// Copyright 2018 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

package gstr

// Soundex calculates the soundex key of a string.
// See http://php.net/manual/en/function.soundex.php.
func Soundex(str string) string {
	if str == "" {
		panic("str: cannot be an empty string")
	}
	table := [26]rune{
		'0', '1', '2', '3', // A, B, C, D
		'0', '1', '2', // E, F, G
		'0',                          // H
		'0', '2', '2', '4', '5', '5', // I, J, K, L, M, N
		'0', '1', '2', '6', '2', '3', // O, P, Q, R, S, T
		'0', '1', // U, V
		'0', '2', // W, X
		'0', '2', // Y, Z
	}
	last, code, small := -1, 0, 0
	sd := make([]rune, 4)
	// build soundex string
	for i := 0; i < len(str) && small < 4; i++ {
		// ToUpper
		char := str[i]
		if char < '\u007F' && 'a' <= char && char <= 'z' {
			code = int(char - 'a' + 'A')
		} else {
			code = int(char)
		}
		if code >= 'A' && code <= 'Z' {
			if small == 0 {
				sd[small] = rune(code)
				small++
				last = int(table[code-'A'])
			} else {
				code = int(table[code-'A'])
				if code != last {
					if code != 0 {
						sd[small] = rune(code)
						small++
					}
					last = code
				}
			}
		}
	}
	// pad with "0"
	for ; small < 4; small++ {
		sd[small] = '0'
	}
	return string(sd)
}