/*
  This file is part of TALER
  Copyright (C) 2022 Taler Systems SA

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

  TALER 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 Affero General Public License for more details.

  You should have received a copy of the GNU Affero General Public License along with
  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
*/
use std::{
    collections::HashMap,
    fmt::Write,
    time::{Duration, SystemTime},
};

use bitcoin::{hashes::Hash, Amount as BtcAmount, BlockHash, Txid};
use btc_wire::{
    rpc::{self, AutoRpcWallet, Category, ErrorCode, Rpc, Transaction},
    rpc_utils::sender_address,
    taler_utils::{btc_payto_url, btc_to_taler},
    GetOpReturnErr, GetSegwitErr,
};
use common::{
    api_common::base32,
    log::{
        log::{error, info, warn},
        OrFail,
    },
    metadata::OutMetadata,
    postgres,
    reconnect::AutoReconnectDb,
    sql::{sql_array, sql_url},
    status::{BounceStatus, DebitStatus},
};
use postgres::{fallible_iterator::FallibleIterator, Client};

use crate::{
    fail_point::fail_point,
    sql::{sql_addr, sql_btc_amount, sql_txid},
    WireState,
};

use super::{analysis::analysis, LoopError, LoopResult};

/// Synchronize local db with blockchain and perform transactions
pub fn worker(mut rpc: AutoRpcWallet, mut db: AutoReconnectDb, mut state: WireState) {
    let mut lifetime = state.lifetime;
    let mut status = true;
    let mut skip_notification = false;

    loop {
        // Check lifetime
        if let Some(nb) = lifetime.as_mut() {
            if *nb == 0 {
                info!("Reach end of lifetime");
                return;
            } else {
                *nb -= 1;
            }
        }

        // Connect
        let rpc = rpc.client();
        let db = db.client();

        let result: LoopResult<()> = (|| {
            // Listen to all channels
            db.batch_execute("LISTEN new_block; LISTEN new_tx")?;
            // Wait for the next notification
            {
                let mut ntf = db.notifications();
                if !skip_notification && ntf.is_empty() {
                    // Block until next notification
                    ntf.blocking_iter().next()?;
                }
                // Conflate all notifications
                let mut iter = ntf.iter();
                while iter.next()?.is_some() {}
            }

            // It is not possible to atomically update the blockchain and the database.
            // When we failed to sync the database and the blockchain state we rely on
            // sync_chain to recover the lost updates.
            // When this function is running concurrently, it not possible to known another
            // execution has failed, and this can lead to a transaction being sent multiple time.
            // To ensure only a single version of this function is running at a given time we rely
            // on postgres advisory lock

            // Take the lock
            let row = db.query_one("SELECT pg_try_advisory_lock(42)", &[])?;
            let locked: bool = row.get(0);
            if !locked {
                return Err(LoopError::Concurrency);
            }

            // Perform analysis
            state.confirmation = analysis(rpc, state.confirmation, state.max_confirmation)?;

            // Sync chain
            if let Some(stuck) = sync_chain(rpc, db, &state, &mut status)? {
                // As we are now in sync with the blockchain if a transaction has Requested status it have not been sent

                // Send requested debits
                while debit(db, rpc, &state)? {}

                // Bump stuck transactions
                for id in stuck {
                    let bump = rpc.bump_fee(&id)?;
                    fail_point("(injected) fail bump", 0.3)?;
                    let row = db.query_one(
                        "UPDATE tx_out SET txid=$1 WHERE txid=$2 RETURNING wtid",
                        &[
                            &bump.txid.as_byte_array().as_slice(),
                            &id.as_byte_array().as_slice(),
                        ],
                    )?;
                    info!(
                        ">> (bump) {} replace {} with {}",
                        base32(row.get(0)),
                        id,
                        bump.txid
                    );
                }

                // Send requested bounce
                while bounce(db, rpc, &state.bounce_fee)? {}
            }

            Ok(())
        })();
        if let Err(e) = result {
            error!("worker: {}", e);
            // When we catch an error, we sometimes want to retry immediately (eg. reconnect to RPC or DB).
            // Bitcoin error codes are generic. We need to match the msg to get precise ones. Some errors
            // can resolve themselves when a new block is mined (new fees, new transactions). Our simple
            // approach is to wait for the next loop when an RPC error is caught to prevent endless logged errors.
            skip_notification = !matches!(
                e,
                LoopError::Rpc(rpc::Error::RPC { .. } | rpc::Error::Bitcoin(_))
                    | LoopError::Concurrency
            );
        } else {
            skip_notification = false;
        }
    }
}

