/**
 * See Copyright Notice in picrin.h
 */

#include "picrin.h"
#include "picrin/extra.h"
#include "value.h"
#include "object.h"

#undef EOF
#define EOF (-1)

KHASH_DECLARE(read, int, pic_value)
KHASH_DEFINE(read, int, pic_value, kh_int_hash_func, kh_int_hash_equal)

struct reader_control {
  int typecase;
  khash_t(read) labels;
};

#define CASE_DEFAULT 0
#define CASE_FOLD    1

typedef pic_value (*pic_reader_t)(pic_state *, pic_value port, int c, struct reader_control *);

static pic_reader_t reader_table[256];
static pic_reader_t reader_dispatch[256];

static pic_value read_value(pic_state *pic, pic_value port, int c, struct reader_control *p);
static pic_value read_nullable(pic_state *pic, pic_value port, int c, struct reader_control *p);

PIC_NORETURN static void
read_error(pic_state *pic, const char *msg, pic_value irritants)
{
  pic_raise(pic, pic_make_error(pic, "read", msg, irritants));
}

static int
skip(pic_state *pic, pic_value port, int c)
{
  while (isspace(c)) {
    c = pic_fgetc(pic, port);
  }
  return c;
}

static int
next(pic_state *pic, pic_value port)
{
  return pic_fgetc(pic, port);
}

static int
peek(pic_state *pic, pic_value port)
{
  int c;

  pic_ungetc(pic, (c = pic_fgetc(pic, port)), port);

  return c;
}

static bool
expect(pic_state *pic, pic_value port, const char *str)
{
  int c;

  while ((c = (int)*str++) != 0) {
    if (c != peek(pic, port))
      return false;
    next(pic, port);
  }

  return true;
}

static bool
isdelim(int c)
{
  return c == EOF || strchr("();,|\" \t\n\r", c) != NULL; /* ignores "#", "'" */
}

static int
case_fold(int c, struct reader_control *p)
{
  if (p->typecase == CASE_FOLD) {
    c = tolower(c);
  }
  return c;
}

static pic_value
read_comment(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  do {
    c = next(pic, port);
  } while (! (c == EOF || c == '\n'));

  return pic_invalid_value(pic);
}

static pic_value
read_block_comment(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *PIC_UNUSED(p))
{
  int x, y;
  int i = 1;

  y = next(pic, port);

  while (y != EOF && i > 0) {
    x = y;
    y = next(pic, port);
    if (x == '|' && y == '#') {
      i--;
    }
    if (x == '#' && y == '|') {
      i++;
    }
  }

  return pic_invalid_value(pic);
}

static pic_value
read_datum_comment(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  read_value(pic, port, next(pic, port), p);

  return pic_invalid_value(pic);
}

static pic_value
read_directive(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  switch (peek(pic, port)) {
  case 'n':
    if (expect(pic, port, "no-fold-case")) {
      p->typecase = CASE_DEFAULT;
      return pic_invalid_value(pic);
    }
    break;
  case 'f':
    if (expect(pic, port, "fold-case")) {
      p->typecase = CASE_FOLD;
      return pic_invalid_value(pic);
    }
    break;
  }

  return read_comment(pic, port, c, p);
}

static pic_value
read_quote(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  return pic_list(pic, 2, pic_intern_lit(pic, "quote"), read_value(pic, port, next(pic, port), p));
}

static pic_value
read_quasiquote(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  return pic_list(pic, 2, pic_intern_lit(pic, "quasiquote"), read_value(pic, port, next(pic, port), p));
}

static pic_value
read_unquote(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  pic_value tag;

  if (peek(pic, port) == '@') {
    tag = pic_intern_lit(pic, "unquote-splicing");
    next(pic, port);
  } else {
    tag = pic_intern_lit(pic, "unquote");
  }
  return pic_list(pic, 2, tag, read_value(pic, port, next(pic, port), p));
}

static pic_value
read_syntax_quote(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  return pic_list(pic, 2, pic_intern_lit(pic, "syntax-quote"), read_value(pic, port, next(pic, port), p));
}

