use contract_interface::zgs_flow::MineContext;
use ethereum_types::{H256, U256};
use rand::{self, Rng};
use std::time;
use task_executor::TaskExecutor;
use tokio::sync::{broadcast, mpsc};
use tokio::time::{sleep, Duration, Instant};

use storage::config::ShardConfig;
use zgs_spec::{SECTORS_PER_LOAD, SECTORS_PER_MAX_MINING_RANGE, SECTORS_PER_PRICING};

use crate::recall_range::RecallRange;
use crate::{
    pora::{AnswerWithoutProof, Miner},
    watcher::MineContextMessage,
    MinerConfig, MinerMessage, PoraLoader,
};

use std::sync::Arc;

pub struct PoraService {
    mine_context_receiver: broadcast::Receiver<MineContextMessage>,
    mine_answer_sender: mpsc::UnboundedSender<AnswerWithoutProof>,
    msg_recv: broadcast::Receiver<MinerMessage>,
    loader: Arc<dyn PoraLoader>,

    puzzle: Option<PoraPuzzle>,
    mine_range: MineRangeConfig,
    miner_id: H256,

    cpu_percentage: u64,
    iter_batch: usize,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub(super) struct PoraPuzzle {
    context: MineContext,
    target_quality: U256,
    max_shards: u64,
}

impl PoraPuzzle {
    pub fn new(context: MineContext, target_quality: U256, max_shards: u64) -> Self {
        Self {
            context,
            target_quality,
            max_shards,
        }
    }

    pub fn max_shards(&self) -> u64 {
        self.max_shards
    }

    pub fn context_digest(&self) -> H256 {
        H256(self.context.digest)
    }
}
#[derive(Clone, Debug, Default)]
pub struct MineRangeConfig {
    start_position: Option<u64>,
    end_position: Option<u64>,
    shard_config: ShardConfig,
}

impl MineRangeConfig {
    #[inline]
    fn to_valid_range(&self, context: &MineContext) -> Option<RecallRange> {
        let self_start_position = self.start_position?;
        let self_end_position = self.end_position?;

        if self_start_position >= self_end_position {
            return None;
        }
        let minable_length =
            (context.flow_length.as_u64() / SECTORS_PER_LOAD as u64) * SECTORS_PER_LOAD as u64;

        let num_shards = 1u64 << self.shard_config.miner_shard_mask().count_zeros();
        let mining_length = std::cmp::min(
            minable_length,
            (SECTORS_PER_MAX_MINING_RANGE as u64).saturating_mul(num_shards),
        );

        let start_position = std::cmp::min(self_start_position, minable_length - mining_length);
        let start_position =
            (start_position / SECTORS_PER_PRICING as u64) * SECTORS_PER_PRICING as u64;

        Some(RecallRange {
            start_position,
            mining_length,
            shard_mask: self.shard_config.miner_shard_mask(),
            shard_id: self.shard_config.miner_shard_id(),
        })
    }

    #[inline]
    pub(crate) fn is_covered(&self, recall_position: u64) -> Option<bool> {
        let self_start_position = self.start_position?;
        let self_end_position = self.end_position?;

        if self_start_position >= self_end_position {
            return Some(false);
        }
        Some(
            self_start_position <= recall_position + SECTORS_PER_LOAD as u64
                && self_end_position > recall_position,
        )
    }
}

impl PoraService {
    pub fn spawn(
        executor: TaskExecutor,
        msg_recv: broadcast::Receiver<MinerMessage>,
        mine_context_receiver: broadcast::Receiver<MineContextMessage>,
        loader: Arc<dyn PoraLoader>,
        config: &MinerConfig,
        miner_id: H256,
    ) -> mpsc::UnboundedReceiver<AnswerWithoutProof> {
        let (mine_answer_sender, mine_answer_receiver) =
            mpsc::unbounded_channel::<AnswerWithoutProof>();
        let mine_range = MineRangeConfig {
            start_position: Some(0),
            end_position: Some(u64::MAX),
            shard_config: config.shard_config,
        };
        let pora = PoraService {
            mine_context_receiver,
            mine_answer_sender,
            msg_recv,
            puzzle: None,
            mine_range,
            miner_id,
            loader,
            cpu_percentage: config.cpu_percentage,
            iter_batch: config.iter_batch,
        };
        executor.spawn(async move { Box::pin(pora.start()).await }, "pora_master");
        mine_answer_receiver
    }

