/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2007
 *      Herbert Xu <herbert@gondor.apana.org.au>.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <limits.h>
#include <errno.h>
#include <inttypes.h>
#include <stdlib.h>
#include <stdio.h>
#include "arith.h"
#include "arith_yacc.h"
#include "expand.h"
#include "shell.h"
#include "error.h"
#include "memalloc.h"
#include "output.h"
#include "options.h"
#include "var.h"

#if ARITH_BOR + 11 != ARITH_BORASS || ARITH_ASS + 11 != ARITH_EQ
#error Arithmetic tokens are out of order.
#endif

static const char *arith_startbuf;

const char *arith_buf;
union yystype yylval;

static int last_token;

#define ARITH_PRECEDENCE(op, prec) [op - ARITH_BINOP_MIN] = prec

static const char prec[ARITH_BINOP_MAX - ARITH_BINOP_MIN] = {
        ARITH_PRECEDENCE(ARITH_MUL, 0),
        ARITH_PRECEDENCE(ARITH_DIV, 0),
        ARITH_PRECEDENCE(ARITH_REM, 0),
        ARITH_PRECEDENCE(ARITH_ADD, 1),
        ARITH_PRECEDENCE(ARITH_SUB, 1),
        ARITH_PRECEDENCE(ARITH_LSHIFT, 2),
        ARITH_PRECEDENCE(ARITH_RSHIFT, 2),
        ARITH_PRECEDENCE(ARITH_LT, 3),
        ARITH_PRECEDENCE(ARITH_LE, 3),
        ARITH_PRECEDENCE(ARITH_GT, 3),
        ARITH_PRECEDENCE(ARITH_GE, 3),
        ARITH_PRECEDENCE(ARITH_EQ, 4),
        ARITH_PRECEDENCE(ARITH_NE, 4),
        ARITH_PRECEDENCE(ARITH_BAND, 5),
        ARITH_PRECEDENCE(ARITH_BXOR, 6),
        ARITH_PRECEDENCE(ARITH_BOR, 7),
};

#define ARITH_MAX_PREC 8

int letcmd(int, char **);

static __dead2 void yyerror(const char *s)
{
        error("arithmetic expression: %s: \"%s\"", s, arith_startbuf);
        /* NOTREACHED */
}

static arith_t arith_lookupvarint(char *varname)
{
        const char *str;
        char *p;
        arith_t result;

        str = lookupvar(varname);
        if (uflag && str == NULL)
                yyerror("variable not set");
        if (str == NULL || *str == '\0')
                str = "0";
        errno = 0;
        result = strtoarith_t(str, &p);
        if (errno != 0 || *p != '\0')
                yyerror("variable conversion error");
        return result;
}

static inline int arith_prec(int op)
{
        return prec[op - ARITH_BINOP_MIN];
}

static inline int higher_prec(int op1, int op2)
{
        return arith_prec(op1) < arith_prec(op2);
}

static arith_t do_binop(int op, arith_t a, arith_t b)
{

        switch (op) {
        default:
        case ARITH_REM:
        case ARITH_DIV:
                if (!b)
                        yyerror("division by zero");
                if (a == ARITH_MIN && b == -1)
                        yyerror("divide error");
                return op == ARITH_REM ? a % b : a / b;
        case ARITH_MUL:
                return (uintmax_t)a * (uintmax_t)b;
        case ARITH_ADD:
                return (uintmax_t)a + (uintmax_t)b;
        case ARITH_SUB:
                return (uintmax_t)a - (uintmax_t)b;
        case ARITH_LSHIFT:
                return (uintmax_t)a << (b & (sizeof(uintmax_t) * CHAR_BIT - 1));
        case ARITH_RSHIFT:
                return a >> (b & (sizeof(uintmax_t) * CHAR_BIT - 1));
        case ARITH_LT:
                return a < b;
        case ARITH_LE:
                return a <= b;
        case ARITH_GT:
                return a > b;
        case ARITH_GE:
                return a >= b;
        case ARITH_EQ:
                return a == b;
        case ARITH_NE:
                return a != b;
        case ARITH_BAND:
                return a & b;
        case ARITH_BXOR:
                return a ^ b;
        case ARITH_BOR:
                return a | b;
        }
}

static arith_t assignment(int var, int noeval);

static arith_t primary(int token, union yystype *val, int op, int noeval)
{
        arith_t result;

