#define _XOPEN_SOURCE /* glibc2 needs this */
#include <time.h>
#include <ctype.h>
#include "cache.h"

struct entry {
        unsigned char old_sha1[20];
        unsigned char new_sha1[20];
        int converted;
};

#define MAXOBJECTS (1000000)

static struct entry *convert[MAXOBJECTS];
static int nr_convert;

static struct entry * convert_entry(unsigned char *sha1);

static struct entry *insert_new(unsigned char *sha1, int pos)
{
        struct entry *new = xmalloc(sizeof(struct entry));
        memset(new, 0, sizeof(*new));
        memcpy(new->old_sha1, sha1, 20);
        memmove(convert + pos + 1, convert + pos, (nr_convert - pos) * sizeof(struct entry *));
        convert[pos] = new;
        nr_convert++;
        if (nr_convert == MAXOBJECTS)
                die("you're kidding me - hit maximum object limit");
        return new;
}

static struct entry *lookup_entry(unsigned char *sha1)
{
        int low = 0, high = nr_convert;

        while (low < high) {
                int next = (low + high) / 2;
                struct entry *n = convert[next];
                int cmp = memcmp(sha1, n->old_sha1, 20);
                if (!cmp)
                        return n;
                if (cmp < 0) {
                        high = next;
                        continue;
                }
                low = next+1;
        }
        return insert_new(sha1, low);
}

static void convert_binary_sha1(void *buffer)
{
        struct entry *entry = convert_entry(buffer);
        memcpy(buffer, entry->new_sha1, 20);
}

static void convert_ascii_sha1(void *buffer)
{
        unsigned char sha1[20];
        struct entry *entry;

        if (get_sha1_hex(buffer, sha1))
                die("bad sha1");
        entry = convert_entry(sha1);
        memcpy(buffer, sha1_to_hex(entry->new_sha1), 40);
}

static int write_subdirectory(void *buffer, unsigned long size, const char *base, int baselen, unsigned char *result_sha1)
{
        char *new = xmalloc(size);
        unsigned long newlen = 0;
        unsigned long used;

        used = 0;
        while (size) {
                int len = 21 + strlen(buffer);
                char *path = strchr(buffer, ' ');
                unsigned char *sha1;
                unsigned int mode;
                char *slash, *origpath;

                if (!path || sscanf(buffer, "%o", &mode) != 1)
                        die("bad tree conversion");
                path++;
                if (memcmp(path, base, baselen))
                        break;
                origpath = path;
                path += baselen;
                slash = strchr(path, '/');
                if (!slash) {
                        newlen += sprintf(new + newlen, "%o %s", mode, path);
                        new[newlen++] = '\0';
                        memcpy(new + newlen, buffer + len - 20, 20);
                        newlen += 20;

                        used += len;
                        size -= len;
                        buffer += len;
                        continue;
                }

                newlen += sprintf(new + newlen, "%o %.*s", S_IFDIR, (int)(slash - path), path);
                new[newlen++] = 0;
                sha1 = (unsigned char *)(new + newlen);
                newlen += 20;

                len = write_subdirectory(buffer, size, origpath, slash-origpath+1, sha1);

                used += len;
                size -= len;
                buffer += len;
        }

        write_sha1_file(new, newlen, "tree", result_sha1);
        free(new);
        return used;
}

static int convert_mode(char *buffer)
{
        char *end;
        unsigned short mode = strtoul(buffer, &end, 8);
        unsigned short newmode;
        char num[10];
        int len;

        if (*end != ' ')
                die("corrupt tree object");
        switch (mode) {
        case S_IFREG | 0644:
        case S_IFREG | 0755:
        case S_IFLNK:
        case S_IFDIR:
                return 0;
        }
        newmode = 0;
        if (S_ISREG(mode))
                newmode = (mode & 0100) ? 0755 : 0644;
        newmode |= mode & S_IFMT;
        len = sprintf(num, "%o", newmode);
        if (len != end - buffer)
                return error("unable to convert tree entry mode %o to %o", mode, newmode);
        memcpy(buffer, num, len);
        return 0;
}

static void convert_tree(void *buffer, unsigned long size, unsigned char *result_sha1)
{
        void *orig_buffer = buffer;
        unsigned long orig_size = size;

        while (size) {
                int len = 1+strlen(buffer);

                convert_mode(buffer);
                convert_binary_sha1(buffer + len);

                len += 20;
                if (len > size)
                        die("corrupt tree object");
                size -= len;
                buffer += len;
        }

