/* sh.c - toybox shell
 *
 * Copyright 2006 Rob Landley <rob@landley.net>
 *
 * The POSIX-2008/SUSv4 spec for this is at:
 * http://opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
 * and http://opengroup.org/onlinepubs/9699919799/utilities/sh.html
 *
 * The first link describes the following shell builtins:
 *
 *   break colon continue dot eval exec exit export readonly return set shift
 *   times trap unset
 *
 * The second link (the utilities directory) also contains specs for the
 * following shell builtins:
 *
 *   alias bg cd command fc fg getopts hash jobs kill read type ulimit
 *   umask unalias wait
 *
 * Things like the bash man page are good to read too.
 *
 * TODO: "make sh" doesn't work (nofork builtins need to be included)
 * TODO: test that $PS1 color changes work without stupid \[ \] hack
 * TODO: make fake pty wrapper for test infrastructure
 * TODO: // Handle embedded NUL bytes in the command line.
 * TODO: var=val command
 * existing but considered builtins: false kill pwd true
 * buitins: alias bg command fc fg getopts jobs newgrp read umask unalias wait
 * "special" builtins: break continue : . eval exec export readonly return set
 *   shift times trap unset
 * | & ; < > ( ) $ ` \ " ' <space> <tab> <newline>
 * * ? [ # ~ = %
 * ! { } case do done elif else esac fi for if in then until while
 * [[ ]] function select
 * $@ $* $# $? $- $$ $! $0
 * ENV HOME IFS LANG LC_ALL LINENO PATH PPID PS1 PS2 PS4 PWD
 * label:
 * TODO: test exit from "trap EXIT" doesn't recurse

USE_SH(NEWTOY(cd, NULL, TOYFLAG_NOFORK))
USE_SH(NEWTOY(exit, NULL, TOYFLAG_NOFORK))

USE_SH(NEWTOY(sh, "c:i", TOYFLAG_BIN))
USE_SH(OLDTOY(toysh, sh, TOYFLAG_BIN))
// Login lies in argv[0], so add some aliases to catch that
USE_SH(OLDTOY(-sh, sh, 0))
USE_SH(OLDTOY(-toysh, sh, 0))

config SH
  bool "sh (toysh)"
  default n
  help
    usage: sh [-c command] [script]

    Command shell.  Runs a shell script, or reads input interactively
    and responds to it.

    -c	command line to execute
    -i	interactive mode (default when STDIN is a tty)

config CD
  bool
  default n
  depends on SH
  help
    usage: cd [-PL] [path]

    Change current directory.  With no arguments, go $HOME.

    -P	Physical path: resolve symlinks in path.
    -L	Local path: .. trims directories off $PWD (default).

config EXIT
  bool
  default n
  depends on SH
  help
    usage: exit [status]

    Exit shell.  If no return value supplied on command line, use value
    of most recent command, or 0 if none.
*/

#define FOR_sh
#include "toys.h"

GLOBALS(
  char *command;

  long lineno;
)

// What we know about a single process.
struct command {
  struct command *next;
  int flags;              // exit, suspend, && ||
  int pid;                // pid (or exit code)
  int argc;
  char *argv[0];
};

// A collection of processes piped into/waiting on each other.
struct pipeline {
  struct pipeline *next;
  int job_id;
  struct command *cmd;
  char *cmdline;         // Unparsed line for display purposes
  int cmdlinelen;        // How long is cmdline?
};

void cd_main(void)
{
  char *dest = *toys.optargs ? *toys.optargs : getenv("HOME");

  xchdir(dest ? dest : "/");
}

void exit_main(void)
{
  exit(*toys.optargs ? atoi(*toys.optargs) : 0);
}

// Parse one word from the command line, appending one or more argv[] entries
// to struct command.  Handles environment variable substitution and
// substrings.  Returns pointer to next used byte, or NULL if it
// hit an ending token.
static char *parse_word(char *start, struct command **cmd)
{
  char *end;

  // Detect end of line (and truncate line at comment)
  if (strchr("><&|(;", *start)) return 0;

  // Grab next word.  (Add dequote and envvar logic here)
  end = start;
  while (*end && !isspace(*end)) end++;
  (*cmd)->argv[(*cmd)->argc++] = xstrndup(start, end-start);

  // Allocate more space if there's no room for NULL terminator.

  if (!((*cmd)->argc & 7))
    *cmd=xrealloc(*cmd,
        sizeof(struct command) + ((*cmd)->argc+8)*sizeof(char *));
  (*cmd)->argv[(*cmd)->argc] = 0;
  return end;
}

// Parse a line of text into a pipeline.
// Returns a pointer to the next line.

