// This is a part of Chrono.
// See README.md and LICENSE.txt for details.

//! The internal implementation of the calendar and ordinal date.
//!
//! The current implementation is optimized for determining year, month, day and day of week.
//! 4-bit `YearFlags` map to one of 14 possible classes of year in the Gregorian calendar,
//! which are included in every packed `NaiveDate` instance.
//! The conversion between the packed calendar date (`Mdf`) and the ordinal date (`Of`) is
//! based on the moderately-sized lookup table (~1.5KB)
//! and the packed representation is chosen for the efficient lookup.
//! Every internal data structure does not validate its input,
//! but the conversion keeps the valid value valid and the invalid value invalid
//! so that the user-facing `NaiveDate` can validate the input as late as possible.

#![allow(dead_code)] // some internal methods have been left for consistency
#![cfg_attr(feature = "__internal_bench", allow(missing_docs))]

use core::{fmt, i32};
use div::{div_rem, mod_floor};
use num_traits::FromPrimitive;
use Weekday;

/// The internal date representation. This also includes the packed `Mdf` value.
pub type DateImpl = i32;

pub const MAX_YEAR: DateImpl = i32::MAX >> 13;
pub const MIN_YEAR: DateImpl = i32::MIN >> 13;

/// The year flags (aka the dominical letter).
///
/// There are 14 possible classes of year in the Gregorian calendar:
/// common and leap years starting with Monday through Sunday.
/// The `YearFlags` stores this information into 4 bits `abbb`,
/// where `a` is `1` for the common year (simplifies the `Of` validation)
/// and `bbb` is a non-zero `Weekday` (mapping `Mon` to 7) of the last day in the past year
/// (simplifies the day of week calculation from the 1-based ordinal).
#[derive(PartialEq, Eq, Copy, Clone)]
pub struct YearFlags(pub u8);

pub const A: YearFlags = YearFlags(0o15);
pub const AG: YearFlags = YearFlags(0o05);
pub const B: YearFlags = YearFlags(0o14);
pub const BA: YearFlags = YearFlags(0o04);
pub const C: YearFlags = YearFlags(0o13);
pub const CB: YearFlags = YearFlags(0o03);
pub const D: YearFlags = YearFlags(0o12);
pub const DC: YearFlags = YearFlags(0o02);
pub const E: YearFlags = YearFlags(0o11);
pub const ED: YearFlags = YearFlags(0o01);
pub const F: YearFlags = YearFlags(0o17);
pub const FE: YearFlags = YearFlags(0o07);
pub const G: YearFlags = YearFlags(0o16);
pub const GF: YearFlags = YearFlags(0o06);

static YEAR_TO_FLAGS: [YearFlags; 400] = [
    BA, G, F, E, DC, B, A, G, FE, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA,
    G, F, E, DC, B, A, G, FE, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G,
    F, E, DC, B, A, G, FE, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F,
    E, DC, B, A, G, FE, D, C, B, AG, F, E, D, // 100
    C, B, A, G, FE, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC,
    B, A, G, FE, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B,
    A, G, FE, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A,
    G, FE, D, C, B, AG, F, E, D, CB, A, G, F, // 200
    E, D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A, G, FE,
    D, C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A, G, FE, D,
    C, B, AG, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A, G, FE, D, C,
    B, AG, F, E, D, CB, A, G, F, ED, C, B, A, // 300
    G, F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A, G, FE, D, C, B, AG,
    F, E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A, G, FE, D, C, B, AG, F,
    E, D, CB, A, G, F, ED, C, B, A, GF, E, D, C, BA, G, F, E, DC, B, A, G, FE, D, C, B, AG, F, E,
    D, CB, A, G, F, ED, C, B, A, GF, E, D, C, // 400
];

