/*
 * <literal> ::= [a-z][A-Z][0-9]
 * <charClass> ::= '['<literal>'-'<literal>']'
 * <string> ::= <literal><literal>*
 * <or> ::= '('<regex>'|'<regex>')'
 * <*> ::= <regex>'*'
 * <regex> ::= <literal>|<conc>|<or>|<charClass>
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *ptr;

typedef struct node {
    int character;
    struct node *left;
    struct node *right;
} Node, *NodePtr;

NodePtr charClass();
NodePtr string();
NodePtr _or();
NodePtr asterisk();
NodePtr regex();
NodePtr createNode(int,NodePtr,NodePtr);

NodePtr createNode(int character, NodePtr left, NodePtr right) {
    NodePtr n;
    n = (NodePtr)malloc(sizeof(Node));
    n->character = character;
    n->left = left;
    n->right = right;
    return n;
}

// <charClass> ::= '['<literal>'-'<literal>']'
NodePtr charClass() {
    NodePtr n = createNode(0,0,0);
    return n;
}

// <literal> ::= [a-z][A-Z][0-9]
NodePtr literal() {
    char c = *ptr;
    createNode(c,0,0);
}

// <string> ::= <literal><literal>*
NodePtr string() {
    char c = *ptr;
    NodePtr n = (NodePtr)malloc(sizeof(Node));

    if (('a'<=c && c<='z')||('A'<=c && c<='Z')||('0'<=c && c<='9')) {
        n = createNode(0,literal(),string());
        return n;
    } else {
        n = createNode(0,0,0);
    }
}

// <or> ::= '('<regex>'|'<regex>')'
NodePtr _or() {
    regex();
    while(*ptr++ == ')') {
        if (*ptr == '|') {
            ptr++;
            regex();
        }
    }
}

// <*> ::= <regex>'*'
NodePtr asterisk() {

}

// <regex> ::= <literal>|<string>|<or>|<charClass>
// <literal> は <string> に内包されるから、<regex> ::= <string>|<or>|<charClass>が正しい??
NodePtr regex() {

    NodePtr n;

    while (int c = *ptr++) {
        if (c == '(') {
            ptr++;
            _or();
        } else if (c == '[') {
            charClass();
        } else {
            n = createNode(0,string(),regex());
        }
    }

    return n;
}

int
main(int argc, char **argv)
{
    for (int i = 1; i < argc; i++) {
        if (strcmp(argv[i],"-regex") == 0) {
            ptr = argv[i+1]; i++;
        }
    }

    printf("regex : %s\n",ptr);
    NodePtr n = regex();

    return 0;
}