#include "cache.h"
#include "commit.h"
#include "pack.h"
#include "fetch.h"

#include <curl/curl.h>
#include <curl/easy.h>

#if LIBCURL_VERSION_NUM >= 0x070908
#define USE_CURL_MULTI
#define DEFAULT_MAX_REQUESTS 5
#endif

#if LIBCURL_VERSION_NUM < 0x070704
#define curl_global_cleanup() do { /* nothing */ } while(0)
#endif
#if LIBCURL_VERSION_NUM < 0x070800
#define curl_global_init(a) do { /* nothing */ } while(0)
#endif

#if LIBCURL_VERSION_NUM < 0x070c04
#define NO_CURL_EASY_DUPHANDLE
#endif

#define PREV_BUF_SIZE 4096
#define RANGE_HEADER_SIZE 30

static int got_alternates = -1;
static int active_requests = 0;
static int data_received;

#ifdef USE_CURL_MULTI
static int max_requests = -1;
static CURLM *curlm;
#endif
#ifndef NO_CURL_EASY_DUPHANDLE
static CURL *curl_default;
#endif
static struct curl_slist *pragma_header;
static struct curl_slist *no_pragma_header;
static struct curl_slist *no_range_header;
static char curl_errorstr[CURL_ERROR_SIZE];

struct alt_base
{
        char *base;
        int got_indices;
        struct packed_git *packs;
        struct alt_base *next;
};

static struct alt_base *alt = NULL;

enum transfer_state {
        WAITING,
        ABORTED,
        ACTIVE,
        COMPLETE,
};

struct transfer_request
{
        unsigned char sha1[20];
        struct alt_base *repo;
        char *url;
        char filename[PATH_MAX];
        char tmpfile[PATH_MAX];
        int local;
        enum transfer_state state;
        CURLcode curl_result;
        char errorstr[CURL_ERROR_SIZE];
        long http_code;
        unsigned char real_sha1[20];
        SHA_CTX c;
        z_stream stream;
        int zret;
        int rename;
        struct active_request_slot *slot;
        struct transfer_request *next;
};

struct active_request_slot
{
        CURL *curl;
        FILE *local;
        int in_use;
        int done;
        CURLcode curl_result;
        long http_code;
        void *callback_data;
        void (*callback_func)(void *data);
        struct active_request_slot *next;
};

struct alt_request {
        char *base;
        char *url;
        struct buffer *buffer;
        struct active_request_slot *slot;
        int http_specific;
};

static struct transfer_request *request_queue_head = NULL;
static struct active_request_slot *active_queue_head = NULL;

static int curl_ssl_verify = -1;
static char *ssl_cert = NULL;
#if LIBCURL_VERSION_NUM >= 0x070902
static char *ssl_key = NULL;
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
static char *ssl_capath = NULL;
#endif
static char *ssl_cainfo = NULL;
static long curl_low_speed_limit = -1;
static long curl_low_speed_time = -1;

struct buffer
{
        size_t posn;
        size_t size;
        void *buffer;
};

static int http_options(const char *var, const char *value)
{
        if (!strcmp("http.sslverify", var)) {
                if (curl_ssl_verify == -1) {
                        curl_ssl_verify = git_config_bool(var, value);
                }
                return 0;
        }

        if (!strcmp("http.sslcert", var)) {
                if (ssl_cert == NULL) {
                        ssl_cert = xmalloc(strlen(value)+1);
                        strcpy(ssl_cert, value);
                }
                return 0;
        }
#if LIBCURL_VERSION_NUM >= 0x070902
        if (!strcmp("http.sslkey", var)) {
                if (ssl_key == NULL) {
                        ssl_key = xmalloc(strlen(value)+1);
                        strcpy(ssl_key, value);
                }
                return 0;
        }
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
        if (!strcmp("http.sslcapath", var)) {
                if (ssl_capath == NULL) {
                        ssl_capath = xmalloc(strlen(value)+1);
                        strcpy(ssl_capath, value);
                }
                return 0;
        }
#endif
        if (!strcmp("http.sslcainfo", var)) {
                if (ssl_cainfo == NULL) {
                        ssl_cainfo = xmalloc(strlen(value)+1);
                        strcpy(ssl_cainfo, value);
                }
                return 0;
        }

#ifdef USE_CURL_MULTI   
        if (!strcmp("http.maxrequests", var)) {
                if (max_requests == -1)
                        max_requests = git_config_int(var, value);
                return 0;
        }
#endif

        if (!strcmp("http.lowspeedlimit", var)) {
                if (curl_low_speed_limit == -1)
                        curl_low_speed_limit = (long)git_config_int(var, value);
                return 0;
        }
        if (!strcmp("http.lowspeedtime", var)) {
                if (curl_low_speed_time == -1)
                        curl_low_speed_time = (long)git_config_int(var, value);
                return 0;
        }