/// Retrieve last stored hash
fn last_hash(db: &mut Client) -> Result<BlockHash, postgres::Error> {
    let row = db.query_one("SELECT value FROM state WHERE name='last_hash'", &[])?;
    Ok(BlockHash::from_slice(row.get(0)).unwrap())
}

/// Parse new transactions, return stuck transactions if the database is up to date with the latest mined block
fn sync_chain(
    rpc: &mut Rpc,
    db: &mut Client,
    state: &WireState,
    status: &mut bool,
) -> LoopResult<Option<Vec<Txid>>> {
    // Get stored last_hash
    let last_hash = last_hash(db)?;
    // Get the current confirmation delay
    let conf_delay = state.confirmation;

    // Get a set of transactions ids to parse
    let (txs, removed, lastblock): (
        HashMap<Txid, (Category, i32)>,
        HashMap<Txid, (Category, i32)>,
        BlockHash,
    ) = {
        // Get all transactions made since this block
        let list = rpc.list_since_block(Some(&last_hash), conf_delay)?;
        // Only keep ids and category
        let txs = list
            .transactions
            .into_iter()
            .map(|tx| (tx.txid, (tx.category, tx.confirmations)))
            .collect();
        let removed = list
            .removed
            .into_iter()
            .map(|tx| (tx.txid, (tx.category, tx.confirmations)))
            .collect();
        (txs, removed, list.lastblock)
    };

    // Check if a confirmed incoming transaction have been removed by a blockchain reorganization
    let new_status = sync_chain_removed(&txs, &removed, rpc, db, conf_delay as i32)?;

    // Sync status with database
    if *status != new_status {
        let mut tx = db.transaction()?;
        tx.execute(
            "UPDATE state SET value=$1 WHERE name='status'",
            &[&[new_status as u8].as_slice()],
        )?;
        tx.execute("NOTIFY status", &[])?;
        tx.commit()?;
        *status = new_status;
        if new_status {
            info!("Recovered lost transactions");
        }
    }
    if !new_status {
        return Ok(None);
    }

    let mut stuck = vec![];

    for (id, (category, confirmations)) in txs {
        match category {
            Category::Send => {
                if sync_chain_outgoing(&id, confirmations, rpc, db, state)? {
                    stuck.push(id);
                }
            }
            Category::Receive if confirmations >= conf_delay as i32 => {
                sync_chain_incoming_confirmed(&id, rpc, db, state)?
            }
            _ => {
                // Ignore coinbase and unconfirmed send transactions
            }
        }
    }

    // Move last_hash forward
    db.execute(
        "UPDATE state SET value=$1 WHERE name='last_hash' AND value=$2",
        &[
            &lastblock.as_byte_array().as_slice(),
            &last_hash.as_byte_array().as_slice(),
        ],
    )?;

    Ok(Some(stuck))
}

/// Sync database with removed transactions, return false if bitcoin backing is compromised
fn sync_chain_removed(
    txs: &HashMap<Txid, (Category, i32)>,
    removed: &HashMap<Txid, (Category, i32)>,
    rpc: &mut Rpc,
    db: &mut Client,
    min_confirmations: i32,
) -> LoopResult<bool> {
    // A removed incoming transaction is a correctness issues in only two cases:
    // - it is a confirmed credit registered in the database
    // - it is an invalid transactions already bounced
    // Those two cases can compromise bitcoin backing
    // Removed outgoing transactions will be retried automatically by the node

    let mut blocking_debit = Vec::new();
    let mut blocking_bounce = Vec::new();

    // Only keep incoming transaction that are not reconfirmed
    // TODO study risk of accepting only mined transactions for faster recovery
    for (id, _) in removed.iter().filter(|(id, (cat, _))| {
        *cat == Category::Receive
            && txs
                .get(*id)
                .map(|(_, confirmations)| *confirmations < min_confirmations)
                .unwrap_or(true)
    }) {
        match rpc.get_tx_segwit_key(id) {
            Ok((full, key)) => {
                // Credits are only problematic if not reconfirmed and stored in the database
                if db
                    .query_opt(
                        "SELECT 1 FROM tx_in WHERE reserve_pub=$1",
                        &[&key.as_slice()],
                    )?
                    .is_some()
                {
                    let debit_addr = sender_address(rpc, &full)?;
                    blocking_debit.push((key, id, debit_addr));
                }
            }
            Err(err) => match err {
                GetSegwitErr::Decode(_) => {
                    // Invalid tx are only problematic if already bounced
                    if let Some(row) = db.query_opt(
                        "SELECT txid FROM bounce WHERE bounced=$1 AND txid IS NOT NULL",
                        &[&id.as_byte_array().as_slice()],
                    )? {
                        blocking_bounce.push((sql_txid(&row, 0), id));
                    } else {
                        // Remove transaction from bounce table
                        db.execute(
                            "DELETE FROM bounce WHERE bounced=$1",
                            &[&id.as_byte_array().as_slice()],
                        )?;
                    }
                }
                GetSegwitErr::RPC(it) => return Err(it.into()),
            },
        }
    }