static YEAR_DELTAS: [u8; 401] = [
    0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8,
    8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14,
    15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 20,
    21, 21, 21, 21, 22, 22, 22, 22, 23, 23, 23, 23, 24, 24, 24, 24, 25, 25, 25, // 100
    25, 25, 25, 25, 25, 26, 26, 26, 26, 27, 27, 27, 27, 28, 28, 28, 28, 29, 29, 29, 29, 30, 30, 30,
    30, 31, 31, 31, 31, 32, 32, 32, 32, 33, 33, 33, 33, 34, 34, 34, 34, 35, 35, 35, 35, 36, 36, 36,
    36, 37, 37, 37, 37, 38, 38, 38, 38, 39, 39, 39, 39, 40, 40, 40, 40, 41, 41, 41, 41, 42, 42, 42,
    42, 43, 43, 43, 43, 44, 44, 44, 44, 45, 45, 45, 45, 46, 46, 46, 46, 47, 47, 47, 47, 48, 48, 48,
    48, 49, 49, 49, // 200
    49, 49, 49, 49, 49, 50, 50, 50, 50, 51, 51, 51, 51, 52, 52, 52, 52, 53, 53, 53, 53, 54, 54, 54,
    54, 55, 55, 55, 55, 56, 56, 56, 56, 57, 57, 57, 57, 58, 58, 58, 58, 59, 59, 59, 59, 60, 60, 60,
    60, 61, 61, 61, 61, 62, 62, 62, 62, 63, 63, 63, 63, 64, 64, 64, 64, 65, 65, 65, 65, 66, 66, 66,
    66, 67, 67, 67, 67, 68, 68, 68, 68, 69, 69, 69, 69, 70, 70, 70, 70, 71, 71, 71, 71, 72, 72, 72,
    72, 73, 73, 73, // 300
    73, 73, 73, 73, 73, 74, 74, 74, 74, 75, 75, 75, 75, 76, 76, 76, 76, 77, 77, 77, 77, 78, 78, 78,
    78, 79, 79, 79, 79, 80, 80, 80, 80, 81, 81, 81, 81, 82, 82, 82, 82, 83, 83, 83, 83, 84, 84, 84,
    84, 85, 85, 85, 85, 86, 86, 86, 86, 87, 87, 87, 87, 88, 88, 88, 88, 89, 89, 89, 89, 90, 90, 90,
    90, 91, 91, 91, 91, 92, 92, 92, 92, 93, 93, 93, 93, 94, 94, 94, 94, 95, 95, 95, 95, 96, 96, 96,
    96, 97, 97, 97, 97, // 400+1
];

pub fn cycle_to_yo(cycle: u32) -> (u32, u32) {
    let (mut year_mod_400, mut ordinal0) = div_rem(cycle, 365);
    let delta = u32::from(YEAR_DELTAS[year_mod_400 as usize]);
    if ordinal0 < delta {
        year_mod_400 -= 1;
        ordinal0 += 365 - u32::from(YEAR_DELTAS[year_mod_400 as usize]);
    } else {
        ordinal0 -= delta;
    }
    (year_mod_400, ordinal0 + 1)
}

pub fn yo_to_cycle(year_mod_400: u32, ordinal: u32) -> u32 {
    year_mod_400 * 365 + u32::from(YEAR_DELTAS[year_mod_400 as usize]) + ordinal - 1
}

impl YearFlags {
    #[inline]
    pub fn from_year(year: i32) -> YearFlags {
        let year = mod_floor(year, 400);
        YearFlags::from_year_mod_400(year)
    }

    #[inline]
    pub fn from_year_mod_400(year: i32) -> YearFlags {
        YEAR_TO_FLAGS[year as usize]
    }

    #[inline]
    pub fn ndays(&self) -> u32 {
        let YearFlags(flags) = *self;
        366 - u32::from(flags >> 3)
    }

    #[inline]
    pub fn isoweek_delta(&self) -> u32 {
        let YearFlags(flags) = *self;
        let mut delta = u32::from(flags) & 0b0111;
        if delta < 3 {
            delta += 7;
        }
        delta
    }

