#!/bin/bash
# Generate timezone offset lookup table based on longitude
# Samples at multiple latitudes to handle political boundaries

set -e

OUTPUT_FILE="src/location/timezone_offsets.zig"
TEMP_FILE=$(mktemp)

# Latitudes to sample (equator, +/-30)
LATITUDES=(0 30 -30)

echo "Generating timezone offset table..."
echo "This will make 1080 API calls (360 longitudes × 3 latitudes)"
echo

# Start the output file
cat > "$TEMP_FILE" << 'EOF'
// Auto-generated timezone offset table
// Generated by scripts/generate_timezone_table.sh
//
// Maps longitude (0-359) to UTC offset in minutes
// Sampled at latitudes: 0°, 30°N, 30°S and uses most common offset

const std = @import("std");

/// 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 = .{
EOF

# For each longitude
for lon in {-180..179}; do
    # Normalize to 0-359 for array index
    array_idx=$((lon + 180))

    echo -n "Processing longitude $lon ($((array_idx + 1))/360)..." >&2

    # Collect offsets from all latitudes
    declare -A offset_counts

    for lat in "${LATITUDES[@]}"; do
        # Query the API
        response=$(curl -s "https://tools.maximmaeder.com/t/get-timezone-by-coordinates/?latitude=$lat&longitude=$lon")

        # Extract offset (format: "UTC+05:30" or "UTC-08:00")
        offset=$(echo "$response" | grep -oP 'UTC[+-]\d{2}:\d{2}' | head -1)

        if [ -z "$offset" ]; then
            echo " failed to get timezone for lat=$lat, lon=$lon" >&2
            continue
        fi

        # Convert to minutes
        sign=$(echo "$offset" | grep -oP '[+-]')
        hours=$(echo "$offset" | grep -oP '\d{2}' | head -1)
        mins=$(echo "$offset" | grep -oP '\d{2}' | tail -1)

        total_mins=$((hours * 60 + mins))
        if [ "$sign" = "-" ]; then
            total_mins=$((total_mins * -1))
        fi

        # Count occurrences
        offset_counts[$total_mins]=$((${offset_counts[$total_mins]:-0} + 1))

        # Rate limit
        sleep 0.1
    done

    # Find most common offset
    max_count=0
    most_common_offset=0
    for offset in "${!offset_counts[@]}"; do
        if [ "${offset_counts[$offset]}" -gt "$max_count" ]; then
            max_count="${offset_counts[$offset]}"
            most_common_offset="$offset"
        fi
    done

    echo " → ${most_common_offset} minutes" >&2

    # Add to array (with comma except for last element)
    if [ "$array_idx" -eq 359 ]; then
        echo "    $most_common_offset," >> "$TEMP_FILE"
    else
        echo "    $most_common_offset," >> "$TEMP_FILE"
    fi

    unset offset_counts
done

# Close the array
cat >> "$TEMP_FILE" << 'EOF'
};

/// Get timezone offset in minutes for a given longitude
/// longitude: -180 to 180
/// Returns: offset in minutes from UTC
pub fn getTimezoneOffset(longitude: f32) i16 {
    // Normalize to 0-359
    const normalized = @mod(@as(i32, @intFromFloat(@round(longitude))) + 180, 360);
    return timezone_offsets[@intCast(normalized)];
}

test "timezone offset lookup" {
    // London (0°) should be close to UTC
    const london_offset = getTimezoneOffset(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(-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(139.0);
    try std.testing.expect(tokyo_offset >= 480 and tokyo_offset <= 600);
}
EOF

# Move to final location
mv "$TEMP_FILE" "$OUTPUT_FILE"

echo
echo "Generated $OUTPUT_FILE"
echo "Running zig fmt..."
zig fmt "$OUTPUT_FILE"
echo "Done!"