static pic_value
read_syntax_quasiquote(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  return pic_list(pic, 2, pic_intern_lit(pic, "syntax-quasiquote"), read_value(pic, port, next(pic, port), p));
}

static pic_value
read_syntax_unquote(pic_state *pic, pic_value port, int PIC_UNUSED(c), struct reader_control *p)
{
  pic_value tag;

  if (peek(pic, port) == '@') {
    tag = pic_intern_lit(pic, "syntax-unquote-splicing");
    next(pic, port);
  } else {
    tag = pic_intern_lit(pic, "syntax-unquote");
  }
  return pic_list(pic, 2, tag, read_value(pic, port, next(pic, port), p));
}

static pic_value
read_atom(pic_state *pic, pic_value port, int c, struct reader_control *p) {
  int len;
  char *buf;
  pic_value str;

  len = 1;
  buf = pic_malloc(pic, len + 1);
  buf[0] = case_fold(c, p);
  buf[1] = 0;

  while (! isdelim(peek(pic, port))) {
    c = next(pic, port);
    len += 1;
    buf = pic_realloc(pic, buf, len + 1);
    buf[len - 1] = case_fold(c, p);
    buf[len] = 0;
  }

  str = pic_str_value(pic, buf, len);
  pic_free(pic, buf);

  return str;
}

static pic_value
read_symbol(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  return pic_intern(pic, read_atom(pic, port, c, p));
}

static pic_value
read_number(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  pic_value str = read_atom(pic, port, c, p), num;

  num = pic_funcall(pic, "picrin.base", "string->number", 1, str);
  if (! pic_false_p(pic, num)) {
    return num;
  }
  return pic_intern(pic, str);
}

static unsigned
read_uinteger(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  unsigned u = 0;

  if (! isdigit(c)) {
    read_error(pic, "expected one or more digits", pic_list(pic, 1, pic_char_value(pic, c)));
  }

  u = c - '0';
  while (isdigit(c = peek(pic, port))) {
    u = u * 10 + next(pic, port) - '0';
  }

  return u;
}

static pic_value
read_true(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  if ((c = peek(pic, port)) == 'r') {
    if (! expect(pic, port, "rue")) {
      read_error(pic, "unexpected character while reading #true", pic_nil_value(pic));
    }
  } else if (! isdelim(c)) {
    read_error(pic, "non-delimiter character given after #t", pic_list(pic, 1, pic_char_value(pic, c)));
  }

  return pic_true_value(pic);
}

static pic_value
read_false(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  if ((c = peek(pic, port)) == 'a') {
    if (! expect(pic, port, "alse")) {
      read_error(pic, "unexpected character while reading #false", pic_nil_value(pic));
    }
  } else if (! isdelim(c)) {
    read_error(pic, "non-delimiter character given after #f", pic_list(pic, 1, pic_char_value(pic, c)));
  }

  return pic_false_value(pic);
}

static pic_value
read_char(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  c = next(pic, port);

  if (! isdelim(peek(pic, port))) {
    switch (c) {
    default: read_error(pic, "unexpected character after char literal", pic_list(pic, 1, pic_char_value(pic, c)));
    case 'a': c = '\a'; if (! expect(pic, port, "larm")) goto fail; break;
    case 'b': c = '\b'; if (! expect(pic, port, "ackspace")) goto fail; break;
    case 'd': c = 0x7F; if (! expect(pic, port, "elete")) goto fail; break;
    case 'e': c = 0x1B; if (! expect(pic, port, "scape")) goto fail; break;
    case 'n':
      if ((c = peek(pic, port)) == 'e') {
        c = '\n';
        if (! expect(pic, port, "ewline"))
          goto fail;
      } else {
        c = '\0';
        if (! expect(pic, port, "ull"))
          goto fail;
      }
      break;
    case 'r': c = '\r'; if (! expect(pic, port, "eturn")) goto fail; break;
    case 's': c = ' '; if (! expect(pic, port, "pace")) goto fail; break;
    case 't': c = '\t'; if (! expect(pic, port, "ab")) goto fail; break;
    }
  }

  return pic_char_value(pic, (char)c);

 fail:
  read_error(pic, "unexpected character while reading character literal", pic_list(pic, 1, pic_char_value(pic, c)));
}

static pic_value
read_string(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  char *buf;
  int size, cnt;
  pic_value str;

  size = 256;
  buf = pic_malloc(pic, size);
  cnt = 0;

