#include <assert.h>
#include "parser_internal.h"

typedef struct {
  const HParser *p;
  HAction action;
  void* user_data;
} HParseAction;

static HParseResult* parse_action(void *env, HParseState *state) {
  HParseAction *a = (HParseAction*)env;
  if (a->p && a->action) {
    HParseResult *tmp = h_do_parse(a->p, state);
    //HParsedToken *tok = a->action(h_do_parse(a->p, state));
    if(tmp) {
      const HParsedToken *tok = a->action(tmp, a->user_data);
      return make_result(state->arena, (HParsedToken*)tok);
    } else
      return NULL;
  } else // either the parser's missing or the action's missing
    return NULL;
}

static void desugar_action(HAllocator *mm__, HCFStack *stk__, void *env) {
  HParseAction *a = (HParseAction*)env;

  HCFS_BEGIN_CHOICE() {
    HCFS_BEGIN_SEQ() {
      HCFS_DESUGAR(a->p);
    } HCFS_END_SEQ();
    HCFS_THIS_CHOICE->user_data = a->user_data;
    HCFS_THIS_CHOICE->action = a->action;
    HCFS_THIS_CHOICE->reshape = h_act_first;
  } HCFS_END_CHOICE();
}

static bool action_isValidRegular(void *env) {
  HParseAction *a = (HParseAction*)env;
  return a->p->vtable->isValidRegular(a->p->env);
}

static bool action_isValidCF(void *env) {
  HParseAction *a = (HParseAction*)env;
  return a->p->vtable->isValidCF(a->p->env);
}

static bool h_svm_action_action(HArena *arena, HSVMContext *ctx, void* arg) {
  HParseResult res;
  HParseAction *a = arg;
  assert(ctx->stack_count >= 1);
  if (ctx->stack[ctx->stack_count-1]->token_type != TT_MARK) {
    assert(ctx->stack_count >= 2 && ctx->stack[ctx->stack_count-2]->token_type == TT_MARK);
    res.ast = ctx->stack[ctx->stack_count-2] = ctx->stack[ctx->stack_count-1];
    ctx->stack_count--;
    // mark replaced.
  } else {
    res.ast = NULL;
  }
  res.arena = arena;

  HParsedToken *tok = a->action(&res, a->user_data);
  if (tok != NULL)
    ctx->stack[ctx->stack_count-1] = tok;
  else
    ctx->stack_count--;
  return true; // action can't fail
}

static bool action_ctrvm(HRVMProg *prog, void* env) {
  HParseAction *a = (HParseAction*)env;
  h_rvm_insert_insn(prog, RVM_PUSH, 0);
  if (!h_compile_regex(prog, a->p))
    return false;
  h_rvm_insert_insn(prog, RVM_ACTION, h_rvm_create_action(prog, h_svm_action_action, a));
  return true;
}

static const HParserVtable action_vt = {
  .parse = parse_action,
  .isValidRegular = action_isValidRegular,
  .isValidCF = action_isValidCF,
  .desugar = desugar_action,
  .compile_to_rvm = action_ctrvm,
};

HParser* h_action(const HParser* p, const HAction a, void* user_data) {
  return h_action__m(&system_allocator, p, a, user_data);
}

HParser* h_action__m(HAllocator* mm__, const HParser* p, const HAction a, void* user_data) {
  HParseAction *env = h_new(HParseAction, 1);
  env->p = p;
  env->action = a;
  env->user_data = user_data;
  return h_new_parser(mm__, &action_vt, env);
}
