/* Copyright (C) 2011 Jeff Epler <jepler@unpythonic.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>

#define streq(a,b) (strcmp((a),(b)) == 0)

char *read_file(char *name, char **end, time_t *mtime) {
    int f = open(name, O_RDONLY);
    int sz;
    struct stat st;
    if(f == -1) { perror(name); return 0; }
    fstat(f, &st);
    char *result = malloc(st.st_size+1);
    size_t bytes_read = read(f, result, st.st_size);
    if(bytes_read != st.st_size) {
        free(result);
        return 0;
    }
    result[bytes_read] = 0;
    *end = result + bytes_read;
    *mtime = st.st_mtime;
    fprintf(stderr, "read=%zd mtime=%ld\n", bytes_read, (long)st.st_mtime);
    return result;
}

char *strip(char *s, int ch) {
    if(!s) return NULL;
    while(*s == ch) s++;
    char *t = s + strlen(s) - 1;
    while(t > s && *t == ch) *t = 0;
    return s;
}

int cache_valid(char **dptr, time_t deptime) {
    char *REQUEST_METHOD = getenv("REQUEST_METHOD");
    char *QUERY_STRING = getenv("QUERY_STRING");
    if(QUERY_STRING && strlen(QUERY_STRING)) return 0;
    if(!REQUEST_METHOD) return 0;

    if(strcmp(REQUEST_METHOD, "GET") && strcmp(REQUEST_METHOD, "HEAD")) return 0;

    struct stat st;
    if(!*dptr) return 0;

    char *dep = *dptr;
    while(*dep) {
        if(stat(dep, &st) != 0) {
            fprintf(stderr, "stat %s -> %s\n", dep, strerror(errno));
            return 0;
        }
        if(st.st_mtime > deptime) {
            fprintf(stderr, "mtime %s %ld > %ld\n", dep, (long)st.st_mtime, (long)deptime);
            return 0;
        }
        dep = dep + strlen(dep) + 1;
    }
    *dptr = dep + 1;
    return 1;
}

int main(int argc, char **argv) {
    char *PATH_INFO   = getenv("PATH_INFO");
    char *REQUEST_METHOD = getenv("REQUEST_METHOD");
    char *real_script = getenv("REAL_SCRIPT");

    char *cache;
    if(!PATH_INFO) PATH_INFO = strdup("");
    PATH_INFO = strip(PATH_INFO, '/');
    
    asprintf(&cache, "%s-cache/%s/_cache", real_script, PATH_INFO);

    time_t mtime;
    char *end;
    char *data = read_file(cache, &end, &mtime);

    if(cache_valid(&data, mtime)) {
        fprintf(stderr, "Using cache %s\n", cache);
        if(streq(REQUEST_METHOD, "HEAD")) {
            end = strstr(data, "\n\n");
        }
        while(end != data) {
            ssize_t r = write(1, data, end-data);
            if(r < 0) {
                perror("write");
                break;
            }
            data += r;
        }
    } else {
        // unlink(cache);
        argv[0] = real_script;
        execv(real_script, argv);
    }
}