static char *parse_pipeline(char *cmdline, struct pipeline *line)
{
  struct command **cmd = &(line->cmd);
  char *start = line->cmdline = cmdline;

  if (!cmdline) return 0;

  line->cmdline = cmdline;

  // Parse command into argv[]
  for (;;) {
    char *end;

    // Skip leading whitespace and detect end of line.
    while (isspace(*start)) start++;
    if (!*start || *start=='#') {
      line->cmdlinelen = start-cmdline;
      return 0;
    }

    // Allocate next command structure if necessary
    if (!*cmd) *cmd = xzalloc(sizeof(struct command)+8*sizeof(char *));

    // Parse next argument and add the results to argv[]
    end = parse_word(start, cmd);

    // If we hit the end of this command, how did it end?
    if (!end) {
      if (*start) {
        if (*start==';') {
          start++;
          break;
        }
        // handle | & < > >> << || &&
      }
      break;
    }
    start = end;
  }

  line->cmdlinelen = start-cmdline;

  return start;
}

// Execute the commands in a pipeline
static void run_pipeline(struct pipeline *line)
{
  struct toy_list *tl;
  struct command *cmd = line->cmd;
  if (!cmd || !cmd->argc) return;

  tl = toy_find(cmd->argv[0]);

  // Is this command a builtin that should run in this process?
  if (tl && (tl->flags & TOYFLAG_NOFORK)) {
    struct toy_context temp;
    jmp_buf rebound;

    // This fakes lots of what toybox_main() does.
    memcpy(&temp, &toys, sizeof(struct toy_context));
    memset(&toys, 0, sizeof(struct toy_context));

    if (!setjmp(rebound)) {
      toys.rebound = &rebound;
      toy_init(tl, cmd->argv);
      tl->toy_main();
    }
    cmd->pid = toys.exitval;
    if (toys.optargs != toys.argv+1) free(toys.optargs);
    if (toys.old_umask) umask(toys.old_umask);
    memcpy(&toys, &temp, sizeof(struct toy_context));
  } else {
    int status;

    cmd->pid = vfork();
    if (!cmd->pid) xexec(cmd->argv);
    else waitpid(cmd->pid, &status, 0);

    if (WIFEXITED(status)) cmd->pid = WEXITSTATUS(status);
    if (WIFSIGNALED(status)) cmd->pid = WTERMSIG(status);
  }

  return;
}

// Free the contents of a command structure
static void free_cmd(void *data)
{
  struct command *cmd=(struct command *)data;

  while(cmd->argc) free(cmd->argv[--cmd->argc]);
}


// Parse a command line and do what it says to do.
static void handle(char *command)
{
  struct pipeline line;
  char *start = command;

  // Loop through commands in this line

  for (;;) {

    // Parse a group of connected commands

    memset(&line,0,sizeof(struct pipeline));
    start = parse_pipeline(start, &line);
    if (!line.cmd) break;

    // Run those commands

    run_pipeline(&line);
    llist_traverse(line.cmd, free_cmd);
  }
}

static void do_prompt(void)
{
  char *prompt = getenv("PS1"), *s, c, cc;

  if (!prompt) prompt = "\\$ ";
  while (*prompt) {
    c = *(prompt++);

    if (c=='!') {
      if (*prompt=='!') prompt++;
      else {
        printf("%ld", TT.lineno);
        continue;
      }
    } else if (c=='\\') {
      cc = *(prompt++);
      if (!cc) goto down;

      // \nnn \dD{}hHjlstT@AuvVwW!#$
      // Ignore bash's "nonprintable" hack; query our cursor position instead.
      if (cc=='[' || cc==']') continue;
      else if (cc=='$') putchar(getuid() ? '$' : '#');
      else if (cc=='h' || cc=='H') {
        *toybuf = 0;
        gethostname(toybuf, sizeof(toybuf)-1);
        if (cc=='h' && (s = strchr(toybuf, '.'))) *s = 0;
        fputs(toybuf, stdout);
      } else if (cc=='s') fputs(getbasename(*toys.argv), stdout);
      else {
        if (!(c = unescape(cc))) {
          c = '\\';
          prompt--;
        }

        goto down;
      }
      continue;
    }
down:
    putchar(c);
  }
}

void sh_main(void)
{
  FILE *f = 0;

  // Set up signal handlers and grab control of this tty.
  if (isatty(0)) toys.optflags |= FLAG_i;

  if (*toys.optargs) f = xfopen(*toys.optargs, "r");
  if (TT.command) handle(xstrdup(TT.command));
  else {
    size_t cmdlen = 0;
    for (;;) {
      char *command = 0;

      // TODO: parse escapes in prompt
      if (!f) do_prompt();
      if (1 > getline(&command, &cmdlen, f ? f : stdin)) break;
      handle(command);
      free(command);
    }
  }

  toys.exitval = 1;
}