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refactor(date): replace most date parsing with zeit functions

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Simon Hartcher 2025-04-23 12:48:53 +10:00
parent e22b4246c1
commit 6028255aa3
1 changed files with 47 additions and 247 deletions
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294
lib/date/src/parsing.zig
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@ -4,137 +4,66 @@
const std = @import("std");
const log = std.log.scoped(.date);
const zeit = @import("zeit");
pub const DateTime = struct { day: u8, month: u8, year: u16, hour: u8, minute: u8, second: u8 };
pub const DateTime = struct {
day: u8,
month: u8,
year: u16,
hour: u8,
minute: u8,
second: u8,
pub fn fromInstant(val: zeit.Instant) DateTime {
return fromTime(val.time());
}
pub fn fromTime(val: zeit.Time) DateTime {
return DateTime{
.day = val.day,
.month = @intFromEnum(val.month),
.year = @intCast(val.year),
.hour = val.hour,
.minute = val.minute,
.second = val.second,
};
}
pub fn time(self: DateTime) zeit.Time {
return zeit.Time{
.day = @intCast(self.day),
.month = @enumFromInt(self.month),
.year = self.year,
.hour = @intCast(self.hour),
.minute = @intCast(self.minute),
.second = @intCast(self.second),
};
}
pub fn instant(self: DateTime) !zeit.Instant {
return try zeit.instant(.{ .source = .{ .time = self.time() } });
}
};
const SECONDS_PER_DAY = 86400; //* 24* 60 * 60 */
const DAYS_PER_YEAR = 365; //* Normal year (no leap year) */
pub fn timestampToDateTime(timestamp: i64) DateTime {
// aus https://de.wikipedia.org/wiki/Unixzeit
const unixtime = @as(u64, @intCast(timestamp));
const DAYS_IN_4_YEARS = 1461; //* 4*365 + 1 */
const DAYS_IN_100_YEARS = 36524; //* 100*365 + 25 - 1 */
const DAYS_IN_400_YEARS = 146097; //* 400*365 + 100 - 4 + 1 */
const DAY_NUMBER_ADJUSTED_1970_01_01 = 719468; //* Day number relates to March 1st */
var dayN: u64 = DAY_NUMBER_ADJUSTED_1970_01_01 + unixtime / SECONDS_PER_DAY;
const seconds_since_midnight: u64 = unixtime % SECONDS_PER_DAY;
var temp: u64 = 0;
// Leap year rules for Gregorian Calendars
// Any year divisible by 100 is not a leap year unless also divisible by 400
temp = 4 * (dayN + DAYS_IN_100_YEARS + 1) / DAYS_IN_400_YEARS - 1;
var year = @as(u16, @intCast(100 * temp));
dayN -= DAYS_IN_100_YEARS * temp + temp / 4;
// For Julian calendars, each year divisible by 4 is a leap year
temp = 4 * (dayN + DAYS_PER_YEAR + 1) / DAYS_IN_4_YEARS - 1;
year += @as(u16, @intCast(temp));
dayN -= DAYS_PER_YEAR * temp + temp / 4;
// dayN calculates the days of the year in relation to March 1
var month = @as(u8, @intCast((5 * dayN + 2) / 153));
const day = @as(u8, @intCast(dayN - (@as(u64, @intCast(month)) * 153 + 2) / 5 + 1));
// 153 = 31+30+31+30+31 Days for the 5 months from March through July
// 153 = 31+30+31+30+31 Days for the 5 months from August through December
// 31+28 Days for January and February (see below)
// +2: Rounding adjustment
// +1: The first day in March is March 1st (not March 0)
month += 3; // Convert from the day that starts on March 1st, to a human year */
if (month > 12) { // months 13 and 14 become 1 (January) und 2 (February) of the next year
month -= 12;
year += 1;
}
const hours = @as(u8, @intCast(seconds_since_midnight / 3600));
const minutes = @as(u8, @intCast(seconds_since_midnight % 3600 / 60));
const seconds = @as(u8, @intCast(seconds_since_midnight % 60));
return DateTime{ .day = day, .month = month, .year = year, .hour = hours, .minute = minutes, .second = seconds };
pub fn timestampToDateTime(timestamp: zeit.Seconds) DateTime {
const ins = zeit.instant(.{ .source = .{ .unix_timestamp = timestamp } }) catch @panic("Failed to create instant from timestamp");
return DateTime.fromInstant(ins);
}
pub fn parseEnglishToTimestamp(data: []const u8) !i64 {
return try dateTimeToTimestamp(try parseEnglishToDateTime(data));
}
const EnglishParsingState = enum { Start, Day, Month, Year, Hour, Minute, Second, End };
/// Converts a string to a timestamp value. May not handle dates before the
/// epoch. Dates should look like "Fri, 03 Jun 2022 18:12:36 GMT"
pub fn parseEnglishToDateTime(data: []const u8) !DateTime {
// Fri, 03 Jun 2022 18:12:36 GMT
if (!std.mem.endsWith(u8, data, "GMT")) return error.InvalidFormat;
var start: usize = 0;
var state = EnglishParsingState.Start;
// Anything not explicitly set by our string would be 0
var rc = DateTime{ .year = 0, .month = 0, .day = 0, .hour = 0, .minute = 0, .second = 0 };
for (data, 0..) |ch, i| {
switch (ch) {
',' => {},
' ', ':' => {
// State transition
// We're going to coerce and this might not go well, but we
// want the compiler to create checks, so we'll turn on
// runtime safety for this block, forcing checks in ReleaseSafe
// ReleaseFast modes.
