/*
 * Builtin "git replace"
 *
 * Copyright (c) 2008 Christian Couder <chriscool@tuxfamily.org>
 *
 * Based on builtin/tag.c by Kristian Høgsberg <krh@redhat.com>
 * and Carlos Rica <jasampler@gmail.com> that was itself based on
 * git-tag.sh and mktag.c by Linus Torvalds.
 */

#include "cache.h"
#include "builtin.h"
#include "refs.h"
#include "parse-options.h"
#include "run-command.h"
#include "tag.h"

static const char * const git_replace_usage[] = {
        N_("git replace [-f] <object> <replacement>"),
        N_("git replace [-f] --edit <object>"),
        N_("git replace [-f] --graft <commit> [<parent>...]"),
        N_("git replace -d <object>..."),
        N_("git replace [--format=<format>] [-l [<pattern>]]"),
        NULL
};

enum replace_format {
      REPLACE_FORMAT_SHORT,
      REPLACE_FORMAT_MEDIUM,
      REPLACE_FORMAT_LONG
};

struct show_data {
        const char *pattern;
        enum replace_format format;
};

static int show_reference(const char *refname, const unsigned char *sha1,
                          int flag, void *cb_data)
{
        struct show_data *data = cb_data;

        if (!wildmatch(data->pattern, refname, 0, NULL)) {
                if (data->format == REPLACE_FORMAT_SHORT)
                        printf("%s\n", refname);
                else if (data->format == REPLACE_FORMAT_MEDIUM)
                        printf("%s -> %s\n", refname, sha1_to_hex(sha1));
                else { /* data->format == REPLACE_FORMAT_LONG */
                        unsigned char object[20];
                        enum object_type obj_type, repl_type;

                        if (get_sha1(refname, object))
                                return error("Failed to resolve '%s' as a valid ref.", refname);

                        obj_type = sha1_object_info(object, NULL);
                        repl_type = sha1_object_info(sha1, NULL);

                        printf("%s (%s) -> %s (%s)\n", refname, typename(obj_type),
                               sha1_to_hex(sha1), typename(repl_type));
                }
        }

        return 0;
}

static int list_replace_refs(const char *pattern, const char *format)
{
        struct show_data data;

        if (pattern == NULL)
                pattern = "*";
        data.pattern = pattern;

        if (format == NULL || *format == '\0' || !strcmp(format, "short"))
                data.format = REPLACE_FORMAT_SHORT;
        else if (!strcmp(format, "medium"))
                data.format = REPLACE_FORMAT_MEDIUM;
        else if (!strcmp(format, "long"))
                data.format = REPLACE_FORMAT_LONG;
        else
                die("invalid replace format '%s'\n"
                    "valid formats are 'short', 'medium' and 'long'\n",
                    format);

        for_each_replace_ref(show_reference, (void *) &data);

        return 0;
}

typedef int (*each_replace_name_fn)(const char *name, const char *ref,
                                    const unsigned char *sha1);

static int for_each_replace_name(const char **argv, each_replace_name_fn fn)
{
        const char **p, *full_hex;
        char ref[PATH_MAX];
        int had_error = 0;
        unsigned char sha1[20];

        for (p = argv; *p; p++) {
                if (get_sha1(*p, sha1)) {
                        error("Failed to resolve '%s' as a valid ref.", *p);
                        had_error = 1;
                        continue;
                }
                full_hex = sha1_to_hex(sha1);
                snprintf(ref, sizeof(ref), "refs/replace/%s", full_hex);
                /* read_ref() may reuse the buffer */
                full_hex = ref + strlen("refs/replace/");
                if (read_ref(ref, sha1)) {
                        error("replace ref '%s' not found.", full_hex);
                        had_error = 1;
                        continue;
                }
                if (fn(full_hex, ref, sha1))
                        had_error = 1;
        }
        return had_error;
}

