package math_bits

import "base:intrinsics"

U8_MIN  :: 0
U16_MIN :: 0
U32_MIN :: 0
U64_MIN :: 0

U8_MAX  :: 1 <<  8 - 1
U16_MAX :: 1 << 16 - 1
U32_MAX :: 1 << 32 - 1
U64_MAX :: 1 << 64 - 1

I8_MIN  :: - 1 << 7
I16_MIN :: - 1 << 15
I32_MIN :: - 1 << 31
I64_MIN :: - 1 << 63

I8_MAX  :: 1 <<  7 - 1
I16_MAX :: 1 << 15 - 1
I32_MAX :: 1 << 31 - 1
I64_MAX :: 1 << 63 - 1


count_ones           :: intrinsics.count_ones
count_zeros          :: intrinsics.count_zeros
trailing_zeros       :: intrinsics.count_trailing_zeros
leading_zeros        :: intrinsics.count_leading_zeros
count_trailing_zeros :: intrinsics.count_trailing_zeros
count_leading_zeros  :: intrinsics.count_leading_zeros
reverse_bits         :: intrinsics.reverse_bits
byte_swap            :: intrinsics.byte_swap

overflowing_add :: intrinsics.overflow_add
overflowing_sub :: intrinsics.overflow_sub
overflowing_mul :: intrinsics.overflow_mul


@(require_results)
log2 :: proc "contextless" (x: $T) -> T where intrinsics.type_is_integer(T), intrinsics.type_is_unsigned(T) {
	return (8*size_of(T)-1) - count_leading_zeros(x)
}

@(require_results)
rotate_left8 :: proc "contextless" (x: u8,  k: int) -> u8 {
	n :: 8
	s := uint(k) & (n-1)
	return x <<s | x>>(n-s)
}
@(require_results)
rotate_left16 :: proc "contextless" (x: u16, k: int) -> u16 {
	n :: 16
	s := uint(k) & (n-1)
	return x <<s | x>>(n-s)
}
@(require_results)
rotate_left32 :: proc "contextless" (x: u32, k: int) -> u32 {
	n :: 32
	s := uint(k) & (n-1)
	return x <<s | x>>(n-s)
}
@(require_results)
rotate_left64 :: proc "contextless" (x: u64, k: int) -> u64 {
	n :: 64
	s := uint(k) & (n-1)
	return x <<s | x>>(n-s)
}

@(require_results)
rotate_left :: proc "contextless" (x: uint, k: int) -> uint {
	n :: 8*size_of(uint)
	s := uint(k) & (n-1)
	return x <<s | x>>(n-s)
}

@(require_results)
from_be_u8   :: proc "contextless" (i:   u8) ->   u8 { return i }
@(require_results)
from_be_u16  :: proc "contextless" (i:  u16) ->  u16 { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }
@(require_results)
from_be_u32  :: proc "contextless" (i:  u32) ->  u32 { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }
@(require_results)
from_be_u64  :: proc "contextless" (i:  u64) ->  u64 { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }
@(require_results)
from_be_uint :: proc "contextless" (i: uint) -> uint { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }

@(require_results)
from_le_u8   :: proc "contextless" (i:   u8) ->   u8 { return i }
@(require_results)
from_le_u16  :: proc "contextless" (i:  u16) ->  u16 { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }
@(require_results)
from_le_u32  :: proc "contextless" (i:  u32) ->  u32 { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }
@(require_results)
from_le_u64  :: proc "contextless" (i:  u64) ->  u64 { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }
@(require_results)
from_le_uint :: proc "contextless" (i: uint) -> uint { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }

@(require_results)
to_be_u8   :: proc "contextless" (i:   u8) ->   u8 { return i }
@(require_results)
to_be_u16  :: proc "contextless" (i:  u16) ->  u16 { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }
@(require_results)
to_be_u32  :: proc "contextless" (i:  u32) ->  u32 { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }
@(require_results)
to_be_u64  :: proc "contextless" (i:  u64) ->  u64 { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }
@(require_results)
to_be_uint :: proc "contextless" (i: uint) -> uint { when ODIN_ENDIAN == .Big { return i } else { return byte_swap(i) } }


@(require_results)
to_le_u8   :: proc "contextless" (i:   u8) ->   u8 { return i }
@(require_results)
to_le_u16  :: proc "contextless" (i:  u16) ->  u16 { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }
@(require_results)
to_le_u32  :: proc "contextless" (i:  u32) ->  u32 { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }
@(require_results)
to_le_u64  :: proc "contextless" (i:  u64) ->  u64 { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }
@(require_results)
to_le_uint :: proc "contextless" (i: uint) -> uint { when ODIN_ENDIAN == .Little { return i } else { return byte_swap(i) } }



