#include "cache.h"

#include <sys/types.h>
#include <dirent.h>

struct needs {
        unsigned char parent[20];
        unsigned char needs[20];
        char tag[10];
};

struct seen {
        unsigned char sha1[20];
        char tag[10];
        unsigned needed;
};

static struct needs *needs;
static struct seen *seen;

static int nr_seen, alloc_seen, nr_needs, alloc_needs;

/*
 * These two functions build up a graph in memory about
 * what objects we've referenced, and found, and types..
 */
static int compare_seen(const void *s1, const void *s2)
{
        return memcmp(s1, s2, 20);
}

static int lookup_seen(unsigned char *sha1, char *tag)
{
        int first = 0, last = nr_seen;

        while (last > first) {
                int next = (last + first) / 2;
                struct seen *s = seen + next;
                int cmp = memcmp(sha1, s->sha1, 20);

                if (cmp < 0) {
                        last = next;
                        continue;
                }
                if (cmp > 0) {
                        first = next+1;
                        continue;
                }
                if (strcmp(tag, s->tag))
                        break;
                s->needed++;
                return 1;
        }
        return 0;
}

static void check_connectivity(void)
{
        int i;

        /* Sort the "seen" tags for quicker lookup */
        qsort(seen, nr_seen, sizeof(struct seen), compare_seen);

        /* Look up all the requirements, warn about missing objects.. */
        for (i = 0; i < nr_needs; i++) {
                struct needs *n = needs + i;
                char hex[60];

                if (lookup_seen(n->needs, n->tag))
                        continue;
                strcpy(hex, sha1_to_hex(n->parent));
                printf("missing %s: %s referenced by %s\n", n->tag, sha1_to_hex(n->needs), hex);
        }

        /* Tell the user about things not referenced.. */
        for (i = 0; i < nr_seen; i++) {
                struct seen *s = seen + i;

                if (s->needed)
                        continue;
                printf("unreferenced %s: %s\n", s->tag, sha1_to_hex(s->sha1));
        }
}

static void mark_needs_sha1(unsigned char *parent, const char * tag, unsigned char *child)
{
        struct needs *n;

        if (nr_needs == alloc_needs) {
                alloc_needs = alloc_nr(alloc_needs);
                needs = realloc(needs, alloc_needs*sizeof(struct needs));
        }
        n = needs + nr_needs;
        nr_needs++;
        memcpy(n->parent, parent, 20);
        memcpy(n->needs, child, 20);
        strncpy(n->tag, tag, sizeof(n->tag));
}

static int mark_sha1_seen(unsigned char *sha1, char *tag)
{
        struct seen *s;

        if (nr_seen == alloc_seen) {
                alloc_seen = alloc_nr(alloc_seen);
                seen = realloc(seen, alloc_seen*sizeof(struct seen));
        }
        s = seen + nr_seen;
        memset(s, 0, sizeof(*s));
        nr_seen++;
        memcpy(s->sha1, sha1, 20);
        strncpy(s->tag, tag, sizeof(s->tag));
        
        return 0;
}

static int fsck_tree(unsigned char *sha1, void *data, unsigned long size)
{
        int warn_old_tree = 1;

        while (size) {
                int len = 1+strlen(data);
                unsigned char *file_sha1 = data + len;
                char *path = strchr(data, ' ');
                unsigned int mode;
                if (size < len + 20 || !path || sscanf(data, "%o", &mode) != 1)
                        return -1;

                /* Warn about trees that don't do the recursive thing.. */
                if (warn_old_tree && strchr(path, '/')) {
                        fprintf(stderr, "warning: fsck-cache: tree %s has full pathnames in it\n", sha1_to_hex(sha1));
                        warn_old_tree = 0;
                }

                data += len + 20;
                size -= len + 20;
                mark_needs_sha1(sha1, S_ISDIR(mode) ? "tree" : "blob", file_sha1);
        }
        return 0;
}

static int fsck_commit(unsigned char *sha1, void *data, unsigned long size)
{
        int parents;
        unsigned char tree_sha1[20];
        unsigned char parent_sha1[20];

        if (memcmp(data, "tree ", 5))
                return -1;
        if (get_sha1_hex(data + 5, tree_sha1) < 0)
                return -1;
        mark_needs_sha1(sha1, "tree", tree_sha1);
        data += 5 + 40 + 1;     /* "tree " + <hex sha1> + '\n' */
        parents = 0;
        while (!memcmp(data, "parent ", 7)) {
                if (get_sha1_hex(data + 7, parent_sha1) < 0)
                        return -1;
                mark_needs_sha1(sha1, "commit", parent_sha1);
                data += 7 + 40 + 1;     /* "parent " + <hex sha1> + '\n' */
                parents++;
        }
        if (!parents)
                printf("root: %s\n", sha1_to_hex(sha1));
        return 0;
}

static int fsck_entry(unsigned char *sha1, char *tag, void *data, unsigned long size)
{
        if (!strcmp(tag, "blob")) {
                /* Nothing to check */;
        } else if (!strcmp(tag, "tree")) {
                if (fsck_tree(sha1, data, size) < 0)
                        return -1;
        } else if (!strcmp(tag, "commit")) {
                if (fsck_commit(sha1, data, size) < 0)
                        return -1;
        } else
                return -1;
        return mark_sha1_seen(sha1, tag);
}

static int fsck_name(char *hex)
{
        unsigned char sha1[20];
        if (!get_sha1_hex(hex, sha1)) {
                unsigned long mapsize;
                void *map = map_sha1_file(sha1, &mapsize);
                if (map) {
                        char type[100];
                        unsigned long size;
                        void *buffer = NULL;
                        if (!check_sha1_signature(sha1, map, mapsize))
                                buffer = unpack_sha1_file(map, mapsize, type, &size);
                        munmap(map, mapsize);
                        if (buffer && !fsck_entry(sha1, type, buffer, size))
                                return 0;
                }
        }
        return -1;
}

static int fsck_dir(int i, char *path)
{
        DIR *dir = opendir(path);
        struct dirent *de;

        if (!dir) {
                fprintf(stderr, "missing sha1 directory '%s'", path);
                return -1;
        }

        while ((de = readdir(dir)) != NULL) {
                char name[100];
                int len = strlen(de->d_name);

                switch (len) {
                case 2:
                        if (de->d_name[1] != '.')
                                break;
                case 1:
                        if (de->d_name[0] != '.')
                                break;
                        continue;
                case 38:
                        sprintf(name, "%02x", i);
                        memcpy(name+2, de->d_name, len+1);
                        if (!fsck_name(name))
                                continue;
                }
                fprintf(stderr, "bad sha1 file: %s/%s\n", path, de->d_name);
        }
        closedir(dir);
        return 0;
}

int main(int argc, char **argv)
{
        int i;
        char *sha1_dir;

        if (argc != 1)
                usage("fsck-cache");
        sha1_dir = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
        for (i = 0; i < 256; i++) {
                static char dir[4096];
                sprintf(dir, "%s/%02x", sha1_dir, i);
                fsck_dir(i, dir);
        }
        check_connectivity();
        return 0;
}