  /* TODO: intraline whitespaces */

  while ((c = next(pic, port)) != '"') {
    if (c == '\\') {
      switch (c = next(pic, port)) {
      case 'a': c = '\a'; break;
      case 'b': c = '\b'; break;
      case 't': c = '\t'; break;
      case 'n': c = '\n'; break;
      case 'r': c = '\r'; break;
      }
    }
    buf[cnt++] = (char)c;
    if (cnt >= size) {
      buf = pic_realloc(pic, buf, size *= 2);
    }
  }
  buf[cnt] = '\0';

  str = pic_str_value(pic, buf, cnt);
  pic_free(pic, buf);
  return str;
}

static pic_value
read_pipe(pic_state *pic, pic_value port, int c, struct reader_control *PIC_UNUSED(p))
{
  char *buf;
  int size, cnt;
  pic_value sym;
  /* Currently supports only ascii chars */
  char HEX_BUF[3];
  size_t i = 0;

  size = 256;
  buf = pic_malloc(pic, size);
  cnt = 0;
  while ((c = next(pic, port)) != '|') {
    if (c == '\\') {
      switch ((c = next(pic, port))) {
      case 'a': c = '\a'; break;
      case 'b': c = '\b'; break;
      case 't': c = '\t'; break;
      case 'n': c = '\n'; break;
      case 'r': c = '\r'; break;
      case 'x':
        i = 0;
        while ((HEX_BUF[i++] = (char)next(pic, port)) != ';') {
          if (i >= sizeof HEX_BUF)
            read_error(pic, "expected ';'", pic_list(pic, 1, pic_char_value(pic, HEX_BUF[sizeof(HEX_BUF) - 1])));
        }
        c = (char)strtol(HEX_BUF, NULL, 16);
        break;
      }
    }
    buf[cnt++] = (char)c;
    if (cnt >= size) {
      buf = pic_realloc(pic, buf, size *= 2);
    }
  }
  buf[cnt] = '\0';

  sym = pic_intern_cstr(pic, buf);
  pic_free(pic, buf);

  return sym;
}

static pic_value
read_blob(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  int nbits, n;
  int len;
  unsigned char *dat;
  pic_value blob;

  nbits = 0;

  while (isdigit(c = next(pic, port))) {
    nbits = 10 * nbits + c - '0';
  }

  if (nbits != 8) {
    read_error(pic, "unsupported bytevector bit width", pic_list(pic, 1, pic_int_value(pic, nbits)));
  }

  if (c != '(') {
    read_error(pic, "expected '(' character", pic_list(pic, 1, pic_char_value(pic, c)));
  }

  len = 0;
  dat = NULL;
  c = next(pic, port);
  while ((c = skip(pic, port, c)) != ')') {
    n = read_uinteger(pic, port, c, p);
    if (n < 0 || (1 << nbits) <= n) {
      read_error(pic, "invalid element in bytevector literal", pic_list(pic, 1, pic_int_value(pic, n)));
    }
    len += 1;
    dat = pic_realloc(pic, dat, len);
    dat[len - 1] = (unsigned char)n;
    c = next(pic, port);
  }

  blob = pic_blob_value(pic, dat, len);

  pic_free(pic, dat);
  return blob;
}

static pic_value
read_undef_or_blob(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  if ((c = peek(pic, port)) == 'n') {
    if (! expect(pic, port, "ndefined")) {
      read_error(pic, "unexpected character while reading #undefined", pic_nil_value(pic));
    }
    return pic_undef_value(pic);
  }
  if (! isdigit(c)) {
    read_error(pic, "expect #undefined or #u8(...), but illegal character given", pic_list(pic, 1, pic_char_value(pic, c)));
  }
  return read_blob(pic, port, 'u', p);
}

