/*
 * "git reset" builtin command
 *
 * Copyright (c) 2007 Carlos Rica
 *
 * Based on git-reset.sh, which is
 *
 * Copyright (c) 2005, 2006 Linus Torvalds and Junio C Hamano
 */
#include "cache.h"
#include "tag.h"
#include "object.h"
#include "commit.h"
#include "run-command.h"
#include "refs.h"
#include "diff.h"
#include "diffcore.h"
#include "tree.h"
#include "branch.h"
#include "parse-options.h"
#include "unpack-trees.h"
#include "cache-tree.h"

static const char * const git_reset_usage[] = {
        "git reset [--mixed | --soft | --hard | --merge | --keep] [-q] [<commit>]",
        "git reset [-q] <commit> [--] <paths>...",
        "git reset --patch [<commit>] [--] [<paths>...]",
        NULL
};

enum reset_type { MIXED, SOFT, HARD, MERGE, KEEP, NONE };
static const char *reset_type_names[] = {
        "mixed", "soft", "hard", "merge", "keep", NULL
};

static char *args_to_str(const char **argv)
{
        char *buf = NULL;
        unsigned long len, space = 0, nr = 0;

        for (; *argv; argv++) {
                len = strlen(*argv);
                ALLOC_GROW(buf, nr + 1 + len, space);
                if (nr)
                        buf[nr++] = ' ';
                memcpy(buf + nr, *argv, len);
                nr += len;
        }
        ALLOC_GROW(buf, nr + 1, space);
        buf[nr] = '\0';

        return buf;
}

static inline int is_merge(void)
{
        return !access(git_path("MERGE_HEAD"), F_OK);
}

static int reset_index_file(const unsigned char *sha1, int reset_type, int quiet)
{
        int nr = 1;
        int newfd;
        struct tree_desc desc[2];
        struct unpack_trees_options opts;
        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));

        memset(&opts, 0, sizeof(opts));
        opts.head_idx = 1;
        opts.src_index = &the_index;
        opts.dst_index = &the_index;
        opts.fn = oneway_merge;
        opts.merge = 1;
        if (!quiet)
                opts.verbose_update = 1;
        switch (reset_type) {
        case KEEP:
        case MERGE:
                opts.update = 1;
                break;
        case HARD:
                opts.update = 1;
                /* fallthrough */
        default:
                opts.reset = 1;
        }

        newfd = hold_locked_index(lock, 1);

        read_cache_unmerged();

        if (reset_type == KEEP) {
                unsigned char head_sha1[20];
                if (get_sha1("HEAD", head_sha1))
                        return error("You do not have a valid HEAD.");
                if (!fill_tree_descriptor(desc, head_sha1))
                        return error("Failed to find tree of HEAD.");
                nr++;
                opts.fn = twoway_merge;
        }

        if (!fill_tree_descriptor(desc + nr - 1, sha1))
                return error("Failed to find tree of %s.", sha1_to_hex(sha1));
        if (unpack_trees(nr, desc, &opts))
                return -1;
        if (write_cache(newfd, active_cache, active_nr) ||
            commit_locked_index(lock))
                return error("Could not write new index file.");

        return 0;
}

static void print_new_head_line(struct commit *commit)
{
        const char *hex, *body;

        hex = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
        printf("HEAD is now at %s", hex);
        body = strstr(commit->buffer, "\n\n");
        if (body) {
                const char *eol;
                size_t len;
                body += 2;
                eol = strchr(body, '\n');
                len = eol ? eol - body : strlen(body);
                printf(" %.*s\n", (int) len, body);
        }
        else
                printf("\n");
}

static int update_index_refresh(int fd, struct lock_file *index_lock, int flags)
{
        int result;

        if (!index_lock) {
                index_lock = xcalloc(1, sizeof(struct lock_file));
                fd = hold_locked_index(index_lock, 1);
        }

        if (read_cache() < 0)
                return error("Could not read index");

        result = refresh_index(&the_index, (flags), NULL, NULL,
                               "Unstaged changes after reset:") ? 1 : 0;
        if (write_cache(fd, active_cache, active_nr) ||
                        commit_locked_index(index_lock))
                return error ("Could not refresh index");
        return result;
}

static void update_index_from_diff(struct diff_queue_struct *q,
                struct diff_options *opt, void *data)
{
        int i;
        int *discard_flag = data;

