/* 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
 * TODO: ! history expansion
 *
 * bash man page:
 * control operators || & && ; ;; ;& ;;& ( ) | |& <newline>
 * reserved words
 *   ! case  coproc  do done elif else esac fi for  function  if  in  select
 *   then until while { } time [[ ]]



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)

# These are here for the help text, they're not selectable and control nothing
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;

  struct double_list functions;

  // Running jobs.
  struct sh_job {
    struct sh_job *next, *prev;
    unsigned jobno;

    // Every pipeline has at least one set of arguments or it's Not A Thing
    struct sh_arg {
      char **v;
      int c;
    } pipeline;

    // null terminated array of running processes in pipeline
    struct sh_process {
      struct string_list *delete; // expanded strings
      int pid, exit;   // status? Stopped? Exited?
      struct sh_arg arg;
    } *procs, *proc;
  } *jobs, *job;
  unsigned jobcnt;
)

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);
}

// Print prompt, parsing escapes
static void do_prompt(char *prompt)
{
  char *s, c, cc;

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

    if (c=='!') {
      if (*prompt=='!') prompt++;
      else {
        printf("%ld", TT.lineno);
        continue;
      }
    } else if (c=='\\') {
      int i = 0;

      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--;
        }
        i++;
      }
      if (!i) continue;
    }
down:
    putchar(c);
  }
  fflush(stdout);
}

// Assign one variable
// s: key=val
// type: 0 = whatever it was before, local otherwise
void setvar(char *s, int type)
{
// todo: expand_arg: tilde, parameter+variable expansion, command substitution, arith expansion, quote removal. No wildcards, "$@" treated like "$@".
  // local, export, readonly, integer...
  xsetenv(xstrdup(s), 0);
}

// todo: ${name:?error} causes an error/abort here (syntax_err longjmp?)
static void expand_arg(struct sh_arg *arg, char *new)
{
  if (!(arg->c&32)) arg->v = xrealloc(arg->v, sizeof(void *)*(arg->c+33));

  arg->v[arg->c++] = new;
  arg->v[arg->c] = 0;

/*
  char *s = word, *new = 0;

  // replacement
  while (*s) {
    if (*s == '$') {
      s++;
    } else if (*strchr("*?[{", *s)) {
      s++;
    } else if (*s == '<' || *s == '>') {
      s++;
    } else s++;
  }

  return new;
*/
}

// Execute the commands in a pipeline
static void run_command(struct sh_arg *arg)
{
  struct sh_process *pp = xzalloc(sizeof(struct sh_process));
  struct toy_list *tl;
  unsigned envlen, j;

  // Grab variable assignments
  for (envlen = 0; envlen<arg->c; envlen++) {
    char *s = arg->v[envlen];
    for (j=0; s[j] && s[j]!='=' && s[j]!='\\'; j++);
    if (s[j]!='=') break;
  }
  if (envlen == arg->c) {
    for (j = 0; j<envlen; j++) setvar(arg->v[j], 0);
    return;
  }

// todo: from i to envlen, need either start/end or to save a chunk
// how to set without duplicates and n^2 loop?

  for (j = envlen; j<arg->c; j++) expand_arg(&pp->arg, arg->v[j]);

  tl = toy_find(*pp->arg.v);

// todo use envlen
// todo: check for functions

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

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

// todo: redirect stdin/out
    if (!sigsetjmp(rebound, 1)) {
      toys.rebound = &rebound;
// must be null terminated
      toy_init(tl, pp->arg.v);
      tl->toy_main();
    }
    pp->exit = 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 pipe[2];

    pipe[0] = 0;
    pipe[1] = 1;
// todo: redirect and pipe
// todo: redirecting stderr needs xpopen3() or rethink
    if (-1 == (pp->pid = xpopen_both(pp->arg.v, pipe)))
      perror_msg("%s: vfork", *pp->arg.v);
// todo: don't close stdin/stdout!
    else pp->exit = xpclose_both(pp->pid, 0);
  }

  llist_traverse(pp->delete, free);
  return;
}

// like error_msg() but exit from shell scripts
void syntax_err(char *msg, ...)
{
  va_list va;

  va_start(va, msg);
  verror_msg(msg, 0, va);
  va_end(va);

  if (*toys.optargs) xexit();
}

// return length of match found at this point
static int anyof(char *s, char **try)
{
  while (*try) {
    if (strstart(&s, *try)) return strlen(*try);
    try++;
  }

  return 0;
}

// parse next word from command line. Returns end, or 0 if need continuation
// caller eats leading spaces
static char *parse_word(char *start)
{
  int i, quote = 0;
  char *end = start, *s;

  // find end of this word
  while (*end) {
    i = 0;

