import {Buffer} from "buffer";
import {StarknetBtcHeader} from "./headers/StarknetBtcHeader";
import {BitcoinNetwork, BitcoinRpc, BtcBlock, BtcRelay, RelaySynchronizer, StatePredictorUtils} from "@atomiqlabs/base";
import {
    bigNumberishToBuffer,
    bufferToU32Array, getLogger,
    toHex, u32ReverseEndianness
} from "../../utils/Utils";
import {StarknetContractBase} from "../contract/StarknetContractBase";
import {StarknetBtcStoredHeader} from "./headers/StarknetBtcStoredHeader";
import {StarknetTx} from "../chain/modules/StarknetTransactions";
import {StarknetSigner} from "../wallet/StarknetSigner";
import {BtcRelayAbi} from "./BtcRelayAbi";
import {BigNumberish, hash} from "starknet";
import {StarknetFees} from "../chain/modules/StarknetFees";
import {StarknetChainInterface} from "../chain/StarknetChainInterface";
import {StarknetAction} from "../chain/StarknetAction";

function serializeBlockHeader(e: BtcBlock): StarknetBtcHeader {
    return new StarknetBtcHeader({
        reversed_version: u32ReverseEndianness(e.getVersion()),
        previous_blockhash: bufferToU32Array(Buffer.from(e.getPrevBlockhash(), "hex").reverse()),
        merkle_root: bufferToU32Array(Buffer.from(e.getMerkleRoot(), "hex").reverse()),
        reversed_timestamp: u32ReverseEndianness(e.getTimestamp()),
        nbits: u32ReverseEndianness(e.getNbits()),
        nonce: u32ReverseEndianness(e.getNonce()),
        hash: Buffer.from(e.getHash(), "hex").reverse()
    });
}

const GAS_PER_BLOCKHEADER = {l1DataGas: 600, l2Gas: 24_000_000, l1Gas: 0};
const GAS_PER_BLOCKHEADER_FORK_REORG = {l1DataGas: 1000, l2Gas: 4_000_000, l1Gas: 0};

const btcRelayAddreses: {[network in BitcoinNetwork]?: string} = {
    [BitcoinNetwork.TESTNET4]: "0x0099b63f39f0cabb767361de3d8d3e97212351a51540e2687c2571f4da490dbe",
    [BitcoinNetwork.TESTNET]: "0x068601c79da2231d21e015ccfd59c243861156fa523a12c9f987ec28eb8dbc8c",
    [BitcoinNetwork.MAINNET]: "0x057b14a4231b82f1e525ff35a722d893ca3dd2bde0baa6cee97937c5be861dbc"
};

const btcRelayDeploymentHeights: {[network in BitcoinNetwork]?: number} = {
    [BitcoinNetwork.TESTNET4]: 760719,
    [BitcoinNetwork.TESTNET]: 633915,
    [BitcoinNetwork.MAINNET]: 1278562
};

function serializeCalldata(headers: StarknetBtcHeader[], storedHeader: StarknetBtcStoredHeader, span: BigNumberish[]) {
    span.push(toHex(headers.length));
    headers.forEach(header => {
        span.push(...header.serialize());
    });
    span.push(...storedHeader.serialize());
    return span;
}

const logger = getLogger("StarknetBtcRelay: ");

/**
 * Starknet BTC Relay bitcoin light client contract representation
 *
 * @category BTC Relay
 */
export class StarknetBtcRelay<B extends BtcBlock>
    extends StarknetContractBase<typeof BtcRelayAbi>
    implements BtcRelay<StarknetBtcStoredHeader, StarknetTx, B, StarknetSigner> {

    /**
     * Returns a {@link StarknetAction} that submits new main chain bitcoin blockheaders to the light client
     *
     * @param signer Starknet signer's address
     * @param mainHeaders New bitcoin blockheaders to submit
     * @param storedHeader Current latest committed and stored bitcoin blockheader in the light client
     */
    private SaveMainHeaders(signer: string, mainHeaders: StarknetBtcHeader[], storedHeader: StarknetBtcStoredHeader): StarknetAction {

        return new StarknetAction(signer, this.Chain,
            {
                contractAddress: this.contract.address,
                entrypoint: "submit_main_blockheaders",
                calldata: serializeCalldata(mainHeaders, storedHeader, [])
            },
            StarknetFees.starknetGasMul(GAS_PER_BLOCKHEADER, mainHeaders.length)
        )
    }