@(require_results)
len_u8 :: proc "contextless" (x: u8) -> int {
	return int(len_u8_table[x])
}
@(require_results)
len_u16 :: proc "contextless" (x: u16) -> (n: int) {
	x := x
	if x >= 1<<8 {
		x >>= 8
		n = 8
	}
	return n + int(len_u8_table[x])
}
@(require_results)
len_u32 :: proc "contextless" (x: u32) -> (n: int) {
	x := x
	if x >= 1<<16 {
		x >>= 16
		n = 16
	}
	if x >= 1<<8 {
		x >>= 8
		n += 8
	}
	return n + int(len_u8_table[x])
}
@(require_results)
len_u64 :: proc "contextless" (x: u64) -> (n: int) {
	x := x
	if x >= 1<<32 {
		x >>= 32
		n = 32
	}
	if x >= 1<<16 {
		x >>= 16
		n += 16
	}
	if x >= 1<<8 {
		x >>= 8
		n += 8
	}
	return n + int(len_u8_table[x])
}
@(require_results)
len_uint :: proc "contextless" (x: uint) -> (n: int) {
	when size_of(uint) == size_of(u64) {
		return len_u64(u64(x))
	} else {
		return len_u32(u32(x))
	}
}

// returns the minimum number of bits required to represent x
len :: proc{len_u8, len_u16, len_u32, len_u64, len_uint}


@(require_results)
add_u32 :: proc "contextless" (x, y, carry: u32) -> (sum, carry_out: u32) {
	tmp_carry, tmp_carry2: bool
	sum, tmp_carry = intrinsics.overflow_add(x, y)
	sum, tmp_carry2 = intrinsics.overflow_add(sum, carry)
	carry_out = u32(tmp_carry | tmp_carry2)
	return
}
@(require_results)
add_u64 :: proc "contextless" (x, y, carry: u64) -> (sum, carry_out: u64) {
	tmp_carry, tmp_carry2: bool
	sum, tmp_carry = intrinsics.overflow_add(x, y)
	sum, tmp_carry2 = intrinsics.overflow_add(sum, carry)
	carry_out = u64(tmp_carry | tmp_carry2)
	return
}
@(require_results)
add_uint :: proc "contextless" (x, y, carry: uint) -> (sum, carry_out: uint) {
	when size_of(uint) == size_of(u64) {
		a, b := add_u64(u64(x), u64(y), u64(carry))
	} else {
		#assert(size_of(uint) == size_of(u32))
		a, b := add_u32(u32(x), u32(y), u32(carry))
	}
	return uint(a), uint(b)
}
add :: proc{add_u32, add_u64, add_uint}


@(require_results)
sub_u32 :: proc "contextless" (x, y, borrow: u32) -> (diff, borrow_out: u32) {
	tmp_borrow, tmp_borrow2: bool
	diff, tmp_borrow = intrinsics.overflow_sub(x, y)
	diff, tmp_borrow2 = intrinsics.overflow_sub(diff, borrow)
	borrow_out = u32(tmp_borrow | tmp_borrow2)
	return
}
@(require_results)
sub_u64 :: proc "contextless" (x, y, borrow: u64) -> (diff, borrow_out: u64) {
	tmp_borrow, tmp_borrow2: bool
	diff, tmp_borrow = intrinsics.overflow_sub(x, y)
	diff, tmp_borrow2 = intrinsics.overflow_sub(diff, borrow)
	borrow_out = u64(tmp_borrow | tmp_borrow2)
	return
}
@(require_results)
sub_uint :: proc "contextless" (x, y, borrow: uint) -> (diff, borrow_out: uint) {
	when size_of(uint) == size_of(u64) {
		a, b := sub_u64(u64(x), u64(y), u64(borrow))
	} else {
		#assert(size_of(uint) == size_of(u32))
		a, b := sub_u32(u32(x), u32(y), u32(borrow))
	}
	return uint(a), uint(b)
}
sub :: proc{sub_u32, sub_u64, sub_uint}


@(require_results)
mul_u32 :: proc "contextless" (x, y: u32) -> (hi, lo: u32) {
	z := u64(x) * u64(y)
	hi, lo = u32(z>>32), u32(z)
	return
}
@(require_results)
mul_u64 :: proc "contextless" (x, y: u64) -> (hi, lo: u64) {
	prod_wide := u128(x) * u128(y)
	hi, lo = u64(prod_wide>>64), u64(prod_wide)
	return
}