    // Handle quote contexts
    if (quote) {
      // end quote, skip quoted chars
      if (*end == toybuf[quote-1]) quote--, end++;
      else if (toybuf[quote-1] == '"' && *end == '`') toybuf[quote++] = *end++;
      else if (toybuf[quote-1] == '\'' || isspace(*end)) end++;
      else i++;
    } else {
      if (isspace(*end)) break;
      // start quote
      if (strchr("\"'`", *end)) toybuf[quote++] = *end++;
      else if (strstart(&end, "<(") || strstart(&end,">(")) toybuf[quote++]=')';
      else {
        // control chars.
        // 123<<file- parses as 2 args: "123<<" "file-".
        // note: >&; becomes ">&" ";" because first loop, then second loop.
        s = end;
        if (*s == '{') s++;
        for (s = end; isdigit(*s); s++);
        if (*end == '{' && *s == '}') s++;
        s += anyof(s, (char *[]){"<<<", "<<-", "<<", "<&", "<>", "<", ">>",
          ">&", ">|", ">", 0});
        if (s == end || isdigit(s[-1]))
          s += anyof(s, (char *[]){";;&", ";;", ";&", ";", "||", "|&", "|",
            "&&", "&>>", "&>", "&", "(", ")", 0});
        if (s != end && !isdigit(*s)) return (end == start) ? s : end;
        i++;
      }
    }

    // loop if we already handled a symbol
    if (!i) continue;

    // Things the same unquoted or in double quotes

    // backslash escapes
    if (*end == '\\') {
      if (!end[1] || (end[1]=='\n' && !end[2])) return 0;
      end += 2;
    } else if (*end == '$') {
      // barf if we're near overloading quote stack (nesting ridiculously deep)
      if (quote>4000) {
        syntax_err("tilt");
        return (void *)1;
      }
      end++;
      if (strstart(&end, "((")) {
        // all we care about here are parentheses matching and then ending ))
        for (i = 0;;) {
          if (!*end) return 0;
          if (!i && strstart(&end, "))")) break;
          if (*end == '(') i++;
          else if (*end == ')') i--;
        }
      } else if (-1 != (i = stridx("({[", *end))) {
        toybuf[quote++] = ")}]"[i];
        end++;
      }
    } else end++;
  }

  return quote ? 0 : end;
}

// if then fi for while until select done done case esac break continue return

// Allocate more space for arg, and possibly terminator
void argxtend(struct sh_arg *arg)
{
  if (!(arg->c&31)) arg->v = xrealloc(arg->v, (33+arg->c)*sizeof(void *));
}

// Pipeline segments
struct sh_pipeline {
  struct sh_pipeline *next, *prev;
  char count, here, type;
  struct sh_arg arg[1];
};

// scratch space (state held between calls). Don't want to make it global yet
// because this could be reentrant.
struct sh_parse {
  struct sh_pipeline *pipeline;
  struct double_list *expect;
  char *end;
};

// Free one pipeline segment.
void free_pipeline(void *pipeline)
{
  struct sh_pipeline *pl = pipeline;
  int i, j;

  if (pl) for (j=0; j<=pl->count; j++) {
    for (i = 0; i<=pl->arg->c; i++)  free(pl->arg[j].v[i]);
    free(pl->arg[j].v);
  }
  free(pl);
}

// Consume a line of shell script and do what it says. Returns 0 if finished,
// 1 to request another line of input (> prompt).
static int parse_line(char *line, struct sh_parse *sp)
{
  char *start = line, *delete = 0, *end, *last = 0, *s, *ex;
  struct sh_pipeline *pl = sp->pipeline ? sp->pipeline->prev : 0;
  struct sh_arg *arg = 0;
  long i;

  // Resume appending to last statement?
  if (pl) {
    arg = pl->arg;

    // Extend/resume quoted block
    if (arg->c<0) {
      delete = start = xmprintf("%s%s", arg->v[arg->c = (-arg->c)-1], start);
      free(arg->v[arg->c]);
      arg->v[arg->c] = 0;

    // is a HERE document in progress?
    } else if (pl->count != pl->here) {
      arg += 1+pl->here;

      argxtend(arg);
      if (strcmp(line, arg->v[arg->c])) {
        // Add this line
        arg->v[arg->c+1] = arg->v[arg->c];
        arg->v[arg->c++] = xstrdup(line);
      // EOF hit, end HERE document
      } else {
        arg->v[arg->c] = 0;
        pl->here++;
      }
      start = 0;
    }
  }

  // Parse words, assemble argv[] pipelines, check flow control and HERE docs
  if (start) for (;;) {
    s = 0;

