BREAKING CHANGE: the Go module path is now github.com/tiennm99/tiennm99bot,
the default sticker pack is stickers_by_<bot username>, and the health body,
deploy DM, User-Agents and image names say tiennm99bot.
- /duonglich appends a nhuan hint when the queried month is also that
lunar year's leap month and the exact leap date exists
- both commands append a caveat when the result falls in a lunar month
starting or ending on one of the seven razor-edge boundaries from
2072 on (new moon within ~2 minutes of UTC+7 midnight)
- freeze the verified 1800-2199 month structure as golden testdata so
a self-consistent engine change cannot silently shift boundaries
- close known-issues open questions 1 and 2
The mean-cycle lunation estimate in solarToLunar can overshoot by one when
the target day falls just before a new moon whose UTC+7 calendar day rounds
forward; the reference implementation steps back only once and returns day 0
for 13/4/1877, 16/3/1885, 7/5/2054 and 9/4/2062. Loop the step-back until the
month start is on or before the target day.
Tests: extend round-trip to the full 1800-2199 range with day-continuity
checks, pin the 4 overshoot dates, anchor leap-month placement to published
tables (15 leap + 5 no-leap years), and pin the two razor-edge lunations
(20/6/1944, 7/7/1967) verified against published Vietnamese calendars.
/amlich converts duong lich to am lich (defaults to today, Asia/Saigon);
/duonglich converts am lich to duong lich with a nhuan flag for leap
months. Dates accept d, d/m, or d/m/yyyy - missing parts fill from today
in the input's calendar. Conversion is a dependency-free port of Ho Ngoc
Duc's algorithm at UTC+7, with rejection of impossible lunar inputs,
anchored by known Tet/leap-month dates and a 1950-2050 round-trip test.
tiennm99