@(require_results)
mul_uint :: proc "contextless" (x, y: uint) -> (hi, lo: uint) {
	when size_of(uint) == size_of(u32) {
		a, b := mul_u32(u32(x), u32(y))
	} else {
		#assert(size_of(uint) == size_of(u64))
		a, b := mul_u64(u64(x), u64(y))
	}
	return uint(a), uint(b)
}

mul :: proc{mul_u32, mul_u64, mul_uint}


@(require_results)
div_u32 :: proc "odin" (hi, lo, y: u32) -> (quo, rem: u32) {
	assert(y != 0 && y <= hi)
	z := u64(hi)<<32 | u64(lo)
	quo, rem = u32(z/u64(y)), u32(z%u64(y))
	return
}
@(require_results)
div_u64 :: proc "odin" (hi, lo, y: u64) -> (quo, rem: u64) {
	y := y
	two32  :: 1 << 32
	mask32 :: two32 - 1
	if y == 0 {
		panic("divide error")
	}
	if y <= hi {
		panic("overflow error")
	}

	s := uint(count_leading_zeros(y))
	y <<= s

	yn1 := y >> 32
	yn0 := y & mask32
	un32 := hi<<s | lo>>(64-s)
	un10 := lo << s
	un1 := un10 >> 32
	un0 := un10 & mask32
	q1 := un32 / yn1
	rhat := un32 - q1*yn1

	for q1 >= two32 || q1*yn0 > two32*rhat+un1 {
		q1 -= 1
		rhat += yn1
		if rhat >= two32 {
			break
		}
	}

	un21 := un32*two32 + un1 - q1*y
	q0 := un21 / yn1
	rhat = un21 - q0*yn1

	for q0 >= two32 || q0*yn0 > two32*rhat+un0 {
		q0 -= 1
		rhat += yn1
		if rhat >= two32 {
			break
		}
	}

	return q1*two32 + q0, (un21*two32 + un0 - q0*y) >> s
}
@(require_results)
div_uint :: proc "odin" (hi, lo, y: uint) -> (quo, rem: uint) {
	when size_of(uint) == size_of(u32) {
		a, b := div_u32(u32(hi), u32(lo), u32(y))
	} else {
		#assert(size_of(uint) == size_of(u64))
		a, b := div_u64(u64(hi), u64(lo), u64(y))
	}
	return uint(a), uint(b)
}
div :: proc{div_u32, div_u64, div_uint}



@(require_results)
is_power_of_two_u8   :: proc "contextless" (i:   u8) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_i8   :: proc "contextless" (i:   i8) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_u16  :: proc "contextless" (i:  u16) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_i16  :: proc "contextless" (i:  i16) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_u32  :: proc "contextless" (i:  u32) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_i32  :: proc "contextless" (i:  i32) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_u64  :: proc "contextless" (i:  u64) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_i64  :: proc "contextless" (i:  i64) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_uint :: proc "contextless" (i: uint) -> bool { return i > 0 && (i & (i-1)) == 0 }
@(require_results)
is_power_of_two_int  :: proc "contextless" (i:  int) -> bool { return i > 0 && (i & (i-1)) == 0 }

is_power_of_two :: proc{
	is_power_of_two_u8,   is_power_of_two_i8,
	is_power_of_two_u16,  is_power_of_two_i16,
	is_power_of_two_u32,  is_power_of_two_i32,
	is_power_of_two_u64,  is_power_of_two_i64,
	is_power_of_two_uint, is_power_of_two_int,
}


@private
len_u8_table := [256]u8{
	0         = 0,
	1         = 1,
	2..<4     = 2,
	4..<8     = 3,
	8..<16    = 4,
	16..<32   = 5,
	32..<64   = 6,
	64..<128  = 7,
	128..<256 = 8,
}


@(require_results)
bitfield_extract_u8   :: proc "contextless" (value:   u8, offset, bits: uint) ->   u8 { return (value >> offset) &   u8(1<<bits - 1) }
@(require_results)
bitfield_extract_u16  :: proc "contextless" (value:  u16, offset, bits: uint) ->  u16 { return (value >> offset) &  u16(1<<bits - 1) }
@(require_results)
bitfield_extract_u32  :: proc "contextless" (value:  u32, offset, bits: uint) ->  u32 { return (value >> offset) &  u32(1<<bits - 1) }
@(require_results)
bitfield_extract_u64  :: proc "contextless" (value:  u64, offset, bits: uint) ->  u64 { return (value >> offset) &  u64(1<<bits - 1) }
@(require_results)
bitfield_extract_u128 :: proc "contextless" (value: u128, offset, bits: uint) -> u128 { return (value >> offset) & u128(1<<bits - 1) }
@(require_results)
bitfield_extract_uint :: proc "contextless" (value: uint, offset, bits: uint) -> uint { return (value >> offset) & uint(1<<bits - 1) }

