/*
 * When commands are first encountered, they are entered in a hash table.
 * This ensures that a full path search will not have to be done for them
 * on each invocation.
 *
 * We should investigate converting to a linear search, even though that
 * would make the command name "hash" a misnomer.
 */

#include "shell.h"
#include "main.h"
#include "nodes.h"
#include "parser.h"
#include "redir.h"
#include "eval.h"
#include "exec.h"
#include "builtins.h"
#include "var.h"
#include "options.h"
#include "input.h"
#include "output.h"
#include "syntax.h"
#include "memalloc.h"
#include "error.h"
#include "init.h"
#include "mystring.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "myerrno.h"


#define CMDTABLESIZE 31		/* should be prime */
#define ARB 1			/* actual size determined at run time */



struct tblentry {
      struct tblentry *next;	/* next entry in hash chain */
      union param param;	/* definition of builtin function */
      short cmdtype;		/* index identifying command */
      char rehash;		/* if set, cd done since entry created */
      char cmdname[ARB];	/* name of command */
};


STATIC struct tblentry *cmdtable[CMDTABLESIZE];
STATIC int builtinloc;		/* index in path of %builtin, or -1 */


#ifdef __STDC__
STATIC void tryexec(char *, char **, char **);
STATIC void execinterp(char **, char **);
STATIC void printentry(struct tblentry *);
STATIC void clearcmdentry(int);
STATIC struct tblentry *cmdlookup(char *, int);
STATIC void delete_cmd_entry(void);
#else
STATIC void tryexec();
STATIC void execinterp();
STATIC void printentry();
STATIC void clearcmdentry();
STATIC struct tblentry *cmdlookup();
STATIC void delete_cmd_entry();
#endif



/*
 * Exec a program.  Never returns.  If you change this routine, you may
 * have to change the find_command routine as well.
 */

void
shellexec(argv, envp, path, index)
      char **argv, **envp;
      char *path;
      {
      char *cmdname;
      int e;

      if (strchr(argv[0], '/') != NULL) {
	    tryexec(argv[0], argv, envp);
	    e = errno;
      } else {
	    e = ENOENT;
	    while ((cmdname = padvance(&path, argv[0])) != NULL) {
		  if (--index < 0 && pathopt == NULL) {
			tryexec(cmdname, argv, envp);
			if (errno != ENOENT && errno != ENOTDIR)
			      e = errno;
		  }
		  stunalloc(cmdname);
	    }
      }
      error2(argv[0], errmsg(e, E_EXEC));
}


STATIC void
tryexec(cmd, argv, envp)
      char *cmd;
      char **argv;
      char **envp;
      {
      int e;
      char *p;

#ifdef SYSV
      do {
	    execve(cmd, argv, envp);
      } while (errno == EINTR);
#else
      execve(cmd, argv, envp);
#endif
      e = errno;
      if (e == ENOEXEC) {
	    initshellproc();
	    setinputfile(cmd, 0);
	    commandname = arg0 = savestr(argv[0]);
#ifndef BSD
	    pgetc(); pungetc();		/* fill up input buffer */
	    p = parsenextc;
	    if (parsenleft > 2 && p[0] == '#' && p[1] == '!') {
		  argv[0] = cmd;
		  execinterp(argv, envp);
	    }
#endif
	    setparam(argv + 1);
	    raise(EXSHELLPROC);
	    /*NOTREACHED*/
      }
      errno = e;
}


#ifndef BSD
/*
 * Execute an interpreter introduced by "#!", for systems where this
 * feature has not been built into the kernel.  If the interpreter is
 * the shell, return (effectively ignoring the "#!").  If the execution
 * of the interpreter fails, exit.
 *
 * This code peeks inside the input buffer in order to avoid actually
 * reading any input.  It would benefit from a rewrite.
 */

