// This file is part of Gear.

// Copyright (C) 2022-2024 Gear Technologies Inc.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

use super::{GearApi, Result};
use crate::Error;
use gsdk::{config::Header, ext::sp_core::H256, metadata::vara_runtime::RuntimeEvent};
use subxt::config::Header as _;

type GearBlock = Header;

impl GearApi {
    /// Return the total gas limit per block (also known as a gas budget).
    pub fn block_gas_limit(&self) -> Result<u64> {
        self.0.api().gas_limit().map_err(Into::into)
    }

    /// The expected average block time at which BABE should be creating blocks.
    ///
    /// Since BABE is probabilistic it is not trivial to figure out what the
    /// expected average block time should be based on the slot duration and the
    /// security parameter `c` (where `1 - c` represents the probability of a
    /// slot being empty).
    pub fn expected_block_time(&self) -> Result<u64> {
        self.0.api().expected_block_time().map_err(Into::into)
    }

    // Get block data
    async fn get_block_at(&self, block_hash: Option<H256>) -> Result<GearBlock> {
        let hash = if let Some(hash) = block_hash {
            hash
        } else {
            self.0
                .api()
                .backend()
                .latest_finalized_block_ref()
                .await?
                .hash()
        };

        self.0
            .api()
            .backend()
            .block_header(hash)
            .await?
            .ok_or(Error::BlockDataNotFound)
    }

    /// Return a hash of the last block.
    pub async fn last_block_hash(&self) -> Result<H256> {
        Ok(self.get_block_at(None).await?.hash())
    }

    /// Return a number of the last block (also known as block height).
    pub async fn last_block_number(&self) -> Result<u32> {
        Ok(self.get_block_at(None).await?.number())
    }

    /// Return vector of events contained in the last block.
    pub async fn last_events(&self) -> Result<Vec<RuntimeEvent>> {
        self.0.api().get_events_at(None).await.map_err(Into::into)
    }

    /// Return a number of the specified block identified by the `block_hash`.
    pub async fn block_number_at(&self, block_hash: H256) -> Result<u32> {
        Ok(self.get_block_at(Some(block_hash)).await?.number())
    }

    /// Get a hash of a block identified by its `block_number`.
    pub async fn get_block_hash(&self, block_number: u32) -> Result<H256> {
        self.0
            .api()
            .rpc()
            .chain_get_block_hash(Some(block_number.into()))
            .await?
            .ok_or(Error::BlockHashNotFound)
    }

    /// Return a timestamp of the last block.
    ///
    /// The timestamp is the number of milliseconds elapsed since the Unix
    /// epoch.
    pub async fn last_block_timestamp(&self) -> Result<u64> {
        self.0
            .api()
            .block_timestamp(None)
            .await
            .map_err(|_| Error::TimestampNotFound)
    }

    /// Return vector of events contained in the specified block identified by
    /// the `block_hash`.
    pub async fn events_at(&self, block_hash: H256) -> Result<Vec<RuntimeEvent>> {
        self.0
            .api()
            .get_events_at(block_hash)
            .await
            .map_err(Into::into)
    }

    /// Return vector of events contained in blocks since the block identified
    /// by the `block_hash` but no more than in `max_depth` blocks.
    pub async fn events_since(
        &self,
        block_hash: H256,
        max_depth: usize,
    ) -> Result<Vec<RuntimeEvent>> {
        let mut block_hashes = Vec::with_capacity(max_depth);

        let mut current = self.get_block_at(None).await?;
        for _ in 0..max_depth {
            let current_hash = current.hash();
            block_hashes.push(current_hash);

            if current_hash == block_hash {
                break;
            }

            current = self.get_block_at(Some(current.parent_hash)).await?;
        }

        if block_hashes.contains(&block_hash) {
            let mut events = vec![];

            for hash in block_hashes.into_iter() {
                events.append(self.events_at(hash).await?.as_mut());
            }

            Ok(events)
        } else {
            Err(Error::MaxDepthReached)
        }
    }

    /// Check whether the message queue processing is stopped or not.
    pub async fn queue_processing_enabled(&self) -> Result<bool> {
        self.0.api().execute_inherent().await.map_err(Into::into)
    }

    /// Looks at two blocks from the stream and checks if the Gear block number
    /// has grown from block to block or not.
    pub async fn queue_processing_stalled(&self) -> Result<bool> {
        let mut listener = self.subscribe().await?;

        let current = listener.next_block_hash().await?;
        let gear_current = self.0.api().gear_block_number(Some(current)).await?;

        let mut next = current;
        while next == current {
            next = listener.next_block_hash().await?;
        }
        let gear_next = self.0.api().gear_block_number(Some(next)).await?;

        Ok(gear_next <= gear_current)
    }
}