    /**
     * Returns a {@link StarknetAction} for submitting a short fork bitcoin blockheaders to the light client,
     *  forking the chain from the provided `storedHeader` param's blockheight. For a successful fork the
     *  submitted chain needs to have higher total chainwork than the current cannonical chain
     *
     * @param signer Starknet signer's address
     * @param forkHeaders Fork bitcoin blockheaders to submit
     * @param storedHeader Committed and stored bitcoin blockheader from which to fork the light client
     */
    private SaveShortForkHeaders(signer: string, forkHeaders: StarknetBtcHeader[], storedHeader: StarknetBtcStoredHeader): StarknetAction {
        return new StarknetAction(signer, this.Chain,
            {
                contractAddress: this.contract.address,
                entrypoint: "submit_short_fork_blockheaders",
                calldata: serializeCalldata(forkHeaders, storedHeader, [])
            },
            StarknetFees.starknetGasMul(GAS_PER_BLOCKHEADER, forkHeaders.length)
        )
    }

    /**
     * Returns a {@link StarknetAction} for submitting a long fork of bitcoin blockheaders to the light client.
     *
     * @param signer Starknet signer's address
     * @param forkId Fork ID to submit the fork blockheaders to
     * @param forkHeaders Fork bitcoin blockheaders to submit
     * @param storedHeader Either a committed and stored bitcoin blockheader from which to fork the light client (when
     *  creating the fork), or the tip of the fork (when adding more blockheaders to the fork)
     * @param totalForkHeaders Total blockheaders in the fork - used to estimate the gas usage when re-org happens
     */
    private SaveLongForkHeaders(signer: string, forkId: number, forkHeaders: StarknetBtcHeader[], storedHeader: StarknetBtcStoredHeader, totalForkHeaders: number = 100): StarknetAction {
        return new StarknetAction(signer, this.Chain,
            {
                contractAddress: this.contract.address,
                entrypoint: "submit_fork_blockheaders",
                calldata: serializeCalldata(forkHeaders, storedHeader, [toHex(forkId)])
            },
            StarknetFees.starknetGasAdd(
                StarknetFees.starknetGasMul(GAS_PER_BLOCKHEADER, forkHeaders.length),
                StarknetFees.starknetGasMul(GAS_PER_BLOCKHEADER_FORK_REORG, totalForkHeaders)
            )
        )
    }

    /**
     * @internal
     */
    readonly _bitcoinRpc: BitcoinRpc<B>;

    readonly maxHeadersPerTx: number = 40;
    readonly maxForkHeadersPerTx: number = 25;
    readonly maxShortForkHeadersPerTx: number = 40;

    constructor(
        chainInterface: StarknetChainInterface,
        bitcoinRpc: BitcoinRpc<B>,
        bitcoinNetwork: BitcoinNetwork,
        contractAddress: string | undefined = btcRelayAddreses[bitcoinNetwork],
        contractDeploymentHeight?: number
    ) {
        if(contractAddress==null) throw new Error("No BtcRelay address specified!");
        super(
            chainInterface, contractAddress, BtcRelayAbi,
            contractDeploymentHeight ??
            (btcRelayAddreses[bitcoinNetwork]===contractAddress
                ? btcRelayDeploymentHeights[bitcoinNetwork]
                : undefined)
        );
        this._bitcoinRpc = bitcoinRpc;
    }

    /**
     * Computes subsequent commited headers as they will appear on the blockchain when transactions
     *  are submitted & confirmed
     *
     * @param initialStoredHeader
     * @param syncedHeaders
     * @private
     */
    private computeCommitedHeaders(initialStoredHeader: StarknetBtcStoredHeader, syncedHeaders: StarknetBtcHeader[]) {
        const computedCommitedHeaders = [initialStoredHeader];
        for(let blockHeader of syncedHeaders) {
            computedCommitedHeaders.push(computedCommitedHeaders[computedCommitedHeaders.length-1].computeNext(blockHeader));
        }
        return computedCommitedHeaders;
    }

    /**
     * A common logic for submitting blockheaders in a transaction
     *
     * @param signer Starknet signer's address
     * @param headers Bitcoin blockheaders to submit to the btc relay
     * @param storedHeader Current latest stored block header for a given fork or main chain
     * @param forkId Fork ID to submit to, `forkId`=0 means main chain, `forkId`=-1 means short fork
     * @param feeRate Fee rate for the transaction
     * @private
     */
    private async _saveHeaders(
        signer: string,
        headers: BtcBlock[],
        storedHeader: StarknetBtcStoredHeader,
        forkId: number,
        feeRate: string
    ) {
        const blockHeaderObj = headers.map(serializeBlockHeader);
        let starknetAction: StarknetAction;
        switch(forkId) {
            case -1:
                starknetAction = this.SaveShortForkHeaders(signer, blockHeaderObj, storedHeader);
                break;
            case 0:
                starknetAction = this.SaveMainHeaders(signer, blockHeaderObj, storedHeader);
                break;
            default:
                starknetAction = this.SaveLongForkHeaders(signer, forkId, blockHeaderObj, storedHeader);
                break;
        }

        const tx = await starknetAction.tx(feeRate);

        const computedCommitedHeaders = this.computeCommitedHeaders(storedHeader, blockHeaderObj);
        const lastStoredHeader = computedCommitedHeaders[computedCommitedHeaders.length-1];

        return {
            forkId: forkId,
            lastStoredHeader,
            tx,
            computedCommitedHeaders
        }
    }

