/* bake.c - Ever burned a cake?
 * Copyright 2023 Emil Williams
 *
 * Licensed under the GNU Public License version 3 only, see LICENSE.
 *
 * @BAKE cc -std=c89 -O2 @FILENAME -o ${@SHORT} @ARGS # ${other-file} @STOP
 */

#define _POSIX_C_SOURCE 200809L

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <locale.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <limits.h>

#include "config.h"

#define START "@BAKE"
#define  STOP "@STOP"

#define EXPUNGE_START "${"
#define EXPUNGE_STOP   "}"

#define VERSION "20240302"

#define  HELP                                                                                         \
  BOLD "[option] target-file" RESET " [" GREEN "arguments" RESET " ...]\n"                            \
  "Use the format `" BOLD "@BAKE" RESET " cmd ...' within the target-file, this will execute the\n"   \
  "rest of line, or if found within the file, until the " BOLD "@STOP" RESET " marker.\n"             \

#define DESC                                                 \
  "Options [Must always be first]\n"                         \
  "\t" DIM "-h --help" RESET", " BOLD "-n --dry-run\n" RESET \
  "Expansions\n"                                             \
  "\t" YELLOW "@FILENAME" RESET "  returns target-file                (abc.x.txt)\n"  \
  "\t" YELLOW "@SHORT   " RESET "  returns target-file without suffix (^-> abc.x)\n"  \
  "\t" YELLOW "@ARGS    " RESET "  returns " GREEN "arguments" RESET "\n"

#define FILENAME_LIMIT (FILENAME_MAX)

#define BAKE_ERROR 127

enum {
  BAKE_UNRECOGNIZED,
  BAKE_MISSING_SUFFIX,
};

#define ARRLEN(a) (sizeof(a) / sizeof(a[0]))

#if INCLUDE_AUTONOMOUS_COMPILE
  __attribute__((__section__(".text"))) static char autonomous_compile[] =
  "@BAKE cc -std=c89 -O2 $@.c -o $@ $+ @STOP";
#endif

static int bake_errno;

typedef struct {
  char * buf;
  size_t len;
} string_t;

typedef string_t map_t;

/*** root ***/

static void
swap(char * a, char * b) {
  *a ^= *b;
  *b ^= *a;
  *a ^= *b;
}

static int
root(char ** rootp) {
  char x[1] = {'\0'};
  char * root = *rootp;
  size_t len = strlen(root);
  int ret;

  while (len && root[len] != '/') {
    --len;
  }

  if (!len) {
    return 0;
  }

  swap(root + len, x);
  ret = chdir(root);
  swap(root + len, x);

  *rootp += len + 1;
  return ret;
}

/*** find region in file ***/

static map_t
map(char * fn) {
  struct stat s;
  int fd;
  map_t m = (map_t) {
    0
  };
  fd = open(fn, O_RDONLY);

  if (fd != -1) {
    if (!fstat(fd, &s)
        &&   s.st_mode & S_IFREG
        &&   s.st_size) {
      m.len = (size_t) s.st_size;
      m.buf = (char *) mmap(NULL, m.len, PROT_READ, MAP_SHARED, fd, 0);
    }

    close(fd);
  }

  return m;
}

static char *
find(char * buf, char * x, char * end) {
  size_t xlen = strlen(x);
  char * start = buf;

  for (; buf <= end - xlen; ++buf) {
    if (!strncmp(buf, x, xlen)) {
      if (start < buf && buf[-1] == '\\') {
        continue;
      } else {
        return buf;
      }
    }
  }

  return NULL;
}

static string_t
get_region(string_t m, char * findstart, char * findstop) {
  string_t ret = { NULL, 0 };
  char * end = m.len + m.buf;
  ret.buf = find(m.buf, findstart, end);

  if (ret.buf) {
    char * stop = ret.buf + strlen(findstart);
    stop = find(stop, findstop, end);

    if (stop) {
      ret.len = stop - ret.buf;
    } else      {
      ret.buf = NULL;
    }
  }

  return ret;
}

static char *
find_region(string_t m, char * findstart, char * findstop) {
  char * buf = NULL, * start, * stop, * end = m.len + m.buf;
  start = find(m.buf, findstart, end);

  if (start) {
    start += strlen(findstart);

#ifdef REQUIRE_SPACE

    if (!isspace(*start)) {
      bake_errno = BAKE_MISSING_SUFFIX;
      return NULL;
    }

#endif /* REQUIRE_SPACE */

    stop = find(start, findstop, end);

    if (!stop) {
      stop = start;

      while (stop < end && *stop != '\n') {
        if (stop[0] == '\\'
            &&  stop[1] == '\n') {
          stop += 2;
        }