    // skip leading whitespace/comment here to know where next word starts
    for (;;) {
      if (isspace(*start)) ++start;
      else if (*start=='#') while (*start && *start != '\n') ++start;
      else break;
    }

    // Parse next word and detect overflow (too many nested quotes).
    if ((end = parse_word(start)) == (void *)1) goto flush;

    // Extend pipeline and argv[] to store result
    if (!arg) {
      pl = xzalloc(sizeof(struct sh_pipeline));
      arg = pl->arg;
      dlist_add_nomalloc((void *)&sp->pipeline, (void *)pl);
    }
    argxtend(arg);

    // Do we need to request another line to finish word (find ending quote)?
    if (!end) {
      // Save unparsed bit of this line, we'll need to re-parse it.
      arg->v[arg->c] = xstrndup(start, strlen(start));
      arg->c = -(arg->c+1);
      free(delete);

      return 1;
    }

    // Ok, we have a word. What does it _mean_?

    // Did we hit end of line or ) outside a function declaration?
    // ) is only saved at start of a statement, ends current statement
    if (end == start || (arg->c && *start == ')' && pl->type!='f')) {
      arg->v[arg->c] = 0;

      if (pl->type == 'f' && arg->c<3) {
        s = "function()";
        goto flush;
      }

      // don't save blank pipeline segments
      if (!arg->c) free_pipeline(dlist_lpop(&sp->pipeline));

      // stop at EOL, else continue with new pipeline segment for )
      if (end == start) break;
      arg = 0;
      last = 0;

      continue;
    } else {

      // Save argument (strdup) and check for flow control
      s = arg->v[arg->c] = xstrndup(start, end-start);
      start = end;
      if (!strchr(";|&", *s)) arg->v[++arg->c] = 0;
      else {

        // flow control without a statement is an error
        if (!arg->c) goto flush;

        // treat ; as newline so we don't have to check both elsewhere.
        if (!strcmp(s, ";")) {
          arg->v[arg->c] = 0;
          free(s);
          s = 0;
        }
        last = s;
        arg = 0;

        continue;
      }
    }

    // We just ended a pipeline segment.

    // Grab HERE document(s)
    for (i = 0; i<arg->c; i++) {

      // find an argument of the form [{n}]<<[-] with another one after it
      s = arg->v[i];
      if (*s == '{') s++;
      while (isdigit(*s)) s++;
      if (*arg->v[i] == '{' && *s == '}') s++;
      if (strcmp(s, "<<") && strcmp(s, "<<-")) continue;
      if (i+1 == arg->c) goto flush;

      // Got one, queue it up so input loop asks for more lines.
      dlist_lpop(&sp->pipeline);
      pl = xrealloc(pl, sizeof(*pl) + ++pl->count*sizeof(struct sh_arg));
      dlist_add_nomalloc((void *)&sp->pipeline, (void *)pl);

      arg[pl->count].v = xzalloc(sizeof(void *));
      *arg[pl->count].v = arg->v[++i];
      arg[pl->count].c = 0;
    }

    // function in progress?
    if (arg->c>1 && !strcmp(s, "(")) pl->type = 'f';
    if (pl->type=='f') {
      if (arg->c == 2 && strcmp(s, "(")) goto flush;
      if (arg->c == 3) {
        if (strcmp(s, ")")) goto flush;

        // end function segment, expect function body
        arg = 0;
        last = 0;
        dlist_add(&sp->expect, "}");
        dlist_add(&sp->expect, 0);
        dlist_add(&sp->expect, "{");

        continue;
      }

    // flow control is the first word of a pipeline segment
    } else if (arg->c>1) continue;
    ex = sp->expect ? sp->expect->prev->data : 0;

    // When waiting for { it must be next symbol, but can be on a new line.
    if (ex && !strcmp(ex, "{")) {
      if (strcmp(s, "{") || (!i && *end)) goto flush;
      free(arg->v[--arg->c]);

      continue;
    }

    end = 0;
    if (!strcmp(s, "if")) end = "then";
    else if (!strcmp(s, "for") || !strcmp(s, "select")
         || !strcmp(s, "while") || !strcmp(s, "until")) end = "do";
    else if (!strcmp(s, "case")) end = "esac";
    else if (!strcmp(s, "{")) end = "}";
    else if (!strcmp(s, "[[")) end = "]]";
    else if (!strcmp(s, "(")) end = ")";

    // Expecting NULL means a statement: any otherwise unrecognized word
    else if (sp->expect && !ex) {
      free(dlist_pop(&sp->expect));
      continue;
    } else if (!ex) goto check;

    if (end) {
      pl->type = 1;

      // Only innermost statement needed in { { { echo ;} ;} ;} and such
      if (sp->expect && !sp->expect->prev->data) free(dlist_pop(&sp->expect));

