restructures the code

src/curl.c

@@ -0,0 +1,67 @@
+#include <curl/curl.h>
+#include <curl/easy.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "curl.h"
+
+#define BASE_URL_SIZE 38
+
+void init_string(string* s)
+{
+	s->len = 0;
+	s->buf = malloc(s->len + 1);
+
+	if (NULL == s->buf) {
+		fprintf(stderr, "malloc() failed!\n");
+		exit(EXIT_FAILURE);
+	}
+	s->buf[0] = '\0';
+}
+
+size_t writefunc(void* ptr, size_t size, size_t nmemb, string* s)
+{
+	size_t new_len = s->len + (size * nmemb);
+	s->buf = realloc(s->buf, new_len + 1);
+	if (NULL == s->buf) {
+		fprintf(stderr, "realloc() failed!\n");
+		exit(EXIT_FAILURE);
+	}
+	memcpy(s->buf + s->len, ptr, size * nmemb);
+	s->buf[new_len] = '\0';
+	s->len = new_len;
+	return size * nmemb;
+}
+
+CURLcode perform_book_get(char* isbn, string* s)
+{
+	CURL* handler;
+	char* base_url;
+	size_t finalurl_size = BASE_URL_SIZE + 15;
+	char finalurl[finalurl_size];
+	CURLcode result;
+
+	handler = curl_easy_init();
+	if (!handler) {
+		fprintf(stderr, "cURL failed to initialize!\n");
+		exit(EXIT_FAILURE);
+	}
+
+	base_url = "https://openlibrary.org/search.json?q=";
+
+	// Setup the URL for the request
+	snprintf(finalurl, finalurl_size, "%s%s", base_url, isbn);
+
+	curl_easy_setopt(handler, CURLOPT_URL, finalurl);
+	curl_easy_setopt(handler, CURLOPT_HTTPGET, 1L);
+	curl_easy_setopt(handler, CURLOPT_WRITEFUNCTION, writefunc);
+	curl_easy_setopt(handler, CURLOPT_WRITEDATA, s);
+
+	result = curl_easy_perform(handler);
+
+	// Always clean up
+	curl_easy_cleanup(handler);
+
+	return result;
+
+}

src/curl.h

@@ -0,0 +1,40 @@
+#ifndef CURL_H
+#define CURL_H
+
+/**
+ * struct string_t
+ * char* buf - The buffer containing the string data
+ * size_t len - The length of the buffer
+ */
+typedef struct string_t {
+	char* buf;
+	size_t len;
+} string;
+
+/**
+ * void init_string
+ * string* s - The string struct
+ *
+ * Initializes the string struct
+ */
+void init_string(string* s);
+
+/**
+ * size_t writefunc
+ *
+ * The arguments from CURLOPT_WRITEFUNCTION
+ *
+ * Writes the cURL get into the string struct
+ */
+size_t writefunc(void* ptr, size_t size, size_t nmemb, string* s);
+
+/**
+ * CURLcode perform_book_get
+ * char* isbn - The ISBN
+ * string* s - The string struct to place the GET output in
+ *
+ * Performs a GET request with the ISBN
+ */
+CURLcode perform_book_get(char* isbn, string* s);
+
+#endif

src/json.c

@@ -0,0 +1,70 @@
+#include <curl/curl.h>
+#include <cjson/cJSON.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "curl.h"
+#include "json.h"
+
+#define MAX_BUF_LEN 1024
+
+void check_valid_query(cJSON* numfound)
+{
+	if (0 != numfound->valueint)
+		return;
+	fprintf(stderr, "No ISBN found!\n");
+	exit(EXIT_FAILURE);
+}
+
+void get_authors(cJSON* bookinfo, char authors[256])
+{
+	char* temp_author;
+	size_t new_len;
+	cJSON* author_arr = cJSON_GetObjectItemCaseSensitive(bookinfo, "author_name")->child;
+
+	snprintf(authors, strlen(author_arr->valuestring) + 1, "%s", author_arr->valuestring);
+	author_arr = author_arr->next;
+
+	while (NULL != author_arr) {
+		// The plus 1 is for the \0, the plus 2 is for the ", "
+		new_len = strlen(authors) + strlen(author_arr->valuestring) + 1 + 2;
+
+		temp_author = malloc(sizeof(char) * new_len);
+		snprintf(temp_author, new_len, "%s, %s", authors, author_arr->valuestring);
+		memcpy(authors, temp_author, new_len);
+
+		free(temp_author);
+
+		author_arr = author_arr->next;
+	}
+}
+
+void parse_json(string* s, char* isbn, book_t* book)
+{
+	char authors[MAX_BUF_LEN];
+
+	cJSON* json = cJSON_Parse(s->buf);
+	if (NULL == json) {
+		const char* error_ptr = cJSON_GetErrorPtr();
+		if (NULL != error_ptr)
+			fprintf(stderr, "JSON error: %s\n", error_ptr);
+		cJSON_Delete(json);
+		exit(EXIT_FAILURE);
+	}
+
+	check_valid_query(cJSON_GetObjectItemCaseSensitive(json, "numFound"));
+
+	cJSON* bookinfo = cJSON_GetObjectItemCaseSensitive(json, "docs")->child;
+
+	book->isbn = isbn;
+	book->title = cJSON_GetObjectItemCaseSensitive(bookinfo, "title")->valuestring;
+	book->year_of_publication = cJSON_GetObjectItemCaseSensitive(bookinfo, "first_publish_year")->valueint;
+	book->page_len = cJSON_GetObjectItemCaseSensitive(bookinfo, "number_of_pages_median")->valueint;
+
+	get_authors(bookinfo, authors);
+
+	// Need to malloc, because we need to copy authors into the book struct
+	book->authors = (char*) malloc(sizeof(char) * (strlen(authors) + 1));
+	memcpy(book->authors, authors, strlen(authors) + 1);
+}