    if !blocking_bounce.is_empty() || !blocking_debit.is_empty() {
        let mut buf = "The following transaction have been removed from the blockchain, bitcoin backing is compromised until the transaction reappear:".to_string();
        for (key, id, addr) in blocking_debit {
            write!(
                &mut buf,
                "\n\tcredit {} in {} from {}",
                base32(&key),
                id,
                addr
            )
            .unwrap();
        }
        for (id, bounced) in blocking_bounce {
            write!(&mut buf, "\n\tbounced {} in {}", id, bounced).unwrap();
        }
        error!("{}", buf);
        Ok(false)
    } else {
        Ok(true)
    }
}

/// Sync database with an incoming confirmed transaction
fn sync_chain_incoming_confirmed(
    id: &Txid,
    rpc: &mut Rpc,
    db: &mut Client,
    state: &WireState,
) -> Result<(), LoopError> {
    match rpc.get_tx_segwit_key(id) {
        Ok((full, reserve_pub)) => {
            // Store transactions in database
            let debit_addr = sender_address(rpc, &full)?;
            let credit_addr = full.details[0].address.clone().unwrap().assume_checked();
            let date = SystemTime::UNIX_EPOCH + Duration::from_secs(full.time);
            let amount = btc_to_taler(&full.amount, state.currency);
            let nb = db.execute("INSERT INTO tx_in (_date, amount, reserve_pub, debit_acc, credit_acc) VALUES ($1, $2, $3, $4, $5) ON CONFLICT (reserve_pub) DO NOTHING ", &[
                &date, &amount.to_string(), &reserve_pub.as_slice(), &btc_payto_url(&debit_addr).as_ref(), &btc_payto_url(&credit_addr).as_ref()
            ])?;
            if nb > 0 {
                info!(
                    "<< {} {} in {} from {}",
                    amount,
                    base32(&reserve_pub),
                    id,
                    debit_addr
                );
            }
        }
        Err(err) => match err {
            GetSegwitErr::Decode(_) => {
                // If encoding is wrong request a bounce
                db.execute(
                    "INSERT INTO bounce (bounced) VALUES ($1) ON CONFLICT (bounced) DO NOTHING",
                    &[&id.as_byte_array().as_slice()],
                )?;
            }
            GetSegwitErr::RPC(e) => return Err(e.into()),
        },
    }
    Ok(())
}

/// Sync database with a debit transaction, return true if stuck
fn sync_chain_debit(
    id: &Txid,
    full: &Transaction,
    wtid: &[u8; 32],
    rpc: &mut Rpc,
    db: &mut Client,
    confirmations: i32,
    state: &WireState,
) -> LoopResult<bool> {
    let credit_addr = full.details[0].address.clone().unwrap().assume_checked();
    let amount = btc_to_taler(&full.amount, state.currency);