#define NEWARGS 5

STATIC void
execinterp(argv, envp)
      char **argv, **envp;
      {
      int n;
      char *inp;
      char *outp;
      char c;
      char *p;
      char **ap;
      char *newargs[NEWARGS];
      int i;
      char **ap2;
      char **new;

      n = parsenleft - 2;
      inp = parsenextc + 2;
      ap = newargs;
      for (;;) {
	    while (--n >= 0 && (*inp == ' ' || *inp == '\t'))
		  inp++;
	    if (n < 0)
		  goto bad;
	    if ((c = *inp++) == '\n')
		  break;
	    if (ap == &newargs[NEWARGS])
bad:		  error("Bad #! line");
	    STARTSTACKSTR(outp);
	    do {
		  STPUTC(c, outp);
	    } while (--n >= 0 && (c = *inp++) != ' ' && c != '\t' && c != '\n');
	    STPUTC('\0', outp);
	    n++, inp--;
	    *ap++ = grabstackstr(outp);
      }
      if (ap == newargs + 1) {	/* if no args, maybe no exec is needed */
	    p = newargs[0];
	    for (;;) {
		  if (equal(p, "sh") || equal(p, "ash")) {
			return;
		  }
		  while (*p != '/') {
			if (*p == '\0')
			      goto break2;
			p++;
		  }
		  p++;
	    }
break2:;
      }
      i = (char *)ap - (char *)newargs;		/* size in bytes */
      if (i == 0)
	    error("Bad #! line");
      for (ap2 = argv ; *ap2++ != NULL ; );
      new = ckmalloc(i + ((char *)ap2 - (char *)argv));
      ap = newargs, ap2 = new;
      while ((i -= sizeof (char **)) >= 0)
	    *ap2++ = *ap++;
      ap = argv;
      while (*ap2++ = *ap++);
      shellexec(new, envp, pathval(), 0);
}
#endif



/*
 * Do a path search.  The variable path (passed by reference) should be
 * set to the start of the path before the first call; padvance will update
 * this value as it proceeds.  Successive calls to padvance will return
 * the possible path expansions in sequence.  If an option (indicated by
 * a percent sign) appears in the path entry then the global variable
 * pathopt will be set to point to it; otherwise pathopt will be set to
 * NULL.
 */

char *pathopt;

char *
padvance(path, name)
      char **path;
      char *name;
      {
      register char *p, *q;
      char *start;
      int len;

      if (*path == NULL)
	    return NULL;
      start = *path;
      for (p = start ; *p && *p != ':' && *p != '%' ; p++);
      len = p - start + strlen(name) + 2;	/* "2" is for '/' and '\0' */
      while (stackblocksize() < len)
	    growstackblock();
      q = stackblock();
      if (p != start) {
	    bcopy(start, q, p - start);
	    q += p - start;
	    *q++ = '/';
      }
      strcpy(q, name);
      pathopt = NULL;
      if (*p == '%') {
	    pathopt = ++p;
	    while (*p && *p != ':')  p++;
      }
      if (*p == ':')
	    *path = p + 1;
      else
	    *path = NULL;
      return stalloc(len);
}



/*** Command hashing code ***/


hashcmd(argc, argv)  char **argv; {
      struct tblentry **pp;
      struct tblentry *cmdp;
      int c;
      int verbose;
      struct cmdentry entry;
      char *name;

      if (argc <= 1) {
	    for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
		  for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
			printentry(cmdp);
		  }
	    }
	    return 0;
      }
      verbose = 0;
      while ((c = nextopt("rv")) != '\0') {
	    if (c == 'r') {
		  clearcmdentry(0);
	    } else if (c == 'v') {
		  verbose++;
	    }
      }
      while ((name = *argptr) != NULL) {
	    if ((cmdp = cmdlookup(name, 0)) != NULL
	     && (cmdp->cmdtype == CMDNORMAL
		|| cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0))
		  delete_cmd_entry();
	    find_command(name, &entry, 1);
	    if (verbose) {
		  if (entry.cmdtype != CMDUNKNOWN) {	/* if no error msg */
			cmdp = cmdlookup(name, 0);
			printentry(cmdp);
		  }
		  flushall();
	    }
	    argptr++;
      }
      return 0;
}


