// Copyright 2026 Arctel.net
// SPDX-License-Identifier: Apache-2.0

package cap

import (
	"fmt"
	"strings"
)

// fnv1a returns the 32-bit FNV-1a hash of a string
//
//nolint:mnd // FNV-1a 算法位移常量
func fnv1a(str string) uint32 {
	var hash uint32 = 2166136261
	for i := range len(str) {
		hash ^= uint32(str[i])
		hash += (hash << 1) + (hash << 4) + (hash << 7) + (hash << 8) + (hash << 24)
	}
	return hash
}

// fnv1aResume resumes FNV-1a hashing from a given state
//
//nolint:mnd // FNV-1a 算法位移常量
func fnv1aResume(state uint32, str string) uint32 {
	h := state
	for i := range len(str) {
		h ^= uint32(str[i])
		h += (h << 1) + (h << 4) + (h << 7) + (h << 8) + (h << 24)
	}
	return h
}

// prngFromHash generates a hex string of specified length using an initial hash state
//
//nolint:mnd // xorshift 算法位移常量
func prngFromHash(initialHash uint32, length int) string {
	state := initialHash
	var result strings.Builder
	for result.Len() < length {
		state ^= state << 13
		state ^= state >> 17
		state ^= state << 5
		hexStr := fmt.Sprintf("%08x", state)
		result.WriteString(hexStr)
	}
	return result.String()[:length]
}