/*
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

const API_PREFIX = "https://blockstream.info/api";

const IRON_BLOCK = "https://gamepedia.cursecdn.com/minecraft_gamepedia/7/7e/Block_of_Iron_JE4_BE3.png?version=692673bafa1e94785ab6012d7a3c8dc4";
const GOLD_BLOCK = "https://gamepedia.cursecdn.com/minecraft_gamepedia/archive/7/72/20190429060628%21Block_of_Gold_JE6_BE3.png?version=448d791eb688910a0cc215181312b715";
const DIAMOND_BLOCK = "https://gamepedia.cursecdn.com/minecraft_gamepedia/archive/6/6b/20190502005227%21Block_of_Diamond_JE6_BE3.png?version=721888d830050c06303696cf79695eb9";

const HALVING_PERIOD = 210000;

var recentBlocks = null;

function getCurTipBlock() {
    return recentBlocks[0];
}

function doApiReq(endpoint, cb) {
    let xhr = new XMLHttpRequest();

    xhr.timeout = 5000;

    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            if (xhr.status == 200) {
                let json = JSON.parse(xhr.responseText);
                cb(json);
            } else {
                // TODO Make this better?
                cb(null);
            }
        }
    };

    xhr.open("GET", API_PREFIX + endpoint);
    xhr.send()
}

function doGetRecentBlocks(cb) {
    doApiReq("/blocks/tip", cb);
}

function doGetBlockCoinBaseTx(blockhash, cb) {
    let reqSuffix = "/block/" + blockhash + "/txs";
    let internalCb = function(resp) {
        if (resp != null) {
            cb(resp[0]);
        } else {
            cb(null);
        }
    };

    doApiReq(reqSuffix, function(resp) {
        if (resp != null) {
            internalCb(resp);
        } else {
            // Sometimes the data hasn't been fully processed yet by the time we
            // make the call so wait a bit and then try again.
            setTimeout(function() {
                doApiReq(reqSuffix, internalCb);
            }, 1000)
        }
    });
}

function calcRenderedSatQty(sats, decimals) {
    let subBtc = sats % 100000000;
    let btc = (sats - subBtc) / 100000000;

    let maskModulus = 10 ** (8 - decimals);
    let subDecimal = (subBtc - (subBtc % maskModulus)) / maskModulus;
    let decimal = "0".repeat(decimals) + subDecimal.toString();

    if (decimal != 0) {
        return btc.toString() + "." + decimal.substr(decimals * -1);
    } else {
        return btc.toString();
    }
}

function calcNextHalvingHeight() {
    let height = recentBlocks[0].height;
    let epoch = Math.floor(height / HALVING_PERIOD);
    return (epoch + 1) * HALVING_PERIOD;
}

function calcRewardAtHeight(height) {
    let epoch = Math.floor(height / HALVING_PERIOD);
    return 5000000000 / (2 ** epoch);
}

function calcRewardBreakdown(height, sats) {
    let subsidy = calcRewardAtHeight(height);
    let fees = sats - subsidy;

    let rSubsidy = calcRenderedSatQty(subsidy, 2);
    let rFees = calcRenderedSatQty(fees, 3);
    return rSubsidy + " subsidy + " + rFees + " fees"
}

function toggleElemSelected(elem) {
    if (elem.classList.contains("blbselected")) {
        elem.classList.remove("blbselected");
    } else {
        elem.classList.add("blbselected");
    }
}

function formatDate(date) {
    let year = date.getUTCFullYear();
    let month = "0" + (1 + date.getUTCMonth());
    let day = "0" + date.getUTCDate();
    let hours = "0" + date.getUTCHours();
    let minutes = "0" + date.getUTCMinutes();
    let seconds = "0" + date.getUTCSeconds();

    let datePart = year + "-" + month.substr(-2) + "-" + day.substr(-2);
    let timePart = hours.substr(-2) + ":" + minutes.substr(-2) + ":" + seconds.substr(-2);

    return datePart + " " + timePart;
}

function calcAdjustedETA() {
    let sum = 0;
    for (let i = 0; i < recentBlocks.length - 1; i++) {
        let cur = recentBlocks[i];
        let prev = recentBlocks[i + 1];
        let diff = cur.timestamp - prev.timestamp;
        if (diff < 0) {
            continue;
        }
        sum += diff;
    }

    let avgBlockTimeSec = sum / (recentBlocks.length - 1);
    let secsLeft = (calcNextHalvingHeight() - getCurTipBlock().height) * avgBlockTimeSec;

    let now = new Date();
    let tzOff = now.getTimezoneOffset();
    let adjEta = new Date(now.getTime() + (secsLeft * 1000) - (tzOff * 60));

    return formatDate(adjEta);
}

function updateFancyPrediction() {
    let adjEta = calcAdjustedETA();
    let elem = document.getElementById("fancyprediction");
    elem.innerHTML = "very roughly " + adjEta + " local time";
}

function isHalvingHeight(height) {
    return height % HALVING_PERIOD == 0;
}

function makeBlockElem(block, prevBlock) {
    let entry = document.createElement("div");

    let innerElem = document.createElement("div");
    innerElem.classList.add("entryinner");
    entry.appendChild(innerElem);

    if (block.height % 2 == 0) {
        innerElem.classList.add("blocklisteven");
    } else {
        innerElem.classList.add("blocklistodd");
    }

