#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 struct strbuf sb = STRBUF_INIT;
        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:
         */
        struct strbuf cwd = STRBUF_INIT;

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

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

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

        strbuf_reset(&sb);
        strbuf_addstr(&sb, path);

        while (depth--) {
                if (!is_directory(sb.buf)) {
                        char *last_slash = find_last_dir_sep(sb.buf);
                        if (last_slash) {
                                last_elem = xstrdup(last_slash + 1);
                                strbuf_setlen(&sb, last_slash - sb.buf + 1);
                        } else {
                                last_elem = xmemdupz(sb.buf, sb.len);
                                strbuf_reset(&sb);
                        }
                }

                if (sb.len) {
                        if (!cwd.len && strbuf_getcwd(&cwd)) {
                                if (die_on_error)
                                        die_errno("Could not get current working directory");
                                else
                                        goto error_out;
                        }

                        if (chdir(sb.buf)) {
                                if (die_on_error)
                                        die_errno("Could not switch to '%s'",
                                                  sb.buf);
                                else
                                        goto error_out;
                        }
                }
                if (strbuf_getcwd(&sb)) {
                        if (die_on_error)
                                die_errno("Could not get current working directory");
                        else
                                goto error_out;
                }

                if (last_elem) {
                        if (sb.len && !is_dir_sep(sb.buf[sb.len - 1]))
                                strbuf_addch(&sb, '/');
                        strbuf_addstr(&sb, last_elem);
                        free(last_elem);
                        last_elem = NULL;
                }

                if (!lstat(sb.buf, &st) && S_ISLNK(st.st_mode)) {
                        struct strbuf next_sb = STRBUF_INIT;
                        ssize_t len = strbuf_readlink(&next_sb, sb.buf, 0);
                        if (len < 0) {
                                if (die_on_error)
                                        die_errno("Invalid symlink '%s'",
                                                  sb.buf);
                                else
                                        goto error_out;
                        }
                        strbuf_swap(&sb, &next_sb);
                        strbuf_release(&next_sb);
                } else
                        break;
        }

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

        return retval;
}

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

const char *real_path_if_valid(const char *path)
{
        return real_path_internal(path, 0);
}

/*
 * Use this to get an absolute path from a relative one. If you want
 * to resolve links, you should use real_path.
 */
const char *absolute_path(const char *path)
{
        static struct strbuf sb = STRBUF_INIT;
        strbuf_reset(&sb);
        strbuf_add_absolute_path(&sb, path);
        return sb.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 struct strbuf path = STRBUF_INIT;
#ifndef GIT_WINDOWS_NATIVE
        if (!pfx_len || is_absolute_path(arg))
                return arg;
        strbuf_reset(&path);
        strbuf_add(&path, pfx, pfx_len);
        strbuf_addstr(&path, arg);
#else
        /* don't add prefix to absolute paths, but still replace '\' by '/' */
        strbuf_reset(&path);
        if (is_absolute_path(arg))
                pfx_len = 0;
        else if (pfx_len)
                strbuf_add(&path, pfx, pfx_len);
        strbuf_addstr(&path, arg);
        convert_slashes(path.buf + pfx_len);
#endif
        return path.buf;
}