    // If we got here we expect a specific word to end this block: is this it?
    } else if (!strcmp(s, ex)) {
      // can't "if | then" or "while && do", only ; & or newline works
      if (*last && strcmp(end, "&")) {
        s = end;
        goto flush;
      }

      free(dlist_pop(&sp->expect));
      pl->type = anyof(s, (char *[]){"fi", "done", "esac", "}", "]]", ")"})
        ? 3 : 2;

      // if it's a multipart block, what comes next?
      if (!strcmp(s, "do")) end = "done";
      else if (!strcmp(s, "then")) end = "fi\0A";

    // fi could have elif, which queues a then.
    } else if (!strcmp(ex, "fi")) {
      if (!strcmp(s, "elif")) {
        free(dlist_pop(&sp->expect));
        end = "then";
      // catch duplicate else while we're here
      } else if (!strcmp(s, "else")) {
        if (ex[3] != 'A') {
          s = "2 else";
          goto flush;
        }
        free(dlist_pop(&sp->expect));
        end = "fi\0B";
      }
    }

    // Do we need to queue up the next thing to expect?
    if (end) {
      if (!pl->type) pl->type = 2;
      dlist_add(&sp->expect, end);
      dlist_add(&sp->expect, 0);    // they're all preceded by a statement
    }

check:
    // syntax error check: these can't be the first word in an unexpected place
    if (!pl->type && anyof(s, (char *[]){"then", "do", "esac", "}", "]]", ")",
        "done", "then", "fi", "elif", "else"})) goto flush;
  }
  free(delete);

if (0) if (sp->expect) {
dprintf(2, "expectorate\n");
struct double_list *dl;
for (dl = sp->expect; dl; dl = (dl->next == sp->expect) ? 0 : dl->next)
  dprintf(2, "expecting %s\n", dl->data);
if (sp->pipeline) dprintf(2, "count=%d here=%d\n", sp->pipeline->prev->count, sp->pipeline->prev->here);
}

  // return if HERE document or more flow control
  if (sp->expect) return 1;
  if (sp->pipeline && sp->pipeline->prev->count != sp->pipeline->prev->here)
    return 1;

  // At this point, we've don't need more input and can start executing.

if (0) {
dprintf(2, "pipeline now\n");
struct sh_pipeline *ppl = pl;
int q = 0;
for (pl = sp->pipeline; pl ; pl = (pl->next == sp->pipeline) ? 0 : pl->next) {
  for (i = 0; i<pl->arg->c; i++) printf("arg[%d][%ld]=%s\n", q, i, pl->arg->v[i]);
  printf("term[%d]=%s\n", q++, pl->arg->v[pl->arg->c]);
}
pl = ppl;
}

  // **************************** do the thing *******************************

  // Now we have a complete thought and can start running stuff.

  // iterate through the commands running each one

  // run a pipeline of commands
  for (pl = sp->pipeline; pl ; pl = (pl->next == sp->pipeline) ? 0 : pl->next) {
    arg = pl->arg;

/*
  function () { commands ; }
    local variables in functions

if/then/elif/else/fi
for select while until/do/done
case/esac
{/}
[[/]]
(/)
function/}

*/

    run_command(arg);
  }

  s = 0;
flush:
  if (s) syntax_err("bad %s", s);
  while ((pl = dlist_pop(&sp->pipeline))) free_pipeline(pl);
  llist_traverse(sp->expect, free);

  return 0;
}

void sh_main(void)
{
  FILE *f;
  struct sh_parse scratch;
  int prompt = 0;

  // Set up signal handlers and grab control of this tty.

  memset(&scratch, 0, sizeof(scratch));
  if (TT.command) f = fmemopen(TT.command, strlen(TT.command), "r");
  else if (*toys.optargs) f = xfopen(*toys.optargs, "r");
  else {
    f = stdin;
    if (isatty(0)) toys.optflags |= FLAG_i;
  }

  for (;;) {
    char *new = 0;
    size_t linelen = 0;

    // Prompt and read line
    if (f == stdin) {
      char *s = getenv(prompt ? "PS2" : "PS1");

      if (!s) s = prompt ? "> " : (getpid() ? "\\$ " : "# ");
      do_prompt(s);
    } else TT.lineno++;
    if (1>(linelen = getline(&new, &linelen, f ? f : stdin))) break;
    if (new[linelen-1] == '\n') new[--linelen] = 0;

// TODO if (!isspace(*new)) add_to_history(line);

    // returns 0 if line consumed, command if it needs more data
    prompt = parse_line(new, &scratch);
    free(new);
  }

  if (prompt) error_exit("%ld:unfinished line"+4*!TT.lineno, TT.lineno);
  toys.exitval = f && ferror(f);
}