@(require_results)
bitfield_extract_i8 :: proc "contextless" (value: i8, offset, bits: uint) -> i8 {
	v := (u8(value) >> offset) & u8(1<<bits - 1)
	m := u8(1<<(bits-1))
	r := (v~m) - m
	return i8(r)
}
@(require_results)
bitfield_extract_i16 :: proc "contextless" (value: i16, offset, bits: uint) -> i16 {
	v := (u16(value) >> offset) & u16(1<<bits - 1)
	m := u16(1<<(bits-1))
	r := (v~m) - m
	return i16(r)
}
@(require_results)
bitfield_extract_i32 :: proc "contextless" (value: i32, offset, bits: uint) -> i32 {
	v := (u32(value) >> offset) & u32(1<<bits - 1)
	m := u32(1<<(bits-1))
	r := (v~m) - m
	return i32(r)
}
@(require_results)
bitfield_extract_i64 :: proc "contextless" (value: i64, offset, bits: uint) -> i64 {
	v := (u64(value) >> offset) & u64(1<<bits - 1)
	m := u64(1<<(bits-1))
	r := (v~m) - m
	return i64(r)
}
@(require_results)
bitfield_extract_i128 :: proc "contextless" (value: i128, offset, bits: uint) -> i128 {
	v := (u128(value) >> offset) & u128(1<<bits - 1)
	m := u128(1<<(bits-1))
	r := (v~m) - m
	return i128(r)
}
@(require_results)
bitfield_extract_int :: proc "contextless" (value: int, offset, bits: uint) -> int {
	v := (uint(value) >> offset) & uint(1<<bits - 1)
	m := uint(1<<(bits-1))
	r := (v~m) - m
	return int(r)
}


bitfield_extract :: proc{
	bitfield_extract_u8,
	bitfield_extract_u16,
	bitfield_extract_u32,
	bitfield_extract_u64,
	bitfield_extract_u128,
	bitfield_extract_uint,
	bitfield_extract_i8,
	bitfield_extract_i16,
	bitfield_extract_i32,
	bitfield_extract_i64,
	bitfield_extract_i128,
	bitfield_extract_int,
}


@(require_results)
bitfield_insert_u8 :: proc "contextless" (base, insert: u8, offset, bits: uint) -> u8 {
	mask := u8(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_u16 :: proc "contextless" (base, insert: u16, offset, bits: uint) -> u16 {
	mask := u16(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_u32 :: proc "contextless" (base, insert: u32, offset, bits: uint) -> u32 {
	mask := u32(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_u64 :: proc "contextless" (base, insert: u64, offset, bits: uint) -> u64 {
	mask := u64(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_u128 :: proc "contextless" (base, insert: u128, offset, bits: uint) -> u128 {
	mask := u128(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_uint :: proc "contextless" (base, insert: uint, offset, bits: uint) -> uint {
	mask := uint(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}

@(require_results)
bitfield_insert_i8 :: proc "contextless" (base, insert: i8, offset, bits: uint) -> i8 {
	mask := i8(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_i16 :: proc "contextless" (base, insert: i16, offset, bits: uint) -> i16 {
	mask := i16(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_i32 :: proc "contextless" (base, insert: i32, offset, bits: uint) -> i32 {
	mask := i32(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_i64 :: proc "contextless" (base, insert: i64, offset, bits: uint) -> i64 {
	mask := i64(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_i128 :: proc "contextless" (base, insert: i128, offset, bits: uint) -> i128 {
	mask := i128(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}
@(require_results)
bitfield_insert_int :: proc "contextless" (base, insert: int, offset, bits: uint) -> int {
	mask := int(1<<bits - 1)
	return (base &~ (mask<<offset)) | ((insert&mask) << offset)
}

bitfield_insert :: proc{
	bitfield_insert_u8,
	bitfield_insert_u16,
	bitfield_insert_u32,
	bitfield_insert_u64,
	bitfield_insert_u128,
	bitfield_insert_uint,
	bitfield_insert_i8,
	bitfield_insert_i16,
	bitfield_insert_i32,
	bitfield_insert_i64,
	bitfield_insert_i128,
	bitfield_insert_int,
}