#include "cache.h"
#include "tag.h"
#include "commit.h"
#include "pkt-line.h"
#include "utf8.h"

int save_commit_buffer = 1;

struct sort_node
{
        /*
         * the number of children of the associated commit
         * that also occur in the list being sorted.
         */
        unsigned int indegree;

        /*
         * reference to original list item that we will re-use
         * on output.
         */
        struct commit_list * list_item;

};

const char *commit_type = "commit";

struct cmt_fmt_map {
        const char *n;
        size_t cmp_len;
        enum cmit_fmt v;
} cmt_fmts[] = {
        { "raw",        1,      CMIT_FMT_RAW },
        { "medium",     1,      CMIT_FMT_MEDIUM },
        { "short",      1,      CMIT_FMT_SHORT },
        { "email",      1,      CMIT_FMT_EMAIL },
        { "full",       5,      CMIT_FMT_FULL },
        { "fuller",     5,      CMIT_FMT_FULLER },
        { "oneline",    1,      CMIT_FMT_ONELINE },
};

enum cmit_fmt get_commit_format(const char *arg)
{
        int i;

        if (!arg || !*arg)
                return CMIT_FMT_DEFAULT;
        if (*arg == '=')
                arg++;
        for (i = 0; i < ARRAY_SIZE(cmt_fmts); i++) {
                if (!strncmp(arg, cmt_fmts[i].n, cmt_fmts[i].cmp_len) &&
                    !strncmp(arg, cmt_fmts[i].n, strlen(arg)))
                        return cmt_fmts[i].v;
        }

        die("invalid --pretty format: %s", arg);
}

static struct commit *check_commit(struct object *obj,
                                   const unsigned char *sha1,
                                   int quiet)
{
        if (obj->type != OBJ_COMMIT) {
                if (!quiet)
                        error("Object %s is a %s, not a commit",
                              sha1_to_hex(sha1), typename(obj->type));
                return NULL;
        }
        return (struct commit *) obj;
}

struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
                                              int quiet)
{
        struct object *obj = deref_tag(parse_object(sha1), NULL, 0);

        if (!obj)
                return NULL;
        return check_commit(obj, sha1, quiet);
}

struct commit *lookup_commit_reference(const unsigned char *sha1)
{
        return lookup_commit_reference_gently(sha1, 0);
}

struct commit *lookup_commit(const unsigned char *sha1)
{
        struct object *obj = lookup_object(sha1);
        if (!obj) {
                struct commit *ret = alloc_commit_node();
                created_object(sha1, &ret->object);
                ret->object.type = OBJ_COMMIT;
                return ret;
        }
        if (!obj->type)
                obj->type = OBJ_COMMIT;
        return check_commit(obj, sha1, 0);
}

static unsigned long parse_commit_date(const char *buf)
{
        unsigned long date;

        if (memcmp(buf, "author", 6))
                return 0;
        while (*buf++ != '\n')
                /* nada */;
        if (memcmp(buf, "committer", 9))
                return 0;
        while (*buf++ != '>')
                /* nada */;
        date = strtoul(buf, NULL, 10);
        if (date == ULONG_MAX)
                date = 0;
        return date;
}

static struct commit_graft **commit_graft;
static int commit_graft_alloc, commit_graft_nr;

static int commit_graft_pos(const unsigned char *sha1)
{
        int lo, hi;
        lo = 0;
        hi = commit_graft_nr;
        while (lo < hi) {
                int mi = (lo + hi) / 2;
                struct commit_graft *graft = commit_graft[mi];
                int cmp = hashcmp(sha1, graft->sha1);
                if (!cmp)
                        return mi;
                if (cmp < 0)
                        hi = mi;
                else
                        lo = mi + 1;
        }
        return -lo - 1;
}

int register_commit_graft(struct commit_graft *graft, int ignore_dups)
{
        int pos = commit_graft_pos(graft->sha1);
        
