#include "cache.h"
#include "refs.h"
#include "pkt-line.h"
#include <sys/wait.h>

static const char receive_pack_usage[] = "git-receive-pack <git-dir>";

static const char *unpacker = "git-unpack-objects";

static int show_ref(const char *path, const unsigned char *sha1)
{
        packet_write(1, "%s %s\n", sha1_to_hex(sha1), path);
        return 0;
}

static void write_head_info(void)
{
        for_each_ref(show_ref);
}

struct command {
        struct command *next;
        unsigned char old_sha1[20];
        unsigned char new_sha1[20];
        char ref_name[0];
};

static struct command *commands = NULL;

static int is_all_zeroes(const char *hex)
{
        int i;
        for (i = 0; i < 40; i++)
                if (*hex++ != '0')
                        return 0;
        return 1;
}

static int verify_old_ref(const char *name, char *hex_contents)
{
        int fd, ret;
        char buffer[60];

        if (is_all_zeroes(hex_contents))
                return 0;
        fd = open(name, O_RDONLY);
        if (fd < 0)
                return -1;
        ret = read(fd, buffer, 40);
        close(fd);
        if (ret != 40)
                return -1;
        if (memcmp(buffer, hex_contents, 40))
                return -1;
        return 0;
}

static void update(const char *name, unsigned char *old_sha1, unsigned char *new_sha1)
{
        char new_hex[60], *old_hex, *lock_name;
        int newfd, namelen, written;

        namelen = strlen(name);
        lock_name = xmalloc(namelen + 10);
        memcpy(lock_name, name, namelen);
        memcpy(lock_name + namelen, ".lock", 6);

        strcpy(new_hex, sha1_to_hex(new_sha1));
        old_hex = sha1_to_hex(old_sha1);
        if (!has_sha1_file(new_sha1))
                die("unpack should have generated %s, but I can't find it!", new_hex);

        newfd = open(lock_name, O_CREAT | O_EXCL | O_WRONLY, 0666);
        if (newfd < 0)
                die("unable to create %s (%s)", lock_name, strerror(errno));

        /* Write the ref with an ending '\n' */
        new_hex[40] = '\n';
        new_hex[41] = 0;
        written = write(newfd, new_hex, 41);
        /* Remove the '\n' again */
        new_hex[40] = 0;

        close(newfd);
        if (written != 41) {
                unlink(lock_name);
                die("unable to write %s", lock_name);
        }
        if (verify_old_ref(name, old_hex) < 0) {
                unlink(lock_name);
                die("%s changed during push", name);
        }
        if (rename(lock_name, name) < 0) {
                unlink(lock_name);
                die("unable to replace %s", name);
        }
        fprintf(stderr, "%s: %s -> %s\n", name, old_hex, new_hex);
}


/*
 * This gets called after(if) we've successfully
 * unpacked the data payload.
 */
static void execute_commands(void)
{
        struct command *cmd = commands;

        while (cmd) {
                update(cmd->ref_name, cmd->old_sha1, cmd->new_sha1);
                cmd = cmd->next;
        }
}

static void read_head_info(void)
{
        struct command **p = &commands;
        for (;;) {
                static char line[1000];
                unsigned char old_sha1[20], new_sha1[20];
                struct command *cmd;
                int len;

                len = packet_read_line(0, line, sizeof(line));
                if (!len)
                        break;
                if (line[len-1] == '\n')
                        line[--len] = 0;
                if (len < 83 ||
                    line[40] != ' ' ||
                    line[81] != ' ' ||
                    get_sha1_hex(line, old_sha1) ||
                    get_sha1_hex(line + 41, new_sha1))
                        die("protocol error: expected old/new/ref, got '%s'", line);
                cmd = xmalloc(sizeof(struct command) + len - 80);
                memcpy(cmd->old_sha1, old_sha1, 20);
                memcpy(cmd->new_sha1, new_sha1, 20);
                memcpy(cmd->ref_name, line + 82, len - 81);
                cmd->next = NULL;
                *p = cmd;
                p = &cmd->next;
        }
}

static void unpack(void)
{
        pid_t pid = fork();

        if (pid < 0)
                die("unpack fork failed");
        if (!pid) {
                execlp(unpacker, unpacker, NULL);
                die("unpack execute failed");
        }

        for (;;) {
                int status, code;
                int retval = waitpid(pid, &status, 0);

                if (retval < 0) {
                        if (errno == EINTR)
                                continue;
                        die("waitpid failed (%s)", strerror(retval));
                }
                if (retval != pid)
                        die("waitpid is confused");
                if (WIFSIGNALED(status))
                        die("%s died of signal %d", unpacker, WTERMSIG(status));
                if (!WIFEXITED(status))
                        die("%s died out of really strange complications", unpacker);
                code = WEXITSTATUS(status);
                if (code)
                        die("%s exited with error code %d", unpacker, code);
                return;
        }
}

int main(int argc, char **argv)
{
        int i;
        const char *dir = NULL;

        argv++;
        for (i = 1; i < argc; i++) {
                const char *arg = *argv++;

                if (*arg == '-') {
                        /* Do flag handling here */
                        usage(receive_pack_usage);
                }
                if (dir)
                        usage(receive_pack_usage);
                dir = arg;
        }
        if (!dir)
                usage(receive_pack_usage);

        /* chdir to the directory. If that fails, try appending ".git" */
        if (chdir(dir) < 0) {
                if (chdir(mkpath("%s.git", dir)) < 0)
                        die("unable to cd to %s", dir);
        }

        /* If we have a ".git" directory, chdir to it */
        chdir(".git");
        setenv("GIT_DIR", ".", 1);

        if (access("objects", X_OK) < 0 || access("refs/heads", X_OK) < 0)
                die("%s doesn't appear to be a git directory", dir);
        write_head_info();

        /* EOF */
        packet_flush(1);

        read_head_info();
        if (commands) {
                unpack();
                execute_commands();
        }
        return 0;
}