#include "cache.h"
#include "builtin.h"
#include "object.h"
#include "commit.h"
#include "tag.h"
#include "wt-status.h"
#include "run-command.h"
#include "exec_cmd.h"
#include "utf8.h"
#include "parse-options.h"
#include "cache-tree.h"

/*
 * This implements the builtins revert and cherry-pick.
 *
 * Copyright (c) 2007 Johannes E. Schindelin
 *
 * Based on git-revert.sh, which is
 *
 * Copyright (c) 2005 Linus Torvalds
 * Copyright (c) 2005 Junio C Hamano
 */

static const char * const revert_usage[] = {
        "git-revert [options] <commit-ish>",
        NULL
};

static const char * const cherry_pick_usage[] = {
        "git-cherry-pick [options] <commit-ish>",
        NULL
};

static int edit, no_replay, no_commit, mainline;
static enum { REVERT, CHERRY_PICK } action;
static struct commit *commit;

static const char *me;

#define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"

static void parse_args(int argc, const char **argv)
{
        const char * const * usage_str =
                action == REVERT ?  revert_usage : cherry_pick_usage;
        unsigned char sha1[20];
        const char *arg;
        int noop;
        struct option options[] = {
                OPT_BOOLEAN('n', "no-commit", &no_commit, "don't automatically commit"),
                OPT_BOOLEAN('e', "edit", &edit, "edit the commit message"),
                OPT_BOOLEAN('x', NULL, &no_replay, "append commit name when cherry-picking"),
                OPT_BOOLEAN('r', NULL, &noop, "no-op (backward compatibility)"),
                OPT_INTEGER('m', "mainline", &mainline, "parent number"),
                OPT_END(),
        };

        if (parse_options(argc, argv, options, usage_str, 0) != 1)
                usage_with_options(usage_str, options);
        arg = argv[0];

        if (get_sha1(arg, sha1))
                die ("Cannot find '%s'", arg);
        commit = (struct commit *)parse_object(sha1);
        if (!commit)
                die ("Could not find %s", sha1_to_hex(sha1));
        if (commit->object.type == OBJ_TAG) {
                commit = (struct commit *)
                        deref_tag((struct object *)commit, arg, strlen(arg));
        }
        if (commit->object.type != OBJ_COMMIT)
                die ("'%s' does not point to a commit", arg);
}

static char *get_oneline(const char *message)
{
        char *result;
        const char *p = message, *abbrev, *eol;
        int abbrev_len, oneline_len;

        if (!p)
                die ("Could not read commit message of %s",
                                sha1_to_hex(commit->object.sha1));
        while (*p && (*p != '\n' || p[1] != '\n'))
                p++;

        if (*p) {
                p += 2;
                for (eol = p + 1; *eol && *eol != '\n'; eol++)
                        ; /* do nothing */
        } else
                eol = p;
        abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
        abbrev_len = strlen(abbrev);
        oneline_len = eol - p;
        result = xmalloc(abbrev_len + 5 + oneline_len);
        memcpy(result, abbrev, abbrev_len);
        memcpy(result + abbrev_len, "... ", 4);
        memcpy(result + abbrev_len + 4, p, oneline_len);
        result[abbrev_len + 4 + oneline_len] = '\0';
        return result;
}

static char *get_encoding(const char *message)
{
        const char *p = message, *eol;

        if (!p)
                die ("Could not read commit message of %s",
                                sha1_to_hex(commit->object.sha1));
        while (*p && *p != '\n') {
                for (eol = p + 1; *eol && *eol != '\n'; eol++)
                        ; /* do nothing */
                if (!prefixcmp(p, "encoding ")) {
                        char *result = xmalloc(eol - 8 - p);
                        strlcpy(result, p + 9, eol - 8 - p);
                        return result;
                }
                p = eol;
                if (*p == '\n')
                        p++;
        }
        return NULL;
}

static struct lock_file msg_file;
static int msg_fd;

static void add_to_msg(const char *string)
{
        int len = strlen(string);
        if (write_in_full(msg_fd, string, len) < 0)
                die ("Could not write to MERGE_MSG");
}

static void add_message_to_msg(const char *message)
{
        const char *p = message;
        while (*p && (*p != '\n' || p[1] != '\n'))
                p++;

        if (!*p)
                add_to_msg(sha1_to_hex(commit->object.sha1));

        p += 2;
        add_to_msg(p);
        return;
}

static void set_author_ident_env(const char *message)
{
        const char *p = message;
        if (!p)
                die ("Could not read commit message of %s",
                                sha1_to_hex(commit->object.sha1));
        while (*p && *p != '\n') {
                const char *eol;

                for (eol = p; *eol && *eol != '\n'; eol++)
                        ; /* do nothing */
                if (!prefixcmp(p, "author ")) {
                        char *line, *pend, *email, *timestamp;

