ufo_data/ufojson_core.cpp

// ufojson_core.cpp
// Copyright (C) 2023 Richard Geldreich, Jr.
#include "ufojson_core.h"

// Note that May ends in a period.
const char* g_months[12] =
{
    "Jan.",
    "Feb.",
    "Mar.",
    "Apr.",
    "May.",
    "Jun.",
    "Jul.",
    "Aug.",
    "Sep.",
    "Oct.",
    "Nov.",
    "Dec."
};

const char* g_full_months[12] =
{
    "January",
    "February",
    "March",
    "April",
    "May",
    "June",
    "July",
    "August",
    "September",
    "October",
    "November",
    "December"
};

const char* g_date_prefix_strings[NUM_DATE_PREFIX_STRINGS] =
{
    "Early Spring",
    "Early Summer",
    "Early Autumn",
    "Early Fall",
    "Early Winter",

    "Mid Spring",
    "Mid Summer",
    "Mid Autumn",
    "Mid Fall",
    "Mid Winter",

    "Late Spring",
    "Late Summer",
    "Late Autumn",
    "Late Fall",
    "Late Winter",

    "Spring",
    "Summer",
    "Autumn",
    "Fall",
    "Winter",

    "Early",
    "Mid",
    "Late",
    "End of"
};

bool is_season(date_prefix_t prefix)
{
    switch (prefix)
    {
    case cEarlySpring:
    case cEarlySummer:
    case cEarlyAutumn:
    case cEarlyFall:
    case cEarlyWinter:

    case cMidSpring:
    case cMidSummer:
    case cMidAutumn:
    case cMidFall:
    case cMidWinter:

    case cLateSpring:
    case cLateSummer:
    case cLateAutumn:
    case cLateFall:
    case cLateWinter:

    case cSpring:
    case cSummer:
    case cAutumn:
    case cFall:
    case cWinter:
        return true;
    default:
        break;
    }

    return false;
}

int determine_month(const std::string& date)
{
    uint32_t i;
    for (i = 0; i < 12; i++)
        if (string_begins_with(date, g_full_months[i]))
            return i;
    return -1;
}

event_date::event_date()
{
    clear();
}

event_date::event_date(const event_date& other)
{
    *this = other;
}

bool event_date::sanity_check() const
{
    if (m_year == -1)
        return false;

    if ((m_month == 0) || (m_day == 0))
        return false;

    if ((m_month < -1) || (m_month > 12))
        return false;

    if ((m_day < -1) || (m_day > 31))
        return false;

    if (m_plural)
    {
        if (m_month != -1)
            return false;
    }

    if (m_month == -1)
    {
        if (m_day != -1)
            return false;
    }

    if (is_season(m_prefix))
    {
        if (m_month != -1)
            return false;

        if (m_day != -1)
            return false;
    }
    else if ((m_prefix >= cEarly) && (m_prefix <= cEndOf))
    {
        if (m_day != -1)
            return false;
    }

    return true;
}

bool event_date::operator== (const event_date& rhs) const
{
    return (m_prefix == rhs.m_prefix) &&
        (m_year == rhs.m_year) &&
        (m_month == rhs.m_month) &&
        (m_day == rhs.m_day) &&
        (m_fuzzy == rhs.m_fuzzy) &&
        (m_plural == rhs.m_plural) &&
        (m_approx == rhs.m_approx) &&
        (m_estimated == rhs.m_estimated);
}

bool event_date::operator!= (const event_date& rhs) const
{
    return !(*this == rhs);
}

event_date& event_date::operator =(const event_date& rhs)
{
    m_prefix = rhs.m_prefix;
    m_year = rhs.m_year;
    m_month = rhs.m_month;
    m_day = rhs.m_day;
    m_fuzzy = rhs.m_fuzzy;
    m_plural = rhs.m_plural;
    m_approx = rhs.m_approx;
    m_estimated = rhs.m_estimated;
    return *this;
}

void event_date::clear()
{
    m_prefix = cNoPrefix;

    m_year = -1;
    m_month = -1;
    m_day = -1;

    m_fuzzy = false; //?
    m_plural = false; // 's
    m_approx = false; // (approximate)
    m_estimated = false; // (estimated)
}

bool event_date::is_valid() const
{
    return m_year != -1;
}

std::string event_date::get_string() const
{
    if (m_year == -1)
        return "";

    std::string res;

    if (m_prefix != cNoPrefix)
    {
        res = g_date_prefix_strings[m_prefix];
        res += " ";
    }

    if (m_month == -1)
    {
        assert(m_day == -1);

        char buf[256];
        sprintf_s(buf, "%i", m_year);
        res += buf;
    }
    else if (m_day == -1)
    {
        assert(m_month >= 1 && m_month <= 12);

        char buf[256];
        sprintf_s(buf, "%u/%i", m_month, m_year);
        res += buf;
    }
    else
    {
        assert(m_month >= 1 && m_month <= 12);

        char buf[256];
        sprintf_s(buf, "%u/%u/%i", m_month, m_day, m_year);
        res += buf;
    }

    if (m_plural)
        res += "'s";

    if (m_fuzzy)
        res += "?";

    if (m_approx)
        res += " (approximate)";

    if (m_estimated)
        res += " (estimated)";