        write_subdirectory(orig_buffer, orig_size, "", 0, result_sha1);
}

static unsigned long parse_oldstyle_date(const char *buf)
{
        char c, *p;
        char buffer[100];
        struct tm tm;
        const char *formats[] = {
                "%c",
                "%a %b %d %T",
                "%Z",
                "%Y",
                " %Y",
                NULL
        };
        /* We only ever did two timezones in the bad old format .. */
        const char *timezones[] = {
                "PDT", "PST", "CEST", NULL
        };
        const char **fmt = formats;

        p = buffer;
        while (isspace(c = *buf))
                buf++;
        while ((c = *buf++) != '\n')
                *p++ = c;
        *p++ = 0;
        buf = buffer;
        memset(&tm, 0, sizeof(tm));
        do {
                const char *next = strptime(buf, *fmt, &tm);
                if (next) {
                        if (!*next)
                                return mktime(&tm);
                        buf = next;
                } else {
                        const char **p = timezones;
                        while (isspace(*buf))
                                buf++;
                        while (*p) {
                                if (!memcmp(buf, *p, strlen(*p))) {
                                        buf += strlen(*p);
                                        break;
                                }
                                p++;
                        }
                }
                fmt++;
        } while (*buf && *fmt);
        printf("left: %s\n", buf);
        return mktime(&tm);                             
}

static int convert_date_line(char *dst, void **buf, unsigned long *sp)
{
        unsigned long size = *sp;
        char *line = *buf;
        char *next = strchr(line, '\n');
        char *date = strchr(line, '>');
        int len;

        if (!next || !date)
                die("missing or bad author/committer line %s", line);
        next++; date += 2;

        *buf = next;
        *sp = size - (next - line);

        len = date - line;
        memcpy(dst, line, len);
        dst += len;

        /* Is it already in new format? */
        if (isdigit(*date)) {
                int datelen = next - date;
                memcpy(dst, date, datelen);
                return len + datelen;
        }

        /*
         * Hacky hacky: one of the sparse old-style commits does not have
         * any date at all, but we can fake it by using the committer date.
         */
        if (*date == '\n' && strchr(next, '>'))
                date = strchr(next, '>')+2;

        return len + sprintf(dst, "%lu -0700\n", parse_oldstyle_date(date));
}

static void convert_date(void *buffer, unsigned long size, unsigned char *result_sha1)
{
        char *new = xmalloc(size + 100);
        unsigned long newlen = 0;
        
        // "tree <sha1>\n"
        memcpy(new + newlen, buffer, 46);
        newlen += 46;
        buffer += 46;
        size -= 46;

        // "parent <sha1>\n"
        while (!memcmp(buffer, "parent ", 7)) {
                memcpy(new + newlen, buffer, 48);
                newlen += 48;
                buffer += 48;
                size -= 48;
        }

        // "author xyz <xyz> date"
        newlen += convert_date_line(new + newlen, &buffer, &size);
        // "committer xyz <xyz> date"
        newlen += convert_date_line(new + newlen, &buffer, &size);

        // Rest
        memcpy(new + newlen, buffer, size);
        newlen += size;

        write_sha1_file(new, newlen, "commit", result_sha1);
        free(new);      
}

static void convert_commit(void *buffer, unsigned long size, unsigned char *result_sha1)
{
        void *orig_buffer = buffer;
        unsigned long orig_size = size;

        convert_ascii_sha1(buffer+5);
        buffer += 46;    /* "tree " + "hex sha1" + "\n" */
        while (!memcmp(buffer, "parent ", 7)) {
                convert_ascii_sha1(buffer+7);
                buffer += 48;
        }
        convert_date(orig_buffer, orig_size, result_sha1);
}

static struct entry * convert_entry(unsigned char *sha1)
{
        struct entry *entry = lookup_entry(sha1);
        char type[20];
        void *buffer, *data;
        unsigned long size;

        if (entry->converted)
                return entry;
        data = read_sha1_file(sha1, type, &size);
        if (!data)
                die("unable to read object %s", sha1_to_hex(sha1));

        buffer = xmalloc(size);
        memcpy(buffer, data, size);
        
        if (!strcmp(type, "blob")) {
                write_sha1_file(buffer, size, "blob", entry->new_sha1);
        } else if (!strcmp(type, "tree"))
                convert_tree(buffer, size, entry->new_sha1);
        else if (!strcmp(type, "commit"))
                convert_commit(buffer, size, entry->new_sha1);
        else
                die("unknown object type '%s' in %s", type, sha1_to_hex(sha1));
        entry->converted = 1;
        free(buffer);
        return entry;
}

int main(int argc, char **argv)
{
        unsigned char sha1[20];
        struct entry *entry;

        if (argc != 2 || get_sha1(argv[1], sha1))
                usage("git-convert-cache <sha1>");

        entry = convert_entry(sha1);
        printf("new sha1: %s\n", sha1_to_hex(entry->new_sha1));
        return 0;
}