// Package guts provides a low-level interface to the BLAKE3 cryptographic hash
// function.
package guts

import (
	
	
)

// Various constants.
const (
	FlagChunkStart = 1 << iota
	FlagChunkEnd
	FlagParent
	FlagRoot
	FlagKeyedHash
	FlagDeriveKeyContext
	FlagDeriveKeyMaterial

	BlockSize = 64
	ChunkSize = 1024

	MaxSIMD = 16 // AVX-512 vectors can store 16 words
)

// IV is the BLAKE3 initialization vector.
var IV = [8]uint32{
	0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A,
	0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19,
}

// A Node represents a chunk or parent in the BLAKE3 Merkle tree.
type Node struct {
	CV       [8]uint32 // chaining value from previous node
	Block    [16]uint32
	Counter  uint64
	BlockLen uint32
	Flags    uint32
}

// ParentNode returns a Node that incorporates the chaining values of two child
// nodes.
func (,  [8]uint32,  *[8]uint32,  uint32) Node {
	 := Node{
		CV:       *,
		Counter:  0,         // counter is reset for parents
		BlockLen: BlockSize, // block is full
		Flags:     | FlagParent,
	}
	copy(.Block[:8], [:])
	copy(.Block[8:], [:])
	return 
}

// Eigentrees returns the sequence of eigentree heights that increment counter
// to counter+chunks.
func ( uint64,  uint64) ( []int) {
	for  := ;  < +; {
		 := min(bits.TrailingZeros64(), bits.Len64(+-)-1)
		 = append(, )
		 += 1 << 
	}
	return
}

// CompressEigentree compresses a buffer of 2^n chunks in parallel, returning
// their root node.
func ( []byte,  *[8]uint32,  uint64,  uint32) Node {
	if  := uint64(len() / ChunkSize); bits.OnesCount64() != 1 {
		panic("non-power-of-two eigentree size")
	} else if  == 1 {
		return CompressChunk(, , , )
	} else if  <= MaxSIMD {
		 := len()
		if cap() < MaxSIMD*ChunkSize {
			 = append(, make([]byte, MaxSIMD*ChunkSize-len())...)
		}
		return CompressBuffer((*[MaxSIMD * ChunkSize]byte)([:MaxSIMD*ChunkSize]), , , , )
	} else {
		 := make([][8]uint32, /MaxSIMD)
		var  sync.WaitGroup
		for  := range  {
			.Add(1)
			go func( uint64) {
				defer .Done()
				[] = ChainingValue(CompressBuffer((*[MaxSIMD * ChunkSize]byte)([*MaxSIMD*ChunkSize:]), MaxSIMD*ChunkSize, , +(MaxSIMD*), ))
			}(uint64())
		}
		.Wait()

		var  func( [][8]uint32) Node
		 = func( [][8]uint32) Node {
			if len() == 2 {
				return ParentNode([0], [1], , )
			} else if len() == MaxSIMD {
				return mergeSubtrees((*[MaxSIMD][8]uint32)(), MaxSIMD, , )
			}
			return ParentNode(ChainingValue(([:len()/2])), ChainingValue(([len()/2:])), , )
		}
		return ()
	}
}