        /* Fall back on the default ones */
        return git_default_config(var, value);
}

static size_t fwrite_buffer(void *ptr, size_t eltsize, size_t nmemb,
                            struct buffer *buffer)
{
        size_t size = eltsize * nmemb;
        if (size > buffer->size - buffer->posn)
                size = buffer->size - buffer->posn;
        memcpy(buffer->buffer + buffer->posn, ptr, size);
        buffer->posn += size;
        data_received++;
        return size;
}

static size_t fwrite_buffer_dynamic(const void *ptr, size_t eltsize,
                                    size_t nmemb, struct buffer *buffer)
{
        size_t size = eltsize * nmemb;
        if (size > buffer->size - buffer->posn) {
                buffer->size = buffer->size * 3 / 2;
                if (buffer->size < buffer->posn + size)
                        buffer->size = buffer->posn + size;
                buffer->buffer = xrealloc(buffer->buffer, buffer->size);
        }
        memcpy(buffer->buffer + buffer->posn, ptr, size);
        buffer->posn += size;
        data_received++;
        return size;
}

static size_t fwrite_sha1_file(void *ptr, size_t eltsize, size_t nmemb,
                               void *data)
{
        unsigned char expn[4096];
        size_t size = eltsize * nmemb;
        int posn = 0;
        struct transfer_request *request = (struct transfer_request *)data;
        do {
                ssize_t retval = write(request->local,
                                       ptr + posn, size - posn);
                if (retval < 0)
                        return posn;
                posn += retval;
        } while (posn < size);

        request->stream.avail_in = size;
        request->stream.next_in = ptr;
        do {
                request->stream.next_out = expn;
                request->stream.avail_out = sizeof(expn);
                request->zret = inflate(&request->stream, Z_SYNC_FLUSH);
                SHA1_Update(&request->c, expn,
                            sizeof(expn) - request->stream.avail_out);
        } while (request->stream.avail_in && request->zret == Z_OK);
        data_received++;
        return size;
}

#ifdef USE_CURL_MULTI
static void process_curl_messages(void);
static void process_request_queue(void);
#endif
static void fetch_alternates(char *base);

static CURL* get_curl_handle(void)
{
        CURL* result = curl_easy_init();

        curl_easy_setopt(result, CURLOPT_SSL_VERIFYPEER, curl_ssl_verify);
#if LIBCURL_VERSION_NUM >= 0x070907
        curl_easy_setopt(result, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
#endif

        if (ssl_cert != NULL)
                curl_easy_setopt(result, CURLOPT_SSLCERT, ssl_cert);
#if LIBCURL_VERSION_NUM >= 0x070902
        if (ssl_key != NULL)
                curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
        if (ssl_capath != NULL)
                curl_easy_setopt(result, CURLOPT_CAPATH, ssl_capath);
#endif
        if (ssl_cainfo != NULL)
                curl_easy_setopt(result, CURLOPT_CAINFO, ssl_cainfo);
        curl_easy_setopt(result, CURLOPT_FAILONERROR, 1);

        if (curl_low_speed_limit > 0 && curl_low_speed_time > 0) {
                curl_easy_setopt(result, CURLOPT_LOW_SPEED_LIMIT,
                                 curl_low_speed_limit);
                curl_easy_setopt(result, CURLOPT_LOW_SPEED_TIME,
                                 curl_low_speed_time);
        }

        curl_easy_setopt(result, CURLOPT_FOLLOWLOCATION, 1);

        return result;
}

static struct active_request_slot *get_active_slot(void)
{
        struct active_request_slot *slot = active_queue_head;
        struct active_request_slot *newslot;

#ifdef USE_CURL_MULTI
        int num_transfers;

        /* Wait for a slot to open up if the queue is full */
        while (active_requests >= max_requests) {
                curl_multi_perform(curlm, &num_transfers);
                if (num_transfers < active_requests) {
                        process_curl_messages();
                }
        }
#endif

        while (slot != NULL && slot->in_use) {
                slot = slot->next;
        }
        if (slot == NULL) {
                newslot = xmalloc(sizeof(*newslot));
                newslot->curl = NULL;
                newslot->in_use = 0;
                newslot->next = NULL;

                slot = active_queue_head;
                if (slot == NULL) {
                        active_queue_head = newslot;
                } else {
                        while (slot->next != NULL) {
                                slot = slot->next;
                        }
                        slot->next = newslot;
                }
                slot = newslot;
        }

        if (slot->curl == NULL) {
#ifdef NO_CURL_EASY_DUPHANDLE
                slot->curl = get_curl_handle();
#else
                slot->curl = curl_easy_duphandle(curl_default);
#endif
        }

        active_requests++;
        slot->in_use = 1;
        slot->done = 0;
        slot->local = NULL;
        slot->callback_data = NULL;
        slot->callback_func = NULL;
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, pragma_header);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_range_header);
        curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, curl_errorstr);

        return slot;
}

static int start_active_slot(struct active_request_slot *slot)
{
#ifdef USE_CURL_MULTI
        CURLMcode curlm_result = curl_multi_add_handle(curlm, slot->curl);

        if (curlm_result != CURLM_OK &&
            curlm_result != CURLM_CALL_MULTI_PERFORM) {
                active_requests--;
                slot->in_use = 0;
                return 0;
        }
#endif
        return 1;
}