static pic_value
read_pair(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  static const int tCLOSE = ')';
  pic_value car, cdr;

 retry:

  c = skip(pic, port, ' ');

  if (c == tCLOSE) {
    return pic_nil_value(pic);
  }
  if (c == '.' && isdelim(peek(pic, port))) {
    cdr = read_value(pic, port, next(pic, port), p);

  closing:
    if ((c = skip(pic, port, ' ')) != tCLOSE) {
      if (pic_invalid_p(pic, read_nullable(pic, port, c, p))) {
        goto closing;
      }
      read_error(pic, "unmatched parenthesis", pic_nil_value(pic));
    }
    return cdr;
  }
  else {
    car = read_nullable(pic, port, c, p);

    if (pic_invalid_p(pic, car)) {
      goto retry;
    }

    cdr = read_pair(pic, port, '(', p);
    return pic_cons(pic, car, cdr);
  }
}

static pic_value
read_vector(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  pic_value list, it, elem, vec;
  int i = 0;

  list = read_value(pic, port, c, p);

  vec = pic_make_vec(pic, pic_length(pic, list), NULL);

  pic_for_each (elem, list, it) {
    pic_vec_set(pic, vec, i++, elem);
  }

  return vec;
}

static pic_value
read_label_set(pic_state *pic, pic_value port, int i, struct reader_control *p)
{
  khash_t(read) *h = &p->labels;
  pic_value val;
  int c, ret, it;

  it = kh_put(read, h, i, &ret);

  switch ((c = skip(pic, port, ' '))) {
  case '(':
    {
      pic_value tmp;

      kh_val(h, it) = val = pic_cons(pic, pic_undef_value(pic), pic_undef_value(pic));

      tmp = read_value(pic, port, c, p);
      pic_pair_ptr(pic, val)->car = pic_car(pic, tmp);
      pic_pair_ptr(pic, val)->cdr = pic_cdr(pic, tmp);

      return val;
    }
  case '#':
    {
      bool vect;

      if (peek(pic, port) == '(') {
        vect = true;
      } else {
        vect = false;
      }

      if (vect) {
        pic_value tmp;

        kh_val(h, it) = val = pic_make_vec(pic, 0, NULL);

        tmp = read_value(pic, port, c, p);
        PIC_SWAP(pic_value *, pic_vec_ptr(pic, tmp)->data, pic_vec_ptr(pic, val)->data);
        PIC_SWAP(int, pic_vec_ptr(pic, tmp)->len, pic_vec_ptr(pic, val)->len);

        return val;
      }

      /* fall through */
    }
  default:
    {
      kh_val(h, it) = val = read_value(pic, port, c, p);

      return val;
    }
  }
}

static pic_value
read_label_ref(pic_state *pic, pic_value PIC_UNUSED(port), int i, struct reader_control *p)
{
  khash_t(read) *h = &p->labels;
  int it;

  it = kh_get(read, h, i);
  if (it == kh_end(h)) {
    read_error(pic, "label of given index not defined", pic_list(pic, 1, pic_int_value(pic, i)));
  }
  return kh_val(h, it);
}

static pic_value
read_label(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  int i;

  i = 0;
  do {
    i = i * 10 + c - '0';
  } while (isdigit(c = next(pic, port)));

  if (c == '=') {
    return read_label_set(pic, port, i, p);
  }
  if (c == '#') {
    return read_label_ref(pic, port, i, p);
  }
  read_error(pic, "broken label expression", pic_nil_value(pic));
}

static pic_value
read_unmatch(pic_state *pic, pic_value PIC_UNUSED(port), int PIC_UNUSED(c), struct reader_control *PIC_UNUSED(p))
{
  read_error(pic, "unmatched parenthesis", pic_nil_value(pic));
}

static pic_value
read_dispatch(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  c = next(pic, port);

  if (c == EOF) {
    read_error(pic, "unexpected EOF", pic_nil_value(pic));
  }

  if (reader_dispatch[c] == NULL) {
    read_error(pic, "invalid character at the seeker head", pic_list(pic, 1, pic_char_value(pic, c)));
  }