                        p += 7;
                        line = xmemdupz(p, eol - p);
                        email = strchr(line, '<');
                        if (!email)
                                die ("Could not extract author email from %s",
                                        sha1_to_hex(commit->object.sha1));
                        if (email == line)
                                pend = line;
                        else
                                for (pend = email; pend != line + 1 &&
                                                isspace(pend[-1]); pend--);
                                        ; /* do nothing */
                        *pend = '\0';
                        email++;
                        timestamp = strchr(email, '>');
                        if (!timestamp)
                                die ("Could not extract author email from %s",
                                        sha1_to_hex(commit->object.sha1));
                        *timestamp = '\0';
                        for (timestamp++; *timestamp && isspace(*timestamp);
                                        timestamp++)
                                ; /* do nothing */
                        setenv("GIT_AUTHOR_NAME", line, 1);
                        setenv("GIT_AUTHOR_EMAIL", email, 1);
                        setenv("GIT_AUTHOR_DATE", timestamp, 1);
                        free(line);
                        return;
                }
                p = eol;
                if (*p == '\n')
                        p++;
        }
        die ("No author information found in %s",
                        sha1_to_hex(commit->object.sha1));
}

static int merge_recursive(const char *base_sha1,
                const char *head_sha1, const char *head_name,
                const char *next_sha1, const char *next_name)
{
        char buffer[256];
        const char *argv[6];

        sprintf(buffer, "GITHEAD_%s", head_sha1);
        setenv(buffer, head_name, 1);
        sprintf(buffer, "GITHEAD_%s", next_sha1);
        setenv(buffer, next_name, 1);

        /*
         * This three way merge is an interesting one.  We are at
         * $head, and would want to apply the change between $commit
         * and $prev on top of us (when reverting), or the change between
         * $prev and $commit on top of us (when cherry-picking or replaying).
         */
        argv[0] = "merge-recursive";
        argv[1] = base_sha1;
        argv[2] = "--";
        argv[3] = head_sha1;
        argv[4] = next_sha1;
        argv[5] = NULL;

        return run_command_v_opt(argv, RUN_COMMAND_NO_STDIN | RUN_GIT_CMD);
}

static char *help_msg(const unsigned char *sha1)
{
        static char helpbuf[1024];
        char *msg = getenv("GIT_CHERRY_PICK_HELP");

        if (msg)
                return msg;

        strcpy(helpbuf, "  After resolving the conflicts,\n"
               "mark the corrected paths with 'git add <paths>' "
               "or 'git rm <paths>' and commit the result.");

        if (action == CHERRY_PICK) {
                sprintf(helpbuf + strlen(helpbuf),
                        "\nWhen commiting, use the option "
                        "'-c %s' to retain authorship and message.",
                        find_unique_abbrev(sha1, DEFAULT_ABBREV));
        }
        return helpbuf;
}

static int revert_or_cherry_pick(int argc, const char **argv)
{
        unsigned char head[20];
        struct commit *base, *next, *parent;
        int i;
        char *oneline, *reencoded_message = NULL;
        const char *message, *encoding;
        const char *defmsg = xstrdup(git_path("MERGE_MSG"));

        git_config(git_default_config);
        me = action == REVERT ? "revert" : "cherry-pick";
        setenv(GIT_REFLOG_ACTION, me, 0);
        parse_args(argc, argv);

