/* vi: set sw=4 ts=4: */
/*
 * Mini tr implementation for busybox
 *
 ** Copyright (c) 1987,1997, Prentice Hall   All rights reserved.
 *
 * The name of Prentice Hall may not be used to endorse or promote
 * products derived from this software without specific prior
 * written permission.
 *
 * Copyright (c) Michiel Huisjes
 *
 * This version of tr is adapted from Minix tr and was modified
 * by Erik Andersen <andersen@codepoet.org> to be used in busybox.
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
/* http://www.opengroup.org/onlinepubs/009695399/utilities/tr.html
 * TODO: graph, print
 */

//kbuild:lib-$(CONFIG_TR) += tr.o

//config:config TR
//config:       bool "tr"
//config:       default y
//config:       help
//config:         tr is used to squeeze, and/or delete characters from standard
//config:         input, writing to standard output.
//config:
//config:config FEATURE_TR_CLASSES
//config:       bool "Enable character classes (such as [:upper:])"
//config:       default y
//config:       depends on TR
//config:       help
//config:         Enable character classes, enabling commands such as:
//config:         tr [:upper:] [:lower:] to convert input into lowercase.
//config:
//config:config FEATURE_TR_EQUIV
//config:       bool "Enable equivalence classes"
//config:       default y
//config:       depends on TR
//config:       help
//config:         Enable equivalence classes, which essentially add the enclosed
//config:         character to the current set. For instance, tr [=a=] xyz would
//config:         replace all instances of 'a' with 'xyz'. This option is mainly
//config:         useful for cases when no other way of expressing a character
//config:         is possible.

//usage:#define tr_trivial_usage
//usage:       "[-cds] STRING1 [STRING2]"
//usage:#define tr_full_usage "\n\n"
//usage:       "Translate, squeeze, or delete characters from stdin, writing to stdout\n"
//usage:     "\n        -c      Take complement of STRING1"
//usage:     "\n        -d      Delete input characters coded STRING1"
//usage:     "\n        -s      Squeeze multiple output characters of STRING2 into one character"
//usage:
//usage:#define tr_example_usage
//usage:       "$ echo \"gdkkn vnqkc\" | tr [a-y] [b-z]\n"
//usage:       "hello world\n"

#include "libbb.h"

enum {
        ASCII = 256,
        /* string buffer needs to be at least as big as the whole "alphabet".
         * BUFSIZ == ASCII is ok, but we will realloc in expand
         * even for smallest patterns, let's avoid that by using *2:
         */
        TR_BUFSIZ = (BUFSIZ > ASCII*2) ? BUFSIZ : ASCII*2,
};

static void map(char *pvector,
                char *string1, unsigned string1_len,
                char *string2, unsigned string2_len)
{
        char last = '0';
        unsigned i, j;

        for (j = 0, i = 0; i < string1_len; i++) {
                if (string2_len <= j)
                        pvector[(unsigned char)(string1[i])] = last;
                else
                        pvector[(unsigned char)(string1[i])] = last = string2[j++];
        }
}

/* supported constructs:
 *   Ranges,  e.g.,  0-9   ==>  0123456789
 *   Escapes, e.g.,  \a    ==>  Control-G
 *   Character classes, e.g. [:upper:] ==> A...Z
 *   Equiv classess, e.g. [=A=] ==> A   (hmmmmmmm?)
 * not supported:
 *   \ooo-\ooo - octal ranges
 *   [x*N] - repeat char x N times
 *   [x*] - repeat char x until it fills STRING2:
 * # echo qwe123 | /usr/bin/tr 123456789 '[d]'
 * qwe[d]
 * # echo qwe123 | /usr/bin/tr 123456789 '[d*]'
 * qweddd
 */
static unsigned expand(const char *arg, char **buffer_p)
{
        char *buffer = *buffer_p;
        unsigned pos = 0;
        unsigned size = TR_BUFSIZ;
        unsigned i; /* can't be unsigned char: must be able to hold 256 */
        unsigned char ac;