static int delete_replace_ref(const char *name, const char *ref,
                              const unsigned char *sha1)
{
        if (delete_ref(ref, sha1, 0))
                return 1;
        printf("Deleted replace ref '%s'\n", name);
        return 0;
}

static void check_ref_valid(unsigned char object[20],
                            unsigned char prev[20],
                            char *ref,
                            int ref_size,
                            int force)
{
        if (snprintf(ref, ref_size,
                     "refs/replace/%s",
                     sha1_to_hex(object)) > ref_size - 1)
                die("replace ref name too long: %.*s...", 50, ref);
        if (check_refname_format(ref, 0))
                die("'%s' is not a valid ref name.", ref);

        if (read_ref(ref, prev))
                hashclr(prev);
        else if (!force)
                die("replace ref '%s' already exists", ref);
}

static int replace_object_sha1(const char *object_ref,
                               unsigned char object[20],
                               const char *replace_ref,
                               unsigned char repl[20],
                               int force)
{
        unsigned char prev[20];
        enum object_type obj_type, repl_type;
        char ref[PATH_MAX];
        struct ref_lock *lock;

        obj_type = sha1_object_info(object, NULL);
        repl_type = sha1_object_info(repl, NULL);
        if (!force && obj_type != repl_type)
                die("Objects must be of the same type.\n"
                    "'%s' points to a replaced object of type '%s'\n"
                    "while '%s' points to a replacement object of type '%s'.",
                    object_ref, typename(obj_type),
                    replace_ref, typename(repl_type));

        check_ref_valid(object, prev, ref, sizeof(ref), force);

        lock = lock_any_ref_for_update(ref, prev, 0, NULL);
        if (!lock)
                die("%s: cannot lock the ref", ref);
        if (write_ref_sha1(lock, repl, NULL) < 0)
                die("%s: cannot update the ref", ref);

        return 0;
}

static int replace_object(const char *object_ref, const char *replace_ref, int force)
{
        unsigned char object[20], repl[20];

        if (get_sha1(object_ref, object))
                die("Failed to resolve '%s' as a valid ref.", object_ref);
        if (get_sha1(replace_ref, repl))
                die("Failed to resolve '%s' as a valid ref.", replace_ref);

        return replace_object_sha1(object_ref, object, replace_ref, repl, force);
}

/*
 * Write the contents of the object named by "sha1" to the file "filename",
 * pretty-printed for human editing based on its type.
 */
static void export_object(const unsigned char *sha1, const char *filename)
{
        const char *argv[] = { "--no-replace-objects", "cat-file", "-p", NULL, NULL };
        struct child_process cmd = { argv };
        int fd;

        fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
        if (fd < 0)
                die_errno("unable to open %s for writing", filename);

        argv[3] = sha1_to_hex(sha1);
        cmd.git_cmd = 1;
        cmd.out = fd;

        if (run_command(&cmd))
                die("cat-file reported failure");

        close(fd);
}

/*
 * Read a previously-exported (and possibly edited) object back from "filename",
 * interpreting it as "type", and writing the result to the object database.
 * The sha1 of the written object is returned via sha1.
 */
static void import_object(unsigned char *sha1, enum object_type type,
                          const char *filename)
{
        int fd;

        fd = open(filename, O_RDONLY);
        if (fd < 0)
                die_errno("unable to open %s for reading", filename);

        if (type == OBJ_TREE) {
                const char *argv[] = { "mktree", NULL };
                struct child_process cmd = { argv };
                struct strbuf result = STRBUF_INIT;

                cmd.argv = argv;
                cmd.git_cmd = 1;
                cmd.in = fd;
                cmd.out = -1;

                if (start_command(&cmd))
                        die("unable to spawn mktree");

                if (strbuf_read(&result, cmd.out, 41) < 0)
                        die_errno("unable to read from mktree");
                close(cmd.out);

                if (finish_command(&cmd))
                        die("mktree reported failure");
                if (get_sha1_hex(result.buf, sha1) < 0)
                        die("mktree did not return an object name");

                strbuf_release(&result);
        } else {
                struct stat st;
                int flags = HASH_FORMAT_CHECK | HASH_WRITE_OBJECT;

                if (fstat(fd, &st) < 0)
                        die_errno("unable to fstat %s", filename);
                if (index_fd(sha1, fd, &st, type, NULL, flags) < 0)
                        die("unable to write object to database");
                /* index_fd close()s fd for us */
        }