        /* this is copied from the shell script, but it's never triggered... */
        if (action == REVERT && !no_replay)
                die("revert is incompatible with replay");

        if (no_commit) {
                /*
                 * We do not intend to commit immediately.  We just want to
                 * merge the differences in, so let's compute the tree
                 * that represents the "current" state for merge-recursive
                 * to work on.
                 */
                if (write_cache_as_tree(head, 0, NULL))
                        die ("Your index file is unmerged.");
        } else {
                struct wt_status s;

                if (get_sha1("HEAD", head))
                        die ("You do not have a valid HEAD");
                wt_status_prepare(&s);
                if (s.commitable)
                        die ("Dirty index: cannot %s", me);
                discard_cache();
        }

        if (!commit->parents)
                die ("Cannot %s a root commit", me);
        if (commit->parents->next) {
                /* Reverting or cherry-picking a merge commit */
                int cnt;
                struct commit_list *p;

                if (!mainline)
                        die("Commit %s is a merge but no -m option was given.",
                            sha1_to_hex(commit->object.sha1));

                for (cnt = 1, p = commit->parents;
                     cnt != mainline && p;
                     cnt++)
                        p = p->next;
                if (cnt != mainline || !p)
                        die("Commit %s does not have parent %d",
                            sha1_to_hex(commit->object.sha1), mainline);
                parent = p->item;
        } else if (0 < mainline)
                die("Mainline was specified but commit %s is not a merge.",
                    sha1_to_hex(commit->object.sha1));
        else
                parent = commit->parents->item;

        if (!(message = commit->buffer))
                die ("Cannot get commit message for %s",
                                sha1_to_hex(commit->object.sha1));

        /*
         * "commit" is an existing commit.  We would want to apply
         * the difference it introduces since its first parent "prev"
         * on top of the current HEAD if we are cherry-pick.  Or the
         * reverse of it if we are revert.
         */

        msg_fd = hold_lock_file_for_update(&msg_file, defmsg, 1);

        encoding = get_encoding(message);
        if (!encoding)
                encoding = "utf-8";
        if (!git_commit_encoding)
                git_commit_encoding = "utf-8";
        if ((reencoded_message = reencode_string(message,
                                        git_commit_encoding, encoding)))
                message = reencoded_message;

        oneline = get_oneline(message);

        if (action == REVERT) {
                char *oneline_body = strchr(oneline, ' ');

                base = commit;
                next = parent;
                add_to_msg("Revert \"");
                add_to_msg(oneline_body + 1);
                add_to_msg("\"\n\nThis reverts commit ");
                add_to_msg(sha1_to_hex(commit->object.sha1));
                add_to_msg(".\n");
        } else {
                base = parent;
                next = commit;
                set_author_ident_env(message);
                add_message_to_msg(message);
                if (no_replay) {
                        add_to_msg("(cherry picked from commit ");
                        add_to_msg(sha1_to_hex(commit->object.sha1));
                        add_to_msg(")\n");
                }
        }

        if (merge_recursive(sha1_to_hex(base->object.sha1),
                                sha1_to_hex(head), "HEAD",
                                sha1_to_hex(next->object.sha1), oneline) ||
                        write_cache_as_tree(head, 0, NULL)) {
                add_to_msg("\nConflicts:\n\n");
                read_cache();
                for (i = 0; i < active_nr;) {
                        struct cache_entry *ce = active_cache[i++];
                        if (ce_stage(ce)) {
                                add_to_msg("\t");
                                add_to_msg(ce->name);
                                add_to_msg("\n");
                                while (i < active_nr && !strcmp(ce->name,
                                                active_cache[i]->name))
                                        i++;
                        }
                }
                if (commit_lock_file(&msg_file) < 0)
                        die ("Error wrapping up %s", defmsg);
                fprintf(stderr, "Automatic %s failed.%s\n",
                        me, help_msg(commit->object.sha1));
                exit(1);
        }
        if (commit_lock_file(&msg_file) < 0)
                die ("Error wrapping up %s", defmsg);
        fprintf(stderr, "Finished one %s.\n", me);

        /*
         *
         * If we are cherry-pick, and if the merge did not result in
         * hand-editing, we will hit this commit and inherit the original
         * author date and name.
         * If we are revert, or if our cherry-pick results in a hand merge,
         * we had better say that the current user is responsible for that.
         */

        if (!no_commit) {
                if (edit)
                        return execl_git_cmd("commit", "-n", NULL);
                else
                        return execl_git_cmd("commit", "-n", "-F", defmsg, NULL);
        }
        free(reencoded_message);

        return 0;
}

int cmd_revert(int argc, const char **argv, const char *prefix)
{
        if (isatty(0))
                edit = 1;
        no_replay = 1;
        action = REVERT;
        return revert_or_cherry_pick(argc, argv);
}

int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
{
        no_replay = 0;
        action = CHERRY_PICK;
        return revert_or_cherry_pick(argc, argv);
}