static void run_active_slot(struct active_request_slot *slot)
{
#ifdef USE_CURL_MULTI
        int num_transfers;
        long last_pos = 0;
        long current_pos;
        fd_set readfds;
        fd_set writefds;
        fd_set excfds;
        int max_fd;
        struct timeval select_timeout;
        CURLMcode curlm_result;

        while (!slot->done) {
                data_received = 0;
                do {
                        curlm_result = curl_multi_perform(curlm,
                                                          &num_transfers);
                } while (curlm_result == CURLM_CALL_MULTI_PERFORM);
                if (num_transfers < active_requests) {
                        process_curl_messages();
                        process_request_queue();
                }

                if (!data_received && slot->local != NULL) {
                        current_pos = ftell(slot->local);
                        if (current_pos > last_pos)
                                data_received++;
                        last_pos = current_pos;
                }

                if (!slot->done && !data_received) {
                        max_fd = 0;
                        FD_ZERO(&readfds);
                        FD_ZERO(&writefds);
                        FD_ZERO(&excfds);
                        select_timeout.tv_sec = 0;
                        select_timeout.tv_usec = 50000;
                        select(max_fd, &readfds, &writefds,
                               &excfds, &select_timeout);
                }
        }
#else
        slot->curl_result = curl_easy_perform(slot->curl);
        active_requests--;
#endif
}

static void start_request(struct transfer_request *request)
{
        char *hex = sha1_to_hex(request->sha1);
        char prevfile[PATH_MAX];
        char *url;
        char *posn;
        int prevlocal;
        unsigned char prev_buf[PREV_BUF_SIZE];
        ssize_t prev_read = 0;
        long prev_posn = 0;
        char range[RANGE_HEADER_SIZE];
        struct curl_slist *range_header = NULL;
        struct active_request_slot *slot;

        snprintf(prevfile, sizeof(prevfile), "%s.prev", request->filename);
        unlink(prevfile);
        rename(request->tmpfile, prevfile);
        unlink(request->tmpfile);

        if (request->local != -1)
                error("fd leakage in start: %d", request->local);
        request->local = open(request->tmpfile,
                              O_WRONLY | O_CREAT | O_EXCL, 0666);
        /* This could have failed due to the "lazy directory creation";
         * try to mkdir the last path component.
         */
        if (request->local < 0 && errno == ENOENT) {
                char *dir = strrchr(request->tmpfile, '/');
                if (dir) {
                        *dir = 0;
                        mkdir(request->tmpfile, 0777);
                        *dir = '/';
                }
                request->local = open(request->tmpfile,
                                      O_WRONLY | O_CREAT | O_EXCL, 0666);
        }

        if (request->local < 0) {
                request->state = ABORTED;
                error("Couldn't create temporary file %s for %s: %s\n",
                      request->tmpfile, request->filename, strerror(errno));
                return;
        }

        memset(&request->stream, 0, sizeof(request->stream));

        inflateInit(&request->stream);

        SHA1_Init(&request->c);

        url = xmalloc(strlen(request->repo->base) + 50);
        request->url = xmalloc(strlen(request->repo->base) + 50);
        strcpy(url, request->repo->base);
        posn = url + strlen(request->repo->base);
        strcpy(posn, "objects/");
        posn += 8;
        memcpy(posn, hex, 2);
        posn += 2;
        *(posn++) = '/';
        strcpy(posn, hex + 2);
        strcpy(request->url, url);

        /* If a previous temp file is present, process what was already
           fetched. */
        prevlocal = open(prevfile, O_RDONLY);
        if (prevlocal != -1) {
                do {
                        prev_read = read(prevlocal, prev_buf, PREV_BUF_SIZE);
                        if (prev_read>0) {
                                if (fwrite_sha1_file(prev_buf,
                                                     1,
                                                     prev_read,
                                                     request) == prev_read) {
                                        prev_posn += prev_read;
                                } else {
                                        prev_read = -1;
                                }
                        }
                } while (prev_read > 0);
                close(prevlocal);
        }
        unlink(prevfile);

        /* Reset inflate/SHA1 if there was an error reading the previous temp
           file; also rewind to the beginning of the local file. */
        if (prev_read == -1) {
                memset(&request->stream, 0, sizeof(request->stream));
                inflateInit(&request->stream);
                SHA1_Init(&request->c);
                if (prev_posn>0) {
                        prev_posn = 0;
                        lseek(request->local, SEEK_SET, 0);
                        ftruncate(request->local, 0);
                }
        }

        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_FILE, request);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
        curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, request->errorstr);
        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);

        /* If we have successfully processed data from a previous fetch
           attempt, only fetch the data we don't already have. */
        if (prev_posn>0) {
                if (get_verbosely)
                        fprintf(stderr,
                                "Resuming fetch of object %s at byte %ld\n",
                                hex, prev_posn);
                sprintf(range, "Range: bytes=%ld-", prev_posn);
                range_header = curl_slist_append(range_header, range);
                curl_easy_setopt(slot->curl,
                                 CURLOPT_HTTPHEADER, range_header);
        }

