#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <unistd.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sodium.h>
#include <pawstd.h>
#define KEY_SIZE crypto_secretbox_KEYBYTES
#define SALT_SIZE crypto_pwhash_SALTBYTES
#define BUF_SIZE 1024

bool stdinput = false;

size_t fileSize(FILE *file) {
	fseek(file,0,SEEK_END);
	size_t size = ftell(file);
	fseek(file,0,SEEK_SET);
	return size;
}

bool keyGen(const unsigned char* salt, const char* password, unsigned char* key) {
	fprintf(stderr,NOR"Beginning key generation...\n");
	if (crypto_pwhash(
				key,KEY_SIZE,
				password,strlen(password),
				salt,crypto_pwhash_OPSLIMIT_INTERACTIVE,
				crypto_pwhash_MEMLIMIT_INTERACTIVE,
				crypto_pwhash_ALG_DEFAULT) != 0) {
		fprintf(stderr,ERR"Out of memory! Key could not be generated.\n");
		return false;
	}
	fprintf(stderr,OK"Key generation successful!\n");
	return true;
}

int encryptMessage(const char* inputFile, const char* outputFile, const char* password) {

	// Generate salt
	unsigned char salt[SALT_SIZE];
	randombytes_buf(salt, SALT_SIZE);
	
	// Key generation from password
	unsigned char key[KEY_SIZE];
	if (!keyGen(salt,password,key)) {
		return 1;
	}

	fprintf(stderr,NOR"Reading file...\n");

	FILE *outFile = fopen(outputFile,"wb");
	if (outFile == NULL) {
		fprintf(stderr,ERR"Could not open output file!\n");
		return 1;
	}

	unsigned char* decrypted;
	size_t decLen;

	// Check if input is stdin, and read the input
	if (stdinput) {
		// Begin reading into buffer
		unsigned char buffer[BUF_SIZE];
		size_t inputSize = 0;
		unsigned char c;
		unsigned char* input = malloc(BUF_SIZE);
		if (input == NULL) {
			fprintf(stderr,ERR"Memory allocation error.");
			fclose(outFile);
			return 1;
		}
		int i = 0;
		c = fgetc(stdin);
		while (feof(stdin) == 0) {
			inputSize++;
			if (i < BUF_SIZE) {
				buffer[i] = c;
				i++;
			} else {
				char *old = input;
				input = realloc(input, inputSize);
				if (input == NULL) {
					fprintf(stderr,ERR"Memory allocation error.");
					fclose(outFile);
					free(old);
					return 1;
				}
				memcpy(input + inputSize - BUF_SIZE,buffer,BUF_SIZE);
				i = 0;
			}
			c = fgetc(stdin);
		}
		if (i > 0) {
			char *old = input;
			input = realloc(input, inputSize);
			if (input == NULL) {
				fprintf(stderr,ERR"Memory allocation error.");
				fclose(outFile);
				free(old);
				return 1;
			}
			memcpy(input + inputSize - i,buffer,i);
		}
		decrypted = input;
		decLen = inputSize;
	} else {
		// Open input file
		FILE *inFile = fopen(inputFile,"rb");
		if (inFile == NULL || outFile == NULL) {
			fprintf(stderr,ERR"Could not open input file!\n");
			return 1;
		}

		// Read input file
		fprintf(stderr,NOR"Reading input filesize...\n");
		decLen = fileSize(inFile);
		fprintf(stderr,OK"File is %d bytes.\n",decLen);
		decrypted = malloc(decLen);

		if (fread(decrypted,1,decLen,inFile) != decLen) {
			fprintf(stderr,ERR"Error reading from file.\n");
			fclose(inFile);
			fclose(outFile);
			return 1;
		}
		fclose(inFile);
	}

	fprintf(stderr,OK"Input read successfully!\n");
	fprintf(stderr,NOR"Beginning encryption...\n");

	// Generate a nonce, write headers and encrypted message
	unsigned char nonce[crypto_secretbox_NONCEBYTES];
	randombytes_buf(nonce,sizeof(nonce));

	// Encrypt the data
	unsigned char encrypted[decLen + crypto_secretbox_MACBYTES];
	crypto_secretbox_easy(encrypted, decrypted, decLen, nonce, key);