STATIC void
printentry(cmdp)
      struct tblentry *cmdp;
      {
      int index;
      char *path;
      char *name;

      if (cmdp->cmdtype == CMDNORMAL) {
	    index = cmdp->param.index;
	    path = pathval();
	    do {
		  name = padvance(&path, cmdp->cmdname);
		  stunalloc(name);
	    } while (--index >= 0);
	    out1str(name);
      } else if (cmdp->cmdtype == CMDBUILTIN) {
	    out1fmt("builtin %s", cmdp->cmdname);
      } else if (cmdp->cmdtype == CMDFUNCTION) {
	    out1fmt("function %s", cmdp->cmdname);
#ifdef DEBUG
      } else {
	    error("internal error: cmdtype %d", cmdp->cmdtype);
#endif
      }
      if (cmdp->rehash)
	    out1c('*');
      out1c('\n');
}



/*
 * Resolve a command name.  If you change this routine, you may have to
 * change the shellexec routine as well.
 */

void
find_command(name, entry, printerr)
      char *name;
      struct cmdentry *entry;
      {
      struct tblentry *cmdp;
      int index;
      int prev;
      char *path;
      char *fullname;
      struct stat statb;
      int e;
      int i;

      /* If name contains a slash, don't use the hash table */
      if (strchr(name, '/') != NULL) {
	    entry->cmdtype = CMDNORMAL;
	    entry->u.index = 0;
	    return;
      }

      /* If name is in the table, and not invalidated by cd, we're done */
      if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->rehash == 0)
	    goto success;

      /* If %builtin not in path, check for builtin next */
      if (builtinloc < 0 && (i = find_builtin(name)) >= 0) {
	    INTOFF;
	    cmdp = cmdlookup(name, 1);
	    cmdp->cmdtype = CMDBUILTIN;
	    cmdp->param.index = i;
	    INTON;
	    goto success;
      }

      /* We have to search path. */
      prev = -1;		/* where to start */
      if (cmdp) {		/* doing a rehash */
	    if (cmdp->cmdtype == CMDBUILTIN)
		  prev = builtinloc;
	    else
		  prev = cmdp->param.index;
      }

      path = pathval();
      e = ENOENT;
      index = -1;
loop:
      while ((fullname = padvance(&path, name)) != NULL) {
	    stunalloc(fullname);
	    index++;
	    if (pathopt) {
		  if (prefix("builtin", pathopt)) {
			if ((i = find_builtin(name)) < 0)
			      goto loop;
			INTOFF;
			cmdp = cmdlookup(name, 1);
			cmdp->cmdtype = CMDBUILTIN;
			cmdp->param.index = i;
			INTON;
			goto success;
		  } else if (prefix("func", pathopt)) {
			/* handled below */
		  } else {
			goto loop;	/* ignore unimplemented options */
		  }
	    }
	    /* if rehash, don't redo absolute path names */
	    if (fullname[0] == '/' && index <= prev) {
		  if (index < prev)
			goto loop;
		  TRACE(("searchexec \"%s\": no change\n", name));
		  goto success;
	    }
	    while (stat(fullname, &statb) < 0) {
#ifdef SYSV
		  if (errno == EINTR)
			continue;
#endif
		  if (errno != ENOENT && errno != ENOTDIR)
			e = errno;
		  goto loop;
	    }
	    e = EACCES;	/* if we fail, this will be the error */
	    if ((statb.st_mode & S_IFMT) != S_IFREG)
		  goto loop;
	    if (pathopt) {		/* this is a %func directory */
		  stalloc(strlen(fullname) + 1);
		  readcmdfile(fullname);
		  if ((cmdp = cmdlookup(name, 0)) == NULL || cmdp->cmdtype != CMDFUNCTION)
			error("%s not defined in %s", name, fullname);
		  stunalloc(fullname);
		  goto success;
	    }
	    if (statb.st_uid == geteuid()) {
		  if ((statb.st_mode & 0100) == 0)
			goto loop;
	    } else if (statb.st_gid == getegid()) {
		  if ((statb.st_mode & 010) == 0)
			goto loop;
	    } else {
		  if ((statb.st_mode & 01) == 0)
			goto loop;
	    }
	    TRACE(("searchexec \"%s\" returns \"%s\"\n", name, fullname));
	    INTOFF;
	    cmdp = cmdlookup(name, 1);
	    cmdp->cmdtype = CMDNORMAL;
	    cmdp->param.index = index;
	    INTON;
	    goto success;
      }