    return res;
}

// Parses basic dates (not ranges). Works with dates returned by get_string().
// Date can end in "(approximate)", "(estimated)", "?", or "'s".
// 2 digit dates converted to 1900+.
// Supports year, month/year, or month/day/year.
bool event_date::parse(const char* pStr, bool fix_20century_dates)
{
    clear();

    std::string temp(pStr);

    string_trim(temp);

    if (!temp.size())
        return false;

    if (isalpha(temp[0]))
    {
        uint32_t i;
        for (i = 0; i < cTotalPrefixes; i++)
            if (string_begins_with(temp, g_date_prefix_strings[i]))
                break;
        if (i == cTotalPrefixes)
            return false;

        temp.erase(0, strlen(g_date_prefix_strings[i]));

        m_prefix = static_cast<date_prefix_t>(i);
    }

    string_trim(temp);

    if (!temp.size())
        return false;

    if (string_ends_in(temp, "(approximate)"))
    {
        m_approx = true;
        temp.resize(temp.size() - strlen("(approximate)"));
    }
    else if (string_ends_in(temp, "(estimated)"))
    {
        m_estimated = true;
        temp.resize(temp.size() - strlen("(estimated)"));
    }

    string_trim(temp);

    if (!temp.size())
        return false;

    if (string_ends_in(temp, "'s"))
    {
        m_plural = true;
        temp.resize(temp.size() - 2);

        string_trim(temp);
    }

    if (string_ends_in(temp, "?"))
    {
        m_fuzzy = true;
        temp.resize(temp.size() - 1);

        string_trim(temp);
    }

    if (!temp.size())
        return false;

    int num_slashes = 0;
    std::string date_strs[3];

    for (size_t i = 0; i < temp.size(); i++)
    {
        if (temp[i] == '/')
        {
            num_slashes++;
            if (num_slashes == 3)
                return false;
        }
        else if (isdigit(temp[i]))
        {
            date_strs[num_slashes] += temp[i];
        }
        else
        {
            return false;
        }
    }

    if (num_slashes == 0)
    {
        m_year = atoi(date_strs[0].c_str());
    }
    else if (num_slashes == 1)
    {
        m_month = atoi(date_strs[0].c_str());
        if ((m_month < 1) || (m_month > 12))
            return false;

        m_year = atoi(date_strs[1].c_str());
    }
    else
    {
        m_month = atoi(date_strs[0].c_str());
        if ((m_month < 1) || (m_month > 12))
            return false;

        m_day = atoi(date_strs[1].c_str());
        if ((m_day < 1) || (m_day > 31))
            return false;

        m_year = atoi(date_strs[2].c_str());
    }
    
    if (fix_20century_dates)
    {
        if ((m_year >= 1) && (m_year <= 99))
            m_year += 1900;
    }

    if ((m_year < 0) || (m_year > 2100))
        return false;

    return true;
}

// More advanced date range parsing, used for converting the Eberhart timeline.
// Note this doesn't support "'s", "(approximate)", "(estimated)", or converting 2 digit years to 1900'.
bool event_date::parse_eberhart_date_range(std::string date,
    event_date& begin_date,
    event_date& end_date, event_date& alt_date,
    int required_year)
{
    begin_date.clear();
    end_date.clear();
    alt_date.clear();

    if (!date.size())
        return false;

    string_trim(date);

    // First change Unicode EN DASH (e2 80 93) to '-'
    std::string fixed_date;
    for (uint32_t i = 0; i < date.size(); i++)
    {
        if (((i + 2) < date.size()) && ((uint8_t)date[i] == 0xE2) && ((uint8_t)date[i + 1] == 0x80) && ((uint8_t)date[i + 2] == 0x93))
        {
            fixed_date.push_back('-');
            i += 2;
        }
        else
            fixed_date.push_back(date[i]);
    }
    date.swap(fixed_date);

    // Now tokenize the input
    string_vec tokens;

    const int MIN_YEAR = 100, MAX_YEAR = 2050;

    {
        bool in_token = false;
        uint32_t ofs = 0;
        std::string cur_token;
        while (ofs < date.size())
        {
            const uint8_t c = date[ofs];

            if ((c == ' ') || (c == '(') || (c == ')') || (c == ','))
            {
                if (in_token)
                {
                    tokens.push_back(cur_token);
                    cur_token.clear();
                    in_token = false;
                }
            }
            else if (c == '-')
            {
                if (in_token)
                {
                    tokens.push_back(cur_token);
                    cur_token.clear();
                    in_token = false;
                }

                tokens.push_back("-");
            }
            else
            {
                cur_token.push_back((char)c);
                in_token = true;

                if ((cur_token == "mid") || (cur_token == "Mid"))
                {
                    if ((ofs + 1) < date.size())
                    {
                        // Fix "Mid-December" by slamming the upcoming dash to space.
                        if (date[ofs + 1] == '-')
                            date[ofs + 1] = ' ';
                    }
                }
            }

            ofs++;
        }

        if (in_token)
        {
            tokens.push_back(cur_token);
            cur_token.clear();
            in_token = false;
        }
    }

