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

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

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

char *ptr;
NodePtr regexHeadNode;

NodePtr charClass();
NodePtr string();
NodePtr group();
NodePtr _or();
NodePtr asterisk();
NodePtr regex();
NodePtr createNode(char,NodePtr,NodePtr);

NodePtr createNode(char character, NodePtr left, NodePtr right) {
    NodePtr n = (NodePtr)malloc(sizeof(Node));
    n->self = n;
    n->character = character;
    n->left = left;
    n->right = right;

    return n;
}

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

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

// <string> ::= <literal><literal>*
NodePtr string() {
    char c = *ptr;
    NodePtr n = NULL;
    printf("%c\n",c);
    if (('a'<=c && c<='z')||('A'<=c && c<='Z')||('0'<=c && c<='9')) {
        n = createNode(0,literal(),string());
    } else {
        n = createNode(0,0,0);
    }
    return n;
}

// <group> ::= '('<regex>')' | '('<regex>'|'<regex>')'
NodePtr group() {
    NodePtr n;
    if (*ptr == ')') {
        n = createNode(0,0,0);
        ptr++;
    } else {
        ptr++;
        n = regex();
    }

    return n;
}


// <or> ::= <regex>'|'<regex>
NodePtr _or() {
    NodePtr n = createNode('|',regexHeadNode,regex());
    return n;
}

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

}

// <regex> ::= <string>|<or>|<charClass>|<group>|<*>
NodePtr regex() {

    NodePtr n;

    while (*ptr != '\0') {
        if ((*ptr == '(') || (*ptr == ')')) {
            n = group();
        } else if (*ptr == '[') {
            n = charClass();
        } else if (*ptr == '|'){
            n = _or();
        } else {
            n = string();
            regexHeadNode = n;
        }
    }

    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;
}