      /* We failed.  If there was an entry for this command, delete it */
      if (cmdp)
	    delete_cmd_entry();
      if (printerr)
	    outfmt(out2, "%s: %s\n", name, errmsg(e, E_EXEC));
      entry->cmdtype = CMDUNKNOWN;
      return;

success:
      cmdp->rehash = 0;
      entry->cmdtype = cmdp->cmdtype;
      entry->u = cmdp->param;
}



/*
 * Search the table of builtin commands.
 */

int
find_builtin(name)
      char *name;
      {
      const register struct builtincmd *bp;

      for (bp = builtincmd ; bp->name ; bp++) {
	    if (*bp->name == *name && equal(bp->name, name))
		  return bp->code;
      }
      return -1;
}



/*
 * Called when a cd is done.  Marks all commands so the next time they
 * are executed they will be rehashed.
 */

void
hashcd() {
      struct tblentry **pp;
      struct tblentry *cmdp;

      for (pp = cmdtable ; pp < &cmdtable[CMDTABLESIZE] ; pp++) {
	    for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
		  if (cmdp->cmdtype == CMDNORMAL
		   || cmdp->cmdtype == CMDBUILTIN && builtinloc >= 0)
			cmdp->rehash = 1;
	    }
      }
}



/*
 * Called before PATH is changed.  The argument is the new value of PATH;
 * pathval() still returns the old value at this point.  Called with
 * interrupts off.
 */

void
changepath(newval)
      char *newval;
      {
      char *old, *new;
      int index;
      int firstchange;
      int bltin;

      old = pathval();
      new = newval;
      firstchange = 9999;	/* assume no change */
      index = 0;
      bltin = -1;
      for (;;) {
	    if (*old != *new) {
		  firstchange = index;
		  if (*old == '\0' && *new == ':'
		   || *old == ':' && *new == '\0')
			firstchange++;
		  old = new;	/* ignore subsequent differences */
	    }
	    if (*new == '\0')
		  break;
	    if (*new == '%' && bltin < 0 && prefix("builtin", new + 1))
		  bltin = index;
	    if (*new == ':') {
		  index++;
	    }
	    new++, old++;
      }
      if (builtinloc < 0 && bltin >= 0)
	    builtinloc = bltin;		/* zap builtins */
      if (builtinloc >= 0 && bltin < 0)
	    firstchange = 0;
      clearcmdentry(firstchange);
      builtinloc = bltin;
}


/*
 * Clear out command entries.  The argument specifies the first entry in
 * PATH which has changed.
 */

STATIC void
clearcmdentry(firstchange) {
      struct tblentry **tblp;
      struct tblentry **pp;
      struct tblentry *cmdp;

      INTOFF;
      for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
	    pp = tblp;
	    while ((cmdp = *pp) != NULL) {
		  if (cmdp->cmdtype == CMDNORMAL && cmdp->param.index >= firstchange
		   || cmdp->cmdtype == CMDBUILTIN && builtinloc >= firstchange) {
			*pp = cmdp->next;
			ckfree(cmdp);
		  } else {
			pp = &cmdp->next;
		  }
	    }
      }
      INTON;
}


/*
 * Delete all functions.
 */

#ifdef mkinit
MKINIT void deletefuncs();