    // Combine together separate tokens for "Early summer" into a single token to simplify the next loop.
    string_vec new_tokens;
    for (uint32_t i = 0; i < tokens.size(); i++)
    {
        bool processed_flag = false;

        if (((i + 1) < tokens.size()) && isalpha((uint8_t)tokens[i][0]) && isalpha((uint8_t)tokens[i + 1][0]))
        {
            uint32_t a;
            for (a = cEarly; a <= cLate; a++)
                if (string_begins_with(tokens[i], g_date_prefix_strings[a]))
                    break;

            uint32_t b;
            for (b = cSpring; b <= cWinter; b++)
                if (string_begins_with(tokens[i + 1], g_date_prefix_strings[b]))
                    break;

            if ((a <= cLate) && (b <= cWinter))
            {
                new_tokens.push_back(tokens[i] + " " + tokens[i + 1]);

                i++;

                processed_flag = true;
            }
        }

        if (!processed_flag)
        {
            new_tokens.push_back(tokens[i]);
        }
    }

    tokens.swap(new_tokens);

    // Process each token individually, using a simple state machine.
    uint32_t cur_token = 0;
    bool inside_end = false;
    bool inside_alt = false;

    while (cur_token < tokens.size())
    {
        std::string& s = tokens[cur_token];
        if (!s.size())
            return false;

        if (s[0] == '-')
        {
            if (s.size() != 1)
                return false;

            if (inside_alt)
                return false;

            if (inside_end)
                return false;

            inside_end = true;
        }
        else if (isdigit((uint8_t)s[0]))
        {
            event_date& d = inside_alt ? alt_date : (inside_end ? end_date : begin_date);

            if (string_ends_in(s, "?"))
            {
                if (d.m_fuzzy)
                    return false;

                d.m_fuzzy = true;

                s.pop_back();
            }

            int val = atoi(s.c_str());
            if ((!val) || (val == INT_MIN) || (val == INT_MAX))
                return false;

            char buf[32];
            sprintf_s(buf, "%i", val);
            if (strlen(buf) != s.size())
                return false;

            if (d.m_month != -1)
            {
                if ((d.m_day != -1) || (d.m_prefix != cNoPrefix) || (val >= MIN_YEAR))
                {
                    if (d.m_year != -1)
                        return false;
                    if ((val < MIN_YEAR) || (val > MAX_YEAR))
                        return false;

                    if ((!inside_end) && (!inside_alt) && (required_year != -1))
                    {
                        if (val != required_year)
                            return false;
                    }

                    d.m_year = val;
                }
                else
                {
                    if ((val < 1) || (val > 31))
                        return false;

                    if (d.m_day != -1)
                        return false;

                    d.m_day = val;
                }
            }
            else
            {
                if ((inside_end || inside_alt) && (begin_date.m_month != -1) && (val <= 31))
                {
                    // Handle cases like "January 20-25" or "January 20 or 25".

                    if (d.m_month != -1)
                        return false;

                    d.m_month = begin_date.m_month;

                    if ((val < 1) || (val > 31))
                        return false;

                    if (d.m_day != -1)
                        return false;
                    d.m_day = val;
                }
                else
                {
                    if (d.m_year != -1)
                        return false;
                    if ((val < MIN_YEAR) || (val > MAX_YEAR))
                        return false;

                    if ((!inside_end) && (!inside_alt) && (required_year != -1))
                    {
                        if (val != required_year)
                            return false;
                    }

                    d.m_year = val;
                }
            }
        }
        else if (isalpha((uint8_t)s[0]))
        {
            if (string_begins_with(s, "or"))
            {
                if (s.size() != 2)
                    return false;

                if (inside_alt)
                    return false;

                inside_alt = true;
                inside_end = false;
            }
            else
            {
                event_date& d = inside_alt ? alt_date : (inside_end ? end_date : begin_date);

                if (string_ends_in(s, "?"))
                {
                    if (d.m_fuzzy)
                        return false;

                    d.m_fuzzy = true;

                    s.pop_back();
                }

                int month = determine_month(s);
                if (month >= 0)
                {
                    assert(month <= 11);

                    if (s.size() != strlen(g_full_months[month]))
                        return false;

                    if (d.m_month != -1)
                        return false;

                    d.m_month = month + 1;
                }
                else
                {
                    uint32_t i;
                    for (i = 0; i < cTotalPrefixes; i++)
                        if (string_begins_with(s, g_date_prefix_strings[i]))
                            break;
                    if (i == cTotalPrefixes)
                        return false;

                    if (s.size() != strlen(g_date_prefix_strings[i]))
                        return false;

                    if (d.m_prefix != -1)
                        return false;

                    d.m_prefix = static_cast<date_prefix_t>(i);
                }
            }
        }
        else
        {
            return false;
        }

        cur_token++;
    }

    // If there's no begin date, then error
    if ((begin_date.m_year == -1) && (begin_date.m_month == -1) && (begin_date.m_prefix == cNoPrefix))
        return false;

    // Check for no begin year specified
    if (begin_date.m_year == -1)
        begin_date.m_year = required_year;

    // Check for no end year specified
    if ((end_date.m_year == -1) && ((end_date.m_prefix != cNoPrefix) || (end_date.m_month != -1)))
        end_date.m_year = required_year;