        if (0 <= pos) {
                if (ignore_dups)
                        free(graft);
                else {
                        free(commit_graft[pos]);
                        commit_graft[pos] = graft;
                }
                return 1;
        }
        pos = -pos - 1;
        if (commit_graft_alloc <= ++commit_graft_nr) {
                commit_graft_alloc = alloc_nr(commit_graft_alloc);
                commit_graft = xrealloc(commit_graft,
                                        sizeof(*commit_graft) *
                                        commit_graft_alloc);
        }
        if (pos < commit_graft_nr)
                memmove(commit_graft + pos + 1,
                        commit_graft + pos,
                        (commit_graft_nr - pos - 1) *
                        sizeof(*commit_graft));
        commit_graft[pos] = graft;
        return 0;
}

struct commit_graft *read_graft_line(char *buf, int len)
{
        /* The format is just "Commit Parent1 Parent2 ...\n" */
        int i;
        struct commit_graft *graft = NULL;

        if (buf[len-1] == '\n')
                buf[--len] = 0;
        if (buf[0] == '#' || buf[0] == '\0')
                return NULL;
        if ((len + 1) % 41) {
        bad_graft_data:
                error("bad graft data: %s", buf);
                free(graft);
                return NULL;
        }
        i = (len + 1) / 41 - 1;
        graft = xmalloc(sizeof(*graft) + 20 * i);
        graft->nr_parent = i;
        if (get_sha1_hex(buf, graft->sha1))
                goto bad_graft_data;
        for (i = 40; i < len; i += 41) {
                if (buf[i] != ' ')
                        goto bad_graft_data;
                if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
                        goto bad_graft_data;
        }
        return graft;
}

int read_graft_file(const char *graft_file)
{
        FILE *fp = fopen(graft_file, "r");
        char buf[1024];
        if (!fp)
                return -1;
        while (fgets(buf, sizeof(buf), fp)) {
                /* The format is just "Commit Parent1 Parent2 ...\n" */
                int len = strlen(buf);
                struct commit_graft *graft = read_graft_line(buf, len);
                if (!graft)
                        continue;
                if (register_commit_graft(graft, 1))
                        error("duplicate graft data: %s", buf);
        }
        fclose(fp);
        return 0;
}

static void prepare_commit_graft(void)
{
        static int commit_graft_prepared;
        char *graft_file;

        if (commit_graft_prepared)
                return;
        graft_file = get_graft_file();
        read_graft_file(graft_file);
        /* make sure shallows are read */
        is_repository_shallow();
        commit_graft_prepared = 1;
}

static struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
{
        int pos;
        prepare_commit_graft();
        pos = commit_graft_pos(sha1);
        if (pos < 0)
                return NULL;
        return commit_graft[pos];
}

int write_shallow_commits(int fd, int use_pack_protocol)
{
        int i, count = 0;
        for (i = 0; i < commit_graft_nr; i++)
                if (commit_graft[i]->nr_parent < 0) {
                        const char *hex =
                                sha1_to_hex(commit_graft[i]->sha1);
                        count++;
                        if (use_pack_protocol)
                                packet_write(fd, "shallow %s", hex);
                        else {
                                if (write_in_full(fd, hex,  40) != 40)
                                        break;
                                if (write_in_full(fd, "\n", 1) != 1)
                                        break;
                        }
                }
        return count;
}

int unregister_shallow(const unsigned char *sha1)
{
        int pos = commit_graft_pos(sha1);
        if (pos < 0)
                return -1;
        if (pos + 1 < commit_graft_nr)
                memcpy(commit_graft + pos, commit_graft + pos + 1,
                                sizeof(struct commit_graft *)
                                * (commit_graft_nr - pos - 1));
        commit_graft_nr--;
        return 0;
}

int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
{
        char *tail = buffer;
        char *bufptr = buffer;
        unsigned char parent[20];
        struct commit_list **pptr;
        struct commit_graft *graft;
        unsigned n_refs = 0;

        if (item->object.parsed)
                return 0;
        item->object.parsed = 1;
        tail += size;
        if (tail <= bufptr + 5 || memcmp(bufptr, "tree ", 5))
                return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
        if (tail <= bufptr + 45 || get_sha1_hex(bufptr + 5, parent) < 0)
                return error("bad tree pointer in commit %s",
                             sha1_to_hex(item->object.sha1));
        item->tree = lookup_tree(parent);
        if (item->tree)
                n_refs++;
        bufptr += 46; /* "tree " + "hex sha1" + "\n" */
        pptr = &item->parents;