    #[inline]
    pub fn nisoweeks(&self) -> u32 {
        let YearFlags(flags) = *self;
        52 + ((0b0000_0100_0000_0110 >> flags as usize) & 1)
    }
}

impl fmt::Debug for YearFlags {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let YearFlags(flags) = *self;
        match flags {
            0o15 => "A".fmt(f),
            0o05 => "AG".fmt(f),
            0o14 => "B".fmt(f),
            0o04 => "BA".fmt(f),
            0o13 => "C".fmt(f),
            0o03 => "CB".fmt(f),
            0o12 => "D".fmt(f),
            0o02 => "DC".fmt(f),
            0o11 => "E".fmt(f),
            0o01 => "ED".fmt(f),
            0o10 => "F?".fmt(f),
            0o00 => "FE?".fmt(f), // non-canonical
            0o17 => "F".fmt(f),
            0o07 => "FE".fmt(f),
            0o16 => "G".fmt(f),
            0o06 => "GF".fmt(f),
            _ => write!(f, "YearFlags({})", flags),
        }
    }
}

pub const MIN_OL: u32 = 1 << 1;
pub const MAX_OL: u32 = 366 << 1; // larger than the non-leap last day `(365 << 1) | 1`
pub const MIN_MDL: u32 = (1 << 6) | (1 << 1);
pub const MAX_MDL: u32 = (12 << 6) | (31 << 1) | 1;

const XX: i8 = -128;
static MDL_TO_OL: [i8; MAX_MDL as usize + 1] = [
    XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
    XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
    XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, // 0
    XX, XX, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, // 1
    XX, XX, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
    66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
    66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, XX, XX, XX, XX, XX, // 2
    XX, XX, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74,
    72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74,
    72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, // 3
    XX, XX, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76,
    74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76,
    74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, XX, XX, // 4
    XX, XX, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80,
    78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80,
    78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, // 5
    XX, XX, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82,
    80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82,
    80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, XX, XX, // 6
    XX, XX, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86,
    84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86,
    84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, // 7
    XX, XX, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88,
    86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88,
    86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, // 8
    XX, XX, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90,
    88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90,
    88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, XX, XX, // 9
    XX, XX, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94,
    92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94,
    92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, // 10
    XX, XX, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96,
    94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96,
    94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, XX, XX, // 11
    XX, XX, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98,
    100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100,
    98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98,
    100, // 12
];

static OL_TO_MDL: [u8; MAX_OL as usize + 1] = [
    0, 0, // 0
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
    64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, // 1
    66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
    66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
    66, 66, 66, 66, 66, 66, 66, 66, 66, // 2
    74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72,
    74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72,
    74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, 74, 72, // 3
    76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74,
    76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74,
    76, 74, 76, 74, 76, 74, 76, 74, 76, 74, 76, 74, // 4
    80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78,
    80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78,
    80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, 80, 78, // 5
    82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80,
    82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80,
    82, 80, 82, 80, 82, 80, 82, 80, 82, 80, 82, 80, // 6
    86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84,
    86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84,
    86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, 86, 84, // 7
    88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86,
    88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86,
    88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, 88, 86, // 8
    90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88,
    90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88,
    90, 88, 90, 88, 90, 88, 90, 88, 90, 88, 90, 88, // 9
    94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92,
    94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92,
    94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, 94, 92, // 10
    96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94,
    96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94,
    96, 94, 96, 94, 96, 94, 96, 94, 96, 94, 96, 94, // 11
    100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100,
    98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98,
    100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100, 98, 100,
    98, // 12
];

/// Ordinal (day of year) and year flags: `(ordinal << 4) | flags`.
///
/// The whole bits except for the least 3 bits are referred as `Ol` (ordinal and leap flag),
/// which is an index to the `OL_TO_MDL` lookup table.
#[derive(PartialEq, PartialOrd, Copy, Clone)]
pub struct Of(pub u32);

impl Of {
    #[inline]
    fn clamp_ordinal(ordinal: u32) -> u32 {
        if ordinal > 366 {
            0
        } else {
            ordinal
        }
    }

