// TODO: move into separate forester utils crate
use anchor_lang::{
    prelude::borsh, solana_program::pubkey::Pubkey, AnchorDeserialize, AnchorSerialize,
};

use light_registry::{
    protocol_config::state::{EpochState, ProtocolConfig},
    sdk::{create_register_forester_epoch_pda_instruction, create_report_work_instruction},
    utils::{get_epoch_pda_address, get_forester_epoch_pda_from_authority},
    EpochPda, ForesterEpochPda,
};
use solana_sdk::signature::{Keypair, Signature, Signer};

use crate::rpc::{errors::RpcError, rpc_connection::RpcConnection};

// What does the forester need to know?
// What are my public keys (current epoch account, last epoch account, known Merkle trees)
// 1. The current epoch
// 2. When does the next registration start
// 3. When is my turn.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ForesterSlot {
    pub slot: u64,
    pub start_solana_slot: u64,
    pub end_solana_slot: u64,
    pub forester_index: u64,
}

#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub struct Forester {
    pub registration: Epoch,
    pub active: Epoch,
    pub report_work: Epoch,
}

impl Forester {
    pub fn switch_to_report_work(&mut self) {
        self.report_work = self.active.clone();
        self.active = self.registration.clone();
    }

    pub async fn report_work(
        &mut self,
        rpc: &mut impl RpcConnection,
        forester_keypair: &Keypair,
    ) -> Result<Signature, RpcError> {
        let ix = create_report_work_instruction(&forester_keypair.pubkey(), self.report_work.epoch);
        rpc.create_and_send_transaction(&[ix], &forester_keypair.pubkey(), &[forester_keypair])
            .await
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TreeAccounts {
    pub merkle_tree: Pubkey,
    pub queue: Pubkey,
    // TODO: evaluate whether we need
    pub is_rolledover: bool,
    pub tree_type: TreeType,
}

impl TreeAccounts {
    pub fn new(
        merkle_tree: Pubkey,
        queue: Pubkey,
        tree_type: TreeType,
        is_rolledover: bool,
    ) -> Self {
        Self {
            merkle_tree,
            queue,
            tree_type,
            is_rolledover,
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Copy)]
pub enum TreeType {
    Address,
    State,
}

pub fn get_schedule_for_queue(
    mut start_solana_slot: u64,
    queue_pubkey: &Pubkey,
    protocol_config: &ProtocolConfig,
    total_epoch_weight: u64,
    epoch: u64,
) -> Vec<Option<ForesterSlot>> {
    let mut vec = Vec::new();
    let start_slot = 0;
    // TODO: enforce that active_phase_length is a multiple of slot_length
    let end_slot = start_slot + (protocol_config.active_phase_length / protocol_config.slot_length);

    for light_slot in start_slot..end_slot {
        let forester_index = ForesterEpochPda::get_eligible_forester_index(
            light_slot,
            queue_pubkey,
            total_epoch_weight,
            epoch,
        )
        .unwrap();
        vec.push(Some(ForesterSlot {
            slot: light_slot,
            start_solana_slot,
            end_solana_slot: start_solana_slot + protocol_config.slot_length,
            forester_index,
        }));
        start_solana_slot += protocol_config.slot_length;
    }
    vec
}

pub fn get_schedule_for_forester_in_queue(
    start_solana_slot: u64,
    queue_pubkey: &Pubkey,
    total_epoch_weight: u64,
    forester_epoch_pda: &ForesterEpochPda,
) -> Vec<Option<ForesterSlot>> {
    let mut slots = get_schedule_for_queue(
        start_solana_slot,
        queue_pubkey,
        &forester_epoch_pda.protocol_config,
        total_epoch_weight,
        forester_epoch_pda.epoch,
    );
    slots.iter_mut().for_each(|x| {
        // TODO: remove unwrap
        if forester_epoch_pda.is_eligible(x.as_ref().unwrap().forester_index) {
        } else {
            *x = None;
        }
    });
    slots
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct TreeForesterSchedule {
    pub tree_accounts: TreeAccounts,
    /// Vec with the slots that the forester is eligible to perform work.
    /// Non eligible slots are None.
    pub slots: Vec<Option<ForesterSlot>>,
}

