/* This file is in the public domain. */

static const char *userlist = "/etc/mailshim-userlist";

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/stat.h>

#include "validaddr.h"

typedef struct user USER;

struct user {
  USER *link;
  unsigned int hash;
  int nlen;
  char name[0];
  } ;

static int nusers = -1;
static int tblsize = 0;
static USER **table = 0;

static struct stat file_stb;

static void free_user_list(USER **lp)
{
 USER *u;

 while ((u = *lp))
  { *lp = u->link;
    free(u);
  }
}

static unsigned int hash_block(const void *data, int len)
{
 unsigned int h;
 int i;

 h = len;
 for (i=0;i<len;i++) h = (h >> 1) ^ ((h&1) ? 0xedb88320 : 0) ^ (((const unsigned char *)data)[i] | 0x20);
 return(h);
}

static void grow_table(void)
{
 int newsize;
 USER **newtbl;
 USER *u;
 int i;
 int b;

 newsize = (tblsize?:32) << 1;
 newtbl = malloc(newsize*sizeof(USER *));
 for (i=0;i<newsize;i++) newtbl[i] = 0;
 for (i=0;i<tblsize;i++)
  { while ((u = table[i]))
     { table[i] = u->link;
       b = u->hash % newsize;
       u->link = newtbl[b];
       newtbl[b] = u;
     }
  }
 free(table);
 table = newtbl;
 tblsize = newsize;
}

static int reload_users(void)
{
 FILE *f;
 int ll;
 USER *u;
 int bucket;
 int i;
 char line[1024];

 for (i=0;i<tblsize;i++) free_user_list(&table[i]);
 f = fopen(userlist,"r");
 if (f == 0)
  { nusers = -1;
    return(1);
  }
 fstat(fileno(f),&file_stb);
 nusers = 0;
 while (fgets(&line[0],sizeof(line),f))
  { ll = strlen(&line[0]);
    if ((ll > 0) && (line[ll-1] == '\n')) line[--ll] = '\0';
    u = malloc(sizeof(USER)+ll);
    u->nlen = ll;
    bcopy(&line[0],&u->name[0],ll);
    u->hash = hash_block(&line[0],ll);
    nusers ++;
    if (nusers > tblsize) grow_table();
    bucket = u->hash % tblsize;
    u->link = table[bucket];
    table[bucket] = u;
  }
 if (ferror(f))
  { fclose(f);
    nusers = -1;
    return(1);
  }
 fclose(f);
 return(0);
}

int valid_address(const char *lp, const char *dom)
{
 struct stat stb;
 unsigned int h;
 USER *u;
 int ll;

 /* If there's no domain part, it must be a bare <postmaster>. */
 if (dom == 0) return(VA_GOOD);
 /* The domain must be Example. */
 if (strcasecmp(dom,"example.net")) return(VA_BAD);
 /* Postmaster is always valid. */
 if (!strcasecmp(lp,"postmaster")) return(VA_GOOD);
 ll = strlen(lp);
 if (stat(userlist,&stb) < 0)
  { /* No user list? */
    return(VA_UNKNOWN);
  }
 if ( (nusers < 0) ||
      (stb.st_mtime != file_stb.st_mtime) ||
      (stb.st_dev != file_stb.st_dev) ||
      (stb.st_ino != file_stb.st_ino) )
  { if (reload_users()) return(VA_UNKNOWN);
  }
 if (nusers < 1)
  { /* *Still* no user list?! */
    return(VA_UNKNOWN);
  }
 h = hash_block(lp,ll);
 if (tblsize) for (u=table[h%tblsize];u;u=u->link) if ((u->hash == h) && (u->nlen == ll) && !strncasecmp(lp,u->name,ll)) return(VA_GOOD);
 return(VA_BAD);
}