const std = @import("std");

const c = @cImport({
    @cInclude("time.h");
    @cInclude("astro.h");
});

pub const Phase = struct {
    phase: f64, // 0.0 to 1.0 (0=new, 0.25=first quarter, 0.5=full, 0.75=last quarter)
    illuminated: f64, // 0.0 to 1.0
    age_days: f64, // Age in days
    distance_km: f64,
    angular_diameter: f64,

    pub fn emoji(self: Phase) []const u8 {
        const p = self.phase;
        if (p < 0.0625) return "🌑"; // New moon
        if (p < 0.1875) return "🌒"; // Waxing crescent
        if (p < 0.3125) return "🌓"; // First quarter
        if (p < 0.4375) return "🌔"; // Waxing gibbous
        if (p < 0.5625) return "🌕"; // Full moon
        if (p < 0.6875) return "🌖"; // Waning gibbous
        if (p < 0.8125) return "🌗"; // Last quarter
        if (p < 0.9375) return "🌘"; // Waning crescent
        return "🌑"; // New moon
    }

    pub fn day(self: Phase) u8 {
        return @intFromFloat(@round(self.age_days));
    }
};

pub fn getPhase(timestamp: i64) Phase {
    const julian = c.unix_to_julian(@intCast(timestamp));

    var illuminated: f64 = 0;
    var age_days: f64 = 0;
    var distance: f64 = 0;
    var angular_diameter: f64 = 0;
    var sun_distance: f64 = 0;
    var sun_angular_diameter: f64 = 0;

    const phase_angle = c.phase(
        julian,
        &illuminated,
        &age_days,
        &distance,
        &angular_diameter,
        &sun_distance,
        &sun_angular_diameter,
    );

    return .{
        .phase = phase_angle,
        .illuminated = illuminated,
        .age_days = age_days,
        .distance_km = distance,
        .angular_diameter = angular_diameter,
    };
}

test "moon phase calculation" {
    // Test a known date: 2024-01-01 00:00:00 UTC
    const timestamp: i64 = 1704067200;
    const moon = getPhase(timestamp);

    try std.testing.expect(moon.phase >= 0.0 and moon.phase <= 1.0);
    try std.testing.expect(moon.illuminated >= 0.0 and moon.illuminated <= 1.0);
    try std.testing.expect(moon.age_days >= 0.0 and moon.age_days <= 29.53);
    try std.testing.expect(moon.distance_km > 0);
}