    #[inline]
    pub fn new(ordinal: u32, YearFlags(flags): YearFlags) -> Of {
        let ordinal = Of::clamp_ordinal(ordinal);
        Of((ordinal << 4) | u32::from(flags))
    }

    #[inline]
    pub fn from_mdf(Mdf(mdf): Mdf) -> Of {
        let mdl = mdf >> 3;
        match MDL_TO_OL.get(mdl as usize) {
            Some(&v) => Of(mdf.wrapping_sub((i32::from(v) as u32 & 0x3ff) << 3)),
            None => Of(0),
        }
    }

    #[inline]
    pub fn valid(&self) -> bool {
        let Of(of) = *self;
        let ol = of >> 3;
        MIN_OL <= ol && ol <= MAX_OL
    }

    #[inline]
    pub fn ordinal(&self) -> u32 {
        let Of(of) = *self;
        of >> 4
    }

    #[inline]
    pub fn with_ordinal(&self, ordinal: u32) -> Of {
        let ordinal = Of::clamp_ordinal(ordinal);
        let Of(of) = *self;
        Of((of & 0b1111) | (ordinal << 4))
    }

    #[inline]
    pub fn flags(&self) -> YearFlags {
        let Of(of) = *self;
        YearFlags((of & 0b1111) as u8)
    }

    #[inline]
    pub fn with_flags(&self, YearFlags(flags): YearFlags) -> Of {
        let Of(of) = *self;
        Of((of & !0b1111) | u32::from(flags))
    }

    #[inline]
    pub fn weekday(&self) -> Weekday {
        let Of(of) = *self;
        Weekday::from_u32(((of >> 4) + (of & 0b111)) % 7).unwrap()
    }

    #[inline]
    pub fn isoweekdate_raw(&self) -> (u32, Weekday) {
        // week ordinal = ordinal + delta
        let Of(of) = *self;
        let weekord = (of >> 4).wrapping_add(self.flags().isoweek_delta());
        (weekord / 7, Weekday::from_u32(weekord % 7).unwrap())
    }

    #[inline]
    pub fn to_mdf(&self) -> Mdf {
        Mdf::from_of(*self)
    }

    #[inline]
    pub fn succ(&self) -> Of {
        let Of(of) = *self;
        Of(of + (1 << 4))
    }

    #[inline]
    pub fn pred(&self) -> Of {
        let Of(of) = *self;
        Of(of - (1 << 4))
    }
}

impl fmt::Debug for Of {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let Of(of) = *self;
        write!(
            f,
            "Of(({} << 4) | {:#04o} /*{:?}*/)",
            of >> 4,
            of & 0b1111,
            YearFlags((of & 0b1111) as u8)
        )
    }
}

/// Month, day of month and year flags: `(month << 9) | (day << 4) | flags`
///
/// The whole bits except for the least 3 bits are referred as `Mdl`
/// (month, day of month and leap flag),
/// which is an index to the `MDL_TO_OL` lookup table.
#[derive(PartialEq, PartialOrd, Copy, Clone)]
pub struct Mdf(pub u32);

impl Mdf {
    #[inline]
    fn clamp_month(month: u32) -> u32 {
        if month > 12 {
            0
        } else {
            month
        }
    }

    #[inline]
    fn clamp_day(day: u32) -> u32 {
        if day > 31 {
            0
        } else {
            day
        }
    }

    #[inline]
    pub fn new(month: u32, day: u32, YearFlags(flags): YearFlags) -> Mdf {
        let month = Mdf::clamp_month(month);
        let day = Mdf::clamp_day(day);
        Mdf((month << 9) | (day << 4) | u32::from(flags))
    }