    // Check for no alt year specified
    if ((inside_alt) && (alt_date.m_year == -1) && ((alt_date.m_prefix != cNoPrefix) || (alt_date.m_month != -1)))
        alt_date.m_year = required_year;

    if (!check_date_prefix(begin_date))
        return false;
    if (!check_date_prefix(end_date))
        return false;
    if (!check_date_prefix(alt_date))
        return false;

    return true;
}

// Note the returned date may be invalid. It's only intended for sorting/comparison purposes against other sort dates.
void event_date::get_sort_date(int& year, int& month, int& day) const
{
    year = m_year;
    month = 0;
    day = 0;

    if (m_month == -1)
    {
        // All we have is a year, no month or date supplied.
        if (m_plural)
        {
            const bool is_century = (m_year % 100) == 0;
            const bool is_decade = (m_year % 10) == 0;

            // 1900's, 1910's, 1800's etc.
            if (m_prefix == cEarly)
            {
                if (is_century)
                    year += 10;
                else if (is_decade)
                    year += 1;
            }
            else if (m_prefix == cMiddleOf)
            {
                if (is_century)
                    year += 50;
                else if (is_decade)
                    year += 5;
            }
            else if (m_prefix == cLate)
            {
                if (is_century)
                    year += 80;
                else if (is_decade)
                    year += 8;
            }
            else if (m_prefix == cEndOf)
            {
                if (is_century)
                    year += 90;
                else if (is_decade)
                    year += 9;
            }
            else
            {
                // 1980's goes before 1980
                day = -1;
            }
        }
        else
        {
            // 1900, 1910, 1800 etc.
            switch (m_prefix)
            {
            case cEarlySpring:
            {
                month = 3;
                day = 1;
                break;
            }
            case cEarlySummer:
            {
                month = 6;
                day = 1;
                break;
            }
            case cEarlyAutumn:
            {
                month = 9;
                day = 1;
                break;
            }
            case cEarlyFall:
            {
                month = 9;
                day = 1;
                break;
            }
            case cEarlyWinter:
            {
                month = 12;
                day = 1;
                break;
            }
            case cMidSpring:
            {
                month = 4;
                day = 1;
                break;
            }
            case cMidSummer:
            {
                month = 7;
                day = 1;
                break;
            }
            case cMidAutumn:
            {
                month = 10;
                day = 1;
                break;
            }
            case cMidFall:
            {
                month = 10;
                day = 1;
                break;
            }
            case cMidWinter:
            {
                month = 1;
                day = 1;
                break;
            }
            case cLateSpring:
            {
                month = 5;
                day = 15;
                break;
            }
            case cLateSummer:
            {
                month = 8;
                day = 15;
                break;
            }
            case cLateAutumn:
            {
                month = 11;
                day = 15;
                break;
            }
            case cLateFall:
            {
                month = 11;
                day = 15;
                break;
            }
            case cLateWinter:
            {
                month = 2;
                day = 15;
                break;
            }
            case cEarly:
            {
                day = 1;
                break;
            }
            case cSpring:
            {
                month = 3;
                day = 20;
                break;
            }
            case cSummer:
            {
                month = 6;
                day = 21;
                break;
            }
            case cMiddleOf:
            {
                month = 6;
                day = 15;
                break;
            }
            case cAutumn:
            {
                month = 9;
                day = 23;
                break;
            }
            case cFall:
            {
                month = 9;
                day = 23;
                break;
            }
            case cLate:
            {
                month = 10;
                day = 15;
                break;
            }
            case cWinter:
            {
                month = 12;
                day = 21;
                break;
            }
            case cEndOf:
            {
                month = 12;
                day = 1;
                break;
            }
            default:
                break;
            }
        }
    }
    else if (m_day == -1)
    {
        // We have a year and a month, but no date
        month = m_month;

        // 1/1900, 4/1910, 12/1805 etc.
        switch (m_prefix)
        {
        case cEarly:
        {
            day = 2;
            break;
        }
        case cMiddleOf:
        {
            day = 15;
            break;
        }
        case cLate:
        {
            day = 25;
            break;
        }
        case cEndOf:
        {
            day = 28;
            break;
        }
        default:
            break;
        }
    }
    else
    {
        month = m_month;
        day = m_day;
    }
}

// Compares two timeline dates. true if lhs < rhs
bool event_date::compare(const event_date& lhs, const event_date& rhs)
{
    int lhs_year, lhs_month, lhs_day;
    lhs.get_sort_date(lhs_year, lhs_month, lhs_day);

    int rhs_year, rhs_month, rhs_day;
    rhs.get_sort_date(rhs_year, rhs_month, rhs_day);

    if (lhs_year < rhs_year)
        return true;
    else if (lhs_year == rhs_year)
    {
        if (lhs_month < rhs_month)
            return true;
        else if (lhs_month == rhs_month)
        {
            if (lhs_day < rhs_day)
                return true;
        }
    }

    return false;
}

bool event_date::check_date_prefix(const event_date& date)
{
    // Prefix sanity checks
    if (date.m_prefix != cNoPrefix)
    {
        // Can't specify a specific day if you've given us a prefix.
        if (date.m_day != -1)
            return false;

        if (is_season(date.m_prefix))
        {
            // Can't specify an explicit month if you've given us a season.
            if (date.m_month != -1)
                return false;
        }
    }
    return true;
}