    /**
     * Returns a committed bitcoin blockheader based on the provided `commitHash` or `blockHash`
     *
     * @param commitHash Commitment hash of the stored blockheader
     * @param blockHash Block's hash
     * @private
     */
    private getBlock(commitHash?: BigNumberish, blockHash?: Buffer): Promise<[StarknetBtcStoredHeader, bigint] | null> {
        const keys = [commitHash == null ? null : toHex(commitHash)];
        if (blockHash != null) {
            const starknetBlockHash = hash.computePoseidonHashOnElements(bufferToU32Array(Buffer.from([...blockHash]).reverse()));
            keys.push(starknetBlockHash);
        }
        return this._Events.findInContractEvents(
            ["btc_relay::events::StoreHeader", "btc_relay::events::StoreForkHeader"],
            keys,
            (event) => {
                return Promise.resolve([StarknetBtcStoredHeader.fromSerializedFeltArray(event.data), BigInt(event.params.commit_hash)]);
            }
        );
    }

    /**
     * Returns the current main chain blockheight of the BTC Relay
     *
     * @private
     */
    private async getBlockHeight(): Promise<number> {
        return Number(await this.contract.get_blockheight());
    }

    /**
     * @inheritDoc
     */
    public async getTipData(): Promise<{ commitHash: string; blockhash: string, chainWork: Buffer, blockheight: number } | null> {
        const commitHash = await this.contract.get_tip_commit_hash();
        if(commitHash==null || BigInt(commitHash)===BigInt(0)) return null;

        const result = await this.getBlock(commitHash);
        if(result==null) return null;

        const [storedBlockHeader] = result;

        return {
            blockheight: storedBlockHeader.getBlockheight(),
            commitHash: bigNumberishToBuffer(commitHash, 32).toString("hex"),
            blockhash: storedBlockHeader.getBlockHash().toString("hex"),
            chainWork: storedBlockHeader.getChainWork()
        };
    }

    /**
     * @inheritDoc
     */
    public async retrieveLogAndBlockheight(blockData: {blockhash: string}, requiredBlockheight?: number): Promise<{
        header: StarknetBtcStoredHeader,
        height: number
    } | null> {
        //TODO: we can fetch the blockheight and events in parallel
        const blockHeight = await this.getBlockHeight();
        if(requiredBlockheight!=null && blockHeight < requiredBlockheight) {
            return null;
        }
        const result = await this.getBlock(undefined, Buffer.from(blockData.blockhash, "hex"));
        if(result==null) return null;

        const [storedBlockHeader, commitHash] = result;

        //Check if block is part of the main chain
        const chainCommitment = await this.contract.get_commit_hash(storedBlockHeader.getBlockheight());
        if(BigInt(chainCommitment)!==BigInt(commitHash)) return null;

        logger.debug("retrieveLogAndBlockheight(): block found," +
            " commit hash: "+toHex(commitHash)+" blockhash: "+blockData.blockhash+" current btc relay height: "+blockHeight);

        return {header: storedBlockHeader, height: blockHeight};
    }

    /**
     * @inheritDoc
     */
    public async retrieveLogByCommitHash(commitmentHash: string, blockData: {blockhash: string}): Promise<StarknetBtcStoredHeader | null> {
        const result = await this.getBlock(commitmentHash, Buffer.from(blockData.blockhash, "hex"));
        if(result==null) return null;

        const [storedBlockHeader, commitHash] = result;

