#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct {
char*(*copy)(const char*,char*,size_t);
char*(*allSplicedTogether)(const char**,char*,size_t,size_t);
char*(*push)(char*,char*,size_t);
size_t(*indexOf)(const char*,const char*);
size_t(*getLength)(const char*);
} String_;

/**
 * value:你需要复制的字符串
 * result:复制结果
 * max_length:result的预期最大长度(含'\0')
 * 如果max_length不够长，会只复制一部分
 */
static char* copy(const char* value,char*result,size_t max_length){
if(value == NULL||result == NULL)
return NULL;
size_t i = 0;
while(i < max_length-1){
result[i] = value[i];
i++;
if(value[i] == '\0'){
result[i] = '\0';
break;
}
}
return result;
}
/**
 * value:你需要拼接的字符串数组
 * result:拼接结果
 * result_max_length:result的预期最大长度(含'\0')
 * value_count:value的元素数量
 * 如果result_max_length不够长，会只复制一部分
 * value_count如果太长，会出现意外
 * 如果字符串数组中存在NULL，则会跳过该元素进行拼接
 */
static char* allSplicedTogether(const char** value,char* result,size_t result_max_length,size_t value_count){
if(value == NULL||result == NULL)
return NULL;
size_t length = 0;
for(size_t i = 0;i < value_count;i++){
if(value[i] == NULL)continue;
for(size_t ii = 0;value[i][ii] != '\0';ii++){
if(length == result_max_length-1){
i = value_count;
break;
}
result[length] = value[i][ii];
length++;
}
}
result[length+1] = '\0';
return result;
}
/**
 * value:延长的字符串
 * append_string:追加的字符串
 * max_length:value的最大长度(含\0)
 */
static char* push(char* value,const char* append_string,size_t max_length){
size_t length = strlen(value);
for(size_t i = 0;append_string[length+i] != '\0';i++){
if(length+i == max_length-1){
value[length+i+1] = '\0';
return value;
}
value[length+i] = append_string[i];
}
}
/**
 * 获取字符串长度
 */

static size_t getLength(const char* value){
size_t length = 0;
while(value[length] != '\0')
length++;
return length;
}

/**
 * value:被查找的字符串
 * element:要查找的字符串片段
 * 返回element第一次在value中出现的位置的索引
 */

static size_t indexOf(const char* value,const char* element){
size_t index = 0;
size_t satisfy = 0;
size_t should_satisfy = getLength(element);
while(value[index] != '\0'){
if(value[index] == element[satisfy])
satisfy++;
else
satisfy = 0;
if(satisfy == should_satisfy)
return index - satisfy + 1;
index++;
}
return (size_t)-1;
}



String_ String;
void createString(){
String.copy = copy;
String.allSplicedTogether = allSplicedTogether;
String.push = push;
String.getLength = getLength;
String.indexOf = indexOf;
}