        /* Try to get the request started, abort the request on error */
        if (!start_active_slot(slot)) {
                request->state = ABORTED;
                close(request->local); request->local = -1;
                free(request->url);
                return;
        }
        
        request->slot = slot;
        request->state = ACTIVE;
}

static void finish_request(struct transfer_request *request)
{
        struct stat st;

        fchmod(request->local, 0444);
        close(request->local); request->local = -1;

        if (request->http_code == 416) {
                fprintf(stderr, "Warning: requested range invalid; we may already have all the data.\n");
        } else if (request->curl_result != CURLE_OK) {
                if (stat(request->tmpfile, &st) == 0)
                        if (st.st_size == 0)
                                unlink(request->tmpfile);
                return;
        }

        inflateEnd(&request->stream);
        SHA1_Final(request->real_sha1, &request->c);
        if (request->zret != Z_STREAM_END) {
                unlink(request->tmpfile);
                return;
        }
        if (memcmp(request->sha1, request->real_sha1, 20)) {
                unlink(request->tmpfile);
                return;
        }
        request->rename =
                move_temp_to_file(request->tmpfile, request->filename);

        if (request->rename == 0)
                pull_say("got %s\n", sha1_to_hex(request->sha1));
}

static void release_request(struct transfer_request *request)
{
        struct transfer_request *entry = request_queue_head;

        if (request->local != -1)
                error("fd leakage in release: %d", request->local);
        if (request == request_queue_head) {
                request_queue_head = request->next;
        } else {
                while (entry->next != NULL && entry->next != request)
                        entry = entry->next;
                if (entry->next == request)
                        entry->next = entry->next->next;
        }

        free(request->url);
        free(request);
}

#ifdef USE_CURL_MULTI
static void process_curl_messages(void)
{
        int num_messages;
        struct active_request_slot *slot;
        struct transfer_request *request = NULL;
        CURLMsg *curl_message = curl_multi_info_read(curlm, &num_messages);

        while (curl_message != NULL) {
                if (curl_message->msg == CURLMSG_DONE) {
                        int curl_result = curl_message->data.result;
                        slot = active_queue_head;
                        while (slot != NULL &&
                               slot->curl != curl_message->easy_handle)
                                slot = slot->next;
                        if (slot != NULL) {
                                curl_multi_remove_handle(curlm, slot->curl);
                                active_requests--;
                                slot->done = 1;
                                slot->in_use = 0;
                                slot->curl_result = curl_result;
                                curl_easy_getinfo(slot->curl,
                                                  CURLINFO_HTTP_CODE,
                                                  &slot->http_code);
                                request = request_queue_head;
                                while (request != NULL &&
                                       request->slot != slot)
                                        request = request->next;
                        } else {
                                fprintf(stderr, "Received DONE message for unknown request!\n");
                        }

                        /* Process slot callback if appropriate */
                        if (slot->callback_func != NULL) {
                                slot->callback_func(slot->callback_data);
                        }

                        if (request != NULL) {
                                request->curl_result = curl_result;
                                request->http_code = slot->http_code;
                                request->slot = NULL;
                                request->state = COMPLETE;

                                /* Use alternates if necessary */
                                if (request->http_code == 404) {
                                        fetch_alternates(alt->base);
                                        if (request->repo->next != NULL) {
                                                request->repo =
                                                        request->repo->next;
                                                close(request->local);
                                                        request->local = -1;
                                                start_request(request);
                                        } else {
                                                finish_request(request);
                                        }
                                } else {
                                        finish_request(request);
                                }
                        }
                } else {
                        fprintf(stderr, "Unknown CURL message received: %d\n",
                                (int)curl_message->msg);
                }
                curl_message = curl_multi_info_read(curlm, &num_messages);
        }
}

static void process_request_queue(void)
{
        struct transfer_request *request = request_queue_head;
        struct active_request_slot *slot = active_queue_head;
        int num_transfers;

        while (active_requests < max_requests && request != NULL) {
                if (request->state == WAITING) {
                        if (has_sha1_file(request->sha1))
                                release_request(request);
                        else
                                start_request(request);
                        curl_multi_perform(curlm, &num_transfers);
                }
                request = request->next;
        }

        while (slot != NULL) {
                if (!slot->in_use && slot->curl != NULL) {
                        curl_easy_cleanup(slot->curl);
                        slot->curl = NULL;
                }
                slot = slot->next;
        }                               
}
#endif

void prefetch(unsigned char *sha1)
{
        struct transfer_request *newreq;
        struct transfer_request *tail;
        char *filename = sha1_file_name(sha1);

        newreq = xmalloc(sizeof(*newreq));
        memcpy(newreq->sha1, sha1, 20);
        newreq->repo = alt;
        newreq->url = NULL;
        newreq->local = -1;
        newreq->state = WAITING;
        snprintf(newreq->filename, sizeof(newreq->filename), "%s", filename);
        snprintf(newreq->tmpfile, sizeof(newreq->tmpfile),
                 "%s.temp", filename);
        newreq->next = NULL;

        if (request_queue_head == NULL) {
                request_queue_head = newreq;
        } else {
                tail = request_queue_head;
                while (tail->next != NULL) {
                        tail = tail->next;
                }
                tail->next = newreq;
        }
#ifdef USE_CURL_MULTI
        process_request_queue();
        process_curl_messages();
#endif
}

static int fetch_index(struct alt_base *repo, unsigned char *sha1)
{
        char *hex = sha1_to_hex(sha1);
        char *filename;
        char *url;
        char tmpfile[PATH_MAX];
        long prev_posn = 0;
        char range[RANGE_HEADER_SIZE];
        struct curl_slist *range_header = NULL;