    #[inline]
    pub fn from_of(Of(of): Of) -> Mdf {
        let ol = of >> 3;
        match OL_TO_MDL.get(ol as usize) {
            Some(&v) => Mdf(of + (u32::from(v) << 3)),
            None => Mdf(0),
        }
    }

    #[inline]
    pub fn valid(&self) -> bool {
        let Mdf(mdf) = *self;
        let mdl = mdf >> 3;
        match MDL_TO_OL.get(mdl as usize) {
            Some(&v) => v >= 0,
            None => false,
        }
    }

    #[inline]
    pub fn month(&self) -> u32 {
        let Mdf(mdf) = *self;
        mdf >> 9
    }

    #[inline]
    pub fn with_month(&self, month: u32) -> Mdf {
        let month = Mdf::clamp_month(month);
        let Mdf(mdf) = *self;
        Mdf((mdf & 0b1_1111_1111) | (month << 9))
    }

    #[inline]
    pub fn day(&self) -> u32 {
        let Mdf(mdf) = *self;
        (mdf >> 4) & 0b1_1111
    }

    #[inline]
    pub fn with_day(&self, day: u32) -> Mdf {
        let day = Mdf::clamp_day(day);
        let Mdf(mdf) = *self;
        Mdf((mdf & !0b1_1111_0000) | (day << 4))
    }

    #[inline]
    pub fn flags(&self) -> YearFlags {
        let Mdf(mdf) = *self;
        YearFlags((mdf & 0b1111) as u8)
    }

    #[inline]
    pub fn with_flags(&self, YearFlags(flags): YearFlags) -> Mdf {
        let Mdf(mdf) = *self;
        Mdf((mdf & !0b1111) | u32::from(flags))
    }

    #[inline]
    pub fn to_of(&self) -> Of {
        Of::from_mdf(*self)
    }
}

impl fmt::Debug for Mdf {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let Mdf(mdf) = *self;
        write!(
            f,
            "Mdf(({} << 9) | ({} << 4) | {:#04o} /*{:?}*/)",
            mdf >> 9,
            (mdf >> 4) & 0b1_1111,
            mdf & 0b1111,
            YearFlags((mdf & 0b1111) as u8)
        )
    }
}

#[cfg(test)]
mod tests {
    #[cfg(test)]
    extern crate num_iter;

    use self::num_iter::range_inclusive;
    use super::{Mdf, Of};
    use super::{YearFlags, A, AG, B, BA, C, CB, D, DC, E, ED, F, FE, G, GF};
    use std::u32;
    use Weekday;

    const NONLEAP_FLAGS: [YearFlags; 7] = [A, B, C, D, E, F, G];
    const LEAP_FLAGS: [YearFlags; 7] = [AG, BA, CB, DC, ED, FE, GF];
    const FLAGS: [YearFlags; 14] = [A, B, C, D, E, F, G, AG, BA, CB, DC, ED, FE, GF];

    #[test]
    fn test_year_flags_ndays_from_year() {
        assert_eq!(YearFlags::from_year(2014).ndays(), 365);
        assert_eq!(YearFlags::from_year(2012).ndays(), 366);
        assert_eq!(YearFlags::from_year(2000).ndays(), 366);
        assert_eq!(YearFlags::from_year(1900).ndays(), 365);
        assert_eq!(YearFlags::from_year(1600).ndays(), 366);
        assert_eq!(YearFlags::from_year(1).ndays(), 365);
        assert_eq!(YearFlags::from_year(0).ndays(), 366); // 1 BCE (proleptic Gregorian)
        assert_eq!(YearFlags::from_year(-1).ndays(), 365); // 2 BCE
        assert_eq!(YearFlags::from_year(-4).ndays(), 366); // 5 BCE
        assert_eq!(YearFlags::from_year(-99).ndays(), 365); // 100 BCE
        assert_eq!(YearFlags::from_year(-100).ndays(), 365); // 101 BCE
        assert_eq!(YearFlags::from_year(-399).ndays(), 365); // 400 BCE
        assert_eq!(YearFlags::from_year(-400).ndays(), 366); // 401 BCE
    }

