#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"
#include "diff.h"
#include "revision.h"
#include "rerere.h"
#include "merge-recursive.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, signoff;
static enum { REVERT, CHERRY_PICK } action;
static struct commit *commit;
static const char *commit_name;
static int allow_rerere_auto;

static const char *me;

#define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"

static char *get_encoding(const char *message);

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];
        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_BOOLEAN('s', "signoff", &signoff, "add Signed-off-by:"),
                OPT_INTEGER('m', "mainline", &mainline, "parent number"),
                OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
                OPT_END(),
        };

        if (parse_options(argc, argv, NULL, options, usage_str, 0) != 1)
                usage_with_options(usage_str, options);

        commit_name = argv[0];
        if (get_sha1(commit_name, sha1))
                die ("Cannot find '%s'", commit_name);
        commit = lookup_commit_reference(sha1);
        if (!commit)
                exit(1);
}

struct commit_message {
        char *parent_label;
        const char *label;
        const char *subject;
        char *reencoded_message;
        const char *message;
};

static int get_message(const char *raw_message, struct commit_message *out)
{
        const char *encoding;
        const char *p, *abbrev, *eol;
        char *q;
        int abbrev_len, oneline_len;

        if (!raw_message)
                return -1;
        encoding = get_encoding(raw_message);
        if (!encoding)
                encoding = "UTF-8";
        if (!git_commit_encoding)
                git_commit_encoding = "UTF-8";
        if ((out->reencoded_message = reencode_string(raw_message,
                                        git_commit_encoding, encoding)))
                out->message = out->reencoded_message;

        abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
        abbrev_len = strlen(abbrev);

        /* Find beginning and end of commit subject. */
        p = out->message;
        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;
        oneline_len = eol - p;

        out->parent_label = xmalloc(strlen("parent of ") + abbrev_len +
                              strlen("... ") + oneline_len + 1);
        q = out->parent_label;
        q = mempcpy(q, "parent of ", strlen("parent of "));
        out->label = q;
        q = mempcpy(q, abbrev, abbrev_len);
        q = mempcpy(q, "... ", strlen("... "));
        out->subject = q;
        q = mempcpy(q, p, oneline_len);
        *q = '\0';
        return 0;
}

static void free_message(struct commit_message *msg)
{
        free(msg->parent_label);
        free(msg->reencoded_message);
}

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

        if (!*p)
                strbuf_addstr(msgbuf, sha1_to_hex(commit->object.sha1));

        p += 2;
        strbuf_addstr(msgbuf, p);
}

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 time 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 char *help_msg(const char *name)
{
        struct strbuf helpbuf = STRBUF_INIT;
        char *msg = getenv("GIT_CHERRY_PICK_HELP");

        if (msg)
                return msg;

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

        if (action == CHERRY_PICK) {
                strbuf_addf(&helpbuf, " with: \n"
                        "\n"
                        "        git commit -c %s\n",
                        name);
        }
        else
                strbuf_addch(&helpbuf, '.');
        return strbuf_detach(&helpbuf, NULL);
}

static void write_message(struct strbuf *msgbuf, const char *filename)
{
        static struct lock_file msg_file;

        int msg_fd = hold_lock_file_for_update(&msg_file, filename,
                                               LOCK_DIE_ON_ERROR);
        if (write_in_full(msg_fd, msgbuf->buf, msgbuf->len) < 0)
                die_errno("Could not write to %s.", filename);
        strbuf_release(msgbuf);
        if (commit_lock_file(&msg_file) < 0)
                die("Error wrapping up %s", filename);
}

static struct tree *empty_tree(void)
{
        struct tree *tree = xcalloc(1, sizeof(struct tree));

        tree->object.parsed = 1;
        tree->object.type = OBJ_TREE;
        pretend_sha1_file(NULL, 0, OBJ_TREE, tree->object.sha1);
        return tree;
}

static NORETURN void die_dirty_index(const char *me)
{
        if (read_cache_unmerged()) {
                die_resolve_conflict(me);
        } else {
                if (advice_commit_before_merge)
                        die("Your local changes would be overwritten by %s.\n"
                            "Please, commit your changes or stash them to proceed.", me);
                else
                        die("Your local changes would be overwritten by %s.\n", me);
        }
}

