fut>(cfg: &MqConfig, handler: F) -> Result<()>
where
    F: Fn(JobRequest) -> Fut + Send + Sync + 'static,
    Fut: std::future::Future<Output = Result<()>> + Send + 'static,
{
    // Backward-compatible wrapper that runs until process exit (no cooperative shutdown)
    consume_jobs_until(cfg, futures_util::future::pending(), handler).await
}

#[instrument(skip(cfg, shutdown, handler))]
pub async fn consume_jobs_until<F, Fut, S>(cfg: &MqConfig, shutdown: S, handler: F) -> Result<()>
where
    F: Fn(JobRequest) -> Fut + Send + Sync + 'static,
    Fut: std::future::Future<Output = Result<()>> + Send + 'static,
    S: std::future::Future<Output = ()> + Send + 'static,
{
    let conn = connect(cfg).await?;
    let channel = conn.create_channel().await.into_diagnostic()?;
    declare_topology(&channel, cfg).await?;

    // Set QoS
    channel
        .basic_qos(cfg.prefetch, BasicQosOptions { global: false })
        .await
        .into_diagnostic()?;

    let consumer: Consumer = channel
        .basic_consume(
            &cfg.queue,
            "orchestrator",
            BasicConsumeOptions { no_ack: false, ..Default::default() },
            FieldTable::default(),
        )
        .await
        .into_diagnostic()?;

    info!(queue = %cfg.queue, prefetch = cfg.prefetch, "consumer started");

    tokio::pin!(consumer);
    let mut shutdown = Box::pin(shutdown);

    loop {
        tokio::select! {
            _ = &mut shutdown => {
                info!("shutdown requested; canceling consumer");
                // Best-effort cancel; ignore errors during shutdown.
                let _ = channel.basic_cancel("orchestrator", BasicCancelOptions { nowait: false }).await;
                break;
            }
            maybe_delivery = consumer.next() => {
                match maybe_delivery {
                    Some(Ok(d)) => {
                        let tag = d.delivery_tag;
                        match serde_json::from_slice::<JobRequest>(&d.data) {
                            Ok(job) => {
                                let span = tracing::info_span!("handle_job", request_id = %job.request_id, repo = %job.repo_url, sha = %job.commit_sha);
                                if let Err(err) = handler(job).instrument(span).await {
                                    error!(error = %err, "handler error; nacking to DLQ");
                                    channel
                                        .basic_nack(tag, BasicNackOptions { requeue: false, multiple: false })
                                        .await
                                        .into_diagnostic()?;
                                } else {
                                    channel
                                        .basic_ack(tag, BasicAckOptions { multiple: false })
                                        .await
                                        .into_diagnostic()?;
                                }
                            }
                            Err(e) => {
                                warn!(error = %e, "failed to deserialize JobRequest; dead-lettering");
                                channel
                                    .basic_nack(tag, BasicNackOptions { requeue: false, multiple: false })
                                    .await
                                    .into_diagnostic()?;
                            }
                        }
                    }
                    Some(Err(e)) => {
                        error!(error = %e, "consumer delivery error; continuing");
                        tokio::time::sleep(Duration::from_millis(200)).await;
                    }
                    None => {
                        // Stream ended; exit loop.
                        break;
                    }
                }
            }
        }
    }

    Ok(())
}