        /* do_diff_cache() mangled the index */
        discard_cache();
        *discard_flag = 1;
        read_cache();

        for (i = 0; i < q->nr; i++) {
                struct diff_filespec *one = q->queue[i]->one;
                if (one->mode) {
                        struct cache_entry *ce;
                        ce = make_cache_entry(one->mode, one->sha1, one->path,
                                0, 0);
                        if (!ce)
                                die("make_cache_entry failed for path '%s'",
                                    one->path);
                        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD |
                                ADD_CACHE_OK_TO_REPLACE);
                } else
                        remove_file_from_cache(one->path);
        }
}

static int interactive_reset(const char *revision, const char **argv,
                             const char *prefix)
{
        const char **pathspec = NULL;

        if (*argv)
                pathspec = get_pathspec(prefix, argv);

        return run_add_interactive(revision, "--patch=reset", pathspec);
}

static int read_from_tree(const char *prefix, const char **argv,
                unsigned char *tree_sha1, int refresh_flags)
{
        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
        int index_fd, index_was_discarded = 0;
        struct diff_options opt;

        memset(&opt, 0, sizeof(opt));
        diff_tree_setup_paths(get_pathspec(prefix, (const char **)argv), &opt);
        opt.output_format = DIFF_FORMAT_CALLBACK;
        opt.format_callback = update_index_from_diff;
        opt.format_callback_data = &index_was_discarded;

        index_fd = hold_locked_index(lock, 1);
        index_was_discarded = 0;
        read_cache();
        if (do_diff_cache(tree_sha1, &opt))
                return 1;
        diffcore_std(&opt);
        diff_flush(&opt);
        diff_tree_release_paths(&opt);

        if (!index_was_discarded)
                /* The index is still clobbered from do_diff_cache() */
                discard_cache();
        return update_index_refresh(index_fd, lock, refresh_flags);
}

static void prepend_reflog_action(const char *action, char *buf, size_t size)
{
        const char *sep = ": ";
        const char *rla = getenv("GIT_REFLOG_ACTION");
        if (!rla)
                rla = sep = "";
        if (snprintf(buf, size, "%s%s%s", rla, sep, action) >= size)
                warning("Reflog action message too long: %.*s...", 50, buf);
}

static void die_if_unmerged_cache(int reset_type)
{
        if (is_merge() || read_cache() < 0 || unmerged_cache())
                die("Cannot do a %s reset in the middle of a merge.",
                    reset_type_names[reset_type]);

}

int cmd_reset(int argc, const char **argv, const char *prefix)
{
        int i = 0, reset_type = NONE, update_ref_status = 0, quiet = 0;
        int patch_mode = 0;
        const char *rev = "HEAD";
        unsigned char sha1[20], *orig = NULL, sha1_orig[20],
                                *old_orig = NULL, sha1_old_orig[20];
        struct commit *commit;
        char *reflog_action, msg[1024];
        const struct option options[] = {
                OPT__QUIET(&quiet),
                OPT_SET_INT(0, "mixed", &reset_type,
                                                "reset HEAD and index", MIXED),
                OPT_SET_INT(0, "soft", &reset_type, "reset only HEAD", SOFT),
                OPT_SET_INT(0, "hard", &reset_type,
                                "reset HEAD, index and working tree", HARD),
                OPT_SET_INT(0, "merge", &reset_type,
                                "reset HEAD, index and working tree", MERGE),
                OPT_SET_INT(0, "keep", &reset_type,
                                "reset HEAD but keep local changes", KEEP),
                OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
                OPT_END()
        };

        git_config(git_default_config, NULL);

        argc = parse_options(argc, argv, prefix, options, git_reset_usage,
                                                PARSE_OPT_KEEP_DASHDASH);
        reflog_action = args_to_str(argv);
        setenv("GIT_REFLOG_ACTION", reflog_action, 0);

