118 lines
3.9 KiB
Python
Executable file
118 lines
3.9 KiB
Python
Executable file
#!/usr/bin/env -S uv run --script
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# /// script
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# dependencies = ["timezonefinder", "pytz"]
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# ///
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"""
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Generate timezone offset lookup table based on longitude.
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Samples at latitudes 0°, 30°N, 30°S and uses most common offset.
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"""
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from timezonefinder import TimezoneFinder
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import pytz
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from datetime import datetime
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from collections import Counter
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OUTPUT_FILE = "src/location/timezone_offsets.zig"
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LATITUDES = [0, 30, -30]
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def get_offset_minutes(tz_name):
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"""Get UTC offset in minutes for a timezone at current time"""
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if not tz_name:
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return 0
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tz = pytz.timezone(tz_name)
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now = datetime.now(tz)
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offset = now.utcoffset()
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return int(offset.total_seconds() / 60)
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def main():
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tf = TimezoneFinder()
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print(f"Generating timezone offset table...")
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print(f"Sampling at latitudes: {LATITUDES}")
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print()
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offsets = []
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for lon in range(-180, 180):
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# Collect offsets from all latitudes
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offset_list = []
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for lat in LATITUDES:
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tz_name = tf.timezone_at(lat=lat, lng=lon)
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offset = get_offset_minutes(tz_name)
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offset_list.append(offset)
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# Find most common offset (handles political boundaries)
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most_common = Counter(offset_list).most_common(1)[0][0]
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offsets.append(most_common)
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if (lon + 180) % 30 == 0:
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print(f"Progress: {lon + 180 + 1}/360 longitudes processed")
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# Write output file
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with open(OUTPUT_FILE, 'w') as f:
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f.write("""// Auto-generated timezone offset table
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// Generated by scripts/generate_timezone_table.py
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//
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// Maps longitude (0-359) to UTC offset in minutes
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// Sampled at latitudes: 0°, 30°N, 30°S and uses most common offset
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//
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// ACCURACY NOTES:
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// - This is a simplified longitude-only lookup for weather display purposes
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// - Samples 3 latitudes per longitude and uses the most common offset
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// - Works well for mid-latitudes (±30°) where most population lives
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// - Can be off by 1-2.5 hours at extreme latitudes (e.g., Russia vs Australia)
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// - Acceptable for "morning/afternoon/evening/night" weather labels
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// - If higher accuracy is needed, modify getTimezoneOffset() to use latitude
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const std = @import("std");
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const Coordinates = @import("../Coordinates.zig");
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/// Timezone offset in minutes from UTC for each degree of longitude (0-359)
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/// Negative values = west of UTC, positive = east of UTC
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pub const timezone_offsets: [360]i16 = .{
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""")
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for offset in offsets:
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f.write(f" {offset},\n")
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f.write("""};
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/// Get timezone offset in minutes for given coordinates
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/// Currently only uses longitude; latitude is available for future improvements
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/// coords: Location coordinates
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/// Returns: offset in minutes from UTC
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pub fn getTimezoneOffset(coords: Coordinates) i16 {
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// Currently only uses longitude (see ACCURACY NOTES above)
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// Latitude could be used in future for better accuracy at extreme latitudes
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_ = coords.latitude;
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// Normalize longitude to 0-359
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const normalized = @mod(@as(i32, @intFromFloat(@round(coords.longitude))) + 180, 360);
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return timezone_offsets[@intCast(normalized)];
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}
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test "timezone offset lookup" {
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// London (0°) should be close to UTC
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const london_offset = getTimezoneOffset(.{ .latitude = 51.5, .longitude = 0.0 });
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try std.testing.expect(london_offset >= -60 and london_offset <= 60);
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// New York (-74°) should be around UTC-5 (-300 minutes)
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const ny_offset = getTimezoneOffset(.{ .latitude = 40.7, .longitude = -74.0 });
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try std.testing.expect(ny_offset >= -360 and ny_offset <= -240);
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// Tokyo (139°) should be around UTC+9 (540 minutes)
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const tokyo_offset = getTimezoneOffset(.{ .latitude = 35.7, .longitude = 139.0 });
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try std.testing.expect(tokyo_offset >= 480 and tokyo_offset <= 600);
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}
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""")
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print(f"\nGenerated {OUTPUT_FILE}")
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print("Running zig fmt...")
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import subprocess
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subprocess.run(["zig", "fmt", OUTPUT_FILE])
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print("Done!")
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if __name__ == "__main__":
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main()
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