    #[test]
    fn test_year_flags_nisoweeks() {
        assert_eq!(A.nisoweeks(), 52);
        assert_eq!(B.nisoweeks(), 52);
        assert_eq!(C.nisoweeks(), 52);
        assert_eq!(D.nisoweeks(), 53);
        assert_eq!(E.nisoweeks(), 52);
        assert_eq!(F.nisoweeks(), 52);
        assert_eq!(G.nisoweeks(), 52);
        assert_eq!(AG.nisoweeks(), 52);
        assert_eq!(BA.nisoweeks(), 52);
        assert_eq!(CB.nisoweeks(), 52);
        assert_eq!(DC.nisoweeks(), 53);
        assert_eq!(ED.nisoweeks(), 53);
        assert_eq!(FE.nisoweeks(), 52);
        assert_eq!(GF.nisoweeks(), 52);
    }

    #[test]
    fn test_of() {
        fn check(expected: bool, flags: YearFlags, ordinal1: u32, ordinal2: u32) {
            for ordinal in range_inclusive(ordinal1, ordinal2) {
                let of = Of::new(ordinal, flags);
                assert!(
                    of.valid() == expected,
                    "ordinal {} = {:?} should be {} for dominical year {:?}",
                    ordinal,
                    of,
                    if expected { "valid" } else { "invalid" },
                    flags
                );
            }
        }

        for &flags in NONLEAP_FLAGS.iter() {
            check(false, flags, 0, 0);
            check(true, flags, 1, 365);
            check(false, flags, 366, 1024);
            check(false, flags, u32::MAX, u32::MAX);
        }

        for &flags in LEAP_FLAGS.iter() {
            check(false, flags, 0, 0);
            check(true, flags, 1, 366);
            check(false, flags, 367, 1024);
            check(false, flags, u32::MAX, u32::MAX);
        }
    }

    #[test]
    fn test_mdf_valid() {
        fn check(expected: bool, flags: YearFlags, month1: u32, day1: u32, month2: u32, day2: u32) {
            for month in range_inclusive(month1, month2) {
                for day in range_inclusive(day1, day2) {
                    let mdf = Mdf::new(month, day, flags);
                    assert!(
                        mdf.valid() == expected,
                        "month {} day {} = {:?} should be {} for dominical year {:?}",
                        month,
                        day,
                        mdf,
                        if expected { "valid" } else { "invalid" },
                        flags
                    );
                }
            }
        }

        for &flags in NONLEAP_FLAGS.iter() {
            check(false, flags, 0, 0, 0, 1024);
            check(false, flags, 0, 0, 16, 0);
            check(true, flags, 1, 1, 1, 31);
            check(false, flags, 1, 32, 1, 1024);
            check(true, flags, 2, 1, 2, 28);
            check(false, flags, 2, 29, 2, 1024);
            check(true, flags, 3, 1, 3, 31);
            check(false, flags, 3, 32, 3, 1024);
            check(true, flags, 4, 1, 4, 30);
            check(false, flags, 4, 31, 4, 1024);
            check(true, flags, 5, 1, 5, 31);
            check(false, flags, 5, 32, 5, 1024);
            check(true, flags, 6, 1, 6, 30);
            check(false, flags, 6, 31, 6, 1024);
            check(true, flags, 7, 1, 7, 31);
            check(false, flags, 7, 32, 7, 1024);
            check(true, flags, 8, 1, 8, 31);
            check(false, flags, 8, 32, 8, 1024);
            check(true, flags, 9, 1, 9, 30);
            check(false, flags, 9, 31, 9, 1024);
            check(true, flags, 10, 1, 10, 31);
            check(false, flags, 10, 32, 10, 1024);
            check(true, flags, 11, 1, 11, 30);
            check(false, flags, 11, 31, 11, 1024);
            check(true, flags, 12, 1, 12, 31);
            check(false, flags, 12, 32, 12, 1024);
            check(false, flags, 13, 0, 16, 1024);
            check(false, flags, u32::MAX, 0, u32::MAX, 1024);
            check(false, flags, 0, u32::MAX, 16, u32::MAX);
            check(false, flags, u32::MAX, u32::MAX, u32::MAX, u32::MAX);
        }