        while (*arg) {
                if (pos + ASCII > size) {
                        size += ASCII;
                        *buffer_p = buffer = xrealloc(buffer, size);
                }
                if (*arg == '\\') {
                        arg++;
                        buffer[pos++] = bb_process_escape_sequence(&arg);
                        continue;
                }
                if (arg[1] == '-') { /* "0-9..." */
                        ac = arg[2];
                        if (ac == '\0') { /* "0-": copy verbatim */
                                buffer[pos++] = *arg++; /* copy '0' */
                                continue; /* next iter will copy '-' and stop */
                        }
                        i = (unsigned char) *arg;
                        while (i <= ac) /* ok: i is unsigned _int_ */
                                buffer[pos++] = i++;
                        arg += 3; /* skip 0-9 */
                        continue;
                }
                if ((ENABLE_FEATURE_TR_CLASSES || ENABLE_FEATURE_TR_EQUIV)
                 && *arg == '['
                ) {
                        arg++;
                        i = (unsigned char) *arg++;
                        /* "[xyz...". i=x, arg points to y */
                        if (ENABLE_FEATURE_TR_CLASSES && i == ':') { /* [:class:] */
#define CLO ":]\0"
                                static const char classes[] ALIGN1 =
                                        "alpha"CLO "alnum"CLO "digit"CLO
                                        "lower"CLO "upper"CLO "space"CLO
                                        "blank"CLO "punct"CLO "cntrl"CLO
                                        "xdigit"CLO;
                                enum {
                                        CLASS_invalid = 0, /* we increment the retval */
                                        CLASS_alpha = 1,
                                        CLASS_alnum = 2,
                                        CLASS_digit = 3,
                                        CLASS_lower = 4,
                                        CLASS_upper = 5,
                                        CLASS_space = 6,
                                        CLASS_blank = 7,
                                        CLASS_punct = 8,
                                        CLASS_cntrl = 9,
                                        CLASS_xdigit = 10,
                                        //CLASS_graph = 11,
                                        //CLASS_print = 12,
                                };
                                smalluint j;
                                char *tmp;

                                /* xdigit needs 8, not 7 */
                                i = 7 + (arg[0] == 'x');
                                tmp = xstrndup(arg, i);
                                j = index_in_strings(classes, tmp) + 1;
                                free(tmp);

                                if (j == CLASS_invalid)
                                        goto skip_bracket;

                                arg += i;
                                if (j == CLASS_alnum || j == CLASS_digit || j == CLASS_xdigit) {
                                        for (i = '0'; i <= '9'; i++)
                                                buffer[pos++] = i;
                                }
                                if (j == CLASS_alpha || j == CLASS_alnum || j == CLASS_upper) {
                                        for (i = 'A'; i <= 'Z'; i++)
                                                buffer[pos++] = i;
                                }
                                if (j == CLASS_alpha || j == CLASS_alnum || j == CLASS_lower) {
                                        for (i = 'a'; i <= 'z'; i++)
                                                buffer[pos++] = i;
                                }
                                if (j == CLASS_space || j == CLASS_blank) {
                                        buffer[pos++] = '\t';
                                        if (j == CLASS_space) {
                                                buffer[pos++] = '\n';
                                                buffer[pos++] = '\v';
                                                buffer[pos++] = '\f';
                                                buffer[pos++] = '\r';
                                        }
                                        buffer[pos++] = ' ';
                                }
                                if (j == CLASS_punct || j == CLASS_cntrl) {
                                        for (i = '\0'; i < ASCII; i++) {
                                                if ((j == CLASS_punct && isprint_asciionly(i) && !isalnum(i) && !isspace(i))
                                                 || (j == CLASS_cntrl && iscntrl(i))
                                                ) {
                                                        buffer[pos++] = i;
                                                }
                                        }
                                }
                                if (j == CLASS_xdigit) {
                                        for (i = 'A'; i <= 'F'; i++) {
                                                buffer[pos + 6] = i | 0x20;
                                                buffer[pos++] = i;
                                        }
                                        pos += 6;
                                }
                                continue;
                        }
                        /* "[xyz...", i=x, arg points to y */
                        if (ENABLE_FEATURE_TR_EQUIV && i == '=') { /* [=CHAR=] */
                                buffer[pos++] = *arg; /* copy CHAR */
                                if (!arg[0] || arg[1] != '=' || arg[2] != ']')
                                        bb_show_usage();
                                arg += 3;  /* skip CHAR=] */
                                continue;
                        }
                        /* The rest of "[xyz..." cases is treated as normal
                         * string, "[" has no special meaning here:
                         * tr "[a-z]" "[A-Z]" can be written as tr "a-z" "A-Z",
                         * also try tr "[a-z]" "_A-Z+" and you'll see that
                         * [] is not special here.
                         */
 skip_bracket:
                        arg -= 2; /* points to "[" in "[xyz..." */
                }
                buffer[pos++] = *arg++;
        }
        return pos;
}

