#include "builtin.h"
#include "transport.h"
#include "run-command.h"

/*
 * URL syntax:
 *      'command [arg1 [arg2 [...]]]'   Invoke command with given arguments.
 *      Special characters:
 *      '% ': Literal space in argument.
 *      '%%': Literal percent sign.
 *      '%S': Name of service (git-upload-pack/git-upload-archive/
 *              git-receive-pack.
 *      '%s': Same as \s, but with possible git- prefix stripped.
 *      '%G': Only allowed as first 'character' of argument. Do not pass this
 *              Argument to command, instead send this as name of repository
 *              in in-line git://-style request (also activates sending this
 *              style of request).
 *      '%V': Only allowed as first 'character' of argument. Used in
 *              conjunction with '%G': Do not pass this argument to command,
 *              instead send this as vhost in git://-style request (note: does
 *              not activate sending git:// style request).
 */

static char *git_req;
static char *git_req_vhost;

static char *strip_escapes(const char *str, const char *service,
        const char **next)
{
        size_t rpos = 0;
        int escape = 0;
        char special = 0;
        size_t psoff = 0;
        struct strbuf ret = STRBUF_INIT;

        /* Calculate prefix length for \s and lengths for \s and \S */
        if (!strncmp(service, "git-", 4))
                psoff = 4;

        /* Pass the service to command. */
        setenv("GIT_EXT_SERVICE", service, 1);
        setenv("GIT_EXT_SERVICE_NOPREFIX", service + psoff, 1);

        /* Scan the length of argument. */
        while (str[rpos] && (escape || str[rpos] != ' ')) {
                if (escape) {
                        switch (str[rpos]) {
                        case ' ':
                        case '%':
                        case 's':
                        case 'S':
                                break;
                        case 'G':
                        case 'V':
                                special = str[rpos];
                                if (rpos == 1)
                                        break;
                                /* Fall-through to error. */
                        default:
                                die("Bad remote-ext placeholder '%%%c'.",
                                        str[rpos]);
                        }
                        escape = 0;
                } else
                        escape = (str[rpos] == '%');
                rpos++;
        }
        if (escape && !str[rpos])
                die("remote-ext command has incomplete placeholder");
        *next = str + rpos;
        if (**next == ' ')
                ++*next;        /* Skip over space */

        /*
         * Do the actual placeholder substitution. The string will be short
         * enough not to overflow integers.
         */
        rpos = special ? 2 : 0;         /* Skip first 2 bytes in specials. */
        escape = 0;
        while (str[rpos] && (escape || str[rpos] != ' ')) {
                if (escape) {
                        switch (str[rpos]) {
                        case ' ':
                        case '%':
                                strbuf_addch(&ret, str[rpos]);
                                break;
                        case 's':
                                strbuf_addstr(&ret, service + psoff);
                                break;
                        case 'S':
                                strbuf_addstr(&ret, service);
                                break;
                        }
                        escape = 0;
                } else
                        switch (str[rpos]) {
                        case '%':
                                escape = 1;
                                break;
                        default:
                                strbuf_addch(&ret, str[rpos]);
                                break;
                        }
                rpos++;
        }
        switch (special) {
        case 'G':
                git_req = strbuf_detach(&ret, NULL);
                return NULL;
        case 'V':
                git_req_vhost = strbuf_detach(&ret, NULL);
                return NULL;
        default:
                return strbuf_detach(&ret, NULL);
        }
}

/* Should be enough... */
#define MAXARGUMENTS 256

static const char **parse_argv(const char *arg, const char *service)
{
        int arguments = 0;
        int i;
        const char **ret;
        char *temparray[MAXARGUMENTS + 1];

        while (*arg) {
                char *expanded;
                if (arguments == MAXARGUMENTS)
                        die("remote-ext command has too many arguments");
                expanded = strip_escapes(arg, service, &arg);
                if (expanded)
                        temparray[arguments++] = expanded;
        }

        ret = xmalloc((arguments + 1) * sizeof(char *));
        for (i = 0; i < arguments; i++)
                ret[i] = temparray[i];
        ret[arguments] = NULL;
        return ret;
}

static void send_git_request(int stdin_fd, const char *serv, const char *repo,
        const char *vhost)
{
        size_t bufferspace;
        size_t wpos = 0;
        char *buffer;

        /*
         * Request needs 12 bytes extra if there is vhost (xxxx \0host=\0) and
         * 6 bytes extra (xxxx \0) if there is no vhost.
         */
        if (vhost)
                bufferspace = strlen(serv) + strlen(repo) + strlen(vhost) + 12;
        else
                bufferspace = strlen(serv) + strlen(repo) + 6;

        if (bufferspace > 0xFFFF)
                die("Request too large to send");
        buffer = xmalloc(bufferspace);

        /* Make the packet. */
        wpos = sprintf(buffer, "%04x%s %s%c", (unsigned)bufferspace,
                serv, repo, 0);

        /* Add vhost if any. */
        if (vhost)
                sprintf(buffer + wpos, "host=%s%c", vhost, 0);

        /* Send the request */
        if (write_in_full(stdin_fd, buffer, bufferspace) < 0)
                die_errno("Failed to send request");

        free(buffer);
}

static int run_child(const char *arg, const char *service)
{
        int r;
        struct child_process child;

        memset(&child, 0, sizeof(child));
        child.in = -1;
        child.out = -1;
        child.err = 0;
        child.argv = parse_argv(arg, service);

        if (start_command(&child) < 0)
                die("Can't run specified command");

        if (git_req)
                send_git_request(child.in, service, git_req, git_req_vhost);

        r = bidirectional_transfer_loop(child.out, child.in);
        if (!r)
                r = finish_command(&child);
        else
                finish_command(&child);
        return r;
}

#define MAXCOMMAND 4096

static int command_loop(const char *child)
{
        char buffer[MAXCOMMAND];

        while (1) {
                size_t i;
                if (!fgets(buffer, MAXCOMMAND - 1, stdin)) {
                        if (ferror(stdin))
                                die("Comammand input error");
                        exit(0);
                }
                /* Strip end of line characters. */
                i = strlen(buffer);
                while (i > 0 && isspace(buffer[i - 1]))
                        buffer[--i] = 0;

                if (!strcmp(buffer, "capabilities")) {
                        printf("*connect\n\n");
                        fflush(stdout);
                } else if (!strncmp(buffer, "connect ", 8)) {
                        printf("\n");
                        fflush(stdout);
                        return run_child(child, buffer + 8);
                } else {
                        fprintf(stderr, "Bad command");
                        return 1;
                }
        }
}

int cmd_remote_ext(int argc, const char **argv, const char *prefix)
{
        if (argc != 3)
                die("Expected two arguments");

        return command_loop(argv[2]);
}