impl TreeForesterSchedule {
    pub fn new(tree_accounts: TreeAccounts) -> Self {
        Self {
            tree_accounts,
            slots: Vec::new(),
        }
    }

    pub fn new_with_schedule(
        tree_accounts: &TreeAccounts,
        solana_slot: u64,
        forester_epoch_pda: &ForesterEpochPda,
    ) -> Self {
        let mut _self = Self {
            tree_accounts: *tree_accounts,
            slots: Vec::new(),
        };
        _self.slots = get_schedule_for_forester_in_queue(
            solana_slot,
            &_self.tree_accounts.queue,
            forester_epoch_pda.total_epoch_weight.unwrap(),
            forester_epoch_pda,
        );
        _self
    }

    pub fn is_eligible(&self, forester_slot: u64) -> bool {
        self.slots[forester_slot as usize].is_some()
    }
}

#[derive(Debug, Clone, AnchorSerialize, AnchorDeserialize, Default, PartialEq, Eq)]
pub struct EpochPhases {
    pub registration: Phase,
    pub active: Phase,
    pub report_work: Phase,
    pub post: Phase,
}

impl EpochPhases {
    pub fn get_current_phase(&self, current_slot: u64) -> Phase {
        if current_slot >= self.registration.start && current_slot <= self.registration.end {
            self.registration.clone()
        } else if current_slot >= self.active.start && current_slot <= self.active.end {
            self.active.clone()
        } else if current_slot >= self.report_work.start && current_slot <= self.report_work.end {
            self.report_work.clone()
        } else {
            self.post.clone()
        }
    }
    pub fn get_current_epoch_state(&self, current_slot: u64) -> EpochState {
        if current_slot >= self.registration.start && current_slot <= self.registration.end {
            EpochState::Registration
        } else if current_slot >= self.active.start && current_slot <= self.active.end {
            EpochState::Active
        } else if current_slot >= self.report_work.start && current_slot <= self.report_work.end {
            EpochState::ReportWork
        } else {
            EpochState::Post
        }
    }
}

#[derive(Debug, Clone, AnchorSerialize, AnchorDeserialize, Default, PartialEq, Eq)]
pub struct Phase {
    pub start: u64,
    pub end: u64,
}

pub fn get_epoch_phases(protocol_config: &ProtocolConfig, epoch: u64) -> EpochPhases {
    let epoch_start_slot = protocol_config
        .genesis_slot
        .saturating_add(epoch.saturating_mul(protocol_config.active_phase_length));

    let registration_start = epoch_start_slot;
    let registration_end = registration_start
        .saturating_add(protocol_config.registration_phase_length)
        .saturating_sub(1);

    let active_start = registration_end.saturating_add(1);
    let active_end = active_start
        .saturating_add(protocol_config.active_phase_length)
        .saturating_sub(1);

    let report_work_start = active_end.saturating_add(1);
    let report_work_end = report_work_start
        .saturating_add(protocol_config.report_work_phase_length)
        .saturating_sub(1);

    let post_start = report_work_end.saturating_add(1);
    let post_end = u64::MAX;

    EpochPhases {
        registration: Phase {
            start: registration_start,
            end: registration_end,
        },
        active: Phase {
            start: active_start,
            end: active_end,
        },
        report_work: Phase {
            start: report_work_start,
            end: report_work_end,
        },
        post: Phase {
            start: post_start,
            end: post_end,
        },
    }
}

#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct Epoch {
    pub epoch: u64,
    pub epoch_pda: Pubkey,
    pub forester_epoch_pda: Pubkey,
    pub phases: EpochPhases,
    pub state: EpochState,
    pub merkle_trees: Vec<TreeForesterSchedule>,
}

