/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2026 Baptiste Daroussin <bapt@FreeBSD.org>
 */

/*
 * Speaks the same protocol as "pkg ssh" (see pkg-ssh(8)):
 *   -> ok: pkg-serve <version>
 *   <- get <file> <mtime>
 *   -> ok: <size>\n<data>   or   ok: 0\n   or   ko: <error>\n
 *   <- quit
 */

#include <sys/capsicum.h>
#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define VERSION "0.1"
#define BUFSZ 32768

static void
usage(void)
{
        fprintf(stderr, "usage: pkg-serve basedir\n");
        exit(EXIT_FAILURE);
}

int
main(int argc, char *argv[])
{
        struct stat st;
        cap_rights_t rights;
        char *line = NULL;
        char *file, *age;
        size_t linecap = 0, r, toread;
        ssize_t linelen;
        off_t remaining;
        time_t mtime;
        char *end;
        int fd, ffd;
        char buf[BUFSZ];
        const char *basedir;

        if (argc != 2)
                usage();

        basedir = argv[1];

        if ((fd = open(basedir, O_DIRECTORY | O_RDONLY | O_CLOEXEC)) < 0)
                err(EXIT_FAILURE, "open(%s)", basedir);

        cap_rights_init(&rights, CAP_READ, CAP_FSTATAT, CAP_LOOKUP,
            CAP_FCNTL);
        if (cap_rights_limit(fd, &rights) < 0 && errno != ENOSYS)
                err(EXIT_FAILURE, "cap_rights_limit");

        if (cap_enter() < 0 && errno != ENOSYS)
                err(EXIT_FAILURE, "cap_enter");

        printf("ok: pkg-serve " VERSION "\n");
        fflush(stdout);

        while ((linelen = getline(&line, &linecap, stdin)) > 0) {
                /* trim newline */
                if (linelen > 0 && line[linelen - 1] == '\n')
                        line[--linelen] = '\0';

                if (linelen == 0)
                        continue;

                if (strcmp(line, "quit") == 0)
                        break;

                if (strncmp(line, "get ", 4) != 0) {
                        printf("ko: unknown command '%s'\n", line);
                        fflush(stdout);
                        continue;
                }

                file = line + 4;

                if (*file == '\0') {
                        printf("ko: bad command get, expecting 'get file age'\n");
                        fflush(stdout);
                        continue;
                }

                /* skip leading slash */
                if (*file == '/')
                        file++;

                /* find the age argument */
                age = file;
                while (*age != '\0' && !isspace((unsigned char)*age))
                        age++;

                if (*age == '\0') {
                        printf("ko: bad command get, expecting 'get file age'\n");
                        fflush(stdout);
                        continue;
                }

                *age++ = '\0';

                /* skip whitespace */
                while (isspace((unsigned char)*age))
                        age++;

                if (*age == '\0') {
                        printf("ko: bad command get, expecting 'get file age'\n");
                        fflush(stdout);
                        continue;
                }

                errno = 0;
                mtime = (time_t)strtoimax(age, &end, 10);
                if (errno != 0 || *end != '\0' || end == age) {
                        printf("ko: bad number %s\n", age);
                        fflush(stdout);
                        continue;
                }

                if (fstatat(fd, file, &st, AT_RESOLVE_BENEATH) == -1) {
                        printf("ko: file not found\n");
                        fflush(stdout);
                        continue;
                }

                if (!S_ISREG(st.st_mode)) {
                        printf("ko: not a file\n");
                        fflush(stdout);
                        continue;
                }

                if (st.st_mtime <= mtime) {
                        printf("ok: 0\n");
                        fflush(stdout);
                        continue;
                }

                if ((ffd = openat(fd, file, O_RDONLY | O_RESOLVE_BENEATH)) == -1) {
                        printf("ko: file not found\n");
                        fflush(stdout);
                        continue;
                }

                printf("ok: %" PRIdMAX "\n", (intmax_t)st.st_size);
                fflush(stdout);

                remaining = st.st_size;
                while (remaining > 0) {
                        toread = sizeof(buf);
                        if ((off_t)toread > remaining)
                                toread = (size_t)remaining;
                        r = read(ffd, buf, toread);
                        if (r <= 0)
                                break;
                        if (fwrite(buf, 1, r, stdout) != r)
                                break;
                        remaining -= r;
                }
                close(ffd);
                if (remaining > 0)
                        errx(EXIT_FAILURE, "%s: file truncated during transfer",
                            file);
                fflush(stdout);
        }

        return (EXIT_SUCCESS);
}