/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This handles basic git sha1 object files - packing, unpacking,
 * creation etc.
 */
#include <stdarg.h>
#include "cache.h"

const char *sha1_file_directory = NULL;

static unsigned hexval(char c)
{
        if (c >= '0' && c <= '9')
                return c - '0';
        if (c >= 'a' && c <= 'f')
                return c - 'a' + 10;
        if (c >= 'A' && c <= 'F')
                return c - 'A' + 10;
        return ~0;
}

int get_sha1_hex(const char *hex, unsigned char *sha1)
{
        int i;
        for (i = 0; i < 20; i++) {
                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
                if (val & ~0xff)
                        return -1;
                *sha1++ = val;
                hex += 2;
        }
        return 0;
}

char * sha1_to_hex(const unsigned char *sha1)
{
        static char buffer[50];
        static const char hex[] = "0123456789abcdef";
        char *buf = buffer;
        int i;

        for (i = 0; i < 20; i++) {
                unsigned int val = *sha1++;
                *buf++ = hex[val >> 4];
                *buf++ = hex[val & 0xf];
        }
        return buffer;
}

/*
 * NOTE! This returns a statically allocated buffer, so you have to be
 * careful about using it. Do a "strdup()" if you need to save the
 * filename.
 */
char *sha1_file_name(const unsigned char *sha1)
{
        int i;
        static char *name, *base;

        if (!base) {
                char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
                int len = strlen(sha1_file_directory);
                base = malloc(len + 60);
                memcpy(base, sha1_file_directory, len);
                memset(base+len, 0, 60);
                base[len] = '/';
                base[len+3] = '/';
                name = base + len + 1;
        }
        for (i = 0; i < 20; i++) {
                static char hex[] = "0123456789abcdef";
                unsigned int val = sha1[i];
                char *pos = name + i*2 + (i > 0);
                *pos++ = hex[val >> 4];
                *pos = hex[val & 0xf];
        }
        return base;
}

int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
{
        char header[100];
        unsigned char real_sha1[20];
        SHA_CTX c;

        SHA1_Init(&c);
        SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
        SHA1_Update(&c, map, size);
        SHA1_Final(real_sha1, &c);
        return memcmp(sha1, real_sha1, 20) ? -1 : 0;
}

void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
{
        char *filename = sha1_file_name(sha1);
        int fd = open(filename, O_RDONLY);
        struct stat st;
        void *map;

        if (fd < 0) {
                perror(filename);
                return NULL;
        }
        if (fstat(fd, &st) < 0) {
                close(fd);
                return NULL;
        }
        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);
        if (-1 == (int)(long)map)
                return NULL;
        *size = st.st_size;
        return map;
}

void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
{
        int ret, bytes;
        z_stream stream;
        char buffer[8192];
        char *buf;

        /* Get the data stream */
        memset(&stream, 0, sizeof(stream));
        stream.next_in = map;
        stream.avail_in = mapsize;
        stream.next_out = buffer;
        stream.avail_out = sizeof(buffer);

        inflateInit(&stream);
        ret = inflate(&stream, 0);
        if (sscanf(buffer, "%10s %lu", type, size) != 2)
                return NULL;

        bytes = strlen(buffer) + 1;
        buf = malloc(*size);
        if (!buf)
                return NULL;

        memcpy(buf, buffer + bytes, stream.total_out - bytes);
        bytes = stream.total_out - bytes;
        if (bytes < *size && ret == Z_OK) {
                stream.next_out = buf + bytes;
                stream.avail_out = *size - bytes;
                while (inflate(&stream, Z_FINISH) == Z_OK)
                        /* nothing */;
        }
        inflateEnd(&stream);
        return buf;
}

void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
{
        unsigned long mapsize;
        void *map, *buf;

        map = map_sha1_file(sha1, &mapsize);
        if (map) {
                buf = unpack_sha1_file(map, mapsize, type, size);
                munmap(map, mapsize);
                return buf;
        }
        return NULL;
}

int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
{
        int size;
        char *compressed;
        z_stream stream;
        unsigned char sha1[20];
        SHA_CTX c;
        char *filename;
        int fd;

        /* Sha1.. */
        SHA1_Init(&c);
        SHA1_Update(&c, buf, len);
        SHA1_Final(sha1, &c);

        if (returnsha1)
                memcpy(returnsha1, sha1, 20);

        filename = sha1_file_name(sha1);
        fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
        if (fd < 0) {
                if (errno != EEXIST)
                        return -1;

                /*
                 * We might do collision checking here, but we'd need to
                 * uncompress the old file and check it. Later.
                 */
                return 0;
        }

        /* Set it up */
        memset(&stream, 0, sizeof(stream));
        deflateInit(&stream, Z_BEST_COMPRESSION);
        size = deflateBound(&stream, len);
        compressed = malloc(size);

        /* Compress it */
        stream.next_in = buf;
        stream.avail_in = len;
        stream.next_out = compressed;
        stream.avail_out = size;
        while (deflate(&stream, Z_FINISH) == Z_OK)
                /* nothing */;
        deflateEnd(&stream);
        size = stream.total_out;

        if (write(fd, compressed, size) != size)
                die("unable to write file");
        close(fd);
                
        return 0;
}

static inline int collision_check(char *filename, void *buf, unsigned int size)
{
#ifdef COLLISION_CHECK
        void *map;
        int fd = open(filename, O_RDONLY);
        struct stat st;
        int cmp;

        /* Unreadable object, or object went away? Strange. */
        if (fd < 0)
                return -1;

        if (fstat(fd, &st) < 0 || size != st.st_size)
                return -1;

        map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);
        if (map == MAP_FAILED)
                return -1;
        cmp = memcmp(buf, map, size);
        munmap(map, size);
        if (cmp)
                return -1;
#endif
        return 0;
}

int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
{
        char *filename = sha1_file_name(sha1);
        int fd;

        fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
        if (fd < 0) {
                if (errno != EEXIST)
                        return -1;
                if (collision_check(filename, buf, size))
                        return error("SHA1 collision detected!"
                                        " This is bad, bad, BAD!\a\n");
                return 0;
        }
        write(fd, buf, size);
        close(fd);
        return 0;
}