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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2019 Olaf Wintermann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

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

#include "xml.h"

typedef struct StackElm {
    WSXmlNode *node; // list of nodes
    //WSXmlNode *parent; // if not NULL, call endcb after node->next is NULL
    int endonly;
    struct StackElm *next;
} StackElm;

#define STACK_PUSH(stack, elm) if(stack) { elm->next = stack; } stack = elm;

int wsxml_iterator(
        pool_handle_t *pool,
        WSXmlNode *node,
        wsxml_func begincb,
        wsxml_func endcb,
        void *udata)
{  
    if(!node) {
        return 0;
    }
    
    StackElm *stack = pool_malloc(pool, sizeof(StackElm));
    if(!stack) {
        return 1; // OOM
    }
    stack->next = NULL;
    stack->node = node;
    stack->endonly = 0;
    //stack->parent = NULL;
    
    int ret = 0;
    int br = 0;
    while(stack) {
        StackElm *cur = stack;
        WSXmlNode *xmlnode = cur->node; // get top stack element
        stack = cur->next;              // and remove it
        cur->next = NULL;
        
        while(xmlnode && !cur->endonly) {
            // element begin callback
            if(begincb(xmlnode, udata)) {
                br = 1;
                break; // I don't like break with labels - is this wrong?
            }
            
            if(xmlnode->children) {
                // put the children on the stack
                // the next stack iteration will process the children
                StackElm *newelm = pool_malloc(pool, sizeof(StackElm));
                if(!newelm) {
                    ret = 1;
                    br = 1;
                    break;
                }
                newelm->next = NULL;
                newelm->node = xmlnode->children;
                // setting the parent will make sure endcb will be called
                // for the current xmlnode after all children are processed
                //newelm->parent = xmlnode;
                newelm->endonly = 0;
                
                // if xmlnode->next is not NULL, there are still nodes at
                // this level, therefore we have to put these also on the
                // stack
                // this way, the remaining nodes are processed after all
                // children and the end tag are processed
                if(xmlnode->next) {
                    StackElm *nextelm = pool_malloc(pool, sizeof(StackElm));
                    if(!nextelm) {
                        ret = 1;
                        br = 1;
                        break;
                    }
                    nextelm->node = xmlnode->next;
                    nextelm->next = NULL;
                    nextelm->endonly = 0;
                    STACK_PUSH(stack, nextelm);
                }
                
                // we have to put the end tag of the current element
                // on the stack to ensure endcb is called for the current
                // element, after all children are processed
                // reuse cur
                cur->node = xmlnode;
                cur->endonly = 1;
                STACK_PUSH(stack, cur);
                
                cur = NULL;
                
                // now we can put the children on the stack
                STACK_PUSH(stack, newelm);
                // break, because we don't want to process xmlnode->next now
                break;
            } else {
                // no children means, the end callback can be called directly
                // after the begin callback (no intermediate nodes)
                cur->node = NULL;
                if(endcb(xmlnode, udata)) {
                    br = 1;
                    break;
                }
            }
            
            // continue with next node at this level
            xmlnode = xmlnode->next;
        }
        if(br) {
            break; // break because of an error
        }
        
        if(cur && cur->node) {
            //xmlNode *endNode = cur->parent ? cur->parent : cur->node;
            xmlNode *endNode = cur->node;
            if(endcb(endNode, udata)) {
                break;
            }
            pool_free(pool, cur);
        }
    }
    
    // free all remaining elements
    StackElm *elm = stack;
    while(elm) {
        StackElm *next = elm->next;
        pool_free(pool, elm);
        elm = next;
    }

    return ret;
}