        FILE *indexfile;
        struct active_request_slot *slot;

        if (has_pack_index(sha1))
                return 0;

        if (get_verbosely)
                fprintf(stderr, "Getting index for pack %s\n", hex);
        
        url = xmalloc(strlen(repo->base) + 64);
        sprintf(url, "%s/objects/pack/pack-%s.idx", repo->base, hex);
        
        filename = sha1_pack_index_name(sha1);
        snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
        indexfile = fopen(tmpfile, "a");
        if (!indexfile)
                return error("Unable to open local file %s for pack index",
                             filename);

        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_FILE, indexfile);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
        slot->local = indexfile;

        /* If there is data present from a previous transfer attempt,
           resume where it left off */
        prev_posn = ftell(indexfile);
        if (prev_posn>0) {
                if (get_verbosely)
                        fprintf(stderr,
                                "Resuming fetch of index for pack %s at byte %ld\n",
                                hex, prev_posn);
                sprintf(range, "Range: bytes=%ld-", prev_posn);
                range_header = curl_slist_append(range_header, range);
                curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
        }

        if (start_active_slot(slot)) {
                run_active_slot(slot);
                if (slot->curl_result != CURLE_OK) {
                        fclose(indexfile);
                        return error("Unable to get pack index %s\n%s", url,
                                     curl_errorstr);
                }
        } else {
                fclose(indexfile);
                return error("Unable to start request");
        }

        fclose(indexfile);

        return move_temp_to_file(tmpfile, filename);
}

static int setup_index(struct alt_base *repo, unsigned char *sha1)
{
        struct packed_git *new_pack;
        if (has_pack_file(sha1))
                return 0; // don't list this as something we can get

        if (fetch_index(repo, sha1))
                return -1;

        new_pack = parse_pack_index(sha1);
        new_pack->next = repo->packs;
        repo->packs = new_pack;
        return 0;
}

static void process_alternates(void *callback_data)
{
        struct alt_request *alt_req = (struct alt_request *)callback_data;
        struct active_request_slot *slot = alt_req->slot;
        struct alt_base *tail = alt;
        char *base = alt_req->base;
        static const char null_byte = '\0';
        char *data;
        int i = 0;

        if (alt_req->http_specific) {
                if (slot->curl_result != CURLE_OK ||
                    !alt_req->buffer->posn) {

                        /* Try reusing the slot to get non-http alternates */
                        alt_req->http_specific = 0;
                        sprintf(alt_req->url, "%s/objects/info/alternates",
                                base);
                        curl_easy_setopt(slot->curl, CURLOPT_URL,
                                         alt_req->url);
                        active_requests++;
                        slot->in_use = 1;
                        slot->done = 0;
                        if (start_active_slot(slot)) {
                                return;
                        } else {
                                got_alternates = -1;
                                slot->done = 1;
                                return;
                        }
                }
        } else if (slot->curl_result != CURLE_OK) {
                if (slot->http_code != 404) {
                        got_alternates = -1;
                        return;
                }
        }

        fwrite_buffer_dynamic(&null_byte, 1, 1, alt_req->buffer);
        alt_req->buffer->posn--;
        data = alt_req->buffer->buffer;

        while (i < alt_req->buffer->posn) {
                int posn = i;
                while (posn < alt_req->buffer->posn && data[posn] != '\n')
                        posn++;
                if (data[posn] == '\n') {
                        int okay = 0;
                        int serverlen = 0;
                        struct alt_base *newalt;
                        char *target = NULL;
                        if (data[i] == '/') {
                                serverlen = strchr(base + 8, '/') - base;
                                okay = 1;
                        } else if (!memcmp(data + i, "../", 3)) {
                                i += 3;
                                serverlen = strlen(base);
                                while (i + 2 < posn && 
                                       !memcmp(data + i, "../", 3)) {
                                        do {
                                                serverlen--;
                                        } while (serverlen &&
                                                 base[serverlen - 1] != '/');
                                        i += 3;
                                }
                                // If the server got removed, give up.
                                okay = strchr(base, ':') - base + 3 < 
                                        serverlen;
                        } else if (alt_req->http_specific) {
                                char *colon = strchr(data + i, ':');
                                char *slash = strchr(data + i, '/');
                                if (colon && slash && colon < data + posn &&
                                    slash < data + posn && colon < slash) {
                                        okay = 1;
                                }
                        }
                        // skip 'objects' at end
                        if (okay) {
                                target = xmalloc(serverlen + posn - i - 6);
                                strncpy(target, base, serverlen);
                                strncpy(target + serverlen, data + i,
                                        posn - i - 7);
                                target[serverlen + posn - i - 7] = '\0';
                                if (get_verbosely)
                                        fprintf(stderr, 
                                                "Also look at %s\n", target);
                                newalt = xmalloc(sizeof(*newalt));
                                newalt->next = NULL;
                                newalt->base = target;
                                newalt->got_indices = 0;
                                newalt->packs = NULL;
                                while (tail->next != NULL)
                                        tail = tail->next;
                                tail->next = newalt;
                        }
                }
                i = posn + 1;
        }

