/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2020 Baptiste Daroussin <bapt@FreeBSD.org>
 *
 * 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.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <ctype.h>
#include <getopt.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

extern int main_quotedprintable(int, char *[]);

static int
hexval(int c)
{
        if ('0' <= c && c <= '9')
                return c - '0';
        return (10 + c - 'A');
}


static int
decode_char(const char *s)
{
        return (16 * hexval(toupper(s[1])) + hexval(toupper(s[2])));
}


static void
decode_quoted_printable(const char *body, FILE *fpo, bool rfc2047)
{
        while (*body != '\0') {
                switch (*body) {
                case '=':
                        if (strlen(body) < 2) {
                                fputc(*body, fpo);
                                break;
                        }

                        if (body[1] == '\r' && body[2] == '\n') {
                                body += 2;
                                break;
                        }
                        if (body[1] == '\n') {
                                body++;
                                break;
                        }
                        if (strchr("0123456789ABCDEFabcdef", body[1]) == NULL) {
                                fputc(*body, fpo);
                                break;
                        }
                        if (strchr("0123456789ABCDEFabcdef", body[2]) == NULL) {
                                fputc(*body, fpo);
                                break;
                        }
                        fputc(decode_char(body), fpo);
                        body += 2;
                        break;
                case '_':
                        if (rfc2047) {
                                fputc(0x20, fpo);
                                break;
                        }
                        /* FALLTHROUGH */
                default:
                        fputc(*body, fpo);
                        break;
                }
                body++;
        }
}

static void
encode_quoted_printable(const char *body, FILE *fpo, bool rfc2047)
{
        const char *end = body + strlen(body);
        size_t linelen = 0;
        char prev = '\0';

        while (*body != '\0') {
                if (linelen == 75) {
                        fputs("=\r\n", fpo);
                        linelen = 0;
                }
                if (!isascii(*body) ||
                    *body == '=' ||
                    (*body == '.' && body + 1 < end &&
                      (body[1] == '\n' || body[1] == '\r'))) {
                        fprintf(fpo, "=%02X", (unsigned char)*body);
                        linelen += 2;
                        prev = *body;
                } else if (*body < 33 && *body != '\n') {
                        if ((*body == ' ' || *body == '\t') &&
                            body + 1 < end &&
                            (body[1] != '\n' && body[1] != '\r')) {
                                if (*body == 0x20 && rfc2047)
                                        fputc('_', fpo);
                                else
                                        fputc(*body, fpo);
                                prev = *body;
                        } else {
                                fprintf(fpo, "=%02X", (unsigned char)*body);
                                linelen += 2;
                                prev = '_';
                        }
                } else if (*body == '\n') {
                        if (prev == ' ' || prev == '\t') {
                                fputc('=', fpo);
                        }
                        fputc('\n', fpo);
                        linelen = 0;
                        prev = 0;
                } else {
                        fputc(*body, fpo);
                        prev = *body;
                }
                body++;
                linelen++;
        }
}

static void
qp(FILE *fp, FILE *fpo, bool encode, bool rfc2047)
{
        char *line = NULL;
        size_t linecap = 0;
        void (*codec)(const char *line, FILE *f, bool rfc2047);

        codec = encode ? encode_quoted_printable : decode_quoted_printable ;

        while (getline(&line, &linecap, fp) > 0)
                codec(line, fpo, rfc2047);
        free(line);
}

static void
usage(void)
{
        fprintf(stderr,
           "usage: bintrans qp [-d] [-r] [-o outputfile] [file name]\n");
}

int
main_quotedprintable(int argc, char *argv[])
{
        int ch;
        bool encode = true;
        bool rfc2047 = false;
        FILE *fp = stdin;
        FILE *fpo = stdout;

        static const struct option opts[] =
        {
                { "decode", no_argument,                NULL, 'd'},
                { "output", required_argument,          NULL, 'o'},
                { "rfc2047", no_argument,               NULL, 'r'},
                {NULL,          no_argument,            NULL, 0}
        };

        while ((ch = getopt_long(argc, argv, "+do:ru", opts, NULL)) != -1) {
                switch(ch) {
                case 'o':
                        fpo = fopen(optarg, "w");
                        if (fpo == NULL) {
                                perror(optarg);
                                exit(EXIT_FAILURE);
                        }
                        break;
                case 'u':
                        /* FALLTHROUGH for backward compatibility */
                case 'd':
                        encode = false;
                        break;
                case 'r':
                        rfc2047 = true;
                        break;
                default:
                        usage();
                        exit(EXIT_FAILURE);
                }
        };
        argc -= optind;
        argv += optind;
        if (argc > 0) {
                fp = fopen(argv[0], "r");
                if (fp == NULL) {
                        perror(argv[0]);
                        exit(EXIT_FAILURE);
                }
        }
        qp(fp, fpo, encode, rfc2047);

        return (EXIT_SUCCESS);
}