/*
 * "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 "builtin.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[] = {
        N_("git reset [--mixed | --soft | --hard | --merge | --keep] [-q] [<commit>]"),
        N_("git reset [-q] <commit> [--] <paths>..."),
        N_("git reset --patch [<commit>] [--] [<paths>...]"),
        NULL
};

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

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

static int reset_index(const unsigned char *sha1, int reset_type, int quiet)
{
        int nr = 1;
        struct tree_desc desc[2];
        struct tree *tree;
        struct unpack_trees_options opts;

        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;
        }

        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 (reset_type == MIXED || reset_type == HARD) {
                tree = parse_tree_indirect(sha1);
                prime_cache_tree(&active_cache_tree, tree);
        }

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

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

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

        for (i = 0; i < q->nr; i++) {
                struct diff_filespec *one = q->queue[i]->one;
                if (one->mode && !is_null_sha1(one->sha1)) {
                        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 read_from_tree(const char **pathspec, unsigned char *tree_sha1,
                          int refresh_flags)
{
        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
        int index_fd;
        struct diff_options opt;

        memset(&opt, 0, sizeof(opt));
        diff_tree_setup_paths(pathspec, &opt);
        opt.output_format = DIFF_FORMAT_CALLBACK;
        opt.format_callback = update_index_from_diff;

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

        return update_index_refresh(index_fd, lock, refresh_flags);
}

static void set_reflog_message(struct strbuf *sb, const char *action,
                               const char *rev)
{
        const char *rla = getenv("GIT_REFLOG_ACTION");

        strbuf_reset(sb);
        if (rla)
                strbuf_addf(sb, "%s: %s", rla, action);
        else if (rev)
                strbuf_addf(sb, "reset: moving to %s", rev);
        else
                strbuf_addf(sb, "reset: %s", action);
}

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]));

}

static const char **parse_args(const char **argv, const char *prefix, const char **rev_ret)
{
        const char *rev = "HEAD";
        unsigned char unused[20];
        /*
         * 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 points immediately after [-opts].
         */

        if (argv[0]) {
                if (!strcmp(argv[0], "--")) {
                        argv++; /* reset to HEAD, possibly with paths */
                } else if (argv[1] && !strcmp(argv[1], "--")) {
                        rev = argv[0];
                        argv += 2;
                }
                /*
                 * Otherwise, argv[0] could be either <rev> or <paths> and
                 * has to be unambiguous.
                 */
                else if (!get_sha1_committish(argv[0], unused)) {
                        /*
                         * Ok, argv[0] looks like a rev; it should not
                         * be a filename.
                         */
                        verify_non_filename(prefix, argv[0]);
                        rev = *argv++;
                } else {
                        /* Otherwise we treat this as a filename */
                        verify_filename(prefix, argv[0], 1);
                }
        }
        *rev_ret = rev;
        return argv[0] ? get_pathspec(prefix, argv) : NULL;
}

static int update_refs(const char *rev, const unsigned char *sha1)
{
        int update_ref_status;
        struct strbuf msg = STRBUF_INIT;
        unsigned char *orig = NULL, sha1_orig[20],
                *old_orig = NULL, sha1_old_orig[20];

        if (!get_sha1("ORIG_HEAD", sha1_old_orig))
                old_orig = sha1_old_orig;
        if (!get_sha1("HEAD", sha1_orig)) {
                orig = sha1_orig;
                set_reflog_message(&msg, "updating ORIG_HEAD", NULL);
                update_ref(msg.buf, "ORIG_HEAD", orig, old_orig, 0, MSG_ON_ERR);
        } else if (old_orig)
                delete_ref("ORIG_HEAD", old_orig, 0);
        set_reflog_message(&msg, "updating HEAD", rev);
        update_ref_status = update_ref(msg.buf, "HEAD", sha1, orig, 0, MSG_ON_ERR);
        strbuf_release(&msg);
        return update_ref_status;
}

int cmd_reset(int argc, const char **argv, const char *prefix)
{
        int reset_type = NONE, update_ref_status = 0, quiet = 0;
        int patch_mode = 0;
        const char *rev;
        unsigned char sha1[20];
        const char **pathspec = NULL;
        struct commit *commit;
        const struct option options[] = {
                OPT__QUIET(&quiet, N_("be quiet, only report errors")),
                OPT_SET_INT(0, "mixed", &reset_type,
                                                N_("reset HEAD and index"), MIXED),
                OPT_SET_INT(0, "soft", &reset_type, N_("reset only HEAD"), SOFT),
                OPT_SET_INT(0, "hard", &reset_type,
                                N_("reset HEAD, index and working tree"), HARD),
                OPT_SET_INT(0, "merge", &reset_type,
                                N_("reset HEAD, index and working tree"), MERGE),
                OPT_SET_INT(0, "keep", &reset_type,
                                N_("reset HEAD but keep local changes"), KEEP),
                OPT_BOOLEAN('p', "patch", &patch_mode, N_("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);
        pathspec = parse_args(argv, prefix, &rev);

        if (get_sha1_committish(rev, sha1))
                die(_("Failed to resolve '%s' as a valid ref."), rev);

        /*
         * NOTE: As "git reset $treeish -- $path" should be usable on
         * any tree-ish, this is not strictly correct. We are not
         * moving the HEAD to any commit; we are merely resetting the
         * entries in the index to that of a treeish.
         */
        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 run_add_interactive(rev, "--patch=reset", pathspec);
        }

        /* 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 (pathspec) {
                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]));
        }
        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]));

        if (pathspec)
                return read_from_tree(pathspec, sha1,
                                quiet ? REFRESH_QUIET : REFRESH_IN_PORCELAIN);

        /* 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 || reset_type == KEEP)
                die_if_unmerged_cache(reset_type);

        if (reset_type != SOFT) {
                struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
                int newfd = hold_locked_index(lock, 1);
                int err = reset_index(sha1, reset_type, quiet);
                if (reset_type == KEEP && !err)
                        err = reset_index(sha1, MIXED, quiet);
                if (err)
                        die(_("Could not reset index file to revision '%s'."), rev);
                if (write_cache(newfd, active_cache, active_nr) ||
                    commit_locked_index(lock))
                        die(_("Could not write new index file."));
        }

        /* Any resets update HEAD to the head being switched to,
         * saving the previous head in ORIG_HEAD before. */
        update_ref_status = update_refs(rev, sha1);

        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();

        return update_ref_status;
}