#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));
}

/* removes the last path component from 'path' except if 'path' is root */
static void strip_last_component(struct strbuf *path)
{
        size_t offset = offset_1st_component(path->buf);
        size_t len = path->len;

        /* Find start of the last component */
        while (offset < len && !is_dir_sep(path->buf[len - 1]))
                len--;
        /* Skip sequences of multiple path-separators */
        while (offset < len && is_dir_sep(path->buf[len - 1]))
                len--;

        strbuf_setlen(path, len);
}

/* get (and remove) the next component in 'remaining' and place it in 'next' */
static void get_next_component(struct strbuf *next, struct strbuf *remaining)
{
        char *start = NULL;
        char *end = NULL;

        strbuf_reset(next);

        /* look for the next component */
        /* Skip sequences of multiple path-separators */
        for (start = remaining->buf; is_dir_sep(*start); start++)
                ; /* nothing */
        /* Find end of the path component */
        for (end = start; *end && !is_dir_sep(*end); end++)
                ; /* nothing */

        strbuf_add(next, start, end - start);
        /* remove the component from 'remaining' */
        strbuf_remove(remaining, 0, end - remaining->buf);
}

/* We allow "recursive" symbolic links. Only within reason, though. */
#define MAXSYMLINKS 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 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 resolved = STRBUF_INIT;
        struct strbuf remaining = STRBUF_INIT;
        struct strbuf next = STRBUF_INIT;
        struct strbuf symlink = STRBUF_INIT;
        char *retval = NULL;
        int num_symlinks = 0;
        struct stat st;

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

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

        strbuf_reset(&resolved);

        if (is_absolute_path(path)) {
                /* absolute path; start with only root as being resolved */
                int offset = offset_1st_component(path);
                strbuf_add(&resolved, path, offset);
                strbuf_addstr(&remaining, path + offset);
        } else {
                /* relative path; can use CWD as the initial resolved path */
                if (strbuf_getcwd(&resolved)) {
                        if (die_on_error)
                                die_errno("unable to get current working directory");
                        else
                                goto error_out;
                }
                strbuf_addstr(&remaining, path);
        }

        /* Iterate over the remaining path components */
        while (remaining.len > 0) {
                get_next_component(&next, &remaining);

                if (next.len == 0) {
                        continue; /* empty component */
                } else if (next.len == 1 && !strcmp(next.buf, ".")) {
                        continue; /* '.' component */
                } else if (next.len == 2 && !strcmp(next.buf, "..")) {
                        /* '..' component; strip the last path component */
                        strip_last_component(&resolved);
                        continue;
                }

                /* append the next component and resolve resultant path */
                if (!is_dir_sep(resolved.buf[resolved.len - 1]))
                        strbuf_addch(&resolved, '/');
                strbuf_addbuf(&resolved, &next);

                if (lstat(resolved.buf, &st)) {
                        /* error out unless this was the last component */
                        if (errno != ENOENT || remaining.len) {
                                if (die_on_error)
                                        die_errno("Invalid path '%s'",
                                                  resolved.buf);
                                else
                                        goto error_out;
                        }
                } else if (S_ISLNK(st.st_mode)) {
                        ssize_t len;
                        strbuf_reset(&symlink);

                        if (num_symlinks++ > MAXSYMLINKS) {
                                if (die_on_error)
                                        die("More than %d nested symlinks "
                                            "on path '%s'", MAXSYMLINKS, path);
                                else
                                        goto error_out;
                        }

                        len = strbuf_readlink(&symlink, resolved.buf,
                                              st.st_size);
                        if (len < 0) {
                                if (die_on_error)
                                        die_errno("Invalid symlink '%s'",
                                                  resolved.buf);
                                else
                                        goto error_out;
                        }

                        if (is_absolute_path(symlink.buf)) {
                                /* absolute symlink; set resolved to root */
                                int offset = offset_1st_component(symlink.buf);
                                strbuf_reset(&resolved);
                                strbuf_add(&resolved, symlink.buf, offset);
                                strbuf_remove(&symlink, 0, offset);
                        } else {
                                /*
                                 * relative symlink
                                 * strip off the last component since it will
                                 * be replaced with the contents of the symlink
                                 */
                                strip_last_component(&resolved);
                        }

                        /*
                         * if there are still remaining components to resolve
                         * then append them to symlink
                         */
                        if (remaining.len) {
                                strbuf_addch(&symlink, '/');
                                strbuf_addbuf(&symlink, &remaining);
                        }

                        /*
                         * use the symlink as the remaining components that
                         * need to be resloved
                         */
                        strbuf_swap(&symlink, &remaining);
                }
        }

        retval = resolved.buf;

error_out:
        strbuf_release(&remaining);
        strbuf_release(&next);
        strbuf_release(&symlink);

        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;
}