        graft = lookup_commit_graft(item->object.sha1);
        while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
                struct commit *new_parent;

                if (tail <= bufptr + 48 ||
                    get_sha1_hex(bufptr + 7, parent) ||
                    bufptr[47] != '\n')
                        return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
                bufptr += 48;
                if (graft)
                        continue;
                new_parent = lookup_commit(parent);
                if (new_parent) {
                        pptr = &commit_list_insert(new_parent, pptr)->next;
                        n_refs++;
                }
        }
        if (graft) {
                int i;
                struct commit *new_parent;
                for (i = 0; i < graft->nr_parent; i++) {
                        new_parent = lookup_commit(graft->parent[i]);
                        if (!new_parent)
                                continue;
                        pptr = &commit_list_insert(new_parent, pptr)->next;
                        n_refs++;
                }
        }
        item->date = parse_commit_date(bufptr);

        if (track_object_refs) {
                unsigned i = 0;
                struct commit_list *p;
                struct object_refs *refs = alloc_object_refs(n_refs);
                if (item->tree)
                        refs->ref[i++] = &item->tree->object;
                for (p = item->parents; p; p = p->next)
                        refs->ref[i++] = &p->item->object;
                set_object_refs(&item->object, refs);
        }

        return 0;
}

int parse_commit(struct commit *item)
{
        char type[20];
        void *buffer;
        unsigned long size;
        int ret;

        if (item->object.parsed)
                return 0;
        buffer = read_sha1_file(item->object.sha1, type, &size);
        if (!buffer)
                return error("Could not read %s",
                             sha1_to_hex(item->object.sha1));
        if (strcmp(type, commit_type)) {
                free(buffer);
                return error("Object %s not a commit",
                             sha1_to_hex(item->object.sha1));
        }
        ret = parse_commit_buffer(item, buffer, size);
        if (save_commit_buffer && !ret) {
                item->buffer = buffer;
                return 0;
        }
        free(buffer);
        return ret;
}

struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
{
        struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
        new_list->item = item;
        new_list->next = *list_p;
        *list_p = new_list;
        return new_list;
}

void free_commit_list(struct commit_list *list)
{
        while (list) {
                struct commit_list *temp = list;
                list = temp->next;
                free(temp);
        }
}

struct commit_list * insert_by_date(struct commit *item, struct commit_list **list)
{
        struct commit_list **pp = list;
        struct commit_list *p;
        while ((p = *pp) != NULL) {
                if (p->item->date < item->date) {
                        break;
                }
                pp = &p->next;
        }
        return commit_list_insert(item, pp);
}

        
void sort_by_date(struct commit_list **list)
{
        struct commit_list *ret = NULL;
        while (*list) {
                insert_by_date((*list)->item, &ret);
                *list = (*list)->next;
        }
        *list = ret;
}

struct commit *pop_most_recent_commit(struct commit_list **list,
                                      unsigned int mark)
{
        struct commit *ret = (*list)->item;
        struct commit_list *parents = ret->parents;
        struct commit_list *old = *list;

        *list = (*list)->next;
        free(old);

        while (parents) {
                struct commit *commit = parents->item;
                parse_commit(commit);
                if (!(commit->object.flags & mark)) {
                        commit->object.flags |= mark;
                        insert_by_date(commit, list);
                }
                parents = parents->next;
        }
        return ret;
}

void clear_commit_marks(struct commit *commit, unsigned int mark)
{
        struct commit_list *parents;

        commit->object.flags &= ~mark;
        parents = commit->parents;
        while (parents) {
                struct commit *parent = parents->item;

                /* Have we already cleared this? */
                if (mark & parent->object.flags)
                        clear_commit_marks(parent, mark);
                parents = parents->next;
        }
}

/*
 * Generic support for pretty-printing the header
 */
static int get_one_line(const char *msg, unsigned long len)
{
        int ret = 0;

        while (len--) {
                char c = *msg++;
                if (!c)
                        break;
                ret++;
                if (c == '\n')
                        break;
        }
        return ret;
}