const next_state = try endEnglishState(state, &rc, data[start..i]);
state = next_state;
start = i + 1;
},
else => {}, // We need to be pretty trusting on this format...
}
}
return rc;
const ins = try zeit.instant(.{ .source = .{ .rfc1123 = data } });
return DateTime.fromInstant(ins);
}
fn endEnglishState(current_state: EnglishParsingState, date: *DateTime, prev_data: []const u8) !EnglishParsingState {
var next_state: EnglishParsingState = undefined;
log.debug("endEnglishState. Current state '{}', data: {s}", .{ current_state, prev_data });
// Using two switches is slightly less efficient, but more readable
switch (current_state) {
.End => return error.IllegalStateTransition,
.Start => next_state = .Day,
.Day => next_state = .Month,
.Month => next_state = .Year,
.Year => next_state = .Hour,
.Hour => next_state = .Minute,
.Minute => next_state = .Second,
.Second => next_state = .End,
}
switch (current_state) {
.Year => date.year = try std.fmt.parseUnsigned(u16, prev_data, 10),
.Month => date.month = try parseEnglishMonth(prev_data),
.Day => date.day = try std.fmt.parseUnsigned(u8, prev_data, 10),
.Hour => date.hour = try std.fmt.parseUnsigned(u8, prev_data, 10),
.Minute => date.minute = try std.fmt.parseUnsigned(u8, prev_data, 10),
.Second => date.second = try std.fmt.parseUnsigned(u8, prev_data, 10),
.Start => {},
.End => return error.InvalidState,
}
return next_state;
}
fn parseEnglishMonth(data: []const u8) !u8 {
if (std.ascii.startsWithIgnoreCase(data, "Jan")) return 1;
if (std.ascii.startsWithIgnoreCase(data, "Feb")) return 2;
if (std.ascii.startsWithIgnoreCase(data, "Mar")) return 3;
if (std.ascii.startsWithIgnoreCase(data, "Apr")) return 4;
if (std.ascii.startsWithIgnoreCase(data, "May")) return 5;
if (std.ascii.startsWithIgnoreCase(data, "Jun")) return 6;
if (std.ascii.startsWithIgnoreCase(data, "Jul")) return 7;
if (std.ascii.startsWithIgnoreCase(data, "Aug")) return 8;
if (std.ascii.startsWithIgnoreCase(data, "Sep")) return 9;
if (std.ascii.startsWithIgnoreCase(data, "Oct")) return 10;
if (std.ascii.startsWithIgnoreCase(data, "Nov")) return 11;
if (std.ascii.startsWithIgnoreCase(data, "Dec")) return 12;
return error.InvalidMonth;
}
pub fn parseIso8601ToTimestamp(data: []const u8) !i64 {
return try dateTimeToTimestamp(try parseIso8601ToDateTime(data));
}
@ -229,144 +158,15 @@ fn endIsoState(current_state: IsoParsingState, date: *DateTime, prev_data: []con
}
return next_state;
}
pub fn dateTimeToTimestamp(datetime: DateTime) !i64 {
const epoch = DateTime{
.year = 1970,
.month = 1,
.day = 1,
.hour = 0,
.minute = 0,
.second = 0,
};
return secondsBetween(epoch, datetime);
pub fn dateTimeToTimestamp(datetime: DateTime) !zeit.Seconds {
return (try datetime.instant()).unixTimestamp();
}
const DateTimeToTimestampError = error{
DateTimeOutOfRange,
};
fn secondsBetween(start: DateTime, end: DateTime) DateTimeToTimestampError!i64 {
try validateDatetime(start);
try validateDatetime(end);
if (end.year < start.year) return -1 * try secondsBetween(end, start);
if (start.month != 1 or
start.day != 1 or
start.hour != 0 or
start.minute != 0 or
start.second != 0)
{
const seconds_into_start_year = secondsFromBeginningOfYear(
start.year,
start.month,
start.day,
start.hour,
start.minute,
start.second,
);
const new_start = DateTime{
.year = start.year,
.month = 1,