	// Patchy but correct-ish attempt to solve annoying stdout issue
	size_t totalSize = strlen("gneurshk") + sizeof(salt) + sizeof(nonce) + sizeof(encrypted);
	size_t offset = 0;
	unsigned char* outputBuffer = malloc(totalSize);
	if (outputBuffer == NULL) {
		fprintf(stderr,ERR"Memory allocation error.\n");
		return 1;
	}
	memcpy(outputBuffer + offset, "gneurshk", strlen("gneurshk"));
	offset += strlen("gneurshk");

	memcpy(outputBuffer + offset, salt, sizeof(salt));
	offset += sizeof(salt);

	memcpy(outputBuffer + offset, nonce, sizeof(nonce));
	offset += sizeof(nonce);

	memcpy(outputBuffer + offset, encrypted, sizeof(encrypted));

	fprintf(stderr,NOR"Writing encrypted data...\n");

	if(fwrite(outputBuffer, 1, totalSize, outFile) != totalSize) {
		fprintf(stderr,ERR"Error writing encrypted data to file.\n");
		fclose(outFile);
		return 1;
	}

	fclose(outFile);
	free(decrypted);
	free(outputBuffer);

	fprintf(stderr,"\n"OK"File encrypted!\n");

	return 0;
}

int decryptMessage(const char* inputFile, const char* outputFile, const char* password) {
	// Open output file
	FILE *outFile = fopen(outputFile,"wb");
	if (outFile == NULL) {
		fprintf(stderr,ERR"Could not open output file!\n");
		return 1;
	}

	// Variables
	unsigned char salt[SALT_SIZE];
	unsigned char nonce[crypto_secretbox_NONCEBYTES];
	

	unsigned char* fullInput;
	size_t inLen;

	// Check if input is stdin, and read the input
	if (stdinput) {
		// Begin reading into buffer
		unsigned char buffer[BUF_SIZE];
		size_t inputSize = 0;
		unsigned char c;
		unsigned char* input = malloc(BUF_SIZE);
		if (input == NULL) {
			fprintf(stderr,ERR"Memory allocation error.");
			fclose(outFile);
			return 1;
		}
		int i = 0;
		c = fgetc(stdin);
		while (feof(stdin) == 0) {
			inputSize++;
			if (i < BUF_SIZE) {
				buffer[i] = c;
				i++;
			} else {
				char *old = input;
				input = realloc(input, inputSize);
				if (input == NULL) {
					fprintf(stderr,ERR"Memory allocation error.");
					fclose(outFile);
					free(old);
					return 1;
				}
				memcpy(input + inputSize - BUF_SIZE,buffer,BUF_SIZE);
				i = 0;
			}
			c = fgetc(stdin);
		}
		if (i > 0) {
			char *old = input;
			input = realloc(input, inputSize);
			if (input == NULL) {
				fprintf(stderr,ERR"Memory allocation error.");
				fclose(outFile);
				free(old);
				return 1;
			}
			memcpy(input + inputSize - i,buffer,i);
		}
		fullInput = input;
		inLen = inputSize;
	} else {	
		FILE *inFile = fopen(inputFile,"rb");
		
		// Get the size of the file and read it
		size_t inputSize = fileSize(inFile);
		unsigned char* input = malloc(inputSize);

		if (fread(input,1,inputSize,inFile) != inputSize) {
			fprintf(stderr,ERR"Error reading from input file.\n");
			fclose(inFile);
			fclose(outFile);
			return 1;
		}
		
		fclose(inFile);
		fullInput = input;
		inLen = inputSize;
	}

	size_t encLen = inLen - sizeof(salt) - sizeof(nonce) - 8;

	fprintf(stderr,DBG"Size of encrypted file: %d bytes.\n",inLen);
	fprintf(stderr,DBG"This means the encrypted content is %d bytes.\n",encLen);

	unsigned char encrypted[encLen];

	// Verify file
	size_t offset = 0;
	if (memcmp(fullInput,"gneurshk",strlen("gneurshk")) != 0) {
		fprintf(stderr,ERR"Invalid header.\n");
		fprintf(stderr,ERR"Make sure the input file was signed by this program!\n");
		fclose(outFile);
		return 1;
	}
	fprintf(stderr,OK"Valid header! Reading the rest...\n");
	offset += strlen("gneurshk");

	// Read salt and nonce
	memcpy(salt, fullInput + offset, sizeof(salt));
	offset += sizeof(salt);

	memcpy(nonce, fullInput + offset, sizeof(nonce));
	offset += sizeof(nonce);

	memcpy(encrypted, fullInput + offset, sizeof(encrypted));

	fprintf(stderr,OK"Data retrieved.\n");