    /* ===== Top row data ===== */

    let topElem = document.createElement("div");
    topElem.classList.add("entrytop");
    innerElem.appendChild(topElem);

    // Make the icon.
    let iconCtr = document.createElement("div");
    iconCtr.classList.add("blbiconctr");
    topElem.appendChild(iconCtr);
    let iconElem = document.createElement("img");
    iconElem.classList.add("blbicon");
    iconCtr.appendChild(iconElem);
    if (isHalvingHeight(block.height)) {
        iconElem.src = DIAMOND_BLOCK;
        entry.classList.add("halvingblockentry");
    } else {
        iconElem.src = GOLD_BLOCK;
    }

    // Element for all the data.
    let dataElem = document.createElement("div");
    dataElem.classList.add("blbdata");
    topElem.appendChild(dataElem);

    // Make the height element.
    let heightElem = document.createElement("span");
    heightElem.classList.add("blbheight");
    heightElem.innerHTML = block.height.toString();
    dataElem.appendChild(heightElem);

    // this makes it look a lot nicer
    dataElem.append("—");

    // Make the timestamp element.
    let timestampElem = document.createElement("span");
    let timestampDate = new Date(block.timestamp * 1000);
    timestampElem.innerHTML = formatDate(timestampDate) + " UTC";
    dataElem.appendChild(timestampElem);

    // this makes it look a lot nicer
    dataElem.append("—");

    // Make the reward breakdown element.
    let rewardElem = document.createElement("span");
    rewardElem.innerHTML = "Reward: ? sat";
    dataElem.appendChild(rewardElem);
    doGetBlockCoinBaseTx(block.id, function(resp) {
        let reward = resp.vout[0].value;
        let rewardStr = calcRewardBreakdown(block.height, reward);
        rewardElem.innerHTML = rewardStr;
    });

    /* ==== Detail row data ===== */

    // Details
    let detailElem = document.createElement("div");
    detailElem.classList.add("entrydetail");

    // Make the hash element.
    let hashElem = document.createElement("div");
    hashElem.innerHTML = block.id;
    hashElem.classList.add("blbhash");
    detailElem.appendChild(hashElem);

    // Weight and height
    let sizeElem = document.createElement("div");
    detailElem.appendChild(sizeElem);
    let blockKB = Math.floor(block.size / 1024);
    let blockkWU = Math.floor(block.weight / 1024);
    sizeElem.innerHTML = "Size/Weight: " + blockKB + " KiB / " + blockkWU + " kSipa";

    // Number of transactions
    let txsElem = document.createElement("div");
    detailElem.appendChild(txsElem);
    txsElem.innerHTML = "Tx count: " + block.tx_count;

    // Make the duration element.
    if (prevBlock != null) {
        let timeElem = document.createElement("div");
        let blocktime = block.timestamp - prevBlock.timestamp;
        if (blocktime < 0) {
            blocktime = 0; // ehhhhhhhh
        }
        timeElem.innerHTML = "Since last block: " + blocktime.toString() + " sec";
        detailElem.appendChild(timeElem);
    } else {
        let oopsElem = document.createElement("div");
        oopsElem.innerHTML = "<br/>(I don't feel like making the request to get the previous block to find the blocktime)";
        detailElem.appendChild(oopsElem);
    }

    let linksElem = document.createElement("div");
    linksElem.classList.add("detaillinks");
    detailElem.appendChild(linksElem);

    // Link to the block on Blockstream's explorer.
    let blockstreamLink = document.createElement("a");
    blockstreamLink.href = "https://blockstream.info/block/"+ block.id;
    let blockstreamLogo = document.createElement("img");
    blockstreamLogo.src = "https://blockstream.info/img/icons/blockstream-logo.png";
    blockstreamLink.appendChild(blockstreamLogo);
    let viewonElem = document.createElement("span");
    viewonElem.innerHTML = "View on blockstream.info";
    blockstreamLink.appendChild(viewonElem);
    linksElem.appendChild(blockstreamLink);

    // Thing to close the details.
    //let closeElem = document.createElement("div");
    //closeElem.classList.add("closebtn");
    //closeElem.innerHTML = "close";
    linksElem.onclick = function() {
        console.log("foobar");
        // This is such a hack but it works.  We have to do this because the
        // onclick for the entry we're removing it from here *still gets run*
        // when we pick up the click here.  This just defers removing it until
        // we're about to render the next frame, so we're sure we remove it.
        window.requestAnimationFrame(function() {
            entry.classList.add("blbselected");
        });
    };
    //detailElem.appendChild(closeElem);