        ++stop;
      }
    }

    buf = strndup(start, (size_t) (stop - m.buf) - (start - m.buf));
  }

  return buf;
}

static char *
file_find_region(char * fn, char * start, char * stop) {
  char * buf = NULL;
  map_t m = map(fn);

  if (m.buf) {
    buf = find_region(m, start, stop);
    munmap(m.buf, m.len);
  }

  return buf;
}

/*** g_short, g_all ***/

static char *
shorten(char * fn) {
  size_t i, last, len;
  static char sh[FILENAME_LIMIT];
  len = strlen(fn);

  for (last = i = 0; i < len; ++i) {
    if (fn[i] == '.') {
      last = i;
    }
  }

  last = last ? last : i;
  strncpy(sh, fn, last);
  sh[last] = '\0';
  return sh;
}

static char *
all_args(size_t argc, char ** argv) {
  char * all = NULL;

  if (argc > 0) {
    size_t i, len = argc;

    for (i = 0; i < argc; ++i) {
      len += strlen(argv[i]);
    }

    all = malloc(len + 1);
    all[len] = '\0';

    for (len = 0, i = 0; i < argc; ++i) {
      strcpy(all + len, argv[i]);
      len += strlen(argv[i]) + 1;

      if (i + 1 < argc) {
        all[len - 1] = ' ';
      }
    }
  }

  return all ? all : calloc(1, 1);
}

/*** insert, expand, bake_expand ***/

static void
insert(char * str, char * new, size_t slen, size_t nlen, size_t shift) {
  memmove(str + nlen, str + shift, slen + 1 - shift);
  memcpy(str, new, nlen);
}

static char *
expand(char * buf, char * macro, char * with) {
  ssize_t i,
          blen = strlen(buf),
          mlen = strlen(macro),
          wlen = strlen(with),
          nlen;
  fflush(stdout);

  for (i = 0; i < blen - mlen + 1; ++i) {
    if (!strncmp(buf + i, macro, mlen)) {
      if (i && buf[i - 1] == '\\') {
        memmove(buf + i - 1, buf + i, blen - i);
        buf[blen - 1] = '\0';
      } else {
        nlen = wlen - mlen + 1;

        if (nlen > 0) {
          buf = realloc(buf, blen + nlen);
        }

        insert(buf + i, with, blen - i, wlen, mlen);
        blen += (nlen > 0) * nlen;
      }
    }
  }

  return buf;
}

static char *
bake_expand(char * buf, char * filename, int argc, char ** argv) {
  enum {
    MACRO_FILENAME,
    MACRO_SHORT,
    MACRO_ARGS,
    MACRO_STOP,
    MACRO_NONE
  };

  char * macro[MACRO_NONE],
       * macro_old[MACRO_STOP];

  size_t i;

  macro[MACRO_FILENAME] = "@FILENAME";
  macro[MACRO_SHORT   ] =    "@SHORT";
  macro[MACRO_ARGS    ] =     "@ARGS";
  macro[MACRO_STOP    ] =     "@STOP";

  macro_old[MACRO_FILENAME] = "$@";
  macro_old[MACRO_SHORT   ] = "$*";
  macro_old[MACRO_ARGS    ] = "$+";

  char * global[4];

  global[MACRO_FILENAME] = filename;
  global[MACRO_SHORT   ] = shorten(filename);
  global[MACRO_ARGS    ] = all_args((size_t) argc, argv);
  global[MACRO_STOP    ] = "";

#if NEW_MACROS

  for (i = 0; i < ARRLEN(macro); ++i) {
    buf = expand(buf, macro[i], global[i]);
  }

#endif

#if OLD_MACROS

  for (i = 0; i < ARRLEN(macro_old); ++i) {
    buf = expand(buf, macro_old[i], global[i]);
  }

#endif

  free(global[MACRO_ARGS]);

  return buf;
}

static string_t *
remove_expand(char * buf) {
  string_t * rem = NULL;
  size_t i = 0;
  size_t f;

  rem = (string_t *) realloc(rem, i + 1 * sizeof(string_t));

  while (rem) {
    fflush(stdout);
    rem[i] = get_region((string_t) {
      buf, strlen(buf)
    }, EXPUNGE_START, EXPUNGE_STOP);

    if (rem[i].buf) {
      expand(rem[i].buf, EXPUNGE_START, "");
      expand(rem[i].buf, EXPUNGE_STOP, "");
    } else break;