    async fn start(mut self) {
        let mut mining_enabled = true;
        let mut channel_opened = true;

        let cpu_percent: u64 = self.cpu_percentage;
        let diastole = sleep(Duration::from_secs(0));
        tokio::pin!(diastole);

        loop {
            tokio::select! {
                biased;

                v = self.msg_recv.recv(), if channel_opened => {
                    trace!("PoraService receives msg={:?}", v);
                    match v {
                        Ok(MinerMessage::ToggleMining(enable)) => {
                            info!("Toggle mining: {}", if enable { "on" } else { "off" });
                            mining_enabled = enable;
                        }
                        Ok(MinerMessage::SetStartPosition(pos)) => {
                            info!("Change start position to: {:?}", pos);
                            self.mine_range.start_position = pos;
                            self.report_reason_if_mine_stop("update mine range");

                        }
                        Ok(MinerMessage::SetEndPosition(pos)) => {
                            info!("Change end position to: {:?}", pos);
                            self.mine_range.end_position = pos;
                            self.report_reason_if_mine_stop("update mine range");
                        }
                        Ok(MinerMessage::SetShardConfig(shard_config)) => {
                            self.mine_range.shard_config = shard_config;
                            self.report_reason_if_mine_stop("update shard");
                        }
                        Err(broadcast::error::RecvError::Closed) => {
                            warn!("Unexpected: Mine service config channel closed.");
                            channel_opened = false;
                        }
                        Err(_)=>{

                        }
                    }
                }

                maybe_msg = self.mine_context_receiver.recv() => {
                    match maybe_msg {
                        Ok(msg) => {
                            info!("Update mine service: {:?}", msg);
                            self.puzzle = msg;
                            self.report_reason_if_mine_stop("update mine context");
                        },
                        Err(broadcast::error::RecvError::Closed) => {
                            warn!("Mine context channel closed.");
                        },
                        Err(_) => {}
                    }
                }

                () = &mut diastole, if !diastole.is_elapsed() => {
                }

                _ = async {}, if mining_enabled
                                && cpu_percent > 0
                                && self.as_miner().is_ok()
                                && diastole.is_elapsed() => {
                    let nonce = H256(rand::thread_rng().gen());
                    let miner = self.as_miner().unwrap();

                    let timer = time::Instant::now();

                    if let Some(answer) = miner.batch_iteration(nonce, self.iter_batch).await {
                        info!("Hit Pora answer {:?}", answer);
                        if self.mine_answer_sender.send(answer).is_err() {
                            warn!("Mine submitter channel closed");
                        }
                    } else if cpu_percent < 100 {
                        // 2^64 ns = 500 years
                        let elapsed = timer.elapsed().as_nanos() as u64;
                        let diastole_time = elapsed / cpu_percent * (100 - cpu_percent);
                        diastole.as_mut().reset(Instant::now() + Duration::from_nanos(diastole_time));
                    }
                }
            }
        }
    }

    #[inline]
    fn as_miner(&self) -> Result<Miner, &'static str> {
        let puzzle = self.puzzle.as_ref().ok_or("no mine context")?;

        let range = self
            .mine_range
            .to_valid_range(&puzzle.context)
            .ok_or("no mine range")?;

        if range.mining_length == 0 {
            return Err("mine range is zero");
        }

        if puzzle.max_shards() < self.mine_range.shard_config.num_shard as u64 {
            return Err("too many mine shards");
        }

        if puzzle.context.flow_length <= U256::one() {
            return Err("no data submitted");
        }

        if self.mine_range.shard_config.num_shard as u64 > puzzle.context.flow_length.as_u64() {
            return Err("Not enough flow length to shard");
        }

        Ok(Miner {
            range,
            miner_id: &self.miner_id,
            mine_range_config: &self.mine_range,
            context: &puzzle.context,
            target_quality: &puzzle.target_quality,
            loader: &*self.loader,
        })
    }

    fn report_reason_if_mine_stop(&self, event: &'static str) {
        if let Err(reason) = self.as_miner() {
            info!(reason, "Mine stopped on {}", event);
        }
    }
}