    /* ===== Finalize ===== */

    // Put it together.
    innerElem.appendChild(detailElem);
    entry.appendChild(innerElem);
    entry.classList.add("blocklistentry");
    entry.onclick = function() {
        toggleElemSelected(entry);
    };

    return entry;
}

var blocksLeftElem = null;
var timeLeftElem = null;
var halfTimeElem = null;

const TARGET_BLOCKTIME = 10 * 60;
var blocktimeAvgSecs = TARGET_BLOCKTIME;

function updateRemainingCount(block) {
    if (blocksLeftElem == null) {
        blocksLeftElem = document.getElementById("blocksleft");
    }

    if (timeLeftElem == null) {
        timeLeftElem = document.getElementById("timeleft");
    }

    if (halfTimeElem == null) {
        halfTimeElem = document.getElementById("halftime");
    }

    let nextHalvingHeight = calcNextHalvingHeight();
    let blocksLeft = nextHalvingHeight - getCurTipBlock().height;
    blocksLeftElem.innerHTML = blocksLeft.toString()

    if (blocksLeft <= 1) {
        timeLeftElem.innerHTML = "Halving imminent!";

        // Hide the expected time.
        let timectr = document.getElementById("halftimectr");
        timectr.style.display = "none";

    } else {
        let nowUnix = Date.now() / 1000; // wtf???

        let sinceLastBlock = nowUnix - block.timestamp;
        let secsLeft = ((blocksLeft * blocktimeAvgSecs) - sinceLastBlock)|0;

        let secsPart = secsLeft % 60;
        let minLeft = (secsLeft - secsPart) / 60;
        let minPart = minLeft % 60;
        let hrsLeft = (minLeft - minPart) / 60;

        let acc = secsPart + "s";
        if (minLeft > 0) {
            acc = (minPart + "m ") + acc;
        }
        if (hrsLeft > 0) {
            acc = (hrsLeft + "h ") + acc;
        }

        timeLeftElem.innerHTML = "roughly " + acc + " remaining";

        // Reward halving date.
        let localNow = new Date();
        let tzOff = (new Date()).getTimezoneOffset() * 60 * 1000;
        let etaDate = new Date(localNow.getTime() + (secsLeft * 1000) - tzOff);
        let formattedEtaDate = formatDate(etaDate);
        halfTimeElem.innerHTML = "around " + formattedEtaDate + " local time";

    }
}

function addNewBlock(block) {

    let prev = getCurTipBlock();
    recentBlocks = [block].concat(recentBlocks);
    //updateBlocktimeAvg();
    let elem = makeBlockElem(block, prev);

    elem.classList.add("newblock");
    setTimeout(function() {
        elem.classList.remove("newblock");
    }, 2000);

    let blocklist = document.getElementById("blocklist");
    blocklist.prepend(elem);

}

function populateRecentBlocks(blocks) {

    let blocklist = document.getElementById("blocklist");
    let loadingElem = document.getElementById("blocklistloading");

    updateRemainingCount(getCurTipBlock());

    for (let i = 0; i < blocks.length; i++) {
        let block = blocks[i];
        let prevBlock = null;
        if (i < blocks.length - 1) {
            prevBlock = blocks[i + 1];
        }

        let elem = makeBlockElem(block, prevBlock);

        if (i == 0) {
            // Adding the new block so we give it the class to make it colored,
            // but set a timer so it goes away eventually.
            elem.classList.add("newblock");
            setTimeout(function() {
                elem.classList.remove("newblock");
            }, 2000);
        }

        blocklist.appendChild(elem);

    }

    loadingElem.style.display = "none";
    //updateRemainingCount(curTipBlock);
}

function getPollDelayAtHeight(height) {
    let blocksUntilHalving = calcNextHalvingHeight() - height;
    if (blocksUntilHalving <= 2) {
        return 2500;
    } else {
        return 10000;
    }
}

function checkNewBlocks() {
    console.log("Polling for new blocks...");
    doGetRecentBlocks(function(blocks) {
        if (blocks == null) {
            alert("Error polling for new bocks, please refresh the page.");
            return;
        }

        let curTip = getCurTipBlock();

        // Find the index of the newest known block.
        let knownHeight = curTip.height;
        let newestKnownIndex = -1;
        for (let i = 0; i < blocks.length; i++) {
            if (blocks[i].height == knownHeight) {
                newestKnownIndex = i;
                break;
            }
        }

        // If there's no new blocks, exit.
        if (newestKnownIndex == 0) {
            console.log("No new blocks found.");
        } else if (newestKnownIndex == -1) {
            console.log("wtf");
        }

        // If there are new blocks, add them.
        for (let i = newestKnownIndex - 1; i >= 0; i--) {
            let newBlock = blocks[i];
            console.log("Adding new block at height " + newBlock.height + " (" + newBlock.id + ")");
            addNewBlock(newBlock);
        }

        // Set up to call this again.
        setTimeout(checkNewBlocks, getPollDelayAtHeight(recentBlocks[0].height));
    });
}

function init() {
    console.log("Hello!");

    doGetRecentBlocks(function(blocks) {
        if (blocks == null) {
            alert("Error loading blocks, please refresh the page.");
            return;
        }

        recentBlocks = blocks;
        //updateBlocktimeAvg();

        populateRecentBlocks(blocks);
        setTimeout(checkNewBlocks, 5000);
        setInterval(function() {
            updateRemainingCount(recentBlocks[0]);
        }, 1000);
    });
}