src/json.h

@@ -0,0 +1,40 @@
+#ifndef JSON_H
+#define JSON_H
+
+#define MAX_BUF_LEN 1024
+
+typedef struct book_t {
+	char* isbn;
+	char* title;
+	char* authors;
+	int year_of_publication;
+	int page_len;
+} book_t;
+
+/**
+ * void check_valid_query
+ * cJSON* numfound - The json entry that contains the numFound value
+ *
+ * Checks if there are any search results in this json entry
+ */
+void check_valid_query(cJSON* numfound);
+
+/**
+ * void get_authors
+ * cJSON* bookinfo - The JSON entry that has all of the information about the book
+ * char* authors - The string to fill
+ *
+ * Takes the JSON entry from bookinfo and combines all of the authors into one final string
+ */
+void get_authors(cJSON* bookinfo, char* authors);
+
+/**
+ * void parse_json
+ * string* s - The string struct
+ * char* isbn - The ISBN
+ * book_t* book - The struct to fill with book information
+ *
+ * Parses through the given JSON entry and gathers all of the information we need
+ */
+void parse_json(string* s, char* isbn, book_t* book);
+#endif

src/main.c

@@ -0,0 +1,124 @@
+#include <curl/curl.h>
+#include <cjson/cJSON.h>
+#include <stdio.h> 
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "curl.h"
+#include "json.h"
+
+#define FILE_NAME "books.csv"
+
+#define MAX_BUF_LEN 1024 
+
+void print_book(book_t* book)
+{
+	printf("ISBN: %s\n", book->isbn);
+	printf("Title: %s\n", book->title);
+	printf("Author(s): %s\n", book->authors);
+	printf("(First) Year of Publication: %d\n", book->year_of_publication);
+	printf("Page length: %d\n", book->page_len);
+}
+
+void write_to_file(book_t* book)
+{
+	FILE* file;
+	int file_exists;
+
+	/**
+	 * We want to check if the file exists
+	 * if it doesnt, we create a new one
+	 * otherwise, we write to the existing one
+	 */
+	file_exists = access(FILE_NAME, F_OK);
+	if (0 != file_exists) {
+		file = fopen(FILE_NAME, "w");
+		fprintf(file, "isbn,title,authors,year of publication,page length\n");
+	} else {
+		file = fopen(FILE_NAME, "a");
+	}
+
+	// now we write the information
+	fprintf(file, "\"%s\",\"%s\",\"%s\",%d,%d\n", 
+			book->isbn, book->title, book->authors, book->year_of_publication, book->page_len);
+
+	fclose(file);
+}
+
+int main(int argc, char* argv[])
+{
+	char isbn_buf[14]; // want to hold a max of 14 so we can hold up to ISBN13s
+	char options[2];
+	CURLcode res;
+	book_t new_book;
+
+	if (3 != argc) {
+		printf("Usage: isbn [isbn] [options]\n");
+		return EXIT_FAILURE;
+	}
+
+	size_t input_len = strlen(argv[1]);
+	if (!(13 == input_len || 10 == input_len)) {
+		fprintf(stderr, "Invalid ISBN submitted!");
+		return EXIT_FAILURE;
+	}
+
+
+	/**
+	 * We must initialize cURL
+	 */
+	curl_global_init(CURL_GLOBAL_ALL);
+
+	/**
+	 * Grab the ISBN from argv
+	 */
+	snprintf(isbn_buf, 14, "%s", argv[1]);
+
+	/**
+	 * Grab the formatting options from argv
+	 */
+	snprintf(options, 2, "%s", argv[2]);
+	if (!(('w' == options[0]) || ('r' == options[0]))) {
+		fprintf(stderr, "Invalid option submitted!\n");
+		return EXIT_FAILURE;
+	}
+
+
+	/**
+	 * Setup the output string
+	 */
+	string get_output;
+	init_string(&get_output);
+
+	/**
+	 *  Perform the get request
+	 */ 
+	res = perform_book_get(isbn_buf, &get_output);
+	if (0 != res) {
+		fprintf(stderr, "Failed to perform the get request!\n");
+		return EXIT_FAILURE;
+	}
+
+
+	/**
+	 * Now we want to parse the JSON input
+	 */
+	parse_json(&get_output, isbn_buf, &new_book);
+
+	/**
+	 * We need to free this string
+	 */
+	free(get_output.buf);
+
+	/**
+	 * NOW we either print or save the book
+	 */
+	if (options[0] == 'w')
+		write_to_file(&new_book);
+	else if (options[0] == 'r')
+		print_book(&new_book);
+
+
+	return 0;
+}