        got_alternates = 1;
}

static void fetch_alternates(char *base)
{
        struct buffer buffer;
        char *url;
        char *data;
        struct active_request_slot *slot;
        static struct alt_request alt_req;
        int num_transfers;

        /* If another request has already started fetching alternates,
           wait for them to arrive and return to processing this request's
           curl message */
        while (got_alternates == 0) {
                curl_multi_perform(curlm, &num_transfers);
                process_curl_messages();
                process_request_queue();
        }

        /* Nothing to do if they've already been fetched */
        if (got_alternates == 1)
                return;

        /* Start the fetch */
        got_alternates = 0;

        data = xmalloc(4096);
        buffer.size = 4096;
        buffer.posn = 0;
        buffer.buffer = data;

        if (get_verbosely)
                fprintf(stderr, "Getting alternates list for %s\n", base);
        
        url = xmalloc(strlen(base) + 31);
        sprintf(url, "%s/objects/info/http-alternates", base);

        /* Use a callback to process the result, since another request
           may fail and need to have alternates loaded before continuing */
        slot = get_active_slot();
        slot->callback_func = process_alternates;
        slot->callback_data = &alt_req;

        curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
                         fwrite_buffer_dynamic);
        curl_easy_setopt(slot->curl, CURLOPT_URL, url);

        alt_req.base = base;
        alt_req.url = url;
        alt_req.buffer = &buffer;
        alt_req.http_specific = 1;
        alt_req.slot = slot;

        if (start_active_slot(slot))
                run_active_slot(slot);
        else
                got_alternates = -1;

        free(data);
        free(url);
}

static int fetch_indices(struct alt_base *repo)
{
        unsigned char sha1[20];
        char *url;
        struct buffer buffer;
        char *data;
        int i = 0;

        struct active_request_slot *slot;

        if (repo->got_indices)
                return 0;

        data = xmalloc(4096);
        buffer.size = 4096;
        buffer.posn = 0;
        buffer.buffer = data;

        if (get_verbosely)
                fprintf(stderr, "Getting pack list for %s\n", repo->base);
        
        url = xmalloc(strlen(repo->base) + 21);
        sprintf(url, "%s/objects/info/packs", repo->base);

        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
                         fwrite_buffer_dynamic);
        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, NULL);
        if (start_active_slot(slot)) {
                run_active_slot(slot);
                if (slot->curl_result != CURLE_OK) {
                        free(buffer.buffer);
                        return error("%s", curl_errorstr);
                }
        } else {
                free(buffer.buffer);
                return error("Unable to start request");
        }

        data = buffer.buffer;
        while (i < buffer.posn) {
                switch (data[i]) {
                case 'P':
                        i++;
                        if (i + 52 < buffer.posn &&
                            !strncmp(data + i, " pack-", 6) &&
                            !strncmp(data + i + 46, ".pack\n", 6)) {
                                get_sha1_hex(data + i + 6, sha1);
                                setup_index(repo, sha1);
                                i += 51;
                                break;
                        }
                default:
                        while (data[i] != '\n')
                                i++;
                }
                i++;
        }

        free(buffer.buffer);
        repo->got_indices = 1;
        return 0;
}

static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
{
        char *url;
        struct packed_git *target;
        struct packed_git **lst;
        FILE *packfile;
        char *filename;
        char tmpfile[PATH_MAX];
        int ret;
        long prev_posn = 0;
        char range[RANGE_HEADER_SIZE];
        struct curl_slist *range_header = NULL;

        struct active_request_slot *slot;

        if (fetch_indices(repo))
                return -1;
        target = find_sha1_pack(sha1, repo->packs);
        if (!target)
                return -1;

        if (get_verbosely) {
                fprintf(stderr, "Getting pack %s\n",
                        sha1_to_hex(target->sha1));
                fprintf(stderr, " which contains %s\n",
                        sha1_to_hex(sha1));
        }

        url = xmalloc(strlen(repo->base) + 65);
        sprintf(url, "%s/objects/pack/pack-%s.pack",
                repo->base, sha1_to_hex(target->sha1));

        filename = sha1_pack_name(target->sha1);
        snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
        packfile = fopen(tmpfile, "a");
        if (!packfile)
                return error("Unable to open local file %s for pack",
                             filename);

        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_FILE, packfile);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
        slot->local = packfile;