bool timeline_event::operator==(const timeline_event& rhs) const
{
#define COMP(X) if (X != rhs.X) return false;
    COMP(m_date_str);
    COMP(m_time_str);
    COMP(m_alt_date_str);
    COMP(m_end_date_str);
    COMP(m_begin_date);
    COMP(m_end_date);
    COMP(m_alt_date);
    COMP(m_desc);
    COMP(m_type);
    COMP(m_refs);
    COMP(m_locations);
    COMP(m_attributes);
    COMP(m_see_also);
    COMP(m_rocket_type);
    COMP(m_rocket_altitude);
    COMP(m_rocket_range);
    COMP(m_atomic_type);
    COMP(m_atomic_kt);
    COMP(m_atomic_mt);
    COMP(m_source_id);
    COMP(m_source);
    COMP(m_udb_data);
#undef COMP
    return true;
}

bool timeline_event::operator!=(const timeline_event& rhs) const
{
    return !(*this == rhs);
}

bool timeline_event::operator< (const timeline_event& rhs) const
{
    return event_date::compare(m_begin_date, rhs.m_begin_date);
}

void timeline_event::print(FILE* pFile) const
{
    fprintf(pFile, "**Date:** %s  \n", m_date_str.c_str());
    if (m_alt_date_str.size())
        fprintf(pFile, "**Alternate date:** %s  \n", m_alt_date_str.c_str());

    if (m_time_str.size())
        fprintf(pFile, "**Time:** %s  \n", m_time_str.c_str());

    if (m_end_date_str.size())
        fprintf(pFile, "**End date:** %s  \n", m_end_date_str.c_str());

    for (uint32_t i = 0; i < m_locations.size(); i++)
        fprintf(pFile, "**Location:** %s  \n", m_locations[i].c_str());

    fprintf(pFile, "**Description:** %s  \n", m_desc.c_str());

    for (uint32_t i = 0; i < m_type.size(); i++)
        fprintf(pFile, "**Type:** %s  \n", m_type[i].c_str());

    for (uint32_t i = 0; i < m_refs.size(); i++)
        fprintf(pFile, "**Reference:** %s  \n", m_refs[i].c_str());
        
    if (m_source.size() && m_source_id.size())
    {
        fprintf(pFile, "**Source:** %s, **ID:** %s  \n", m_source.c_str(), m_source_id.c_str());
    }
    else
    {
        if (m_source.size())
            fprintf(pFile, "**Source:** %s  \n", m_source.c_str());
        if (m_source_id.size())
            fprintf(pFile, "**Source ID:** %s  \n", m_source_id.c_str());
    }

    if (m_attributes.size())
    {
        fprintf(pFile, "  \n**Attributes:** ");

        for (uint32_t i = 0; i < m_attributes.size(); i++)
        {
            fprintf(pFile, "%s", m_attributes[i].c_str());

            if (i != (m_attributes.size() - 1))
                fprintf(pFile, ", ");
        }

        fprintf(pFile, "  \n");
    }

    for (uint32_t i = 0; i < m_see_also.size(); i++)
        fprintf(pFile, "**See also:** %s  \n", m_see_also[i].c_str());

    if (m_rocket_type.size())
        fprintf(pFile, "**Rocket type:** %s  \n", m_rocket_type.c_str());
    if (m_rocket_altitude.size())
        fprintf(pFile, "**Rocket altitude:** %s  \n", m_rocket_altitude.c_str());
    if (m_rocket_range.size())
        fprintf(pFile, "**Rocket range:** %s  \n", m_rocket_range.c_str());

    if (m_atomic_type.size())
        fprintf(pFile, "**Atomic type:** %s  \n", m_atomic_type.c_str());
    if (m_atomic_kt.size())
        fprintf(pFile, "**Atomic KT:** %s  \n", m_atomic_kt.c_str());
    if (m_atomic_mt.size())
        fprintf(pFile, "**Atomic MT:** %s  \n", m_atomic_mt.c_str());
                
    if (m_udb_data.size())
    {
        fprintf(pFile, "  \n**UDB Data:** ");
        
        uint32_t total_printed = 0;
        for (const auto& x : m_udb_data)
        {
            fprintf(pFile, "**%s:** \"%s\"", x.first.c_str(), x.second.c_str());
            total_printed++;

            if (total_printed != m_udb_data.size())
            {
                fprintf(pFile, ", ");
            }
        }
        if (total_printed)
            fprintf(pFile, "  \n");
    }
}

void timeline_event::from_json(const json& obj, const char* pSource_override, bool fix_20century_dates)
{
    auto date = obj.find("date");
    auto alt_date = obj.find("alt_date");
    auto time = obj.find("time");
    auto end_date = obj.find("end_date");
    auto desc = obj.find("desc");
    auto location = obj.find("location");
    auto ref = obj.find("ref");
    auto type = obj.find("type");
    auto attributes = obj.find("attributes");
    auto atomic_kt = obj.find("atomic_kt");
    auto atomic_mt = obj.find("atomic_mt");
    auto atomic_type = obj.find("atomic_type");
    auto rocket_type = obj.find("rocket_type");
    auto see_also = obj.find("see_also");
    auto rocket_altitude = obj.find("rocket_altitude");
    auto rocket_range = obj.find("rocket_range");
    auto source_id = obj.find("source_id");
    auto source = obj.find("source");
    
    if (desc == obj.end())
        panic("Missing desc");

    if (!desc->is_string())
        panic("Invalid desc");

    if ((date == obj.end()) || (!date->is_string()))
        panic("Missing date");