/* NB: buffer is guaranteed to be at least TR_BUFSIZE
 * (which is >= ASCII) big.
 */
static int complement(char *buffer, int buffer_len)
{
        int len;
        char conv[ASCII];
        unsigned char ch;

        len = 0;
        ch = '\0';
        while (1) {
                if (memchr(buffer, ch, buffer_len) == NULL)
                        conv[len++] = ch;
                if (++ch == '\0')
                        break;
        }
        memcpy(buffer, conv, len);
        return len;
}

int tr_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tr_main(int argc UNUSED_PARAM, char **argv)
{
        int i;
        smalluint opts;
        ssize_t read_chars;
        size_t in_index, out_index;
        unsigned last = UCHAR_MAX + 1; /* not equal to any char */
        unsigned char coded, c;
        char *str1 = xmalloc(TR_BUFSIZ);
        char *str2 = xmalloc(TR_BUFSIZ);
        int str2_length;
        int str1_length;
        char *vector = xzalloc(ASCII * 3);
        char *invec  = vector + ASCII;
        char *outvec = vector + ASCII * 2;

#define TR_OPT_complement   (3 << 0)
#define TR_OPT_delete       (1 << 2)
#define TR_OPT_squeeze_reps (1 << 3)

        for (i = 0; i < ASCII; i++) {
                vector[i] = i;
                /*invec[i] = outvec[i] = FALSE; - done by xzalloc */
        }

        /* -C/-c difference is that -C complements "characters",
         * and -c complements "values" (binary bytes I guess).
         * In POSIX locale, these are the same.
         */

        opt_complementary = "-1";
        opts = getopt32(argv, "+Ccds"); /* '+': stop at first non-option */
        argv += optind;

        str1_length = expand(*argv++, &str1);
        str2_length = 0;
        if (opts & TR_OPT_complement)
                str1_length = complement(str1, str1_length);
        if (*argv) {
                if (argv[0][0] == '\0')
                        bb_error_msg_and_die("STRING2 cannot be empty");
                str2_length = expand(*argv, &str2);
                map(vector, str1, str1_length,
                                str2, str2_length);
        }
        for (i = 0; i < str1_length; i++)
                invec[(unsigned char)(str1[i])] = TRUE;
        for (i = 0; i < str2_length; i++)
                outvec[(unsigned char)(str2[i])] = TRUE;

        goto start_from;

        /* In this loop, str1 space is reused as input buffer,
         * str2 - as output one. */
        for (;;) {
                /* If we're out of input, flush output and read more input. */
                if ((ssize_t)in_index == read_chars) {
                        if (out_index) {
                                xwrite(STDOUT_FILENO, str2, out_index);
 start_from:
                                out_index = 0;
                        }
                        read_chars = safe_read(STDIN_FILENO, str1, TR_BUFSIZ);
                        if (read_chars <= 0) {
                                if (read_chars < 0)
                                        bb_perror_msg_and_die(bb_msg_read_error);
                                break;
                        }
                        in_index = 0;
                }
                c = str1[in_index++];
                if ((opts & TR_OPT_delete) && invec[c])
                        continue;
                coded = vector[c];
                if ((opts & TR_OPT_squeeze_reps) && last == coded
                 && (invec[c] || outvec[coded])
                ) {
                        continue;
                }
                str2[out_index++] = last = coded;
        }

        if (ENABLE_FEATURE_CLEAN_UP) {
                free(vector);
                free(str2);
                free(str1);
        }

        return EXIT_SUCCESS;
}