#include "cache.h"

/*
 * Do not use this for inspecting *tracked* content.  When path is a
 * symlink to a directory, we do not want to say it is a directory when
 * dealing with tracked content in the working tree.
 */
int is_directory(const char *path)
{
        struct stat st;
        return (!stat(path, &st) && S_ISDIR(st.st_mode));
}

/* We allow "recursive" symbolic links. Only within reason, though. */
#define MAXDEPTH 5

/*
 * Return the real path (i.e., absolute path, with symlinks resolved
 * and extra slashes removed) equivalent to the specified path.  (If
 * you want an absolute path but don't mind links, use
 * absolute_path().)  The return value is a pointer to a static
 * buffer.
 *
 * The input and all intermediate paths must be shorter than MAX_PATH.
 * The directory part of path (i.e., everything up to the last
 * dir_sep) must denote a valid, existing directory, but the last
 * component need not exist.  If die_on_error is set, then die with an
 * informative error message if there is a problem.  Otherwise, return
 * NULL on errors (without generating any output).
 *
 * If path is our buffer, then return path, as it's already what the
 * user wants.
 */
static const char *real_path_internal(const char *path, int die_on_error)
{
        static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];
        char *retval = NULL;

        /*
         * If we have to temporarily chdir(), store the original CWD
         * here so that we can chdir() back to it at the end of the
         * function:
         */
        char cwd[1024] = "";

        int buf_index = 1;

        int depth = MAXDEPTH;
        char *last_elem = NULL;
        struct stat st;

        /* We've already done it */
        if (path == buf || path == next_buf)
                return path;

        if (!*path) {
                if (die_on_error)
                        die("The empty string is not a valid path");
                else
                        goto error_out;
        }

        if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX) {
                if (die_on_error)
                        die("Too long path: %.*s", 60, path);
                else
                        goto error_out;
        }

        while (depth--) {
                if (!is_directory(buf)) {
                        char *last_slash = find_last_dir_sep(buf);
                        if (last_slash) {
                                last_elem = xstrdup(last_slash + 1);
                                last_slash[1] = '\0';
                        } else {
                                last_elem = xstrdup(buf);
                                *buf = '\0';
                        }
                }

                if (*buf) {
                        if (!*cwd && !getcwd(cwd, sizeof(cwd))) {
                                if (die_on_error)
                                        die_errno("Could not get current working directory");
                                else
                                        goto error_out;
                        }

                        if (chdir(buf)) {
                                if (die_on_error)
                                        die_errno("Could not switch to '%s'", buf);
                                else
                                        goto error_out;
                        }
                }
                if (!getcwd(buf, PATH_MAX)) {
                        if (die_on_error)
                                die_errno("Could not get current working directory");
                        else
                                goto error_out;
                }

                if (last_elem) {
                        size_t len = strlen(buf);
                        if (len + strlen(last_elem) + 2 > PATH_MAX) {
                                if (die_on_error)
                                        die("Too long path name: '%s/%s'",
                                            buf, last_elem);
                                else
                                        goto error_out;
                        }
                        if (len && !is_dir_sep(buf[len-1]))
                                buf[len++] = '/';
                        strcpy(buf + len, last_elem);
                        free(last_elem);
                        last_elem = NULL;
                }

                if (!lstat(buf, &st) && S_ISLNK(st.st_mode)) {
                        ssize_t len = readlink(buf, next_buf, PATH_MAX);
                        if (len < 0) {
                                if (die_on_error)
                                        die_errno("Invalid symlink '%s'", buf);
                                else
                                        goto error_out;
                        }
                        if (PATH_MAX <= len) {
                                if (die_on_error)
                                        die("symbolic link too long: %s", buf);
                                else
                                        goto error_out;
                        }
                        next_buf[len] = '\0';
                        buf = next_buf;
                        buf_index = 1 - buf_index;
                        next_buf = bufs[buf_index];
                } else
                        break;
        }

        retval = buf;
error_out:
        free(last_elem);
        if (*cwd && chdir(cwd))
                die_errno ("Could not change back to '%s'", cwd);

        return retval;
}

const char *real_path(const char *path)
{
        return real_path_internal(path, 1);
}

static const char *get_pwd_cwd(void)
{
        static char cwd[PATH_MAX + 1];
        char *pwd;
        struct stat cwd_stat, pwd_stat;
        if (getcwd(cwd, PATH_MAX) == NULL)
                return NULL;
        pwd = getenv("PWD");
        if (pwd && strcmp(pwd, cwd)) {
                stat(cwd, &cwd_stat);
                if ((cwd_stat.st_dev || cwd_stat.st_ino) &&
                    !stat(pwd, &pwd_stat) &&
                    pwd_stat.st_dev == cwd_stat.st_dev &&
                    pwd_stat.st_ino == cwd_stat.st_ino) {
                        strlcpy(cwd, pwd, PATH_MAX);
                }
        }
        return cwd;
}

/*
 * Use this to get an absolute path from a relative one. If you want
 * to resolve links, you should use real_path.
 *
 * If the path is already absolute, then return path. As the user is
 * never meant to free the return value, we're safe.
 */
const char *absolute_path(const char *path)
{
        static char buf[PATH_MAX + 1];

        if (!*path) {
                die("The empty string is not a valid path");
        } else if (is_absolute_path(path)) {
                if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
                        die("Too long path: %.*s", 60, path);
        } else {
                size_t len;
                const char *fmt;
                const char *cwd = get_pwd_cwd();
                if (!cwd)
                        die_errno("Cannot determine the current working directory");
                len = strlen(cwd);
                fmt = (len > 0 && is_dir_sep(cwd[len-1])) ? "%s%s" : "%s/%s";
                if (snprintf(buf, PATH_MAX, fmt, cwd, path) >= PATH_MAX)
                        die("Too long path: %.*s", 60, path);
        }
        return buf;
}

/*
 * 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];
#ifndef WIN32
        if (!pfx_len || is_absolute_path(arg))
                return arg;
        memcpy(path, pfx, pfx_len);
        strcpy(path + pfx_len, arg);
#else
        char *p;
        /* don't add prefix to absolute paths, but still replace '\' by '/' */
        if (is_absolute_path(arg))
                pfx_len = 0;
        else if (pfx_len)
                memcpy(path, pfx, pfx_len);
        strcpy(path + pfx_len, arg);
        for (p = path + pfx_len; *p; p++)
                if (*p == '\\')
                        *p = '/';
#endif
        return path;
}