#[derive(Debug, Clone, AnchorSerialize, AnchorDeserialize, Default, PartialEq, Eq)]
pub struct EpochRegistration {
    pub epoch: u64,
    pub slots_until_registration_starts: u64,
    pub slots_until_registration_ends: u64,
}

impl Epoch {
    /// returns slots until next epoch and that epoch
    /// registration is open if
    pub async fn slots_until_next_epoch_registration<R: RpcConnection>(
        rpc: &mut R,
        protocol_config: &ProtocolConfig,
    ) -> Result<EpochRegistration, RpcError> {
        let current_solana_slot = rpc.get_slot().await?;

        let mut epoch = protocol_config
            .get_latest_register_epoch(current_solana_slot)
            .unwrap();
        let registration_start_slot =
            protocol_config.genesis_slot + epoch * protocol_config.active_phase_length;

        let registration_end_slot =
            registration_start_slot + protocol_config.registration_phase_length;
        if current_solana_slot > registration_end_slot {
            epoch += 1;
        }
        let next_registration_start_slot =
            protocol_config.genesis_slot + epoch * protocol_config.active_phase_length;
        let next_registration_end_slot =
            next_registration_start_slot + protocol_config.registration_phase_length;
        let slots_until_registration_ends =
            next_registration_end_slot.saturating_sub(current_solana_slot);
        let slots_until_registration_starts =
            next_registration_start_slot.saturating_sub(current_solana_slot);
        Ok(EpochRegistration {
            epoch,
            slots_until_registration_starts,
            slots_until_registration_ends,
        })
    }

    /// creates forester account and fetches epoch account
    pub async fn register<R: RpcConnection>(
        rpc: &mut R,
        protocol_config: &ProtocolConfig,
        authority: &Keypair,
    ) -> Result<Option<Epoch>, RpcError> {
        let epoch_registration =
            Self::slots_until_next_epoch_registration(rpc, protocol_config).await?;
        if epoch_registration.slots_until_registration_starts > 0
            || epoch_registration.slots_until_registration_ends == 0
        {
            return Ok(None);
        }

        let instruction = create_register_forester_epoch_pda_instruction(
            &authority.pubkey(),
            epoch_registration.epoch,
        );
        let signature = rpc
            .create_and_send_transaction(&[instruction], &authority.pubkey(), &[authority])
            .await?;
        rpc.confirm_transaction(signature).await?;
        let epoch_pda_pubkey = get_epoch_pda_address(epoch_registration.epoch);
        let epoch_pda = rpc
            .get_anchor_account::<EpochPda>(&epoch_pda_pubkey)
            .await?
            .unwrap();
        let forester_epoch_pda_pubkey =
            get_forester_epoch_pda_from_authority(&authority.pubkey(), epoch_registration.epoch).0;

        let phases = get_epoch_phases(protocol_config, epoch_pda.epoch);
        Ok(Some(Self {
            // epoch: epoch_registration.epoch,
            epoch_pda: epoch_pda_pubkey,
            forester_epoch_pda: forester_epoch_pda_pubkey,
            merkle_trees: Vec::new(),
            epoch: epoch_pda.epoch,
            state: phases.get_current_epoch_state(rpc.get_slot().await?),
            phases,
        }))
    }
    // TODO: implement
    /// forester account and epoch account already exist
    /// -> fetch accounts and init
    pub fn fetch_registered() {}

    pub async fn fetch_account_and_add_trees_with_schedule<R: RpcConnection>(
        &mut self,
        rpc: &mut R,
        trees: &[TreeAccounts],
    ) -> Result<(), RpcError> {
        let current_solana_slot = rpc.get_slot().await?;