/* High bit set, or ISO-2022-INT */
static int non_ascii(int ch)
{
        ch = (ch & 0xff);
        return ((ch & 0x80) || (ch == 0x1b));
}

static int is_rfc2047_special(char ch)
{
        return (non_ascii(ch) || (ch == '=') || (ch == '?') || (ch == '_'));
}

static int add_rfc2047(char *buf, const char *line, int len,
                       const char *encoding)
{
        char *bp = buf;
        int i, needquote;
        char q_encoding[128];
        const char *q_encoding_fmt = "=?%s?q?";

        for (i = needquote = 0; !needquote && i < len; i++) {
                int ch = line[i];
                if (non_ascii(ch))
                        needquote++;
                if ((i + 1 < len) &&
                    (ch == '=' && line[i+1] == '?'))
                        needquote++;
        }
        if (!needquote)
                return sprintf(buf, "%.*s", len, line);

        i = snprintf(q_encoding, sizeof(q_encoding), q_encoding_fmt, encoding);
        if (sizeof(q_encoding) < i)
                die("Insanely long encoding name %s", encoding);
        memcpy(bp, q_encoding, i);
        bp += i;
        for (i = 0; i < len; i++) {
                unsigned ch = line[i] & 0xFF;
                if (is_rfc2047_special(ch)) {
                        sprintf(bp, "=%02X", ch);
                        bp += 3;
                }
                else if (ch == ' ')
                        *bp++ = '_';
                else
                        *bp++ = ch;
        }
        memcpy(bp, "?=", 2);
        bp += 2;
        return bp - buf;
}

static int add_user_info(const char *what, enum cmit_fmt fmt, char *buf,
                         const char *line, int relative_date,
                         const char *encoding)
{
        char *date;
        int namelen;
        unsigned long time;
        int tz, ret;
        const char *filler = "    ";

        if (fmt == CMIT_FMT_ONELINE)
                return 0;
        date = strchr(line, '>');
        if (!date)
                return 0;
        namelen = ++date - line;
        time = strtoul(date, &date, 10);
        tz = strtol(date, NULL, 10);

        if (fmt == CMIT_FMT_EMAIL) {
                char *name_tail = strchr(line, '<');
                int display_name_length;
                if (!name_tail)
                        return 0;
                while (line < name_tail && isspace(name_tail[-1]))
                        name_tail--;
                display_name_length = name_tail - line;
                filler = "";
                strcpy(buf, "From: ");
                ret = strlen(buf);
                ret += add_rfc2047(buf + ret, line, display_name_length,
                                   encoding);
                memcpy(buf + ret, name_tail, namelen - display_name_length);
                ret += namelen - display_name_length;
                buf[ret++] = '\n';
        }
        else {
                ret = sprintf(buf, "%s: %.*s%.*s\n", what,
                              (fmt == CMIT_FMT_FULLER) ? 4 : 0,
                              filler, namelen, line);
        }
        switch (fmt) {
        case CMIT_FMT_MEDIUM:
                ret += sprintf(buf + ret, "Date:   %s\n",
                               show_date(time, tz, relative_date));
                break;
        case CMIT_FMT_EMAIL:
                ret += sprintf(buf + ret, "Date: %s\n",
                               show_rfc2822_date(time, tz));
                break;
        case CMIT_FMT_FULLER:
                ret += sprintf(buf + ret, "%sDate: %s\n", what,
                               show_date(time, tz, relative_date));
                break;
        default:
                /* notin' */
                break;
        }
        return ret;
}

static int is_empty_line(const char *line, int *len_p)
{
        int len = *len_p;
        while (len && isspace(line[len-1]))
                len--;
        *len_p = len;
        return !len;
}

static int add_merge_info(enum cmit_fmt fmt, char *buf, const struct commit *commit, int abbrev)
{
        struct commit_list *parent = commit->parents;
        int offset;

        if ((fmt == CMIT_FMT_ONELINE) || (fmt == CMIT_FMT_EMAIL) ||
            !parent || !parent->next)
                return 0;

        offset = sprintf(buf, "Merge:");