        /* If there is data present from a previous transfer attempt,
           resume where it left off */
        prev_posn = ftell(packfile);
        if (prev_posn>0) {
                if (get_verbosely)
                        fprintf(stderr,
                                "Resuming fetch of pack %s at byte %ld\n",
                                sha1_to_hex(target->sha1), prev_posn);
                sprintf(range, "Range: bytes=%ld-", prev_posn);
                range_header = curl_slist_append(range_header, range);
                curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
        }

        if (start_active_slot(slot)) {
                run_active_slot(slot);
                if (slot->curl_result != CURLE_OK) {
                        fclose(packfile);
                        return error("Unable to get pack file %s\n%s", url,
                                     curl_errorstr);
                }
        } else {
                fclose(packfile);
                return error("Unable to start request");
        }

        fclose(packfile);

        ret = move_temp_to_file(tmpfile, filename);
        if (ret)
                return ret;

        lst = &repo->packs;
        while (*lst != target)
                lst = &((*lst)->next);
        *lst = (*lst)->next;

        if (verify_pack(target, 0))
                return -1;
        install_packed_git(target);

        return 0;
}

static int fetch_object(struct alt_base *repo, unsigned char *sha1)
{
        char *hex = sha1_to_hex(sha1);
        int ret;
        struct transfer_request *request = request_queue_head;

        while (request != NULL && memcmp(request->sha1, sha1, 20))
                request = request->next;
        if (request == NULL)
                return error("Couldn't find request for %s in the queue", hex);

        if (has_sha1_file(request->sha1)) {
                release_request(request);
                return 0;
        }

#ifdef USE_CURL_MULTI
        while (request->state == WAITING) {
                int num_transfers;
                curl_multi_perform(curlm, &num_transfers);
                if (num_transfers < active_requests) {
                        process_curl_messages();
                        process_request_queue();
                }
        }
#else
        start_request(request);
#endif

        while (request->state == ACTIVE) {
                run_active_slot(request->slot);
#ifndef USE_CURL_MULTI
                request->curl_result = request->slot->curl_result;
                request->http_code = request->slot->http_code;
                request->slot = NULL;

                /* Use alternates if necessary */
                if (request->http_code == 404) {
                        fetch_alternates(alt->base);
                        if (request->repo->next != NULL) {
                                request->repo = request->repo->next;
                                close(request->local); request->local = -1;
                                start_request(request);
                        }
                } else {
                        finish_request(request);
                        request->state = COMPLETE;
                }
#endif
        }
        if (request->local != -1) {
                close(request->local); request->local = -1;
        }

        if (request->state == ABORTED) {
                release_request(request);
                return error("Request for %s aborted", hex);
        }

        if (request->curl_result != CURLE_OK && request->http_code != 416) {
                if (request->http_code == 404)
                        ret = -1; /* Be silent, it is probably in a pack. */
                else
                        ret = error("%s (curl_result = %d, http_code = %ld, sha1 = %s)",
                                    request->errorstr, request->curl_result,
                                    request->http_code, hex);
                release_request(request);
                return ret;
        }

        if (request->zret != Z_STREAM_END) {
                ret = error("File %s (%s) corrupt\n", hex, request->url);
                release_request(request);
                return ret;
        }

        if (memcmp(request->sha1, request->real_sha1, 20)) {
                release_request(request);
                return error("File %s has bad hash\n", hex);
        }

        if (request->rename < 0) {
                ret = error("unable to write sha1 filename %s: %s",
                            request->filename,
                            strerror(request->rename));
                release_request(request);
                return ret;
        }

        release_request(request);
        return 0;
}

int fetch(unsigned char *sha1)
{
        struct alt_base *altbase = alt;

        if (!fetch_object(altbase, sha1))
                return 0;
        while (altbase) {
                if (!fetch_pack(altbase, sha1))
                        return 0;
                fetch_alternates(alt->base);
                altbase = altbase->next;
        }
        return error("Unable to find %s under %s\n", sha1_to_hex(sha1), 
                     alt->base);
}

static inline int needs_quote(int ch)
{
        switch (ch) {
        case '/': case '-': case '.':
        case 'A'...'Z': case 'a'...'z': case '0'...'9':
                return 0;
        default:
                return 1;
        }
}

static inline int hex(int v)
{
        if (v < 10) return '0' + v;
        else return 'A' + v - 10;
}

static char *quote_ref_url(const char *base, const char *ref)
{
        const char *cp;
        char *dp, *qref;
        int len, baselen, ch;

        baselen = strlen(base);
        len = baselen + 6; /* "refs/" + NUL */
        for (cp = ref; (ch = *cp) != 0; cp++, len++)
                if (needs_quote(ch))
                        len += 2; /* extra two hex plus replacement % */
        qref = xmalloc(len);
        memcpy(qref, base, baselen);
        memcpy(qref + baselen, "refs/", 5);
        for (cp = ref, dp = qref + baselen + 5; (ch = *cp) != 0; cp++) {
                if (needs_quote(ch)) {
                        *dp++ = '%';
                        *dp++ = hex((ch >> 4) & 0xF);
                        *dp++ = hex(ch & 0xF);
                }
                else
                        *dp++ = ch;
        }
        *dp = 0;

