#!/usr/bin/env -S uv run --script
# /// script
# dependencies = ["timezonefinder", "pytz"]
# ///
"""
Generate timezone offset lookup table based on longitude.
Samples at latitudes 0°, 30°N, 30°S and uses most common offset.
"""

from timezonefinder import TimezoneFinder
import pytz
from datetime import datetime
from collections import Counter

OUTPUT_FILE = "src/location/timezone_offsets.zig"
LATITUDES = [0, 30, -30]

def get_offset_minutes(tz_name):
    """Get UTC offset in minutes for a timezone at current time"""
    if not tz_name:
        return 0
    tz = pytz.timezone(tz_name)
    now = datetime.now(tz)
    offset = now.utcoffset()
    return int(offset.total_seconds() / 60)

def main():
    tf = TimezoneFinder()

    print(f"Generating timezone offset table...")
    print(f"Sampling at latitudes: {LATITUDES}")
    print()

    offsets = []

    for lon in range(-180, 180):
        # Collect offsets from all latitudes
        offset_list = []

        for lat in LATITUDES:
            tz_name = tf.timezone_at(lat=lat, lng=lon)
            offset = get_offset_minutes(tz_name)
            offset_list.append(offset)

        # Find most common offset (handles political boundaries)
        most_common = Counter(offset_list).most_common(1)[0][0]
        offsets.append(most_common)

        if (lon + 180) % 30 == 0:
            print(f"Progress: {lon + 180 + 1}/360 longitudes processed")

    # Write output file
    with open(OUTPUT_FILE, 'w') as f:
        f.write("""// Auto-generated timezone offset table
// Generated by scripts/generate_timezone_table.py
//
// Maps longitude (0-359) to UTC offset in minutes
// Sampled at latitudes: 0°, 30°N, 30°S and uses most common offset
//
// ACCURACY NOTES:
// - This is a simplified longitude-only lookup for weather display purposes
// - Samples 3 latitudes per longitude and uses the most common offset
// - Works well for mid-latitudes (±30°) where most population lives
// - Can be off by 1-2.5 hours at extreme latitudes (e.g., Russia vs Australia)
// - Acceptable for "morning/afternoon/evening/night" weather labels
// - If higher accuracy is needed, modify getTimezoneOffset() to use latitude

const std = @import("std");

const Coordinates = @import("../Coordinates.zig");

/// Timezone offset in minutes from UTC for each degree of longitude (0-359)
/// Negative values = west of UTC, positive = east of UTC
pub const timezone_offsets: [360]i16 = .{
""")

        for offset in offsets:
            f.write(f"    {offset},\n")

        f.write("""};

/// Get timezone offset in minutes for given coordinates
/// Currently only uses longitude; latitude is available for future improvements
/// coords: Location coordinates
/// Returns: offset in minutes from UTC
pub fn getTimezoneOffset(coords: Coordinates) i16 {
    // Currently only uses longitude (see ACCURACY NOTES above)
    // Latitude could be used in future for better accuracy at extreme latitudes
    _ = coords.latitude;

    // Normalize longitude to 0-359
    const normalized = @mod(@as(i32, @intFromFloat(@round(coords.longitude))) + 180, 360);
    return timezone_offsets[@intCast(normalized)];
}

test "timezone offset lookup" {
    // London (0°) should be close to UTC
    const london_offset = getTimezoneOffset(.{ .latitude = 51.5, .longitude = 0.0 });
    try std.testing.expect(london_offset >= -60 and london_offset <= 60);

    // New York (-74°) should be around UTC-5 (-300 minutes)
    const ny_offset = getTimezoneOffset(.{ .latitude = 40.7, .longitude = -74.0 });
    try std.testing.expect(ny_offset >= -360 and ny_offset <= -240);

    // Tokyo (139°) should be around UTC+9 (540 minutes)
    const tokyo_offset = getTimezoneOffset(.{ .latitude = 35.7, .longitude = 139.0 });
    try std.testing.expect(tokyo_offset >= 480 and tokyo_offset <= 600);
}
""")

    print(f"\nGenerated {OUTPUT_FILE}")
    print("Running zig fmt...")
    import subprocess
    subprocess.run(["zig", "fmt", OUTPUT_FILE])
    print("Done!")

if __name__ == "__main__":
    main()