        while (parent) {
                struct commit *p = parent->item;
                const char *hex = NULL;
                const char *dots;
                if (abbrev)
                        hex = find_unique_abbrev(p->object.sha1, abbrev);
                if (!hex)
                        hex = sha1_to_hex(p->object.sha1);
                dots = (abbrev && strlen(hex) != 40) ?  "..." : "";
                parent = parent->next;

                offset += sprintf(buf + offset, " %s%s", hex, dots);
        }
        buf[offset++] = '\n';
        return offset;
}

static char *get_header(const struct commit *commit, const char *key)
{
        int key_len = strlen(key);
        const char *line = commit->buffer;

        for (;;) {
                const char *eol = strchr(line, '\n'), *next;

                if (line == eol)
                        return NULL;
                if (!eol) {
                        eol = line + strlen(line);
                        next = NULL;
                } else
                        next = eol + 1;
                if (!strncmp(line, key, key_len) && line[key_len] == ' ') {
                        int len = eol - line - key_len;
                        char *ret = xmalloc(len);
                        memcpy(ret, line + key_len + 1, len - 1);
                        ret[len - 1] = '\0';
                        return ret;
                }
                line = next;
        }
}

static char *replace_encoding_header(char *buf, char *encoding)
{
        char *encoding_header = strstr(buf, "\nencoding ");
        char *end_of_encoding_header;
        int encoding_header_pos;
        int encoding_header_len;
        int new_len;
        int need_len;
        int buflen = strlen(buf) + 1;

        if (!encoding_header)
                return buf; /* should not happen but be defensive */
        encoding_header++;
        end_of_encoding_header = strchr(encoding_header, '\n');
        if (!end_of_encoding_header)
                return buf; /* should not happen but be defensive */
        end_of_encoding_header++;

        encoding_header_len = end_of_encoding_header - encoding_header;
        encoding_header_pos = encoding_header - buf;

        if (is_encoding_utf8(encoding)) {
                /* we have re-coded to UTF-8; drop the header */
                memmove(encoding_header, end_of_encoding_header,
                        buflen - (encoding_header_pos + encoding_header_len));
                return buf;
        }
        new_len = strlen(encoding);
        need_len = new_len + strlen("encoding \n");
        if (encoding_header_len < need_len) {
                buf = xrealloc(buf, buflen + (need_len - encoding_header_len));
                encoding_header = buf + encoding_header_pos;
                end_of_encoding_header = encoding_header + encoding_header_len;
        }
        memmove(end_of_encoding_header + (need_len - encoding_header_len),
                end_of_encoding_header,
                buflen - (encoding_header_pos + encoding_header_len));
        memcpy(encoding_header + 9, encoding, strlen(encoding));
        encoding_header[9 + new_len] = '\n';
        return buf;
}

static char *logmsg_reencode(const struct commit *commit,
                             char *output_encoding)
{
        char *encoding;
        char *out;
        char *utf8 = "utf-8";

        if (!*output_encoding)
                return NULL;
        encoding = get_header(commit, "encoding");
        if (!encoding)
                encoding = utf8;
        if (!strcmp(encoding, output_encoding))
                out = strdup(commit->buffer);
        else
                out = reencode_string(commit->buffer,
                                      output_encoding, encoding);
        if (out)
                out = replace_encoding_header(out, output_encoding);

        if (encoding != utf8)
                free(encoding);
        if (!out)
                return NULL;
        return out;
}

unsigned long pretty_print_commit(enum cmit_fmt fmt,
                                  const struct commit *commit,
                                  unsigned long len,
                                  char *buf, unsigned long space,
                                  int abbrev, const char *subject,
                                  const char *after_subject,
                                  int relative_date)
{
        int hdr = 1, body = 0, seen_title = 0;
        unsigned long offset = 0;
        int indent = 4;
        int parents_shown = 0;
        const char *msg = commit->buffer;
        int plain_non_ascii = 0;
        char *reencoded;
        char *encoding;

        encoding = (git_log_output_encoding
                    ? git_log_output_encoding
                    : git_commit_encoding);
        if (!encoding)
                encoding = "utf-8";
        reencoded = logmsg_reencode(commit, encoding);
        if (reencoded)
                msg = reencoded;

        if (fmt == CMIT_FMT_ONELINE || fmt == CMIT_FMT_EMAIL)
                indent = 0;