.day = 1,
.hour = 0,
.minute = 0,
.second = 0,
};
return (try secondsBetween(new_start, end)) - seconds_into_start_year;
}
const leap_years_between = leapYearsBetween(start.year, end.year);
const add_days: u1 = 0;
const years_diff = end.year - start.year;
// log.debug("Years from epoch: {d}, Leap years: {d}", .{ years_diff, leap_years_between });
const days_diff: i32 = (years_diff * DAYS_PER_YEAR) + leap_years_between + add_days;
// log.debug("Days with leap year, without month: {d}", .{days_diff});
const seconds_into_year = secondsFromBeginningOfYear(
end.year,
end.month,
end.day,
end.hour,
end.minute,
end.second,
);
return (days_diff * SECONDS_PER_DAY) + @as(i64, seconds_into_year);
}
fn validateDatetime(dt: DateTime) !void {
if (dt.month > 12 or
dt.day > 31 or
dt.hour >= 24 or
dt.minute >= 60 or
dt.second >= 60) return error.DateTimeOutOfRange;
}
fn secondsFromBeginningOfYear(year: u16, month: u8, day: u8, hour: u8, minute: u8, second: u8) u32 {
const current_year_is_leap_year = isLeapYear(year);
const leap_year_days_per_month: [12]u5 = .{ 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
const normal_days_per_month: [12]u5 = .{ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
const days_per_month = if (current_year_is_leap_year) leap_year_days_per_month else normal_days_per_month;
var current_month: usize = 1;
const end_month = month;
var days_diff: u32 = 0;
while (current_month != end_month) {
days_diff += days_per_month[current_month - 1]; // months are 1-based vs array is 0-based
current_month += 1;
}
// log.debug("Days with month, without day: {d}. Day of month {d}, will add {d} days", .{
// days_diff,
// day,
// day - 1,
// });
// We need -1 because we're not actually including the ending day (that's up to hour/minute)
// In other words, days in the month are 1-based, while hours/minutes are zero based
days_diff += day - 1;
// log.debug("Total days diff: {d}", .{days_diff});
var seconds_diff: u32 = days_diff * SECONDS_PER_DAY;
// From here out, we want to get everything into seconds
seconds_diff += @as(u32, hour) * 60 * 60;
seconds_diff += @as(u32, minute) * 60;
seconds_diff += @as(u32, second);
return seconds_diff;
}
fn isLeapYear(year: u16) bool {
if (year % 4 != 0) return false;
if (year % 400 == 0) return true;
if (year % 100 == 0) return false;
return true;
}
fn leapYearsBetween(start_year_inclusive: u16, end_year_exclusive: u16) u16 {
const start = @min(start_year_inclusive, end_year_exclusive);
const end = @max(start_year_inclusive, end_year_exclusive);
var current = start;
// log.debug("Leap years starting from {d}, ending at {d}", .{ start, end });
while (current % 4 != 0 and current < end) {
current += 1;
}
if (current == end) return 0; // No leap years here. E.g. 1971-1973
// We're on a potential leap year, and now we can step by 4
var rc: u16 = 0;
while (current < end) {
if (current % 4 == 0) {
if (current % 100 != 0) {
// log.debug("Year {d} is leap year", .{current});
rc += 1;
current += 4;
continue;
}
// We're on a century, which is normally not a leap year, unless
// it's divisible by 400
if (current % 400 == 0) {
// log.debug("Year {d} is leap year", .{current});
rc += 1;
}
}
current += 4;
}
return rc;
}
fn printDateTime(dt: DateTime) void {
log.debug("{:0>4}-{:0>2}-{:0>2}T{:0>2}:{:0>2}:{:0<2}Z", .{
dt.year,