/*
 * "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"

static const char builtin_reset_usage[] =
"git-reset [--mixed | --soft | --hard] [-q] [<commit-ish>] [ [--] <paths>...]";

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 is_hard_reset)
{
        int i = 0;
        const char *args[6];

        args[i++] = "read-tree";
        args[i++] = "-v";
        args[i++] = "--reset";
        if (is_hard_reset)
                args[i++] = "-u";
        args[i++] = sha1_to_hex(sha1);
        args[i] = NULL;

        return run_command_v_opt(args, RUN_GIT_CMD);
}

static void print_new_head_line(struct commit *commit)
{
        const char *hex, *dots = "...", *body;

        hex = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
        if (!hex) {
                hex = sha1_to_hex(commit->object.sha1);
                dots = "";
        }
        printf("HEAD is now at %s%s", hex, dots);
        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 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_cache(0) ? 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);
                        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 *prefix, const char **argv,
                unsigned char *tree_sha1)
{
        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);
}

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);
}

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

int cmd_reset(int argc, const char **argv, const char *prefix)
{
        int i = 1, reset_type = NONE, update_ref_status = 0, quiet = 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];

        git_config(git_default_config);

        reflog_action = args_to_str(argv);
        setenv("GIT_REFLOG_ACTION", reflog_action, 0);

        while (i < argc) {
                if (!strcmp(argv[i], "--mixed")) {
                        reset_type = MIXED;
                        i++;
                }
                else if (!strcmp(argv[i], "--soft")) {
                        reset_type = SOFT;
                        i++;
                }
                else if (!strcmp(argv[i], "--hard")) {
                        reset_type = HARD;
                        i++;
                }
                else if (!strcmp(argv[i], "-q")) {
                        quiet = 1;
                        i++;
                }
                else
                        break;
        }

        if (i < argc && argv[i][0] != '-')
                rev = 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 (i < argc && !strcmp(argv[i], "--"))
                i++;
        else if (i < argc && argv[i][0] == '-')
                usage(builtin_reset_usage);

        /* 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 option is deprecated with paths.");
                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);
        }
        if (reset_type == NONE)
                reset_type = MIXED; /* by default */

        if (reset_type == HARD && is_bare_repository())
                die("hard reset makes no sense in a bare repository");

        /* 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) {
                if (is_merge() || read_cache() < 0 || unmerged_cache())
                        die("Cannot do a soft reset in the middle of a merge.");
        }
        else if (reset_index_file(sha1, (reset_type == HARD)))
                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);
        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);
                break;
        }

        unlink(git_path("MERGE_HEAD"));
        unlink(git_path("rr-cache/MERGE_RR"));
        unlink(git_path("MERGE_MSG"));
        unlink(git_path("SQUASH_MSG"));

        free(reflog_action);

        return update_ref_status;
}