static int revert_or_cherry_pick(int argc, const char **argv)
{
        unsigned char head[20];
        struct commit *base, *next, *parent;
        const char *base_label, *next_label;
        int i, index_fd, clean;
        struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };

        char *defmsg = git_pathdup("MERGE_MSG");
        struct merge_options o;
        struct tree *result, *next_tree, *base_tree, *head_tree;
        static struct lock_file index_lock;
        struct strbuf msgbuf = STRBUF_INIT;

        git_config(git_default_config, NULL);
        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 (read_cache() < 0)
                die("git %s: failed to read the index", me);
        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 {
                if (get_sha1("HEAD", head))
                        die ("You do not have a valid HEAD");
                if (index_differs_from("HEAD", 0))
                        die_dirty_index(me);
        }
        discard_cache();

        index_fd = hold_locked_index(&index_lock, 1);

        if (!commit->parents) {
                if (action == REVERT)
                        die ("Cannot revert a root commit");
                parent = NULL;
        }
        else 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 (parent && parse_commit(parent) < 0)
                die("%s: cannot parse parent commit %s",
                    me, sha1_to_hex(parent->object.sha1));

        if (get_message(commit->buffer, &msg) != 0)
                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.
         */

        if (action == REVERT) {
                base = commit;
                base_label = msg.label;
                next = parent;
                next_label = msg.parent_label;
                strbuf_addstr(&msgbuf, "Revert \"");
                strbuf_addstr(&msgbuf, msg.subject);
                strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
                strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));

                if (commit->parents->next) {
                        strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
                        strbuf_addstr(&msgbuf, sha1_to_hex(parent->object.sha1));
                }
                strbuf_addstr(&msgbuf, ".\n");
        } else {
                base = parent;
                base_label = msg.parent_label;
                next = commit;
                next_label = msg.label;
                set_author_ident_env(msg.message);
                add_message_to_msg(&msgbuf, msg.message);
                if (no_replay) {
                        strbuf_addstr(&msgbuf, "(cherry picked from commit ");
                        strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
                        strbuf_addstr(&msgbuf, ")\n");
                }
        }

        read_cache();
        init_merge_options(&o);
        o.ancestor = base ? base_label : "(empty tree)";
        o.branch1 = "HEAD";
        o.branch2 = next ? next_label : "(empty tree)";

        head_tree = parse_tree_indirect(head);
        next_tree = next ? next->tree : empty_tree();
        base_tree = base ? base->tree : empty_tree();

        clean = merge_trees(&o,
                            head_tree,
                            next_tree, base_tree, &result);

        if (active_cache_changed &&
            (write_cache(index_fd, active_cache, active_nr) ||
             commit_locked_index(&index_lock)))
                die("%s: Unable to write new index file", me);
        rollback_lock_file(&index_lock);

        if (!clean) {
                strbuf_addstr(&msgbuf, "\nConflicts:\n\n");
                for (i = 0; i < active_nr;) {
                        struct cache_entry *ce = active_cache[i++];
                        if (ce_stage(ce)) {
                                strbuf_addch(&msgbuf, '\t');
                                strbuf_addstr(&msgbuf, ce->name);
                                strbuf_addch(&msgbuf, '\n');
                                while (i < active_nr && !strcmp(ce->name,
                                                active_cache[i]->name))
                                        i++;
                        }
                }
                write_message(&msgbuf, defmsg);
                fprintf(stderr, "Automatic %s failed.%s\n",
                        me, help_msg(commit_name));
                rerere(allow_rerere_auto);
                exit(1);
        }
        write_message(&msgbuf, 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) {
                /* 6 is max possible length of our args array including NULL */
                const char *args[6];
                int i = 0;
                args[i++] = "commit";
                args[i++] = "-n";
                if (signoff)
                        args[i++] = "-s";
                if (!edit) {
                        args[i++] = "-F";
                        args[i++] = defmsg;
                }
                args[i] = NULL;
                return execv_git_cmd(args);
        }
        free_message(&msg);
        free(defmsg);

        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);
}