// Immortal Number Search
// by Daniel Marschall

// FUT TODO: Auch "r%10" und die letzte Ziffer übereinstimmen? + weitere konsistenzprüfungen

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdbool.h>
#include <time.h>
#include <gmp.h>

static inline char* getTimeStamp(char *timestamp_buf, const int len) {
	time_t now = time(0);
	strftime (timestamp_buf, len, "%a, %d %b %Y %T %z", localtime(&now));
	return timestamp_buf;
}

// ACHTUNG: BEI GROSSEN ZAHLEN GIBTS KERNEL PANIC, LOL (Speicher knapp)
static inline bool isImmortal(const mpz_t n, const unsigned int m) {
	// unsigned int m = strlen(n);

	mpz_t rop;
	mpz_init(rop);
	mpz_t m_pow;
	mpz_init(m_pow);

	mpz_ui_pow_ui(m_pow, 10, m);
	mpz_powm_ui(rop, n, 2, m_pow); // rop = n^2 % (mod 10^m)

	bool res = mpz_cmp(rop, n) == 0;

	mpz_clear(m_pow);
	mpz_clear(rop);

	return res;
}

static inline void mygetline(char* line, size_t size, FILE* myfile) {
	if (fgets(line, size, myfile) == NULL) {
		line = "";
		return;
	}

	size_t ln = strlen(line) - 1;
	if (line[ln] == '\n') line[ln] = '\0';

	ln = strlen(line) - 1;
	if (line[ln] == '\r') line[ln] = '\0';

	return;
}

int main(int argc, char** argv) {
	const char* SIGNATURE = "Immortal Number Report File Version 3.00";
	const char* END_SIG = "END OF REPORT";

	if (argc != 2) {
		fprintf(stderr, "Syntax: %s <datafile>\n", argv[0]);
		return 2;
	}

	const char* DATA_FILENAME = argv[1];

	unsigned char* a;

	unsigned /* long long */ int a_size = -1;
	unsigned /* long long */ int top = -1;

	char debug_timestamp[255];

	getTimeStamp(debug_timestamp, 255);
	printf("%s - Immort-Testprogramm gestartet\n", debug_timestamp);

	char line[255];
	FILE* myfile = fopen(DATA_FILENAME, "r");
	if (!myfile) {
		getTimeStamp(debug_timestamp, 255);
		fprintf(stderr, "%s - File not found: %s", debug_timestamp, DATA_FILENAME);
		return EXIT_FAILURE;
	}

	// __try {
		mygetline(line, sizeof line, myfile); // Major. signature
		if (strcmp(line, SIGNATURE) != 0 /* not equal */) {
			getTimeStamp(debug_timestamp, 255);
			fprintf(stderr, "%s - Load error: Wrong format signature. Expecting '%s' but is '%s'.\n", debug_timestamp, SIGNATURE, line);
			fclose(myfile);
			return EXIT_FAILURE;
		}
		mygetline(line, sizeof line, myfile); // Minor. signature
		mygetline(line, sizeof line, myfile); // ""

		mygetline(line, sizeof line, myfile); // "(Starting time)"
		mygetline(line, sizeof line, myfile); // Starting time
		mygetline(line, sizeof line, myfile); // ""

		mygetline(line, sizeof line, myfile); // "(Save timestamp)"
		mygetline(line, sizeof line, myfile); // Timestamp
		mygetline(line, sizeof line, myfile); // ""

		mygetline(line, sizeof line, myfile); // "(Base)"
		mygetline(line, sizeof line, myfile); // 10
		unsigned int base = atoi(line);
		if (base != 10) {
			getTimeStamp(debug_timestamp, 255);
			fprintf(stderr, "%s - This edition can only work with base = 10.\n", debug_timestamp);
			fclose(myfile);
			return EXIT_FAILURE;
		}
		mygetline(line, sizeof line, myfile); // ""

		mygetline(line, sizeof line, myfile); // "(Root)"
		mygetline(line, sizeof line, myfile); // 5
		unsigned int root = atoi(line);
		if (root != 5) {
			getTimeStamp(debug_timestamp, 255);
			fprintf(stderr, "%s - This edition can only work with root = 5.\n", debug_timestamp);
			fclose(myfile);
			return EXIT_FAILURE;
		}
		mygetline(line, sizeof line, myfile); // ""

		mygetline(line, sizeof line, myfile); // "(Digits)"
		mygetline(line, sizeof line, myfile); // C
		unsigned /* long long */ int u = atoi(line) - 1;
		mygetline(line, sizeof line, myfile); // ""

		mygetline(line, sizeof line, myfile); // "(r)"
		mygetline(line, sizeof line, myfile); // r
		mygetline(line, sizeof line, myfile); // ""

		a_size = u + 1;

		getTimeStamp(debug_timestamp, 255);
		fprintf(stderr, "%s - Count: %d\n", debug_timestamp, a_size);

		// a = new unsigned char[a_size];
		a = (unsigned char*) malloc(a_size * sizeof(unsigned char));
		if (a == NULL) {
			getTimeStamp(debug_timestamp, 255);
			fprintf(stderr, "%s - Memory allocation failed!\n", debug_timestamp);
			return EXIT_FAILURE;
		}

		mygetline(line, sizeof line, myfile); // "(Reversed notation)"
		do {
			mygetline(line, sizeof line, myfile);
			for (unsigned int i = 0; i < strlen(line); ++i) {
				if (++top >= a_size) {
					getTimeStamp(debug_timestamp, 255);
					fprintf(stderr, "%s - Corrupt: Formal and actual length mismatch! (Overflow)\n", debug_timestamp);
					return EXIT_FAILURE;
				}

				char toadd = line[i] - '0';
				a[top] = toadd;
			}
		} while (strcmp(line, "") != 0 /* not equal */);

		if (top+1 != a_size) {
			getTimeStamp(debug_timestamp, 255);
			fprintf(stderr, "%s - Corrupt: Formal and actual length mismatch! (Underflow)\n", debug_timestamp);
			return EXIT_FAILURE;
		}

		mygetline(line, sizeof line, myfile);

		if (strcmp(line, END_SIG) != 0 /* not equal */) {
			getTimeStamp(debug_timestamp, 255);
			fprintf(stderr, "%s - Corrupt: End-signature mismatch.\n", debug_timestamp);
			return EXIT_FAILURE;
		}
	// } __finally {
		fclose(myfile);
	// }

	getTimeStamp(debug_timestamp, 255);
	printf("%s - Beginne Immort-Test...\n", debug_timestamp);

	mpz_t num;
	mpz_init(num);
	mpz_t m_pow;
	mpz_init(m_pow);
	mpz_t ra;
	mpz_init(ra);
	for (unsigned int i = 0; i < top + 1 /* a.count() */; ++i) {
		unsigned char xa = a[i];
		if (i > 0) {
			xa = 9 - xa;
		} else {
			xa = 11 - xa;
		}

		mpz_ui_pow_ui(m_pow, 10, i);
		mpz_mul_ui(ra, m_pow, xa);
		mpz_add(num, num, ra);
	}
	mpz_clear(ra);
	mpz_clear(m_pow);

	if (!isImmortal(num, top + 1)) {
		getTimeStamp(debug_timestamp, 255);
		fprintf(stderr, "%s - Integrity test failed. Is not immortal.\n", debug_timestamp);

		mpz_clear(num);
		return EXIT_FAILURE;
	}

	mpz_clear(num);

	getTimeStamp(debug_timestamp, 255);
	printf("%s - Immort test succeed.\n", debug_timestamp);
	return EXIT_SUCCESS;
}