        if self.phases.active.end < current_solana_slot
            || self.phases.active.start > current_solana_slot
        {
            println!("current_solana_slot {:?}", current_solana_slot);
            println!("registration phase {:?}", self.phases.registration);
            println!("active phase {:?}", self.phases.active);
            // return Err(RpcError::EpochNotActive);
            panic!("TODO: throw epoch not active error");
        }
        let epoch_pda = rpc
            .get_anchor_account::<EpochPda>(&self.epoch_pda)
            .await?
            .unwrap();
        let mut forester_epoch_pda = rpc
            .get_anchor_account::<ForesterEpochPda>(&self.forester_epoch_pda)
            .await?
            .unwrap();
        // IF active phase has started and total_epoch_weight is not set, set it now to
        if forester_epoch_pda.total_epoch_weight.is_none() {
            forester_epoch_pda.total_epoch_weight = Some(epoch_pda.registered_weight);
        }
        self.add_trees_with_schedule(&forester_epoch_pda, trees, current_solana_slot);
        Ok(())
    }
    /// Internal function to init Epoch struct with registered account
    /// 1. calculate epoch phases
    /// 2. set current epoch state
    /// 3. derive tree schedule for all input trees
    pub fn add_trees_with_schedule(
        &mut self,
        forester_epoch_pda: &ForesterEpochPda,
        trees: &[TreeAccounts],
        current_solana_slot: u64,
    ) {
        // let state = self.phases.get_current_epoch_state(current_solana_slot);
        // TODO: add epoch state to sync schedule
        for tree in trees {
            let tree_schedule = TreeForesterSchedule::new_with_schedule(
                tree,
                current_solana_slot,
                forester_epoch_pda,
            );
            self.merkle_trees.push(tree_schedule);
        }
    }

    pub fn update_state(&mut self, current_solana_slot: u64) -> EpochState {
        let current_state = self.phases.get_current_epoch_state(current_solana_slot);
        if current_state != self.state {
            self.state = current_state.clone();
        }
        current_state
    }

    /// execute active phase test:
    /// (multi thread)
    /// - iterate over all trees, check whether eligible and empty queues
    ///
    /// forester:
    /// - start a new thread per tree
    /// - this thread will sleep when it is not elibile and wake up with
    ///   some buffer time prior to the start of the slot
    /// - threads shut down when the active phase ends
    pub fn execute_active_phase() {}

    /// report work phase:
    /// (single thread)
    /// - free Merkle tree memory
    /// - execute report work tx (single thread)
    pub fn execute_report_work_phase() {}
    /// post phase:
    /// (single thread)
    /// - claim rewards
    /// - close forester epoch account
    pub fn execute_post_phase() {}
}

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

    #[test]
    fn test_epoch_phases() {
        let config = ProtocolConfig {
            genesis_slot: 200,
            min_weight: 0,
            slot_length: 10,
            registration_phase_length: 100,
            active_phase_length: 1000,
            report_work_phase_length: 100,
            network_fee: 5000,
            ..Default::default()
        };

        let epoch = 1;
        let phases = get_epoch_phases(&config, epoch);

        assert_eq!(phases.registration.start, 1200);
        assert_eq!(phases.registration.end, 1299);

        assert_eq!(phases.active.start, 1300);
        assert_eq!(phases.active.end, 2299);

        assert_eq!(phases.report_work.start, 2300);
        assert_eq!(phases.report_work.end, 2399);

        assert_eq!(phases.post.start, 2400);
        assert_eq!(phases.post.end, u64::MAX);
    }

    #[test]
    fn test_get_schedule_for_queue() {
        let protocol_config = ProtocolConfig {
            genesis_slot: 0,
            min_weight: 100,
            slot_length: 10,
            registration_phase_length: 100,
            active_phase_length: 1000,
            report_work_phase_length: 100,
            network_fee: 5000,
            ..Default::default()
        };

        let total_epoch_weight = 500;
        let queue_pubkey = Pubkey::new_unique();
        let start_solana_slot = 0;
        let epoch = 0;

        let schedule = get_schedule_for_queue(
            start_solana_slot,
            &queue_pubkey,
            &protocol_config,
            total_epoch_weight,
            epoch,
        );

        assert_eq!(
            schedule.len(),
            (protocol_config.active_phase_length / protocol_config.slot_length) as usize
        );

        for (i, slot_option) in schedule.iter().enumerate() {
            let slot = slot_option.as_ref().unwrap();
            assert_eq!(slot.slot, i as u64);
            assert_eq!(
                slot.start_solana_slot,
                start_solana_slot + (i as u64 * protocol_config.slot_length)
            );
            assert_eq!(
                slot.end_solana_slot,
                slot.start_solana_slot + protocol_config.slot_length
            );
            assert!(slot.forester_index < total_epoch_weight);
        }
    }
}