/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/* config/applet/usage bits are in bc.c */

//#include "libbb.h"
//#include "common_bufsiz.h"
#include <math.h>

#if 0
typedef unsigned data_t;
#define DATA_FMT ""
#elif 0
typedef unsigned long data_t;
#define DATA_FMT "l"
#else
typedef unsigned long long data_t;
#define DATA_FMT "ll"
#endif

struct globals {
        unsigned pointer;
        unsigned base;
        double stack[1];
} FIX_ALIASING;
enum { STACK_SIZE = (COMMON_BUFSIZE - offsetof(struct globals, stack)) / sizeof(double) };
#define G (*(struct globals*)bb_common_bufsiz1)
#define pointer   (G.pointer   )
#define base      (G.base      )
#define stack     (G.stack     )
#define INIT_G() do { \
        setup_common_bufsiz(); \
        base = 10; \
} while (0)

static unsigned check_under(void)
{
        unsigned p = pointer;
        if (p == 0)
                bb_simple_error_msg_and_die("stack underflow");
        return p - 1;
}

static void push(double a)
{
        if (pointer >= STACK_SIZE)
                bb_simple_error_msg_and_die("stack overflow");
        stack[pointer++] = a;
}

static double pop(void)
{
        unsigned p = check_under();
        pointer = p;
        return stack[p];
}

static void add(void)
{
        push(pop() + pop());
}

static void sub(void)
{
        double subtrahend = pop();

        push(pop() - subtrahend);
}

static void mul(void)
{
        push(pop() * pop());
}

#if ENABLE_FEATURE_DC_LIBM
static void power(void)
{
        double topower = pop();

        push(pow(pop(), topower));
}
#endif

static void divide(void)
{
        double divisor = pop();

        push(pop() / divisor);
}

static void mod(void)
{
        data_t d = pop();

        /* compat with dc (GNU bc 1.07.1) 1.4.1:
         * $ dc -e '4 0 % p'
         * dc: remainder by zero
         * 0
         */
        if (d == 0) {
                bb_simple_error_msg("remainder by zero");
                pop();
                push(0);
                return;
        }
        /* ^^^^ without this, we simply get SIGFPE and die */

        push((data_t) pop() % d);
}

static void and(void)
{
        push((data_t) pop() & (data_t) pop());
}

static void or(void)
{
        push((data_t) pop() | (data_t) pop());
}

static void eor(void)
{
        push((data_t) pop() ^ (data_t) pop());
}

static void not(void)
{
        push(~(data_t) pop());
}

static void set_output_base(void)
{
        static const char bases[] ALIGN1 = { 2, 8, 10, 16, 0 };
        unsigned b = (unsigned)pop();

        base = *strchrnul(bases, b);
        if (base == 0) {
                bb_error_msg("error, base %u is not supported", b);
                base = 10;
        }
}

static void print_base(double print)
{
        data_t x, i;

        x = (data_t) print;
        if (base == 10) {
                if (x == print) /* exactly representable as unsigned integer */
                        printf("%"DATA_FMT"u\n", x);
                else
                        printf("%g\n", print);
                return;
        }

        switch (base) {
        case 16:
                printf("%"DATA_FMT"x\n", x);
                break;
        case 8:
                printf("%"DATA_FMT"o\n", x);
                break;
        default: /* base 2 */
                i = MAXINT(data_t) - (MAXINT(data_t) >> 1);
                /* i is 100000...00000 */
                do {
                        if (x & i)
                                break;
                        i >>= 1;
                } while (i > 1);
                do {
                        bb_putchar('1' - !(x & i));
                        i >>= 1;
                } while (i);
                bb_putchar('\n');
        }
}

static void print_stack_no_pop(void)
{
        unsigned i = pointer;
        while (i)
                print_base(stack[--i]);
}

static void print_no_pop(void)
{
        print_base(stack[check_under()]);
}

struct op {
        const char name[4];
        void (*function) (void);
};

static const struct op operators[] ALIGN_PTR = {
#if ENABLE_FEATURE_DC_LIBM
        {"^",   power},
//      {"exp", power},
//      {"pow", power},
#endif
        {"%",   mod},
//      {"mod", mod},
        // logic ops are not standard, remove?
        {"and", and},
        {"or",  or},
        {"not", not},
        {"xor", eor},
        {"+",   add},
//      {"add", add},
        {"-",   sub},
//      {"sub", sub},
        {"*",   mul},
//      {"mul", mul},
        {"/",   divide},
//      {"div", divide},
        {"p", print_no_pop},
        {"f", print_stack_no_pop},
        {"o", set_output_base},
};

/* Feed the stack machine */
static void stack_machine(const char *argument)
{
        char *end;
        double number;
        const struct op *o;

 next:
//TODO: needs setlocale(LC_NUMERIC, "C")?
        number = strtod(argument, &end);
        if (end != argument) {
                argument = end;
                push(number);
                goto next;
        }

        /* We might have matched a digit, eventually advance the argument */
        argument = skip_whitespace(argument);

        if (*argument == '\0')
                return;

        o = operators;
        do {
                char *after_name = is_prefixed_with(argument, o->name);
                if (after_name) {
                        argument = after_name;
                        o->function();
                        goto next;
                }
                o++;
        } while (o != operators + ARRAY_SIZE(operators));

        bb_error_msg_and_die("syntax error at '%s'", argument);
}

static void process_file(FILE *fp)
{
        char *line;
        while ((line = xmalloc_fgetline(fp)) != NULL) {
                stack_machine(line);
                free(line);
        }
}

int dc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int dc_main(int argc UNUSED_PARAM, char **argv)
{
        bool script = 0;

        INIT_G();

        /* Run -e'SCRIPT' and -fFILE in order of appearance, then handle FILEs */
        for (;;) {
                int n = getopt(argc, argv, "e:f:");
                if (n <= 0)
                        break;
                switch (n) {
                case 'e':
                        script = 1;
                        stack_machine(optarg);
                        break;
                case 'f':
                        script = 1;
                        process_file(xfopen_for_read(optarg));
                        break;
                default:
                        bb_show_usage();
                }
        }
        argv += optind;

        if (*argv) {
                do
                        process_file(xfopen_for_read(*argv++));
                while (*argv);
        } else if (!script) {
                /* Take stuff from stdin if no args are given */
                process_file(stdin);
        }

        return EXIT_SUCCESS;
}