/* vi: set sw=4 ts=4: */
/*
 * popmaildir: a simple yet powerful POP3 client
 * Delivers contents of remote mailboxes to local Maildir
 *
 * Inspired by original utility by Nikola Vladov
 *
 * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */
#include "libbb.h"
#include "mail.h"

static void pop3_checkr(const char *fmt, const char *param, char **ret)
{
        const char *msg = command(fmt, param);
        char *answer = xmalloc_fgetline(stdin);
        if (answer && '+' == answer[0]) {
                if (timeout)
                        alarm(0);
                if (ret) {
                        // skip "+OK "
                        memmove(answer, answer + 4, strlen(answer) - 4);
                        *ret = answer;
                } else
                        free(answer);
                return;
        }
        bb_error_msg_and_die("%s failed: %s", msg, answer);
}

static void pop3_check(const char *fmt, const char *param)
{
        pop3_checkr(fmt, param, NULL);
}

int popmaildir_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int popmaildir_main(int argc UNUSED_PARAM, char **argv)
{
        char *buf;
        unsigned nmsg;
        char *hostname;
        pid_t pid;
        const char *retr;
#if ENABLE_FEATURE_POPMAILDIR_DELIVERY
        const char *delivery;
#endif
        unsigned opt_nlines = 0;

        enum {
                OPT_b = 1 << 0,         // -b binary mode. Ignored
                OPT_d = 1 << 1,         // -d,-dd,-ddd debug. Ignored
                OPT_m = 1 << 2,         // -m show used memory. Ignored
                OPT_V = 1 << 3,         // -V version. Ignored
                OPT_c = 1 << 4,         // -c use tcpclient. Ignored
                OPT_a = 1 << 5,         // -a use APOP protocol
                OPT_s = 1 << 6,         // -s skip authorization
                OPT_T = 1 << 7,         // -T get messages with TOP instead with RETR
                OPT_k = 1 << 8,         // -k keep retrieved messages on the server
                OPT_t = 1 << 9,         // -t90 set timeout to 90 sec
                OPT_R = 1 << 10,        // -R20000 remove old messages on the server >= 20000 bytes (requires -k). Ignored
                OPT_Z = 1 << 11,        // -Z11-23 remove messages from 11 to 23 (dangerous). Ignored
                OPT_L = 1 << 12,        // -L50000 not retrieve new messages >= 50000 bytes. Ignored
                OPT_H = 1 << 13,        // -H30 type first 30 lines of a message; (-L12000 -H30). Ignored
                OPT_M = 1 << 14,        // -M\"program arg1 arg2 ...\"; deliver by program. Treated like -F
                OPT_F = 1 << 15,        // -F\"program arg1 arg2 ...\"; filter by program. Treated like -M
        };

        // init global variables
        INIT_G();

        // parse options
        opt_complementary = "-1:dd:t+:R+:L+:H+";
        opts = getopt32(argv,
                "bdmVcasTkt:" "R:Z:L:H:" IF_FEATURE_POPMAILDIR_DELIVERY("M:F:"),
                &timeout, NULL, NULL, NULL, &opt_nlines
                IF_FEATURE_POPMAILDIR_DELIVERY(, &delivery, &delivery) // we treat -M and -F the same
        );
        //argc -= optind;
        argv += optind;

        // get auth info
        if (!(opts & OPT_s))
                get_cred_or_die(STDIN_FILENO);

        // goto maildir
        xchdir(*argv++);

        // launch connect helper, if any
        if (*argv)
                launch_helper((const char **)argv);

        // get server greeting
        pop3_checkr(NULL, NULL, &buf);

        // authenticate (if no -s given)
        if (!(opts & OPT_s)) {
                // server supports APOP and we want it?
                if ('<' == buf[0] && (opts & OPT_a)) {
                        union { // save a bit of stack
                                md5_ctx_t ctx;
                                char hex[16 * 2 + 1];
                        } md5;
                        uint32_t res[16 / 4];

