/*
 * Totally braindamaged mbox splitter program.
 *
 * It just splits a mbox into a list of files: "0001" "0002" ..
 * so you can process them further from there.
 */
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include "cache.h"

static const char git_mailsplit_usage[] =
"git-mailsplit [-d<prec>] [-f<n>] [-b] -o<directory> <mbox>...";

static int is_from_line(const char *line, int len)
{
        const char *colon;

        if (len < 20 || memcmp("From ", line, 5))
                return 0;

        colon = line + len - 2;
        line += 5;
        for (;;) {
                if (colon < line)
                        return 0;
                if (*--colon == ':')
                        break;
        }

        if (!isdigit(colon[-4]) ||
            !isdigit(colon[-2]) ||
            !isdigit(colon[-1]) ||
            !isdigit(colon[ 1]) ||
            !isdigit(colon[ 2]))
                return 0;

        /* year */
        if (strtol(colon+3, NULL, 10) <= 90)
                return 0;

        /* Ok, close enough */
        return 1;
}

/* Could be as small as 64, enough to hold a Unix "From " line. */
static char buf[4096];

/* Called with the first line (potentially partial)
 * already in buf[] -- normally that should begin with
 * the Unix "From " line.  Write it into the specified
 * file.
 */
static int split_one(FILE *mbox, const char *name, int allow_bare)
{
        FILE *output = NULL;
        int len = strlen(buf);
        int fd;
        int status = 0;
        int is_bare = !is_from_line(buf, len);

        if (is_bare && !allow_bare)
                goto corrupt;

        fd = open(name, O_WRONLY | O_CREAT | O_EXCL, 0666);
        if (fd < 0)
                die("cannot open output file %s", name);
        output = fdopen(fd, "w");

        /* Copy it out, while searching for a line that begins with
         * "From " and having something that looks like a date format.
         */
        for (;;) {
                int is_partial = (buf[len-1] != '\n');

                if (fputs(buf, output) == EOF)
                        die("cannot write output");

                if (fgets(buf, sizeof(buf), mbox) == NULL) {
                        if (feof(mbox)) {
                                status = 1;
                                break;
                        }
                        die("cannot read mbox");
                }
                len = strlen(buf);
                if (!is_partial && !is_bare && is_from_line(buf, len))
                        break; /* done with one message */
        }
        fclose(output);
        return status;

 corrupt:
        if (output)
                fclose(output);
        unlink(name);
        fprintf(stderr, "corrupt mailbox\n");
        exit(1);
}

int main(int argc, const char **argv)
{
        int nr = 0, nr_prec = 4;
        int allow_bare = 0;
        const char *dir = NULL;
        const char **argp;
        static const char *stdin_only[] = { "-", NULL };
        char *name;

        for (argp = argv+1; *argp; argp++) {
                const char *arg = *argp;

                if (arg[0] != '-')
                        break;
                /* do flags here */
                if ( arg[1] == 'd' ) {
                        nr_prec = strtol(arg+2, NULL, 10);
                        if (nr_prec < 3 || 10 <= nr_prec)
                                usage(git_mailsplit_usage);
                        continue;
                } else if ( arg[1] == 'f' ) {
                        nr = strtol(arg+2, NULL, 10);
                } else if ( arg[1] == 'b' && !arg[2] ) {
                        allow_bare = 1;
                } else if ( arg[1] == 'o' && arg[2] ) {
                        dir = arg+2;
                } else if ( arg[1] == '-' && !arg[2] ) {
                        argp++; /* -- marks end of options */
                        break;
                } else {
                        die("unknown option: %s", arg);
                }
        }

        if ( !dir ) {
                /* Backwards compatibility: if no -o specified, accept
                   <mbox> <dir> or just <dir> */
                switch (argc - (argp-argv)) {
                case 1:
                        dir = argp[0];
                        argp = stdin_only;
                        break;
                case 2:
                        stdin_only[0] = argp[0];
                        dir = argp[1];
                        argp = stdin_only;
                        break;
                default:
                        usage(git_mailsplit_usage);
                }
        } else {
                /* New usage: if no more argument, parse stdin */
                if ( !*argp )
                        argp = stdin_only;
        }

        name = xmalloc(strlen(dir) + 2 + 3 * sizeof(nr));

        while (*argp) {
                const char *file = *argp++;
                FILE *f = !strcmp(file, "-") ? stdin : fopen(file, "rt");
                int file_done = 0;

                if ( !f )
                        die ("cannot open mbox %s", file);

                if (fgets(buf, sizeof(buf), f) == NULL) {
                        if (f == stdin)
                                break; /* empty stdin is OK */
                        die("cannot read mbox %s", file);
                }

                while (!file_done) {
                        sprintf(name, "%s/%0*d", dir, nr_prec, ++nr);
                        file_done = split_one(f, name, allow_bare);
                }

                if (f != stdin)
                        fclose(f);
        }

        printf("%d\n", nr);
        return 0;
}