  return reader_dispatch[c](pic, port, c, p);
}

static pic_value
read_nullable(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  c = skip(pic, port, c);

  if (c == EOF) {
    read_error(pic, "unexpected EOF", pic_nil_value(pic));
  }

  if (reader_table[c] == NULL) {
    read_error(pic, "invalid character at the seeker head", pic_list(pic, 1, pic_char_value(pic, c)));
  }

  return reader_table[c](pic, port, c, p);
}

static pic_value
read_value(pic_state *pic, pic_value port, int c, struct reader_control *p)
{
  pic_value val;

 retry:
  val = read_nullable(pic, port, c, p);

  if (pic_invalid_p(pic, val)) {
    c = next(pic, port);
    goto retry;
  }

  return val;
}

static void
reader_table_init(void)
{
  int c;

  for (c = 0; c < 256; ++c) {
    reader_table[c] = NULL;
  }
  for (c = 0; c < 256; ++c) {
    reader_dispatch[c] = NULL;
  }

  /* default reader */
  for (c = 1; c < 256; ++c) {
    reader_table[c] = read_symbol;
  }

  reader_table[')'] = read_unmatch;
  reader_table[';'] = read_comment;
  reader_table['\''] = read_quote;
  reader_table['`'] = read_quasiquote;
  reader_table[','] = read_unquote;
  reader_table['"'] = read_string;
  reader_table['|'] = read_pipe;
  reader_table['('] = read_pair;
  reader_table['#'] = read_dispatch;
  reader_table['+'] = read_number;
  reader_table['-'] = read_number;
  for (c = '0'; c <= '9'; ++c) {
    reader_table[c] = read_number;
  }

  reader_dispatch['!'] = read_directive;
  reader_dispatch['|'] = read_block_comment;
  reader_dispatch[';'] = read_datum_comment;
  reader_dispatch['t'] = read_true;
  reader_dispatch['f'] = read_false;
  reader_dispatch['\''] = read_syntax_quote;
  reader_dispatch['`'] = read_syntax_quasiquote;
  reader_dispatch[','] = read_syntax_unquote;
  reader_dispatch['\\'] = read_char;
  reader_dispatch['('] = read_vector;
  reader_dispatch['u'] = read_undef_or_blob;

  /* read labels */
  for (c = '0'; c <= '9'; ++c) {
    reader_dispatch[c] = read_label;
  }
}

static void
reader_init(pic_state *PIC_UNUSED(pic), struct reader_control *p)
{
  p->typecase = CASE_DEFAULT;
  kh_init(read, &p->labels);
}

static void
reader_destroy(pic_state *pic, struct reader_control *p)
{
  kh_destroy(read, &p->labels);
}

pic_value
pic_read(pic_state *pic, pic_value port)
{
  struct reader_control p;
  size_t ai = pic_enter(pic);
  pic_value val;
  int c;
  pic_value e;

  reader_init(pic, &p);

  pic_try {
    while ((c = skip(pic, port, next(pic, port))) != EOF) {
      val = read_nullable(pic, port, c, &p);

      if (! pic_invalid_p(pic, val)) {
        break;
      }
      pic_leave(pic, ai);
    }
    if (c == EOF) {
      val = pic_eof_object(pic);
    }
  }
  pic_catch(e) {
    reader_destroy(pic, &p);
    pic_raise(pic, e);
  }

  pic_leave(pic, ai);
  return pic_protect(pic, val);
}

pic_value
pic_read_cstr(pic_state *pic, const char *str)
{
  pic_value port = pic_fmemopen(pic, str, strlen(str), "r");
  pic_value form, e;

  pic_try {
    form = pic_read(pic, port);
  }
  pic_catch(e) {
    pic_fclose(pic, port);
    pic_raise(pic, e);
  }

  pic_fclose(pic, port);

  return form;
}

static pic_value
pic_read_read(pic_state *pic)
{
  pic_value port = pic_stdin(pic);

  pic_get_args(pic, "|p", &port);

  return pic_read(pic, port);
}

void
pic_init_read(pic_state *pic)
{
  reader_table_init();

  pic_defun(pic, "read", pic_read_read);
}