        /*
         * Possible arguments are:
         *
         * git reset [-opts] <rev> <paths>...
         * git reset [-opts] <rev> -- <paths>...
         * git reset [-opts] -- <paths>...
         * git reset [-opts] <paths>...
         *
         * At this point, argv[i] points immediately after [-opts].
         */

        if (i < argc) {
                if (!strcmp(argv[i], "--")) {
                        i++; /* reset to HEAD, possibly with paths */
                } else if (i + 1 < argc && !strcmp(argv[i+1], "--")) {
                        rev = argv[i];
                        i += 2;
                }
                /*
                 * Otherwise, argv[i] could be either <rev> or <paths> and
                 * has to be unambiguous.
                 */
                else if (!get_sha1(argv[i], sha1)) {
                        /*
                         * Ok, argv[i] looks like a rev; it should not
                         * be a filename.
                         */
                        verify_non_filename(prefix, argv[i]);
                        rev = argv[i++];
                } else {
                        /* Otherwise we treat this as a filename */
                        verify_filename(prefix, argv[i]);
                }
        }

        if (get_sha1(rev, sha1))
                die("Failed to resolve '%s' as a valid ref.", rev);

        commit = lookup_commit_reference(sha1);
        if (!commit)
                die("Could not parse object '%s'.", rev);
        hashcpy(sha1, commit->object.sha1);

        if (patch_mode) {
                if (reset_type != NONE)
                        die("--patch is incompatible with --{hard,mixed,soft}");
                return interactive_reset(rev, argv + i, prefix);
        }

        /* git reset tree [--] paths... can be used to
         * load chosen paths from the tree into the index without
         * affecting the working tree nor HEAD. */
        if (i < argc) {
                if (reset_type == MIXED)
                        warning("--mixed with paths is deprecated; use 'git reset -- <paths>' instead.");
                else if (reset_type != NONE)
                        die("Cannot do %s reset with paths.",
                                        reset_type_names[reset_type]);
                return read_from_tree(prefix, argv + i, sha1,
                                quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
        }
        if (reset_type == NONE)
                reset_type = MIXED; /* by default */

        if (reset_type != SOFT && reset_type != MIXED)
                setup_work_tree();

        if (reset_type == MIXED && is_bare_repository())
                die("%s reset is not allowed in a bare repository",
                    reset_type_names[reset_type]);

        /* Soft reset does not touch the index file nor the working tree
         * at all, but requires them in a good order.  Other resets reset
         * the index file to the tree object we are switching to. */
        if (reset_type == SOFT)
                die_if_unmerged_cache(reset_type);
        else {
                int err;
                if (reset_type == KEEP)
                        die_if_unmerged_cache(reset_type);
                err = reset_index_file(sha1, reset_type, quiet);
                if (reset_type == KEEP)
                        err = err || reset_index_file(sha1, MIXED, quiet);
                if (err)
                        die("Could not reset index file to revision '%s'.", rev);
        }

        /* Any resets update HEAD to the head being switched to,
         * saving the previous head in ORIG_HEAD before. */
        if (!get_sha1("ORIG_HEAD", sha1_old_orig))
                old_orig = sha1_old_orig;
        if (!get_sha1("HEAD", sha1_orig)) {
                orig = sha1_orig;
                prepend_reflog_action("updating ORIG_HEAD", msg, sizeof(msg));
                update_ref(msg, "ORIG_HEAD", orig, old_orig, 0, MSG_ON_ERR);
        }
        else if (old_orig)
                delete_ref("ORIG_HEAD", old_orig, 0);
        prepend_reflog_action("updating HEAD", msg, sizeof(msg));
        update_ref_status = update_ref(msg, "HEAD", sha1, orig, 0, MSG_ON_ERR);

        switch (reset_type) {
        case HARD:
                if (!update_ref_status && !quiet)
                        print_new_head_line(commit);
                break;
        case SOFT: /* Nothing else to do. */
                break;
        case MIXED: /* Report what has not been updated. */
                update_index_refresh(0, NULL,
                                quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);
                break;
        }

        remove_branch_state();

        free(reflog_action);

        return update_ref_status;
}