module analytics.balances;

import handy_http_primitives : Optional, mapIfPresent;
import std.datetime;
import std.stdio;
import std.path;
import std.file;
import slf4d;
import asdf;

import profile.data;
import profile.model;
import account.data;
import account.model;
import account.service;
import analytics.util;
import transaction.model;
import transaction.dto;
import util.pagination;

struct TimeSeriesPoint {
    /// The millisecond UTC timestamp.
    ulong x;
    /// The value at this timestamp.
    long y;
}

alias CurrencyGroupedTimeSeries = TimeSeriesPoint[][string];

struct AccountBalanceData {
    ulong accountId;
    string currencyCode;
    TimeSeriesPoint[] data;
}

struct BalanceTimeSeriesAnalytics {
    AccountBalanceData[] accounts;
    CurrencyGroupedTimeSeries totals;
}

void computeAccountBalanceTimeSeries(Profile profile, ProfileRepository profileRepo) {
    ProfileDataSource ds = profileRepo.getDataSource(profile);
    Account[] accounts = ds.getAccountRepository().findAll();

    // Initialize the data structure that'll store the analytics info.
    BalanceTimeSeriesAnalytics data;
    foreach (account; accounts) {
        AccountBalanceData accountData;
        accountData.accountId = account.id;
        accountData.currencyCode = account.currency.code.idup;
        data.accounts ~= accountData;
    }

    foreach (timestamp; generateTimeSeriesTimestamps(days(1), 365)) {
        // Compute the balance of each account at this timestamp.
        foreach (idx, account; accounts) {
            auto balance = getBalance(ds, account.id, timestamp);
            if (!balance.isNull) {
                data.accounts[idx].data ~= TimeSeriesPoint(
                    timestamp.toUnixMillis(),
                    balance.value
                );
            }
        }

        // Compute total balances for this timestamp.
        auto totalBalances = getTotalBalanceForAllAccounts(ds, timestamp);
        foreach (CurrencyBalance bal; totalBalances) {
            data.totals[bal.currency.code.idup] ~= TimeSeriesPoint(timestamp.toUnixMillis(), bal.balance);
        }
    }

    ds.doTransaction(() {
        ds.getPropertiesRepository().deleteProperty("analytics.balanceTimeSeries");
        ds.getPropertiesRepository().setProperty(
            "analytics.balanceTimeSeries",
            serializeToJsonPretty(data)
        );
    });
    infoF!"Computed account balance analytics for user %s, profile %s."(
        profile.username,
        profile.name
    );
}

struct CategorySpendData {
    ulong categoryId;
    string categoryName;
    string categoryColor;
    CurrencyGroupedTimeSeries dataByCurrency;
}

struct CategorySpendTimeSeriesAnalytics {
    CategorySpendData[] categories;
}

void computeCategorySpendTimeSeries(Profile profile, ProfileRepository profileRepo) {
    ProfileDataSource ds = profileRepo.getDataSource(profile);
    TransactionCategory[] rootCategories = ds.getTransactionCategoryRepository()
        .findAllByParentId(Optional!ulong.empty);

    CategorySpendTimeSeriesAnalytics data;
    
    PageRequest pr = PageRequest(1, 100, [Sort("txn.timestamp", SortDir.ASC)]);
    Page!TransactionsListItem page = ds.getTransactionRepository().findAll(pr);
    while (page.items.length > 0) {
        foreach (TransactionsListItem txn; page.items) {
            if (!isTypicalSpendingTransaction(txn)) continue;

            ulong categoryId = txn.category.mapIfPresent!(c => c.id).orElse(0);
            TimeSeriesPoint dataPoint = TimeSeriesPoint(
                SysTime.fromISOExtString(txn.timestamp).toUnixMillis(),
                txn.amount
            );

            bool foundCategory = false;
            foreach (ref cd; data.categories) {
                if (cd.categoryId == categoryId) {
                    cd.dataByCurrency[txn.currency.code.idup] ~= dataPoint;
                    foundCategory = true;
                    break;
                }
            }
            if (!foundCategory) {
                CategorySpendData cd;
                cd.categoryId = categoryId;
                cd.categoryName = txn.category.mapIfPresent!(c => c.name).orElse("None");
                cd.categoryColor = txn.category.mapIfPresent!(c => c.color).orElse("FFFFFF");
                cd.dataByCurrency[txn.currency.code.idup] ~= dataPoint;
                data.categories ~= cd;
            }
        }
        page = ds.getTransactionRepository().findAll(page.pageRequest.next());
    }

    ds.doTransaction(() {
        ds.getPropertiesRepository().deleteProperty("analytics.categorySpendTimeSeries");
        ds.getPropertiesRepository().setProperty(
            "analytics.categorySpendTimeSeries",
            serializeToJsonPretty(data)
        );
    });
    infoF!"Computed category spend analytics for user %s, profile %s."(
        profile.username,
        profile.name
    );
}

private bool isTypicalSpendingTransaction(in TransactionsListItem txn) {
    return !txn.creditedAccount.isNull &&
        txn.debitedAccount.isNull &&
        !txn.internalTransfer;
}