        /* After-subject is used to pass in Content-Type: multipart
         * MIME header; in that case we do not have to do the
         * plaintext content type even if the commit message has
         * non 7-bit ASCII character.  Otherwise, check if we need
         * to say this is not a 7-bit ASCII.
         */
        if (fmt == CMIT_FMT_EMAIL && !after_subject) {
                int i, ch, in_body;

                for (in_body = i = 0; (ch = msg[i]) && i < len; i++) {
                        if (!in_body) {
                                /* author could be non 7-bit ASCII but
                                 * the log may be so; skip over the
                                 * header part first.
                                 */
                                if (ch == '\n' &&
                                    i + 1 < len && msg[i+1] == '\n')
                                        in_body = 1;
                        }
                        else if (non_ascii(ch)) {
                                plain_non_ascii = 1;
                                break;
                        }
                }
        }

        for (;;) {
                const char *line = msg;
                int linelen = get_one_line(msg, len);

                if (!linelen)
                        break;

                /*
                 * We want some slop for indentation and a possible
                 * final "...". Thus the "+ 20".
                 */
                if (offset + linelen + 20 > space) {
                        memcpy(buf + offset, "    ...\n", 8);
                        offset += 8;
                        break;
                }

                msg += linelen;
                len -= linelen;
                if (hdr) {
                        if (linelen == 1) {
                                hdr = 0;
                                if ((fmt != CMIT_FMT_ONELINE) && !subject)
                                        buf[offset++] = '\n';
                                continue;
                        }
                        if (fmt == CMIT_FMT_RAW) {
                                memcpy(buf + offset, line, linelen);
                                offset += linelen;
                                continue;
                        }
                        if (!memcmp(line, "parent ", 7)) {
                                if (linelen != 48)
                                        die("bad parent line in commit");
                                continue;
                        }

                        if (!parents_shown) {
                                offset += add_merge_info(fmt, buf + offset,
                                                         commit, abbrev);
                                parents_shown = 1;
                                continue;
                        }
                        /*
                         * MEDIUM == DEFAULT shows only author with dates.
                         * FULL shows both authors but not dates.
                         * FULLER shows both authors and dates.
                         */
                        if (!memcmp(line, "author ", 7))
                                offset += add_user_info("Author", fmt,
                                                        buf + offset,
                                                        line + 7,
                                                        relative_date,
                                                        encoding);
                        if (!memcmp(line, "committer ", 10) &&
                            (fmt == CMIT_FMT_FULL || fmt == CMIT_FMT_FULLER))
                                offset += add_user_info("Commit", fmt,
                                                        buf + offset,
                                                        line + 10,
                                                        relative_date,
                                                        encoding);
                        continue;
                }

                if (!subject)
                        body = 1;

                if (is_empty_line(line, &linelen)) {
                        if (!seen_title)
                                continue;
                        if (!body)
                                continue;
                        if (subject)
                                continue;
                        if (fmt == CMIT_FMT_SHORT)
                                break;
                }

                seen_title = 1;
                if (subject) {
                        int slen = strlen(subject);
                        memcpy(buf + offset, subject, slen);
                        offset += slen;
                        offset += add_rfc2047(buf + offset, line, linelen,
                                              encoding);
                }
                else {
                        memset(buf + offset, ' ', indent);
                        memcpy(buf + offset + indent, line, linelen);
                        offset += linelen + indent;
                }
                buf[offset++] = '\n';
                if (fmt == CMIT_FMT_ONELINE)
                        break;
                if (subject && plain_non_ascii) {
                        int sz;
                        char header[512];
                        const char *header_fmt =
                                "Content-Type: text/plain; charset=%s\n"
                                "Content-Transfer-Encoding: 8bit\n";
                        sz = snprintf(header, sizeof(header), header_fmt,
                                      encoding);
                        if (sizeof(header) < sz)
                                die("Encoding name %s too long", encoding);
                        memcpy(buf + offset, header, sz);
                        offset += sz;
                }
                if (after_subject) {
                        int slen = strlen(after_subject);
                        if (slen > space - offset - 1)
                                slen = space - offset - 1;
                        memcpy(buf + offset, after_subject, slen);
                        offset += slen;
                        after_subject = NULL;
                }
                subject = NULL;
        }
        while (offset && isspace(buf[offset-1]))
                offset--;
        /* Make sure there is an EOLN for the non-oneline case */
        if (fmt != CMIT_FMT_ONELINE)
                buf[offset++] = '\n';
        /*
         * make sure there is another EOLN to separate the headers from whatever
         * body the caller appends if we haven't already written a body
         */
        if (fmt == CMIT_FMT_EMAIL && !body)
                buf[offset++] = '\n';
        buf[offset] = '\0';