        /*
         * No need to close(fd) here; both run-command and index-fd
         * will have done it for us.
         */
}

static int edit_and_replace(const char *object_ref, int force)
{
        char *tmpfile = git_pathdup("REPLACE_EDITOBJ");
        enum object_type type;
        unsigned char old[20], new[20], prev[20];
        char ref[PATH_MAX];

        if (get_sha1(object_ref, old) < 0)
                die("Not a valid object name: '%s'", object_ref);

        type = sha1_object_info(old, NULL);
        if (type < 0)
                die("unable to get object type for %s", sha1_to_hex(old));

        check_ref_valid(old, prev, ref, sizeof(ref), force);

        export_object(old, tmpfile);
        if (launch_editor(tmpfile, NULL, NULL) < 0)
                die("editing object file failed");
        import_object(new, type, tmpfile);

        free(tmpfile);

        if (!hashcmp(old, new))
                return error("new object is the same as the old one: '%s'", sha1_to_hex(old));

        return replace_object_sha1(object_ref, old, "replacement", new, force);
}

static void replace_parents(struct strbuf *buf, int argc, const char **argv)
{
        struct strbuf new_parents = STRBUF_INIT;
        const char *parent_start, *parent_end;
        int i;

        /* find existing parents */
        parent_start = buf->buf;
        parent_start += 46; /* "tree " + "hex sha1" + "\n" */
        parent_end = parent_start;

        while (starts_with(parent_end, "parent "))
                parent_end += 48; /* "parent " + "hex sha1" + "\n" */

        /* prepare new parents */
        for (i = 0; i < argc; i++) {
                unsigned char sha1[20];
                if (get_sha1(argv[i], sha1) < 0)
                        die(_("Not a valid object name: '%s'"), argv[i]);
                lookup_commit_or_die(sha1, argv[i]);
                strbuf_addf(&new_parents, "parent %s\n", sha1_to_hex(sha1));
        }

        /* replace existing parents with new ones */
        strbuf_splice(buf, parent_start - buf->buf, parent_end - parent_start,
                      new_parents.buf, new_parents.len);

        strbuf_release(&new_parents);
}

struct check_mergetag_data {
        int argc;
        const char **argv;
};

static void check_one_mergetag(struct commit *commit,
                               struct commit_extra_header *extra,
                               void *data)
{
        struct check_mergetag_data *mergetag_data = (struct check_mergetag_data *)data;
        const char *ref = mergetag_data->argv[0];
        unsigned char tag_sha1[20];
        struct tag *tag;
        int i;

        hash_sha1_file(extra->value, extra->len, typename(OBJ_TAG), tag_sha1);
        tag = lookup_tag(tag_sha1);
        if (!tag)
                die(_("bad mergetag in commit '%s'"), ref);
        if (parse_tag_buffer(tag, extra->value, extra->len))
                die(_("malformed mergetag in commit '%s'"), ref);