    if confirmations < 0 {
        if full.replaced_by_txid.is_none() {
            // Handle conflicting tx
            let nb_row = db.execute(
                "UPDATE tx_out SET status=$1, txid=NULL where txid=$2",
                &[
                    &(DebitStatus::Requested as i16),
                    &id.as_byte_array().as_slice(),
                ],
            )?;
            if nb_row > 0 {
                warn!(">> (conflict) {} in {id} to {credit_addr}", base32(wtid));
            }
        }
    } else {
        // Get previous out tx
        let row = db.query_opt(
            "SELECT id,status,txid FROM tx_out WHERE wtid=$1 FOR UPDATE",
            &[&wtid.as_slice()],
        )?;
        if let Some(row) = row {
            // If already in database, sync status
            let row_id: i32 = row.get(0);
            let status: i16 = row.get(1);
            match DebitStatus::try_from(status as u8).unwrap() {
                DebitStatus::Requested => {
                    let nb_row = db.execute(
                        "UPDATE tx_out SET status=$1, txid=$2 WHERE id=$3 AND status=$4",
                        &[
                            &(DebitStatus::Sent as i16),
                            &id.as_byte_array().as_slice(),
                            &row_id,
                            &status,
                        ],
                    )?;
                    if nb_row > 0 {
                        warn!(
                            ">> (recovered) {amount} {} in {id} to {credit_addr}",
                            base32(wtid)
                        );
                    }
                }
                DebitStatus::Sent => {
                    if let Some(txid) = full.replaces_txid {
                        let stored_id = sql_txid(&row, 2);
                        if txid == stored_id {
                            let nb_row = db.execute(
                                "UPDATE tx_out SET txid=$1 WHERE txid=$2",
                                &[
                                    &id.as_byte_array().as_slice(),
                                    &txid.as_byte_array().as_slice(),
                                ],
                            )?;
                            if nb_row > 0 {
                                info!(">> (recovered) {} replace {txid} with {id}", base32(wtid),);
                            }
                        }
                    }
                }
            }
        } else {
            // Else add to database
            let debit_addr = sender_address(rpc, full)?;
            let date = SystemTime::UNIX_EPOCH + Duration::from_secs(full.time);
            let nb = db.execute(
                    "INSERT INTO tx_out (_date, amount, wtid, debit_acc, credit_acc, exchange_url, status, txid, request_uid) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9) ON CONFLICT (wtid) DO NOTHING",
                    &[&date, &amount.to_string(), &wtid.as_slice(), &btc_payto_url(&debit_addr).as_ref(), &btc_payto_url(&credit_addr).as_ref(), &state.base_url.as_ref(), &(DebitStatus::Sent as i16), &id.as_byte_array().as_slice(), &None::<&[u8]>],
                        )?;
            if nb > 0 {
                warn!(
                    ">> (onchain) {amount} {} in {id} to {credit_addr}",
                    base32(wtid)
                );
            }
        }

        // Check if stuck
        if let Some(delay) = state.bump_delay {
            if confirmations == 0 && full.replaced_by_txid.is_none() {
                let now = SystemTime::now()
                    .duration_since(SystemTime::UNIX_EPOCH)
                    .unwrap()
                    .as_secs();
                if now - full.time > delay as u64 {
                    return Ok(true);
                }
            }
        }
    }
    Ok(false)
}

/// Sync database with an outgoing bounce transaction
fn sync_chain_bounce(
    id: &Txid,
    bounced: &Txid,
    db: &mut Client,
    confirmations: i32,
) -> LoopResult<()> {
    if confirmations < 0 {
        // Handle conflicting tx
        let nb_row = db.execute(
            "UPDATE bounce SET status=$1, txid=NULL where txid=$2",
            &[
                &(BounceStatus::Requested as i16),
                &id.as_byte_array().as_slice(),
            ],
        )?;
        if nb_row > 0 {
            warn!("|| (conflict) {} in {}", &bounced, &id);
        }
    } else {
        // Get previous bounce
        let row = db.query_opt(
            "SELECT id, status FROM bounce WHERE bounced=$1",
            &[&bounced.as_byte_array().as_slice()],
        )?;
        if let Some(row) = row {
            // If already in database, sync status
            let row_id: i32 = row.get(0);
            let status: i16 = row.get(1);
            match BounceStatus::try_from(status as u8).unwrap() {
                BounceStatus::Requested => {
                    let nb_row = db.execute(
                        "UPDATE bounce SET status=$1, txid=$2 WHERE id=$3 AND status=$4",
                        &[
                            &(BounceStatus::Sent as i16),
                            &id.as_byte_array().as_slice(),
                            &row_id,
                            &status,
                        ],
                    )?;
                    if nb_row > 0 {
                        warn!("|| (recovered) {} in {}", &bounced, &id);
                    }
                }
                BounceStatus::Ignored => error!(
                    "watcher: ignored bounce {} found in chain at {}",
                    bounced, id
                ),
                BounceStatus::Sent => { /* Status is correct */ }
            }
        } else {
            // Else add to database
            let nb = db.execute(
        "INSERT INTO bounce (bounced, txid, status) VALUES ($1, $2, $3) ON CONFLICT (txid) DO NOTHING",
        &[&bounced.as_byte_array().as_slice(), &id.as_byte_array().as_slice(), &(BounceStatus::Sent as i16)],
            )?;
            if nb > 0 {
                warn!("|| (onchain) {} in {}", &bounced, &id);
            }
        }
    }

