/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2012 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <errno.h>
#include <assert.h>
#include <string.h>
#include <unistd.h>
#include <getopt.h>

#include "hashmap.h"
#include "util.h"
#include "path-util.h"
#include "log.h"
#include "pager.h"
#include "build.h"

static bool arg_no_pager = false;

static int equivalent(const char *a, const char *b) {
        char *x, *y;
        int r;

        x = canonicalize_file_name(a);
        if (!x)
                return -errno;

        y = canonicalize_file_name(b);
        if (!y) {
                free(x);
                return -errno;
        }

        r = path_equal(x, y);
        free(x);
        free(y);

        return r;
}

static int found_override(const char *top, const char *bottom) {
        char *dest;
        int k;
        pid_t pid;

        assert(top);
        assert(bottom);

        if (null_or_empty_path(top) > 0) {
                printf(ANSI_HIGHLIGHT_RED_ON "[MASK]" ANSI_HIGHLIGHT_OFF "       %s → %s\n", top, bottom);
                goto finish;
        }

        k = readlink_malloc(top, &dest);
        if (k >= 0) {
                if (equivalent(dest, bottom) > 0)
                        printf(ANSI_HIGHLIGHT_GREEN_ON "[EQUIVALENT]" ANSI_HIGHLIGHT_OFF " %s → %s\n", top, bottom);
                else
                        printf(ANSI_HIGHLIGHT_ON "[REDIRECT]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);

                free(dest);
                goto finish;
        }

        printf(ANSI_HIGHLIGHT_ON "[OVERRIDE]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);

        putchar('\n');

        fflush(stdout);

        pid = fork();
        if (pid < 0) {
                log_error("Failed to fork off diff: %m");
                return -errno;
        } else if (pid == 0) {
                execlp("diff", "diff", "-us", "--", bottom, top, NULL);
                log_error("Failed to execute diff: %m");
                _exit(1);
        }

        wait_for_terminate(pid, NULL);

        putchar('\n');

finish:

        return 0;
}

static int enumerate_dir(Hashmap *top, Hashmap *bottom, const char *path) {
        DIR *d;
        int r = 0;

        assert(top);
        assert(bottom);
        assert(path);

        d = opendir(path);
        if (!d) {
                if (errno == ENOENT)
                        return 0;

                log_error("Failed to enumerate %s: %m", path);
                return -errno;
        }

        for (;;) {
                struct dirent *de, buf;
                int k;
                char *p;

                k = readdir_r(d, &buf, &de);
                if (k != 0) {
                        r = -k;
                        goto finish;
                }

                if (!de)
                        break;

                if (!dirent_is_file(de))
                        continue;

                p = join(path, "/", de->d_name, NULL);
                if (!p) {
                        r = -ENOMEM;
                        goto finish;
                }

                path_kill_slashes(p);

                k = hashmap_put(top, path_get_file_name(p), p);
                if (k >= 0) {
                        p = strdup(p);
                        if (!p) {
                                r = -ENOMEM;
                                goto finish;
                        }
                } else if (k != -EEXIST) {
                        free(p);
                        r = k;
                        goto finish;
                }

                free(hashmap_remove(bottom, path_get_file_name(p)));
                k = hashmap_put(bottom, path_get_file_name(p), p);
                if (k < 0) {
                        free(p);
                        r = k;
                        goto finish;
                }
        }

finish:
        closedir(d);

        return r;
}

static int process_suffix(const char *prefixes, const char *suffix) {
        const char *p;
        char *f;
        Hashmap *top, *bottom;
        int r = 0, k;
        Iterator i;
        int n_found = 0;

        assert(prefixes);
        assert(suffix);

        top = hashmap_new(string_hash_func, string_compare_func);
        if (!top) {
                r = -ENOMEM;
                goto finish;
        }

        bottom = hashmap_new(string_hash_func, string_compare_func);
        if (!bottom) {
                r = -ENOMEM;
                goto finish;
        }