    if (type != obj.end() && !type->is_string() && !type->is_array())
        panic("Invalid type");

    if (end_date != obj.end() && !end_date->is_string())
        panic("Invalid end_date");

    if (alt_date != obj.end() && !alt_date->is_string())
        panic("Invalid alt_date");

    if (time != obj.end() && !time->is_string())
        panic("Invalid time");

    m_date_str = (*date);
    if (!m_begin_date.parse(m_date_str.c_str(), fix_20century_dates))
        panic("Failed parsing date %s\n", m_date_str.c_str());
        
    if (end_date != obj.end())
    {
        m_end_date_str = (*end_date);

        if (!m_end_date.parse(m_end_date_str.c_str(), fix_20century_dates))
            panic("Failed parsing end date %s\n", m_end_date_str.c_str());
    }

    if (alt_date != obj.end())
    {
        m_alt_date_str = (*alt_date);

        if (!m_alt_date.parse(m_alt_date_str.c_str(), fix_20century_dates))
            panic("Failed parsing alt date %s\n", m_alt_date_str.c_str());
    }

    if (time != obj.end())
        m_time_str = (*time);

    if (type != obj.end())
    {
        if (type->is_string())
        {
            m_type.resize(1);
            m_type[0] = (*type);
        }
        else
        {
            m_type.resize(type->size());
            for (uint32_t j = 0; j < type->size(); j++)
            {
                if (!(*type)[j].is_string())
                    panic("Invalid type");

                m_type[j] = (*type)[j];
            }
        }
    }

    m_desc = (*desc);

    if (source_id != obj.end())
    {
        if (!source_id->is_string())
            panic("Invalid source ID");

        m_source_id = (*source_id);
    }

    if (location != obj.end())
    {
        if (location->is_array())
        {
            for (uint32_t j = 0; j < location->size(); j++)
            {
                const auto& loc_arr_entry = (*location)[j];

                if (!loc_arr_entry.is_string())
                    panic("Invalid location");

                m_locations.push_back(loc_arr_entry);
            }
        }
        else
        {
            if (!location->is_string())
                panic("Invalid location");

            m_locations.push_back((*location));
        }
    }

    if (ref != obj.end())
    {
        if (ref->is_array())
        {
            for (uint32_t j = 0; j < ref->size(); j++)
            {
                const auto& ref_arr_entry = (*ref)[j];

                if (!ref_arr_entry.is_string())
                    panic("Invalid ref");

                m_refs.push_back(ref_arr_entry);
            }
        }
        else
        {
            if (!ref->is_string())
                panic("Invalid ref");

            m_refs.push_back((*ref));
        }
    }

    if (atomic_kt != obj.end())
    {
        if (!atomic_kt->is_string())
            panic("Invalid atomic_kt");
        m_atomic_kt = (*atomic_kt);
    }

    if (atomic_mt != obj.end())
    {
        if (!atomic_mt->is_string())
            panic("Invalid atomic_mt");
        m_atomic_mt = (*atomic_mt);
    }

    if (atomic_type != obj.end())
    {
        if (!atomic_type->is_string())
            panic("Invalid atomic_type");
        m_atomic_type = (*atomic_type);
    }

    if (rocket_type != obj.end())
    {
        if (!rocket_type->is_string())
            panic("Invalid rocket_type");
        m_rocket_type = (*rocket_type);
    }

    if (rocket_altitude != obj.end())
    {
        if (!rocket_altitude->is_string())
            panic("Invalid rocket_altitude");
        m_rocket_altitude = (*rocket_altitude);
    }

    if (rocket_range != obj.end())
    {
        if (!rocket_range->is_string())
            panic("Invalid rocket_range");
        m_rocket_range = (*rocket_range);
    }

    if (see_also != obj.end())
    {
        if (see_also->is_array())
        {
            for (uint32_t j = 0; j < see_also->size(); j++)
            {
                const auto& see_also_array_entry = (*see_also)[j];

                if (!see_also_array_entry.is_string())
                    panic("Invalid see_also");

                m_see_also.push_back(see_also_array_entry);
            }
        }
        else
        {
            if (!see_also->is_string())
                panic("Invalid see_also");

            m_see_also.push_back((*see_also));
        }
    }

    if (attributes != obj.end())
    {
        if (attributes->is_array())
        {
            for (uint32_t j = 0; j < attributes->size(); j++)
            {
                const auto& attr_entry = (*attributes)[j];

                if (!attr_entry.is_string())
                    panic("Invalid attributes");

                m_attributes.push_back(attr_entry);
            }
        }
        else
        {
            if (!attributes->is_string())
                panic("Invalid attributes");

            m_attributes.push_back(*attributes);
        }
    }

    if (pSource_override)
        m_source = pSource_override;
    else if (source != obj.end())
    {
        if (!source->is_string())
            panic("Invalid source");

        m_source = (*source);
    }

    m_udb_data.clear();

    const json::const_iterator udb_data = obj.find("udb");
    if (udb_data != obj.end())
    {
        if (!udb_data->is_object())
            panic("Expected udb object");

        for (auto x = udb_data->begin(); x != udb_data->end(); ++x)
        {
            if (!x->is_string())
                panic("Expected string");

            if (!x.key().size() || !x.value().size())
                panic("Empty strings");

