#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct Node Node;
typedef struct Exploration Exploration;


enum opcode {
    STRING,
    AND,
    STAR,
    PLUS
};
struct Exploration
{
    int position;
    char *text;
};

Exploration *mkExploration(char *text)
{
    Exploration *exploration = calloc(1,sizeof(Exploration*)); //sizeof du type pointeur
    exploration->position= 0;
    exploration->text= text;
    return exploration;
}

char advance(Exploration *exploration)
{
    return exploration->text[exploration->position++];
}

int endExploration(Exploration *exploration)
{
    if (exploration->position >= strlen(exploration->text))
    {
        return 1;
    } else
    {
        return -1;
    }
}

void setPosition(Exploration *exploration, int position)
{
    exploration->position= position;
}


struct Node
{
    enum opcode type;
    union {
	char *stringValue;
	Node *children[2];
    };
};



Node *mkNode(enum opcode type)
{
    Node *node= calloc(1, sizeof(Node));
    node->type= type;
    return node;
}

Node *mkString(char *value)
{
    Node *node= mkNode(STRING);
    node->stringValue= value;
    return node;
}

Node *mkAnd(Node *node1, Node *node2)
{
    Node *node= mkNode(AND);
    node->children[0]= node1;
    node->children[1]= node2;
    return node;
}


Node *mkStar(Node *child)
{
    Node *node= mkNode(STAR);
    node->children[0]= child;
    return node;
}

Node *mkPlus(Node *child)
{
    Node *node= mkNode(PLUS);
    node->children[0]= child;
    return node;
}


int execute(Node *node, Exploration *in)
{
    switch (node->type) {
      case STRING: {
      int pos= in->position;
      for (int i=0; i < strlen(node->stringValue);i++)
      {
          if (advance(in) != node->stringValue[i])
          {
              setPosition(in, pos);
              return 0;
          }
      }
      return endExploration(in);
      }
      case AND: {
      int pos= in->position;
      if (execute(node->children[0], in) == 0) //si il y a eu une erreur
      {
          setPosition(in, pos);
          return 0;
      } else //si ça s'est bien passé
      {
          int result=  execute(node->children[1], in);
          if (result == 0) {
            setPosition(in, pos);
          }
          return result;
      }
      }
      case STAR: {
      int pos= in->position;
      int result;
      while ((result= execute(node->children[0], in)) == -1){
          pos= in->position;;
      }
      if (result == 0) {
          setPosition(in, pos);
      }
      return endExploration(in);
      }
      case PLUS: {
      Node *newNode= mkAnd(node->children[0], mkStar(node->children[0]));
      return execute(newNode,in);
      }
    }
    printf("this cannot happen\n");
    abort();
}


int main(int argc, char **argv)
{
    Exploration *in= mkExploration("aabbcc");

    /*Node *program=
	mkString("aabbcc");
    Node *program=
	mkAnd(mkString("aab"),
	      mkString("bcc"));*/

    /*Node *program=
	mkAnd(mkString("aa"),
	      mkAnd(mkString("bb"),
		    mkString("cc")));*/

    Node *program=
            mkAnd(mkPlus(mkString("a")),       // "a"*"b"*"c"*
                mkAnd(mkStar(mkString("b")),
                mkStar(mkString("c"))));


    if (execute(program, in)<=0)
    {
        printf("no match\n");
    } else
    {
        printf("match\n");
    }// 0 => no match, 1 => match




    /*Input *in1= mkInput("hello");
    Input *in2= mkInput("world");
    Input *in3= mkInput("hello world");
    Node *program=
	      mkOr(mkString("hello"),       // "hello" | "world"
		   mkString("world"));
    printf("%i\n", execute(program, in));  // 0 => no match, 1 => match*/



    return 0;
}