                        char *s = strchr(buf, '>');
                        if (s)
                                s[1] = '\0';
                        // get md5 sum of "<stamp>password" string
                        md5_begin(&md5.ctx);
                        md5_hash(&md5.ctx, buf, strlen(buf));
                        md5_hash(&md5.ctx, G.pass, strlen(G.pass));
                        md5_end(&md5.ctx, res);
                        *bin2hex(md5.hex, (char*)res, 16) = '\0';
                        // APOP
                        s = xasprintf("%s %s", G.user, md5.hex);
                        pop3_check("APOP %s", s);
                        free(s);
                        free(buf);
                // server ignores APOP -> use simple text authentication
                } else {
                        // USER
                        pop3_check("USER %s", G.user);
                        // PASS
                        pop3_check("PASS %s", G.pass);
                }
        }

        // get mailbox statistics
        pop3_checkr("STAT", NULL, &buf);

        // prepare message filename suffix
        hostname = safe_gethostname();
        pid = getpid();

        // get messages counter
        // NOTE: we don't use xatou(buf) since buf is "nmsg nbytes"
        // we only need nmsg and atoi is just exactly what we need
        // if atoi fails to convert buf into number it returns 0
        // in this case the following loop simply will not be executed
        nmsg = atoi(buf);
        free(buf);

        // loop through messages
        retr = (opts & OPT_T) ? xasprintf("TOP %%u %u", opt_nlines) : "RETR %u";
        for (; nmsg; nmsg--) {

                char *filename;
                char *target;
                char *answer;
                FILE *fp;
#if ENABLE_FEATURE_POPMAILDIR_DELIVERY
                int rc;
#endif
                // generate unique filename
                filename  = xasprintf("tmp/%llu.%u.%s",
                        monotonic_us(), (unsigned)pid, hostname);

                // retrieve message in ./tmp/ unless filter is specified
                pop3_check(retr, (const char *)(ptrdiff_t)nmsg);

#if ENABLE_FEATURE_POPMAILDIR_DELIVERY
                // delivery helper ordered? -> setup pipe
                if (opts & (OPT_F|OPT_M)) {
                        // helper will have $FILENAME set to filename
                        xsetenv("FILENAME", filename);
                        fp = popen(delivery, "w");
                        unsetenv("FILENAME");
                        if (!fp) {
                                bb_perror_msg("delivery helper");
                                break;
                        }
                } else
#endif
                // create and open file filename
                fp = xfopen_for_write(filename);

                // copy stdin to fp (either filename or delivery helper)
                while ((answer = xmalloc_fgets_str(stdin, "\r\n")) != NULL) {
                        char *s = answer;
                        if ('.' == answer[0]) {
                                if ('.' == answer[1])
                                        s++;
                                else if ('\r' == answer[1] && '\n' == answer[2] && '\0' == answer[3])
                                        break;
                        }
                        //*strchrnul(s, '\r') = '\n';
                        fputs(s, fp);
                        free(answer);
                }

#if ENABLE_FEATURE_POPMAILDIR_DELIVERY
                // analyse delivery status
                if (opts & (OPT_F|OPT_M)) {
                        rc = pclose(fp);
                        if (99 == rc) // 99 means bail out
                                break;
//                      if (rc) // !0 means skip to the next message
                                goto skip;
//                      // 0 means continue
                } else {
                        // close filename
                        fclose(fp);
                }
#endif

                // delete message from server
                if (!(opts & OPT_k))
                        pop3_check("DELE %u", (const char*)(ptrdiff_t)nmsg);

                // atomically move message to ./new/
                target = xstrdup(filename);
                strncpy(target, "new", 3);
                // ... or just stop receiving on failure
                if (rename_or_warn(filename, target))
                        break;
                free(target);

#if ENABLE_FEATURE_POPMAILDIR_DELIVERY
 skip:
#endif
                free(filename);
        }

        // Bye
        pop3_check("QUIT", NULL);

        if (ENABLE_FEATURE_CLEAN_UP) {
                free(G.user);
                free(G.pass);
        }

        return EXIT_SUCCESS;
}