    Ok(())
}

/// Sync database with an outgoing transaction, return true if stuck
fn sync_chain_outgoing(
    id: &Txid,
    confirmations: i32,
    rpc: &mut Rpc,
    db: &mut Client,
    state: &WireState,
) -> LoopResult<bool> {
    match rpc
        .get_tx_op_return(id)
        .map(|(full, bytes)| (full, OutMetadata::decode(&bytes)))
    {
        Ok((full, Ok(info))) => match info {
            OutMetadata::Debit { wtid, .. } => {
                return sync_chain_debit(id, &full, &wtid, rpc, db, confirmations, state);
            }
            OutMetadata::Bounce { bounced } => {
                sync_chain_bounce(id, &Txid::from_byte_array(bounced), db, confirmations)?
            }
        },
        Ok((_, Err(e))) => warn!("send: decode-info {} - {}", id, e),
        Err(e) => match e {
            GetOpReturnErr::MissingOpReturn => { /* Ignore */ }
            GetOpReturnErr::RPC(e) => return Err(e)?,
        },
    }
    Ok(false)
}

/// Send a debit transaction on the blockchain, return false if no more requested transactions are found
fn debit(db: &mut Client, rpc: &mut Rpc, state: &WireState) -> LoopResult<bool> {
    // We rely on the advisory lock to ensure we are the only one sending transactions
    let row = db.query_opt(
        "SELECT id, amount, wtid, credit_acc, exchange_url FROM tx_out WHERE status=$1 ORDER BY _date LIMIT 1",
        &[&(DebitStatus::Requested as i16)],
    )?;
    if let Some(row) = &row {
        let id: i32 = row.get(0);
        let amount = sql_btc_amount(row, 1, state.currency);
        let wtid: [u8; 32] = sql_array(row, 2);
        let addr = sql_addr(row, 3);
        let url = sql_url(row, 4);
        let metadata = OutMetadata::Debit { wtid, url };

        let tx_id = rpc.send(
            &addr,
            &amount,
            Some(&metadata.encode().or_fail(|e| format!("{}", e))),
            false,
        )?;
        fail_point("(injected) fail debit", 0.3)?;
        db.execute(
            "UPDATE tx_out SET status=$1, txid=$2 WHERE id=$3",
            &[
                &(DebitStatus::Sent as i16),
                &tx_id.as_byte_array().as_slice(),
                &id,
            ],
        )?;
        let amount = btc_to_taler(&amount.to_signed().unwrap(), state.currency);
        info!(">> {} {} in {} to {}", amount, base32(&wtid), tx_id, addr);
    }
    Ok(row.is_some())
}

/// Bounce a transaction on the blockchain, return false if no more requested transactions are found
fn bounce(db: &mut Client, rpc: &mut Rpc, fee: &BtcAmount) -> LoopResult<bool> {
    // We rely on the advisory lock to ensure we are the only one sending transactions
    let row = db.query_opt(
        "SELECT id, bounced FROM bounce WHERE status=$1 ORDER BY _date LIMIT 1",
        &[&(BounceStatus::Requested as i16)],
    )?;
    if let Some(row) = &row {
        let id: i32 = row.get(0);
        let bounced: Txid = sql_txid(row, 1);
        let metadata = OutMetadata::Bounce {
            bounced: *bounced.as_byte_array(),
        };

        match rpc.bounce(
            &bounced,
            fee,
            Some(&metadata.encode().or_fail(|e| format!("{}", e))),
        ) {
            Ok(it) => {
                fail_point("(injected) fail bounce", 0.3)?;
                db.execute(
                    "UPDATE bounce SET txid=$1, status=$2 WHERE id=$3",
                    &[
                        &it.as_byte_array().as_slice(),
                        &(BounceStatus::Sent as i16),
                        &id,
                    ],
                )?;
                info!("|| {} in {}", &bounced, &it);
            }
            Err(err) => match err {
                rpc::Error::RPC {
                    code: ErrorCode::RpcWalletInsufficientFunds | ErrorCode::RpcWalletError,
                    msg,
                } => {
                    db.execute(
                        "UPDATE bounce SET status=$1 WHERE id=$2",
                        &[&(BounceStatus::Ignored as i16), &id],
                    )?;
                    info!("|| (ignore) {} because {}", &bounced, msg);
                }
                e => Err(e)?,
            },
        }
    }
    Ok(row.is_some())
}