/*      $OpenBSD: tsearch.c,v 1.10 2015/09/26 16:03:48 guenther Exp $   */

/*
 * Tree search generalized from Knuth (6.2.2) Algorithm T just like
 * the AT&T man page says.
 *
 * The node_t structure is for internal use only
 *
 * Written by reading the System V Interface Definition, not the code.
 *
 * Totally public domain.
 */

#include <search.h>
#include <stdlib.h>

typedef struct node_t {
    char          *key;
    struct node_t *left, *right;
} node;

/* find or insert datum into search tree */
void *
tsearch(const void *vkey, void **vrootp,
    int (*compar)(const void *, const void *))
{
    node *q;
    char *key = (char *)vkey;
    node **rootp = (node **)vrootp;

    if (rootp == (struct node_t **)0)
        return ((void *)0);
    while (*rootp != (struct node_t *)0) {      /* Knuth's T1: */
        int r;

        if ((r = (*compar)(key, (*rootp)->key)) == 0)   /* T2: */
            return ((void *)*rootp);            /* we found it! */
        rootp = (r < 0) ?
            &(*rootp)->left :           /* T3: follow left branch */
            &(*rootp)->right;           /* T4: follow right branch */
    }
    q = malloc(sizeof(node));   /* T5: key not found */
    if (q != (struct node_t *)0) {      /* make new node */
        *rootp = q;                     /* link new node to old */
        q->key = key;                   /* initialize new node */
        q->left = q->right = (struct node_t *)0;
    }
    return ((void *)q);
}

/* delete node with given key */
void *
tdelete(const void *vkey, void **vrootp,
    int (*compar)(const void *, const void *))
{
    node **rootp = (node **)vrootp;
    char *key = (char *)vkey;
    node *p = (node *)1;
    node *q;
    node *r;
    int cmp;

    if (rootp == (struct node_t **)0 || *rootp == (struct node_t *)0)
        return ((struct node_t *)0);
    while ((cmp = (*compar)(key, (*rootp)->key)) != 0) {
        p = *rootp;
        rootp = (cmp < 0) ?
            &(*rootp)->left :           /* follow left branch */
            &(*rootp)->right;           /* follow right branch */
        if (*rootp == (struct node_t *)0)
            return ((void *)0);         /* key not found */
    }
    r = (*rootp)->right;                        /* D1: */
    if ((q = (*rootp)->left) == (struct node_t *)0)     /* Left (struct node_t *)0? */
        q = r;
    else if (r != (struct node_t *)0) {         /* Right link is null? */
        if (r->left == (struct node_t *)0) {    /* D2: Find successor */
            r->left = q;
            q = r;
        } else {                        /* D3: Find (struct node_t *)0 link */
            for (q = r->left; q->left != (struct node_t *)0; q = r->left)
                r = q;
            r->left = q->right;
            q->left = (*rootp)->left;
            q->right = (*rootp)->right;
        }
    }
    free((struct node_t *) *rootp);     /* D4: Free node */
    *rootp = q;                         /* link parent to new node */
    return(p);
}

/* Walk the nodes of a tree */
static void
trecurse(node *root, void (*action)(const void *, VISIT, int), int level)
{
    if (root->left == (struct node_t *)0 && root->right == (struct node_t *)0)
        (*action)(root, leaf, level);
    else {
        (*action)(root, preorder, level);
        if (root->left != (struct node_t *)0)
            trecurse(root->left, action, level + 1);
        (*action)(root, postorder, level);
        if (root->right != (struct node_t *)0)
            trecurse(root->right, action, level + 1);
        (*action)(root, endorder, level);
    }
}

/* Walk the nodes of a tree */
void
twalk(const void *vroot, void (*action)(const void *, VISIT, int))
{
    node *root = (node *)vroot;

    if (root != (node *)0 && action != (void (*)(const void *, VISIT, int))0)
        trecurse(root, action, 0);
}