        //Check if block is part of the main chain
        const chainCommitment = await this.contract.get_commit_hash(storedBlockHeader.getBlockheight());
        if(BigInt(chainCommitment)!==BigInt(commitHash)) return null;

        logger.debug("retrieveLogByCommitHash(): block found," +
            " commit hash: "+commitmentHash+" blockhash: "+blockData.blockhash+" height: "+storedBlockHeader.getBlockheight());

        return storedBlockHeader;
    }

    /**
     * @inheritDoc
     */
    public async retrieveLatestKnownBlockLog(): Promise<{
        resultStoredHeader: StarknetBtcStoredHeader,
        resultBitcoinHeader: B
    } | null> {
        const data = await this._Events.findInContractEvents(
            ["btc_relay::events::StoreHeader", "btc_relay::events::StoreForkHeader"],
            null,
            async (event) => {
                const storedHeader = StarknetBtcStoredHeader.fromSerializedFeltArray(event.data);

                const blockHashHex = storedHeader.getBlockHash().toString("hex");
                const commitHash = event.params.commit_hash;

                const [isInBtcMainChain, btcRelayCommitHash] = await Promise.all([
                    this._bitcoinRpc.isInMainChain(blockHashHex).catch(() => false),
                    this.contract.get_commit_hash(storedHeader.getBlockheight())
                ]);

                if(!isInBtcMainChain) return null;
                if(BigInt(commitHash)!==BigInt(btcRelayCommitHash)) return null;

                const bitcoinBlockHeader = await this._bitcoinRpc.getBlockHeader(blockHashHex);
                if(bitcoinBlockHeader==null) return null;

                return {
                    resultStoredHeader: storedHeader,
                    resultBitcoinHeader: bitcoinBlockHeader,
                    commitHash: commitHash
                }
            }
        )

        if(data!=null) logger.debug("retrieveLatestKnownBlockLog(): block found," +
            " commit hash: "+toHex(data.commitHash)+" blockhash: "+data.resultBitcoinHeader.getHash()+
            " height: "+data.resultStoredHeader.getBlockheight());

        return data;
    }

    /**
     * @inheritDoc
     */
    public async saveMainHeaders(signer: string, mainHeaders: BtcBlock[], storedHeader: StarknetBtcStoredHeader, feeRate?: string) {
        feeRate ??= await this.getMainFeeRate(signer);
        logger.debug("saveMainHeaders(): submitting main blockheaders, count: "+mainHeaders.length);
        return this._saveHeaders(signer, mainHeaders, storedHeader, 0, feeRate);
    }

    /**
     * @inheritDoc
     */
    public async saveNewForkHeaders(signer: string, forkHeaders: BtcBlock[], storedHeader: StarknetBtcStoredHeader, tipWork: Buffer, feeRate?: string) {
        let forkId: number = Math.floor(Math.random() * 0xFFFFFFFFFFFF);
        feeRate ??= await this.getForkFeeRate(signer, forkId);

        logger.debug("saveNewForkHeaders(): submitting new fork & blockheaders," +
            " count: "+forkHeaders.length+" forkId: 0x"+forkId.toString(16));

        const result = await this._saveHeaders(signer, forkHeaders, storedHeader, forkId, feeRate);
        if(result.forkId!==0 && StatePredictorUtils.gtBuffer(result.lastStoredHeader.getChainWork(), tipWork)) {
            //Fork's work is higher than main chain's work, this fork will become a main chain
            result.forkId = 0;
        }
        return result;
    }

    /**
     * @inheritDoc
     */
    public async saveForkHeaders(signer: string, forkHeaders: BtcBlock[], storedHeader: StarknetBtcStoredHeader, forkId: number, tipWork: Buffer, feeRate?: string) {
        feeRate ??= await this.getForkFeeRate(signer, forkId);

        logger.debug("saveForkHeaders(): submitting blockheaders to existing fork," +
            " count: "+forkHeaders.length+" forkId: 0x"+forkId.toString(16));

        const result = await this._saveHeaders(signer, forkHeaders, storedHeader, forkId, feeRate);
        if(result.forkId!==0 && StatePredictorUtils.gtBuffer(result.lastStoredHeader.getChainWork(), tipWork)) {
            //Fork's work is higher than main chain's work, this fork will become a main chain
            result.forkId = 0;
        }
        return result;
    }

    /**
     * @inheritDoc
     */
    public async saveShortForkHeaders(signer: string, forkHeaders: BtcBlock[], storedHeader: StarknetBtcStoredHeader, tipWork: Buffer, feeRate?: string) {
        feeRate ??= await this.getMainFeeRate(signer);
        logger.debug("saveShortForkHeaders(): submitting short fork blockheaders," +
            " count: "+forkHeaders.length);

        const result = await this._saveHeaders(signer, forkHeaders, storedHeader, -1, feeRate);
        if(result.forkId!==0 && StatePredictorUtils.gtBuffer(result.lastStoredHeader.getChainWork(), tipWork)) {
            //Fork's work is higher than main chain's work, this fork will become a main chain
            result.forkId = 0;
        }
        return result;
    }

