/*
 * Path resolver program
 * 
 * This program is free software. It comes without any warranty, to
 * the extent permitted by applicable law. You can redistribute it
 * and/or modify it under the terms of the Do What The Fuck You Want
 * To Public License, Version 2, as published by Sam Hocevar. See
 * http://www.wtfpl.net/ for more details.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <unistd.h>
#include <sys/stat.h>

char* resolve_path(const char* input) {
    char* resolved_path = malloc(PATH_MAX);
    if (!resolved_path) {
        perror("Memory allocation failed");
        exit(EXIT_FAILURE);
    }
    
    // ケース1: 入力が '.' または '/' で始まる場合
    if (input[0] == '.' || input[0] == '/') {
        if (realpath(input, resolved_path) == NULL) {
            perror("realpath failed");
            free(resolved_path);
            return NULL;
        }
        return resolved_path;
    }
    
    // ケース2: 環境変数PATHからファイルを探す
    char* path_env = getenv("PATH");
    if (!path_env) {
        fprintf(stderr, "PATH environment variable not found\n");
        free(resolved_path);
        return NULL;
    }
    
    // PATHを:で分割して処理
    char* path_copy = strdup(path_env);
    char* path_token = strtok(path_copy, ":");
    struct stat st;
    
    while (path_token != NULL) {
        char full_path[PATH_MAX];
        snprintf(full_path, PATH_MAX, "%s/%s", path_token, input);
        
        // ファイルが存在するか確認
        if (stat(full_path, &st) == 0) {
            if (realpath(full_path, resolved_path) == NULL) {
                perror("realpath failed");
                free(path_copy);
                free(resolved_path);
                return NULL;
            }
            free(path_copy);
            return resolved_path;
        }
        
        path_token = strtok(NULL, ":");
    }
    
    free(path_copy);
    free(resolved_path);
    return NULL;
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
        return EXIT_FAILURE;
    }
    
    char* result = resolve_path(argv[1]);
    if (result) {
        printf("%s\n", result);
        free(result);
        return EXIT_SUCCESS;
    } else {
        fprintf(stderr, "File not found: %s\n", argv[1]);
        return EXIT_FAILURE;
    }
}