        NULSTR_FOREACH(p, prefixes) {
                char *t;

                t = join(p, "/", suffix, NULL);
                if (!t) {
                        r = -ENOMEM;
                        goto finish;
                }

                k = enumerate_dir(top, bottom, t);
                if (k < 0)
                        r = k;

                log_debug("Looking at %s", t);
                free(t);
        }

        HASHMAP_FOREACH(f, top, i) {
                char *o;

                o = hashmap_get(bottom, path_get_file_name(f));
                assert(o);

                if (path_equal(o, f))
                        continue;

                k = found_override(f, o);
                if (k < 0)
                        r = k;

                n_found ++;
        }

finish:
        if (top)
                hashmap_free_free(top);
        if (bottom)
                hashmap_free_free(bottom);

        return r < 0 ? r : n_found;
}

static int process_suffix_chop(const char *prefixes, const char *suffix) {
        const char *p;

        assert(prefixes);
        assert(suffix);

        if (!path_is_absolute(suffix))
                return process_suffix(prefixes, suffix);

        /* Strip prefix from the suffix */
        NULSTR_FOREACH(p, prefixes) {
                if (startswith(suffix, p)) {
                        suffix += strlen(p);;
                        suffix += strspn(suffix, "/");
                        return process_suffix(prefixes, suffix);
                }
        }

        log_error("Invalid suffix specification %s.", suffix);
        return -EINVAL;
}

static void help(void) {

        printf("%s [OPTIONS...] [SUFFIX...]\n\n"
               "Find overridden configuration files.\n\n"
               "  -h --help           Show this help\n"
               "     --version        Show package version\n"
               "     --no-pager       Do not pipe output into a pager\n",
               program_invocation_short_name);
}

static int parse_argv(int argc, char *argv[]) {

        enum {
                ARG_NO_PAGER = 0x100,
                ARG_VERSION
        };

        static const struct option options[] = {
                { "help",      no_argument,       NULL, 'h'          },
                { "version",   no_argument,       NULL, ARG_VERSION  },
                { "no-pager",  no_argument,       NULL, ARG_NO_PAGER },
                { NULL,        0,                 NULL, 0            }
        };

        int c;

        assert(argc >= 1);
        assert(argv);

        while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0) {

                switch (c) {

                case 'h':
                        help();
                        return 0;

                case ARG_VERSION:
                        puts(PACKAGE_STRING);
                        puts(DISTRIBUTION);
                        puts(SYSTEMD_FEATURES);
                        return 0;

                case ARG_NO_PAGER:
                        arg_no_pager = true;
                        break;

                case '?':
                        return -EINVAL;

                default:
                        log_error("Unknown option code %c", c);
                        return -EINVAL;
                }
        }

        return 1;
}

int main(int argc, char *argv[]) {

        const char prefixes[] =
                "/etc\0"
                "/run\0"
                "/usr/local/lib\0"
                "/usr/local/share\0"
                "/usr/lib\0"
                "/usr/share\0"
#ifdef HAVE_SPLIT_USR
                "/lib\0"
#endif
                ;

        const char suffixes[] =
                "sysctl.d\0"
                "tmpfiles.d\0"
                "modules-load.d\0"
                "binfmt.d\0"
                "systemd/system\0"
                "systemd/user\0"
                "systemd/system.preset\0"
                "systemd/user.preset\0"
                "udev/rules.d\0"
                "modprobe.d\0";

        int r = 0, k;
        int n_found = 0;

        log_parse_environment();
        log_open();

        r = parse_argv(argc, argv);
        if (r <= 0)
                goto finish;

        if (!arg_no_pager)
                pager_open();

        if (optind < argc) {
                int i;

                for (i = optind; i < argc; i++) {
                        k = process_suffix_chop(prefixes, argv[i]);
                        if (k < 0)
                                r = k;
                        else
                                n_found += k;
                }

        } else {
                const char *n;

                NULSTR_FOREACH(n, suffixes) {
                        k = process_suffix(prefixes, n);
                        if (k < 0)
                                r = k;
                        else
                                n_found += k;
                }
        }

        if (r >= 0)
                printf("\n%i overriden configuration files found.\n", n_found);

finish:
        pager_close();

        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}