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

#define MAX_LEN 1024

void append(char* buffer, char c)
{
    for (int i = 0; i < MAX_LEN - 1; i++)
    {
        if (buffer[i] == '\0')
        {
            buffer[i] = c;
            buffer[i + 1] = '\0';
            return;
        }
    }
}

char* soundex_encoding(const char* s)
{
    const char MAP[] = {
        // A    B    C    D    E    F    G    H    I    J    K    L    M
        '0', '1', '2', '3', '0', '1', '2', '0', '0', '2', '2', '4', '5',
        // N    O    P    Q    R    S    T    U    V    W    X    Y    Z
        '5', '0', '1', '2', '6', '2', '3', '0', '1', '0', '2', '0', '2'};

    char* str = malloc(sizeof(MAX_LEN * (sizeof(char))));
    strcpy(str, s);
    str = strupr(str);
    char buffer[MAX_LEN];
    for (int i = 0; i < MAX_LEN; i++)
    {
        buffer[i] = '\0';
    }
    char prev = '?', prev_output = '?'; // 符号字符

    // 沿用首字符
    append(buffer, str[0]);
    for (int i = 1; i < strlen(str) && strlen(buffer) < 4; i++)
    {
        char c = str[i];
        // 判断字母是否为大写，且是否为符号字符
        if (c >= 'A' && c <= 'Z' && c != prev)
        {
            prev = c;
            char m = MAP[c - 'A'];
            // 去除重复的字母
            if (m != '0' && m != prev_output)
            {
                append(buffer, m);
                prev_output = m;
            }
        }
    }
    if (buffer[1] == MAP[str[0] - 'A'])
    {
        for (int i = 1; i < MAX_LEN - 1; i++)
        {
            buffer[i] = buffer[i + 1];
        }
    }
    free(str);

    // 如果长度不够4就添加0
    for (int i = strlen(buffer); i < 4; i++)
    {
        append(buffer, '0');
    }

    char* result = malloc(sizeof(MAX_LEN * (sizeof(char))));
    strcpy(result, buffer);
    return result;
}

int main(void)
{
    char* s[] = {"Marc", "Earc", "Taylor", "Tttaylor", "Taaaaaylor", "ChenQingyu", "ChanQingyu!!"};

    for (int i = 0; i < sizeof(s) / sizeof(s[0]); i++)
    {
        printf("%s\n", s[i]);
        printf("%s\n", soundex_encoding(s[i]));
        printf("\n");
    }

    return 0;
}