        free(reencoded);
        return offset;
}

struct commit *pop_commit(struct commit_list **stack)
{
        struct commit_list *top = *stack;
        struct commit *item = top ? top->item : NULL;

        if (top) {
                *stack = top->next;
                free(top);
        }
        return item;
}

int count_parents(struct commit * commit)
{
        int count;
        struct commit_list * parents = commit->parents;
        for (count = 0; parents; parents = parents->next,count++)
                ;
        return count;
}

void topo_sort_default_setter(struct commit *c, void *data)
{
        c->util = data;
}

void *topo_sort_default_getter(struct commit *c)
{
        return c->util;
}

/*
 * Performs an in-place topological sort on the list supplied.
 */
void sort_in_topological_order(struct commit_list ** list, int lifo)
{
        sort_in_topological_order_fn(list, lifo, topo_sort_default_setter,
                                     topo_sort_default_getter);
}

void sort_in_topological_order_fn(struct commit_list ** list, int lifo,
                                  topo_sort_set_fn_t setter,
                                  topo_sort_get_fn_t getter)
{
        struct commit_list * next = *list;
        struct commit_list * work = NULL, **insert;
        struct commit_list ** pptr = list;
        struct sort_node * nodes;
        struct sort_node * next_nodes;
        int count = 0;

        /* determine the size of the list */
        while (next) {
                next = next->next;
                count++;
        }
        
        if (!count)
                return;
        /* allocate an array to help sort the list */
        nodes = xcalloc(count, sizeof(*nodes));
        /* link the list to the array */
        next_nodes = nodes;
        next=*list;
        while (next) {
                next_nodes->list_item = next;
                setter(next->item, next_nodes);
                next_nodes++;
                next = next->next;
        }
        /* update the indegree */
        next=*list;
        while (next) {
                struct commit_list * parents = next->item->parents;
                while (parents) {
                        struct commit * parent=parents->item;
                        struct sort_node * pn = (struct sort_node *) getter(parent);

                        if (pn)
                                pn->indegree++;
                        parents=parents->next;
                }
                next=next->next;
        }
        /* 
         * find the tips
         *
         * tips are nodes not reachable from any other node in the list 
         * 
         * the tips serve as a starting set for the work queue.
         */
        next=*list;
        insert = &work;
        while (next) {
                struct sort_node * node = (struct sort_node *) getter(next->item);

                if (node->indegree == 0) {
                        insert = &commit_list_insert(next->item, insert)->next;
                }
                next=next->next;
        }

        /* process the list in topological order */
        if (!lifo)
                sort_by_date(&work);
        while (work) {
                struct commit * work_item = pop_commit(&work);
                struct sort_node * work_node = (struct sort_node *) getter(work_item);
                struct commit_list * parents = work_item->parents;

                while (parents) {
                        struct commit * parent=parents->item;
                        struct sort_node * pn = (struct sort_node *) getter(parent);

                        if (pn) {
                                /*
                                 * parents are only enqueued for emission 
                                 * when all their children have been emitted thereby
                                 * guaranteeing topological order.
                                 */
                                pn->indegree--;
                                if (!pn->indegree) {
                                        if (!lifo)
                                                insert_by_date(parent, &work);
                                        else
                                                commit_list_insert(parent, &work);
                                }
                        }
                        parents=parents->next;
                }
                /*
                 * work_item is a commit all of whose children
                 * have already been emitted. we can emit it now.
                 */
                *pptr = work_node->list_item;
                pptr = &(*pptr)->next;
                *pptr = NULL;
                setter(work_item, NULL);
        }
        free(nodes);
}