    ++i;
    rem = (string_t *) realloc(rem, (1 + i) * sizeof(string_t));
  }

  return rem;
}

/*** strip, run ***/

/* Strips all prefixing and leading whitespace.
 * Except if the last character beforehand is a newline. */
static size_t
strip(char * buf) {
  size_t i = strlen(buf);

  if (!i) {
    return 0;
  }

  while (i && isspace(buf[i - 1])) {
    --i;
  }

  buf[i] = '\0';

  for (i = 0; isspace(buf[i]); ++i);

  if (i && buf[i - 1] == '\n') {
    --i;
  }

  return i;
}

static int
run(char * buf, char * argv0) {
  puts(BOLD GREEN "output" RESET ":\n");
  pid_t pid;

  if ((pid = fork()) == 0) {
    execl("/bin/sh", "sh", "-c", buf, NULL);
    return 0; /* execl overwrites the process anyways */
  } else if (pid == -1) {
    fprintf(stderr, BOLD RED "%s" RESET ": %s, %s\n", argv0, "Fork Error",
            strerror(errno));
    return BAKE_ERROR;
  } else {
    int status;

    if (waitpid(pid, &status, 0) < 0) {
      fprintf(stderr, BOLD RED "%s" RESET ": %s, %s\n", argv0, "Wait PID Error",
              strerror(errno));
      return BAKE_ERROR;
    }

    if (!WIFEXITED(status)) {
      return BAKE_ERROR;
    }

    return WEXITSTATUS(status);
  }
}

/*** main ***/

int
main(int argc, char ** argv) {
  enum { RET_RUN = 0, RET_NORUN = (1 << 0), RET_EXPUNGE = (1 << 1) };
  int ret = RET_RUN;
  char  * buf = NULL,
          *  filename,
          *  argv0;
  string_t * rem;

  argv0 = argv[0];

  while (++argv, --argc && argv[0][0] == '-') {
    ++argv[0];

    if (argv[0][1] == '-') {
      ++argv[0];

      if (!strcmp(argv[0],    "help")) {
        goto help;
      } else if (!strcmp(argv[0], "version")) {
        goto version;
      } else if (!strcmp(argv[0], "expunge")) {
        ret |= RET_EXPUNGE;
      } else if (!strcmp(argv[0], "dry-run")) {
        ret |= RET_NORUN;
      } else                                  {
        puts("UNKNOWN");
        goto help;
      }
    } else do {
        switch (argv[0][0]) {
        case 'h':
          goto help;

        case 'v':
          goto version;

        case 'x':
          ret |= RET_EXPUNGE;
          break;

        case 'n':
          ret |= RET_NORUN;
          break;

        case 0  :
          goto next;

        default :
          puts("UNKNOWN");
          goto help;
        }
      } while (++(argv[0]));

  next:
  }

  filename = argv[0];
  ++argv, --argc;

  if (strlen(filename) > FILENAME_LIMIT) {
    fprintf(stderr, BOLD RED "%s" RESET ": Filename too long (exceeds %d)\n", argv0,
            FILENAME_LIMIT);
    return BAKE_ERROR;
  }

  root(&filename);
  buf = file_find_region(filename, START, STOP);

  char * error[2];
  error[0] = "File Unrecognized";
  error[1] = "Found start without suffix spacing";

  if (!buf) {
    fprintf(stderr, BOLD RED "%s" RESET ": '" BOLD "%s" RESET "' %s.\n",
            argv0, filename, errno ? strerror(errno) : error[bake_errno]);
    return BAKE_ERROR;
  }

  buf = bake_expand(buf, filename, argc, argv);

  printf(BOLD GREEN "%s" RESET ": %s\n", argv0, buf + strip(buf));

  rem = remove_expand(buf);

  printf(BOLD GREEN "%s" RESET ": %s\n", argv0, buf + strip(buf));

  if (!ret) {
    ret = run(buf, argv0);

    if (ret) {
      printf(BOLD RED "result" RESET ": " BOLD "%d\n" RESET, ret);
    }
  } else if (ret & RET_EXPUNGE) {
    if (ret & RET_NORUN) {
      puts("NORUN");
    } else {
      size_t i;
      for (i = 0; rem[i].buf; ++i) {
        printf("removing: %s\n", rem[i].buf);
        remove(rem[i].buf);
      }
    }
  }

  free(rem);
  free(buf);
  return ret;
help:
  fprintf(stderr, YELLOW "%s" RESET ": %s", argv0, HELP DESC);
  return BAKE_ERROR;
version:
  fprintf(stderr, YELLOW "%s" RESET ": v%s\n", argv0, VERSION);
  return BAKE_ERROR;
}