        for &flags in LEAP_FLAGS.iter() {
            check(false, flags, 0, 0, 0, 1024);
            check(false, flags, 0, 0, 16, 0);
            check(true, flags, 1, 1, 1, 31);
            check(false, flags, 1, 32, 1, 1024);
            check(true, flags, 2, 1, 2, 29);
            check(false, flags, 2, 30, 2, 1024);
            check(true, flags, 3, 1, 3, 31);
            check(false, flags, 3, 32, 3, 1024);
            check(true, flags, 4, 1, 4, 30);
            check(false, flags, 4, 31, 4, 1024);
            check(true, flags, 5, 1, 5, 31);
            check(false, flags, 5, 32, 5, 1024);
            check(true, flags, 6, 1, 6, 30);
            check(false, flags, 6, 31, 6, 1024);
            check(true, flags, 7, 1, 7, 31);
            check(false, flags, 7, 32, 7, 1024);
            check(true, flags, 8, 1, 8, 31);
            check(false, flags, 8, 32, 8, 1024);
            check(true, flags, 9, 1, 9, 30);
            check(false, flags, 9, 31, 9, 1024);
            check(true, flags, 10, 1, 10, 31);
            check(false, flags, 10, 32, 10, 1024);
            check(true, flags, 11, 1, 11, 30);
            check(false, flags, 11, 31, 11, 1024);
            check(true, flags, 12, 1, 12, 31);
            check(false, flags, 12, 32, 12, 1024);
            check(false, flags, 13, 0, 16, 1024);
            check(false, flags, u32::MAX, 0, u32::MAX, 1024);
            check(false, flags, 0, u32::MAX, 16, u32::MAX);
            check(false, flags, u32::MAX, u32::MAX, u32::MAX, u32::MAX);
        }
    }

    #[test]
    fn test_of_fields() {
        for &flags in FLAGS.iter() {
            for ordinal in range_inclusive(1u32, 366) {
                let of = Of::new(ordinal, flags);
                if of.valid() {
                    assert_eq!(of.ordinal(), ordinal);
                }
            }
        }
    }

    #[test]
    fn test_of_with_fields() {
        fn check(flags: YearFlags, ordinal: u32) {
            let of = Of::new(ordinal, flags);

            for ordinal in range_inclusive(0u32, 1024) {
                let of = of.with_ordinal(ordinal);
                assert_eq!(of.valid(), Of::new(ordinal, flags).valid());
                if of.valid() {
                    assert_eq!(of.ordinal(), ordinal);
                }
            }
        }

        for &flags in NONLEAP_FLAGS.iter() {
            check(flags, 1);
            check(flags, 365);
        }
        for &flags in LEAP_FLAGS.iter() {
            check(flags, 1);
            check(flags, 366);
        }
    }

    #[test]
    fn test_of_weekday() {
        assert_eq!(Of::new(1, A).weekday(), Weekday::Sun);
        assert_eq!(Of::new(1, B).weekday(), Weekday::Sat);
        assert_eq!(Of::new(1, C).weekday(), Weekday::Fri);
        assert_eq!(Of::new(1, D).weekday(), Weekday::Thu);
        assert_eq!(Of::new(1, E).weekday(), Weekday::Wed);
        assert_eq!(Of::new(1, F).weekday(), Weekday::Tue);
        assert_eq!(Of::new(1, G).weekday(), Weekday::Mon);
        assert_eq!(Of::new(1, AG).weekday(), Weekday::Sun);
        assert_eq!(Of::new(1, BA).weekday(), Weekday::Sat);
        assert_eq!(Of::new(1, CB).weekday(), Weekday::Fri);
        assert_eq!(Of::new(1, DC).weekday(), Weekday::Thu);
        assert_eq!(Of::new(1, ED).weekday(), Weekday::Wed);
        assert_eq!(Of::new(1, FE).weekday(), Weekday::Tue);
        assert_eq!(Of::new(1, GF).weekday(), Weekday::Mon);