SHELLPROC {
      deletefuncs();
}
#endif

void
deletefuncs() {
      struct tblentry **tblp;
      struct tblentry **pp;
      struct tblentry *cmdp;

      INTOFF;
      for (tblp = cmdtable ; tblp < &cmdtable[CMDTABLESIZE] ; tblp++) {
	    pp = tblp;
	    while ((cmdp = *pp) != NULL) {
		  if (cmdp->cmdtype == CMDFUNCTION) {
			*pp = cmdp->next;
			freefunc(cmdp->param.func);
			ckfree(cmdp);
		  } else {
			pp = &cmdp->next;
		  }
	    }
      }
      INTON;
}



/*
 * Locate a command in the command hash table.  If "add" is nonzero,
 * add the command to the table if it is not already present.  The
 * variable "lastcmdentry" is set to point to the address of the link
 * pointing to the entry, so that delete_cmd_entry can delete the
 * entry.
 */

struct tblentry **lastcmdentry;


STATIC struct tblentry *
cmdlookup(name, add)
      char *name;
      {
      int hashval;
      register char *p;
      struct tblentry *cmdp;
      struct tblentry **pp;

      p = name;
      hashval = *p << 4;
      while (*p)
	    hashval += *p++;
      hashval &= 0x7FFF;
      pp = &cmdtable[hashval % CMDTABLESIZE];
      for (cmdp = *pp ; cmdp ; cmdp = cmdp->next) {
	    if (equal(cmdp->cmdname, name))
		  break;
	    pp = &cmdp->next;
      }
      if (add && cmdp == NULL) {
	    INTOFF;
	    cmdp = *pp = ckmalloc(sizeof (struct tblentry) - ARB
			      + strlen(name) + 1);
	    cmdp->next = NULL;
	    cmdp->cmdtype = CMDUNKNOWN;
	    cmdp->rehash = 0;
	    strcpy(cmdp->cmdname, name);
	    INTON;
      }
      lastcmdentry = pp;
      return cmdp;
}


/*
 * Delete the command entry returned on the last lookup.
 */

STATIC void
delete_cmd_entry() {
      struct tblentry *cmdp;

      INTOFF;
      cmdp = *lastcmdentry;
      *lastcmdentry = cmdp->next;
      ckfree(cmdp);
      INTON;
}



#ifdef notdef
void
getcmdentry(name, entry)
      char *name;
      struct cmdentry *entry; 
      {
      struct tblentry *cmdp = cmdlookup(name, 0);

      if (cmdp) {
	    entry->u = cmdp->param;
	    entry->cmdtype = cmdp->cmdtype;
      } else {
	    entry->cmdtype = CMDUNKNOWN;
	    entry->u.index = 0;
      }
}
#endif


/*
 * Add a new command entry, replacing any existing command entry for
 * the same name.
 */

void
addcmdentry(name, entry)
      char *name;
      struct cmdentry *entry;
      {
      struct tblentry *cmdp;

      INTOFF;
      cmdp = cmdlookup(name, 1);
      if (cmdp->cmdtype == CMDFUNCTION) {
	    freefunc(cmdp->param.func);
      }
      cmdp->cmdtype = entry->cmdtype;
      cmdp->param = entry->u;
      INTON;
}


/*
 * Define a shell function.
 */

void
defun(name, func)
      char *name;
      union node *func;
      {
      struct cmdentry entry;

      INTOFF;
      entry.cmdtype = CMDFUNCTION;
      entry.u.func = copyfunc(func);
      addcmdentry(name, &entry);
      INTON;
}


/*
 * Delete a function if it exists.
 */

void
unsetfunc(name)
      char *name;
      {
      struct tblentry *cmdp;

      if ((cmdp = cmdlookup(name, 0)) != NULL && cmdp->cmdtype == CMDFUNCTION) {
	    freefunc(cmdp->param.func);
	    delete_cmd_entry();
      }
}