    /**
     * @inheritDoc
     */
    public async estimateSynchronizeFee(requiredBlockheight: number, feeRate?: string): Promise<bigint> {
        const tipData = await this.getTipData();
        if(tipData==null) throw new Error("Cannot get relay tip data, relay not initialized?");
        const currBlockheight = tipData.blockheight;

        const blockheightDelta = requiredBlockheight-currBlockheight;

        if(blockheightDelta<=0) return 0n;

        const synchronizationFee = BigInt(blockheightDelta) * await this.getFeePerBlock(feeRate);
        logger.debug("estimateSynchronizeFee(): required blockheight: "+requiredBlockheight+
            " blockheight delta: "+blockheightDelta+" fee: "+synchronizationFee.toString(10));

        return synchronizationFee;
    }

    /**
     * @inheritDoc
     */
    public async getFeePerBlock(feeRate?: string): Promise<bigint> {
        feeRate ??= await this.Chain.Fees.getFeeRate();
        return StarknetFees.getGasFee(GAS_PER_BLOCKHEADER, feeRate);
    }

    /**
     * @inheritDoc
     */
    public getMainFeeRate(signer: string | null): Promise<string> {
        return this.Chain.Fees.getFeeRate();
    }

    /**
     * @inheritDoc
     */
    public getForkFeeRate(signer: string, forkId: number): Promise<string> {
        return this.Chain.Fees.getFeeRate();
    }

    /**
     * @inheritDoc
     */
    saveInitialHeader(signer: string, header: B, epochStart: number, pastBlocksTimestamps: number[], feeRate?: string): Promise<StarknetTx> {
        throw new Error("Not supported, starknet contract is initialized with constructor!");
    }

    /**
     * Gets committed headers, identified by blockhash & blockheight, determines required BTC relay blockheight based on
     *  requiredConfirmations.
     * If synchronizer is passed & some blockhash is not found (or blockhash doesn't have enough confirmations),
     *  it produces transactions to sync up the btc relay to the current chain tip & adds them to the passed txs array.
     *
     * @param signer A signer's address to use for the transactions
     * @param btcRelay BtcRelay contract to use for retrieving committed headers
     * @param btcTxs Bitcoin transactions to fetch the stored blockheaders for
     * @param txs Transactions array, in case we need to synchronize the btc relay ourselves the synchronization
     *  txns are added here
     * @param synchronizer optional synchronizer to use to synchronize the btc relay in case it is not yet synchronized
     *  to the required blockheight
     * @param feeRate Fee rate to use for synchronization transactions
     *
     * @private
     */
    static async getCommitedHeadersAndSynchronize(
        signer: string,
        btcRelay: StarknetBtcRelay<any>,
        btcTxs: {blockheight: number, requiredConfirmations: number, blockhash: string}[],
        txs: StarknetTx[],
        synchronizer?: RelaySynchronizer<StarknetBtcStoredHeader, StarknetTx, any>,
        feeRate?: string
    ): Promise<{
        [blockhash: string]: StarknetBtcStoredHeader
    } | null> {
        const leavesTxs: {blockheight: number, requiredConfirmations: number, blockhash: string}[] = [];

        const blockheaders: {
            [blockhash: string]: StarknetBtcStoredHeader
        } = {};

        for(let btcTx of btcTxs) {
            const requiredBlockheight = btcTx.blockheight+btcTx.requiredConfirmations-1;

            const result = await btcRelay.retrieveLogAndBlockheight({
                blockhash: btcTx.blockhash
            }, requiredBlockheight);

            if(result!=null) {
                blockheaders[result.header.getBlockHash().toString("hex")] = result.header;
            } else {
                leavesTxs.push(btcTx);
            }
        }

        if(leavesTxs.length===0) return blockheaders;

        //Need to synchronize
        if(synchronizer==null) return null;

        //TODO: We don't have to synchronize to tip, only to our required blockheight
        const resp = await synchronizer.syncToLatestTxs(signer.toString(), feeRate);
        logger.debug("getCommitedHeaderAndSynchronize(): BTC Relay not synchronized to required blockheight, "+
            "synchronizing ourselves in "+resp.txs.length+" txs");
        logger.debug("getCommitedHeaderAndSynchronize(): BTC Relay computed header map: ",resp.computedHeaderMap);
        txs.push(...resp.txs);

        for(let key in resp.computedHeaderMap) {
            const header = resp.computedHeaderMap[key];
            blockheaders[header.getBlockHash().toString("hex")] = header;
        }

        //Check that blockhashes of all the rest txs are included
        for(let btcTx of leavesTxs) {
            if(blockheaders[btcTx.blockhash]==null) return null;
        }

        //Retrieve computed headers
        return blockheaders;
    }

}