again:
        switch (token) {
        case ARITH_LPAREN:
                result = assignment(op, noeval);
                if (last_token != ARITH_RPAREN)
                        yyerror("expecting ')'");
                last_token = yylex();
                return result;
        case ARITH_NUM:
                last_token = op;
                return val->val;
        case ARITH_VAR:
                last_token = op;
                return noeval ? val->val : arith_lookupvarint(val->name);
        case ARITH_ADD:
                token = op;
                *val = yylval;
                op = yylex();
                goto again;
        case ARITH_SUB:
                *val = yylval;
                return -primary(op, val, yylex(), noeval);
        case ARITH_NOT:
                *val = yylval;
                return !primary(op, val, yylex(), noeval);
        case ARITH_BNOT:
                *val = yylval;
                return ~primary(op, val, yylex(), noeval);
        default:
                yyerror("expecting primary");
        }
}

static arith_t binop2(arith_t a, int op, int precedence, int noeval)
{
        for (;;) {
                union yystype val;
                arith_t b;
                int op2;
                int token;

                token = yylex();
                val = yylval;

                b = primary(token, &val, yylex(), noeval);

                op2 = last_token;
                if (op2 >= ARITH_BINOP_MIN && op2 < ARITH_BINOP_MAX &&
                    higher_prec(op2, op)) {
                        b = binop2(b, op2, arith_prec(op), noeval);
                        op2 = last_token;
                }

                a = noeval ? b : do_binop(op, a, b);

                if (op2 < ARITH_BINOP_MIN || op2 >= ARITH_BINOP_MAX ||
                    arith_prec(op2) >= precedence)
                        return a;

                op = op2;
        }
}

static arith_t binop(int token, union yystype *val, int op, int noeval)
{
        arith_t a = primary(token, val, op, noeval);

        op = last_token;
        if (op < ARITH_BINOP_MIN || op >= ARITH_BINOP_MAX)
                return a;

        return binop2(a, op, ARITH_MAX_PREC, noeval);
}

static arith_t and(int token, union yystype *val, int op, int noeval)
{
        arith_t a = binop(token, val, op, noeval);
        arith_t b;

        op = last_token;
        if (op != ARITH_AND)
                return a;

        token = yylex();
        *val = yylval;

        b = and(token, val, yylex(), noeval | !a);

        return a && b;
}

static arith_t or(int token, union yystype *val, int op, int noeval)
{
        arith_t a = and(token, val, op, noeval);
        arith_t b;

        op = last_token;
        if (op != ARITH_OR)
                return a;

        token = yylex();
        *val = yylval;

        b = or(token, val, yylex(), noeval | !!a);

        return a || b;
}

static arith_t cond(int token, union yystype *val, int op, int noeval)
{
        arith_t a = or(token, val, op, noeval);
        arith_t b;
        arith_t c;

        if (last_token != ARITH_QMARK)
                return a;

        b = assignment(yylex(), noeval | !a);

        if (last_token != ARITH_COLON)
                yyerror("expecting ':'");

        token = yylex();
        *val = yylval;

        c = cond(token, val, yylex(), noeval | !!a);

        return a ? b : c;
}

static arith_t assignment(int var, int noeval)
{
        union yystype val = yylval;
        int op = yylex();
        arith_t result;
        char sresult[DIGITS(result) + 1];

        if (var != ARITH_VAR)
                return cond(var, &val, op, noeval);

        if (op != ARITH_ASS && (op < ARITH_ASS_MIN || op >= ARITH_ASS_MAX))
                return cond(var, &val, op, noeval);

        result = assignment(yylex(), noeval);
        if (noeval)
                return result;

        if (op != ARITH_ASS)
                result = do_binop(op - 11, arith_lookupvarint(val.name), result);
        snprintf(sresult, sizeof(sresult), ARITH_FORMAT_STR, result);
        setvar(val.name, sresult, 0);
        return result;
}

arith_t arith(const char *s)
{
        struct stackmark smark;
        arith_t result;

        setstackmark(&smark);

        arith_buf = arith_startbuf = s;

        result = assignment(yylex(), 0);

        if (last_token)
                yyerror("expecting EOF");

        popstackmark(&smark);

        return result;
}

/*
 *  The exp(1) builtin.
 */
int
letcmd(int argc, char **argv)
{
        const char *p;
        char *concat;
        char **ap;
        arith_t i;

        if (argc > 1) {
                p = argv[1];
                if (argc > 2) {
                        /*
                         * Concatenate arguments.
                         */
                        STARTSTACKSTR(concat);
                        ap = argv + 2;
                        for (;;) {
                                while (*p)
                                        STPUTC(*p++, concat);
                                if ((p = *ap++) == NULL)
                                        break;
                                STPUTC(' ', concat);
                        }
                        STPUTC('\0', concat);
                        p = grabstackstr(concat);
                }
        } else
                p = "";

        i = arith(p);

        out1fmt(ARITH_FORMAT_STR "\n", i);
        return !i;
}