/* 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: // Handle embedded NUL bytes in the command line.

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, "c:i", TOYFLAG_BIN))

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

config SH_TTY
  bool "Interactive shell (terminal control)"
  default n
  depends on SH
  help
    Add terminal control to toysh.  This is necessary for interactive use,
    so the shell isn't killed by CTRL-C.

config SH_PROFILE
  bool "Profile support"
  default n
  depends on SH_TTY
  help
    Read /etc/profile and ~/.profile when running interactively.

    Also enables the built-in command "source".

config SH_JOBCTL
  bool "Job Control (fg, bg, jobs)"
  default n
  depends on SH_TTY
  help
    Add job control to toysh.  This lets toysh handle CTRL-Z, and enables
    the built-in commands "fg", "bg", and "jobs".

    With pipe support, enable use of "&" to run background processes.

config SH_FLOWCTL
  bool "Flow control (if, while, for, functions)"
  default n
  depends on SH
  help
    Add flow control to toysh.  This enables the if/then/else/fi,
    while/do/done, and for/do/done constructs.

    With pipe support, this enables the ability to define functions
    using the "function name" or "name()" syntax, plus curly brackets
    "{ }" to group commands.

config SH_QUOTES
  bool "Smarter argument parsing (quotes)"
  default n
  depends on SH
  help
    Add support for parsing "" and '' style quotes to the toysh command
    parser, with lets arguments have spaces in them.

config SH_WILDCARDS
  bool "Wildcards ( ?*{,} )"
  default n
  depends on SH_QUOTES
  help
    Expand wildcards in argument names, ala "ls -l *.t?z" and
    "rm subdir/{one,two,three}.txt".

config SH_PROCARGS
  bool "Executable arguments ( `` and $() )"
  default n
  depends on SH_QUOTES
  help
    Add support for executing arguments contianing $() and ``, using
    the output of the command as the new argument value(s).

    (Bash calls this "command substitution".)

config SH_ENVVARS
  bool "Environment variable support"
  default n
  depends on SH_QUOTES
  help
    Substitute environment variable values for $VARNAME or ${VARNAME},
    and enable the built-in command "export".

config SH_LOCALS
  bool "Local variables"
  default n
  depends on SH_ENVVARS
  help
    Support for local variables, fancy prompts ($PS1), the "set" command,
    and $?.

config SH_ARRAYS
  bool "Array variables"
  default n
  depends on SH_LOCALS
  help
    Support for ${blah[blah]} style array variables.

config SH_PIPES
  bool "Pipes and redirects ( | > >> < << & && | || () ; )"
  default n
  depends on SH
  help
    Support multiple commands on the same command line.  This includes
    | pipes, > >> < redirects, << here documents, || && conditional
    execution, () subshells, ; sequential execution, and (with job
    control) & background processes.

config SH_BUILTINS
  bool "Builtin commands"
  default n
  depends on SH
  help
    Adds the commands exec, fg, bg, help, jobs, pwd, export, source, set,
    unset, read, alias.

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.

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

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

config CD_P
  bool # "-P support for cd"
  default n
  depends on SH
  help
    usage: cd [-PL]

    -P    Physical path: resolve symlinks in path.
    -L    Cancel previous -P and restore default behavior.
*/

#define FOR_sh
#include "toys.h"

GLOBALS(
  char *command;
)

// A single executable, its arguments, and other information we know about it.
#define SH_FLAG_EXIT    1
#define SH_FLAG_SUSPEND 2
#define SH_FLAG_PIPE    4
#define SH_FLAG_AND     8
#define SH_FLAG_OR      16
#define SH_FLAG_AMP     32
#define SH_FLAG_SEMI    64
#define SH_FLAG_PAREN   128

// 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?
};

// 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 (CFG_SH_PIPES && 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;

  if (CFG_SH_JOBCTL) 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=='#') {
      if (CFG_SH_JOBCTL) 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 (CFG_SH_PIPES && *start) {
        if (*start==';') {
          start++;
          break;
        }
        // handle | & < > >> << || &&
      }
      break;
    }
    start = end;
  }

  if (CFG_SH_JOBCTL) 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 (CFG_SH_FLOWCTL || CFG_SH_PIPES) {
      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);
  }
}

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

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

void sh_main(void)
{
  FILE *f;

  // Set up signal handlers and grab control of this tty.
  if (CFG_SH_TTY) {
    if (isatty(0)) toys.optflags |= 1;
  }
  f = *toys.optargs ? xfopen(*toys.optargs, "r") : NULL;
  if (TT.command) handle(TT.command);
  else {
    size_t cmdlen = 0;
    for (;;) {
      char *command = 0;
      if (!f) xputc('$');
      if (1 > getline(&command, &cmdlen, f ? f : stdin)) break;
      handle(command);
      free(command);
    }
  }

  toys.exitval = 1;
}