#include "cache.h"

const char *prefix_path(const char *prefix, int len, const char *path)
{
        const char *orig = path;
        for (;;) {
                char c;
                if (*path != '.')
                        break;
                c = path[1];
                /* "." */
                if (!c) {
                        path++;
                        break;
                }
                /* "./" */
                if (c == '/') {
                        path += 2;
                        continue;
                }
                if (c != '.')
                        break;
                c = path[2];
                if (!c)
                        path += 2;
                else if (c == '/')
                        path += 3;
                else
                        break;
                /* ".." and "../" */
                /* Remove last component of the prefix */
                do {
                        if (!len)
                                die("'%s' is outside repository", orig);
                        len--;
                } while (len && prefix[len-1] != '/');
                continue;
        }
        if (len) {
                int speclen = strlen(path);
                char *n = xmalloc(speclen + len + 1);
        
                memcpy(n, prefix, len);
                memcpy(n + len, path, speclen+1);
                path = n;
        }
        return path;
}

/* 
 * Unlike prefix_path, this should be used if the named file does
 * not have to interact with index entry; i.e. name of a random file
 * on the filesystem.
 */
const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
{
        static char path[PATH_MAX];
        if (!pfx || !*pfx || arg[0] == '/')
                return arg;
        memcpy(path, pfx, pfx_len);
        strcpy(path + pfx_len, arg);
        return path;
}

/*
 * Verify a filename that we got as an argument for a pathspec
 * entry. Note that a filename that begins with "-" never verifies
 * as true, because even if such a filename were to exist, we want
 * it to be preceded by the "--" marker (or we want the user to
 * use a format like "./-filename")
 */
void verify_filename(const char *prefix, const char *arg)
{
        const char *name;
        struct stat st;

        if (*arg == '-')
                die("bad flag '%s' used after filename", arg);
        name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
        if (!lstat(name, &st))
                return;
        if (errno == ENOENT)
                die("ambiguous argument '%s': unknown revision or filename\n"
                    "Use '--' to separate filenames from revisions", arg);
        die("'%s': %s", arg, strerror(errno));
}

const char **get_pathspec(const char *prefix, const char **pathspec)
{
        const char *entry = *pathspec;
        const char **p;
        int prefixlen;

        if (!prefix && !entry)
                return NULL;

        if (!entry) {
                static const char *spec[2];
                spec[0] = prefix;
                spec[1] = NULL;
                return spec;
        }

        /* Otherwise we have to re-write the entries.. */
        p = pathspec;
        prefixlen = prefix ? strlen(prefix) : 0;
        do {
                *p = prefix_path(prefix, prefixlen, entry);
        } while ((entry = *++p) != NULL);
        return (const char **) pathspec;
}

/*
 * Test if it looks like we're at the top level git directory.
 * We want to see:
 *
 *  - either a .git/objects/ directory _or_ the proper
 *    GIT_OBJECT_DIRECTORY environment variable
 *  - a refs/ directory under ".git"
 *  - either a HEAD symlink or a HEAD file that is formatted as
 *    a proper "ref:".
 */
static int is_toplevel_directory(void)
{
        if (access(".git/refs/", X_OK) ||
            access(getenv(DB_ENVIRONMENT) ?
                   getenv(DB_ENVIRONMENT) : ".git/objects/", X_OK) ||
            validate_symref(".git/HEAD"))
                return 0;
        return 1;
}

const char *setup_git_directory_gently(int *nongit_ok)
{
        static char cwd[PATH_MAX+1];
        int len, offset;

        /*
         * If GIT_DIR is set explicitly, we're not going
         * to do any discovery, but we still do repository
         * validation.
         */
        if (getenv(GIT_DIR_ENVIRONMENT)) {
                char path[PATH_MAX];
                int len = strlen(getenv(GIT_DIR_ENVIRONMENT));
                if (sizeof(path) - 40 < len)
                        die("'$%s' too big", GIT_DIR_ENVIRONMENT);
                memcpy(path, getenv(GIT_DIR_ENVIRONMENT), len);
                
                strcpy(path + len, "/refs");
                if (access(path, X_OK))
                        goto bad_dir_environ;
                strcpy(path + len, "/HEAD");
                if (validate_symref(path))
                        goto bad_dir_environ;
                if (getenv(DB_ENVIRONMENT)) {
                        if (access(getenv(DB_ENVIRONMENT), X_OK))
                                goto bad_dir_environ;
                }
                else {
                        strcpy(path + len, "/objects");
                        if (access(path, X_OK))
                                goto bad_dir_environ;
                }
                return NULL;
        bad_dir_environ:
                path[len] = 0;
                die("Not a git repository: '%s'", path);
        }

        if (!getcwd(cwd, sizeof(cwd)) || cwd[0] != '/')
                die("Unable to read current working directory");

        offset = len = strlen(cwd);
        for (;;) {
                if (is_toplevel_directory())
                        break;
                chdir("..");
                do {
                        if (!offset) {
                                if (nongit_ok) {
                                        if (chdir(cwd))
                                                die("Cannot come back to cwd");
                                        *nongit_ok = 1;
                                        return NULL;
                                }
                                die("Not a git repository");
                        }
                } while (cwd[--offset] != '/');
        }

        if (offset == len)
                return NULL;

        /* Make "offset" point to past the '/', and add a '/' at the end */
        offset++;
        cwd[len++] = '/';
        cwd[len] = 0;
        return cwd + offset;
}

int check_repository_format_version(const char *var, const char *value)
{
       if (strcmp(var, "core.repositoryformatversion") == 0)
               repository_format_version = git_config_int(var, value);
        else if (strcmp(var, "core.sharedrepository") == 0)
                shared_repository = git_config_bool(var, value);
       return 0;
}

int check_repository_format(void)
{
        git_config(check_repository_format_version);
        if (GIT_REPO_VERSION < repository_format_version)
                die ("Expected git repo version <= %d, found %d",
                     GIT_REPO_VERSION, repository_format_version);
        return 0;
}

const char *setup_git_directory(void)
{
        const char *retval = setup_git_directory_gently(NULL);
        check_repository_format();
        return retval;
}