// sum.c, version 1.0.1
// OMKOV coreutils sum
// Copyright (C) 2020, Jakob Wakeling
// MIT Licence

#include "util/error.h"
#include "util/optget.h"

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

#define VERSION "1.0.1"

static struct lop lops[] = {
	{ "help",    ARG_NUL, 256 },
	{ "version", ARG_NUL, 257 },
	{ NULL, 0, 0 }
};

static inline int sum(const char *file);

static inline uint32_t bsd(FILE *fi, size_t *fl);
static inline uint32_t sysv(FILE *fi, size_t *fl);

static uint32_t (*fn)(FILE *, size_t *) = bsd;

static void hlp(void);
static void ver(void);

int main(int ac, char *av[]) {
	struct opt opt = OPTGET_INIT; opt.str = "rs"; opt.lops = lops;
	for (int o; (o = optget(&opt, av, 1)) != -1;) switch (o) {
	case 'r': { fn = bsd; break; }
	case 's': { fn = sysv; break; }
	case 256: { hlp(); return 0; }
	case 257: { ver(); return 0; }
	default: { return 1; }
	}
	
	bool warned = false;
	
	if (opt.ind == ac) { sum(NULL); }
	else for (char **p = &av[opt.ind]; *p; ++p) if (sum(*p)) {
		warn("%s: %s", *p, serr()); warned = true;
	}
	
	return warned;
}

static inline int sum(const char *file) {
	FILE *fi; size_t bl = 0; register uint32_t sum;
	
	if (!file || (file[0] == '-' && file[1] == 0)) { fi = stdin; }
	else if (!(fi = fopen(file, "r"))) { return 1; }
	
	sum = fn(fi, &bl);
	
	printf("%u %zu", sum, bl);
	if (file) { printf(" %s", file); } fputc('\n', stdout);
	
	if (fi != stdin) { fclose(fi); } return 0;
}

static inline uint32_t bsd(FILE *fi, size_t *bl) {
	uint8_t buf[BUFSIZ * 16]; register uint16_t sum = 0;
	
	for (size_t c; (c = fread(buf, 1, sizeof (buf), fi)); *bl += c) {
		for (register size_t i = 0; i != c; ++i) {
			sum = (sum >> 1) + ((sum & 1) << 15);
			sum += buf[i]; sum &= 0xFFFF;
		}
	}
	
	*bl = *bl / 1024 + 1; return sum;
}

static inline uint32_t sysv(FILE *fi, size_t *bl) {
	uint8_t buf[BUFSIZ * 16]; register uint32_t sum = 0;
	
	for (size_t c; (c = fread(buf, 1, sizeof (buf), fi)); *bl += c) {
		for (register size_t i = 0; i != c; ++i) { sum += buf[i]; }
	}
	
	sum = (sum & 0xFFFF) + ((sum & 0xFFFFFFFF) >> 16);
	sum = (sum & 0xFFFF) + (sum >> 16);
	
	*bl = *bl / 512 + 1; return sum;
}

static void hlp(void) {
	puts("sum - write file checksums and block counts\n");
	puts("usage: sum [-rs] [file...]\n");
	puts("options:");
	puts("  -r         Use BSD algorithm and 1024 byte blocks");
	puts("  -s         Use System V algorithm and 512 byte blocks");
	puts("  --help     Display help information");
	puts("  --version  Display version information");
}

static void ver(void) {
	puts("OMKOV coreutils sum, version " VERSION);
	puts("Copyright (C) 2020, Jakob Wakeling");
	puts("MIT Licence (https://opensource.org/licenses/MIT)");
}