        return qref;
}

int fetch_ref(char *ref, unsigned char *sha1)
{
        char *url;
        char hex[42];
        struct buffer buffer;
        char *base = alt->base;
        struct active_request_slot *slot;
        buffer.size = 41;
        buffer.posn = 0;
        buffer.buffer = hex;
        hex[41] = '\0';
        
        url = quote_ref_url(base, ref);
        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        if (start_active_slot(slot)) {
                run_active_slot(slot);
                if (slot->curl_result != CURLE_OK)
                        return error("Couldn't get %s for %s\n%s",
                                     url, ref, curl_errorstr);
        } else {
                return error("Unable to start request");
        }

        hex[40] = '\0';
        get_sha1_hex(hex, sha1);
        return 0;
}

int main(int argc, char **argv)
{
        char *commit_id;
        char *url;
        int arg = 1;
        struct active_request_slot *slot;
        char *low_speed_limit;
        char *low_speed_time;
        char *wait_url;
        int rc = 0;

        while (arg < argc && argv[arg][0] == '-') {
                if (argv[arg][1] == 't') {
                        get_tree = 1;
                } else if (argv[arg][1] == 'c') {
                        get_history = 1;
                } else if (argv[arg][1] == 'a') {
                        get_all = 1;
                        get_tree = 1;
                        get_history = 1;
                } else if (argv[arg][1] == 'v') {
                        get_verbosely = 1;
                } else if (argv[arg][1] == 'w') {
                        write_ref = argv[arg + 1];
                        arg++;
                } else if (!strcmp(argv[arg], "--recover")) {
                        get_recover = 1;
                }
                arg++;
        }
        if (argc < arg + 2) {
                usage("git-http-fetch [-c] [-t] [-a] [-d] [-v] [--recover] [-w ref] commit-id url");
                return 1;
        }
        commit_id = argv[arg];
        url = argv[arg + 1];

        curl_global_init(CURL_GLOBAL_ALL);

#ifdef USE_CURL_MULTI
        {
                char *http_max_requests = getenv("GIT_HTTP_MAX_REQUESTS");
                if (http_max_requests != NULL)
                        max_requests = atoi(http_max_requests);
        }

        curlm = curl_multi_init();
        if (curlm == NULL) {
                fprintf(stderr, "Error creating curl multi handle.\n");
                return 1;
        }
#endif

        if (getenv("GIT_SSL_NO_VERIFY"))
                curl_ssl_verify = 0;

        ssl_cert = getenv("GIT_SSL_CERT");
#if LIBCURL_VERSION_NUM >= 0x070902
        ssl_key = getenv("GIT_SSL_KEY");
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
        ssl_capath = getenv("GIT_SSL_CAPATH");
#endif
        ssl_cainfo = getenv("GIT_SSL_CAINFO");

        low_speed_limit = getenv("GIT_HTTP_LOW_SPEED_LIMIT");
        if (low_speed_limit != NULL)
                curl_low_speed_limit = strtol(low_speed_limit, NULL, 10);
        low_speed_time = getenv("GIT_HTTP_LOW_SPEED_TIME");
        if (low_speed_time != NULL)
                curl_low_speed_time = strtol(low_speed_time, NULL, 10);

        git_config(http_options);

        if (curl_ssl_verify == -1)
                curl_ssl_verify = 1;

#ifdef USE_CURL_MULTI
        if (max_requests < 1)
                max_requests = DEFAULT_MAX_REQUESTS;
#endif

        pragma_header = curl_slist_append(pragma_header, "Pragma: no-cache");
        no_pragma_header = curl_slist_append(no_pragma_header, "Pragma:");
        no_range_header = curl_slist_append(no_range_header, "Range:");

#ifndef NO_CURL_EASY_DUPHANDLE
        curl_default = get_curl_handle();
#endif

        alt = xmalloc(sizeof(*alt));
        alt->base = url;
        alt->got_indices = 0;
        alt->packs = NULL;
        alt->next = NULL;

        if (pull(commit_id))
                rc = 1;

        curl_slist_free_all(pragma_header);
        curl_slist_free_all(no_pragma_header);
        curl_slist_free_all(no_range_header);
#ifndef NO_CURL_EASY_DUPHANDLE
        curl_easy_cleanup(curl_default);
#endif
        slot = active_queue_head;
        while (slot != NULL) {
                if (slot->in_use) {
                        if (get_verbosely) {
                                curl_easy_getinfo(slot->curl,
                                                  CURLINFO_EFFECTIVE_URL,
                                                  &wait_url);
                                fprintf(stderr, "Waiting for %s\n", wait_url);
                        }
                        run_active_slot(slot);
                }
                if (slot->curl != NULL)
                        curl_easy_cleanup(slot->curl);
                slot = slot->next;
        }
#ifdef USE_CURL_MULTI
        curl_multi_cleanup(curlm);
#endif
        curl_global_cleanup();
        return rc;
}