        /* iterate over new parents */
        for (i = 1; i < mergetag_data->argc; i++) {
                unsigned char sha1[20];
                if (get_sha1(mergetag_data->argv[i], sha1) < 0)
                        die(_("Not a valid object name: '%s'"), mergetag_data->argv[i]);
                if (!hashcmp(tag->tagged->sha1, sha1))
                        return; /* found */
        }

        die(_("original commit '%s' contains mergetag '%s' that is discarded; "
              "use --edit instead of --graft"), ref, sha1_to_hex(tag_sha1));
}

static void check_mergetags(struct commit *commit, int argc, const char **argv)
{
        struct check_mergetag_data mergetag_data;

        mergetag_data.argc = argc;
        mergetag_data.argv = argv;
        for_each_mergetag(check_one_mergetag, commit, &mergetag_data);
}

static int create_graft(int argc, const char **argv, int force)
{
        unsigned char old[20], new[20];
        const char *old_ref = argv[0];
        struct commit *commit;
        struct strbuf buf = STRBUF_INIT;
        const char *buffer;
        unsigned long size;

        if (get_sha1(old_ref, old) < 0)
                die(_("Not a valid object name: '%s'"), old_ref);
        commit = lookup_commit_or_die(old, old_ref);

        buffer = get_commit_buffer(commit, &size);
        strbuf_add(&buf, buffer, size);
        unuse_commit_buffer(commit, buffer);

        replace_parents(&buf, argc - 1, &argv[1]);

        if (remove_signature(&buf)) {
                warning(_("the original commit '%s' has a gpg signature."), old_ref);
                warning(_("the signature will be removed in the replacement commit!"));
        }

        check_mergetags(commit, argc, argv);

        if (write_sha1_file(buf.buf, buf.len, commit_type, new))
                die(_("could not write replacement commit for: '%s'"), old_ref);

        strbuf_release(&buf);

        if (!hashcmp(old, new))
                return error("new commit is the same as the old one: '%s'", sha1_to_hex(old));

        return replace_object_sha1(old_ref, old, "replacement", new, force);
}

int cmd_replace(int argc, const char **argv, const char *prefix)
{
        int force = 0;
        const char *format = NULL;
        enum {
                MODE_UNSPECIFIED = 0,
                MODE_LIST,
                MODE_DELETE,
                MODE_EDIT,
                MODE_GRAFT,
                MODE_REPLACE
        } cmdmode = MODE_UNSPECIFIED;
        struct option options[] = {
                OPT_CMDMODE('l', "list", &cmdmode, N_("list replace refs"), MODE_LIST),
                OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
                OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),
                OPT_CMDMODE('g', "graft", &cmdmode, N_("change a commit's parents"), MODE_GRAFT),
                OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
                OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
                OPT_END()
        };

        check_replace_refs = 0;

        argc = parse_options(argc, argv, prefix, options, git_replace_usage, 0);

        if (!cmdmode)
                cmdmode = argc ? MODE_REPLACE : MODE_LIST;

        if (format && cmdmode != MODE_LIST)
                usage_msg_opt("--format cannot be used when not listing",
                              git_replace_usage, options);

        if (force &&
            cmdmode != MODE_REPLACE &&
            cmdmode != MODE_EDIT &&
            cmdmode != MODE_GRAFT)
                usage_msg_opt("-f only makes sense when writing a replacement",
                              git_replace_usage, options);

        switch (cmdmode) {
        case MODE_DELETE:
                if (argc < 1)
                        usage_msg_opt("-d needs at least one argument",
                                      git_replace_usage, options);
                return for_each_replace_name(argv, delete_replace_ref);

        case MODE_REPLACE:
                if (argc != 2)
                        usage_msg_opt("bad number of arguments",
                                      git_replace_usage, options);
                return replace_object(argv[0], argv[1], force);

        case MODE_EDIT:
                if (argc != 1)
                        usage_msg_opt("-e needs exactly one argument",
                                      git_replace_usage, options);
                return edit_and_replace(argv[0], force);

        case MODE_GRAFT:
                if (argc < 1)
                        usage_msg_opt("-g needs at least one argument",
                                      git_replace_usage, options);
                return create_graft(argc, argv, force);

        case MODE_LIST:
                if (argc > 1)
                        usage_msg_opt("only one pattern can be given with -l",
                                      git_replace_usage, options);
                return list_replace_refs(argv[0], format);

        default:
                die("BUG: invalid cmdmode %d", (int)cmdmode);
        }
}