            m_udb_data.push_back(std::make_pair(x.key(), x.value()));
        }
    }
}

void timeline_event::to_json(json& j) const
{
    j = json::object();

    j["date"] = m_date_str;
    j["desc"] = m_desc;

    if (m_alt_date_str.size())
        j["alt_date"] = m_alt_date_str;

    if (m_end_date_str.size())
        j["end_date"] = m_end_date_str;

    if (m_time_str.size())
        j["time"] = m_time_str;

    if (m_type.size() > 1)
        j["type"] = m_type;
    else if (m_type.size())
        j["type"] = m_type[0];

    if (m_refs.size() > 1)
        j["ref"] = m_refs;
    else if (m_refs.size())
        j["ref"] = m_refs[0];

    if (m_locations.size() > 1)
        j["location"] = m_locations;
    else if (m_locations.size())
        j["location"] = m_locations[0];

    if (m_attributes.size() > 1)
        j["attributes"] = m_attributes;
    else if (m_attributes.size())
        j["attributes"] = m_attributes[0];

    if (m_see_also.size() > 1)
        j["see_also"] = m_see_also;
    else if (m_see_also.size())
        j["see_also"] = m_see_also[0];

    if (m_rocket_type.size())
        j["rocket_type"] = m_rocket_type;
    if (m_rocket_altitude.size())
        j["rocket_altitude"] = m_rocket_altitude;
    if (m_rocket_range.size())
        j["rocket_range"] = m_rocket_range;

    if (m_atomic_type.size())
        j["atomic_type"] = m_atomic_type;
    if (m_atomic_kt.size())
        j["atomic_kt"] = m_atomic_kt;
    if (m_atomic_mt.size())
        j["atomic_mt"] = m_atomic_mt;

    if (m_source_id.size())
        j["source_id"] = m_source_id;

    if (m_source.size())
        j["source"] = m_source;

    if (m_udb_data.size())
    {
        auto &udb_obj = (j["udb"] = json::object());
        for (const auto& x : m_udb_data)
        {
            assert(x.first.size() && x.second.size());

            udb_obj[x.first] = x.second;
        }
    }
}

bool ufo_timeline::write_markdown(const char* pTimeline_filename)
{
    const std::vector<timeline_event>& timeline_events = m_events;

    FILE* pTimeline_file = ufopen(pTimeline_filename, "w");
    if (!pTimeline_file)
        panic("Failed creating file %s", pTimeline_file);

    fputc(UTF8_BOM0, pTimeline_file);
    fputc(UTF8_BOM1, pTimeline_file);
    fputc(UTF8_BOM2, pTimeline_file);
    fprintf(pTimeline_file, "<meta charset=\"utf-8\">\n");

    std::map<int, int> year_histogram;

    fprintf(pTimeline_file, "# <a name=\"Top\">UFO Event Timeline v" TIMELINE_VERSION " - Compiled 2/19/2023</a>\n\n");

    fputs(
        u8R"(An automated compilation by <a href="https://twitter.com/richgel999">Richard Geldreich, Jr.</a> using public data from <a href="https://en.wikipedia.org/wiki/Jacques_Vall%C3%A9e">Dr. Jacques Vall<6C>e</a>,
<a href="https://www.academia.edu/9813787/GOVERNMENT_INVOLVEMENT_IN_THE_UFO_COVER_UP_CHRONOLOGY_based">Pea Research</a>, <a href="http://www.cufos.org/UFO_Timeline.html">George M. Eberhart</a>,
<a href="https://en.wikipedia.org/wiki/Richard_H._Hall">Richard H. Hall</a>, <a href="https://web.archive.org/web/20160821221627/http://www.ufoinfo.com/onthisday/sametimenextyear.html">Dr. Donald A. Johnson</a>,
<a href="https://medium.com/@richgel99/1958-keziah-poster-recreation-completed-82fdb55750d8">Fred Keziah</a>, <a href="https://github.com/richgel999/uap_resources/blob/main/bluebook_uncensored_unknowns_don_berliner.pdf">Don Berliner</a>,
<a href="https://www.openminds.tv/larry-hatch-ufo-database-creator-remembered/42142">Larry Hatch</a>, and [NICAP](https://www.nicap.org/).

## Copyrights: 
- Richard Geldreich, Jr. - Copyright (c) 2023 (all parsed dates and events marked \"maj2\" unless otherwise attributed)
- Dr. Jacques F. Vall<EFBFBD>e - Copyright (c) 1993
- LeRoy Pea - Copyright (c) 9/8/1988 (updated 3/17/2005)
- George M. Eberhart - Copyright (c) 2022
- Dr. Donald A. Johnson - Copyright (c) 2012
- Fred Keziah - Copyright (c) 1958
- Larry Hatch - Copyright (c) 1992-2002

## Update History:
- v1.12: Added \*U\* database record data, using a custom event description decoder to handle his 1k+ abbreviations and custom syntax
- v1.11: Crawled all ~10.5k unique URL's in this timeline using [curl](https://curl.se/) and fixed dead URL's to use archive.org.
- v1.10: Added NIPCAP DB data.

## Important Notes:
Best viewed on a desktop/laptop, not a mobile device.

The majority of the events in this chronology are sighting related, however it's important to be aware that this is a timeline of 
UFO/UAP related _events_, not necessarily or exclusively UFO _sightings_. 