/* merge-base stuff */

/* bits #0..15 in revision.h */
#define PARENT1         (1u<<16)
#define PARENT2         (1u<<17)
#define STALE           (1u<<18)
#define RESULT          (1u<<19)

static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);

static struct commit *interesting(struct commit_list *list)
{
        while (list) {
                struct commit *commit = list->item;
                list = list->next;
                if (commit->object.flags & STALE)
                        continue;
                return commit;
        }
        return NULL;
}

static struct commit_list *merge_bases(struct commit *one, struct commit *two)
{
        struct commit_list *list = NULL;
        struct commit_list *result = NULL;

        if (one == two)
                /* We do not mark this even with RESULT so we do not
                 * have to clean it up.
                 */
                return commit_list_insert(one, &result);

        parse_commit(one);
        parse_commit(two);

        one->object.flags |= PARENT1;
        two->object.flags |= PARENT2;
        insert_by_date(one, &list);
        insert_by_date(two, &list);

        while (interesting(list)) {
                struct commit *commit;
                struct commit_list *parents;
                struct commit_list *n;
                int flags;

                commit = list->item;
                n = list->next;
                free(list);
                list = n;

                flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
                if (flags == (PARENT1 | PARENT2)) {
                        if (!(commit->object.flags & RESULT)) {
                                commit->object.flags |= RESULT;
                                insert_by_date(commit, &result);
                        }
                        /* Mark parents of a found merge stale */
                        flags |= STALE;
                }
                parents = commit->parents;
                while (parents) {
                        struct commit *p = parents->item;
                        parents = parents->next;
                        if ((p->object.flags & flags) == flags)
                                continue;
                        parse_commit(p);
                        p->object.flags |= flags;
                        insert_by_date(p, &list);
                }
        }

        /* Clean up the result to remove stale ones */
        free_commit_list(list);
        list = result; result = NULL;
        while (list) {
                struct commit_list *n = list->next;
                if (!(list->item->object.flags & STALE))
                        insert_by_date(list->item, &result);
                free(list);
                list = n;
        }
        return result;
}

struct commit_list *get_merge_bases(struct commit *one,
                                    struct commit *two,
                                    int cleanup)
{
        struct commit_list *list;
        struct commit **rslt;
        struct commit_list *result;
        int cnt, i, j;

        result = merge_bases(one, two);
        if (one == two)
                return result;
        if (!result || !result->next) {
                if (cleanup) {
                        clear_commit_marks(one, all_flags);
                        clear_commit_marks(two, all_flags);
                }
                return result;
        }

        /* There are more than one */
        cnt = 0;
        list = result;
        while (list) {
                list = list->next;
                cnt++;
        }
        rslt = xcalloc(cnt, sizeof(*rslt));
        for (list = result, i = 0; list; list = list->next)
                rslt[i++] = list->item;
        free_commit_list(result);

        clear_commit_marks(one, all_flags);
        clear_commit_marks(two, all_flags);
        for (i = 0; i < cnt - 1; i++) {
                for (j = i+1; j < cnt; j++) {
                        if (!rslt[i] || !rslt[j])
                                continue;
                        result = merge_bases(rslt[i], rslt[j]);
                        clear_commit_marks(rslt[i], all_flags);
                        clear_commit_marks(rslt[j], all_flags);
                        for (list = result; list; list = list->next) {
                                if (rslt[i] == list->item)
                                        rslt[i] = NULL;
                                if (rslt[j] == list->item)
                                        rslt[j] = NULL;
                        }
                }
        }

        /* Surviving ones in rslt[] are the independent results */
        result = NULL;
        for (i = 0; i < cnt; i++) {
                if (rslt[i])
                        insert_by_date(rslt[i], &result);
        }
        free(rslt);
        return result;
}

int in_merge_bases(struct commit *rev1, struct commit *rev2)
{
        struct commit_list *bases, *b;
        int ret = 0;

        bases = get_merge_bases(rev1, rev2, 1);
        for (b = bases; b; b = b->next) {
                if (!hashcmp(rev1->object.sha1, b->item->object.sha1)) {
                        ret = 1;
                        break;
                }
        }

        free_commit_list(bases);
        return ret;
}