	// Key
	unsigned char key[KEY_SIZE];
	
	if (!keyGen(salt,password,key)) {
		return 1;
	}

	fprintf(stderr,OK"Proceeding to decrypt file...\n");

	size_t decLen = encLen - crypto_secretbox_MACBYTES;
	unsigned char decrypted[decLen];

	if (crypto_secretbox_open_easy(decrypted,encrypted,encLen,nonce,key) < 0) {
		fprintf(stderr,ERR"Error decrypting file.\n");
		fclose(outFile);
		return 1;
	}

	if (fwrite(decrypted,1,decLen,outFile) != decLen) {
		fprintf(stderr,ERR"Error writing data to file.\n");
		fclose(outFile);
		return 1;
	}

	fclose(outFile);
	
	fprintf(stderr,"\n"OK"File decrypted!\n");

	return 0;
}

bool isFile(const char* filename) {
	struct stat buffer;
	return (stat(filename, &buffer) == 0);
}

int main(int argc, char *argv[]) {
	fprintf(stderr,"\n- NetPaws Salty - File Encryption Program\n");
	fprintf(stderr,"- 2024 Ignacio Rivero\n");
	fprintf(stderr,"- FOR INTERNAL USE ONLY\n\n");
	// Initialize libsodium
	if (sodium_init() < 0) {
		fprintf(stderr,ERR"libsodium initialization failed! It is not safe to proceed.\n");
		return 1;
	}

	// Handle input, output and password arguments
	int in = -1, out = -1, pass = -1;
	bool decrypt = false;
	
	int i = 1, exit = 0;
	while (i < argc && exit == 0) {
		if (strcmp (argv[i],"-in") == 0) {
			if (i+1 >= argc) {
				fprintf(stderr,ERR"Argument -in requires a file.\n");
				exit = 1;
			} else if (strcmp(argv[i+1],"-") == 0) {
				in = -2;
				i++;
			} else if (!isFile(argv[i+1])) {
				fprintf(stderr,ERR"File not found error: %s\n",argv[i+1]);
				exit = 1;
			} else if (in == -1) {
				in = ++i;
			} else {
				fprintf(stderr,ERR"Too many arguments.\n");
				exit = 1;
			}
		} else if (strcmp(argv[i],"-out") == 0) {
			if (i+1 >= argc) {
				fprintf(stderr,ERR"Argument -out requires a file.\n");
				exit = 1;
			} else if (strcmp(argv[i+1],"-") == 0) {
				out = -2;
				i++;
			} else if (out == -1) {
				out = ++i;
			} else {
				fprintf(stderr,ERR"Too many arguments.\n");
				exit = 1;
			}
		} else if (strcmp (argv[i],"-key") == 0) {
			if (i+1 >= argc) {
				fprintf(stderr,ERR"Argument -key requires a password.\n");
				exit = 1;
			} else if (pass == -1) {
				if (strlen(argv[i+1]) > 128) {
					fprintf(stderr,ERR"Password too long.");
					exit = 1;
				} else {
					pass = ++i;
				}
			} else {
				fprintf(stderr,ERR"Too many arguments.\n");
				exit = 1;
			}
		} else if (strcmp (argv[i],"-d") == 0) {
			decrypt = true;
		} else {
			fprintf(stderr,ERR"Invalid argument: %s\n",argv[i]);
			exit = 1;
		}
		i++;
	}

	if (exit != 0)
		return exit;

	// Set input and output filenames, or go to standard I/O if none
	char input[FILENAME_MAX];
	char output[FILENAME_MAX];
	char psw[129];

	if (in == -1) {
		fprintf(stderr,NOR"No input file, reading from stdin.\n");
		stdinput = true;
	} else if (in == -2) {
		fprintf(stderr,NOR"Reading from stdin.\n");
		stdinput = true;
	} else {
		snprintf(input,sizeof(input),argv[in]);
	}

	if (out == -1) {
		fprintf(stderr,NOR"No output file, writing to stdout.\n");
		snprintf(output,sizeof(output),"/dev/stdout");
	} else if (out == -2) {
		fprintf(stderr,NOR"Writing to stdout.\n");
		snprintf(output,sizeof(output),"/dev/stdout");
	} else {
		snprintf(output,sizeof(output),argv[out]);
	}

	char* password;

	// Set password and run!
	if (pass == -1) {
		password = getpass("Enter your encryption password: ");
	} else {
		password = argv[pass];
	}

	if (decrypt) {
			return decryptMessage(input,output,password);
		} else {
			return encryptMessage(input,output,password);
		}
}