Some sighting reports or events appear multiple times in this timeline because they appear in more than one data source. I view this as a useful feature.

Currently, the events are not sorted by time of day, only by date. Some sources have separate "time" fields, but most don't. This will be fixed once the event times are automatically extracted from the description fields.

A few events don't have firm dates, for example "Summer of 1947", or "Late July 1952". In these instances the compilation code uses fixed dates I selected for date sorting purposes. (See the code for the specific dates.)

## Source Code:
This website is created automatically using a [C++](https://en.wikipedia.org/wiki/C%2B%2B) command line tool called <20>ufojson<6F>. It parses the raw text and [Markdown](https://en.wikipedia.org/wiki/Markdown) source data to [JSON format](https://www.json.org/json-en.html), which is then converted to a single large web page using [pandoc](https://pandoc.org/). This tool's source code and all of the raw source and JSON data is located [here on github](https://github.com/richgel999/ufo_data).)", pTimeline_file);

    fprintf(pTimeline_file, "\n\n## Table of Contents\n\n");

    fprintf(pTimeline_file, "<a href = \"#yearhisto\">Year Histogram</a>\n\n");

    std::set<uint32_t> year_set;
    int min_year = 9999, max_year = -10000;
    for (uint32_t i = 0; i < timeline_events.size(); i++)
    {
        int y;
        year_set.insert(y = timeline_events[i].m_begin_date.m_year);
        min_year = std::min(min_year, y);
        max_year = std::max(max_year, y);
    }

    fprintf(pTimeline_file, "### Years\n");

    uint32_t n = 0;
    for (int y = min_year; y <= max_year; y++)
    {
        if (year_set.find(y) != year_set.end())
        {
            fprintf(pTimeline_file, "<a href=\"#year%i\">%i</a> ", y, y);

            n++;
            if (n == 10)
            {
                fprintf(pTimeline_file, "  \n");
                n = 0;
            }
        }
    }
    fprintf(pTimeline_file, "  \n\n");

    fprintf(pTimeline_file, "## Event Timeline\n");

    int cur_year = -9999;

    for (uint32_t i = 0; i < timeline_events.size(); i++)
    {
        uint32_t hash = crc32((const uint8_t*)timeline_events[i].m_desc.c_str(), timeline_events[i].m_desc.size());
        hash = crc32((const uint8_t*)&timeline_events[i].m_begin_date.m_year, sizeof(timeline_events[i].m_begin_date.m_year), hash);
        hash = crc32((const uint8_t*)&timeline_events[i].m_begin_date.m_month, sizeof(timeline_events[i].m_begin_date.m_month), hash);
        hash = crc32((const uint8_t*)&timeline_events[i].m_begin_date.m_day, sizeof(timeline_events[i].m_begin_date.m_day), hash);

        int year = timeline_events[i].m_begin_date.m_year;
        if ((year != cur_year) && (year > cur_year))
        {
            fprintf(pTimeline_file, "\n---\n\n");
            fprintf(pTimeline_file, "## <a name=\"year%u\">Year: %u</a> <a href=\"#Top\">(Back to Top)</a>\n\n", year, year);

            fprintf(pTimeline_file, "### <a name=\"%08X\">Event %i (%08X)</a>\n", hash, i, hash);

            cur_year = year;
        }
        else
        {
            fprintf(pTimeline_file, "### <a name=\"%08X\"></a> Event %i (%08X)\n", hash, i, hash);
        }

        timeline_events[i].print(pTimeline_file);

        year_histogram[year] = year_histogram[year] + 1;

        fprintf(pTimeline_file, "\n");
    }

    fprintf(pTimeline_file, "\n---\n\n");

    fprintf(pTimeline_file, "#  <a name=\"yearhisto\">Year Histogram</a>\n");

    for (auto it = year_histogram.begin(); it != year_histogram.end(); ++it)
    {
        fprintf(pTimeline_file, "* %i, %i\n", it->first, it->second);
    }

    fclose(pTimeline_file);

    return true;
}

// Load a JSON timeline using nlohmann::json
bool ufo_timeline::load_json(const char* pFilename, bool& utf8_flag, const char* pSource_override, bool fix_20century_dates)
{
    std::vector<timeline_event>& timeline_events = m_events;

    std::vector<uint8_t> buf;

    if (!read_text_file(pFilename, buf, utf8_flag))
        return false;

    if (!buf.size())
        panic("Input file is empty");

    json js;

    bool success = false;
    try
    {
        js = json::parse(buf.begin(), buf.end());
        success = true;
    }
    catch (json::exception& e)
    {
        panic("json::parse() failed (id %i): %s", e.id, e.what());
    }

    if (!js.is_object() || !js.size())
        panic("Invalid JSON");

    auto first_entry = js.begin();

    if (!first_entry->is_array())
        panic("Invalid JSON");

    m_name = first_entry.key();

    const size_t first_event_index = timeline_events.size();
    timeline_events.resize(first_event_index + first_entry->size());

    for (uint32_t i = 0; i < first_entry->size(); i++)
    {
        auto obj = (*first_entry)[i];

        if (!obj.is_object())
            panic("Invalid JSON");

        timeline_events[first_event_index + i].from_json(obj, pSource_override, fix_20century_dates);
    }

    return true;
}