        for &flags in FLAGS.iter() {
            let mut prev = Of::new(1, flags).weekday();
            for ordinal in range_inclusive(2u32, flags.ndays()) {
                let of = Of::new(ordinal, flags);
                let expected = prev.succ();
                assert_eq!(of.weekday(), expected);
                prev = expected;
            }
        }
    }

    #[test]
    fn test_mdf_fields() {
        for &flags in FLAGS.iter() {
            for month in range_inclusive(1u32, 12) {
                for day in range_inclusive(1u32, 31) {
                    let mdf = Mdf::new(month, day, flags);
                    if mdf.valid() {
                        assert_eq!(mdf.month(), month);
                        assert_eq!(mdf.day(), day);
                    }
                }
            }
        }
    }

    #[test]
    fn test_mdf_with_fields() {
        fn check(flags: YearFlags, month: u32, day: u32) {
            let mdf = Mdf::new(month, day, flags);

            for month in range_inclusive(0u32, 16) {
                let mdf = mdf.with_month(month);
                assert_eq!(mdf.valid(), Mdf::new(month, day, flags).valid());
                if mdf.valid() {
                    assert_eq!(mdf.month(), month);
                    assert_eq!(mdf.day(), day);
                }
            }

            for day in range_inclusive(0u32, 1024) {
                let mdf = mdf.with_day(day);
                assert_eq!(mdf.valid(), Mdf::new(month, day, flags).valid());
                if mdf.valid() {
                    assert_eq!(mdf.month(), month);
                    assert_eq!(mdf.day(), day);
                }
            }
        }

        for &flags in NONLEAP_FLAGS.iter() {
            check(flags, 1, 1);
            check(flags, 1, 31);
            check(flags, 2, 1);
            check(flags, 2, 28);
            check(flags, 2, 29);
            check(flags, 12, 31);
        }
        for &flags in LEAP_FLAGS.iter() {
            check(flags, 1, 1);
            check(flags, 1, 31);
            check(flags, 2, 1);
            check(flags, 2, 29);
            check(flags, 2, 30);
            check(flags, 12, 31);
        }
    }

    #[test]
    fn test_of_isoweekdate_raw() {
        for &flags in FLAGS.iter() {
            // January 4 should be in the first week
            let (week, _) = Of::new(4 /* January 4 */, flags).isoweekdate_raw();
            assert_eq!(week, 1);
        }
    }

    #[test]
    fn test_of_to_mdf() {
        for i in range_inclusive(0u32, 8192) {
            let of = Of(i);
            assert_eq!(of.valid(), of.to_mdf().valid());
        }
    }

    #[test]
    fn test_mdf_to_of() {
        for i in range_inclusive(0u32, 8192) {
            let mdf = Mdf(i);
            assert_eq!(mdf.valid(), mdf.to_of().valid());
        }
    }

    #[test]
    fn test_of_to_mdf_to_of() {
        for i in range_inclusive(0u32, 8192) {
            let of = Of(i);
            if of.valid() {
                assert_eq!(of, of.to_mdf().to_of());
            }
        }
    }

    #[test]
    fn test_mdf_to_of_to_mdf() {
        for i in range_inclusive(0u32, 8192) {
            let mdf = Mdf(i);
            if mdf.valid() {
                assert_eq!(mdf, mdf.to_of().to_mdf());
            }
        }
    }
}